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This commit follows on from the earlier commit "libctf, ld, binutils:
add textual error/warning reporting for libctf" and converts every error
in libctf that was reported using ctf_dprintf to use ctf_err_warn
instead, gettextizing them in the process, using N_() where necessary to
avoid doing gettext calls unless an error message is actually generated,
and rephrasing some error messages for ease of translation.
This requires a slight change in the ctf_errwarning_next API: this API
is public but has not been in a release yet, so can still change freely.
The problem is that many errors are emitted at open time (whether
opening of a CTF dict, or opening of a CTF archive): the former of these
throws away its incompletely-initialized ctf_file_t rather than return
it, and the latter has no ctf_file_t at all. So errors and warnings
emitted at open time cannot be stored in the ctf_file_t, and have to go
elsewhere.
We put them in a static local in ctf-subr.c (which is not very
thread-safe: a later commit will improve things here): ctf_err_warn with
a NULL fp adds to this list, and the public interface
ctf_errwarning_next with a NULL fp retrieves from it.
We need a slight exception from the usual iterator rules in this case:
with a NULL fp, there is nowhere to store the ECTF_NEXT_END "error"
which signifies the end of iteration, so we add a new err parameter to
ctf_errwarning_next which is used to report such iteration-related
errors. (If an fp is provided -- i.e., if not reporting open errors --
this is optional, but even if it's optional it's still an API change.
This is actually useful from a usability POV as well, since
ctf_errwarning_next is usually called when there's been an error, so
overwriting the error code with ECTF_NEXT_END is not very helpful!
So, unusually, ctf_errwarning_next now uses the passed fp for its
error code *only* if no errp pointer is passed in, and leaves it
untouched otherwise.)
ld, objdump and readelf are adapted to call ctf_errwarning_next with a
NULL fp to report open errors where appropriate.
The ctf_err_warn API also has to change, gaining a new error-number
parameter which is used to add the error message corresponding to that
error number into the debug stream when LIBCTF_DEBUG is enabled:
changing this API is easy at this point since we are already touching
all existing calls to gettextize them. We need this because the debug
stream should contain the errno's message, but the error reported in the
error/warning stream should *not*, because the caller will probably
report it themselves at failure time regardless, and reporting it in
every error message that leads up to it leads to a ridiculous chattering
on failure, which is likely to end up as ridiculous chattering on stderr
(trimmed a bit):
CTF error: `ld/testsuite/ld-ctf/A.c (0): lookup failure for type 3: flags 1: The parent CTF dictionary is unavailable'
CTF error: `ld/testsuite/ld-ctf/A.c (0): struct/union member type hashing error during type hashing for type 80000001, kind 6: The parent CTF dictionary is unavailable'
CTF error: `deduplicating link variable emission failed for ld/testsuite/ld-ctf/A.c: The parent CTF dictionary is unavailable'
ld/.libs/lt-ld-new: warning: CTF linking failed; output will have no CTF section: `The parent CTF dictionary is unavailable'
We only need to be told that the parent CTF dictionary is unavailable
*once*, not over and over again!
errmsgs are still emitted on warning generation, because warnings do not
usually lead to a failure propagated up to the caller and reported
there.
Debug-stream messages are not translated. If translation is turned on,
there will be a mixture of English and translated messages in the debug
stream, but rather that than burden the translators with debug-only
output.
binutils/ChangeLog
2020-08-27 Nick Alcock <nick.alcock@oracle.com>
* objdump.c (dump_ctf_archive_member): Move error-
reporting...
(dump_ctf_errs): ... into this separate function.
(dump_ctf): Call it on open errors.
* readelf.c (dump_ctf_archive_member): Move error-
reporting...
(dump_ctf_errs): ... into this separate function. Support
calls with NULL fp. Adjust for new err parameter to
ctf_errwarning_next.
(dump_section_as_ctf): Call it on open errors.
include/ChangeLog
2020-08-27 Nick Alcock <nick.alcock@oracle.com>
* ctf-api.h (ctf_errwarning_next): New err parameter.
ld/ChangeLog
2020-08-27 Nick Alcock <nick.alcock@oracle.com>
* ldlang.c (lang_ctf_errs_warnings): Support calls with NULL fp.
Adjust for new err parameter to ctf_errwarning_next. Only
check for assertion failures when fp is non-NULL.
(ldlang_open_ctf): Call it on open errors.
* testsuite/ld-ctf/ctf.exp: Always use the C locale to avoid
breaking the diags tests.
libctf/ChangeLog
2020-08-27 Nick Alcock <nick.alcock@oracle.com>
* ctf-subr.c (open_errors): New list.
(ctf_err_warn): Calls with NULL fp append to open_errors. Add err
parameter, and use it to decorate the debug stream with errmsgs.
(ctf_err_warn_to_open): Splice errors from a CTF dict into the
open_errors.
(ctf_errwarning_next): Calls with NULL fp report from open_errors.
New err param to report iteration errors (including end-of-iteration)
when fp is NULL.
(ctf_assert_fail_internal): Adjust ctf_err_warn call for new err
parameter: gettextize.
* ctf-impl.h (ctfo_get_vbytes): Add ctf_file_t parameter.
(LCTF_VBYTES): Adjust.
(ctf_err_warn_to_open): New.
(ctf_err_warn): Adjust.
(ctf_bundle): Used in only one place: move...
* ctf-create.c: ... here.
(enumcmp): Use ctf_err_warn, not ctf_dprintf, passing the err number
down as needed. Don't emit the errmsg. Gettextize.
(membcmp): Likewise.
(ctf_add_type_internal): Likewise.
(ctf_write_mem): Likewise.
(ctf_compress_write): Likewise. Report errors writing the header or
body.
(ctf_write): Likewise.
* ctf-archive.c (ctf_arc_write_fd): Use ctf_err_warn, not
ctf_dprintf, and gettextize, as above.
(ctf_arc_write): Likewise.
(ctf_arc_bufopen): Likewise.
(ctf_arc_open_internal): Likewise.
* ctf-labels.c (ctf_label_iter): Likewise.
* ctf-open-bfd.c (ctf_bfdclose): Likewise.
(ctf_bfdopen): Likewise.
(ctf_bfdopen_ctfsect): Likewise.
(ctf_fdopen): Likewise.
* ctf-string.c (ctf_str_write_strtab): Likewise.
* ctf-types.c (ctf_type_resolve): Likewise.
* ctf-open.c (get_vbytes_common): Likewise. Pass down the ctf dict.
(get_vbytes_v1): Pass down the ctf dict.
(get_vbytes_v2): Likewise.
(flip_ctf): Likewise.
(flip_types): Likewise. Use ctf_err_warn, not ctf_dprintf, and
gettextize, as above.
(upgrade_types_v1): Adjust calls.
(init_types): Use ctf_err_warn, not ctf_dprintf, as above.
(ctf_bufopen_internal): Likewise. Adjust calls. Transplant errors
emitted into individual dicts into the open errors if this turns
out to be a failed open in the end.
* ctf-dump.c (ctf_dump_format_type): Adjust ctf_err_warn for new err
argument. Gettextize. Don't emit the errmsg.
(ctf_dump_funcs): Likewise. Collapse err label into its only case.
(ctf_dump_type): Likewise.
* ctf-link.c (ctf_create_per_cu): Adjust ctf_err_warn for new err
argument. Gettextize. Don't emit the errmsg.
(ctf_link_one_type): Likewise.
(ctf_link_lazy_open): Likewise.
(ctf_link_one_input_archive): Likewise.
(ctf_link_deduplicating_count_inputs): Likewise.
(ctf_link_deduplicating_open_inputs): Likewise.
(ctf_link_deduplicating_close_inputs): Likewise.
(ctf_link_deduplicating): Likewise.
(ctf_link): Likewise.
(ctf_link_deduplicating_per_cu): Likewise. Add some missed
ctf_set_errnos to obscure error cases.
* ctf-dedup.c (ctf_dedup_rhash_type): Adjust ctf_err_warn for new
err argument. Gettextize. Don't emit the errmsg.
(ctf_dedup_populate_mappings): Likewise.
(ctf_dedup_detect_name_ambiguity): Likewise.
(ctf_dedup_init): Likewise.
(ctf_dedup_multiple_input_dicts): Likewise.
(ctf_dedup_conflictify_unshared): Likewise.
(ctf_dedup): Likewise.
(ctf_dedup_rwalk_one_output_mapping): Likewise.
(ctf_dedup_id_to_target): Likewise.
(ctf_dedup_emit_type): Likewise.
(ctf_dedup_emit_struct_members): Likewise.
(ctf_dedup_populate_type_mapping): Likewise.
(ctf_dedup_populate_type_mappings): Likewise.
(ctf_dedup_emit): Likewise.
(ctf_dedup_hash_type): Likewise. Fix a bit of messed-up error
status setting.
(ctf_dedup_rwalk_one_output_mapping): Likewise. Don't hide
unknown-type-kind messages (which signify file corruption).
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This adds the core deduplicator that the ctf_link machinery calls
(possibly repeatedly) to link the CTF sections: it takes an array
of input ctf_file_t's and another array that indicates which entries in
the input array are parents of which other entries, and returns an array
of outputs. The first output is always the ctf_file_t on which
ctf_link/ctf_dedup/etc was called: the other outputs are child dicts
that have the first output as their parent.
include/
* ctf-api.h (CTF_LINK_SHARE_DUPLICATED): No longer unimplemented.
libctf/
* ctf-impl.h (ctf_type_id_key): New, the key in the
cd_id_to_file_t.
(ctf_dedup): New, core deduplicator state.
(ctf_file_t) <ctf_dedup>: New.
<ctf_dedup_atoms>: New.
<ctf_dedup_atoms_alloc>: New.
(ctf_hash_type_id_key): New prototype.
(ctf_hash_eq_type_id_key): Likewise.
(ctf_dedup_atoms_init): Likewise.
* ctf-hash.c (ctf_hash_eq_type_id_key): New.
(ctf_dedup_atoms_init): Likewise.
* ctf-create.c (ctf_serialize): Adjusted.
(ctf_add_encoded): No longer static.
(ctf_add_reftype): Likewise.
* ctf-open.c (ctf_file_close): Destroy the
ctf_dedup_atoms_alloc.
* ctf-dedup.c: New file.
* ctf-decls.h [!HAVE_DECL_STPCPY]: Add prototype.
* configure.ac: Check for stpcpy.
* Makefile.am: Add it.
* Makefile.in: Regenerate.
* config.h.in: Regenerate.
* configure: Regenerate.
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Now a bunch of stuff that doesn't apply to ld or any normal use of
libctf, piled into one commit so that it's easier to ignore.
The cu-mapping machinery associates incoming compilation unit names with
outgoing names of CTF dictionaries that should correspond to them, for
non-gdb CTF consumers that would like to group multiple TUs into a
single child dict if conflicting types are found in it (the existing use
case is one kernel module, one child CTF dict, even if the kernel module
is composed of multiple CUs).
The upcoming deduplicator needs to track not only the mapping from
incoming CU name to outgoing dict name, but the inverse mapping from
outgoing dict name to incoming CU name, so it can work over every CTF
dict we might see in the output and link into it.
So rejig the ctf-link machinery to do that. Simultaneously (because
they are closely associated and were written at the same time), we add a
new CTF_LINK_EMPTY_CU_MAPPINGS flag to ctf_link, which tells the
ctf_link machinery to create empty child dicts for each outgoing CU
mapping even if no CUs that correspond to it exist in the link. This is
a bit (OK, quite a lot) of a waste of space, but some existing consumers
require it. (Nobody else should use it.)
Its value is not consecutive with existing CTF_LINK flag values because
we're about to add more flags that are conceptually closer to the
existing ones than this one is.
include/
* ctf-api.h (CTF_LINK_EMPTY_CU_MAPPINGS): New.
libctf/
* ctf-impl.h (ctf_file_t): Improve comments.
<ctf_link_cu_mapping>: Split into...
<ctf_link_in_cu_mapping>: ... this...
<ctf_link_out_cu_mapping>: ... and this.
* ctf-create.c (ctf_serialize): Adjust.
* ctf-open.c (ctf_file_close): Likewise.
* ctf-link.c (ctf_create_per_cu): Look things up in the
in_cu_mapping instead of the cu_mapping.
(ctf_link_add_cu_mapping): The deduplicating link will define
what happens if many FROMs share a TO.
(ctf_link_add_cu_mapping): Create in_cu_mapping and
out_cu_mapping. Do not create ctf_link_outputs here any more, or
create per-CU dicts here: they are already created when needed.
(ctf_link_one_variable): Log a debug message if we skip a
variable due to its type being concealed in a CU-mapped link.
(This is probably too common a case to make into a warning.)
(ctf_link): Create empty per-CU dicts if requested.
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When you link TUs that contain conflicting types together, the resulting
CTF section is an archive containing many CTF dicts. These dicts appear
in ctf_link_outputs of the shared dict, with each ctf_import'ing that
shared dict. ctf_importing a dict bumps its refcount to stop it going
away while it's in use -- but if the shared dict (whose refcount is
bumped) has the child dict (doing the bumping) in its ctf_link_outputs,
we have a refcount loop, since the child dict only un-ctf_imports and
drops the parent's refcount when it is freed, but the child is only
freed when the parent's refcount falls to zero.
(In the future, this will be able to go wrong on the inputs too, when an
ld -r'ed deduplicated output with conflicts is relinked. Right now this
cannot happen because we don't ctf_import such dicts at all. This will
be fixed in a later commit in this series.)
Fix this by introducing an internal-use-only ctf_import_unref function
that imports a parent dict *witthout* bumping the parent's refcount, and
using it when we create per-CU outputs. This function is only safe to
use if you know the parent cannot go away while the child exists: but if
the parent *owns* the child, as here, this is necessarily true.
Record in the ctf_file_t whether a parent was imported via ctf_import or
ctf_import_unref, so that if you do another ctf_import later on (or a
ctf_import_unref) it can decide whether to drop the refcount of the
existing parent being replaced depending on which function you used to
import that one. Adjust ctf_serialize so that rather than doing a
ctf_import (which is wrong if the original import was
ctf_import_unref'fed), we just copy the parent field and refcount over
and forcibly flip the unref flag on on the old copy we are going to
discard.
ctf_file_close also needs a bit of tweaking to only close the parent if
it was not imported with ctf_import_unref: while we're at it, guard
against repeated closes with a refcount of zero and stop them causing
double-frees, even if destruction of things freed *inside*
ctf_file_close cause such recursion.
Verified no leaks or accesses to freed memory after all of this with
valgrind. (It was leak-happy before.)
libctf/
* ctf-impl.c (ctf_file_t) <ctf_parent_unreffed>: New.
(ctf_import_unref): New.
* ctf-open.c (ctf_file_close) Drop the refcount all the way to
zero. Don't recurse back in if the refcount is already zero.
(ctf_import): Check ctf_parent_unreffed before deciding whether
to close a pre-existing parent. Set it to zero.
(ctf_import_unreffed): New, as above, setting
ctf_parent_unreffed to 1.
* ctf-create.c (ctf_serialize): Do not ctf_import into the new
child: use direct assignment, and set unreffed on the new and
old children.
* ctf-link.c (ctf_create_per_cu): Import the parent using
ctf_import_unreffed.
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This commit adds a long-missing piece of infrastructure to libctf: the
ability to report errors and warnings using all the power of printf,
rather than being restricted to one errno value. Internally, libctf
calls ctf_err_warn() to add errors and warnings to a list: a new
iterator ctf_errwarning_next() then consumes this list one by one and
hands it to the caller, which can free it. New errors and warnings are
added until the list is consumed by the caller or the ctf_file_t is
closed, so you can dump them at intervals. The caller can of course
choose to print only those warnings it wants. (I am not sure whether we
want objdump, readelf or ld to print warnings or not: right now I'm
printing them, but maybe we only want to print errors? This entirely
depends on whether warnings are voluminous things describing e.g. the
inability to emit single types because of name clashes or something.
There are no users of this infrastructure yet, so it's hard to say.)
There is no internationalization here yet, but this at least adds a
place where internationalization can be added, to one of
ctf_errwarning_next or ctf_err_warn.
We also provide a new ctf_assert() function which uses this
infrastructure to provide non-fatal assertion failures while emitting an
assert-like string to the caller: to save space and avoid needlessly
duplicating unchanging strings, the assertion test is inlined but the
print-things-out failure case is not. All assertions in libctf will be
converted to use this machinery in future commits and propagate
assertion-failure errors up, so that the linker in particular cannot be
killed by libctf assertion failures when it could perfectly well just
print warnings and drop the CTF section.
include/
* ctf-api.h (ECTF_INTERNAL): Adjust error text.
(ctf_errwarning_next): New.
libctf/
* ctf-impl.h (ctf_assert): New.
(ctf_err_warning_t): Likewise.
(ctf_file_t) <ctf_errs_warnings>: Likewise.
(ctf_err_warn): New prototype.
(ctf_assert_fail_internal): Likewise.
* ctf-inlines.h (ctf_assert_internal): Likewise.
* ctf-open.c (ctf_file_close): Free ctf_errs_warnings.
* ctf-create.c (ctf_serialize): Copy it on serialization.
* ctf-subr.c (ctf_err_warn): New, add an error/warning.
(ctf_errwarning_next): New iterator, free and pass back
errors/warnings in succession.
* libctf.ver (ctf_errwarning_next): Add.
ld/
* ldlang.c (lang_ctf_errs_warnings): New, print CTF errors
and warnings. Assert when libctf asserts.
(lang_merge_ctf): Call it.
(land_write_ctf): Likewise.
binutils/
* objdump.c (ctf_archive_member): Print CTF errors and warnings.
* readelf.c (dump_ctf_archive_member): Likewise.
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If corrupt CTF with invalid header flags is passed in, return the new
error ECTF_FLAGS.
include/
* ctf-api.h (ECTF_FLAGS): New.
(ECTF_NERR): Adjust.
* ctf.h (CTF_F_MAX): New.
libctf/
* ctf-open.c (ctf_bufopen_internal): Diagnose invalid flags.
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This allows you to bump the refcount on a ctf_file_t, so that you can
smuggle it out of iterators which open and close the ctf_file_t for you
around the loop body (like ctf_archive_iter).
You still can't use this to preserve a ctf_file_t for longer than the
lifetime of its containing entity (e.g. ctf_archive).
include/
* ctf-api.h (ctf_ref): New.
libctf/
* libctf.ver (ctf_ref): New.
* ctf-open.c (ctf_ref): Implement it.
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When opening, we consider a forward with a kind above the maximum
allowable set of kinds and a forward of kind CTF_K_UNKNOWN to be a
forward to a struct. Whatever CTF version it was that produced
forwards with no associated kind, it predates anything we can read:
remove this wart.
libctf/
* ctf-open.c (init_types): Remove typeless CTF_K_FORWARD
special-casing.
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We were accidentally interning newly-added and newly-opened
non-root-visible types into name tables, and removing names from name
tables when such types were removed. This is very wrong: the whole
point of non-root-visible types is they do not go in name tables and
cannot be looked up by name. This bug made non-root-visible types
basically identical to root-visible types, right back to the earliest
days of libctf in the Solaris era.
libctf/
* ctf-open.c (init_types): Only intern root-visible types.
* ctf-create.c (ctf_dtd_insert): Likewise.
(ctf_dtd_delete): Only remove root-visible types.
(ctf_rollback): Likewise.
(ctf_add_generic): Adjust.
(ctf_add_struct_sized): Adjust comment.
(ctf_add_union_sized): Likewise.
(ctf_add_enum): Likewise.
* ctf-impl.h (ctf_dtd_insert): Adjust prototype.
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A little tabdamage predating the linker patch series has crept in.
New in v5.
libctf/
* ctf-open.c (ctf_bufopen_internal): Fix tabdamage.
* ctf-types.c (ctf_type_lname): Likewise.
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Calling ctf_import (fp, NULL) to cancel out a pre-existing import leaked
the refcnt increment on the parent, so it could never be freed.
New in v4.
libctf/
* ctf-open.c (ctf_import): Do not leak a ctf_file_t ref on every
ctf_import after the first for a given file.
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These just get in the way of auditing for erroneous usage of strdup and
add a huge irregular surface of "ctf_malloc or malloc? ctf_free or free?
ctf_strdup or strdup?"
ctf_malloc and ctf_free usage has not reliably matched up for many
years, if ever, making the whole game pointless.
Go back to malloc, free, and strdup like everyone else: while we're at
it, fix a bunch of places where we weren't properly checking for OOM.
This changes the interface of ctf_cuname_set and ctf_parent_name_set,
which could strdup but could not return errors (like ENOMEM).
New in v4.
include/
* ctf-api.h (ctf_cuname_set): Can now fail, returning int.
(ctf_parent_name_set): Likewise.
libctf/
* ctf-impl.h (ctf_alloc): Remove.
(ctf_free): Likewise.
(ctf_strdup): Likewise.
* ctf-subr.c (ctf_alloc): Remove.
(ctf_free): Likewise.
* ctf-util.c (ctf_strdup): Remove.
* ctf-create.c (ctf_serialize): Use malloc, not ctf_alloc; free, not
ctf_free; strdup, not ctf_strdup.
(ctf_dtd_delete): Likewise.
(ctf_dvd_delete): Likewise.
(ctf_add_generic): Likewise.
(ctf_add_function): Likewise.
(ctf_add_enumerator): Likewise.
(ctf_add_member_offset): Likewise.
(ctf_add_variable): Likewise.
(membadd): Likewise.
(ctf_compress_write): Likewise.
(ctf_write_mem): Likewise.
* ctf-decl.c (ctf_decl_push): Likewise.
(ctf_decl_fini): Likewise.
(ctf_decl_sprintf): Likewise. Check for OOM.
* ctf-dump.c (ctf_dump_append): Use malloc, not ctf_alloc; free, not
ctf_free; strdup, not ctf_strdup.
(ctf_dump_free): Likewise.
(ctf_dump): Likewise.
* ctf-open.c (upgrade_types_v1): Likewise.
(init_types): Likewise.
(ctf_file_close): Likewise.
(ctf_bufopen_internal): Likewise. Check for OOM.
(ctf_parent_name_set): Likewise: report the OOM to the caller.
(ctf_cuname_set): Likewise.
(ctf_import): Likewise.
* ctf-string.c (ctf_str_purge_atom_refs): Use malloc, not ctf_alloc;
free, not ctf_free; strdup, not ctf_strdup.
(ctf_str_free_atom): Likewise.
(ctf_str_create_atoms): Likewise.
(ctf_str_add_ref_internal): Likewise.
(ctf_str_remove_ref): Likewise.
(ctf_str_write_strtab): Likewise.
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The code to handle structures (and unions) that refer to themselves in
ctf_add_type is extremely dodgy. It works by looking through the list
of not-yet-committed types for a structure with the same name as the
structure in question and assuming, if it finds it, that this must be a
reference to the same type. This is a linear search that gets ever
slower as the dictionary grows, requiring you to call ctf_update at
intervals to keep performance tolerable: but if you do that, you run
into the problem that if a forward declared before the ctf_update is
changed to a structure afterwards, ctf_update explodes.
The last commit fixed most of this: this commit can use it, adding a new
ctf_add_processing hash that tracks source type IDs that are currently
being processed and uses it to avoid infinite recursion rather than the
dynamic type list: we split ctf_add_type into a ctf_add_type_internal,
so that ctf_add_type itself can become a wrapper that empties out this
being-processed hash once the entire recursive type addition is over.
Structure additions themselves avoid adding their dependent types
quite so much by checking the type mapping and avoiding re-adding types
we already know we have added.
We also add support for adding forwards to dictionaries that already
contain the thing they are a forward to: we just silently return the
original type.
v4: return existing struct/union/enum types properly, rather than using
an uninitialized variable: shrinks sizes of CTF sections back down
to roughly where they were in v1/v2 of this patch series.
v5: fix tabdamage.
libctf/
* ctf-impl.h (ctf_file_t) <ctf_add_processing>: New.
* ctf-open.c (ctf_file_close): Free it.
* ctf-create.c (ctf_serialize): Adjust.
(membcmp): When reporting a conflict due to an error, report the
error.
(ctf_add_type): Turn into a ctf_add_processing wrapper. Rename to...
(ctf_add_type_internal): ... this. Hand back types we are already
in the middle of adding immediately. Hand back structs/unions with
the same number of members immediately. Do not walk the dynamic
list. Call ctf_add_type_internal, not ctf_add_type. Handle
forwards promoted to other types and the inverse case identically.
Add structs to the mapping as soon as we intern them, before they
gain any members.
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The method of operation of libctf when the dictionary is writable has
before now been that types that are added land in the dynamic type
section, which is a linked list and hash of IDs -> dynamic type
definitions (and, recently a hash of names): the DTDs are a bit of CTF
representing the ctf_type_t and ad hoc C structures representing the
vlen. Historically, libctf was unable to do anything with these types,
not even look them up by ID, let alone by name: if you wanted to do that
say if you were adding a type that depended on one you just added) you
called ctf_update, which serializes all the DTDs into a CTF file and
reopens it, copying its guts over the fp it's called with. The
ctf_updated types are then frozen in amber and unchangeable: all lookups
will return the types in the static portion in preference to the dynamic
portion, and we will refuse to re-add things that already exist in the
static portion (and, of late, in the dynamic portion too). The libctf
machinery remembers the boundary between static and dynamic types and
looks in the right portion for each type. Lots of things still don't
quite work with dynamic types (e.g. getting their size), but enough
works to do a bunch of additions and then a ctf_update, most of the
time.
Except it doesn't, because ctf_add_type finds it necessary to walk the
full dynamic type definition list looking for types with matching names,
so it gets slower and slower with every type you add: fixing this
requires calling ctf_update periodically for no other reason than to
avoid massively slowing things down.
This is all clunky and very slow but kind of works, until you consider
that it is in fact possible and indeed necessary to modify one sort of
type after it has been added: forwards. These are necessarily promoted
to structs, unions or enums, and when they do so *their type ID does not
change*. So all of a sudden we are changing types that already exist in
the static portion. ctf_update gets massively confused by this and
allocates space enough for the forward (with no members), but then emits
the new dynamic type (with all the members) into it. You get an
assertion failure after that, if you're lucky, or a coredump.
So this commit rejigs things a bit and arranges to exclusively use the
dynamic type definitions in writable dictionaries, and the static type
definitions in readable dictionaries: we don't at any time have a mixture
of static and dynamic types, and you don't need to call ctf_update to
make things "appear". The ctf_dtbyname hash I introduced a few months
ago, which maps things like "struct foo" to DTDs, is removed, replaced
instead by a change of type of the four dictionaries which track names.
Rather than just being (unresizable) ctf_hash_t's populated only at
ctf_bufopen time, they are now a ctf_names_t structure, which is a pair
of ctf_hash_t and ctf_dynhash_t, with the ctf_hash_t portion being used
in readonly dictionaries, and the ctf_dynhash_t being used in writable
ones. The decision as to which to use is centralized in the new
functions ctf_lookup_by_rawname (which takes a type kind) and
ctf_lookup_by_rawhash, which it calls (which takes a ctf_names_t *.)
This change lets us switch from using static to dynamic name hashes on
the fly across the entirety of libctf without complexifying anything: in
fact, because we now centralize the knowledge about how to map from type
kind to name hash, it actually simplifies things and lets us throw out
quite a lot of now-unnecessary complexity, from ctf_dtnyname (replaced
by the dynamic half of the name tables), through to ctf_dtnextid (now
that a dictionary's static portion is never referenced if the dictionary
is writable, we can just use ctf_typemax to indicate the maximum type:
dynamic or non-dynamic does not matter, and we no longer need to track
the boundary between the types). You can now ctf_rollback() as far as
you like, even past a ctf_update or for that matter a full writeout; all
the iteration functions work just as well on writable as on read-only
dictionaries; ctf_add_type no longer needs expensive duplicated code to
run over the dynamic types hunting for ones it might be interested in;
and the linker no longer needs a hack to call ctf_update so that calling
ctf_add_type is not impossibly expensive.
There is still a bit more complexity: some new code paths in ctf-types.c
need to know how to extract information from dynamic types. This
complexity will go away again in a few months when libctf acquires a
proper intermediate representation.
You can still call ctf_update if you like (it's public API, after all),
but its only effect now is to set the point to which ctf_discard rolls
back.
Obviously *something* still needs to serialize the CTF file before
writeout, and this job is done by ctf_serialize, which does everything
ctf_update used to except set the counter used by ctf_discard. It is
automatically called by the various functions that do CTF writeout:
nobody else ever needs to call it.
With this in place, forwards that are promoted to non-forwards no longer
crash the link, even if it happens tens of thousands of types later.
v5: fix tabdamage.
libctf/
* ctf-impl.h (ctf_names_t): New.
(ctf_lookup_t) <ctf_hash>: Now a ctf_names_t, not a ctf_hash_t.
(ctf_file_t) <ctf_structs>: Likewise.
<ctf_unions>: Likewise.
<ctf_enums>: Likewise.
<ctf_names>: Likewise.
<ctf_lookups>: Improve comment.
<ctf_ptrtab_len>: New.
<ctf_prov_strtab>: New.
<ctf_str_prov_offset>: New.
<ctf_dtbyname>: Remove, redundant to the names hashes.
<ctf_dtnextid>: Remove, redundant to ctf_typemax.
(ctf_dtdef_t) <dtd_name>: Remove.
<dtd_data>: Note that the ctt_name is now populated.
(ctf_str_atom_t) <csa_offset>: This is now the strtab
offset for internal strings too.
<csa_external_offset>: New, the external strtab offset.
(CTF_INDEX_TO_TYPEPTR): Handle the LCTF_RDWR case.
(ctf_name_table): New declaration.
(ctf_lookup_by_rawname): Likewise.
(ctf_lookup_by_rawhash): Likewise.
(ctf_set_ctl_hashes): Likewise.
(ctf_serialize): Likewise.
(ctf_dtd_insert): Adjust.
(ctf_simple_open_internal): Likewise.
(ctf_bufopen_internal): Likewise.
(ctf_list_empty_p): Likewise.
(ctf_str_remove_ref): Likewise.
(ctf_str_add): Returns uint32_t now.
(ctf_str_add_ref): Likewise.
(ctf_str_add_external): Now returns a boolean (int).
* ctf-string.c (ctf_strraw_explicit): Check the ctf_prov_strtab
for strings in the appropriate range.
(ctf_str_create_atoms): Create the ctf_prov_strtab. Detect OOM
when adding the null string to the new strtab.
(ctf_str_free_atoms): Destroy the ctf_prov_strtab.
(ctf_str_add_ref_internal): Add make_provisional argument. If
make_provisional, populate the offset and fill in the
ctf_prov_strtab accordingly.
(ctf_str_add): Return the offset, not the string.
(ctf_str_add_ref): Likewise.
(ctf_str_add_external): Return a success integer.
(ctf_str_remove_ref): New, remove a single ref.
(ctf_str_count_strtab): Do not count the initial null string's
length or the existence or length of any unreferenced internal
atoms.
(ctf_str_populate_sorttab): Skip atoms with no refs.
(ctf_str_write_strtab): Populate the nullstr earlier. Add one
to the cts_len for the null string, since it is no longer done
in ctf_str_count_strtab. Adjust for csa_external_offset rename.
Populate the csa_offset for both internal and external cases.
Flush the ctf_prov_strtab afterwards, and reset the
ctf_str_prov_offset.
* ctf-create.c (ctf_grow_ptrtab): New.
(ctf_create): Call it. Initialize new fields rather than old
ones. Tell ctf_bufopen_internal that this is a writable dictionary.
Set the ctl hashes and data model.
(ctf_update): Rename to...
(ctf_serialize): ... this. Leave a compatibility function behind.
Tell ctf_simple_open_internal that this is a writable dictionary.
Pass the new fields along from the old dictionary. Drop
ctf_dtnextid and ctf_dtbyname. Use ctf_strraw, not dtd_name.
Do not zero out the DTD's ctt_name.
(ctf_prefixed_name): Rename to...
(ctf_name_table): ... this. No longer return a prefixed name: return
the applicable name table instead.
(ctf_dtd_insert): Use it, and use the right name table. Pass in the
kind we're adding. Migrate away from dtd_name.
(ctf_dtd_delete): Adjust similarly. Remove the ref to the
deleted ctt_name.
(ctf_dtd_lookup_type_by_name): Remove.
(ctf_dynamic_type): Always return NULL on read-only dictionaries.
No longer check ctf_dtnextid: check ctf_typemax instead.
(ctf_snapshot): No longer use ctf_dtnextid: use ctf_typemax instead.
(ctf_rollback): Likewise. No longer fail with ECTF_OVERROLLBACK. Use
ctf_name_table and the right name table, and migrate away from
dtd_name as in ctf_dtd_delete.
(ctf_add_generic): Pass in the kind explicitly and pass it to
ctf_dtd_insert. Use ctf_typemax, not ctf_dtnextid. Migrate away
from dtd_name to using ctf_str_add_ref to populate the ctt_name.
Grow the ptrtab if needed.
(ctf_add_encoded): Pass in the kind.
(ctf_add_slice): Likewise.
(ctf_add_array): Likewise.
(ctf_add_function): Likewise.
(ctf_add_typedef): Likewise.
(ctf_add_reftype): Likewise. Initialize the ctf_ptrtab, checking
ctt_name rather than dtd_name.
(ctf_add_struct_sized): Pass in the kind. Use
ctf_lookup_by_rawname, not ctf_hash_lookup_type /
ctf_dtd_lookup_type_by_name.
(ctf_add_union_sized): Likewise.
(ctf_add_enum): Likewise.
(ctf_add_enum_encoded): Likewise.
(ctf_add_forward): Likewise.
(ctf_add_type): Likewise.
(ctf_compress_write): Call ctf_serialize: adjust for ctf_size not
being initialized until after the call.
(ctf_write_mem): Likewise.
(ctf_write): Likewise.
* ctf-archive.c (arc_write_one_ctf): Likewise.
* ctf-lookup.c (ctf_lookup_by_name): Use ctf_lookuup_by_rawhash, not
ctf_hash_lookup_type.
(ctf_lookup_by_id): No longer check the readonly types if the
dictionary is writable.
* ctf-open.c (init_types): Assert that this dictionary is not
writable. Adjust to use the new name hashes, ctf_name_table,
and ctf_ptrtab_len. GNU style fix for the final ptrtab scan.
(ctf_bufopen_internal): New 'writable' parameter. Flip on LCTF_RDWR
if set. Drop out early when dictionary is writable. Split the
ctf_lookups initialization into...
(ctf_set_cth_hashes): ... this new function.
(ctf_simple_open_internal): Adjust. New 'writable' parameter.
(ctf_simple_open): Adjust accordingly.
(ctf_bufopen): Likewise.
(ctf_file_close): Destroy the appropriate name hashes. No longer
destroy ctf_dtbyname, which is gone.
(ctf_getdatasect): Remove spurious "extern".
* ctf-types.c (ctf_lookup_by_rawname): New, look up types in the
specified name table, given a kind.
(ctf_lookup_by_rawhash): Likewise, given a ctf_names_t *.
(ctf_member_iter): Add support for iterating over the
dynamic type list.
(ctf_enum_iter): Likewise.
(ctf_variable_iter): Likewise.
(ctf_type_rvisit): Likewise.
(ctf_member_info): Add support for types in the dynamic type list.
(ctf_enum_name): Likewise.
(ctf_enum_value): Likewise.
(ctf_func_type_info): Likewise.
(ctf_func_type_args): Likewise.
* ctf-link.c (ctf_accumulate_archive_names): No longer call
ctf_update.
(ctf_link_write): Likewise.
(ctf_link_intern_extern_string): Adjust for new
ctf_str_add_external return value.
(ctf_link_add_strtab): Likewise.
* ctf-util.c (ctf_list_empty_p): New.
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We shouldn't use these, since binutils doesn't require a C99-capable
compiler yet.
New in v3.
v5: fix tabdamage.
libctf/
* ctf-open.c (flip_lbls): Eschew for-loop initial declarations.
(flip_objts): Likewise.
(flip_vars): Likewise.
(flip_types): Likewise.
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Once the deduplicator is capable of actually detecting conflicting types
with the same name (i.e., not yet) we will place such conflicting types,
and types that depend on them, into CTF dictionaries that are the child
of the main dictionary we usually emit: currently, this will lead to the
.ctf section becoming a CTF archive rather than a single dictionary,
with the default-named archive member (_CTF_SECTION, or NULL) being the
main shared dictionary with most of the types in it.
By default, the sections are named after the compilation unit they come
from (complete path and all), with the cuname field in the CTF header
providing further evidence of the name without requiring the caller to
engage in tiresome parsing. But some callers may not wish the mapping
from input CU to output sub-dictionary to be purely CU-based.
The machinery here allows this to be freely changed, in two ways:
- callers can call ctf_link_add_cu_mapping to specify that a single
input compilation unit should have its types placed in some other CU
if they conflict: the CU will always be created, even if empty, so
the consuming program can depend on its existence. You can map
multiple input CUs to one output CU to force all their types to be
merged together: if some of *those* types conflict, the behaviour is
currently unspecified (the new deduplicator will specify it).
- callers can call ctf_link_set_memb_name_changer to provide a function
which is passed every CTF sub-dictionary name in turn (including
_CTF_SECTION) and can return a new name, or NULL if no change is
desired. The mapping from input to output names should not map two
input names to the same output name: if this happens, the two are not
merged but will result in an archive with two members with the same
name (technically valid, but it's hard to access the second
same-named member: you have to do an iteration over archive members).
This is used by the kernel's ctfarchive machinery (not yet upstream) to
encode CTF under member names like {module name}.ctf rather than
.ctf.CU, but it is anticipated that other large projects may wish to
have their own storage for CTF outside of .ctf sections and may wish to
have new naming schemes that suit their special-purpose consumers.
New in v3.
v4: check for strdup failure.
v5: fix tabdamage.
include/
* ctf-api.h (ctf_link_add_cu_mapping): New.
(ctf_link_memb_name_changer_f): New.
(ctf_link_set_memb_name_changer): New.
libctf/
* ctf-impl.h (ctf_file_t) <ctf_link_cu_mappping>: New.
<ctf_link_memb_name_changer>: Likewise.
<ctf_link_memb_name_changer_arg>: Likewise.
* ctf-create.c (ctf_update): Update accordingly.
* ctf-open.c (ctf_file_close): Likewise.
* ctf-link.c (ctf_create_per_cu): Apply the cu mapping.
(ctf_link_add_cu_mapping): New.
(ctf_link_set_memb_name_changer): Likewise.
(ctf_change_parent_name): New.
(ctf_name_list_accum_cb_arg_t) <dynames>: New, storage for names
allocated by the caller's ctf_link_memb_name_changer.
<ndynames>: Likewise.
(ctf_accumulate_archive_names): Call the ctf_link_memb_name_changer.
(ctf_link_write): Likewise (for _CTF_SECTION only): also call
ctf_change_parent_name. Free any resulting names.
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This lets you call ctf_type_mapping (dest_fp, src_fp, src_type_id)
and get told what type ID the corresponding type has in the target
ctf_file_t. This works even if it was added by a recursive call, and
because it is stored in the target ctf_file_t it works even if we
had to add one type to multiple ctf_file_t's as part of conflicting
type handling.
We empty out this mapping after every archive is linked: because it maps
input to output fps, and we only visit each input fp once, its contents
are rendered entirely useless every time the source fp changes.
v3: add several missing mapping additions. Add ctf_dynhash_empty, and
empty after every input archive.
v5: fix tabdamage.
libctf/
* ctf-impl.h (ctf_file_t): New field ctf_link_type_mapping.
(struct ctf_link_type_mapping_key): New.
(ctf_hash_type_mapping_key): Likewise.
(ctf_hash_eq_type_mapping_key): Likewise.
(ctf_add_type_mapping): Likewise.
(ctf_type_mapping): Likewise.
(ctf_dynhash_empty): Likewise.
* ctf-open.c (ctf_file_close): Update accordingly.
* ctf-create.c (ctf_update): Likewise.
(ctf_add_type): Populate the mapping.
* ctf-hash.c (ctf_hash_type_mapping_key): Hash a type mapping key.
(ctf_hash_eq_type_mapping_key): Check the key for equality.
(ctf_dynhash_insert): Fix comment typo.
(ctf_dynhash_empty): New.
* ctf-link.c (ctf_add_type_mapping): New.
(ctf_type_mapping): Likewise.
(empty_link_type_mapping): New.
(ctf_link_one_input_archive): Call it.
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|
This is the start of work on the core of the linking mechanism for CTF
sections. This commit handles the type and string sections.
The linker calls these functions in sequence:
ctf_link_add_ctf: to add each CTF section in the input in turn to a
newly-created ctf_file_t (which will appear in the output, and which
itself will become the shared parent that contains types that all
TUs have in common (in all link modes) and all types that do not
have conflicting definitions between types (by default). Input files
that are themselves products of ld -r are supported, though this is
not heavily tested yet.
ctf_link: called once all input files are added to merge the types in
all the input containers into the output container, eliminating
duplicates.
ctf_link_add_strtab: called once the ELF string table is finalized and
all its offsets are known, this calls a callback provided by the
linker which returns the string content and offset of every string in
the ELF strtab in turn: all these strings which appear in the input
CTF strtab are eliminated from it in favour of the ELF strtab:
equally, any strings that only appear in the input strtab will
reappear in the internal CTF strtab of the output.
ctf_link_shuffle_syms (not yet implemented): called once the ELF symtab
is finalized, this calls a callback provided by the linker which
returns information on every symbol in turn as a ctf_link_sym_t. This
is then used to shuffle the function info and data object sections in
the CTF section into symbol table order, eliminating the index
sections which map those sections to symbol names before that point.
Currently just returns ECTF_NOTYET.
ctf_link_write: Returns a buffer containing either a serialized
ctf_file_t (if there are no types with conflicting definitions in the
object files in the link) or a ctf_archive_t containing a large
ctf_file_t (the common types) and a bunch of small ones named after
individual CUs in which conflicting types are found (containing the
conflicting types, and all types that reference them). A threshold
size above which compression takes place is passed as one parameter.
(Currently, only gzip compression is supported, but I hope to add lzma
as well.)
Lifetime rules for this are simple: don't close the input CTF files
until you've called ctf_link for the last time. We do not assume
that symbols or strings passed in by the callback outlast the
call to ctf_link_add_strtab or ctf_link_shuffle_syms.
Right now, the duplicate elimination mechanism is the one already
present as part of the ctf_add_type function, and is not particularly
good: it misses numerous actual duplicates, and the conflicting-types
detection hardly ever reports that types conflict, even when they do
(one of them just tends to get silently dropped): it is also very slow.
This will all be fixed in the next few weeks, but the fix hardly touches
any of this code, and the linker does work without it, just not as
well as it otherwise might. (And when no CTF section is present,
there is no effect on performance, of course. So only people using
a trunk GCC with not-yet-committed patches will even notice. By the
time it gets upstream, things should be better.)
v3: Fix error handling.
v4: check for strdup failure.
v5: fix tabdamage.
include/
* ctf-api.h (struct ctf_link_sym): New, a symbol in flight to the
libctf linking machinery.
(CTF_LINK_SHARE_UNCONFLICTED): New.
(CTF_LINK_SHARE_DUPLICATED): New.
(ECTF_LINKADDEDLATE): New, replacing ECTF_UNUSED.
(ECTF_NOTYET): New, a 'not yet implemented' message.
(ctf_link_add_ctf): New, add an input file's CTF to the link.
(ctf_link): New, merge the type and string sections.
(ctf_link_strtab_string_f): New, callback for feeding strtab info.
(ctf_link_iter_symbol_f): New, callback for feeding symtab info.
(ctf_link_add_strtab): New, tell the CTF linker about the ELF
strtab's strings.
(ctf_link_shuffle_syms): New, ask the CTF linker to shuffle its
symbols into symtab order.
(ctf_link_write): New, ask the CTF linker to write the CTF out.
libctf/
* ctf-link.c: New file, linking of the string and type sections.
* Makefile.am (libctf_a_SOURCES): Add it.
* Makefile.in: Regenerate.
* ctf-impl.h (ctf_file_t): New fields ctf_link_inputs,
ctf_link_outputs.
* ctf-create.c (ctf_update): Update accordingly.
* ctf-open.c (ctf_file_close): Likewise.
* ctf-error.c (_ctf_errlist): Updated with new errors.
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The CTF file format has always supported "external strtabs", which
internally are strtab offsets with their MSB on: such refs
get their strings from the strtab passed in at CTF file open time:
this is usually intended to be the ELF strtab, and that's what this
implementation is meant to support, though in theory the external
strtab could come from anywhere.
This commit adds support for these external strings in the ctf-string.c
strtab tracking layer. It's quite easy: we just add a field csa_offset
to the atoms table that tracks all strings: this field tracks the offset
of the string in the ELF strtab (with its MSB already on, courtesy of a
new macro CTF_SET_STID), and adds a new function that sets the
csa_offset to the specified offset (plus MSB). Then we just need to
avoid writing out strings to the internal strtab if they have csa_offset
set, and note that the internal strtab is shorter than it might
otherwise be.
(We could in theory save a little more time here by eschewing sorting
such strings, since we never actually write the strings out anywhere,
but that would mean storing them separately and it's just not worth the
complexity cost until profiling shows it's worth doing.)
We also have to go through a bit of extra effort at variable-sorting
time. This was previously using direct references to the internal
strtab: it couldn't use ctf_strptr or ctf_strraw because the new strtab
is not yet ready to put in its usual field (in a ctf_file_t that hasn't
even been allocated yet at this stage): but now we're using the external
strtab, this will no longer do because it'll be looking things up in the
wrong strtab, with disastrous results. Instead, pass the new internal
strtab in to a new ctf_strraw_explicit function which is just like
ctf_strraw except you can specify a ne winternal strtab to use.
But even now that it is using a new internal strtab, this is not quite
enough: it can't look up strings in the external strtab because ld
hasn't written it out yet, and when it does will write it straight to
disk. Instead, when we write the internal strtab, note all the offset
-> string mappings that we have noted belong in the *external* strtab to
a new "synthetic external strtab" dynhash, ctf_syn_ext_strtab, and look
in there at ctf_strraw time if it is set. This uses minimal extra
memory (because only strings in the external strtab that we actually use
are stored, and even those come straight out of the atoms table), but
let both variable sorting and name interning when ctf_bufopen is next
called work fine. (This also means that we don't need to filter out
spurious ECTF_STRTAB warnings from ctf_bufopen but can pass them back to
the caller, once we wrap ctf_bufopen so that we have a new internal
variant of ctf_bufopen etc that we can pass the synthetic external
strtab to. That error has been filtered out since the days of Solaris
libctf, which didn't try to handle the problem of getting external
strtabs right at construction time at all.)
v3: add the synthetic strtab and all associated machinery.
v5: fix tabdamage.
include/
* ctf.h (CTF_SET_STID): New.
libctf/
* ctf-impl.h (ctf_str_atom_t) <csa_offset>: New field.
(ctf_file_t) <ctf_syn_ext_strtab>: Likewise.
(ctf_str_add_ref): Name the last arg.
(ctf_str_add_external) New.
(ctf_str_add_strraw_explicit): Likewise.
(ctf_simple_open_internal): Likewise.
(ctf_bufopen_internal): Likewise.
* ctf-string.c (ctf_strraw_explicit): Split from...
(ctf_strraw): ... here, with new support for ctf_syn_ext_strtab.
(ctf_str_add_ref_internal): Return the atom, not the
string.
(ctf_str_add): Adjust accordingly.
(ctf_str_add_ref): Likewise. Move up in the file.
(ctf_str_add_external): New: update the csa_offset.
(ctf_str_count_strtab): Only account for strings with no csa_offset
in the internal strtab length.
(ctf_str_write_strtab): If the csa_offset is set, update the
string's refs without writing the string out, and update the
ctf_syn_ext_strtab. Make OOM handling less ugly.
* ctf-create.c (struct ctf_sort_var_arg_cb): New.
(ctf_update): Handle failure to populate the strtab. Pass in the
new ctf_sort_var arg. Adjust for ctf_syn_ext_strtab addition.
Call ctf_simple_open_internal, not ctf_simple_open.
(ctf_sort_var): Call ctf_strraw_explicit rather than looking up
strings by hand.
* ctf-hash.c (ctf_hash_insert_type): Likewise (but using
ctf_strraw). Adjust to diagnose ECTF_STRTAB nonetheless.
* ctf-open.c (init_types): No longer filter out ECTF_STRTAB.
(ctf_file_close): Destroy the ctf_syn_ext_strtab.
(ctf_simple_open): Rename to, and reimplement as a wrapper around...
(ctf_simple_open_internal): ... this new function, which calls
ctf_bufopen_internal.
(ctf_bufopen): Rename to, and reimplement as a wrapper around...
(ctf_bufopen_internal): ... this new function, which sets
ctf_syn_ext_strtab.
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No code handles these yet, but our latest GCC patches are generating
them, so we have to be ready for them or erroneously conclude that we
have file corruption.
(This simultaneously fixes a longstanding bug, concealed because nothing
was generating anything in the object or function info sections, where
the end of the section was being tested against the wrong thing: it
would have walked over the entire contents of the variable section and
treated them as part of the function info section. This had to change
now anyway because the new sections have landed in between.)
include/
* ctf.h: Add object index and function index sections. Describe
them. Improve the description of the variable section and clarify
the constraints on backward-pointing type nodes.
(ctf_header): Add cth_objtidxoff, cth_funcidxoff.
libctf/
* ctf-open.c (init_symtab): Check for overflow against the right
section.
(upgrade_header): Set cth_objtidxoff, cth_funcidxoff to zero-length.
(upgrade_types_v1): Note that these sections are not checked.
(flip_header): Endian-swap the header fields.
(flip_ctf): Endian-swap the sections.
(flip_objts): Update comment.
(ctf_bufopen): Check header offsets and alignment for validity.
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The code in ctf_bfdopen_ctfsect (which is the ultimate place where you
end up if you use ctf_open to open a CTF file and pull in the ELF string
and symbol tables) was written before it was possible to actually test
it, since the linker was not written. Now it is, it turns out that the
previous code was completely nonfunctional: it assumed that you could
load the symbol table via bfd_section_from_elf_index (...,elf_onesymtab())
and the string table via bfd_section_from_elf_index on the sh_link.
Unfortunately BFD loads neither of these sections in the conventional
fashion it uses for most others: the symbol table is immediately
converted into internal form (which is useless for our purposes, since
we also have to work in the absence of BFD for readelf, etc) and the
string table is loaded specially via bfd_elf_get_str_section which is
private to bfd/elf.c.
So make this function public, export it in elf-bfd.h, and use it from
libctf, which does something similar to what bfd_elf_sym_name and
bfd_elf_string_from_elf_section do. Similarly, load the symbol table
manually using bfd_elf_get_elf_syms and throw away the internal form
it generates for us (we never use it).
BFD allocates the strtab for us via bfd_alloc, so we can leave BFD to
deallocate it: we allocate the symbol table ourselves before calling
bfd_elf_get_elf_syms, so we still have to free it.
Also change the rules around what you are allowed to provide: It is
useful to provide a string section but no symbol table, because CTF
sections can legitimately have no function info or data object sections
while relying on the ELF strtab for some of their strings. So allow
that combination.
v4: adjust to upstream changes. ctf_bfdopen_ctfsect's first parameter
is potentially unused again (if BFD is not in use for this link
due to not supporting an ELF target).
v5: fix tabdamage.
bfd/
* elf-bfd.h (bfd_elf_get_str_section): Add.
* elf.c (bfd_elf_get_str_section): No longer static.
libctf/
* ctf-open-bfd.c: Add <assert.h>.
(ctf_bfdopen_ctfsect): Open string and symbol tables using
techniques borrowed from bfd_elf_sym_name.
(ctf_new_archive_internal): Improve comment.
* ctf-archive.c (ctf_arc_close): Do not free the ctfi_strsect.
* ctf-open.c (ctf_bufopen): Allow opening with a string section but
no symbol section, but not vice versa.
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The CTF header has before now been thrown away too soon to be dumped
using the ctf_dump() machinery used by objdump and readelf: instead, a
kludge involving debugging-priority dumps of the header offsets on every
open was used.
Replace this with proper first-class dumping machinery just like
everything else in the CTF file, and have objdump and readelf use it.
(The dumper already had an enum value in ctf_sect_names_t for this
purpose, waiting to be used.)
v5: fix tabdamage.
libctf/
* ctf-impl.h (ctf_file_t): New field ctf_openflags.
* ctf-open.c (ctf_bufopen): Set it. No longer dump header offsets.
* ctf-dump.c (dump_header): New function, dump the CTF header.
(ctf_dump): Call it.
(ctf_dump_header_strfield): New function.
(ctf_dump_header_sectfield): Likewise.
binutils/
* objdump.c (dump_ctf_archive_member): Dump the CTF header.
* readelf.c (dump_section_as_ctf): Likewise.
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libctf supports dynamic upgrading of the type table as file format
versions change, but before now has not supported changes to the CTF
header. Doing this is complicated by the baroque storage method used:
the CTF header is kept prepended to the rest of the CTF data, just as
when read from the file, and written out from there, and is
endian-flipped in place.
This makes accessing it needlessly hard and makes it almost impossible
to make the header larger if we add fields. The general storage
machinery around the malloced ctf pointer (the 'ctf_base') is also
overcomplicated: the pointer is sometimes malloced locally and sometimes
assigned from a parameter, so freeing it requires checking to see if
that parameter was used, needlessly coupling ctf_bufopen and
ctf_file_close together.
So split the header out into a new ctf_file_t.ctf_header, which is
written out explicitly: squeeze it out of the CTF buffer whenever we
reallocate it, and use ctf_file_t.ctf_buf to skip past the header when
we do not need to reallocate (when no upgrading or endian-flipping is
required). We now track whether the CTF base can be freed explicitly
via a new ctf_dynbase pointer which is non-NULL only when freeing is
possible.
With all this done, we can upgrade the header on the fly and add new
fields as desired, via a new upgrade_header function in ctf-open.
As with other forms of upgrading, libctf upgrades older headers
automatically to the latest supported version at open time.
For a first use of this field, we add a new string field cth_cuname, and
a corresponding setter/getter pair ctf_cuname_set and ctf_cuname: this
is used by debuggers to determine whether a CTF section's types relate
to a single compilation unit, or to all compilation units in the
program. (Types with ambiguous definitions in different CUs have only
one of these types placed in the top-level shared .ctf container: the
rest are placed in much smaller per-CU containers, which have the shared
container as their parent. Since CTF must be useful in the absence of
DWARF, we store the names of the relevant CUs ourselves, so the debugger
can look them up.)
v5: fix tabdamage.
include/
* ctf-api.h (ctf_cuname): New function.
(ctf_cuname_set): Likewise.
* ctf.h: Improve comment around upgrading, no longer
implying that v2 is the target of upgrades (it is v3 now).
(ctf_header_v2_t): New, old-format header for backward
compatibility.
(ctf_header_t): Add cth_cuname: this is the first of several
header changes in format v3.
libctf/
* ctf-impl.h (ctf_file_t): New fields ctf_header, ctf_dynbase,
ctf_cuname, ctf_dyncuname: ctf_base and ctf_buf are no longer const.
* ctf-open.c (ctf_set_base): Preserve the gap between ctf_buf and
ctf_base: do not assume that it is always sizeof (ctf_header_t).
Print out ctf_cuname: only print out ctf_parname if set.
(ctf_free_base): Removed, ctf_base is no longer freed: free
ctf_dynbase instead.
(ctf_set_version): Fix spacing.
(upgrade_header): New, in-place header upgrading.
(upgrade_types): Rename to...
(upgrade_types_v1): ... this. Free ctf_dynbase, not ctf_base. No
longer track old and new headers separately. No longer allow for
header sizes explicitly: squeeze the headers out on upgrade (they
are preserved in fp->ctf_header). Set ctf_dynbase, ctf_base and
ctf_buf explicitly. Use ctf_free, not ctf_free_base.
(upgrade_types): New, also handle ctf_parmax updating.
(flip_header): Flip ctf_cuname.
(flip_types): Flip BUF explicitly rather than deriving BUF from
BASE.
(ctf_bufopen): Store the header in fp->ctf_header. Correct minimum
required alignment of objtoff and funcoff. No longer store it in
the ctf_buf unless that buf is derived unmodified from the input.
Set ctf_dynbase where ctf_base is dynamically allocated. Drop locals
that duplicate fields in ctf_file: move allocation of ctf_file
further up instead. Call upgrade_header as needed. Move
version-specific ctf_parmax initialization into upgrade_types. More
concise error handling.
(ctf_file_close): No longer test for null pointers before freeing.
Free ctf_dyncuname, ctf_dynbase, and ctf_header. Do not call
ctf_free_base.
(ctf_cuname): New.
(ctf_cuname_set): New.
* ctf-create.c (ctf_update): Populate ctf_cuname.
(ctf_gzwrite): Write out the header explicitly. Remove obsolescent
comment.
(ctf_write): Likewise.
(ctf_compress_write): Get the header from ctf_header, not ctf_base.
Fix the compression length: fp->ctf_size never counted the CTF
header. Simplify the compress call accordingly.
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ctf.h states:
> [...] the CTF string table does not contain any duplicated strings.
Unfortunately this is entirely untrue: libctf has before now made no
attempt whatsoever to deduplicate the string table. It computes the
string table's length on the fly as it adds new strings to the dynamic
CTF file, and ctf_update() just writes each string to the table and
notes the current write position as it traverses the dynamic CTF file's
data structures and builds the final CTF buffer. There is no global
view of the strings and no deduplication.
Fix this by erasing the ctf_dtvstrlen dead-reckoning length, and adding
a new dynhash table ctf_str_atoms that maps unique strings to a list
of references to those strings: a reference is a simple uint32_t * to
some value somewhere in the under-construction CTF buffer that needs
updating to note the string offset when the strtab is laid out.
Adding a string is now a simple matter of calling ctf_str_add_ref(),
which adds a new atom to the atoms table, if one doesn't already exist,
and adding the location of the reference to this atom to the refs list
attached to the atom: this works reliably as long as one takes care to
only call ctf_str_add_ref() once the final location of the offset is
known (so you can't call it on a temporary structure and then memcpy()
that structure into place in the CTF buffer, because the ref will still
point to the old location: ctf_update() changes accordingly).
Generating the CTF string table is a matter of calling
ctf_str_write_strtab(), which counts the length and number of elements
in the atoms table using the ctf_dynhash_iter() function we just added,
populating an array of pointers into the atoms table and sorting it into
order (to help compressors), then traversing this table and emitting it,
updating the refs to each atom as we go. The only complexity here is
arranging to keep the null string at offset zero, since a lot of code in
libctf depends on being able to leave strtab references at 0 to indicate
'no name'. Once the table is constructed and the refs updated, we know
how long it is, so we can realloc() the partial CTF buffer we allocated
earlier and can copy the table on to the end of it (and purge the refs
because they're not needed any more and have been invalidated by the
realloc() call in any case).
The net effect of all this is a reduction in uncompressed strtab sizes
of about 30% (perhaps a quarter to a half of all strings across the
Linux kernel are eliminated as duplicates). Of course, duplicated
strings are highly redundant, so the space saving after compression is
only about 20%: when the other non-strtab sections are factored in, CTF
sizes shrink by about 10%.
No change in externally-visible API or file format (other than the
reduction in pointless redundancy).
libctf/
* ctf-impl.h: (struct ctf_strs_writable): New, non-const version of
struct ctf_strs.
(struct ctf_dtdef): Note that dtd_data.ctt_name is unpopulated.
(struct ctf_str_atom): New, disambiguated single string.
(struct ctf_str_atom_ref): New, points to some other location that
references this string's offset.
(struct ctf_file): New members ctf_str_atoms and ctf_str_num_refs.
Remove member ctf_dtvstrlen: we no longer track the total strlen
as we add strings.
(ctf_str_create_atoms): Declare new function in ctf-string.c.
(ctf_str_free_atoms): Likewise.
(ctf_str_add): Likewise.
(ctf_str_add_ref): Likewise.
(ctf_str_purge_refs): Likewise.
(ctf_str_write_strtab): Likewise.
(ctf_realloc): Declare new function in ctf-util.c.
* ctf-open.c (ctf_bufopen): Create the atoms table.
(ctf_file_close): Destroy it.
* ctf-create.c (ctf_update): Copy-and-free it on update. No longer
special-case the position of the parname string. Construct the
strtab by calling ctf_str_add_ref and ctf_str_write_strtab after the
rest of each buffer element is constructed, not via open-coding:
realloc the CTF buffer and append the strtab to it. No longer
maintain ctf_dtvstrlen. Sort the variable entry table later, after
strtab construction.
(ctf_copy_membnames): Remove: integrated into ctf_copy_{s,l,e}members.
(ctf_copy_smembers): Drop the string offset: call ctf_str_add_ref
after buffer element construction instead.
(ctf_copy_lmembers): Likewise.
(ctf_copy_emembers): Likewise.
(ctf_create): No longer maintain the ctf_dtvstrlen.
(ctf_dtd_delete): Likewise.
(ctf_dvd_delete): Likewise.
(ctf_add_generic): Likewise.
(ctf_add_enumerator): Likewise.
(ctf_add_member_offset): Likewise.
(ctf_add_variable): Likewise.
(membadd): Likewise.
* ctf-util.c (ctf_realloc): New, wrapper around realloc that aborts
if there are active ctf_str_num_refs.
(ctf_strraw): Move to ctf-string.c.
(ctf_strptr): Likewise.
* ctf-string.c: New file, strtab manipulation.
* Makefile.am (libctf_a_SOURCES): Add it.
* Makefile.in: Regenerate.
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Testing of the first code to generate CTF_K_SLICEs on big-endian
revealed a bunch of new problems in this area. Most importantly, the
trick we did earlier to avoid wasting two bytes on padding in the
ctf_slice_t is best avoided: because it leads to the whole file after
that point no longer being naturally aligned, all multibyte accesses
from then on must use memmove() to avoid unaligned access on platforms
where that is fatal. In future, this is planned, but for now we are
still doing direct access in many places, so we must revert to making
ctf_slice_t properly aligned for storage in an array.
Rather than wasting bytes on padding, we boost the size of cts_offset
and cts_bits. This is still a waste of space (we cannot have offsets or
bits in bitfields > 256) but it cannot be avoided for now, and slices
are not so common that this will be a serious problem.
A possibly-worse endianness problem fixed at the same time involves
a codepath used only for foreign-endian, uncompressed CTF files, where
we were not copying the actual CTF data into the buffer, leading to
libctf reading only zeroes (or, possibly, uninitialized garbage).
Finally, when we read in a CTF file, we copy the header and work from
the copy. We were flipping the endianness of the header copy, and of
the body of the file buffer, but not of the header in the file buffer
itself: so if we write the file back out again we end up with an
unreadable frankenfile with header and body of different endiannesses.
Fix by flipping both copies of the header.
include/
* ctf.h (ctf_slice_t): Make cts_offset and cts_bits unsigned
short, so following structures are properly aligned.
libctf/
* ctf-open.c (get_vbytes_common): Return the new slice size.
(ctf_bufopen): Flip the endianness of the CTF-section header copy.
Remember to copy in the CTF data when opening an uncompressed
foreign-endian CTF file. Prune useless variable manipulation.
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If we see a CTF type with a kind we do not recognize in its ctt_info
during opening, we cannot skip it and continue opening the file: if the
type kind is unknown, we do not know how long its vlen is, and we cannot
have skipped past it: so if we continue reading we will almost certainly
read in part of the vlen as if it were a new ctf_type_t.
Avoid this trouble by considering unknown type kinds to be a reason to
return ECTF_CORRUPT, just like everything else that reads in type kinds
does.
libctf/
* ctf-open.c (ctf_types): Fail when unidentified type kinds are
seen.
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This is an essential first piece of info needed to debug both libctf
writing and reading problems, and we weren't recording it anywhere!
(This is a short-term fix: fairly soon, we will record all of this in a
form that outlives ctf_bufopen, and then ctf_dump() will be able to dump
it like it can everything else.)
libctf/
* ctf-open.c (ctf_bufopen): Dump header offsets into the debugging
output.
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This allocator has the ostensible benefit that it lets us mprotect() the
memory used for CTF storage: but in exchange for this it adds
considerable complexity, since we have to track allocation sizes
ourselves for use at freeing time, note whether the data we are storing
was ctf_data_alloc()ed or not so we know if we can safely mprotect()
it... and while the mprotect()ing has found few bugs, it *has* been the
cause of more than one due to errors in all this tracking leading to us
mprotect()ing bits of the heap and stuff like that.
We are about to start composing CTF buffers from pieces so that we can
do usage-based optimizations on the strtab. This means we need
realloc(), which needs nonportable mremap() and *more* tracking of the
*original* allocation size, and the complexity and bureaucracy of all of
this is just too high for its negligible benefits.
Drop the whole thing and just use malloc() like everyone else. It knows
better than we do when it is safe to use mmap() under the covers,
anyway.
While we're at it, don't leak the entire buffer if ctf_compress_write()
fails to compress it.
libctf/
* ctf-subr.c (_PAGESIZE): Remove.
(ctf_data_alloc): Likewise.
(ctf_data_free): Likewise.
(ctf_data_protect): Likewise.
* ctf-impl.h: Remove declarations.
* ctf-create.c (ctf_update): No longer call ctf_data_protect: use
ctf_free, not ctf_data_free.
(ctf_compress_write): Use ctf_data_alloc, not ctf_alloc. Free
the buffer again on compression error.
* ctf-open.c (ctf_set_base): No longer track the size: call
ctf_free, not ctf_data_free.
(upgrade_types): Likewise. Call ctf_alloc, not ctf_data_alloc.
(ctf_bufopen): Likewise. No longer call ctf_data_protect.
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- Use of nonportable <endian.h>
- Use of qsort_r
- Use of zlib without appropriate magic to pull in the binutils zlib
- Use of off64_t without checking (fixed by dropping the unused fields
that need off64_t entirely)
- signedness problems due to long being too short a type on 32-bit
platforms: ctf_id_t is now 'unsigned long', and CTF_ERR must be
used only for functions that return ctf_id_t
- One lingering use of bzero() and of <sys/errno.h>
All fixed, using code from gnulib where possible.
Relatedly, set cts_size in a couple of places it was missed
(string table and symbol table loading upon ctf_bfdopen()).
binutils/
* objdump.c (make_ctfsect): Drop cts_type, cts_flags, and
cts_offset.
* readelf.c (shdr_to_ctf_sect): Likewise.
include/
* ctf-api.h (ctf_sect_t): Drop cts_type, cts_flags, and cts_offset.
(ctf_id_t): This is now an unsigned type.
(CTF_ERR): Cast it to ctf_id_t. Note that it should only be used
for ctf_id_t-returning functions.
libctf/
* Makefile.am (ZLIB): New.
(ZLIBINC): Likewise.
(AM_CFLAGS): Use them.
(libctf_a_LIBADD): New, for LIBOBJS.
* configure.ac: Check for zlib, endian.h, and qsort_r.
* ctf-endian.h: New, providing htole64 and le64toh.
* swap.h: Code style fixes.
(bswap_identity_64): New.
* qsort_r.c: New, from gnulib (with one added #include).
* ctf-decls.h: New, providing a conditional qsort_r declaration,
and unconditional definitions of MIN and MAX.
* ctf-impl.h: Use it. Do not use <sys/errno.h>.
(ctf_set_errno): Now returns unsigned long.
* ctf-util.c (ctf_set_errno): Adjust here too.
* ctf-archive.c: Use ctf-endian.h.
(ctf_arc_open_by_offset): Use memset, not bzero. Drop cts_type,
cts_flags and cts_offset.
(ctf_arc_write): Drop debugging dependent on the size of off_t.
* ctf-create.c: Provide a definition of roundup if not defined.
(ctf_create): Drop cts_type, cts_flags and cts_offset.
(ctf_add_reftype): Do not check if type IDs are below zero.
(ctf_add_slice): Likewise.
(ctf_add_typedef): Likewise.
(ctf_add_member_offset): Cast error-returning ssize_t's to size_t
when known error-free. Drop CTF_ERR usage for functions returning
int.
(ctf_add_member_encoded): Drop CTF_ERR usage for functions returning
int.
(ctf_add_variable): Likewise.
(enumcmp): Likewise.
(enumadd): Likewise.
(membcmp): Likewise.
(ctf_add_type): Likewise. Cast error-returning ssize_t's to size_t
when known error-free.
* ctf-dump.c (ctf_is_slice): Drop CTF_ERR usage for functions
returning int: use CTF_ERR for functions returning ctf_type_id.
(ctf_dump_label): Likewise.
(ctf_dump_objts): Likewise.
* ctf-labels.c (ctf_label_topmost): Likewise.
(ctf_label_iter): Likewise.
(ctf_label_info): Likewise.
* ctf-lookup.c (ctf_func_args): Likewise.
* ctf-open.c (upgrade_types): Cast to size_t where appropriate.
(ctf_bufopen): Likewise. Use zlib types as needed.
* ctf-types.c (ctf_member_iter): Drop CTF_ERR usage for functions
returning int.
(ctf_enum_iter): Likewise.
(ctf_type_size): Likewise.
(ctf_type_align): Likewise. Cast to size_t where appropriate.
(ctf_type_kind_unsliced): Likewise.
(ctf_type_kind): Likewise.
(ctf_type_encoding): Likewise.
(ctf_member_info): Likewise.
(ctf_array_info): Likewise.
(ctf_enum_value): Likewise.
(ctf_type_rvisit): Likewise.
* ctf-open-bfd.c (ctf_bfdopen): Drop cts_type, cts_flags and
cts_offset.
(ctf_simple_open): Likewise.
(ctf_bfdopen_ctfsect): Likewise. Set cts_size properly.
* Makefile.in: Regenerate.
* aclocal.m4: Likewise.
* config.h: Likewise.
* configure: Likewise.
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These functions let you open an ELF file with a customarily-named CTF
section in it, automatically opening the CTF file or archive and
associating the symbol and string tables in the ELF file with the CTF
container, so that you can look up the types of symbols in the ELF file
via ctf_lookup_by_symbol(), and so that strings can be shared between
the ELF file and CTF container, to save space.
It uses BFD machinery to do so. This has now been lightly tested and
seems to work. In particular, if you already have a bfd you can pass
it in to ctf_bfdopen(), and if you want a bfd made for you you can
call ctf_open() or ctf_fdopen(), optionally specifying a target (or
try once without a target and then again with one if you get
ECTF_BFD_AMBIGUOUS back).
We use a forward declaration for the struct bfd in ctf-api.h, so that
ctf-api.h users are not required to pull in <bfd.h>. (This is mostly
for the sake of readelf.)
libctf/
* ctf-open-bfd.c: New file.
* ctf-open.c (ctf_close): New.
* ctf-impl.h: Include bfd.h.
(ctf_file): New members ctf_data_mmapped, ctf_data_mmapped_len.
(ctf_archive_internal): New members ctfi_abfd, ctfi_data,
ctfi_bfd_close.
(ctf_bfdopen_ctfsect): New declaration.
(_CTF_SECTION): likewise.
include/
* ctf-api.h (struct bfd): New forward.
(ctf_fdopen): New.
(ctf_bfdopen): Likewise.
(ctf_open): Likewise.
(ctf_arc_open): Likewise.
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If you need to store a large number of CTF containers somewhere, this
provides a dedicated facility for doing so: an mmappable archive format
like a very simple tar or ar without all the system-dependent format
horrors or need for heavy file copying, with built-in compression of
files above a particular size threshold.
libctf automatically mmap()s uncompressed elements of these archives, or
uncompresses them, as needed. (If the platform does not support mmap(),
copying into dynamically-allocated buffers is used.)
Archive iteration operations are partitioned into raw and non-raw
forms. Raw operations pass thhe raw archive contents to the callback:
non-raw forms open each member with ctf_bufopen() and pass the resulting
ctf_file_t to the iterator instead. This lets you manipulate the raw
data in the archive, or the contents interpreted as a CTF file, as
needed.
It is not yet known whether we will store CTF archives in a linked ELF
object in one of these (akin to debugdata) or whether they'll get one
section per TU plus one parent container for types shared between them.
(In the case of ELF objects with very large numbers of TUs, an archive
of all of them would seem preferable, so we might just use an archive,
and add lzma support so you can assume that .gnu_debugdata and .ctf are
compressed using the same algorithm if both are present.)
To make usage easier, the ctf_archive_t is not the on-disk
representation but an abstraction over both ctf_file_t's and archives of
many ctf_file_t's: users see both CTF archives and raw CTF files as
ctf_archive_t's upon opening, the only difference being that a raw CTF
file has only a single "archive member", named ".ctf" (the default if a
null pointer is passed in as the name). The next commit will make use
of this facility, in addition to providing the public interface to
actually open archives. (In the future, it should be possible to have
all CTF sections in an ELF file appear as an "archive" in the same
fashion.)
This machinery is also used to allow library-internal creators of
ctf_archive_t's (such as the next commit) to stash away an ELF string
and symbol table, so that all opens of members in a given archive will
use them. This lets CTF archives exploit the ELF string and symbol
table just like raw CTF files can.
(All this leads to somewhat confusing type naming. The ctf_archive_t is
a typedef for the opaque internal type, struct ctf_archive_internal: the
non-internal "struct ctf_archive" is the on-disk structure meant for
other libraries manipulating CTF files. It is probably clearest to use
the struct name for struct ctf_archive_internal inside the program, and
the typedef names outside.)
libctf/
* ctf-archive.c: New.
* ctf-impl.h (ctf_archive_internal): New type.
(ctf_arc_open_internal): New declaration.
(ctf_arc_bufopen): Likewise.
(ctf_arc_close_internal): Likewise.
include/
* ctf.h (CTFA_MAGIC): New.
(struct ctf_archive): New.
(struct ctf_archive_modent): Likewise.
* ctf-api.h (ctf_archive_member_f): New.
(ctf_archive_raw_member_f): Likewise.
(ctf_arc_write): Likewise.
(ctf_arc_close): Likewise.
(ctf_arc_open_by_name): Likewise.
(ctf_archive_iter): Likewise.
(ctf_archive_raw_iter): Likewise.
(ctf_get_arc): Likewise.
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This fills in the other half of the opening/creation puzzle: opening of
already-existing CTF files. Such files are always read-only: if you
want to add to a CTF file opened with one of the opening functions in
this file, use ctf_add_type(), in a later commit, to copy appropriate
types into a newly ctf_create()d, writable container.
The lowest-level opening functions are in here: ctf_bufopen(), which
takes ctf_sect_t structures akin to ELF section headers, and
ctf_simple_open(), which can be used if you don't have an entire ELF
section header to work from. Both will malloc() new space for the
buffers only if necessary, will mmap() directly from the file if
requested, and will mprotect() it afterwards to prevent accidental
corruption of the types. These functions are also used by ctf_update()
when converting types in a writable container into read-only types that
can be looked up using the lookup functions (in later commits).
The files are always of the native endianness of the system that created
them: at read time, the endianness of the header magic number is used to
determine whether or not the file needs byte-swapping, and the entire
thing is aggressively byte-swapped.
The agggressive nature of this swapping avoids complicating the rest of
the code with endianness conversions, while the native endianness
introduces no byte-swapping overhead in the common case. (The
endianness-independence code is also much newer than everything else in
this file, and deserves closer scrutiny.)
The accessors at the top of the file are there to transparently support
older versions of the CTF file format, allowing translation from older
formats that have different sizes for the structures in ctf.h:
currently, these older formats are intermingled with the newer ones in
ctf.h: they will probably migrate to a compatibility header in time, to
ease readability. The ctf_set_base() function is split out for the same
reason: when conversion code to a newer format is written, it would need
to malloc() new storage for the entire ctf_file_t if a file format
change causes it to grow, and for that we need ctf_set_base() to be a
separate function.
One pair of linked data structures supported by this file has no
creation code in libctf yet: the data and function object sections read
by init_symtab(). These will probably arrive soon, when the linker comes
to need them. (init_symtab() has hardly been changed since 2009, but if
any code in libctf has rotted over time, this will.)
A few simple accessors are also present that can even be called on
read-only containers because they don't actually modify them, since the
relevant things are not stored in the container but merely change its
operation: ctf_setmodel(), which lets you specify whether a container is
LP64 or not (used to statically determine the sizes of a few types),
ctf_import(), which is the only way to associate a parent container with
a child container, and ctf_setspecific(), which lets the caller
associate an arbitrary pointer with the CTF container for any use. If
the user doesn't call these functions correctly, libctf will misbehave:
this is particularly important for ctf_import(), since a container built
against a given parent container will not be able to resolve types that
depend on types in the parent unless it is ctf_import()ed with a parent
container with the same set of types at the same IDs, or a superset.
Possible future extensions (also noted in the ctf-hash.c file) include
storing a count of things so that we don't need to do one pass over the
CTF file counting everything, and computing a perfect hash at CTF
creation time in some compact form, storing it in the CTF file, and
using it to hash things so we don't need to do a second pass over the
entire CTF file to set up the hashes used to go from names to type IDs.
(There are multiple such hashes, one for each C type namespace: types,
enums, structs, and unions.)
libctf/
* ctf-open.c: New file.
* swap.h: Likewise.
include/
* ctf-api.h (ctf_file_close): New declaration.
(ctf_getdatasect): Likewise.
(ctf_parent_file): Likewise.
(ctf_parent_name): Likewise.
(ctf_parent_name_set): Likewise.
(ctf_import): Likewise.
(ctf_setmodel): Likewise.
(ctf_getmodel): Likewise.
(ctf_setspecific): Likewise.
(ctf_getspecific): Likewise.
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