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Every place that accesses a function's dtd_vlen accesses it only if the
number of args is nonzero, except the serializer, which always tries to
memcpy it. The number of bytes it memcpys in this case is zero, but it
is still undefined behaviour to copy zero bytes from a null pointer.
So check for this case explicitly.
libctf/ChangeLog
2021-03-25 Nick Alcock <nick.alcock@oracle.com>
PR libctf/27628
* ctf-serialize.c (ctf_emit_type_sect): Allow for a NULL vlen in
CTF_K_FUNCTION types.
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Eliminate the dynamic member storage for structs and unions as we have
for other dynamic types. This is much like the previous enum
elimination, except that structs and unions are the only types for which
a full-sized ctf_type_t might be needed. Up to now, this decision has
been made in the individual ctf_add_{struct,union}_sized functions and
duplicated in ctf_add_member_offset. The vlen machinery lets us
simplify this, always allocating a ctf_lmember_t and setting the
dtd_data's ctt_size to CTF_LSIZE_SENT: we figure out whether this is
really justified and (almost always) repack things down into a
ctf_stype_t at ctf_serialize time.
This allows us to eliminate the dynamic member paths from the iterators and
query functions in ctf-types.c in favour of always using the large-structure
vlen stuff for dynamic types (the diff is ugly but that's just because of the
volume of reindentation this calls for). This also means the large-structure
vlen stuff gets more heavily tested, which is nice because it was an almost
totally unused code path before now (it only kicked in for structures of size
>4GiB, and how often do you see those?)
The only extra complexity here is ctf_add_type. Back in the days of the
nondeduplicating linker this was called a ridiculous number of times for
countless identical copies of structures: eschewing the repeated lookups of the
dtd in ctf_add_member_offset and adding the members directly saved an amazing
amount of time. Now the nondeduplicating linker is gone, this is extreme
overoptimization: we can rip out the direct addition and use ctf_member_next and
ctf_add_member_offset, just like ctf_dedup_emit does.
We augment a ctf_add_type test to try adding a self-referential struct, the only
thing the ctf_add_type part of this change really perturbs.
This completes the elimination of dtd_u.
libctf/ChangeLog
2021-03-18 Nick Alcock <nick.alcock@oracle.com>
* ctf-impl.h (ctf_dtdef_t) <dtu_members>: Remove.
<dtd_u>: Likewise.
(ctf_dmdef_t): Remove.
(struct ctf_next) <u.ctn_dmd>: Remove.
* ctf-create.c (INITIAL_VLEN): New, more-or-less arbitrary initial
vlen size.
(ctf_add_enum): Use it.
(ctf_dtd_delete): Do not free the (removed) dmd; remove string
refs from the vlen on struct deletion.
(ctf_add_struct_sized): Populate the vlen: do it by hand if
promoting forwards. Always populate the full-size
lsizehi/lsizelo members.
(ctf_add_union_sized): Likewise.
(ctf_add_member_offset): Set up the vlen rather than the dmd.
Expand it as needed, repointing string refs via
ctf_str_move_pending. Add the member names as pending strings.
Always populate the full-size lsizehi/lsizelo members.
(membadd): Remove, folding back into...
(ctf_add_type_internal): ... here, adding via an ordinary
ctf_add_struct_sized and _next iteration rather than doing
everything by hand.
* ctf-serialize.c (ctf_copy_smembers): Remove this...
(ctf_copy_lmembers): ... and this...
(ctf_emit_type_sect): ... folding into here. Figure out if a
ctf_stype_t is needed here, not in ctf_add_*_sized.
(ctf_type_sect_size): Figure out the ctf_stype_t stuff the same
way here.
* ctf-types.c (ctf_member_next): Remove the dmd path and always
use the vlen. Force large-structure usage for dynamic types.
(ctf_type_align): Likewise.
(ctf_member_info): Likewise.
(ctf_type_rvisit): Likewise.
* testsuite/libctf-regression/type-add-unnamed-struct-ctf.c: Add a
self-referential type to this test.
* testsuite/libctf-regression/type-add-unnamed-struct.c: Adjusted
accordingly.
* testsuite/libctf-regression/type-add-unnamed-struct.lk: Likewise.
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This is the first tricky one, the first complex multi-entry vlen
containing strings. To handle this in vlen form, we have to handle
pending refs moving around on realloc.
We grow vlen regions using a new ctf_grow_vlen function, and iterate
through the existing enums every time a grow happens, telling the string
machinery the distance between the old and new vlen region and letting
it adjust the pending refs accordingly. (This avoids traversing all
outstanding refs to find the refs that need adjusting, at the cost of
having to traverse one enum: an obvious major performance win.)
Addition of enums themselves (and also structs/unions later) is a bit
trickier than earlier forms, because the type might be being promoted
from a forward, and forwards have no vlen: so we have to spot that and
create it if needed.
Serialization of enums simplifies down to just telling the string
machinery about the string refs; all the enum type-lookup code loses all
its dynamic member lookup complexity entirely.
A new test is added that iterates over (and gets values of) an enum with
enough members to force a round of vlen growth.
libctf/ChangeLog
2021-03-18 Nick Alcock <nick.alcock@oracle.com>
* ctf-impl.h (ctf_dtdef_t) <dtd_vlen_alloc>: New.
(ctf_str_move_pending): Declare.
* ctf-string.c (ctf_str_add_ref_internal): Fix error return.
(ctf_str_move_pending): New.
* ctf-create.c (ctf_grow_vlen): New.
(ctf_dtd_delete): Zero out the vlen_alloc after free. Free the
vlen later: iterate over it and free enum name refs first.
(ctf_add_generic): Populate dtd_vlen_alloc from vlen.
(ctf_add_enum): populate the vlen; do it by hand if promoting
forwards.
(ctf_add_enumerator): Set up the vlen rather than the dmd. Expand
it as needed, repointing string refs via ctf_str_move_pending. Add
the enumerand names as pending strings.
* ctf-serialize.c (ctf_copy_emembers): Remove.
(ctf_emit_type_sect): Copy the vlen into place and ref the
strings.
* ctf-types.c (ctf_enum_next): The dynamic portion now uses
the same code as the non-dynamic.
(ctf_enum_name): Likewise.
(ctf_enum_value): Likewise.
* testsuite/libctf-lookup/enum-many-ctf.c: New test.
* testsuite/libctf-lookup/enum-many.lk: New test.
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The preceding change revealed a new bug: the string table is sorted for
better compression, so repeated serialization with type (or member)
additions in the middle can move strings around. But every
serialization flushes the set of refs (the memory locations that are
automatically updated with a final string offset when the strtab is
updated), so if we are not to have string offsets go stale, we must do
all ref additions within the serialization code (which walks the
complete set of types and symbols anyway). Unfortunately, we were adding
one ref in another place: the type name in the dynamic type definitions,
which has a ref added to it by ctf_add_generic.
So adding a type, serializing (via, say, one of the ctf_write
functions), adding another type with a name that sorts earlier, and
serializing again will corrupt the name of the first type because it no
longer had a ref pointing to its dtd entry's name when its string offset
was shifted later in the strtab to mae way for the other type.
To ensure that we don't miss strings, we also maintain a set of *pending
refs* that will be added later (during serialization), and remove
entries from that set when the ref is finally added. We always use
ctf_str_add_pending outside ctf-serialize.c, ensure that ctf_serialize
adds all strtab offsets as refs (even those in the dtds) on every
serialization, and mandate that no refs are live on entry to
ctf_serialize and that all pending refs are gone before strtab
finalization. (Of necessity ctf_serialize has to traverse all strtab
offsets in the dtds in order to serialize them, so adding them as refs
at the same time is easy.)
(Note that we still can't erase unused atoms when we roll back, though
we can erase unused refs: members and enums are still not removed by
rollbacks and might reference strings added after the snapshot.)
libctf/ChangeLog
2021-03-18 Nick Alcock <nick.alcock@oracle.com>
* ctf-hash.c (ctf_dynset_elements): New.
* ctf-impl.h (ctf_dynset_elements): Declare it.
(ctf_str_add_pending): Likewise.
(ctf_dict_t) <ctf_str_pending_ref>: New, set of refs that must be
added during serialization.
* ctf-string.c (ctf_str_create_atoms): Initialize it.
(CTF_STR_ADD_REF): New flag.
(CTF_STR_MAKE_PROVISIONAL): Likewise.
(CTF_STR_PENDING_REF): Likewise.
(ctf_str_add_ref_internal): Take a flags word rather than int
params. Populate, and clear out, ctf_str_pending_ref.
(ctf_str_add): Adjust accordingly.
(ctf_str_add_external): Likewise.
(ctf_str_add_pending): New.
(ctf_str_remove_ref): Also remove the potential ref if it is a
pending ref.
* ctf-serialize.c (ctf_serialize): Prohibit addition of strings
with ctf_str_add_ref before serialization. Ensure that the
ctf_str_pending_ref set is empty before strtab finalization.
(ctf_emit_type_sect): Add a ref to the ctt_name.
* ctf-create.c (ctf_add_generic): Add the ctt_name as a pending
ref.
* testsuite/libctf-writable/reserialize-strtab-corruption.*: New test.
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One pattern which is rarely done in libctf but which is meant to work is
this:
ctf_create();
ctf_add_*(); // add stuff
ctf_type_*() // look stuff up
ctf_write_*();
ctf_add_*(); // should still work
ctf_type_*() // so should this
ctf_write_*(); // and this
i.e., writing out a dict should not break it and you should be able to
do everything you could do with it before, including writing it out
again.
Unfortunately this has been broken for a while because the field which
indicates the maximum valid type ID was not preserved across
serialization: so type additions after serialization would overwrite
types (obviously disastrous) and type lookups would just fail.
Fix trivial.
libctf/ChangeLog
2021-03-18 Nick Alcock <nick.alcock@oracle.com>
* ctf-serialize.c (ctf_serialize): Preserve ctf_typemax across
serialization.
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One more member vanishes from the dtd_u, leaving only the member for
struct/union/enum members.
There's not much to do here, since as of commit afd78bd6f0a30ba5 we use
the same representation (type sizes, etc) in the dtu_argv as we will
use in the final vlen, with one exception: the vlen has alignment
padding, and the dtu_argv did not. Simplify things by adding suitable
padding in both cases.
libctf/ChangeLog
2021-03-18 Nick Alcock <nick.alcock@oracle.com>
* ctf-impl.h (ctf_dtdef_t) <dtd_u.dtu_argv>: Remove.
* ctf-create.c (ctf_dtd_delete): No longer free it.
(ctf_add_function): Use the dtd_vlen, not dtu_argv. Properly align.
* ctf-serialize.c (ctf_emit_type_sect): Just copy the dtd_vlen.
* ctf-types.c (ctf_func_type_info): Just use the vlen.
(ctf_func_type_args): Likewise.
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This is even simpler than ints, floats and slices, with the only extra
complication being the need to manually transfer the array parameter in
the rarely-used function ctf_set_array. (Arrays are unique in libctf in
that they can be modified post facto, not just created and appended to.
I'm not sure why they got this exemption, but it's easy to maintain.)
libctf/ChangeLog
2021-03-18 Nick Alcock <nick.alcock@oracle.com>
* ctf-impl.h (ctf_dtdef_t) <dtd_u.dtu_arr>: Remove.
* ctf-create.c (ctf_add_array): Use the dtd_vlen, not dtu_arr.
(ctf_set_array): Likewise.
* ctf-serialize.c (ctf_emit_type_sect): Just copy the dtd_vlen.
* ctf-types.c (ctf_array_info): Just use the vlen.
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This series eliminates a lot of special-case code to handle dynamic
types (types added to writable dicts and not yet serialized).
Historically, when such types have variable-length data in their final
CTF representations, libctf has always worked by adding such types to a
special union (ctf_dtdef_t.dtd_u) in the dynamic type definition
structure, then picking the members out of this structure at
serialization time and packing them into their final form.
This has the advantage that the ctf_add_* code doesn't need to know
anything about the final CTF representation, but the significant
disadvantage that all code that looks up types in any way needs two code
paths, one for dynamic types, one for all others. Historically libctf
"handled" this by not supporting most type lookups on dynamic types at
all until ctf_update was called to do a complete reserialization of the
entire dict (it didn't emit an error, it just emitted wrong results).
Since commit 676c3ecbad6e9c4, which eliminated ctf_update in favour of
the internal-only ctf_serialize function, all the type-lookup paths
grew an extra branch to handle dynamic types.
We can eliminate this branch again by dropping the dtd_u stuff and
simply writing out the vlen in (close to) its final form at ctf_add_*
time: type lookup for types using this approach is then identical for
types in writable dicts and types that are in read-only ones, and
serialization is also simplified (we just need to write out the vlen
we already created).
The only complexity lies in type kinds for which multiple
vlen representations are valid depending on properties of the type,
e.g. structures. But we can start simple, adjusting ints, floats,
and slices to work this way, and leaving everything else as is.
libctf/ChangeLog
2021-03-18 Nick Alcock <nick.alcock@oracle.com>
* ctf-impl.h (ctf_dtdef_t) <dtd_u.dtu_enc>: Remove.
<dtd_u.dtu_slice>: Likewise.
<dtd_vlen>: New.
* ctf-create.c (ctf_add_generic): Perhaps allocate it. All
callers adjusted.
(ctf_dtd_delete): Free it.
(ctf_add_slice): Use the dtd_vlen, not dtu_enc.
(ctf_add_encoded): Likewise. Assert that this must be an int or
float.
* ctf-serialize.c (ctf_emit_type_sect): Just copy the dtd_vlen.
* ctf-dedup.c (ctf_dedup_rhash_type): Use the dtd_vlen, not
dtu_slice.
* ctf-types.c (ctf_type_reference): Likewise.
(ctf_type_encoding): Remove most dynamic-type-specific code: just
get the vlen from the right place. Report failure to look up the
underlying type's encoding.
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ctf_serialize and its various pieces may be split out into a separate
file now, but ctf_serialize is still far too long and disordered, mixing
header initialization, sizing of multiple CTF sections, sorting and
emission of multiple CTF sections, strtab construction and ctf_dict_t
copying into a single ugly organically-grown mess.
Fix the worst of this by migrating all section sizing and emission into
separate functions, two per section (or class of section in the case of
the symtypetabs). Only the variable section is now sized and emitted
directly in ctf_serialize (because it only takes about three lines to do
so).
The section sizes themselves are still maintained by ctf_serialize so
that it can work out the header offsets, but ctf_symtypetab_sect_sizes
and ctf_emit_symtypetab_sects share a lot of extra state: migrate that
into a shared structure, emit_symtypetab_state_t.
(Test results unchanged.)
libctf/ChangeLog
2021-03-18 Nick Alcock <nick.alcock@oracle.com>
* ctf-serialize.c: General reshuffling, and...
(emit_symtypetab_state_t): New, migrated from
local variables in ctf_serialize.
(ctf_serialize): Split out most section sizing and
emission.
(ctf_symtypetab_sect_sizes): New (split out).
(ctf_emit_symtypetab_sects): Likewise.
(ctf_type_sect_size): Likewise.
(ctf_emit_type_sect): Likewise.
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The code to serialize CTF dicts just gets bigger and bigger as the
dictionary's complexity grows: adding symtypetabs almost doubled it on
its own. It's long past time to split this out into its own source
file, accompanied by the functions that do the actual writeout.
This leaves ctf-create.c populated exclusively by functions related to
actual writable dict creation (ctf_add_*, ctf_create etc), and leaves
both files a much more reasonable size.
libctf/ChangeLog
2021-03-18 Nick Alcock <nick.alcock@oracle.com>
* ctf-create.c (symtypetab_delete_nonstatic_vars): Move
into ctf-serialize.c.
(ctf_symtab_skippable): Likewise.
(CTF_SYMTYPETAB_EMIT_FUNCTION): Likewise.
(CTF_SYMTYPETAB_EMIT_PAD): Likewise.
(CTF_SYMTYPETAB_FORCE_INDEXED): Likewise.
(symtypetab_density): Likewise.
(emit_symtypetab): Likewise.
(emit_symtypetab_index): Likewise.
(ctf_copy_smembers): Likewise.
(ctf_copy_lmembers): Likewise.
(ctf_copy_emembers): Likewise.
(ctf_sort_var): Likewise.
(ctf_serialize): Likewise.
(ctf_gzwrite): Likewise.
(ctf_compress_write): Likewise.
(ctf_write_mem): Likewise.
(ctf_write): Likewise.
* ctf-serialize.c: New file.
* Makefile.am (libctf_nobfd_la_SOURCES): Add it.
* Makefile.in: Regenerate.
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