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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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We were missing several cases where dynhash insertion might fail, likely
due to OOM but possibly for other reasons. Pass the errors on.
libctf/
* ctf-create.c (ctf_dtd_insert): Pass on error returns from
ctf_dynhash_insert.
(ctf_dvd_insert): Likewise.
(ctf_add_generic): Likewise.
(ctf_add_variable): Likewise.
* ctf-impl.h: Adjust declarations.
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bfd/
* Makefile.in: Regenerate.
* configure: Regenerate.
binutils/
* Makefile.in: Regenerate.
* aclocal.m4: Regenerate.
* doc/Makefile.in: Regenerate.
gas/
* Makefile.in: Regenerate.
* configure: Regenerate.
* doc/Makefile.in: Regenerate.
ld/
* Makefile.in: Regenerate.
* configure: Regenerate.
libctf/
* configure: Regenerate.
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Not all platforms have it. Use libiberty xstrndup() instead.
(The include of libiberty.h happens in an unusual place due to the
requirements of synchronization of most source files between this
project and another that does not use libiberty. It serves to pull
libiberty.h in for all source files in libctf/, which does the trick.)
Tested on x86_64-pc-linux-gnu, x86_64-unknown-freebsd12.0,
sparc-sun-solaris2.11, i686-pc-cygwin, i686-w64-mingw32.
libctf/
* ctf-decls.h: Include <libiberty.h>.
* ctf-lookup.c (ctf_lookup_by_name): Call xstrndup(), not strndup().
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Unsigned long will always be adequate (the only cases involving an
ssize_t are cases in which no error can be generated, or in which
negative output would require a seriously corrupted file: the latter has
been rewritten on a branch in any case).
Tested on x86_64-pc-linux-gnu, x86_64-unknown-freebsd12.0,
sparc-sun-solaris2.11, i686-pc-cygwin, i686-w64-mingw32.
libctf/
* ctf-dump.c (ctf_dump_format_type): Cast size_t's used in printf()s.
(ctf_dump_objts): Likewise.
(ctf_dump_funcs): Likewise.
(ctf_dump_member): Likewise.
(ctf_dump_str): Likewise.
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Tested on x86_64-pc-linux-gnu, x86_64-unknown-freebsd12.0,
sparc-sun-solaris2.11, i686-pc-cygwin, i686-w64-mingw32.
libctf/
* ctf-archive.c (arc_mmap_header): Mark fd as potentially unused.
* ctf-subr.c (ctf_data_protect): Mark both args as potentially unused.
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Too many platforms don't support it, and we can always safely use %lu or
%li anyway, because the only uses are in debugging output.
libctf/
* ctf-archive.c (ctf_arc_write): Eschew %zi format specifier.
(ctf_arc_open_by_offset): Likewise.
* ctf-create.c (ctf_add_type): Likewise.
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On x86-64 Fedora 29, I tried to build a mingw-hosted gdb that targets
ppc-linux. You can do this with:
../binutils-gdb/configure --host=i686-w64-mingw32 --target=ppc-linux \
--disable-{binutils,gas,gold,gprof,ld}
The build failed with these errors in libctf:
In file included from ../../binutils-gdb/libctf/ctf-create.c:20:
../../binutils-gdb/libctf/ctf-create.c: In function 'ctf_add_encoded':
../../binutils-gdb/libctf/ctf-create.c:803:59: error: 'NBBY' undeclared (first use in this function)
dtd->dtd_data.ctt_size = clp2 (P2ROUNDUP (ep->cte_bits, NBBY) / NBBY);
^~~~
../../binutils-gdb/libctf/ctf-impl.h:254:42: note: in definition of macro 'P2ROUNDUP'
#define P2ROUNDUP(x, align) (-(-(x) & -(align)))
^~~~~
../../binutils-gdb/libctf/ctf-create.c:803:59: note: each undeclared identifier is reported only once for each function it appears in
dtd->dtd_data.ctt_size = clp2 (P2ROUNDUP (ep->cte_bits, NBBY) / NBBY);
^~~~
../../binutils-gdb/libctf/ctf-impl.h:254:42: note: in definition of macro 'P2ROUNDUP'
#define P2ROUNDUP(x, align) (-(-(x) & -(align)))
^~~~~
../../binutils-gdb/libctf/ctf-create.c: In function 'ctf_add_slice':
../../binutils-gdb/libctf/ctf-create.c:862:59: error: 'NBBY' undeclared (first use in this function)
dtd->dtd_data.ctt_size = clp2 (P2ROUNDUP (ep->cte_bits, NBBY) / NBBY);
^~~~
../../binutils-gdb/libctf/ctf-impl.h:254:42: note: in definition of macro 'P2ROUNDUP'
#define P2ROUNDUP(x, align) (-(-(x) & -(align)))
^~~~~
../../binutils-gdb/libctf/ctf-create.c: In function 'ctf_add_member_offset':
../../binutils-gdb/libctf/ctf-create.c:1341:21: error: 'NBBY' undeclared (first use in this function)
off += lsize * NBBY;
^~~~
../../binutils-gdb/libctf/ctf-create.c: In function 'ctf_add_type':
../../binutils-gdb/libctf/ctf-create.c:1822:16: warning: unknown conversion type character 'z' in format [-Wformat=]
ctf_dprintf ("Conflict for type %s against ID %lx: "
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../../binutils-gdb/libctf/ctf-create.c:1823:35: note: format string is defined here
"union size differs, old %zi, new %zi\n",
^
../../binutils-gdb/libctf/ctf-create.c:1822:16: warning: unknown conversion type character 'z' in format [-Wformat=]
ctf_dprintf ("Conflict for type %s against ID %lx: "
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../../binutils-gdb/libctf/ctf-create.c:1823:44: note: format string is defined here
"union size differs, old %zi, new %zi\n",
^
../../binutils-gdb/libctf/ctf-create.c:1822:16: warning: too many arguments for format [-Wformat-extra-args]
ctf_dprintf ("Conflict for type %s against ID %lx: "
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This patch fixes the actual errors in here. I did not try to fix the
printf warnings, though I think someone ought to.
Ok?
libctf/ChangeLog
2019-06-04 Tom Tromey <tromey@adacore.com>
* ctf-create.c (ctf_add_encoded, ctf_add_slice)
(ctf_add_member_offset): Use CHAR_BIT, not NBBY.
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(Not tested on any such platforms, since I don't have access to any at
the moment. Testing encouraged.)
libctf/
* configure.ac: Check for O_CLOEXEC.
* ctf-decls.h (O_CLOEXEC): Define (to 0), if need be.
* config.h.in: Regenerate.
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We cannot just look for any declaration of qsort_r, because some
operating systems have a qsort_r that has a different prototype
but which still has a pair of pointers in the right places (the last two
args are interchanged): so use AC_LINK_IFELSE to check for both
known variants of qsort_r(), and swap their args into a consistent order
in a suitable inline function. (The code for this is taken almost
unchanged from gnulib.)
(Now we are not using AC_LIBOBJ any more, we can use a better name for
the qsort_r replacement as well.)
libctf/
* qsort_r.c: Rename to...
* ctf-qsort_r.c: ... this.
(_quicksort): Define to ctf_qsort_r.
* ctf-decls.h (qsort_r): Remove.
(ctf_qsort_r): Add.
(struct ctf_qsort_arg): New, transport the real ARG and COMPAR.
(ctf_qsort_compar_thunk): Rearrange the arguments to COMPAR.
* Makefile.am (libctf_a_LIBADD): Remove.
(libctf_a_SOURCES): New, add ctf-qsort_r.c.
* ctf-archive.c (ctf_arc_write): Call ctf_qsort_r, not qsort_r.
* ctf-create.c (ctf_update): Likewise.
* configure.ac: Check for BSD versus GNU qsort_r signature.
* Makefile.in: Regenerate.
* config.h.in: Likewise.
* configure: Likewise.
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This is actually a free-before-initializing (i.e. a free of garbage).
libctf/
* ctf-dump.c (ctf_dump_funcs): Free in the right place.
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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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All machinery works as on ELF, except for automatic loading of ELF
string and symbol tables in the BFD-style open machinery.
* Makefile.def (dependencies): configure-libctf depends on all-bfd
and all its deps.
* Makefile.in: Regenerated.
libctf/
* configure.in: Check for bfd_section_from_elf_index.
* configure: Regenerate.
* config.h.in [HAVE_BFD_ELF]: Likewise.
* libctf/ctf_open_bfd (ctf_bfdopen_ctfsect): Use it.
abfd is potentially unused now.
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This ties libctf into the build system, and makes binutils depend on it
(used by the next commits).
* Makefile.def (host_modules): Add libctf.
* Makefile.def (dependencies): Likewise.
libctf depends on zlib, libiberty, and bfd.
* Makefile.in: Regenerated.
* configure.ac (host_libs): Add libctf.
* configure: Regenerated.
libctf/
* Makefile.am: New.
* Makefile.in: Regenerated.
* config.h.in: Likewise.
* aclocal.m4: Likewise.
* configure: Likewise.
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This introduces ctf_dump(), an iterator which returns a series of
strings, each representing a debugging dump of one item from a given
section in the CTF file. The items may be multiline: a callback is
provided to allow the caller to decorate each line as they desire before
the line is returned.
libctf/
* ctf-dump.c: New.
include/
* ctf-api.h (ctf_dump_decorate_f): New.
(ctf_dump_state_t): new.
(ctf_dump): New.
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This facility allows you to associate regions of type IDs with *labels*,
a labelled tiling of the type ID space. You can use these to define
CTF containers with distinct parents for distinct ranges of the ID
space, or to assist with parallelization of CTF processing, or for any
other purpose you can think of.
Notably absent from here (though declared in the API header) is any way
to define new labels: this will probably be introduced soon, as part of
the linker deduplication work. (One existed in the past, but was deeply
tied to the Solaris CTF file generator and had to be torn out.)
libctf/
* ctf-labels.c: New.
include/
* ctf-api.h (ctf_label_f): New.
(ctf_label_set): New.
(ctf_label_get): New.
(ctf_label_topmost): New.
(ctf_label_info): New.
(ctf_label_iter): New.
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This old Solaris standard allows callers to specify that they are
expecting one particular API and/or CTF file format from the library.
libctf/
* ctf-impl.h (_libctf_version): New declaration.
* ctf-subr.c (_libctf_version): Define it.
(ctf_version): New.
include/
* ctf-api.h (ctf_version): New.
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ctf_add_type() allows you to copy types, and all the types they depend
on, from one container to another (writable) container. This lets a
program maintaining multiple distinct containers (not in a parent-child
relationship) introduce types that depend on types in one container in
another writable one, by copying the necessary types.
libctf/
* ctf-create.c (enumcmp): New.
(enumadd): Likewise.
(membcmp): Likewise.
(membadd): Likewise.
(ctf_add_type): Likewise.
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These functions allow you to look up types given a name in a simple
subset of C declarator syntax (no function pointers), to look up the
types of variables given a name, and to look up the types of data
objects and the type signatures of functions given symbol table offsets.
(Despite its name, one function in this commit, ctf_lookup_symbol_name(),
is for the internal use of libctf only, and does not appear in any
public header files.)
libctf/
* ctf-lookup.c (isqualifier): New.
(ctf_lookup_by_name): Likewise.
(struct ctf_lookup_var_key): Likewise.
(ctf_lookup_var): Likewise.
(ctf_lookup_variable): Likewise.
(ctf_lookup_symbol_name): Likewise.
(ctf_lookup_by_symbol): Likewise.
(ctf_func_info): Likewise.
(ctf_func_args): Likewise.
include/
* ctf-api.h (ctf_func_info): New.
(ctf_func_args): Likewise.
(ctf_lookup_by_symbol): Likewise.
(ctf_lookup_by_symbol): Likewise.
(ctf_lookup_variable): Likewise.
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Finally we get to the functions used to actually look up and enumerate
properties of types in a container (names, sizes, members, what type a
pointer or cv-qual references, determination of whether two types are
assignment-compatible, etc).
With a very few exceptions these do not work for types newly added via
ctf_add_*(): they only work on types in read-only containers, or types
added before the most recent call to ctf_update().
This also adds support for lookup of "variables" (string -> type ID
mappings) and for generation of C type names corresponding to a type ID.
libctf/
* ctf-decl.c: New file.
* ctf-types.c: Likewise.
* ctf-impl.h: New declarations.
include/
* ctf-api.h (ctf_visit_f): New definition.
(ctf_member_f): Likewise.
(ctf_enum_f): Likewise.
(ctf_variable_f): Likewise.
(ctf_type_f): Likewise.
(ctf_type_isparent): Likewise.
(ctf_type_ischild): Likewise.
(ctf_type_resolve): Likewise.
(ctf_type_aname): Likewise.
(ctf_type_lname): Likewise.
(ctf_type_name): Likewise.
(ctf_type_sizee): Likewise.
(ctf_type_align): Likewise.
(ctf_type_kind): Likewise.
(ctf_type_reference): Likewise.
(ctf_type_pointer): Likewise.
(ctf_type_encoding): Likewise.
(ctf_type_visit): Likewise.
(ctf_type_cmp): Likewise.
(ctf_type_compat): Likewise.
(ctf_member_info): Likewise.
(ctf_array_info): Likewise.
(ctf_enum_name): Likewise.
(ctf_enum_value): Likewise.
(ctf_member_iter): Likewise.
(ctf_enum_iter): Likewise.
(ctf_type_iter): Likewise.
(ctf_variable_iter): 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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The CTF creation process looks roughly like (error handling elided):
int err;
ctf_file_t *foo = ctf_create (&err);
ctf_id_t type = ctf_add_THING (foo, ...);
ctf_update (foo);
ctf_*write (...);
Some ctf_add_THING functions accept other type IDs as arguments,
depending on the type: cv-quals, pointers, and structure and union
members all take other types as arguments. So do 'slices', which
let you take an existing integral type and recast it as a type
with a different bitness or offset within a byte, for bitfields.
One class of THING is not a type: "variables", which are mappings
of names (in the internal string table) to types. These are mostly
useful when encoding variables that do not appear in a symbol table
but which some external user has some other way to figure out the
address of at runtime (dynamic symbol lookup or querying a VM
interpreter or something).
You can snapshot the creation process at any point: rolling back to a
snapshot deletes all types and variables added since that point.
You can make arbitrary type queries on the CTF container during the
creation process, but you must call ctf_update() first, which
translates the growing dynamic container into a static one (this uses
the CTF opening machinery, added in a later commit), which is quite
expensive. This function must also be called after adding types
and before writing the container out.
Because addition of types involves looking up existing types, we add a
little of the type lookup machinery here, as well: only enough to
look up types in dynamic containers under construction.
libctf/
* ctf-create.c: New file.
* ctf-lookup.c: New file.
include/
* ctf-api.h (zlib.h): New include.
(ctf_sect_t): New.
(ctf_sect_names_t): Likewise.
(ctf_encoding_t): Likewise.
(ctf_membinfo_t): Likewise.
(ctf_arinfo_t): Likewise.
(ctf_funcinfo_t): Likewise.
(ctf_lblinfo_t): Likewise.
(ctf_snapshot_id_t): Likewise.
(CTF_FUNC_VARARG): Likewise.
(ctf_simple_open): Likewise.
(ctf_bufopen): Likewise.
(ctf_create): Likewise.
(ctf_add_array): Likewise.
(ctf_add_const): Likewise.
(ctf_add_enum_encoded): Likewise.
(ctf_add_enum): Likewise.
(ctf_add_float): Likewise.
(ctf_add_forward): Likewise.
(ctf_add_function): Likewise.
(ctf_add_integer): Likewise.
(ctf_add_slice): Likewise.
(ctf_add_pointer): Likewise.
(ctf_add_type): Likewise.
(ctf_add_typedef): Likewise.
(ctf_add_restrict): Likewise.
(ctf_add_struct): Likewise.
(ctf_add_union): Likewise.
(ctf_add_struct_sized): Likewise.
(ctf_add_union_sized): Likewise.
(ctf_add_volatile): Likewise.
(ctf_add_enumerator): Likewise.
(ctf_add_member): Likewise.
(ctf_add_member_offset): Likewise.
(ctf_add_member_encoded): Likewise.
(ctf_add_variable): Likewise.
(ctf_set_array): Likewise.
(ctf_update): Likewise.
(ctf_snapshot): Likewise.
(ctf_rollback): Likewise.
(ctf_discard): Likewise.
(ctf_write): Likewise.
(ctf_gzwrite): Likewise.
(ctf_compress_write): Likewise.
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We now enter a series of commits that are sufficiently tangled that
avoiding forward definitions is almost impossible: no attempt is made to
make individual commits compilable (which is why the build system does
not reference any of them yet): the only important thing is that they
should form something like conceptual groups.
But first, some definitions, including the core ctf_file_t itself. Uses
of these definitions will be introduced in later commits.
libctf/
* ctf-impl.h: New definitions and declarations for type creation
and lookup.
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libctf maintains two distinct hash ADTs, one (ctf_dynhash) for wrapping
dynamically-generated unknown-sized hashes during CTF file construction,
one (ctf_hash) for wrapping unchanging hashes whose size is known at
creation time for reading CTF files that were previously created.
In the binutils implementation, these are both fairly thin wrappers
around libiberty hashtab.
Unusually, this code is not kept synchronized with libdtrace-ctf,
due to its dependence on libiberty hashtab.
libctf/
* ctf-hash.c: New file.
* ctf-impl.h: New declarations.
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CTF functions return zero on success or an extended errno value which
can be translated into a string via the functions in this commit.
The errno numbers start at -CTF_BASE.
libctf/
* ctf-error.c: New file.
include/
* ctf-api.h (ctf_errno): New declaration.
(ctf_errmsg): Likewise.
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These utilities are a bit of a ragbag of small things needed by more
than one TU: list manipulation, ELF32->64 translators, routines to look
up strings in string tables, dynamically-allocated string appenders, and
routines to set the specialized errno values previously committed in
<ctf-api.h>.
We do still need to dig around in raw ELF symbol tables in places,
because libctf allows the caller to pass in the contents of string and
symbol sections without telling it where they come from, so we cannot
use BFD to get the symbols (BFD reasonably demands the entire file). So
extract minimal ELF definitions from glibc into a private header named
libctf/elf.h: later, we use those to get symbols. (The start-of-
copyright range on elf.h reflects this glibc heritage.)
libctf/
* ctf-util.c: New file.
* elf.h: Likewise.
* ctf-impl.h: Include it, and add declarations.
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The memory-allocation wrappers are simple things to allow malloc
interposition: they are only used inconsistently at present, usually
where malloc debugging was required in the past.
These provide a default implementation that is environment-variable
triggered (initialized on the first call to the libctf creation and
file-opening functions, the first functions people will use), and
a ctf_setdebug()/ctf_getdebug() pair that allows the caller to
explicitly turn debugging off and on. If ctf_setdebug() is called,
the automatic setting from an environment variable is skipped.
libctf/
* ctf-impl.h: New file.
* ctf-subr.c: New file.
include/
* ctf-api.h (ctf_setdebug): New.
(ctf_getdebug): Likewise.
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