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binutils-gdb/bfd/format.c
Alan Modra 5aa0f10c42 The problem with warning in elf_object_p 
elfcode.h can emit three warnings in elf_object_p for various things,
"section extending past end of file", "corrupt string table index",
and "program header with invalid alignment".  The problem with doing
this is that the warning can be emitted for multiple possible targets
as each one is tried.  I was looking at a fuzzer testcase that had an
object file with 6144 program headers, 5316 of which had invalid
alignment.  It would be bad enough to get 5316 messages all the same,
but this object was contained in an archive and resulted in 4975776
repeats.

Some trimming can be done by not warning if the bfd is already marked
read_only, as is done for the "section extending past end of file"
warning, but that still results in an unacceptable number of
warnings for object files in archives.  Besides that, it is just wrong
to warn about a problem detected by a target elf_object_p other than
the one that actually matches.  At some point we might have more
target specific warnings.

So what to do?  One obvious solution is to remove the warnings.
Another is to poke any warning strings into the target xvec, emitting
them if that xvec is the final one chosen.  This also has the benefit
of solving the archive problem.  A warning when recursing into
_bfd_check_format for the first element of the archive (to find the
correct target for the archive) will still be on the xvec at the point
that target is chosen for the archive.  However, target xvecs are
read-only.  Thus the need for per_xvec_warn to logically extend
bfd_target with a writable field.  I've made per_xvec_warn one larger
than bfd_target_vector to provide one place for user code that makes
private copies of target xvecs.

	* elfcode.h (elf_swap_shdr_in, elf_object_p): Stash potential
	warnings in _bfd_per_xvec_warn location.
	* format.c (clear_warnmsg): New function.
	(bfd_check_format_matches): Call clear_warnmsg before trying
	a new xvec.  Print warnings for the successful non-archive
	match.
	* targets.c: Include libiberty.h.
	(_bfd_target_vector_entries): Use ARRAY_SIZE.
	(per_xvec_warn): New.
	(_bfd_per_xvec_warn): New function.
	* Makefile.am (LIBBFD_H_FILES): Add targets.c.
	* Makefile.in: Regenerate.
	* libbfd.h: Regenerate.
2022-09-24 11:28:55 +09:30

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/* Generic BFD support for file formats.
Copyright (C) 1990-2022 Free Software Foundation, Inc.
Written by Cygnus Support.
This file is part of BFD, the Binary File Descriptor library.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
MA 02110-1301, USA. */
/*
SECTION
File formats
A format is a BFD concept of high level file contents type. The
formats supported by BFD are:
o <<bfd_object>>
The BFD may contain data, symbols, relocations and debug info.
o <<bfd_archive>>
The BFD contains other BFDs and an optional index.
o <<bfd_core>>
The BFD contains the result of an executable core dump.
SUBSECTION
File format functions
*/
#include "sysdep.h"
#include "bfd.h"
#include "libbfd.h"
/* IMPORT from targets.c. */
extern const size_t _bfd_target_vector_entries;
/*
FUNCTION
bfd_check_format
SYNOPSIS
bool bfd_check_format (bfd *abfd, bfd_format format);
DESCRIPTION
Verify if the file attached to the BFD @var{abfd} is compatible
with the format @var{format} (i.e., one of <<bfd_object>>,
<<bfd_archive>> or <<bfd_core>>).
If the BFD has been set to a specific target before the
call, only the named target and format combination is
checked. If the target has not been set, or has been set to
<<default>>, then all the known target backends is
interrogated to determine a match. If the default target
matches, it is used. If not, exactly one target must recognize
the file, or an error results.
The function returns <<TRUE>> on success, otherwise <<FALSE>>
with one of the following error codes:
o <<bfd_error_invalid_operation>> -
if <<format>> is not one of <<bfd_object>>, <<bfd_archive>> or
<<bfd_core>>.
o <<bfd_error_system_call>> -
if an error occured during a read - even some file mismatches
can cause bfd_error_system_calls.
o <<file_not_recognised>> -
none of the backends recognised the file format.
o <<bfd_error_file_ambiguously_recognized>> -
more than one backend recognised the file format.
*/
bool
bfd_check_format (bfd *abfd, bfd_format format)
{
return bfd_check_format_matches (abfd, format, NULL);
}
struct bfd_preserve
{
void *marker;
void *tdata;
flagword flags;
const struct bfd_arch_info *arch_info;
struct bfd_section *sections;
struct bfd_section *section_last;
unsigned int section_count;
unsigned int section_id;
struct bfd_hash_table section_htab;
const struct bfd_build_id *build_id;
bfd_cleanup cleanup;
};
/* When testing an object for compatibility with a particular target
back-end, the back-end object_p function needs to set up certain
fields in the bfd on successfully recognizing the object. This
typically happens in a piecemeal fashion, with failures possible at
many points. On failure, the bfd is supposed to be restored to its
initial state, which is virtually impossible. However, restoring a
subset of the bfd state works in practice. This function stores
the subset. */
static bool
bfd_preserve_save (bfd *abfd, struct bfd_preserve *preserve,
bfd_cleanup cleanup)
{
preserve->tdata = abfd->tdata.any;
preserve->arch_info = abfd->arch_info;
preserve->flags = abfd->flags;
preserve->sections = abfd->sections;
preserve->section_last = abfd->section_last;
preserve->section_count = abfd->section_count;
preserve->section_id = _bfd_section_id;
preserve->section_htab = abfd->section_htab;
preserve->marker = bfd_alloc (abfd, 1);
preserve->build_id = abfd->build_id;
preserve->cleanup = cleanup;
if (preserve->marker == NULL)
return false;
return bfd_hash_table_init (&abfd->section_htab, bfd_section_hash_newfunc,
sizeof (struct section_hash_entry));
}
/* Clear out a subset of BFD state. */
static void
bfd_reinit (bfd *abfd, unsigned int section_id, bfd_cleanup cleanup)
{
_bfd_section_id = section_id;
if (cleanup)
cleanup (abfd);
abfd->tdata.any = NULL;
abfd->arch_info = &bfd_default_arch_struct;
abfd->flags &= BFD_FLAGS_SAVED;
abfd->build_id = NULL;
bfd_section_list_clear (abfd);
}
/* Restores bfd state saved by bfd_preserve_save. */
static bfd_cleanup
bfd_preserve_restore (bfd *abfd, struct bfd_preserve *preserve)
{
bfd_hash_table_free (&abfd->section_htab);
abfd->tdata.any = preserve->tdata;
abfd->arch_info = preserve->arch_info;
abfd->flags = preserve->flags;
abfd->section_htab = preserve->section_htab;
abfd->sections = preserve->sections;
abfd->section_last = preserve->section_last;
abfd->section_count = preserve->section_count;
_bfd_section_id = preserve->section_id;
abfd->build_id = preserve->build_id;
/* bfd_release frees all memory more recently bfd_alloc'd than
its arg, as well as its arg. */
bfd_release (abfd, preserve->marker);
preserve->marker = NULL;
return preserve->cleanup;
}
/* Called when the bfd state saved by bfd_preserve_save is no longer
needed. */
static void
bfd_preserve_finish (bfd *abfd ATTRIBUTE_UNUSED, struct bfd_preserve *preserve)
{
if (preserve->cleanup)
{
/* Run the cleanup, assuming that all it will need is the
tdata at the time the cleanup was returned. */
void *tdata = abfd->tdata.any;
abfd->tdata.any = preserve->tdata;
preserve->cleanup (abfd);
abfd->tdata.any = tdata;
}
/* It would be nice to be able to free more memory here, eg. old
tdata, but that's not possible since these blocks are sitting
inside bfd_alloc'd memory. The section hash is on a separate
objalloc. */
bfd_hash_table_free (&preserve->section_htab);
preserve->marker = NULL;
}
static void
clear_warnmsg (const bfd_target *targ)
{
const char **warn = _bfd_per_xvec_warn (targ);
*warn = NULL;
}
/*
FUNCTION
bfd_check_format_matches
SYNOPSIS
bool bfd_check_format_matches
(bfd *abfd, bfd_format format, char ***matching);
DESCRIPTION
Like <<bfd_check_format>>, except when it returns FALSE with
<<bfd_errno>> set to <<bfd_error_file_ambiguously_recognized>>. In that
case, if @var{matching} is not NULL, it will be filled in with
a NULL-terminated list of the names of the formats that matched,
allocated with <<malloc>>.
Then the user may choose a format and try again.
When done with the list that @var{matching} points to, the caller
should free it.
*/
bool
bfd_check_format_matches (bfd *abfd, bfd_format format, char ***matching)
{
extern const bfd_target binary_vec;
#if BFD_SUPPORTS_PLUGINS
extern const bfd_target plugin_vec;
#endif
const bfd_target * const *target;
const bfd_target **matching_vector = NULL;
const bfd_target *save_targ, *right_targ, *ar_right_targ, *match_targ;
int match_count, best_count, best_match;
int ar_match_index;
unsigned int initial_section_id = _bfd_section_id;
struct bfd_preserve preserve, preserve_match;
bfd_cleanup cleanup = NULL;
if (matching != NULL)
*matching = NULL;
if (!bfd_read_p (abfd)
|| (unsigned int) abfd->format >= (unsigned int) bfd_type_end)
{
bfd_set_error (bfd_error_invalid_operation);
return false;
}
if (abfd->format != bfd_unknown)
return abfd->format == format;
if (matching != NULL || *bfd_associated_vector != NULL)
{
size_t amt;
amt = sizeof (*matching_vector) * 2 * _bfd_target_vector_entries;
matching_vector = (const bfd_target **) bfd_malloc (amt);
if (!matching_vector)
return false;
}
/* Presume the answer is yes. */
abfd->format = format;
save_targ = abfd->xvec;
preserve_match.marker = NULL;
if (!bfd_preserve_save (abfd, &preserve, NULL))
goto err_ret;
/* If the target type was explicitly specified, just check that target. */
if (!abfd->target_defaulted)
{
if (bfd_seek (abfd, (file_ptr) 0, SEEK_SET) != 0) /* rewind! */
goto err_ret;
clear_warnmsg (abfd->xvec);
cleanup = BFD_SEND_FMT (abfd, _bfd_check_format, (abfd));
if (cleanup)
goto ok_ret;
/* For a long time the code has dropped through to check all
targets if the specified target was wrong. I don't know why,
and I'm reluctant to change it. However, in the case of an
archive, it can cause problems. If the specified target does
not permit archives (e.g., the binary target), then we should
not allow some other target to recognize it as an archive, but
should instead allow the specified target to recognize it as an
object. When I first made this change, it broke the PE target,
because the specified pei-i386 target did not recognize the
actual pe-i386 archive. Since there may be other problems of
this sort, I changed this test to check only for the binary
target. */
if (format == bfd_archive && save_targ == &binary_vec)
goto err_unrecog;
}
/* Since the target type was defaulted, check them all in the hope
that one will be uniquely recognized. */
right_targ = NULL;
ar_right_targ = NULL;
match_targ = NULL;
best_match = 256;
best_count = 0;
match_count = 0;
ar_match_index = _bfd_target_vector_entries;
for (target = bfd_target_vector; *target != NULL; target++)
{
void **high_water;
/* The binary target matches anything, so don't return it when
searching. Don't match the plugin target if we have another
alternative since we want to properly set the input format
before allowing a plugin to claim the file. Also, don't
check the default target twice. */
if (*target == &binary_vec
#if BFD_SUPPORTS_PLUGINS
|| (match_count != 0 && *target == &plugin_vec)
#endif
|| (!abfd->target_defaulted && *target == save_targ))
continue;
/* If we already tried a match, the bfd is modified and may
have sections attached, which will confuse the next
_bfd_check_format call. */
bfd_reinit (abfd, initial_section_id, cleanup);
/* Free bfd_alloc memory too. If we have matched and preserved
a target then the high water mark is that much higher. */
if (preserve_match.marker)
high_water = &preserve_match.marker;
else
high_water = &preserve.marker;
bfd_release (abfd, *high_water);
*high_water = bfd_alloc (abfd, 1);
/* Change BFD's target temporarily. */
abfd->xvec = *target;
if (bfd_seek (abfd, (file_ptr) 0, SEEK_SET) != 0)
goto err_ret;
clear_warnmsg (abfd->xvec);
cleanup = BFD_SEND_FMT (abfd, _bfd_check_format, (abfd));
if (cleanup)
{
int match_priority = abfd->xvec->match_priority;
#if BFD_SUPPORTS_PLUGINS
/* If this object can be handled by a plugin, give that the
lowest priority; objects both handled by a plugin and
with an underlying object format will be claimed
separately by the plugin. */
if (*target == &plugin_vec)
match_priority = (*target)->match_priority;
#endif
if (abfd->format != bfd_archive
|| (bfd_has_map (abfd)
&& bfd_get_error () != bfd_error_wrong_object_format))
{
/* If this is the default target, accept it, even if
other targets might match. People who want those
other targets have to set the GNUTARGET variable. */
if (abfd->xvec == bfd_default_vector[0])
goto ok_ret;
if (matching_vector)
matching_vector[match_count] = abfd->xvec;
match_count++;
if (match_priority < best_match)
{
best_match = match_priority;
best_count = 0;
}
if (match_priority <= best_match)
{
/* This format checks out as ok! */
right_targ = abfd->xvec;
best_count++;
}
}
else
{
/* An archive with no armap or objects of the wrong
type. We want this target to match if we get no
better matches. */
if (ar_right_targ != bfd_default_vector[0])
ar_right_targ = *target;
if (matching_vector)
matching_vector[ar_match_index] = *target;
ar_match_index++;
}
if (preserve_match.marker == NULL)
{
match_targ = abfd->xvec;
if (!bfd_preserve_save (abfd, &preserve_match, cleanup))
goto err_ret;
cleanup = NULL;
}
}
}
if (best_count == 1)
match_count = 1;
if (match_count == 0)
{
/* Try partial matches. */
right_targ = ar_right_targ;
if (right_targ == bfd_default_vector[0])
{
match_count = 1;
}
else
{
match_count = ar_match_index - _bfd_target_vector_entries;
if (matching_vector && match_count > 1)
memcpy (matching_vector,
matching_vector + _bfd_target_vector_entries,
sizeof (*matching_vector) * match_count);
}
}
/* We have more than one equally good match. If any of the best
matches is a target in config.bfd targ_defvec or targ_selvecs,
choose it. */
if (match_count > 1)
{
const bfd_target * const *assoc = bfd_associated_vector;
while ((right_targ = *assoc++) != NULL)
{
int i = match_count;
while (--i >= 0)
if (matching_vector[i] == right_targ
&& right_targ->match_priority <= best_match)
break;
if (i >= 0)
{
match_count = 1;
break;
}
}
}
/* We still have more than one equally good match, and at least some
of the targets support match priority. Choose the first of the
best matches. */
if (matching_vector && match_count > 1 && best_count != match_count)
{
int i;
for (i = 0; i < match_count; i++)
{
right_targ = matching_vector[i];
if (right_targ->match_priority <= best_match)
break;
}
match_count = 1;
}
/* There is way too much undoing of half-known state here. We
really shouldn't iterate on live bfd's. Note that saving the
whole bfd and restoring it would be even worse; the first thing
you notice is that the cached bfd file position gets out of sync. */
if (preserve_match.marker != NULL)
cleanup = bfd_preserve_restore (abfd, &preserve_match);
if (match_count == 1)
{
abfd->xvec = right_targ;
/* If we come out of the loop knowing that the last target that
matched is the one we want, then ABFD should still be in a usable
state (except possibly for XVEC). This is not just an
optimisation. In the case of plugins a match against the
plugin target can result in the bfd being changed such that
it no longer matches the plugin target, nor will it match
RIGHT_TARG again. */
if (match_targ != right_targ)
{
bfd_reinit (abfd, initial_section_id, cleanup);
bfd_release (abfd, preserve.marker);
if (bfd_seek (abfd, (file_ptr) 0, SEEK_SET) != 0)
goto err_ret;
cleanup = BFD_SEND_FMT (abfd, _bfd_check_format, (abfd));
BFD_ASSERT (cleanup != NULL);
}
ok_ret:
/* If the file was opened for update, then `output_has_begun'
some time ago when the file was created. Do not recompute
sections sizes or alignments in _bfd_set_section_contents.
We can not set this flag until after checking the format,
because it will interfere with creation of BFD sections. */
if (abfd->direction == both_direction)
abfd->output_has_begun = true;
free (matching_vector);
if (preserve_match.marker != NULL)
bfd_preserve_finish (abfd, &preserve_match);
bfd_preserve_finish (abfd, &preserve);
if (!abfd->my_archive)
{
const char **warn = _bfd_per_xvec_warn (abfd->xvec);
if (*warn)
_bfd_error_handler (*warn, abfd);
}
/* File position has moved, BTW. */
return true;
}
if (match_count == 0)
{
err_unrecog:
bfd_set_error (bfd_error_file_not_recognized);
err_ret:
if (cleanup)
cleanup (abfd);
abfd->xvec = save_targ;
abfd->format = bfd_unknown;
free (matching_vector);
if (preserve_match.marker != NULL)
bfd_preserve_finish (abfd, &preserve_match);
bfd_preserve_restore (abfd, &preserve);
return false;
}
/* Restore original target type and format. */
abfd->xvec = save_targ;
abfd->format = bfd_unknown;
bfd_set_error (bfd_error_file_ambiguously_recognized);
if (matching)
{
*matching = (char **) matching_vector;
matching_vector[match_count] = NULL;
/* Return target names. This is a little nasty. Maybe we
should do another bfd_malloc? */
while (--match_count >= 0)
{
const char *name = matching_vector[match_count]->name;
*(const char **) &matching_vector[match_count] = name;
}
}
else
free (matching_vector);
if (cleanup)
cleanup (abfd);
if (preserve_match.marker != NULL)
bfd_preserve_finish (abfd, &preserve_match);
bfd_preserve_restore (abfd, &preserve);
return false;
}
/*
FUNCTION
bfd_set_format
SYNOPSIS
bool bfd_set_format (bfd *abfd, bfd_format format);
DESCRIPTION
This function sets the file format of the BFD @var{abfd} to the
format @var{format}. If the target set in the BFD does not
support the format requested, the format is invalid, or the BFD
is not open for writing, then an error occurs.
*/
bool
bfd_set_format (bfd *abfd, bfd_format format)
{
if (bfd_read_p (abfd)
|| (unsigned int) abfd->format >= (unsigned int) bfd_type_end)
{
bfd_set_error (bfd_error_invalid_operation);
return false;
}
if (abfd->format != bfd_unknown)
return abfd->format == format;
/* Presume the answer is yes. */
abfd->format = format;
if (!BFD_SEND_FMT (abfd, _bfd_set_format, (abfd)))
{
abfd->format = bfd_unknown;
return false;
}
return true;
}
/*
FUNCTION
bfd_format_string
SYNOPSIS
const char *bfd_format_string (bfd_format format);
DESCRIPTION
Return a pointer to a const string
<<invalid>>, <<object>>, <<archive>>, <<core>>, or <<unknown>>,
depending upon the value of @var{format}.
*/
const char *
bfd_format_string (bfd_format format)
{
if (((int) format < (int) bfd_unknown)
|| ((int) format >= (int) bfd_type_end))
return "invalid";
switch (format)
{
case bfd_object:
return "object"; /* Linker/assembler/compiler output. */
case bfd_archive:
return "archive"; /* Object archive file. */
case bfd_core:
return "core"; /* Core dump. */
default:
return "unknown";
}
}
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