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binutils-gdb/bfd/format.c
Joseph Myers 64bfc2584c Fix BFD format matching for x86_64-w64-mingw32 -m32 LTO. 
In <https://sourceware.org/ml/binutils/2015-12/msg00190.html> (commit
4a07dc8135), Kwok fixed a problem with
the template used for a dummy BFD for an IR file for LTO on MinGW,
where the input and output formats are not the same.

A problem, however, remains in the case of linking for
x86_64-w64-mingw32 -m32, where LTO linking reports an ambiguity
between the pe-i386 and pei-i386 formats.  An object (pe-i386) with
plugin data is being tested by the linker to see what formats match.
The default format initially set by the linker when
bfd_check_format_matches is called is pei-i386 (as that's the output
format from the linker script), which does not match, so the function
goes on to the loop over possible BFD vectors.  The pe-i386 vector
matches, as it should.  One other vector matches: the plugin vector.

bfd_check_format_matches tests a vector for matching by temporarily
modifying the BFD object to use that vector then using
_bfd_check_format on it.  So the BFD object is temporarily using
plugin_vec.  _bfd_check_format ends up using bfd_plugin_object_p which
uses plugin_object_p from ld which uses plugin_get_ir_dummy_bfd which
succeeds, having created a BFD based on link_info.output_bfd (because
srctemplate is the BFD temporarily using plugin_vec, even after Kwok's
patch link_info.output_bfd is all that's available to base the dummy
BFD on).  So we end up with a match from the plugin vector which uses
the pei-i386 vector even though the pei-i386 vector itself does not
match the input object.  (In the i686-mingw32 case, as opposed to this
multilib case, pe-i386 is the default BFD target, which would
short-circuit that logic.)

There are two cases of the linker handling inputs with a plugin: they
may be inputs that are also accepted by some non-plugin BFD format, as
here, or they may be a format that would not be recognized at all, as
with some tests in the ld testsuite.  In the former case, there is no
need for BFD to accept the objects using the plugin vector, as the
linker has its own logic to allow plugins to claim objects accepted by
some other BFD vector.  Thus, this patch arranges for the plugin
vector to have the lowest match priority, and for the priority from
that vector to be used in the relevant case (the attempted match to
the plugin vector results in TEMP pointing to the pei-i386 vector).

Tested for GCC and Binutils testsuites for x86_64-pc-linux-gnu, as
well as verifying that it fixes the observed LTO issue for
x86_64-w64-mingw32.

	* plugin.c (plugin_vec): Set match priority to 255.
	* format.c (bfd_check_format_matches) [BFD_SUPPORTS_PLUGINS]: When
	matching against the plugin vector, take priority from there not
	from TEMP.
2016-02-16 00:27:11 +00:00

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/* Generic BFD support for file formats.
Copyright (C) 1990-2016 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
bfd_boolean 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.
*/
bfd_boolean
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;
struct bfd_hash_table section_htab;
};
/* 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 bfd_boolean
bfd_preserve_save (bfd *abfd, struct bfd_preserve *preserve)
{
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_htab = abfd->section_htab;
preserve->marker = bfd_alloc (abfd, 1);
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)
{
abfd->tdata.any = NULL;
abfd->arch_info = &bfd_default_arch_struct;
abfd->flags &= BFD_FLAGS_SAVED;
bfd_section_list_clear (abfd);
}
/* Restores bfd state saved by bfd_preserve_save. */
static void
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_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;
}
/* 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)
{
/* 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;
}
/*
FUNCTION
bfd_check_format_matches
SYNOPSIS
bfd_boolean 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.
*/
bfd_boolean
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;
struct bfd_preserve preserve;
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)
{
bfd_size_type 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.marker = NULL;
/* 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;
right_targ = BFD_SEND_FMT (abfd, _bfd_check_format, (abfd));
if (right_targ)
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++)
{
const bfd_target *temp;
/* Don't check the default target twice. */
if (*target == &binary_vec
|| (!abfd->target_defaulted && *target == save_targ)
|| (*target)->match_priority > best_match)
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);
/* Change BFD's target temporarily. */
abfd->xvec = *target;
if (bfd_seek (abfd, (file_ptr) 0, SEEK_SET) != 0)
goto err_ret;
/* If _bfd_check_format neglects to set bfd_error, assume
bfd_error_wrong_format. We didn't used to even pay any
attention to bfd_error, so I suspect that some
_bfd_check_format might have this problem. */
bfd_set_error (bfd_error_wrong_format);
temp = BFD_SEND_FMT (abfd, _bfd_check_format, (abfd));
if (temp)
{
int match_priority = temp->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
match_targ = temp;
if (preserve.marker != NULL)
bfd_preserve_finish (abfd, &preserve);
if (abfd->format != bfd_archive
|| (bfd_has_map (abfd)
&& bfd_get_error () != bfd_error_wrong_object_format))
{
/* This format checks out as ok! */
right_targ = temp;
/* 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 (temp == bfd_default_vector[0])
goto ok_ret;
if (matching_vector)
matching_vector[match_count] = temp;
match_count++;
if (match_priority < best_match)
{
best_match = match_priority;
best_count = 0;
}
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 (!bfd_preserve_save (abfd, &preserve))
goto err_ret;
}
else if (bfd_get_error () != bfd_error_wrong_format)
goto err_ret;
}
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.marker != NULL)
bfd_preserve_restore (abfd, &preserve);
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). */
if (match_targ != right_targ)
{
bfd_reinit (abfd);
if (bfd_seek (abfd, (file_ptr) 0, SEEK_SET) != 0)
goto err_ret;
match_targ = BFD_SEND_FMT (abfd, _bfd_check_format, (abfd));
BFD_ASSERT (match_targ != 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;
if (matching_vector)
free (matching_vector);
/* File position has moved, BTW. */
return TRUE;
}
if (match_count == 0)
{
err_unrecog:
bfd_set_error (bfd_error_file_not_recognized);
err_ret:
abfd->xvec = save_targ;
abfd->format = bfd_unknown;
if (matching_vector)
free (matching_vector);
if (preserve.marker != NULL)
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;
}
}
return FALSE;
}
/*
FUNCTION
bfd_set_format
SYNOPSIS
bfd_boolean 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.
*/
bfd_boolean
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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