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elf: Add _bfd_elf_m[un]map_section_contents

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Add _bfd_elf_mmap_section_contents and _bfd_elf_munmap_section_contents.
A backend must opt-in to use mmap.  It should replace

bfd_malloc_and_get_section -> _bfd_elf_mmap_section_contents
free			   -> _bfd_elf_munmap_section_contents

on section contents.

	* compress.c (bfd_get_full_section_contents): Don't allocate
	buffer if mmapped_p is true.
	* elf-bfd.h (elf_backend_data): Add use_mmap.
	(bfd_elf_section_data): Add contents_addr and contents_size.
	(_bfd_elf_mmap_section_contents): New.
	(_bfd_elf_munmap_section_contents): Likewise.
	* elf-eh-frame.c (_bfd_elf_parse_eh_frame): Replace
	bfd_malloc_and_get_section and free with
	_bfd_elf_mmap_section_contents and _bfd_elf_munmap_section_contents
	on section contents.
	* elf-sframe.c (_bfd_elf_parse_sframe): Likewise.
	* elf.c (_bfd_elf_make_section_from_shdr): Replace
	bfd_malloc_and_get_section and free with
	_bfd_elf_mmap_section_contents and _bfd_elf_munmap_section_contents
	on section contents.
	(_bfd_elf_print_private_bfd_data): Likewise.
	(_bfd_elf_mmap_section_contents): New.
	(_bfd_elf_munmap_section_contents): Likewise.
	* elf32-i386.c (elf_i386_scan_relocs): Replace
	bfd_malloc_and_get_section and free with
	_bfd_elf_mmap_section_contents and _bfd_elf_munmap_section_contents
	on section contents.
	* elf64-x86-64.c (elf_x86_64_scan_relocs): Likewise.
	(elf_x86_64_get_synthetic_symtab): Likewise.
	* elfcode.h (elf_checksum_contents): Likewise.
	* elflink.c (elf_link_add_object_symbols): Likewise.
	(bfd_elf_get_bfd_needed_list): Likewise.
	* elfxx-target.h (elf_backend_use_mmap): New.
	(elfNN_bed): Add elf_backend_use_mmap.
	* elfxx-x86.c (elf_x86_size_or_finish_relative_reloc): Replace
	bfd_malloc_and_get_section and free with
	_bfd_elf_mmap_section_contents and _bfd_elf_munmap_section_contents
	on section contents.
	(_bfd_x86_elf_get_synthetic_symtab): Replace free with
	_bfd_elf_munmap_section_contents.
	* elfxx-x86.h (elf_backend_use_mmap): New.
	* libbfd.c: Include "elf-bfd.h".
	(_bfd_generic_get_section_contents): Call bfd_mmap_local for
	mmapped_p.
	* opncls.c (_bfd_delete_bfd): Also munmap ELF section contents.
	* section.c (asection): Add mmapped_p.
	(BFD_FAKE_SECTION): Updated.
	(bfd_malloc_and_get_section): Add a sanity check for not
	mmapped_p.
	* bfd-in2.h: Regenerated.
This commit is contained in:
H.J. Lu 2024-03-01 06:14:20 -08:00
parent 9ba56acee5
commit 584b30e4b3
16 changed files with 212 additions and 39 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
bfd/bfd-in2.h
View File

@ -689,6 +689,9 @@ typedef struct bfd_section
/* Nonzero if this section uses RELA relocations, rather than REL. */
unsigned int use_rela_p:1;
/* Nonzero if this section contents are mmapped, rather than malloced. */
unsigned int mmapped_p:1;
/* Bits used by various backends. The generic code doesn't touch
these fields. */
@ -976,8 +979,8 @@ discarded_section (const asection *sec)
/* linker_mark, linker_has_input, gc_mark, decompress_status, */ \
0, 0, 1, 0, \
\
/* segment_mark, sec_info_type, use_rela_p, */ \
0, 0, 0, \
/* segment_mark, sec_info_type, use_rela_p, mmapped_p, */ \
0, 0, 0, 0, \
\
/* sec_flg0, sec_flg1, sec_flg2, sec_flg3, sec_flg4, sec_flg5, */ \
0, 0, 0, 0, 0, 0, \

2
bfd/compress.c
View File

@ -753,7 +753,7 @@ bfd_get_full_section_contents (bfd *abfd, sec_ptr sec, bfd_byte **ptr)
switch (compress_status)
{
case COMPRESS_SECTION_NONE:
if (p == NULL)
if (p == NULL && !sec->mmapped_p)
{
p = (bfd_byte *) bfd_malloc (allocsz);
if (p == NULL)

20
bfd/elf-bfd.h
View File

@ -1778,6 +1778,12 @@ struct elf_backend_data
/* True if the 64-bit Linux PRPSINFO structure's `pr_uid' and `pr_gid'
members use a 16-bit data type. */
unsigned linux_prpsinfo64_ugid16 : 1;
/* True if the backend can use mmap to map in all input section
contents. All bfd_malloc_and_get_section and free usages on
section contents must be replaced by _bfd_elf_mmap_section_contents
and _bfd_elf_munmap_section_contents. */
unsigned use_mmap : 1;
};
/* Information about reloc sections associated with a bfd_elf_section_data
@ -1859,6 +1865,15 @@ struct bfd_elf_section_data
/* Link from a text section to its .eh_frame_entry section. */
asection *eh_frame_entry;
/* If the mmapped_p flag is set, this points to the actual mmapped
address of contents. If it is set to NULL, contents isn't
mmapped. */
void *contents_addr;
/* If the mmapped_p flag is set, this is the actual mmapped size of
contents. */
size_t contents_size;
/* TRUE if the section has secondary reloc sections associated with it.
FIXME: In the future it might be better to change this into a list
of secondary reloc sections, making lookup easier and faster. */
@ -3127,6 +3142,11 @@ extern bool _bfd_elf_maybe_set_textrel
extern bool _bfd_elf_add_dynamic_tags
(bfd *, struct bfd_link_info *, bool);
extern bool _bfd_elf_mmap_section_contents
(bfd *abfd, asection *section, bfd_byte **buf);
extern void _bfd_elf_munmap_section_contents
(asection *, void *);
/* Large common section. */
extern asection _bfd_elf_large_com_section;

4
bfd/elf-eh-frame.c
View File

@ -618,7 +618,7 @@ _bfd_elf_parse_eh_frame (bfd *abfd, struct bfd_link_info *info,
/* Read the frame unwind information from abfd. */
REQUIRE (bfd_malloc_and_get_section (abfd, sec, &ehbuf));
REQUIRE (_bfd_elf_mmap_section_contents (abfd, sec, &ehbuf));
/* If .eh_frame section size doesn't fit into int, we cannot handle
it (it would need to use 64-bit .eh_frame format anyway). */
@ -1052,7 +1052,7 @@ _bfd_elf_parse_eh_frame (bfd *abfd, struct bfd_link_info *info,
hdr_info->u.dwarf.table = false;
free (sec_info);
success:
free (ehbuf);
_bfd_elf_munmap_section_contents (sec, ehbuf);
free (local_cies);
#undef REQUIRE
}

4
bfd/elf-sframe.c
View File

@ -208,7 +208,7 @@ _bfd_elf_parse_sframe (bfd *abfd,
}
/* Read the SFrame stack trace information from abfd. */
if (!bfd_malloc_and_get_section (abfd, sec, &sfbuf))
if (!_bfd_elf_mmap_section_contents (abfd, sec, &sfbuf))
goto fail_no_free;
/* Decode the buffer and keep decoded contents for later use.
@ -241,7 +241,7 @@ fail_no_free:
abfd, sec);
return false;
success:
free (sfbuf);
_bfd_elf_munmap_section_contents (sec, sfbuf);
return true;
}

87
bfd/elf.c
View File

@ -1111,12 +1111,12 @@ _bfd_elf_make_section_from_shdr (bfd *abfd,
{
bfd_byte *contents;
if (!bfd_malloc_and_get_section (abfd, newsect, &contents))
if (!_bfd_elf_mmap_section_contents (abfd, newsect, &contents))
return false;
elf_parse_notes (abfd, (char *) contents, hdr->sh_size,
hdr->sh_offset, hdr->sh_addralign);
free (contents);
_bfd_elf_munmap_section_contents (newsect, contents);
}
if ((newsect->flags & SEC_ALLOC) != 0)
@ -1686,7 +1686,7 @@ _bfd_elf_print_private_bfd_data (bfd *abfd, void *farg)
fprintf (f, _("\nDynamic Section:\n"));
if (!bfd_malloc_and_get_section (abfd, s, &dynbuf))
if (!_bfd_elf_mmap_section_contents (abfd, s, &dynbuf))
goto error_return;
elfsec = _bfd_elf_section_from_bfd_section (abfd, s);
@ -1808,7 +1808,7 @@ _bfd_elf_print_private_bfd_data (bfd *abfd, void *farg)
fprintf (f, "\n");
}
free (dynbuf);
_bfd_elf_munmap_section_contents (s, dynbuf);
dynbuf = NULL;
}
@ -1865,7 +1865,7 @@ _bfd_elf_print_private_bfd_data (bfd *abfd, void *farg)
return true;
error_return:
free (dynbuf);
_bfd_elf_munmap_section_contents (s, dynbuf);
return false;
}
@ -14370,3 +14370,80 @@ _bfd_elf_write_secondary_reloc_section (bfd *abfd, asection *sec)
return result;
}
/* Mmap in section contents. */
bool
_bfd_elf_mmap_section_contents (bfd *abfd, sec_ptr sec, bfd_byte **buf)
{
#ifdef USE_MMAP
const struct elf_backend_data *bed = get_elf_backend_data (abfd);
if (bed->use_mmap
&& sec->compress_status == COMPRESS_SECTION_NONE
&& (sec->flags & SEC_LINKER_CREATED) == 0)
{
/* Use mmap only if section size >= the minimum mmap section
size. */
size_t readsz = bfd_get_section_limit_octets (abfd, sec);
size_t allocsz = bfd_get_section_alloc_size (abfd, sec);
if (readsz == allocsz && readsz >= _bfd_minimum_mmap_size)
{
if (sec->contents != NULL)
{
if (!sec->mmapped_p)
abort ();
*buf = sec->contents;
return true;
}
if (sec->mmapped_p)
abort ();
sec->mmapped_p = 1;
}
}
#endif
*buf = NULL;
bool ret = bfd_get_full_section_contents (abfd, sec, buf);
if (ret && sec->mmapped_p)
*buf = sec->contents;
return ret;
}
/* Munmap section contents. */
void
_bfd_elf_munmap_section_contents (asection *sec ATTRIBUTE_UNUSED,
void *contents)
{
/* NB: Since _bfd_elf_munmap_section_contents is called like free,
CONTENTS may be NULL. */
if (contents == NULL)
return;
#ifdef USE_MMAP
if (sec->mmapped_p)
{
/* _bfd_elf_mmap_section_contents may return the previously
mapped section contents. Munmap the section contents only
if they haven't been cached. */
if (elf_section_data (sec)->this_hdr.contents == contents)
return;
/* When _bfd_elf_mmap_section_contents returns CONTENTS as
malloced, CONTENTS_ADDR is set to NULL. */
if (elf_section_data (sec)->contents_addr != NULL)
{
/* NB: CONTENTS_ADDR and CONTENTS_SIZE must be valid. */
if (munmap (elf_section_data (sec)->contents_addr,
elf_section_data (sec)->contents_size) != 0)
abort ();
sec->mmapped_p = 0;
sec->contents = NULL;
elf_section_data (sec)->contents_addr = NULL;
elf_section_data (sec)->contents_size = 0;
return;
}
}
#endif
free (contents);
}

6
bfd/elf32-i386.c
View File

@ -1499,7 +1499,7 @@ elf_i386_scan_relocs (bfd *abfd,
/* Get the section contents. */
if (elf_section_data (sec)->this_hdr.contents != NULL)
contents = elf_section_data (sec)->this_hdr.contents;
else if (!bfd_malloc_and_get_section (abfd, sec, &contents))
else if (!_bfd_elf_mmap_section_contents (abfd, sec, &contents))
{
sec->check_relocs_failed = 1;
return false;
@ -1933,7 +1933,7 @@ elf_i386_scan_relocs (bfd *abfd,
if (elf_section_data (sec)->this_hdr.contents != contents)
{
if (!converted && !_bfd_link_keep_memory (info))
free (contents);
_bfd_elf_munmap_section_contents (sec, contents);
else
{
/* Cache the section contents for elf_link_input_bfd if any
@ -1951,7 +1951,7 @@ elf_i386_scan_relocs (bfd *abfd,
error_return:
if (elf_section_data (sec)->this_hdr.contents != contents)
free (contents);
_bfd_elf_munmap_section_contents (sec, contents);
sec->check_relocs_failed = 1;
return false;
}

10
bfd/elf64-x86-64.c
View File

@ -2057,7 +2057,7 @@ elf_x86_64_scan_relocs (bfd *abfd, struct bfd_link_info *info,
/* Get the section contents. */
if (elf_section_data (sec)->this_hdr.contents != NULL)
contents = elf_section_data (sec)->this_hdr.contents;
else if (!bfd_malloc_and_get_section (abfd, sec, &contents))
else if (!_bfd_elf_mmap_section_contents (abfd, sec, &contents))
{
sec->check_relocs_failed = 1;
return false;
@ -2591,7 +2591,7 @@ elf_x86_64_scan_relocs (bfd *abfd, struct bfd_link_info *info,
if (elf_section_data (sec)->this_hdr.contents != contents)
{
if (!converted && !_bfd_link_keep_memory (info))
free (contents);
_bfd_elf_munmap_section_contents (sec, contents);
else
{
/* Cache the section contents for elf_link_input_bfd if any
@ -2609,7 +2609,7 @@ elf_x86_64_scan_relocs (bfd *abfd, struct bfd_link_info *info,
error_return:
if (elf_section_data (sec)->this_hdr.contents != contents)
free (contents);
_bfd_elf_munmap_section_contents (sec, contents);
sec->check_relocs_failed = 1;
return false;
}
@ -5273,7 +5273,7 @@ elf_x86_64_get_synthetic_symtab (bfd *abfd,
continue;
/* Get the PLT section contents. */
if (!bfd_malloc_and_get_section (abfd, plt, &plt_contents))
if (!_bfd_elf_mmap_section_contents (abfd, plt, &plt_contents))
break;
/* Check what kind of PLT it is. */
@ -5366,7 +5366,7 @@ elf_x86_64_get_synthetic_symtab (bfd *abfd,
if (plt_type == plt_unknown)
{
free (plt_contents);
_bfd_elf_munmap_section_contents (plt, plt_contents);
continue;
}

7
bfd/elfcode.h
View File

@ -1195,6 +1195,7 @@ elf_checksum_contents (bfd *abfd,
Elf_Internal_Shdr i_shdr;
Elf_External_Shdr x_shdr;
bfd_byte *contents, *free_contents;
asection *sec = NULL;
i_shdr = *i_shdrp[count];
i_shdr.sh_offset = 0;
@ -1210,8 +1211,6 @@ elf_checksum_contents (bfd *abfd,
contents = i_shdr.contents;
if (contents == NULL)
{
asection *sec;
sec = bfd_section_from_elf_index (abfd, count);
if (sec != NULL)
{
@ -1220,7 +1219,7 @@ elf_checksum_contents (bfd *abfd,
{
/* Force rereading from file. */
sec->flags &= ~SEC_IN_MEMORY;
if (!bfd_malloc_and_get_section (abfd, sec, &free_contents))
if (!_bfd_elf_mmap_section_contents (abfd, sec, &free_contents))
continue;
contents = free_contents;
}
@ -1229,7 +1228,7 @@ elf_checksum_contents (bfd *abfd,
if (contents != NULL)
{
(*process) (contents, i_shdr.sh_size, arg);
free (free_contents);
_bfd_elf_munmap_section_contents (sec, free_contents);
}
}

12
bfd/elflink.c
View File

@ -4426,10 +4426,10 @@ elf_link_add_object_symbols (bfd *abfd, struct bfd_link_info *info)
unsigned int elfsec;
unsigned long shlink;
if (!bfd_malloc_and_get_section (abfd, s, &dynbuf))
if (!_bfd_elf_mmap_section_contents (abfd, s, &dynbuf))
{
error_free_dyn:
free (dynbuf);
_bfd_elf_munmap_section_contents (s, dynbuf);
goto error_return;
}
@ -4535,7 +4535,7 @@ elf_link_add_object_symbols (bfd *abfd, struct bfd_link_info *info)
elf_tdata (abfd)->is_pie = (dyn.d_un.d_val & DF_1_PIE) != 0;
}
free (dynbuf);
_bfd_elf_munmap_section_contents (s, dynbuf);
}
/* DT_RUNPATH overrides DT_RPATH. Do _NOT_ bfd_release, as that
@ -8282,7 +8282,7 @@ bfd_elf_get_bfd_needed_list (bfd *abfd,
if (s == NULL || s->size == 0 || (s->flags & SEC_HAS_CONTENTS) == 0)
return true;
if (!bfd_malloc_and_get_section (abfd, s, &dynbuf))
if (!_bfd_elf_mmap_section_contents (abfd, s, &dynbuf))
goto error_return;
elfsec = _bfd_elf_section_from_bfd_section (abfd, s);
@ -8328,12 +8328,12 @@ bfd_elf_get_bfd_needed_list (bfd *abfd,
}
}
free (dynbuf);
_bfd_elf_munmap_section_contents (s, dynbuf);
return true;
error_return:
free (dynbuf);
_bfd_elf_munmap_section_contents (s, dynbuf);
return false;
}

6
bfd/elfxx-target.h
View File

@ -148,6 +148,9 @@
#ifndef elf_backend_strtab_flags
#define elf_backend_strtab_flags 0
#endif
#ifndef elf_backend_use_mmap
#define elf_backend_use_mmap false
#endif
#define bfd_elfNN_bfd_debug_info_start _bfd_void_bfd
#define bfd_elfNN_bfd_debug_info_end _bfd_void_bfd
@ -979,7 +982,8 @@ static const struct elf_backend_data elfNN_bed =
elf_backend_extern_protected_data,
elf_backend_always_renumber_dynsyms,
elf_backend_linux_prpsinfo32_ugid16,
elf_backend_linux_prpsinfo64_ugid16
elf_backend_linux_prpsinfo64_ugid16,
elf_backend_use_mmap
};
/* Forward declaration for use when initialising alternative_target field. */

4
bfd/elfxx-x86.c
View File

@ -1566,7 +1566,7 @@ elf_x86_size_or_finish_relative_reloc
= elf_section_data (sec)->this_hdr.contents;
else
{
if (!bfd_malloc_and_get_section (sec->owner,
if (!_bfd_elf_mmap_section_contents (sec->owner,
sec,
&contents))
info->callbacks->einfo
@ -3789,7 +3789,7 @@ _bfd_x86_elf_get_synthetic_symtab (bfd *abfd,
count = n;
for (j = 0; plts[j].name != NULL; j++)
free (plts[j].contents);
_bfd_elf_munmap_section_contents (plts[j].sec, plts[j].contents);
free (dynrelbuf);

1
bfd/elfxx-x86.h
View File

@ -960,6 +960,7 @@ extern void _bfd_x86_elf_link_report_relative_reloc
_bfd_elf_x86_size_relative_relocs
#define elf_backend_finish_relative_relocs \
_bfd_elf_x86_finish_relative_relocs
#define elf_backend_use_mmap true
#define ELF_P_ALIGN ELF_MINPAGESIZE

59
bfd/libbfd.c
View File

@ -21,6 +21,7 @@
#include "sysdep.h"
#include "bfd.h"
#include "elf-bfd.h"
#include "libbfd.h"
#include "objalloc.h"
@ -1196,6 +1197,19 @@ _bfd_generic_get_section_contents (bfd *abfd,
return false;
}
#ifdef USE_MMAP
if (section->mmapped_p
&& (section->contents != NULL || location != NULL))
{
_bfd_error_handler
/* xgettext:c-format */
(_("%pB: mapped section %pA has non-NULL buffer"),
abfd, section);
bfd_set_error (bfd_error_invalid_operation);
return false;
}
#endif
sz = bfd_get_section_limit_octets (abfd, section);
if (offset + count < count
|| offset + count > sz
@ -1208,8 +1222,49 @@ _bfd_generic_get_section_contents (bfd *abfd,
return false;
}
if (bfd_seek (abfd, section->filepos + offset, SEEK_SET) != 0
|| bfd_read (location, count, abfd) != count)
if (bfd_seek (abfd, section->filepos + offset, SEEK_SET) != 0)
return false;
#ifdef USE_MMAP
if (section->mmapped_p)
{
if (location != 0
|| bfd_get_flavour (abfd) != bfd_target_elf_flavour)
abort ();
int prot = ((section->reloc_count == 0)
? PROT_READ : PROT_READ | PROT_WRITE);
location = bfd_mmap_local
(abfd, count, prot, &elf_section_data (section)->contents_addr,
&elf_section_data (section)->contents_size);
if (location == NULL)
return false;
/* Check for iovec not supporting mmap. */
if (location != MAP_FAILED)
{
section->contents = location;
return true;
}
/* Malloc the buffer and call bfd_read. */
location = (bfd_byte *) bfd_malloc (count);
if (location == NULL)
{
if (bfd_get_error () == bfd_error_no_memory)
_bfd_error_handler
/* xgettext:c-format */
(_("error: %pB(%pA) is too large (%#" PRIx64 " bytes)"),
abfd, section, (uint64_t) count);
return false;
}
section->contents = location;
}
#endif
if (bfd_read (location, count, abfd) != count)
return false;
return true;

9
bfd/opncls.c
View File

@ -164,6 +164,15 @@ static void
_bfd_delete_bfd (bfd *abfd)
{
#ifdef USE_MMAP
if (bfd_get_flavour (abfd) == bfd_target_elf_flavour)
{
asection *sec;
for (sec = abfd->sections; sec != NULL; sec = sec->next)
if (sec->mmapped_p)
munmap (elf_section_data (sec)->contents_addr,
elf_section_data (sec)->contents_size);
}
struct bfd_mmapped *mmapped, *next;
for (mmapped = abfd->mmapped; mmapped != NULL; mmapped = next)
{

9
bfd/section.c
View File

@ -422,6 +422,9 @@ CODE_FRAGMENT
. {* Nonzero if this section uses RELA relocations, rather than REL. *}
. unsigned int use_rela_p:1;
.
. {* Nonzero if this section contents are mmapped, rather than malloced. *}
. unsigned int mmapped_p:1;
.
. {* Bits used by various backends. The generic code doesn't touch
. these fields. *}
.
@ -711,8 +714,8 @@ EXTERNAL
. {* linker_mark, linker_has_input, gc_mark, decompress_status, *} \
. 0, 0, 1, 0, \
. \
. {* segment_mark, sec_info_type, use_rela_p, *} \
. 0, 0, 0, \
. {* segment_mark, sec_info_type, use_rela_p, mmapped_p, *} \
. 0, 0, 0, 0, \
. \
. {* sec_flg0, sec_flg1, sec_flg2, sec_flg3, sec_flg4, sec_flg5, *} \
. 0, 0, 0, 0, 0, 0, \
@ -1625,6 +1628,8 @@ DESCRIPTION
bool
bfd_malloc_and_get_section (bfd *abfd, sec_ptr sec, bfd_byte **buf)
{
if (sec->mmapped_p)
abort ();
*buf = NULL;
return bfd_get_full_section_contents (abfd, sec, buf);
}