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elf: Use nocancel pread64() instead of lseek()+read()

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Transforms this, when linking in a shared object:

  openat(AT_FDCWD, "/lib64/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
  read(3, "\177ELF\2\1\1\3"..., 832) = 832
  lseek(3, 792, SEEK_SET)           = 792
  read(3, "\4\0\0\0\24\0\0\0"..., 68) = 68
  fstat(3, {st_mode=S_IFREG|0755, st_size=6699224, ...}) = 0
  lseek(3, 792, SEEK_SET)           = 792
  read(3, "\4\0\0\0\24\0\0\0"..., 68) = 68
  lseek(3, 864, SEEK_SET)           = 864
  read(3, "\4\0\0\0\20\0\0\0"..., 32) = 32

Into this:

  openat(AT_FDCWD, "/lib64/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
  read(3, "\177ELF\2\1\1\3"..., 832) = 832
  pread(3, "\4\0\0\0\24\0\0\0"..., 68, 792) = 68
  fstat(3, {st_mode=S_IFREG|0755, st_size=6699224, ...}) = 0
  pread(3, "\4\0\0\0\24\0\0\0"..., 68, 792) = 68
  pread(3, "\4\0\0\0\20\0\0\0"..., 32, 864) = 32

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
This commit is contained in:
Leandro Pereira 2019-10-02 12:48:17 -04:00 committed by Carlos O'Donell
parent fed33b0fb0
commit 95c1056962
2 changed files with 7 additions and 9 deletions
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13
elf/dl-load.c
View File

@ -1015,8 +1015,8 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
else
{
phdr = alloca (maplength);
__lseek (fd, header->e_phoff, SEEK_SET);
if ((size_t) __read_nocancel (fd, (void *) phdr, maplength) != maplength)
if ((size_t) __pread64_nocancel (fd, (void *) phdr, maplength,
header->e_phoff) != maplength)
{
errstring = N_("cannot read file data");
goto call_lose_errno;
@ -1664,9 +1664,8 @@ open_verify (const char *name, int fd,
else
{
phdr = alloca (maplength);
__lseek (fd, ehdr->e_phoff, SEEK_SET);
if ((size_t) __read_nocancel (fd, (void *) phdr, maplength)
!= maplength)
if ((size_t) __pread64_nocancel (fd, (void *) phdr, maplength,
ehdr->e_phoff) != maplength)
{
read_error:
errval = errno;
@ -1704,8 +1703,8 @@ open_verify (const char *name, int fd,
abi_note = abi_note_malloced;
}
__lseek (fd, ph->p_offset, SEEK_SET);
if (__read_nocancel (fd, (void *) abi_note, size) != size)
if (__pread64_nocancel (fd, (void *) abi_note, size,
ph->p_offset) != size)
{
free (abi_note_malloced);
goto read_error;

3
sysdeps/x86/dl-prop.h
View File

@ -167,8 +167,7 @@ _dl_process_pt_note (struct link_map *l, const ElfW(Phdr) *ph,
note_malloced = malloc (size);
note = note_malloced;
}
__lseek (fd, ph->p_offset, SEEK_SET);
if (__read_nocancel (fd, (void *) note, size) != size)
if (__pread64_nocancel (fd, (void *) note, size, ph->p_offset) != size)
{
if (note_malloced)
free (note_malloced);