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i386: Port elf_machine_{load_address,dynamic} from x86-64

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This drops reliance on _GLOBAL_OFFSET_TABLE_[0] being the link-time
address of _DYNAMIC.

The code sequence length does not change.

Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
This commit is contained in:
Fangrui Song 2021-09-24 09:36:32 -07:00
parent 381b29616a
commit 91e92272ca
1 changed files with 10 additions and 17 deletions
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27
sysdeps/i386/dl-machine.h
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@ -34,27 +34,20 @@ elf_machine_matches_host (const Elf32_Ehdr *ehdr)
}
/* Return the link-time address of _DYNAMIC. Conveniently, this is the
first element of the GOT, a special entry that is never relocated. */
static inline Elf32_Addr __attribute__ ((unused, const))
elf_machine_dynamic (void)
{
/* This produces a GOTOFF reloc that resolves to zero at link time, so in
fact just loads from the GOT register directly. By doing it without
an asm we can let the compiler choose any register. */
extern const Elf32_Addr _GLOBAL_OFFSET_TABLE_[] attribute_hidden;
return _GLOBAL_OFFSET_TABLE_[0];
}
/* Return the run-time load address of the shared object. */
static inline Elf32_Addr __attribute__ ((unused))
elf_machine_load_address (void)
{
/* Compute the difference between the runtime address of _DYNAMIC as seen
by a GOTOFF reference, and the link-time address found in the special
unrelocated first GOT entry. */
extern Elf32_Dyn bygotoff[] asm ("_DYNAMIC") attribute_hidden;
return (Elf32_Addr) &bygotoff - elf_machine_dynamic ();
extern const Elf32_Ehdr __ehdr_start attribute_hidden;
return (Elf32_Addr) &__ehdr_start;
}
/* Return the link-time address of _DYNAMIC. */
static inline Elf32_Addr __attribute__ ((unused))
elf_machine_dynamic (void)
{
extern Elf32_Dyn _DYNAMIC[] attribute_hidden;
return (Elf32_Addr) _DYNAMIC - elf_machine_load_address ();
}
/* Set up the loaded object described by L so its unrelocated PLT