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x86_64: Simplify elf_machine_{load_address,dynamic}

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and drop reliance on _GLOBAL_OFFSET_TABLE_[0] being the link-time
address of _DYNAMIC. &__ehdr_start is a better way to get the load address.

Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
This commit is contained in:
Fangrui Song 2021-08-17 10:45:57 -07:00
parent 33c50ef428
commit b37b75d269
1 changed files with 9 additions and 16 deletions
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25
sysdeps/x86_64/dl-machine.h
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@ -35,27 +35,20 @@ elf_machine_matches_host (const ElfW(Ehdr) *ehdr)
}
/* Return the link-time address of _DYNAMIC. Conveniently, this is the
first element of the GOT. This must be inlined in a function which
uses global data. */
static inline ElfW(Addr) __attribute__ ((unused))
elf_machine_dynamic (void)
{
/* This produces an IP-relative reloc which is resolved at link time. */
extern const ElfW(Addr) _GLOBAL_OFFSET_TABLE_[] attribute_hidden;
return _GLOBAL_OFFSET_TABLE_[0];
}
/* Return the run-time load address of the shared object. */
static inline ElfW(Addr) __attribute__ ((unused))
elf_machine_load_address (void)
{
/* Compute the difference between the runtime address of _DYNAMIC as seen
by an IP-relative reference, and the link-time address found in the
special unrelocated first GOT entry. */
extern const ElfW(Ehdr) __ehdr_start attribute_hidden;
return (ElfW(Addr)) &__ehdr_start;
}
/* Return the link-time address of _DYNAMIC. */
static inline ElfW(Addr) __attribute__ ((unused))
elf_machine_dynamic (void)
{
extern ElfW(Dyn) _DYNAMIC[] attribute_hidden;
return (ElfW(Addr)) &_DYNAMIC - elf_machine_dynamic ();
return (ElfW(Addr)) _DYNAMIC - elf_machine_load_address ();
}
/* Set up the loaded object described by L so its unrelocated PLT