Date: Wed, 1 Jun 2005 10:24:16 -0700 From: Richard Henderson <rth@twiddle.net> To: freebsd-alpha@FreeBSD.org Subject: reloc_non_plt_obj buggy Message-ID: <20050601172416.GA4197@twiddle.net>
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>From src/libexec/rtld-elf/alpha/reloc.c:
---------------------
#define load64(p) ({ \
Elf_Addr __res; \
__asm__("ldq_u %0,%1" : "=r"(__res) : "m"(*(p))); \
__res; })
#define store64(p, v) \
__asm__("stq_u %1,%0" : "=m"(*(p)) : "r"(v))
---------------------
case R_ALPHA_REFQUAD: {
const Elf_Sym *def;
const Obj_Entry *defobj;
def = find_symdef(ELF_R_SYM(rela->r_info), obj,
&defobj, false, cache);
if (def == NULL)
return -1;
store64(where,
(Elf_Addr) (defobj->relocbase + def->st_value) +
load64(where) + rela->r_addend);
}
---------------------
Someone wasn't very clear on what ldq_u/stq_u actually does.
You're not actually modifying the unaligned address, you're
modifying (address & ~7), and corrupting the dwarf2 data in
the process.
You need to use
struct ualong {
Elf_Addr x __attribute__((packed));
};
#define load64(p) (((struct ualong *)(p))->x)
#define store64(p,v) (((struct ualong *)(p))->x = (v))
r~
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