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elf: work around a gcc bug in elf_get_dynamic_info

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Since commit 2f056e8a5d
"aarch64: define PI_STATIC_AND_HIDDEN",
building glibc with gcc-8 on aarch64 fails with

/BLD/elf/librtld.os: in function `elf_get_dynamic_info':
/SRC/elf/get-dynamic-info.h:70:(.text+0xad8): relocation truncated to
 fit: R_AARCH64_ADR_PREL_PG_HI21 against symbol `_rtld_local' defined
 in .data section in /BLD/elf/librtld.os

This is a gcc bug:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98618
The bug is fixed on gcc-10 and not yet backported. gcc-9 is affected,
but the issue happens to not trigger in glibc, gcc-8 and older seems
to miscompile rtld.os.

Rewriting the affected code in elf_get_dynamic_info seems to make the
issue go away on <= gcc-9.

The change makes the logic a bit clearer too (by separating the index
computation and array update) and drops an older gcc workaround (since
gcc 4.6 is no longer supported).

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
This commit is contained in:
Szabolcs Nagy 2021-01-11 09:04:53 +00:00
parent 2ef23b5205
commit 86a4d3fa7d
1 changed files with 18 additions and 23 deletions
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41
elf/get-dynamic-info.h
View File

@ -30,8 +30,6 @@ auto
inline void __attribute__ ((unused, always_inline))
elf_get_dynamic_info (struct link_map *l, ElfW(Dyn) *temp)
{
ElfW(Dyn) *dyn = l->l_ld;
ElfW(Dyn) **info;
#if __ELF_NATIVE_CLASS == 32
typedef Elf32_Word d_tag_utype;
#elif __ELF_NATIVE_CLASS == 64
@ -39,39 +37,36 @@ elf_get_dynamic_info (struct link_map *l, ElfW(Dyn) *temp)
#endif
#if !defined RTLD_BOOTSTRAP && !defined STATIC_PIE_BOOTSTRAP
if (dyn == NULL)
if (l->l_ld == NULL)
return;
#endif
info = l->l_info;
ElfW(Dyn) **info = l->l_info;
while (dyn->d_tag != DT_NULL)
for (ElfW(Dyn) *dyn = l->l_ld; dyn->d_tag != DT_NULL; dyn++)
{
d_tag_utype i;
if ((d_tag_utype) dyn->d_tag < DT_NUM)
info[dyn->d_tag] = dyn;
i = dyn->d_tag;
else if (dyn->d_tag >= DT_LOPROC
&& dyn->d_tag < DT_LOPROC + DT_THISPROCNUM)
{
/* This does not violate the array bounds of l->l_info, but
gcc 4.6 on sparc somehow does not see this. */
DIAG_PUSH_NEEDS_COMMENT;
DIAG_IGNORE_NEEDS_COMMENT (4.6,
"-Warray-bounds");
info[dyn->d_tag - DT_LOPROC + DT_NUM] = dyn;
DIAG_POP_NEEDS_COMMENT;
}
i = dyn->d_tag - DT_LOPROC + DT_NUM;
else if ((d_tag_utype) DT_VERSIONTAGIDX (dyn->d_tag) < DT_VERSIONTAGNUM)
info[VERSYMIDX (dyn->d_tag)] = dyn;
i = VERSYMIDX (dyn->d_tag);
else if ((d_tag_utype) DT_EXTRATAGIDX (dyn->d_tag) < DT_EXTRANUM)
info[DT_EXTRATAGIDX (dyn->d_tag) + DT_NUM + DT_THISPROCNUM
+ DT_VERSIONTAGNUM] = dyn;
i = DT_EXTRATAGIDX (dyn->d_tag) + DT_NUM + DT_THISPROCNUM
+ DT_VERSIONTAGNUM;
else if ((d_tag_utype) DT_VALTAGIDX (dyn->d_tag) < DT_VALNUM)
info[DT_VALTAGIDX (dyn->d_tag) + DT_NUM + DT_THISPROCNUM
+ DT_VERSIONTAGNUM + DT_EXTRANUM] = dyn;
i = DT_VALTAGIDX (dyn->d_tag) + DT_NUM + DT_THISPROCNUM
+ DT_VERSIONTAGNUM + DT_EXTRANUM;
else if ((d_tag_utype) DT_ADDRTAGIDX (dyn->d_tag) < DT_ADDRNUM)
info[DT_ADDRTAGIDX (dyn->d_tag) + DT_NUM + DT_THISPROCNUM
+ DT_VERSIONTAGNUM + DT_EXTRANUM + DT_VALNUM] = dyn;
++dyn;
i = DT_ADDRTAGIDX (dyn->d_tag) + DT_NUM + DT_THISPROCNUM
+ DT_VERSIONTAGNUM + DT_EXTRANUM + DT_VALNUM;
else
continue;
info[i] = dyn;
}
#define DL_RO_DYN_TEMP_CNT 8