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aarch64: redefine RETURN_ADDRESS to strip PAC

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RETURN_ADDRESS is used at several places in glibc to mean a valid
code address of the call site, but with pac-ret it may contain a
pointer authentication code (PAC), so its definition is adjusted.

This is gcc PR target/94891: __builtin_return_address should not
expose signed pointers to user code where it can cause ABI issues.
In glibc RETURN_ADDRESS is only changed if it is built with pac-ret.
There is no detection for the specific gcc issue because it is
hard to test and the additional xpac does not cause problems.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
This commit is contained in:
Szabolcs Nagy 2020-04-15 17:40:45 +01:00
parent c94767712b
commit d174ec248d
1 changed files with 7 additions and 0 deletions
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7
sysdeps/aarch64/sysdep.h
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@ -44,6 +44,13 @@ strip_pac (void *p)
asm ("hint 7 // xpaclri" : "+r"(ra));
return ra;
}
/* This is needed when glibc is built with -mbranch-protection=pac-ret
with a gcc that is affected by PR target/94891. */
# if HAVE_AARCH64_PAC_RET
# undef RETURN_ADDRESS
# define RETURN_ADDRESS(n) strip_pac (__builtin_return_address (n))
# endif
#endif
#ifdef __ASSEMBLER__