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authorSzabolcs Nagy <szabolcs.nagy@arm.com>2020-04-15 17:40:45 +0100
committerSzabolcs Nagy <szabolcs.nagy@arm.com>2020-07-08 15:02:38 +0100
commitd174ec248d5b6bba3842f425f036495b682c313f (patch)
tree0e0c44233e52934f582c06498464cd91ccd46d0a /sysdeps/aarch64
parentc94767712b06fd37e82d23f86d4d6e1c93948d8a (diff)
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aarch64: redefine RETURN_ADDRESS to strip PAC
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>
Diffstat (limited to 'sysdeps/aarch64')
-rw-r--r--sysdeps/aarch64/sysdep.h7
1 files changed, 7 insertions, 0 deletions
diff --git a/sysdeps/aarch64/sysdep.h b/sysdeps/aarch64/sysdep.h
index f442506952..ae269146e3 100644
--- a/sysdeps/aarch64/sysdep.h
+++ b/sysdeps/aarch64/sysdep.h
@@ -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__