[PATCH 09/15] De-PLTize __stack_chk_fail internal calls within libc.so.

[Nix <nix at esperi dot org dot uk>]

From: Adhemerval Zanella <adhemerval.zanella@linaro.org>

We use the same assembler-macro trick we use to de-PLTize
compiler-generated libcalls to memcpy and memset to redirect
__stack_chk_fail to __stack_chk_fail_local.

v5: New.
v6: Only do it within the shared library: with __stack_chk_fail_local
    in libc_pic.a now we don't need to worry about calls from inside
    other routines in libc_nonshared.a any more.
v8: Merge #ifdef blocks.
v10: Use STACK_PROTECTOR_LEVEL to avoid renaming in files where
     stack-protection is suppressed.

	* sysdeps/generic/symbol-hacks.h [STACK_PROTECTOR_LEVEL &&
	STACK_PROTECTOR_LEVEL > 0] (__stack_chk_fail): Add internal alias.
---
 sysdeps/generic/symbol-hacks.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/sysdeps/generic/symbol-hacks.h b/sysdeps/generic/symbol-hacks.h
index ce576c9..d614c09 100644
--- a/sysdeps/generic/symbol-hacks.h
+++ b/sysdeps/generic/symbol-hacks.h
@@ -4,4 +4,16 @@
 asm ("memmove = __GI_memmove");
 asm ("memset = __GI_memset");
 asm ("memcpy = __GI_memcpy");
+
+/* Some targets do not use __stack_chk_fail_local.  In libc.so,
+   redirect __stack_chk_fail to a hidden reference
+   __stack_chk_fail_local, to avoid the PLT reference.
+   __stack_chk_fail itself is a global symbol, exported from libc.so,
+   and cannot be made hidden.  */
+
+# if IS_IN (libc) && defined SHARED && \
+  defined STACK_PROTECTOR_LEVEL && STACK_PROTECTOR_LEVEL > 0
+asm (".hidden __stack_chk_fail_local\n"
+     "__stack_chk_fail = __stack_chk_fail_local");
+# endif
 #endif
-- 
2.10.1.208.gbec66bc