r263009 - in /trunk/libsanitizer: ChangeLog asa...

[hjl@gcc.gnu.org]

Author: hjl
Date: Thu Jul 26 14:48:55 2018
New Revision: 263009

URL: https://gcc.gnu.org/viewcvs?rev=263009&root=gcc&view=rev
Log:
libsanitizer: Mark REAL(swapcontext) with indirect_return attribute on x86

Cherry-pick compiler-rt revision 337603:

When shadow stack from Intel CET is enabled, the first instruction of all
indirect branch targets must be a special instruction, ENDBR.

lib/asan/asan_interceptors.cc has

...
  int res = REAL(swapcontext)(oucp, ucp);
...

REAL(swapcontext) is a function pointer to swapcontext in libc.  Since
swapcontext may return via indirect branch on x86 when shadow stack is
enabled, as in this case,

int res = REAL(swapcontext)(oucp, ucp);
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^  This function may be
returned via an indirect branch.

Here compiler must insert ENDBR after call, like

call *bar(%rip)
endbr64

I opened an LLVM bug:

https://bugs.llvm.org/show_bug.cgi?id=38207

to add the indirect_return attribute so that it can be used to inform
compiler to insert ENDBR after REAL(swapcontext) call.  We mark
REAL(swapcontext) with the indirect_return attribute if it is available.

This fixed:

https://bugs.llvm.org/show_bug.cgi?id=38249

Reviewed By: eugenis

Differential Revision: https://reviews.llvm.org/D49608

	PR target/86560
	* asan/asan_interceptors.cc (swapcontext) Cherry-pick
	compiler-rt revision 337603.
	* sanitizer_common/sanitizer_internal_defs.h (__has_attribute):
	Likewise.

Modified:
    trunk/libsanitizer/ChangeLog
    trunk/libsanitizer/asan/asan_interceptors.cc
    trunk/libsanitizer/sanitizer_common/sanitizer_internal_defs.h