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libsanitizer: Mark REAL(swapcontext) with indirect_return attribute on x86

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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.

From-SVN: r263009
This commit is contained in:
H.J. Lu 2018-07-26 14:48:55 +00:00 committed by H.J. Lu
parent 49ba258864
commit c83b4b8242
3 changed files with 21 additions and 0 deletions
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8
libsanitizer/ChangeLog
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@ -1,3 +1,11 @@
2018-07-25 H.J. Lu <hongjiu.lu@intel.com>
PR target/86560
* asan/asan_interceptors.cc (swapcontext) Cherry-pick
compiler-rt revision 337603.
* sanitizer_common/sanitizer_internal_defs.h (__has_attribute):
Likewise.
2018-07-05 Jakub Jelinek <jakub@redhat.com> 2018-07-05 Jakub Jelinek <jakub@redhat.com>
Revert Revert

8
libsanitizer/asan/asan_interceptors.cc
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@ -267,7 +267,15 @@ INTERCEPTOR(int, swapcontext, struct ucontext_t *oucp,
uptr stack, ssize; uptr stack, ssize;
ReadContextStack(ucp, &stack, &ssize); ReadContextStack(ucp, &stack, &ssize);
ClearShadowMemoryForContextStack(stack, ssize); ClearShadowMemoryForContextStack(stack, ssize);
#if __has_attribute(__indirect_return__) && \
(defined(__x86_64__) || defined(__i386__))
int (*real_swapcontext)(struct ucontext_t *, struct ucontext_t *)
__attribute__((__indirect_return__))
= REAL(swapcontext);
int res = real_swapcontext(oucp, ucp);
#else
int res = REAL(swapcontext)(oucp, ucp); int res = REAL(swapcontext)(oucp, ucp);
#endif
// swapcontext technically does not return, but program may swap context to // swapcontext technically does not return, but program may swap context to
// "oucp" later, that would look as if swapcontext() returned 0. // "oucp" later, that would look as if swapcontext() returned 0.
// We need to clear shadow for ucp once again, as it may be in arbitrary // We need to clear shadow for ucp once again, as it may be in arbitrary

5
libsanitizer/sanitizer_common/sanitizer_internal_defs.h
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@ -104,6 +104,11 @@
# define __has_feature(x) 0 # define __has_feature(x) 0
#endif #endif
// Older GCCs do not understand __has_attribute.
#if !defined(__has_attribute)
# define __has_attribute(x) 0
#endif
// For portability reasons we do not include stddef.h, stdint.h or any other // For portability reasons we do not include stddef.h, stdint.h or any other
// system header, but we do need some basic types that are not defined // system header, but we do need some basic types that are not defined
// in a portable way by the language itself. // in a portable way by the language itself.