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authorH.J. Lu <hjl.tools@gmail.com>2018-07-24 07:55:35 -0700
committerH.J. Lu <hjl.tools@gmail.com>2018-07-24 07:55:47 -0700
commite27f41ba2b6101be1a511905bff5502ffd23828b (patch)
treef7bd74631da12cc22e2dc5f6556a9ea2b45de5f0 /stdlib/ucontext.h
parent21526a507df8f1b2e37492193a754534d8938c0b (diff)
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Add <bits/indirect-return.h>
Add <bits/indirect-return.h> and include it in <ucontext.h>.
__INDIRECT_RETURN defined in <bits/indirect-return.h> indicates if
swapcontext requires special compiler treatment.  The default
__INDIRECT_RETURN is empty.

On x86, when shadow stack is enabled, __INDIRECT_RETURN is defined
with indirect_return attribute, which has been added to GCC 9, to
indicate that swapcontext returns via indirect branch.  Otherwise
__INDIRECT_RETURN is defined with returns_twice attribute.

When shadow stack is enabled, remove always_inline attribute from
prepare_test_buffer in string/tst-xbzero-opt.c to avoid:

tst-xbzero-opt.c: In function ‘prepare_test_buffer’:
tst-xbzero-opt.c:105:1: error: function ‘prepare_test_buffer’ can never be inlined because it uses setjmp
 prepare_test_buffer (unsigned char *buf)

when indirect_return attribute isn't available.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

	* bits/indirect-return.h: New file.
	* misc/sys/cdefs.h (__glibc_has_attribute): New.
	* sysdeps/x86/bits/indirect-return.h: Likewise.
	* stdlib/Makefile (headers): Add bits/indirect-return.h.
	* stdlib/ucontext.h: Include <bits/indirect-return.h>.
	(swapcontext): Add __INDIRECT_RETURN.
	* string/tst-xbzero-opt.c (ALWAYS_INLINE): New.
	(prepare_test_buffer): Use it.
Diffstat (limited to 'stdlib/ucontext.h')
-rw-r--r--stdlib/ucontext.h6
1 files changed, 5 insertions, 1 deletions
diff --git a/stdlib/ucontext.h b/stdlib/ucontext.h
index eec7611631..ec630038f6 100644
--- a/stdlib/ucontext.h
+++ b/stdlib/ucontext.h
@@ -22,6 +22,9 @@
 
 #include <features.h>
 
+/* Get definition of __INDIRECT_RETURN.  */
+#include <bits/indirect-return.h>
+
 /* Get machine dependent definition of data structures.  */
 #include <sys/ucontext.h>
 
@@ -36,7 +39,8 @@ extern int setcontext (const ucontext_t *__ucp) __THROWNL;
 /* Save current context in context variable pointed to by OUCP and set
    context from variable pointed to by UCP.  */
 extern int swapcontext (ucontext_t *__restrict __oucp,
-			const ucontext_t *__restrict __ucp) __THROWNL;
+			const ucontext_t *__restrict __ucp)
+  __THROWNL __INDIRECT_RETURN;
 
 /* Manipulate user context UCP to continue with calling functions FUNC
    and the ARGC-1 parameters following ARGC when the context is used