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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.
This commit is contained in:
H.J. Lu
parent
21526a507d
commit
e27f41ba2b
11
ChangeLog
11
ChangeLog
@ -1,3 +1,14 @@
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2018-07-24 H.J. Lu <hongjiu.lu@intel.com>
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* bits/indirect-return.h: New file.
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* misc/sys/cdefs.h (__glibc_has_attribute): New.
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* sysdeps/x86/bits/indirect-return.h: Likewise.
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* stdlib/Makefile (headers): Add bits/indirect-return.h.
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* stdlib/ucontext.h: Include <bits/indirect-return.h>.
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(swapcontext): Add __INDIRECT_RETURN.
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* string/tst-xbzero-opt.c (ALWAYS_INLINE): New.
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(prepare_test_buffer): Use it.
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2018-07-24 Andreas Schwab <schwab@suse.de>
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[BZ #23448]
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25
bits/indirect-return.h
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25
bits/indirect-return.h
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@ -0,0 +1,25 @@
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/* Definition of __INDIRECT_RETURN. Generic version.
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Copyright (C) 2018 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#ifndef _UCONTEXT_H
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# error "Never include <bits/indirect-return.h> directly; use <ucontext.h> instead."
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#endif
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/* __INDIRECT_RETURN is used on swapcontext to indicate if it requires
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special compiler treatment. */
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#define __INDIRECT_RETURN
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@ -406,6 +406,12 @@
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# define __glibc_likely(cond) (cond)
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#endif
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#ifdef __has_attribute
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# define __glibc_has_attribute(attr) __has_attribute (attr)
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#else
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# define __glibc_has_attribute(attr) 0
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#endif
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#if (!defined _Noreturn \
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&& (defined __STDC_VERSION__ ? __STDC_VERSION__ : 0) < 201112 \
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&& !__GNUC_PREREQ (4,7))
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@ -26,7 +26,7 @@ headers := stdlib.h bits/stdlib.h bits/stdlib-ldbl.h bits/stdlib-float.h \
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monetary.h bits/monetary-ldbl.h \
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inttypes.h stdint.h bits/wordsize.h \
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errno.h sys/errno.h bits/errno.h bits/types/error_t.h \
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ucontext.h sys/ucontext.h \
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ucontext.h sys/ucontext.h bits/indirect-return.h \
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alloca.h fmtmsg.h \
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bits/stdlib-bsearch.h sys/random.h bits/stdint-intn.h \
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bits/stdint-uintn.h
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@ -22,6 +22,9 @@
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#include <features.h>
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/* Get definition of __INDIRECT_RETURN. */
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#include <bits/indirect-return.h>
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/* Get machine dependent definition of data structures. */
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#include <sys/ucontext.h>
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@ -36,7 +39,8 @@ extern int setcontext (const ucontext_t *__ucp) __THROWNL;
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/* Save current context in context variable pointed to by OUCP and set
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context from variable pointed to by UCP. */
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extern int swapcontext (ucontext_t *__restrict __oucp,
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const ucontext_t *__restrict __ucp) __THROWNL;
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const ucontext_t *__restrict __ucp)
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__THROWNL __INDIRECT_RETURN;
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/* Manipulate user context UCP to continue with calling functions FUNC
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and the ARGC-1 parameters following ARGC when the context is used
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@ -100,7 +100,15 @@ static ucontext_t uc_main, uc_co;
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/* Always check the test buffer immediately after filling it; this
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makes externally visible side effects depend on the buffer existing
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and having been filled in. */
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static inline __attribute__ ((always_inline)) void
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#if defined __CET__ && !__glibc_has_attribute (__indirect_return__)
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/* Note: swapcontext returns via indirect branch when SHSTK is enabled.
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Without indirect_return attribute, swapcontext is marked with
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returns_twice attribute, which prevents always_inline to work. */
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# define ALWAYS_INLINE
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#else
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# define ALWAYS_INLINE __attribute__ ((always_inline))
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#endif
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static inline ALWAYS_INLINE void
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prepare_test_buffer (unsigned char *buf)
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{
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for (unsigned int i = 0; i < PATTERN_REPS; i++)
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37
sysdeps/x86/bits/indirect-return.h
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37
sysdeps/x86/bits/indirect-return.h
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@ -0,0 +1,37 @@
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/* Definition of __INDIRECT_RETURN. x86 version.
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Copyright (C) 2018 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#ifndef _UCONTEXT_H
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# error "Never include <bits/indirect-return.h> directly; use <ucontext.h> instead."
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#endif
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/* On x86, swapcontext returns via indirect branch when the shadow stack
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is enabled. Define __INDIRECT_RETURN to indicate whether swapcontext
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returns via indirect branch. */
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#if defined __CET__ && (__CET__ & 2) != 0
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# if __glibc_has_attribute (__indirect_return__)
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# define __INDIRECT_RETURN __attribute__ ((__indirect_return__))
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# else
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/* Newer compilers provide the indirect_return attribute, but without
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it we can use returns_twice to affect the optimizer in the same
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way and avoid unsafe optimizations. */
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# define __INDIRECT_RETURN __attribute__ ((__returns_twice__))
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# endif
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#else
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# define __INDIRECT_RETURN
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#endif
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