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author | H.J. Lu <hjl.tools@gmail.com> | 2018-05-02 06:17:20 -0700 |
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committer | H.J. Lu <hjl.tools@gmail.com> | 2018-05-02 06:17:41 -0700 |
commit | d6cc1829aa31b6fb060f24dffd28aa6705cdd33a (patch) | |
tree | 197e7983f66d43765505f94a5a29d254d27f6d02 /sysdeps/x86/nptl | |
parent | b109fbfe4dd2ca77656157ddaded773e0da630a2 (diff) | |
download | glibc-d6cc1829aa31b6fb060f24dffd28aa6705cdd33a.tar.gz glibc-d6cc1829aa31b6fb060f24dffd28aa6705cdd33a.tar.xz glibc-d6cc1829aa31b6fb060f24dffd28aa6705cdd33a.zip |
x86: Use pad in pthread_unwind_buf to preserve shadow stack register
The pad array in struct pthread_unwind_buf is used by setjmp to save shadow stack register. We assert that size of struct pthread_unwind_buf is no less than offset of shadow stack pointer + shadow stack pointer size. Since functions, like LIBC_START_MAIN, START_THREAD_DEFN as well as these with thread cancellation, call setjmp, but never return after __libc_unwind_longjmp, __libc_unwind_longjmp, which is defined as __libc_longjmp on x86, doesn't need to restore shadow stack register. __libc_longjmp, which is a private interface for thread cancellation implementation in libpthread, is changed to call __longjmp_cancel, instead of __longjmp. __longjmp_cancel is a new internal function in libc, which is similar to __longjmp, but doesn't restore shadow stack register. The compatibility longjmp and siglongjmp in libpthread.so are changed to call __libc_siglongjmp, instead of __libc_longjmp, so that they will restore shadow stack register. Tested with build-many-glibcs.py. Signed-off-by: H.J. Lu <hjl.tools@gmail.com> Reviewed-by: Carlos O'Donell <carlos@redhat.com> * nptl/pthread_create.c (START_THREAD_DEFN): Clear previous handlers after setjmp. * setjmp/longjmp.c (__libc_longjmp): Don't define alias if defined. * sysdeps/unix/sysv/linux/x86/setjmpP.h: Include <libc-pointer-arith.h>. (_JUMP_BUF_SIGSET_BITS_PER_WORD): New. (_JUMP_BUF_SIGSET_NSIG): Changed to 96. (_JUMP_BUF_SIGSET_NWORDS): Changed to use ALIGN_UP and _JUMP_BUF_SIGSET_BITS_PER_WORD. * sysdeps/x86/Makefile (sysdep_routines): Add __longjmp_cancel. * sysdeps/x86/__longjmp_cancel.S: New file. * sysdeps/x86/longjmp.c: Likewise. * sysdeps/x86/nptl/pt-longjmp.c: Likewise.
Diffstat (limited to 'sysdeps/x86/nptl')
-rw-r--r-- | sysdeps/x86/nptl/pt-longjmp.c | 71 |
1 files changed, 71 insertions, 0 deletions
diff --git a/sysdeps/x86/nptl/pt-longjmp.c b/sysdeps/x86/nptl/pt-longjmp.c new file mode 100644 index 0000000000..6165c7d4a7 --- /dev/null +++ b/sysdeps/x86/nptl/pt-longjmp.c @@ -0,0 +1,71 @@ +/* ABI compatibility for 'longjmp' and 'siglongjmp' symbols in libpthread ABI. + X86 version. + Copyright (C) 18 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <http://www.gnu.org/licenses/>. */ + +#include <pthreadP.h> +#include <jmp_buf-ssp.h> + +#ifdef __x86_64__ +# define SHADOW_STACK_POINTER_SIZE 8 +#else +# define SHADOW_STACK_POINTER_SIZE 4 +#endif + +/* Assert that the priv field in struct pthread_unwind_buf has space + to store shadow stack pointer. */ +_Static_assert ((offsetof (struct pthread_unwind_buf, priv) + <= SHADOW_STACK_POINTER_OFFSET) + && ((offsetof (struct pthread_unwind_buf, priv) + + sizeof (((struct pthread_unwind_buf *) 0)->priv)) + >= (SHADOW_STACK_POINTER_OFFSET + + SHADOW_STACK_POINTER_SIZE)), + "Shadow stack pointer is not within private storage " + "of pthread_unwind_buf."); + +#include <shlib-compat.h> + +/* libpthread once had its own longjmp (and siglongjmp alias), though there + was no apparent reason for it. There is no use in having a separate + symbol in libpthread, but the historical ABI requires it. For static + linking, there is no need to provide anything here--the libc version + will be linked in. For shared library ABI compatibility, there must be + longjmp and siglongjmp symbols in libpthread.so. + + With an IFUNC resolver, it would be possible to avoid the indirection, + but the IFUNC resolver might run before the __libc_longjmp symbol has + been relocated, in which case the IFUNC resolver would not be able to + provide the correct address. */ + +#if SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_22) + +static void __attribute__ ((noreturn, used)) +longjmp_compat (jmp_buf env, int val) +{ + /* NB: We call __libc_siglongjmp, instead of __libc_longjmp, since + __libc_longjmp is a private interface for cancellation which + doesn't restore shadow stack register. */ + __libc_siglongjmp (env, val); +} + +strong_alias (longjmp_compat, longjmp_alias) +compat_symbol (libpthread, longjmp_alias, longjmp, GLIBC_2_0); + +strong_alias (longjmp_alias, siglongjmp_alias) +compat_symbol (libpthread, siglongjmp_alias, siglongjmp, GLIBC_2_0); + +#endif |