x86: Make a space in jmpbuf for shadow stack pointer
To support Shadow Stack (SHSTK) in Intel Control-flow Enforcement
Technology (CET) in setjmp/longjmp, we need to save shadow stack
pointer in jmp_buf. The __saved_mask field in jmp_buf has type
of __sigset_t. On Linux, __sigset_t is defined as
#define _SIGSET_NWORDS (1024 / (8 * sizeof (unsigned long int)))
typedef struct
{
unsigned long int __val[_SIGSET_NWORDS];
} __sigset_t;
which is much bigger than expected by the __sigprocmask system call,
which has
typedef struct {
unsigned long sig[_NSIG_WORDS];
} sigset_t;
For Linux/x86, we can shrink __sigset_t used by __saved_mask in jmp_buf
to add paddings for shadow stack pointer. As long as the new __sigset_t
is not smaller than sigset_t expected by the __sigprocmask system call,
it should work correctly.
This patch adds an internal header file, <setjmpP.h>, to define
__jmp_buf_sigset_t for __saved_mask in jmp_buf for Linux/x86 with a
space to store shadow stack pointer. It verifies __jmp_buf_sigset_t has
the suitable size for the __sigprocmask system call. A run-time test,
tst-saved_mask-1.c, is added to verify that size of __jmp_buf_sigset_t
is sufficient. If its size is too small, the test fails with
rt_sigprocmask(SIG_SETMASK, strace: umoven: short read (4 < 8) @0x7fa8aa28effc
0x7fa8aa28effc, NULL, 8) = -1 EFAULT (Bad address)
rt_sigprocmask(SIG_SETMASK, strace: umoven: short read (4 < 8) @0x7fa8aa28effc
0x7fa8aa28effc, NULL, 8) = -1 EFAULT (Bad address)
rt_sigprocmask(SIG_SETMASK, NULL, 0x7fa8aa28effc, 8) = -1 EFAULT (Bad address)
exit_group(1) = ?
Tested with build-many-glibcs.py.
* debug/longjmp_chk.c: Include <setjmpP.h> instead of
<setjmp.h>.
* setjmp/longjmp.c: Include <setjmpP.h> instead of <setjmp.h>.
(__libc_siglongjmp): Cast &env[0].__saved_mask to "sigset_t *".
* setjmp/sigjmp.c: Include <setjmpP.h> instead of <setjmp.h>.
(__sigjmp_save): Cast &env[0].__saved_mask to "sigset_t *".
* sysdeps/generic/setjmpP.h: New file.
* sysdeps/unix/sysv/linux/x86/jmp_buf-ssp.sym: Likewise.
* sysdeps/unix/sysv/linux/x86/setjmpP.h: Likewise.
* sysdeps/unix/sysv/linux/x86/tst-saved_mask-1.c: Likewise.
* sysdeps/unix/sysv/linux/x86/Makefile (gen-as-const-headers):
Add jmp_buf-ssp.sym.
(tests): Add tst-saved_mask-1.
2017-11-30 12:49:25 +00:00
|
|
|
/* Internal header file for <setjmp.h>. Linux/x86 version.
|
2018-01-01 00:32:25 +00:00
|
|
|
Copyright (C) 2017-2018 Free Software Foundation, Inc.
|
x86: Make a space in jmpbuf for shadow stack pointer
To support Shadow Stack (SHSTK) in Intel Control-flow Enforcement
Technology (CET) in setjmp/longjmp, we need to save shadow stack
pointer in jmp_buf. The __saved_mask field in jmp_buf has type
of __sigset_t. On Linux, __sigset_t is defined as
#define _SIGSET_NWORDS (1024 / (8 * sizeof (unsigned long int)))
typedef struct
{
unsigned long int __val[_SIGSET_NWORDS];
} __sigset_t;
which is much bigger than expected by the __sigprocmask system call,
which has
typedef struct {
unsigned long sig[_NSIG_WORDS];
} sigset_t;
For Linux/x86, we can shrink __sigset_t used by __saved_mask in jmp_buf
to add paddings for shadow stack pointer. As long as the new __sigset_t
is not smaller than sigset_t expected by the __sigprocmask system call,
it should work correctly.
This patch adds an internal header file, <setjmpP.h>, to define
__jmp_buf_sigset_t for __saved_mask in jmp_buf for Linux/x86 with a
space to store shadow stack pointer. It verifies __jmp_buf_sigset_t has
the suitable size for the __sigprocmask system call. A run-time test,
tst-saved_mask-1.c, is added to verify that size of __jmp_buf_sigset_t
is sufficient. If its size is too small, the test fails with
rt_sigprocmask(SIG_SETMASK, strace: umoven: short read (4 < 8) @0x7fa8aa28effc
0x7fa8aa28effc, NULL, 8) = -1 EFAULT (Bad address)
rt_sigprocmask(SIG_SETMASK, strace: umoven: short read (4 < 8) @0x7fa8aa28effc
0x7fa8aa28effc, NULL, 8) = -1 EFAULT (Bad address)
rt_sigprocmask(SIG_SETMASK, NULL, 0x7fa8aa28effc, 8) = -1 EFAULT (Bad address)
exit_group(1) = ?
Tested with build-many-glibcs.py.
* debug/longjmp_chk.c: Include <setjmpP.h> instead of
<setjmp.h>.
* setjmp/longjmp.c: Include <setjmpP.h> instead of <setjmp.h>.
(__libc_siglongjmp): Cast &env[0].__saved_mask to "sigset_t *".
* setjmp/sigjmp.c: Include <setjmpP.h> instead of <setjmp.h>.
(__sigjmp_save): Cast &env[0].__saved_mask to "sigset_t *".
* sysdeps/generic/setjmpP.h: New file.
* sysdeps/unix/sysv/linux/x86/jmp_buf-ssp.sym: Likewise.
* sysdeps/unix/sysv/linux/x86/setjmpP.h: Likewise.
* sysdeps/unix/sysv/linux/x86/tst-saved_mask-1.c: Likewise.
* sysdeps/unix/sysv/linux/x86/Makefile (gen-as-const-headers):
Add jmp_buf-ssp.sym.
(tests): Add tst-saved_mask-1.
2017-11-30 12:49:25 +00:00
|
|
|
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/>. */
|
|
|
|
|
|
|
|
#ifndef _SETJMPP_H
|
|
|
|
#define _SETJMPP_H 1
|
|
|
|
|
|
|
|
#include <bits/types/__sigset_t.h>
|
|
|
|
|
|
|
|
/* The biggest signal number + 1. As of kernel 4.14, x86 _NSIG is 64.
|
|
|
|
Define it to 513 to leave some rooms for future use. */
|
|
|
|
#define _JUMP_BUF_SIGSET_NSIG 513
|
|
|
|
/* Number of longs to hold all signals. */
|
|
|
|
#define _JUMP_BUF_SIGSET_NWORDS \
|
|
|
|
((_JUMP_BUF_SIGSET_NSIG - 1 + 7) / (8 * sizeof (unsigned long int)))
|
|
|
|
|
|
|
|
typedef struct
|
|
|
|
{
|
|
|
|
unsigned long int __val[_JUMP_BUF_SIGSET_NWORDS];
|
|
|
|
} __jmp_buf_sigset_t;
|
|
|
|
|
|
|
|
typedef union
|
|
|
|
{
|
|
|
|
__sigset_t __saved_mask_compat;
|
|
|
|
struct
|
|
|
|
{
|
|
|
|
__jmp_buf_sigset_t __saved_mask;
|
|
|
|
/* Used for shadow stack pointer. */
|
|
|
|
unsigned long int __shadow_stack_pointer;
|
|
|
|
} __saved;
|
|
|
|
} __jmpbuf_arch_t;
|
|
|
|
|
|
|
|
#undef __sigset_t
|
|
|
|
#define __sigset_t __jmpbuf_arch_t
|
|
|
|
#include <setjmp.h>
|
|
|
|
#undef __saved_mask
|
|
|
|
#define __saved_mask __saved_mask.__saved.__saved_mask
|
|
|
|
|
|
|
|
#include <signal.h>
|
|
|
|
|
|
|
|
#define _SIGPROCMASK_NSIG_WORDS (_NSIG / (8 * sizeof (unsigned long int)))
|
|
|
|
|
|
|
|
typedef struct
|
|
|
|
{
|
|
|
|
unsigned long int __val[_SIGPROCMASK_NSIG_WORDS];
|
|
|
|
} __sigprocmask_sigset_t;
|
|
|
|
|
|
|
|
extern jmp_buf ___buf;
|
|
|
|
extern __typeof (___buf[0].__saved_mask) ___saved_mask;
|
|
|
|
_Static_assert (sizeof (___saved_mask) >= sizeof (__sigprocmask_sigset_t),
|
|
|
|
"size of ___saved_mask < size of __sigprocmask_sigset_t");
|
|
|
|
|
|
|
|
#endif /* setjmpP.h */
|