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;
We can shrink __sigset_t used by __saved_mask in jmp_buf to add paddings
for target specific usage. 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 defines __jmp_buf_sigset_t for __saved_mask in
jmp_buf on Linux and verifies __jmp_buf_sigset_t has the suitable size
for the __sigprocmask system call.
Tested with build-many-glibcs.py.
OK for master?
H.J.
---
* bits/setjmp3.h: New file.
* sysdeps/unix/sysv/linux/bits/setjmp3.h: Likewise.
* setjmp/Makefile (headers): Add bits/setjmp3.h.
* setjmp/longjmp.c (__libc_siglongjmp): Cast &env[0].__saved_mask
to "sigset_t *".
* setjmp/sigjmp.c (__sigjmp_save): Likewise.
* sysdeps/powerpc/longjmp.c (__vmx__libc_siglongjmp): Likewise.
* sysdeps/powerpc/novmx-longjmp.c (__novmx__libc_siglongjmp):
Likewise.
* sysdeps/powerpc/novmx-sigjmp.c (__novmx__sigjmp_save): Likewise.
* sysdeps/powerpc/sigjmp.c (__vmx__sigjmp_save): Likewise.
* sysdeps/unix/sysv/linux/ia64/unwind_longjmp.c
(__libc_unwind_longjmp): Likewise.
* setjmp/setjmp.h: Include <bits/setjmp3.h> instead of
<bits/types/__sigset_t.h>.
(__jmp_buf_tag): Change __saved_mask to __target.
* setjmp/tst-jmp_buf.c: Include <signal.h>.
[_NSIG] (KERNEL_NSIG_WORDS): New.
[_NSIG] (kernel_sigset_t): Likewise.
[_NSIG] (do_test): Add _Static_assert for size of __saved_mask
in jmp_buf >= sizeof kernel_sigset_t.
---
bits/setjmp3.h | 31 +++++++++++++++++
setjmp/Makefile | 2 +-
setjmp/longjmp.c | 3 +-
setjmp/setjmp.h | 4 +--
setjmp/sigjmp.c | 2 +-
setjmp/tst-jmp_buf.c | 17 ++++++++++
sysdeps/powerpc/longjmp.c | 3 +-
sysdeps/powerpc/novmx-longjmp.c | 3 +-
sysdeps/powerpc/novmx-sigjmp.c | 2 +-
sysdeps/powerpc/sigjmp.c | 2 +-
sysdeps/unix/sysv/linux/bits/setjmp3.h | 48 +++++++++++++++++++++++++++
sysdeps/unix/sysv/linux/ia64/unwind_longjmp.c | 3 +-
12 files changed, 110 insertions(+), 10 deletions(-)
create mode 100644 bits/setjmp3.h
create mode 100644 sysdeps/unix/sysv/linux/bits/setjmp3.h
new file mode 100644
@@ -0,0 +1,31 @@
+/* Generic __jmpbuf_target_t defition.
+ Copyright (C) 2017 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/>. */
+
+#ifndef _SETJMP_H
+# error "Never include <bits/setjmp3.h> directly; use <setjmp.h> instead."
+#endif
+
+#include <bits/types/__sigset_t.h>
+
+typedef struct
+ {
+ __sigset_t __saved_mask;
+ } __jmpbuf_target_t;
+
+/* Saved signal mask. */
+#define __saved_mask __target.__saved_mask
@@ -22,7 +22,7 @@ subdir := setjmp
include ../Makeconfig
-headers := setjmp.h bits/setjmp.h bits/setjmp2.h
+headers := setjmp.h bits/setjmp.h bits/setjmp2.h bits/setjmp3.h
routines := setjmp sigjmp bsd-setjmp bsd-_setjmp \
longjmp __longjmp jmp-unwind
@@ -31,7 +31,8 @@ __libc_siglongjmp (sigjmp_buf env, int val)
if (env[0].__mask_was_saved)
/* Restore the saved signal mask. */
- (void) __sigprocmask (SIG_SETMASK, &env[0].__saved_mask,
+ (void) __sigprocmask (SIG_SETMASK,
+ (sigset_t *) &env[0].__saved_mask,
(sigset_t *) NULL);
/* Call the machine-dependent function to restore machine state. */
@@ -27,7 +27,7 @@
__BEGIN_DECLS
#include <bits/setjmp.h> /* Get `__jmp_buf'. */
-#include <bits/types/__sigset_t.h>
+#include <bits/setjmp3.h>
/* Calling environment, plus possibly a saved signal mask. */
struct __jmp_buf_tag
@@ -38,7 +38,7 @@ struct __jmp_buf_tag
or add others before it. */
__jmp_buf __jmpbuf; /* Calling environment. */
int __mask_was_saved; /* Saved the signal mask? */
- __sigset_t __saved_mask; /* Saved signal mask. */
+ __jmpbuf_target_t __target; /* Target specific data. */
};
@@ -28,7 +28,7 @@ __sigjmp_save (sigjmp_buf env, int savemask)
{
env[0].__mask_was_saved = (savemask &&
__sigprocmask (SIG_BLOCK, (sigset_t *) NULL,
- &env[0].__saved_mask) == 0);
+ (sigset_t *) &env[0].__saved_mask) == 0);
return 0;
}
@@ -18,9 +18,19 @@
#include <stdio.h>
#include <setjmp.h>
+#include <signal.h>
#include <stddef.h>
#include <jmp_buf-macros.h>
+#ifdef _NSIG
+# define KERNEL_NSIG_WORDS (_NSIG / (8 * sizeof (unsigned long int)))
+
+typedef struct
+ {
+ unsigned long int __val[KERNEL_NSIG_WORDS];
+ } kernel_sigset_t;
+#endif
+
#define STR_HELPER(x) #x
#define STR(x) STR_HELPER(x)
@@ -54,6 +64,13 @@ do_test (void)
TEST_OFFSET (struct __jmp_buf_tag, __saved_mask,
SAVED_MASK_OFFSET);
+#ifdef _NSIG
+ jmp_buf buf;
+ __typeof (buf[0].__saved_mask) saved_mask;
+ _Static_assert (sizeof (saved_mask) >= sizeof (kernel_sigset_t),
+ "size of saved_mask < size of kernel_sigset_t");
+#endif
+
return 0;
}
@@ -39,7 +39,8 @@ __vmx__libc_siglongjmp (sigjmp_buf env, int val)
if (env[0].__mask_was_saved)
/* Restore the saved signal mask. */
- (void) __sigprocmask (SIG_SETMASK, &env[0].__saved_mask,
+ (void) __sigprocmask (SIG_SETMASK,
+ (sigset_t *) &env[0].__saved_mask,
(sigset_t *) NULL);
/* Call the machine-dependent function to restore machine state. */
@@ -37,7 +37,8 @@ __novmx__libc_siglongjmp (__novmx__sigjmp_buf env, int val)
if (env[0].__mask_was_saved)
/* Restore the saved signal mask. */
- (void) __sigprocmask (SIG_SETMASK, &env[0].__saved_mask,
+ (void) __sigprocmask (SIG_SETMASK,
+ (sigset_t *) &env[0].__saved_mask,
(sigset_t *) NULL);
/* Call the machine-dependent function to restore machine state. */
@@ -35,7 +35,7 @@ __novmx__sigjmp_save (__novmx__sigjmp_buf env, int savemask)
{
env[0].__mask_was_saved = (savemask &&
__sigprocmask (SIG_BLOCK, (sigset_t *) NULL,
- &env[0].__saved_mask) == 0);
+ (sigset_t *) &env[0].__saved_mask) == 0);
return 0;
}
@@ -31,7 +31,7 @@ __vmx__sigjmp_save (sigjmp_buf env, int savemask)
{
env[0].__mask_was_saved = (savemask &&
__sigprocmask (SIG_BLOCK, (sigset_t *) NULL,
- &env[0].__saved_mask) == 0);
+ (sigset_t *) &env[0].__saved_mask) == 0);
return 0;
}
new file mode 100644
@@ -0,0 +1,48 @@
+/* __jmpbuf_target_t defition for Linux.
+ Copyright (C) 2017 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/>. */
+
+#ifndef _SETJMP_H
+# error "Never include <bits/setjmp3.h> directly; use <setjmp.h> instead."
+#endif
+
+#include <bits/types/__sigset_t.h>
+
+/* The biggest signal number + 1 */
+#define _JUMP_BUF_SIGSET_NSIG 257
+/* 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;
+ /* Paddings for target specific usage. */
+ unsigned long int __padding[12];
+ } __saved;
+ } __jmpbuf_target_t;
+
+/* Saved signal mask. */
+#define __saved_mask __target.__saved.__saved_mask
@@ -34,7 +34,8 @@ __libc_unwind_longjmp (sigjmp_buf env, int val)
if (env[0].__mask_was_saved)
/* Restore the saved signal mask. */
- (void) __sigprocmask (SIG_SETMASK, &env[0].__saved_mask,
+ (void) __sigprocmask (SIG_SETMASK,
+ (sigset_t *) &env[0].__saved_mask,
(sigset_t *) NULL);
/* Call the machine-dependent function to restore machine state. */