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authorH.J. Lu <hjl.tools@gmail.com>2018-05-02 06:17:20 -0700
committerH.J. Lu <hjl.tools@gmail.com>2018-05-02 06:17:41 -0700
commitd6cc1829aa31b6fb060f24dffd28aa6705cdd33a (patch)
tree197e7983f66d43765505f94a5a29d254d27f6d02
parentb109fbfe4dd2ca77656157ddaded773e0da630a2 (diff)
downloadglibc-d6cc1829aa31b6fb060f24dffd28aa6705cdd33a.tar.gz
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.
-rw-r--r--ChangeLog17
-rw-r--r--nptl/pthread_create.c17
-rw-r--r--setjmp/longjmp.c2
-rw-r--r--sysdeps/unix/sysv/linux/x86/setjmpP.h71
-rw-r--r--sysdeps/x86/Makefile4
-rw-r--r--sysdeps/x86/__longjmp_cancel.S20
-rw-r--r--sysdeps/x86/longjmp.c45
-rw-r--r--sysdeps/x86/nptl/pt-longjmp.c71
8 files changed, 239 insertions, 8 deletions
diff --git a/ChangeLog b/ChangeLog
index 45d30ed07c..da305b79d8 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,20 @@
+2018-05-02 H.J. Lu <hongjiu.lu@intel.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.
+
2018-05-02 Adhemerval Zanella <adhemerval.zanella@linaro.org>
* NEWS: Add ustat.h deprecation entry.
diff --git a/nptl/pthread_create.c b/nptl/pthread_create.c
index caaf07c134..92c945b12b 100644
--- a/nptl/pthread_create.c
+++ b/nptl/pthread_create.c
@@ -427,12 +427,23 @@ START_THREAD_DEFN
compilers without that support we do use setjmp. */
struct pthread_unwind_buf unwind_buf;
- /* No previous handlers. */
+ int not_first_call;
+ not_first_call = setjmp ((struct __jmp_buf_tag *) unwind_buf.cancel_jmp_buf);
+
+ /* No previous handlers. NB: This must be done after setjmp since the
+ private space in the unwind jump buffer may overlap space used by
+ setjmp to store extra architecture-specific information which is
+ never used by the cancellation-specific __libc_unwind_longjmp.
+
+ The private space is allowed to overlap because the unwinder never
+ has to return through any of the jumped-to call frames, and thus
+ only a minimum amount of saved data need be stored, and for example,
+ need not include the process signal mask information. This is all
+ an optimization to reduce stack usage when pushing cancellation
+ handlers. */
unwind_buf.priv.data.prev = NULL;
unwind_buf.priv.data.cleanup = NULL;
- int not_first_call;
- not_first_call = setjmp ((struct __jmp_buf_tag *) unwind_buf.cancel_jmp_buf);
if (__glibc_likely (! not_first_call))
{
/* Store the new cleanup handler info. */
diff --git a/setjmp/longjmp.c b/setjmp/longjmp.c
index a2a7065a85..453889e103 100644
--- a/setjmp/longjmp.c
+++ b/setjmp/longjmp.c
@@ -40,9 +40,11 @@ __libc_siglongjmp (sigjmp_buf env, int val)
}
#ifndef __libc_siglongjmp
+# ifndef __libc_longjmp
/* __libc_longjmp is a private interface for cancellation implementation
in libpthread. */
strong_alias (__libc_siglongjmp, __libc_longjmp)
+# endif
weak_alias (__libc_siglongjmp, _longjmp)
weak_alias (__libc_siglongjmp, longjmp)
weak_alias (__libc_siglongjmp, siglongjmp)
diff --git a/sysdeps/unix/sysv/linux/x86/setjmpP.h b/sysdeps/unix/sysv/linux/x86/setjmpP.h
index c0ed767a0d..6b2608453d 100644
--- a/sysdeps/unix/sysv/linux/x86/setjmpP.h
+++ b/sysdeps/unix/sysv/linux/x86/setjmpP.h
@@ -20,13 +20,72 @@
#define _SETJMPP_H 1
#include <bits/types/__sigset_t.h>
+#include <libc-pointer-arith.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
+/* <setjmp/setjmp.h> has
+
+struct __jmp_buf_tag
+ {
+ __jmp_buf __jmpbuf;
+ int __mask_was_saved;
+ __sigset_t __saved_mask;
+ };
+
+ struct __jmp_buf_tag is 32 bits aligned on i386 and is 64 bits
+ aligned on x32 and x86-64. __saved_mask is aligned to 32 bits
+ on i386/x32 without padding and is aligned to 64 bits on x86-64
+ with 32 bit padding.
+
+ and <nptl/descr.h> has
+
+struct pthread_unwind_buf
+{
+ struct
+ {
+ __jmp_buf jmp_buf;
+ int mask_was_saved;
+ } cancel_jmp_buf[1];
+
+ union
+ {
+ void *pad[4];
+ struct
+ {
+ struct pthread_unwind_buf *prev;
+ struct _pthread_cleanup_buffer *cleanup;
+ int canceltype;
+ } data;
+ } priv;
+};
+
+ struct pthread_unwind_buf is 32 bits aligned on i386 and 64 bits
+ aligned on x32/x86-64. cancel_jmp_buf is aligned to 32 bits on
+ i386 and is aligned to 64 bits on x32/x86-64.
+
+ The pad array in struct pthread_unwind_buf is used by setjmp to save
+ shadow stack register. The usable space in __saved_mask for sigset
+ and shadow stack pointer:
+ 1. i386: The 4x4 byte pad array which can be used for 4 byte shadow
+ stack pointer and maximum 12 byte sigset.
+ 2. x32: 4 byte padding + the 4x4 byte pad array which can be used
+ for 8 byte shadow stack pointer and maximum 12 byte sigset.
+ 3. x86-64: The 4x8 byte pad array which can be used for 8 byte
+ shadow stack pointer and maximum 24 byte sigset.
+
+ NB: We use setjmp in thread cancellation and this saves the shadow
+ stack register, but __libc_unwind_longjmp doesn't restore the shadow
+ stack register since cancellation never returns after longjmp. */
+
+/* Number of bits per long. */
+#define _JUMP_BUF_SIGSET_BITS_PER_WORD (8 * sizeof (unsigned long int))
+/* The biggest signal number. As of kernel 4.14, x86 _NSIG is 64. The
+ common maximum sigset for i386, x32 and x86-64 is 12 bytes (96 bits).
+ Define it to 96 to leave some rooms for future use. */
+#define _JUMP_BUF_SIGSET_NSIG 96
/* Number of longs to hold all signals. */
#define _JUMP_BUF_SIGSET_NWORDS \
- ((_JUMP_BUF_SIGSET_NSIG - 1 + 7) / (8 * sizeof (unsigned long int)))
+ (ALIGN_UP (_JUMP_BUF_SIGSET_NSIG, _JUMP_BUF_SIGSET_BITS_PER_WORD) \
+ / _JUMP_BUF_SIGSET_BITS_PER_WORD)
typedef struct
{
@@ -39,7 +98,9 @@ typedef union
struct
{
__jmp_buf_sigset_t __saved_mask;
- /* Used for shadow stack pointer. */
+ /* Used for shadow stack pointer. NB: Shadow stack pointer
+ must have the same alignment as __saved_mask. Otherwise
+ offset of __saved_mask will be changed. */
unsigned long int __shadow_stack_pointer;
} __saved;
} __jmpbuf_arch_t;
diff --git a/sysdeps/x86/Makefile b/sysdeps/x86/Makefile
index 0d0326c21a..d25d6f0ae4 100644
--- a/sysdeps/x86/Makefile
+++ b/sysdeps/x86/Makefile
@@ -8,3 +8,7 @@ sysdep-dl-routines += dl-get-cpu-features
tests += tst-get-cpu-features
tests-static += tst-get-cpu-features-static
endif
+
+ifeq ($(subdir),setjmp)
+sysdep_routines += __longjmp_cancel
+endif
diff --git a/sysdeps/x86/__longjmp_cancel.S b/sysdeps/x86/__longjmp_cancel.S
new file mode 100644
index 0000000000..b57dbfa376
--- /dev/null
+++ b/sysdeps/x86/__longjmp_cancel.S
@@ -0,0 +1,20 @@
+/* __longjmp_cancel for x86.
+ Copyright (C) 2018 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/>. */
+
+#define __longjmp __longjmp_cancel
+#include <__longjmp.S>
diff --git a/sysdeps/x86/longjmp.c b/sysdeps/x86/longjmp.c
new file mode 100644
index 0000000000..a53f31e1dd
--- /dev/null
+++ b/sysdeps/x86/longjmp.c
@@ -0,0 +1,45 @@
+/* __libc_siglongjmp for x86.
+ Copyright (C) 2018 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/>. */
+
+#define __libc_longjmp __redirect___libc_longjmp
+#include <setjmp/longjmp.c>
+#undef __libc_longjmp
+
+extern void __longjmp_cancel (__jmp_buf __env, int __val)
+ __attribute__ ((__noreturn__)) attribute_hidden;
+
+/* Since __libc_longjmp is a private interface for cancellation
+ implementation in libpthread, there is no need to restore shadow
+ stack register. */
+
+void
+__libc_longjmp (sigjmp_buf env, int val)
+{
+ /* Perform any cleanups needed by the frames being unwound. */
+ _longjmp_unwind (env, val);
+
+ if (env[0].__mask_was_saved)
+ /* Restore the saved signal mask. */
+ (void) __sigprocmask (SIG_SETMASK,
+ (sigset_t *) &env[0].__saved_mask,
+ (sigset_t *) NULL);
+
+ /* Call the machine-dependent function to restore machine state
+ without shadow stack. */
+ __longjmp_cancel (env[0].__jmpbuf, val ?: 1);
+}
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