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[PATCH] x86: Remove vsyscall usage
- From: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- To: GNU C Library <libc-alpha at sourceware dot org>
- Date: Thu, 23 Apr 2015 18:27:29 -0300
- Subject: [PATCH] x86: Remove vsyscall usage
- Authentication-results: sourceware.org; auth=none
This patch removes the vsyscall usage for x86_64 port. As indicated
by kernel code comments [1], vsyscalls are a legacy ABI and its concept
is problematic:
- It interferes with ASLR.
- It's awkward to write code that lives in kernel addresses but is
callable by userspace at fixed addresses.
- The whole concept is impossible for 32-bit compat userspace.
- UML cannot easily virtualize a vsyscall.
The VDSO is a better approach for such functionality. Tested on i686,
x86_64, and x32.
[1] arch/x86/kernel/vsyscall_64.c
--
* sysdeps/unix/sysv/linux/i386/gettimeofday.c
(__gettimeofday_syscall): Remove.
* sysdeps/unix/sysv/linux/i386/time.c (__time_syscall): Remove.
* sysdeps/unix/sysv/linux/x86/gettimeofday.c (__gettimeofday_syscall):
Add function.
(gettimeofday_ifunc): Use __gettimeofday_syscall as fallback mechanism
if vDSO is not present.
* sysdeps/unix/sysv/linux/x86/time.c (__time_syscall): Add function.
(time_ifunc): Use __time_syscall as fallback mechanism if vDSO is not
present.
* sysdeps/unix/sysv/linux/x86_64/gettimeofday.c: Remove file.
* sysdeps/unix/sysv/linux/x86_64/time.c: Likewise.
---
diff --git a/sysdeps/unix/sysv/linux/i386/gettimeofday.c b/sysdeps/unix/sysv/linux/i386/gettimeofday.c
index 3e00eb4..fdb0fab 100644
--- a/sysdeps/unix/sysv/linux/i386/gettimeofday.c
+++ b/sysdeps/unix/sysv/linux/i386/gettimeofday.c
@@ -20,16 +20,6 @@
#ifdef SHARED
-# include <dl-vdso.h>
-# include <errno.h>
-
-/* If the vDSO is not available we fall back on the syscall. */
-static int
-__gettimeofday_syscall (struct timeval *tv, struct timezone *tz)
-{
- return INLINE_SYSCALL (gettimeofday, 2, tv, tz);
-}
-# define GETTIMEOFAY_FALLBACK (void*) (&__gettimeofday_syscall)
# undef libc_ifunc_hidden_def
# define libc_ifunc_hidden_def(name) \
libc_ifunc_hidden_def1 (__GI_##name, __gettimeofday_syscall)
diff --git a/sysdeps/unix/sysv/linux/i386/time.c b/sysdeps/unix/sysv/linux/i386/time.c
index e8a4e59..66b9a6c 100644
--- a/sysdeps/unix/sysv/linux/i386/time.c
+++ b/sysdeps/unix/sysv/linux/i386/time.c
@@ -18,17 +18,6 @@
#ifdef SHARED
-# include <dl-vdso.h>
-# include <errno.h>
-
-/* If the vDSO is not available we fall back on the old vsyscall. */
-static time_t
-__time_syscall (time_t *t)
-{
- INTERNAL_SYSCALL_DECL (err);
- return INTERNAL_SYSCALL (time, err, 1, t);
-}
-# define TIME_FALLBACK (void*) &__time_syscall
# undef libc_ifunc_hidden_def
# define libc_ifunc_hidden_def(name) \
libc_ifunc_hidden_def1 (__GI_##name, __time_syscall)
diff --git a/sysdeps/unix/sysv/linux/x86/gettimeofday.c b/sysdeps/unix/sysv/linux/x86/gettimeofday.c
index c820fd7..c9cb6ea 100644
--- a/sysdeps/unix/sysv/linux/x86/gettimeofday.c
+++ b/sysdeps/unix/sysv/linux/x86/gettimeofday.c
@@ -21,6 +21,14 @@
#ifdef SHARED
# include <dl-vdso.h>
+# include <errno.h>
+
+/* If the vDSO is not available we fall back on the syscall. */
+static int
+__gettimeofday_syscall (struct timeval *tv, struct timezone *tz)
+{
+ return INLINE_SYSCALL (gettimeofday, 2, tv, tz);
+}
void *gettimeofday_ifunc (void) __asm__ ("__gettimeofday");
@@ -31,7 +39,7 @@ gettimeofday_ifunc (void)
/* If the vDSO is not available we fall back on the old vsyscall. */
return (_dl_vdso_vsym ("__vdso_gettimeofday", &linux26)
- ?: GETTIMEOFAY_FALLBACK);
+ ?: (void*) (&__gettimeofday_syscall));
}
asm (".type __gettimeofday, %gnu_indirect_function");
diff --git a/sysdeps/unix/sysv/linux/x86/time.c b/sysdeps/unix/sysv/linux/x86/time.c
index 1ab9248..3459e17 100644
--- a/sysdeps/unix/sysv/linux/x86/time.c
+++ b/sysdeps/unix/sysv/linux/x86/time.c
@@ -21,6 +21,15 @@
#ifdef SHARED
#include <dl-vdso.h>
+#include <errno.h>
+
+/* If the vDSO is not available we fall back on the old vsyscall. */
+static time_t
+__time_syscall (time_t *t)
+{
+ INTERNAL_SYSCALL_DECL (err);
+ return INTERNAL_SYSCALL (time, err, 1, t);
+}
void *time_ifunc (void) __asm__ ("time");
@@ -29,7 +38,8 @@ time_ifunc (void)
{
PREPARE_VERSION_KNOWN (linux26, LINUX_2_6);
- return _dl_vdso_vsym ("__vdso_time", &linux26) ?: TIME_FALLBACK;
+ return _dl_vdso_vsym ("__vdso_time", &linux26)
+ ?: (void*) &__time_syscall;
}
asm (".type time, %gnu_indirect_function");
diff --git a/sysdeps/unix/sysv/linux/x86_64/gettimeofday.c b/sysdeps/unix/sysv/linux/x86_64/gettimeofday.c
deleted file mode 100644
index daa14de..0000000
--- a/sysdeps/unix/sysv/linux/x86_64/gettimeofday.c
+++ /dev/null
@@ -1,26 +0,0 @@
-/* Copyright (C) 2002-2015 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 <sys/time.h>
-
-#ifdef SHARED
-/* If the vDSO is not available we fall back on the old vsyscall. */
-# define VSYSCALL_ADDR_vgettimeofday 0xffffffffff600000ul
-# define GETTIMEOFAY_FALLBACK (void*)VSYSCALL_ADDR_vgettimeofday
-#endif
-
-#include <sysdeps/unix/sysv/linux/x86/gettimeofday.c>
diff --git a/sysdeps/unix/sysv/linux/x86_64/time.c b/sysdeps/unix/sysv/linux/x86_64/time.c
deleted file mode 100644
index 6ceb819..0000000
--- a/sysdeps/unix/sysv/linux/x86_64/time.c
+++ /dev/null
@@ -1,24 +0,0 @@
-/* Copyright (C) 2001-2015 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/>. */
-
-#ifdef SHARED
-/* If the vDSO is not available we fall back on the old vsyscall. */
-#define VSYSCALL_ADDR_vtime 0xffffffffff600400
-#define TIME_FALLBACK (void*)VSYSCALL_ADDR_vtime
-#endif
-
-#include <sysdeps/unix/sysv/linux/x86/time.c>