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Re: [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: Tue, 09 Jun 2015 17:31:12 -0300
- Subject: Re: [PATCH] x86: Remove vsyscall usage
- Authentication-results: sourceware.org; auth=none
- References: <553963C1 dot 2080600 at linaro dot org> <5550FF32 dot 5040708 at linaro dot org> <5571F19A dot 2030807 at linaro dot org>
I will commit it soon if noone opposes it.
On 05-06-2015 15:59, Adhemerval Zanella wrote:
> Ping.
>
> On 11-05-2015 16:12, Adhemerval Zanella wrote:
>> Ping.
>>
>> On 23-04-2015 18:27, Adhemerval Zanella wrote:
>>> 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>
>>>