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Re: [PATCH] x86: Remove vsyscall usage


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>
>>>


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