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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: Mon, 11 May 2015 16:12:50 -0300
- Subject: Re: [PATCH] x86: Remove vsyscall usage
- Authentication-results: sourceware.org; auth=none
- References: <553963C1 dot 2080600 at linaro dot org>
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>
>