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x86: Remove vsyscall usage

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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.

	* sysdeps/unix/sysv/linux/i386/gettimeofday.c
	(__gettimeofday_syscall): Remove vsyscall fallback.
	* sysdeps/unix/sysv/linux/i386/time.c (__time_syscall): Likewise.
	* sysdeps/unix/sysv/linux/x86/gettimeofday.c (__gettimeofday_syscall):
	Add syscall fallback function.
	(gettimeofday_ifunc): Use __gettimeofday_syscall as fallback mechanism
	if vDSO is not present.
	* sysdeps/unix/sysv/linux/x86/time.c (__time_syscall): Add syscall
	fallback 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.

[1] arch/x86/kernel/vsyscall_64.c
This commit is contained in:
Adhemerval Zanella
2015-04-23 09:17:42 -03:00
committed by Adhemerval Zanella
parent 2f44ee08db
commit 7cbeabac0f
7 changed files with 36 additions and 74 deletions
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11
sysdeps/unix/sysv/linux/i386/time.c
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@ -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)