From 7cbeabac0fb28e24c99aaa5085e613ea543a2346 Mon Sep 17 00:00:00 2001 From: Adhemerval Zanella Date: Thu, 23 Apr 2015 09:17:42 -0300 Subject: x86: Remove vsyscall usage 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 --- sysdeps/unix/sysv/linux/x86/gettimeofday.c | 11 +++++++++-- sysdeps/unix/sysv/linux/x86/time.c | 12 +++++++++++- 2 files changed, 20 insertions(+), 3 deletions(-) (limited to 'sysdeps/unix/sysv/linux/x86') diff --git a/sysdeps/unix/sysv/linux/x86/gettimeofday.c b/sysdeps/unix/sysv/linux/x86/gettimeofday.c index c820fd767b..440cb0243a 100644 --- a/sysdeps/unix/sysv/linux/x86/gettimeofday.c +++ b/sysdeps/unix/sysv/linux/x86/gettimeofday.c @@ -21,6 +21,13 @@ #ifdef SHARED # include +# include + +static int +__gettimeofday_syscall (struct timeval *tv, struct timezone *tz) +{ + return INLINE_SYSCALL (gettimeofday, 2, tv, tz); +} void *gettimeofday_ifunc (void) __asm__ ("__gettimeofday"); @@ -29,9 +36,9 @@ gettimeofday_ifunc (void) { PREPARE_VERSION_KNOWN (linux26, LINUX_2_6); - /* If the vDSO is not available we fall back on the old vsyscall. */ + /* If the vDSO is not available we fall back to syscall. */ 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 1ab92489e5..ebf092ae12 100644 --- a/sysdeps/unix/sysv/linux/x86/time.c +++ b/sysdeps/unix/sysv/linux/x86/time.c @@ -21,6 +21,14 @@ #ifdef SHARED #include +#include + +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 +37,9 @@ time_ifunc (void) { PREPARE_VERSION_KNOWN (linux26, LINUX_2_6); - return _dl_vdso_vsym ("__vdso_time", &linux26) ?: TIME_FALLBACK; +/* If the vDSO is not available we fall back on the syscall. */ + return _dl_vdso_vsym ("__vdso_time", &linux26) + ?: (void*) &__time_syscall; } asm (".type time, %gnu_indirect_function"); -- cgit 1.4.1