From 2aae950b21e4bc789d1fc6668faf67e8748300b7 Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Sat, 21 Jul 2007 17:10:01 +0200 Subject: x86_64: Add vDSO for x86-64 with gettimeofday/clock_gettime/getcpu This implements new vDSO for x86-64. The concept is similar to the existing vDSOs on i386 and PPC. x86-64 has had static vsyscalls before, but these are not flexible enough anymore. A vDSO is a ELF shared library supplied by the kernel that is mapped into user address space. The vDSO mapping is randomized for each process for security reasons. Doing this was needed for clock_gettime, because clock_gettime always needs a syscall fallback and having one at a fixed address would have made buffer overflow exploits too easy to write. The vdso can be disabled with vdso=0 It currently includes a new gettimeofday implemention and optimized clock_gettime(). The gettimeofday implementation is slightly faster than the one in the old vsyscall. clock_gettime is significantly faster than the syscall for CLOCK_MONOTONIC and CLOCK_REALTIME. The new calls are generally faster than the old vsyscall. Advantages over the old x86-64 vsyscalls: - Extensible - Randomized - Cleaner - Easier to virtualize (the old static address range previously causes overhead e.g. for Xen because it has to create special page tables for it) Weak points: - glibc support still to be written The VM interface is partly based on Ingo Molnar's i386 version. Includes compile fix from Joachim Deguara Signed-off-by: Andi Kleen Signed-off-by: Linus Torvalds --- arch/x86_64/kernel/time.c | 1 + arch/x86_64/kernel/vmlinux.lds.S | 9 +++++++++ arch/x86_64/kernel/vsyscall.c | 22 ++++------------------ 3 files changed, 14 insertions(+), 18 deletions(-) (limited to 'arch/x86_64/kernel') diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c index 4a0895bacf51..5405a69a1f72 100644 --- a/arch/x86_64/kernel/time.c +++ b/arch/x86_64/kernel/time.c @@ -44,6 +44,7 @@ #include #include #include +#include static char *timename = NULL; diff --git a/arch/x86_64/kernel/vmlinux.lds.S b/arch/x86_64/kernel/vmlinux.lds.S index 5c57ea4591c1..c2d5a840cb1a 100644 --- a/arch/x86_64/kernel/vmlinux.lds.S +++ b/arch/x86_64/kernel/vmlinux.lds.S @@ -93,6 +93,9 @@ SECTIONS .vsyscall_gtod_data : AT(VLOAD(.vsyscall_gtod_data)) { *(.vsyscall_gtod_data) } vsyscall_gtod_data = VVIRT(.vsyscall_gtod_data); + .vsyscall_clock : AT(VLOAD(.vsyscall_clock)) + { *(.vsyscall_clock) } + vsyscall_clock = VVIRT(.vsyscall_clock); .vsyscall_1 ADDR(.vsyscall_0) + 1024: AT(VLOAD(.vsyscall_1)) @@ -189,6 +192,12 @@ SECTIONS .exit.text : AT(ADDR(.exit.text) - LOAD_OFFSET) { *(.exit.text) } .exit.data : AT(ADDR(.exit.data) - LOAD_OFFSET) { *(.exit.data) } +/* vdso blob that is mapped into user space */ + vdso_start = . ; + .vdso : AT(ADDR(.vdso) - LOAD_OFFSET) { *(.vdso) } + . = ALIGN(4096); + vdso_end = .; + #ifdef CONFIG_BLK_DEV_INITRD . = ALIGN(4096); __initramfs_start = .; diff --git a/arch/x86_64/kernel/vsyscall.c b/arch/x86_64/kernel/vsyscall.c index 57660d58d500..06c34949bfdc 100644 --- a/arch/x86_64/kernel/vsyscall.c +++ b/arch/x86_64/kernel/vsyscall.c @@ -42,6 +42,7 @@ #include #include #include +#include #define __vsyscall(nr) __attribute__ ((unused,__section__(".vsyscall_" #nr))) #define __syscall_clobber "r11","rcx","memory" @@ -57,26 +58,9 @@ * - writen by timer interrupt or systcl (/proc/sys/kernel/vsyscall64) * Try to keep this structure as small as possible to avoid cache line ping pongs */ -struct vsyscall_gtod_data_t { - seqlock_t lock; - - /* open coded 'struct timespec' */ - time_t wall_time_sec; - u32 wall_time_nsec; - - int sysctl_enabled; - struct timezone sys_tz; - struct { /* extract of a clocksource struct */ - cycle_t (*vread)(void); - cycle_t cycle_last; - cycle_t mask; - u32 mult; - u32 shift; - } clock; -}; int __vgetcpu_mode __section_vgetcpu_mode; -struct vsyscall_gtod_data_t __vsyscall_gtod_data __section_vsyscall_gtod_data = +struct vsyscall_gtod_data __vsyscall_gtod_data __section_vsyscall_gtod_data = { .lock = SEQLOCK_UNLOCKED, .sysctl_enabled = 1, @@ -96,6 +80,8 @@ void update_vsyscall(struct timespec *wall_time, struct clocksource *clock) vsyscall_gtod_data.wall_time_sec = wall_time->tv_sec; vsyscall_gtod_data.wall_time_nsec = wall_time->tv_nsec; vsyscall_gtod_data.sys_tz = sys_tz; + vsyscall_gtod_data.wall_time_nsec = wall_time->tv_nsec; + vsyscall_gtod_data.wall_to_monotonic = wall_to_monotonic; write_sequnlock_irqrestore(&vsyscall_gtod_data.lock, flags); } -- cgit v1.2.2