linux/arch/x86/vdso/vclock_gettime.c
Andy Lutomirski 46b57a7693 x86/vdso: Move DISABLE_BRANCH_PROFILING into the vdso makefile
DISABLE_BRANCH_PROFILING turns off branch profiling (i.e. a
redefinition of 'if').  Branch profiling depends on a bunch of
kernel-internal symbols and generates extra output sections, none of
which are useful or functional in the vDSO.

It's currently turned off for vclock_gettime.c, but vgetcpu.c also
triggers branch profiling, so just turn it off in the makefile.

This fixes the build on some configurations: the vdso could contain
undefined symbols, and the fake section table overflowed due to
ftrace's added sections.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Link: http://lkml.kernel.org/r/bf1ec29e03b2bbc081f6dcaefa64db1c3a83fb21.1403642755.git.luto@amacapital.net
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
2014-06-24 13:53:00 -07:00

352 lines
8.1 KiB
C

/*
* Copyright 2006 Andi Kleen, SUSE Labs.
* Subject to the GNU Public License, v.2
*
* Fast user context implementation of clock_gettime, gettimeofday, and time.
*
* 32 Bit compat layer by Stefani Seibold <stefani@seibold.net>
* sponsored by Rohde & Schwarz GmbH & Co. KG Munich/Germany
*
* The code should have no internal unresolved relocations.
* Check with readelf after changing.
*/
#include <uapi/linux/time.h>
#include <asm/vgtod.h>
#include <asm/hpet.h>
#include <asm/vvar.h>
#include <asm/unistd.h>
#include <asm/msr.h>
#include <linux/math64.h>
#include <linux/time.h>
#define gtod (&VVAR(vsyscall_gtod_data))
extern int __vdso_clock_gettime(clockid_t clock, struct timespec *ts);
extern int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz);
extern time_t __vdso_time(time_t *t);
#ifdef CONFIG_HPET_TIMER
extern u8 hpet_page
__attribute__((visibility("hidden")));
static notrace cycle_t vread_hpet(void)
{
return *(const volatile u32 *)(&hpet_page + HPET_COUNTER);
}
#endif
#ifndef BUILD_VDSO32
#include <linux/kernel.h>
#include <asm/vsyscall.h>
#include <asm/fixmap.h>
#include <asm/pvclock.h>
notrace static long vdso_fallback_gettime(long clock, struct timespec *ts)
{
long ret;
asm("syscall" : "=a" (ret) :
"0" (__NR_clock_gettime), "D" (clock), "S" (ts) : "memory");
return ret;
}
notrace static long vdso_fallback_gtod(struct timeval *tv, struct timezone *tz)
{
long ret;
asm("syscall" : "=a" (ret) :
"0" (__NR_gettimeofday), "D" (tv), "S" (tz) : "memory");
return ret;
}
#ifdef CONFIG_PARAVIRT_CLOCK
static notrace const struct pvclock_vsyscall_time_info *get_pvti(int cpu)
{
const struct pvclock_vsyscall_time_info *pvti_base;
int idx = cpu / (PAGE_SIZE/PVTI_SIZE);
int offset = cpu % (PAGE_SIZE/PVTI_SIZE);
BUG_ON(PVCLOCK_FIXMAP_BEGIN + idx > PVCLOCK_FIXMAP_END);
pvti_base = (struct pvclock_vsyscall_time_info *)
__fix_to_virt(PVCLOCK_FIXMAP_BEGIN+idx);
return &pvti_base[offset];
}
static notrace cycle_t vread_pvclock(int *mode)
{
const struct pvclock_vsyscall_time_info *pvti;
cycle_t ret;
u64 last;
u32 version;
u8 flags;
unsigned cpu, cpu1;
/*
* Note: hypervisor must guarantee that:
* 1. cpu ID number maps 1:1 to per-CPU pvclock time info.
* 2. that per-CPU pvclock time info is updated if the
* underlying CPU changes.
* 3. that version is increased whenever underlying CPU
* changes.
*
*/
do {
cpu = __getcpu() & VGETCPU_CPU_MASK;
/* TODO: We can put vcpu id into higher bits of pvti.version.
* This will save a couple of cycles by getting rid of
* __getcpu() calls (Gleb).
*/
pvti = get_pvti(cpu);
version = __pvclock_read_cycles(&pvti->pvti, &ret, &flags);
/*
* Test we're still on the cpu as well as the version.
* We could have been migrated just after the first
* vgetcpu but before fetching the version, so we
* wouldn't notice a version change.
*/
cpu1 = __getcpu() & VGETCPU_CPU_MASK;
} while (unlikely(cpu != cpu1 ||
(pvti->pvti.version & 1) ||
pvti->pvti.version != version));
if (unlikely(!(flags & PVCLOCK_TSC_STABLE_BIT)))
*mode = VCLOCK_NONE;
/* refer to tsc.c read_tsc() comment for rationale */
last = gtod->cycle_last;
if (likely(ret >= last))
return ret;
return last;
}
#endif
#else
notrace static long vdso_fallback_gettime(long clock, struct timespec *ts)
{
long ret;
asm(
"mov %%ebx, %%edx \n"
"mov %2, %%ebx \n"
"call __kernel_vsyscall \n"
"mov %%edx, %%ebx \n"
: "=a" (ret)
: "0" (__NR_clock_gettime), "g" (clock), "c" (ts)
: "memory", "edx");
return ret;
}
notrace static long vdso_fallback_gtod(struct timeval *tv, struct timezone *tz)
{
long ret;
asm(
"mov %%ebx, %%edx \n"
"mov %2, %%ebx \n"
"call __kernel_vsyscall \n"
"mov %%edx, %%ebx \n"
: "=a" (ret)
: "0" (__NR_gettimeofday), "g" (tv), "c" (tz)
: "memory", "edx");
return ret;
}
#ifdef CONFIG_PARAVIRT_CLOCK
static notrace cycle_t vread_pvclock(int *mode)
{
*mode = VCLOCK_NONE;
return 0;
}
#endif
#endif
notrace static cycle_t vread_tsc(void)
{
cycle_t ret;
u64 last;
/*
* Empirically, a fence (of type that depends on the CPU)
* before rdtsc is enough to ensure that rdtsc is ordered
* with respect to loads. The various CPU manuals are unclear
* as to whether rdtsc can be reordered with later loads,
* but no one has ever seen it happen.
*/
rdtsc_barrier();
ret = (cycle_t)__native_read_tsc();
last = gtod->cycle_last;
if (likely(ret >= last))
return ret;
/*
* GCC likes to generate cmov here, but this branch is extremely
* predictable (it's just a funciton of time and the likely is
* very likely) and there's a data dependence, so force GCC
* to generate a branch instead. I don't barrier() because
* we don't actually need a barrier, and if this function
* ever gets inlined it will generate worse code.
*/
asm volatile ("");
return last;
}
notrace static inline u64 vgetsns(int *mode)
{
u64 v;
cycles_t cycles;
if (gtod->vclock_mode == VCLOCK_TSC)
cycles = vread_tsc();
#ifdef CONFIG_HPET_TIMER
else if (gtod->vclock_mode == VCLOCK_HPET)
cycles = vread_hpet();
#endif
#ifdef CONFIG_PARAVIRT_CLOCK
else if (gtod->vclock_mode == VCLOCK_PVCLOCK)
cycles = vread_pvclock(mode);
#endif
else
return 0;
v = (cycles - gtod->cycle_last) & gtod->mask;
return v * gtod->mult;
}
/* Code size doesn't matter (vdso is 4k anyway) and this is faster. */
notrace static int __always_inline do_realtime(struct timespec *ts)
{
unsigned long seq;
u64 ns;
int mode;
do {
seq = gtod_read_begin(gtod);
mode = gtod->vclock_mode;
ts->tv_sec = gtod->wall_time_sec;
ns = gtod->wall_time_snsec;
ns += vgetsns(&mode);
ns >>= gtod->shift;
} while (unlikely(gtod_read_retry(gtod, seq)));
ts->tv_sec += __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
ts->tv_nsec = ns;
return mode;
}
notrace static int __always_inline do_monotonic(struct timespec *ts)
{
unsigned long seq;
u64 ns;
int mode;
do {
seq = gtod_read_begin(gtod);
mode = gtod->vclock_mode;
ts->tv_sec = gtod->monotonic_time_sec;
ns = gtod->monotonic_time_snsec;
ns += vgetsns(&mode);
ns >>= gtod->shift;
} while (unlikely(gtod_read_retry(gtod, seq)));
ts->tv_sec += __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
ts->tv_nsec = ns;
return mode;
}
notrace static void do_realtime_coarse(struct timespec *ts)
{
unsigned long seq;
do {
seq = gtod_read_begin(gtod);
ts->tv_sec = gtod->wall_time_coarse_sec;
ts->tv_nsec = gtod->wall_time_coarse_nsec;
} while (unlikely(gtod_read_retry(gtod, seq)));
}
notrace static void do_monotonic_coarse(struct timespec *ts)
{
unsigned long seq;
do {
seq = gtod_read_begin(gtod);
ts->tv_sec = gtod->monotonic_time_coarse_sec;
ts->tv_nsec = gtod->monotonic_time_coarse_nsec;
} while (unlikely(gtod_read_retry(gtod, seq)));
}
notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
{
switch (clock) {
case CLOCK_REALTIME:
if (do_realtime(ts) == VCLOCK_NONE)
goto fallback;
break;
case CLOCK_MONOTONIC:
if (do_monotonic(ts) == VCLOCK_NONE)
goto fallback;
break;
case CLOCK_REALTIME_COARSE:
do_realtime_coarse(ts);
break;
case CLOCK_MONOTONIC_COARSE:
do_monotonic_coarse(ts);
break;
default:
goto fallback;
}
return 0;
fallback:
return vdso_fallback_gettime(clock, ts);
}
int clock_gettime(clockid_t, struct timespec *)
__attribute__((weak, alias("__vdso_clock_gettime")));
notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
{
if (likely(tv != NULL)) {
if (unlikely(do_realtime((struct timespec *)tv) == VCLOCK_NONE))
return vdso_fallback_gtod(tv, tz);
tv->tv_usec /= 1000;
}
if (unlikely(tz != NULL)) {
tz->tz_minuteswest = gtod->tz_minuteswest;
tz->tz_dsttime = gtod->tz_dsttime;
}
return 0;
}
int gettimeofday(struct timeval *, struct timezone *)
__attribute__((weak, alias("__vdso_gettimeofday")));
/*
* This will break when the xtime seconds get inaccurate, but that is
* unlikely
*/
notrace time_t __vdso_time(time_t *t)
{
/* This is atomic on x86 so we don't need any locks. */
time_t result = ACCESS_ONCE(gtod->wall_time_sec);
if (t)
*t = result;
return result;
}
int time(time_t *t)
__attribute__((weak, alias("__vdso_time")));