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Subject[PATCH v13 9/9] Add 32 bit VDSO time support for 64 bit kernel
Date
From: Stefani Seibold <stefani@seibold.net>

This patch add the VDSO time support for the IA32 Emulation Layer.

Due the nature of the kernel headers and the LP64 compiler where the
size of a long and a pointer differs against a 32 bit compiler, there
is some type hacking necessary for optimal performance.

The vsyscall_gtod_data struture must be a rearranged to serve 32- and
64-bit code access at the same time:

- The seqcount_t was replaced by an unsigned, this makes the
vsyscall_gtod_data intedepend of kernel configuration and internal functions.
- All kernel internal structures are replaced by fix size elements
which works for 32- and 64-bit access
- The inner struct clock was removed to pack the whole struct.

The "unsigned seq" would be handled by functions derivated from seqcount_t.

Conflicts:
arch/x86/vdso/vclock_gettime.c

Signed-off-by: Stefani Seibold <stefani@seibold.net>
---
arch/x86/include/asm/vgtod.h | 69 +++++++++++++++++++++++++++-------
arch/x86/kernel/vsyscall_gtod.c | 33 ++++++++++------
arch/x86/vdso/vclock_gettime.c | 71 +++++++++++++++++------------------
arch/x86/vdso/vdso32/vclock_gettime.c | 7 ++++
4 files changed, 118 insertions(+), 62 deletions(-)

diff --git a/arch/x86/include/asm/vgtod.h b/arch/x86/include/asm/vgtod.h
index 46e24d3..abb9e45 100644
--- a/arch/x86/include/asm/vgtod.h
+++ b/arch/x86/include/asm/vgtod.h
@@ -4,27 +4,70 @@
#include <asm/vsyscall.h>
#include <linux/clocksource.h>

+#ifdef CONFIG_X86_64
+typedef u64 gtod_long_t;
+#else
+typedef u32 gtod_long_t;
+#endif
+/*
+ * vsyscall_gtod_data will be accessed by 32 and 64 bit code at the same time
+ * so be carefull by modifying this structure.
+ */
struct vsyscall_gtod_data {
- seqcount_t seq;
+ unsigned seq;

- struct { /* extract of a clocksource struct */
- int vclock_mode;
- cycle_t cycle_last;
- cycle_t mask;
- u32 mult;
- u32 shift;
- } clock;
+ int vclock_mode;
+ cycle_t cycle_last;
+ cycle_t mask;
+ u32 mult;
+ u32 shift;

/* open coded 'struct timespec' */
- time_t wall_time_sec;
u64 wall_time_snsec;
+ gtod_long_t wall_time_sec;
+ gtod_long_t monotonic_time_sec;
u64 monotonic_time_snsec;
- time_t monotonic_time_sec;
+ gtod_long_t wall_time_coarse_sec;
+ gtod_long_t wall_time_coarse_nsec;
+ gtod_long_t monotonic_time_coarse_sec;
+ gtod_long_t monotonic_time_coarse_nsec;

- struct timezone sys_tz;
- struct timespec wall_time_coarse;
- struct timespec monotonic_time_coarse;
+ int tz_minuteswest;
+ int tz_dsttime;
};
extern struct vsyscall_gtod_data vsyscall_gtod_data;

+static inline unsigned gtod_read_begin(const struct vsyscall_gtod_data *s)
+{
+ unsigned ret;
+
+repeat:
+ ret = ACCESS_ONCE(s->seq);
+ if (unlikely(ret & 1)) {
+ cpu_relax();
+ goto repeat;
+ }
+ smp_rmb();
+ return ret;
+}
+
+static inline int gtod_read_retry(const struct vsyscall_gtod_data *s,
+ unsigned start)
+{
+ smp_rmb();
+ return unlikely(s->seq != start);
+}
+
+static inline void gtod_write_begin(struct vsyscall_gtod_data *s)
+{
+ ++s->seq;
+ smp_wmb();
+}
+
+static inline void gtod_write_end(struct vsyscall_gtod_data *s)
+{
+ smp_wmb();
+ ++s->seq;
+}
+
#endif /* _ASM_X86_VGTOD_H */
diff --git a/arch/x86/kernel/vsyscall_gtod.c b/arch/x86/kernel/vsyscall_gtod.c
index 91862a4..973dcc4 100644
--- a/arch/x86/kernel/vsyscall_gtod.c
+++ b/arch/x86/kernel/vsyscall_gtod.c
@@ -4,6 +4,7 @@
*
* Modified for x86 32 bit architecture by
* Stefani Seibold <stefani@seibold.net>
+ * sponsored by Rohde & Schwarz GmbH & Co. KG Munich/Germany
*
* Thanks to hpa@transmeta.com for some useful hint.
* Special thanks to Ingo Molnar for his early experience with
@@ -18,21 +19,22 @@ DEFINE_VVAR(struct vsyscall_gtod_data, vsyscall_gtod_data);

void update_vsyscall_tz(void)
{
- vsyscall_gtod_data.sys_tz = sys_tz;
+ vsyscall_gtod_data.tz_minuteswest = sys_tz.tz_minuteswest;
+ vsyscall_gtod_data.tz_dsttime = sys_tz.tz_dsttime;
}

void update_vsyscall(struct timekeeper *tk)
{
struct vsyscall_gtod_data *vdata = &vsyscall_gtod_data;

- write_seqcount_begin(&vdata->seq);
+ gtod_write_begin(vdata);

/* copy vsyscall data */
- vdata->clock.vclock_mode = tk->clock->archdata.vclock_mode;
- vdata->clock.cycle_last = tk->clock->cycle_last;
- vdata->clock.mask = tk->clock->mask;
- vdata->clock.mult = tk->mult;
- vdata->clock.shift = tk->shift;
+ vdata->vclock_mode = tk->clock->archdata.vclock_mode;
+ vdata->cycle_last = tk->clock->cycle_last;
+ vdata->mask = tk->clock->mask;
+ vdata->mult = tk->mult;
+ vdata->shift = tk->shift;

vdata->wall_time_sec = tk->xtime_sec;
vdata->wall_time_snsec = tk->xtime_nsec;
@@ -49,12 +51,19 @@ void update_vsyscall(struct timekeeper *tk)
vdata->monotonic_time_sec++;
}

- vdata->wall_time_coarse.tv_sec = tk->xtime_sec;
- vdata->wall_time_coarse.tv_nsec = (long)(tk->xtime_nsec >> tk->shift);
+ vdata->wall_time_coarse_sec = tk->xtime_sec;
+ vdata->wall_time_coarse_nsec = (long)(tk->xtime_nsec >> tk->shift);

- vdata->monotonic_time_coarse = timespec_add(vdata->wall_time_coarse,
- tk->wall_to_monotonic);
+ vdata->monotonic_time_coarse_sec =
+ vdata->wall_time_coarse_sec + tk->wall_to_monotonic.tv_sec;
+ vdata->monotonic_time_coarse_nsec =
+ vdata->wall_time_coarse_nsec + tk->wall_to_monotonic.tv_nsec;

- write_seqcount_end(&vdata->seq);
+ while (vdata->monotonic_time_coarse_nsec >= NSEC_PER_SEC) {
+ vdata->monotonic_time_coarse_nsec -= NSEC_PER_SEC;
+ vdata->monotonic_time_coarse_sec++;
+ }
+
+ gtod_write_end(vdata);
}

diff --git a/arch/x86/vdso/vclock_gettime.c b/arch/x86/vdso/vclock_gettime.c
index 0511e3d..c1d9346 100644
--- a/arch/x86/vdso/vclock_gettime.c
+++ b/arch/x86/vdso/vclock_gettime.c
@@ -74,13 +74,12 @@ notrace static long vdso_fallback_gettime(long clock, struct timespec *ts)
"call VDSO32_vsyscall \n"
"pop %%ebx \n"
: "=a" (ret)
- : "0" (__NR_clock_gettime), "d" (clock), "c" (ts)
+ : "0" (__NR_ia32_clock_gettime), "d" (clock), "c" (ts)
: "memory");
return ret;
}

-notrace static long vdso_fallback_gtod(struct timeval *tv,
- struct timezone *tz)
+notrace static long vdso_fallback_gtod(struct timeval *tv, struct timezone *tz)
{
long ret;

@@ -90,7 +89,7 @@ notrace static long vdso_fallback_gtod(struct timeval *tv,
"call VDSO32_vsyscall \n"
"pop %%ebx \n"
: "=a" (ret)
- : "0" (__NR_gettimeofday), "d" (tv), "c" (tz)
+ : "0" (__NR_ia32_gettimeofday), "d" (tv), "c" (tz)
: "memory");
return ret;
}
@@ -157,7 +156,7 @@ static notrace cycle_t vread_pvclock(int *mode)
*mode = VCLOCK_NONE;

/* refer to tsc.c read_tsc() comment for rationale */
- last = gtod->clock.cycle_last;
+ last = gtod->cycle_last;

if (likely(ret >= last))
return ret;
@@ -181,7 +180,7 @@ notrace static cycle_t vread_tsc(void)
rdtsc_barrier();
ret = (cycle_t)vget_cycles();

- last = gtod->clock.cycle_last;
+ last = gtod->cycle_last;

if (likely(ret >= last))
return ret;
@@ -202,20 +201,20 @@ notrace static inline u64 vgetsns(int *mode)
{
u64 v;
cycles_t cycles;
- if (gtod->clock.vclock_mode == VCLOCK_TSC)
+ if (gtod->vclock_mode == VCLOCK_TSC)
cycles = vread_tsc();
#ifdef CONFIG_HPET_TIMER
- else if (gtod->clock.vclock_mode == VCLOCK_HPET)
+ else if (gtod->vclock_mode == VCLOCK_HPET)
cycles = vread_hpet();
#endif
#ifdef CONFIG_PARAVIRT_CLOCK
- else if (gtod->clock.vclock_mode == VCLOCK_PVCLOCK)
+ else if (gtod->vclock_mode == VCLOCK_PVCLOCK)
cycles = vread_pvclock(mode);
#endif
else
return 0;
- v = (cycles - gtod->clock.cycle_last) & gtod->clock.mask;
- return v * gtod->clock.mult;
+ v = (cycles - gtod->cycle_last) & gtod->mask;
+ return v * gtod->mult;
}

/* Code size doesn't matter (vdso is 4k anyway) and this is faster. */
@@ -225,17 +224,18 @@ notrace static int __always_inline do_realtime(struct timespec *ts)
u64 ns;
int mode;

- ts->tv_nsec = 0;
do {
- seq = raw_read_seqcount_begin(&gtod->seq);
- mode = gtod->clock.vclock_mode;
+ 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->clock.shift;
- } while (unlikely(read_seqcount_retry(&gtod->seq, seq)));
+ 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;

- timespec_add_ns(ts, ns);
return mode;
}

@@ -245,16 +245,17 @@ notrace static int do_monotonic(struct timespec *ts)
u64 ns;
int mode;

- ts->tv_nsec = 0;
do {
- seq = raw_read_seqcount_begin(&gtod->seq);
- mode = gtod->clock.vclock_mode;
+ 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->clock.shift;
- } while (unlikely(read_seqcount_retry(&gtod->seq, seq)));
- timespec_add_ns(ts, ns);
+ 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;
}
@@ -263,20 +264,20 @@ notrace static void do_realtime_coarse(struct timespec *ts)
{
unsigned long seq;
do {
- seq = raw_read_seqcount_begin(&gtod->seq);
- ts->tv_sec = gtod->wall_time_coarse.tv_sec;
- ts->tv_nsec = gtod->wall_time_coarse.tv_nsec;
- } while (unlikely(read_seqcount_retry(&gtod->seq, seq)));
+ 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 = raw_read_seqcount_begin(&gtod->seq);
- ts->tv_sec = gtod->monotonic_time_coarse.tv_sec;
- ts->tv_nsec = gtod->monotonic_time_coarse.tv_nsec;
- } while (unlikely(read_seqcount_retry(&gtod->seq, seq)));
+ 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)
@@ -310,17 +311,13 @@ int clock_gettime(clockid_t, struct timespec *)
notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
{
if (likely(tv != NULL)) {
- BUILD_BUG_ON(offsetof(struct timeval, tv_usec) !=
- offsetof(struct timespec, tv_nsec) ||
- sizeof(*tv) != sizeof(struct timespec));
if (unlikely(do_realtime((struct timespec *)tv) == VCLOCK_NONE))
return vdso_fallback_gtod(tv, tz);
tv->tv_usec /= 1000;
}
if (unlikely(tz != NULL)) {
- /* Avoid memcpy. Some old compilers fail to inline it */
- tz->tz_minuteswest = gtod->sys_tz.tz_minuteswest;
- tz->tz_dsttime = gtod->sys_tz.tz_dsttime;
+ tz->tz_minuteswest = gtod->tz_minuteswest;
+ tz->tz_dsttime = gtod->tz_dsttime;
}

return 0;
diff --git a/arch/x86/vdso/vdso32/vclock_gettime.c b/arch/x86/vdso/vdso32/vclock_gettime.c
index fab4ec6..b6df952 100644
--- a/arch/x86/vdso/vdso32/vclock_gettime.c
+++ b/arch/x86/vdso/vdso32/vclock_gettime.c
@@ -2,6 +2,8 @@

#ifdef CONFIG_X86_64

+#include <generated/asm/unistd_32_ia32.h>
+
#define _ASM_X86_PAGE_H

#define __pa(x) 0
@@ -10,6 +12,11 @@
#undef CONFIG_ILLEGAL_POINTER_VALUE
#define CONFIG_ILLEGAL_POINTER_VALUE 0

+#else
+
+#define __NR_ia32_clock_gettime __NR_clock_gettime
+#define __NR_ia32_gettimeofday __NR_gettimeofday
+
#endif

#include "../vclock_gettime.c"
--
1.8.5.4


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