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Subject[PATCH v16 09/10] Add 32 bit VDSO time support for 64 bit kernel
Date
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.

Signed-off-by: Stefani Seibold <stefani@seibold.net>
---
arch/x86/include/asm/vgtod.h | 69 ++++++++++++++++++++++++++++-------
arch/x86/include/asm/vvar.h | 5 +++
arch/x86/kernel/vsyscall_gtod.c | 33 +++++++++++------
arch/x86/vdso/vclock_gettime.c | 68 +++++++++++++++++-----------------
arch/x86/vdso/vdso32/vclock_gettime.c | 13 +++++++
5 files changed, 128 insertions(+), 60 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/include/asm/vvar.h b/arch/x86/include/asm/vvar.h
index 52c79ff..081d909 100644
--- a/arch/x86/include/asm/vvar.h
+++ b/arch/x86/include/asm/vvar.h
@@ -16,6 +16,9 @@
* you mess up, the linker will catch it.)
*/

+#ifndef _ASM_X86_VVAR_H
+#define _ASM_X86_VVAR_H
+
#if defined(__VVAR_KERNEL_LDS)

/* The kernel linker script defines its own magic to put vvars in the
@@ -64,3 +67,5 @@ DECLARE_VVAR(16, int, vgetcpu_mode)
DECLARE_VVAR(128, struct vsyscall_gtod_data, vsyscall_gtod_data)

#undef DECLARE_VVAR
+
+#endif
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 8f1ed88..e1238b9 100644
--- a/arch/x86/vdso/vclock_gettime.c
+++ b/arch/x86/vdso/vclock_gettime.c
@@ -114,7 +114,7 @@ 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;
@@ -145,7 +145,7 @@ notrace static long vdso_fallback_gettime(long clock, struct timespec *ts)
"call VDSO32_vsyscall \n"
"mov %%edx, %%ebx \n"
: "=a" (ret)
- : "0" (__NR_clock_gettime), "g" (clock), "c" (ts)
+ : "0" (__NR_ia32_clock_gettime), "g" (clock), "c" (ts)
: "memory", "edx");
return ret;
}
@@ -160,7 +160,7 @@ notrace static long vdso_fallback_gtod(struct timeval *tv, struct timezone *tz)
"call VDSO32_vsyscall \n"
"mov %%edx, %%ebx \n"
: "=a" (ret)
- : "0" (__NR_gettimeofday), "g" (tv), "c" (tz)
+ : "0" (__NR_ia32_gettimeofday), "g" (tv), "c" (tz)
: "memory", "edx");
return ret;
}
@@ -191,7 +191,7 @@ 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;
@@ -212,20 +212,20 @@ 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. */
@@ -235,17 +235,18 @@ 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;
}

@@ -255,16 +256,17 @@ 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;
}
@@ -273,20 +275,20 @@ 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)
@@ -320,17 +322,13 @@ 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 ffdbdb1..7a73f02 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>
+
/*
* Due the -m32 compilation, there will be a lot of
* "warning: integer constant is too large for 'unsigned long' type",
@@ -24,12 +26,23 @@
#define __va(x) 0

/*
+ * function load_cr3() in x86/include/asm/processor.h depends on __pa().
+ * Replace by a dummy is save since not used
+ */
+#define __pa(x) 0
+
+/*
* The define of CONFIG_ILLEGAL_POINTER_VALUE is also to prevent the
* "warning: integer constant is too large..."
*/
#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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