[PATCH v12 9/9] Add 32 bit VDSO time support for 64 bit kernel

[stefani@seibold.net]

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.

The vsyscall_gtod_data struture must be a little bit rearranged, to
serve 32- and 64-bit code access:

- The seqcount_t was replaced by an unsigned, this makes the
  vsyscall_gtod_data intedepend of kernel configuration and internal functions.
- The structure is now packed, so it can accessed from 32- und 64- bit
  code at the same time.
- The inner struct clock was removed, to make packing of the while
  struct easier.

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          |  20 +++---
 arch/x86/kernel/vsyscall_gtod.c       |  26 +++++--
 arch/x86/vdso/vclock_gettime.c        | 129 ++++++++++++++++++++++++----------
 arch/x86/vdso/vdso32/vclock_gettime.c |  11 +++
 include/uapi/linux/time.h             |   2 +-
 5 files changed, 132 insertions(+), 56 deletions(-)

diff --git a/arch/x86/include/asm/vgtod.h b/arch/x86/include/asm/vgtod.h
index 46e24d3..2567b02 100644
--- a/arch/x86/include/asm/vgtod.h
+++ b/arch/x86/include/asm/vgtod.h
@@ -4,16 +4,18 @@
 #include <asm/vsyscall.h>
 #include <linux/clocksource.h>
 
-struct vsyscall_gtod_data {
-	seqcount_t	seq;
+/*
+ * vsyscall_gtod_data will be accessed by 32 and 64 bit code at the same time
+ * so the structure must be packed
+ */
+struct __attribute__((packed)) vsyscall_gtod_data {
+	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;
diff --git a/arch/x86/kernel/vsyscall_gtod.c b/arch/x86/kernel/vsyscall_gtod.c
index 91862a4..ca48248 100644
--- a/arch/x86/kernel/vsyscall_gtod.c
+++ b/arch/x86/kernel/vsyscall_gtod.c
@@ -16,6 +16,18 @@
 
 DEFINE_VVAR(struct vsyscall_gtod_data, vsyscall_gtod_data);
 
+static inline void gtod_write_begin(unsigned *s)
+{
+	++*s;
+	smp_wmb();
+}
+
+static inline void gtod_write_end(unsigned *s)
+{
+	smp_wmb();
+	++*s;
+}
+
 void update_vsyscall_tz(void)
 {
 	vsyscall_gtod_data.sys_tz = sys_tz;
@@ -25,14 +37,14 @@ void update_vsyscall(struct timekeeper *tk)
 {
 	struct vsyscall_gtod_data *vdata = &vsyscall_gtod_data;
 
-	write_seqcount_begin(&vdata->seq);
+	gtod_write_begin(&vdata->seq);
 
 	/* 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;
@@ -55,6 +67,6 @@ void update_vsyscall(struct timekeeper *tk)
 	vdata->monotonic_time_coarse	= timespec_add(vdata->wall_time_coarse,
 							tk->wall_to_monotonic);
 
-	write_seqcount_end(&vdata->seq);
+	gtod_write_end(&vdata->seq);
 }
 
diff --git a/arch/x86/vdso/vclock_gettime.c b/arch/x86/vdso/vclock_gettime.c
index 469e57b..b045aaa 100644
--- a/arch/x86/vdso/vclock_gettime.c
+++ b/arch/x86/vdso/vclock_gettime.c
@@ -31,12 +31,24 @@
 
 #ifndef BUILD_VDSO32
 
+struct api_timeval {
+	long	tv_sec;		/* seconds */
+	long	tv_usec;	/* microseconds */
+};
+
+struct api_timespec {
+	long	tv_sec;		/* seconds */
+	long	tv_nsec;	/* nanoseconds */
+};
+
+typedef long api_time_t;
+
 static notrace cycle_t vread_hpet(void)
 {
 	return readl((const void __iomem *)fix_to_virt(VSYSCALL_HPET) + HPET_COUNTER);
 }
 
-notrace static long vdso_fallback_gettime(long clock, struct timespec *ts)
+notrace static long vdso_fallback_gettime(long clock, struct api_timespec *ts)
 {
 	long ret;
 	asm("syscall" : "=a" (ret) :
@@ -44,7 +56,8 @@ notrace static long vdso_fallback_gettime(long clock, struct timespec *ts)
 	return ret;
 }
 
-notrace static long vdso_fallback_gtod(struct timeval *tv, struct timezone *tz)
+notrace static long vdso_fallback_gtod(struct api_timeval *tv,
+		struct timezone *tz)
 {
 	long ret;
 
@@ -57,6 +70,18 @@ notrace static long vdso_fallback_gtod(struct timeval *tv, struct timezone *tz)
 u8 hpet_page
 	__attribute__((visibility("hidden")));
 
+struct api_timeval {
+	s32	tv_sec;		/* seconds */
+	s32	tv_usec;	/* microseconds */
+};
+
+struct api_timespec {
+	s32	tv_sec;		/* seconds */
+	s32	tv_nsec;	/* microseconds */
+};
+
+typedef s32 api_time_t;
+
 #ifdef CONFIG_HPET_TIMER
 static notrace cycle_t vread_hpet(void)
 {
@@ -64,7 +89,7 @@ static notrace cycle_t vread_hpet(void)
 }
 #endif
 
-notrace static long vdso_fallback_gettime(long clock, struct timespec *ts)
+notrace static long vdso_fallback_gettime(long clock, struct api_timespec *ts)
 {
 	long ret;
 
@@ -74,12 +99,12 @@ 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,
+notrace static long vdso_fallback_gtod(struct api_timeval *tv,
 		struct timezone *tz)
 {
 	long ret;
@@ -90,7 +115,7 @@ 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 +182,7 @@ 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 +206,7 @@ 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 +227,40 @@ 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;
+}
+
+notrace static unsigned gtod_read_begin(const unsigned *s)
+{
+	unsigned ret;
+
+repeat:
+	ret = ACCESS_ONCE(*s);
+	if (unlikely(ret & 1)) {
+		cpu_relax();
+		goto repeat;
+	}
+	smp_rmb();
+	return ret;
+}
+
+notrace static int gtod_read_retry(const unsigned *s, unsigned start)
+{
+	smp_rmb();
+	return unlikely(*s != start);
 }
 
 /* Code size doesn't matter (vdso is 4k anyway) and this is faster. */
@@ -227,13 +272,13 @@ notrace static int __always_inline do_realtime(struct timespec *ts)
 
 	ts->tv_nsec = 0;
 	do {
-		seq = raw_read_seqcount_begin(&gtod->seq);
-		mode = gtod->clock.vclock_mode;
+		seq = gtod_read_begin(&gtod->seq);
+		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, seq)));
 
 	timespec_add_ns(ts, ns);
 	return mode;
@@ -247,13 +292,13 @@ notrace static int do_monotonic(struct timespec *ts)
 
 	ts->tv_nsec = 0;
 	do {
-		seq = raw_read_seqcount_begin(&gtod->seq);
-		mode = gtod->clock.vclock_mode;
+		seq = gtod_read_begin(&gtod->seq);
+		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)));
+		ns >>= gtod->shift;
+	} while (unlikely(gtod_read_retry(&gtod->seq, seq)));
 	timespec_add_ns(ts, ns);
 
 	return mode;
@@ -263,58 +308,64 @@ notrace static void do_realtime_coarse(struct timespec *ts)
 {
 	unsigned long seq;
 	do {
-		seq = raw_read_seqcount_begin(&gtod->seq);
+		seq = gtod_read_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)));
+	} while (unlikely(gtod_read_retry(&gtod->seq, seq)));
 }
 
 notrace static void do_monotonic_coarse(struct timespec *ts)
 {
 	unsigned long seq;
 	do {
-		seq = raw_read_seqcount_begin(&gtod->seq);
+		seq = gtod_read_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)));
+	} while (unlikely(gtod_read_retry(&gtod->seq, seq)));
 }
 
-notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
+notrace int __vdso_clock_gettime(clockid_t clock, struct api_timespec *ts)
 {
+	struct timespec tmp;
+
 	switch (clock) {
 	case CLOCK_REALTIME:
-		if (do_realtime(ts) == VCLOCK_NONE)
+		if (do_realtime(&tmp) == VCLOCK_NONE)
 			goto fallback;
 		break;
 	case CLOCK_MONOTONIC:
-		if (do_monotonic(ts) == VCLOCK_NONE)
+		if (do_monotonic(&tmp) == VCLOCK_NONE)
 			goto fallback;
 		break;
 	case CLOCK_REALTIME_COARSE:
-		do_realtime_coarse(ts);
+		do_realtime_coarse(&tmp);
 		break;
 	case CLOCK_MONOTONIC_COARSE:
-		do_monotonic_coarse(ts);
+		do_monotonic_coarse(&tmp);
 		break;
 	default:
 		goto fallback;
 	}
 
+	ts->tv_sec = tmp.tv_sec;
+	ts->tv_nsec = tmp.tv_nsec;
+
 	return 0;
 fallback:
 	return vdso_fallback_gettime(clock, ts);
 }
-int clock_gettime(clockid_t, struct timespec *)
+int clock_gettime(clockid_t, struct api_timespec *)
 	__attribute__((weak, alias("__vdso_clock_gettime")));
 
-notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
+notrace int __vdso_gettimeofday(struct api_timeval *tv, struct timezone *tz)
 {
+	struct timespec tmp;
+
 	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(&tmp) == VCLOCK_NONE))
 			return vdso_fallback_gtod(tv, tz);
+		tv->tv_sec = tmp.tv_sec;
+		tv->tv_usec = tmp.tv_nsec;
 		tv->tv_usec /= 1000;
 	}
 	if (unlikely(tz != NULL)) {
@@ -325,21 +376,21 @@ notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
 
 	return 0;
 }
-int gettimeofday(struct timeval *, struct timezone *)
+int gettimeofday(struct api_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)
+notrace api_time_t __vdso_time(api_time_t *t)
 {
 	/* This is atomic on x86 so we don't need any locks. */
-	time_t result = ACCESS_ONCE(gtod->wall_time_sec);
+	api_time_t result = ACCESS_ONCE(gtod->wall_time_sec);
 
 	if (t)
 		*t = result;
 	return result;
 }
-int time(time_t *t)
+int time(api_time_t *t)
 	__attribute__((weak, alias("__vdso_time")));
diff --git a/arch/x86/vdso/vdso32/vclock_gettime.c b/arch/x86/vdso/vdso32/vclock_gettime.c
index fab4ec6..b8a3b22 100644
--- a/arch/x86/vdso/vdso32/vclock_gettime.c
+++ b/arch/x86/vdso/vdso32/vclock_gettime.c
@@ -2,6 +2,12 @@
 
 #ifdef CONFIG_X86_64
 
+typedef signed long long	__kernel_long_t;
+typedef unsigned long long	__kernel_ulong_t;
+#define __kernel_long_t __kernel_long_t
+
+#include <generated/asm/unistd_32_ia32.h>
+
 #define _ASM_X86_PAGE_H
 
 #define __pa(x)                0
@@ -10,6 +16,11 @@
 #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"
diff --git a/include/uapi/linux/time.h b/include/uapi/linux/time.h
index e75e1b6..ebf3734 100644
--- a/include/uapi/linux/time.h
+++ b/include/uapi/linux/time.h
@@ -8,7 +8,7 @@
 #define _STRUCT_TIMESPEC
 struct timespec {
 	__kernel_time_t	tv_sec;			/* seconds */
-	long		tv_nsec;		/* nanoseconds */
+	__kernel_long_t	tv_nsec;		/* nanoseconds */
 };
 #endif
 
-- 
1.8.5.3