[PATCH 1/2] vdso: sparc: stub out custom vdso implementation

[PATCH 1/2] vdso: sparc: stub out custom vdso implementation

[Arnd Bergmann]

From: Arnd Bergmann <arnd@arndb.de>

sparc64 is the only remaining architecture that has its own implementation
of the vdso clock_gettime/gettimeofday helpers in place of the generic
code. This causes a number of issues:

 - Changes to the vdso interfaces require adding sparc64 specific hacks
   even when nothing else needs them

 - The prototypes in <vdso/gettime.h> don't match the function implementation,
   and not including that header to avoid the build error from that causes
   another warning:

  arch/sparc/vdso/vclock_gettime.c:274:1: error: no previous prototype for '__vdso_clock_gettime' [-Werror=missing-prototypes]
    274 | __vdso_clock_gettime(clockid_t clock, struct __kernel_old_timespec *ts)
        | ^~~~~~~~~~~~~~~~~~~~

 - Nobody has ever implemented the clock_gettime64() vdso that is required for
   32-bit compat tasks

 - The warning about the missing executable-stack flag was missed:

  sparc-linux-ld: warning: arch/sparc/vdso/vdso-note.o: missing .note.GNU-stack section implies executable stack
  sparc-linux-ld: NOTE: This behaviour is deprecated and will be removed in a future version of the linker

Most of the removed code only exists on sparc in order to dynamically
patch the vdso based on the presence of the tick vs vtick based
clocksource.

Rip out the whole thing and replace it with a minimal stub as we do
on parisc and uml. This introduces a small performance regression when
using a libc that is aware of the vdso (glibc-2.29 or higher).

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 arch/sparc/Kconfig                  |   1 -
 arch/sparc/include/asm/vvar.h       |  75 ------
 arch/sparc/kernel/Makefile          |   1 -
 arch/sparc/kernel/vdso.c            |  69 ------
 arch/sparc/vdso/Makefile            |   2 +-
 arch/sparc/vdso/vclock_gettime.c    | 341 +++-------------------------
 arch/sparc/vdso/vdso.lds.S          |   2 -
 arch/sparc/vdso/vdso32/vdso32.lds.S |   3 +-
 arch/sparc/vdso/vma.c               | 265 +--------------------
 9 files changed, 31 insertions(+), 728 deletions(-)
 delete mode 100644 arch/sparc/include/asm/vvar.h
 delete mode 100644 arch/sparc/kernel/vdso.c

diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
index dcfdb7f1dae9..776ce79ef188 100644
--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -101,7 +101,6 @@ config SPARC64
 	select HAVE_REGS_AND_STACK_ACCESS_API
 	select ARCH_USE_QUEUED_RWLOCKS
 	select ARCH_USE_QUEUED_SPINLOCKS
-	select GENERIC_TIME_VSYSCALL
 	select ARCH_CLOCKSOURCE_DATA
 	select ARCH_HAS_PTE_SPECIAL
 	select PCI_DOMAINS if PCI
diff --git a/arch/sparc/include/asm/vvar.h b/arch/sparc/include/asm/vvar.h
deleted file mode 100644
index 6eaf5cfcaae1..000000000000
--- a/arch/sparc/include/asm/vvar.h
+++ /dev/null
@@ -1,75 +0,0 @@
-/*
- * Copyright (c) 2017 Oracle and/or its affiliates. All rights reserved.
- */
-
-#ifndef _ASM_SPARC_VVAR_DATA_H
-#define _ASM_SPARC_VVAR_DATA_H
-
-#include <asm/clocksource.h>
-#include <asm/processor.h>
-#include <asm/barrier.h>
-#include <linux/time.h>
-#include <linux/types.h>
-
-struct vvar_data {
-	unsigned int seq;
-
-	int vclock_mode;
-	struct { /* extract of a clocksource struct */
-		u64	cycle_last;
-		u64	mask;
-		int	mult;
-		int	shift;
-	} clock;
-	/* open coded 'struct timespec' */
-	u64		wall_time_sec;
-	u64		wall_time_snsec;
-	u64		monotonic_time_snsec;
-	u64		monotonic_time_sec;
-	u64		monotonic_time_coarse_sec;
-	u64		monotonic_time_coarse_nsec;
-	u64		wall_time_coarse_sec;
-	u64		wall_time_coarse_nsec;
-
-	int		tz_minuteswest;
-	int		tz_dsttime;
-};
-
-extern struct vvar_data *vvar_data;
-extern int vdso_fix_stick;
-
-static inline unsigned int vvar_read_begin(const struct vvar_data *s)
-{
-	unsigned int ret;
-
-repeat:
-	ret = READ_ONCE(s->seq);
-	if (unlikely(ret & 1)) {
-		cpu_relax();
-		goto repeat;
-	}
-	smp_rmb(); /* Finish all reads before we return seq */
-	return ret;
-}
-
-static inline int vvar_read_retry(const struct vvar_data *s,
-					unsigned int start)
-{
-	smp_rmb(); /* Finish all reads before checking the value of seq */
-	return unlikely(s->seq != start);
-}
-
-static inline void vvar_write_begin(struct vvar_data *s)
-{
-	++s->seq;
-	smp_wmb(); /* Makes sure that increment of seq is reflected */
-}
-
-static inline void vvar_write_end(struct vvar_data *s)
-{
-	smp_wmb(); /* Makes the value of seq current before we increment */
-	++s->seq;
-}
-
-
-#endif /* _ASM_SPARC_VVAR_DATA_H */
diff --git a/arch/sparc/kernel/Makefile b/arch/sparc/kernel/Makefile
index 36f2727e1445..7a063cd4b6d3 100644
--- a/arch/sparc/kernel/Makefile
+++ b/arch/sparc/kernel/Makefile
@@ -43,7 +43,6 @@ obj-$(CONFIG_SPARC32)   += systbls_32.o
 obj-y                   += time_$(BITS).o
 obj-$(CONFIG_SPARC32)   += windows.o
 obj-y                   += cpu.o
-obj-$(CONFIG_SPARC64)	+= vdso.o
 obj-$(CONFIG_SPARC32)   += devices.o
 obj-y                   += ptrace_$(BITS).o
 obj-y                   += unaligned_$(BITS).o
diff --git a/arch/sparc/kernel/vdso.c b/arch/sparc/kernel/vdso.c
deleted file mode 100644
index 0e27437eb97b..000000000000
--- a/arch/sparc/kernel/vdso.c
+++ /dev/null
@@ -1,69 +0,0 @@
-/*
- *  Copyright (C) 2001 Andrea Arcangeli <andrea@suse.de> SuSE
- *  Copyright 2003 Andi Kleen, SuSE Labs.
- *
- *  Thanks to hpa@transmeta.com for some useful hint.
- *  Special thanks to Ingo Molnar for his early experience with
- *  a different vsyscall implementation for Linux/IA32 and for the name.
- */
-
-#include <linux/time.h>
-#include <linux/timekeeper_internal.h>
-
-#include <asm/vvar.h>
-
-void update_vsyscall_tz(void)
-{
-	if (unlikely(vvar_data == NULL))
-		return;
-
-	vvar_data->tz_minuteswest = sys_tz.tz_minuteswest;
-	vvar_data->tz_dsttime = sys_tz.tz_dsttime;
-}
-
-void update_vsyscall(struct timekeeper *tk)
-{
-	struct vvar_data *vdata = vvar_data;
-
-	if (unlikely(vdata == NULL))
-		return;
-
-	vvar_write_begin(vdata);
-	vdata->vclock_mode = tk->tkr_mono.clock->archdata.vclock_mode;
-	vdata->clock.cycle_last = tk->tkr_mono.cycle_last;
-	vdata->clock.mask = tk->tkr_mono.mask;
-	vdata->clock.mult = tk->tkr_mono.mult;
-	vdata->clock.shift = tk->tkr_mono.shift;
-
-	vdata->wall_time_sec = tk->xtime_sec;
-	vdata->wall_time_snsec = tk->tkr_mono.xtime_nsec;
-
-	vdata->monotonic_time_sec = tk->xtime_sec +
-				    tk->wall_to_monotonic.tv_sec;
-	vdata->monotonic_time_snsec = tk->tkr_mono.xtime_nsec +
-				      (tk->wall_to_monotonic.tv_nsec <<
-				       tk->tkr_mono.shift);
-
-	while (vdata->monotonic_time_snsec >=
-	       (((u64)NSEC_PER_SEC) << tk->tkr_mono.shift)) {
-		vdata->monotonic_time_snsec -=
-				((u64)NSEC_PER_SEC) << tk->tkr_mono.shift;
-		vdata->monotonic_time_sec++;
-	}
-
-	vdata->wall_time_coarse_sec = tk->xtime_sec;
-	vdata->wall_time_coarse_nsec =
-			(long)(tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift);
-
-	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;
-
-	while (vdata->monotonic_time_coarse_nsec >= NSEC_PER_SEC) {
-		vdata->monotonic_time_coarse_nsec -= NSEC_PER_SEC;
-		vdata->monotonic_time_coarse_sec++;
-	}
-
-	vvar_write_end(vdata);
-}
diff --git a/arch/sparc/vdso/Makefile b/arch/sparc/vdso/Makefile
index fdc4a8f5a49c..e8315c6acb74 100644
--- a/arch/sparc/vdso/Makefile
+++ b/arch/sparc/vdso/Makefile
@@ -103,4 +103,4 @@ quiet_cmd_vdso = VDSO    $@
 		       $(VDSO_LDFLAGS) $(VDSO_LDFLAGS_$(filter %.lds,$(^F))) \
 		       -T $(filter %.lds,$^) $(filter %.o,$^)
 
-VDSO_LDFLAGS = -shared --hash-style=both --build-id=sha1 -Bsymbolic --no-undefined
+VDSO_LDFLAGS = -shared --hash-style=both --build-id=sha1 -Bsymbolic --no-undefined -z noexecstack
diff --git a/arch/sparc/vdso/vclock_gettime.c b/arch/sparc/vdso/vclock_gettime.c
index 79607804ea1b..8b4773fa782c 100644
--- a/arch/sparc/vdso/vclock_gettime.c
+++ b/arch/sparc/vdso/vclock_gettime.c
@@ -15,11 +15,8 @@
 #include <linux/kernel.h>
 #include <linux/time.h>
 #include <linux/string.h>
-#include <asm/io.h>
 #include <asm/unistd.h>
-#include <asm/timex.h>
-#include <asm/clocksource.h>
-#include <asm/vvar.h>
+#include <vdso/gettime.h>
 
 #ifdef	CONFIG_SPARC64
 #define SYSCALL_STRING							\
@@ -44,26 +41,9 @@
 	"f48", "f50", "f52", "f54", "f56", "f58", "f60", "f62",		\
 	"cc", "memory"
 
-/*
- * Compute the vvar page's address in the process address space, and return it
- * as a pointer to the vvar_data.
- */
-notrace static __always_inline struct vvar_data *get_vvar_data(void)
-{
-	unsigned long ret;
-
-	/*
-	 * vdso data page is the first vDSO page so grab the PC
-	 * and move up a page to get to the data page.
-	 */
-	__asm__("rd %%pc, %0" : "=r" (ret));
-	ret &= ~(8192 - 1);
-	ret -= 8192;
-
-	return (struct vvar_data *) ret;
-}
-
-notrace static long vdso_fallback_gettime(long clock, struct __kernel_old_timespec *ts)
+#if !defined(CONFIG_64BIT) || defined(BUILD_VDSO32_64)
+notrace int
+__vdso_clock_gettime(clockid_t clock, struct old_timespec32 *ts)
 {
 	register long num __asm__("g1") = __NR_clock_gettime;
 	register long o0 __asm__("o0") = clock;
@@ -74,320 +54,51 @@ notrace static long vdso_fallback_gettime(long clock, struct __kernel_old_timesp
 	return o0;
 }
 
-notrace static long vdso_fallback_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz)
+notrace int
+__vdso_clock_gettime64(clockid_t clock, struct __kernel_timespec *ts)
 {
-	register long num __asm__("g1") = __NR_gettimeofday;
-	register long o0 __asm__("o0") = (long) tv;
-	register long o1 __asm__("o1") = (long) tz;
+	register long num __asm__("g1") = __NR_clock_gettime64;
+	register long o0 __asm__("o0") = clock;
+	register long o1 __asm__("o1") = (long) ts;
 
 	__asm__ __volatile__(SYSCALL_STRING : "=r" (o0) : "r" (num),
 			     "0" (o0), "r" (o1) : SYSCALL_CLOBBERS);
 	return o0;
 }
 
-#ifdef	CONFIG_SPARC64
-notrace static __always_inline u64 __shr64(u64 val, int amt)
-{
-	return val >> amt;
-}
-
-notrace static __always_inline u64 vread_tick(void)
-{
-	u64	ret;
-
-	__asm__ __volatile__("rd %%tick, %0" : "=r" (ret));
-	return ret;
-}
-
-notrace static __always_inline u64 vread_tick_stick(void)
-{
-	u64	ret;
+int
+clock_gettime64(clockid_t, struct __kernel_timespec *)
+	__attribute__((weak, alias("__vdso_clock_gettime64")));
 
-	__asm__ __volatile__("rd %%asr24, %0" : "=r" (ret));
-	return ret;
-}
 #else
-notrace static __always_inline u64 __shr64(u64 val, int amt)
-{
-	u64 ret;
-
-	__asm__ __volatile__("sllx %H1, 32, %%g1\n\t"
-			     "srl %L1, 0, %L1\n\t"
-			     "or %%g1, %L1, %%g1\n\t"
-			     "srlx %%g1, %2, %L0\n\t"
-			     "srlx %L0, 32, %H0"
-			     : "=r" (ret)
-			     : "r" (val), "r" (amt)
-			     : "g1");
-	return ret;
-}
-
-notrace static __always_inline u64 vread_tick(void)
-{
-	register unsigned long long ret asm("o4");
-
-	__asm__ __volatile__("rd %%tick, %L0\n\t"
-			     "srlx %L0, 32, %H0"
-			     : "=r" (ret));
-	return ret;
-}
-
-notrace static __always_inline u64 vread_tick_stick(void)
+notrace int
+__vdso_clock_gettime(clockid_t clock, struct __kernel_timespec *ts)
 {
-	register unsigned long long ret asm("o4");
+	register long num __asm__("g1") = __NR_clock_gettime;
+	register long o0 __asm__("o0") = clock;
+	register long o1 __asm__("o1") = (long) ts;
 
-	__asm__ __volatile__("rd %%asr24, %L0\n\t"
-			     "srlx %L0, 32, %H0"
-			     : "=r" (ret));
-	return ret;
+	__asm__ __volatile__(SYSCALL_STRING : "=r" (o0) : "r" (num),
+			     "0" (o0), "r" (o1) : SYSCALL_CLOBBERS);
+	return o0;
 }
 #endif
 
-notrace static __always_inline u64 vgetsns(struct vvar_data *vvar)
-{
-	u64 v;
-	u64 cycles;
-
-	cycles = vread_tick();
-	v = (cycles - vvar->clock.cycle_last) & vvar->clock.mask;
-	return v * vvar->clock.mult;
-}
-
-notrace static __always_inline u64 vgetsns_stick(struct vvar_data *vvar)
-{
-	u64 v;
-	u64 cycles;
-
-	cycles = vread_tick_stick();
-	v = (cycles - vvar->clock.cycle_last) & vvar->clock.mask;
-	return v * vvar->clock.mult;
-}
-
-notrace static __always_inline int do_realtime(struct vvar_data *vvar,
-					       struct __kernel_old_timespec *ts)
-{
-	unsigned long seq;
-	u64 ns;
-
-	do {
-		seq = vvar_read_begin(vvar);
-		ts->tv_sec = vvar->wall_time_sec;
-		ns = vvar->wall_time_snsec;
-		ns += vgetsns(vvar);
-		ns = __shr64(ns, vvar->clock.shift);
-	} while (unlikely(vvar_read_retry(vvar, seq)));
-
-	ts->tv_sec += __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
-	ts->tv_nsec = ns;
-
-	return 0;
-}
-
-notrace static __always_inline int do_realtime_stick(struct vvar_data *vvar,
-						     struct __kernel_old_timespec *ts)
-{
-	unsigned long seq;
-	u64 ns;
-
-	do {
-		seq = vvar_read_begin(vvar);
-		ts->tv_sec = vvar->wall_time_sec;
-		ns = vvar->wall_time_snsec;
-		ns += vgetsns_stick(vvar);
-		ns = __shr64(ns, vvar->clock.shift);
-	} while (unlikely(vvar_read_retry(vvar, seq)));
-
-	ts->tv_sec += __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
-	ts->tv_nsec = ns;
-
-	return 0;
-}
-
-notrace static __always_inline int do_monotonic(struct vvar_data *vvar,
-						struct __kernel_old_timespec *ts)
-{
-	unsigned long seq;
-	u64 ns;
-
-	do {
-		seq = vvar_read_begin(vvar);
-		ts->tv_sec = vvar->monotonic_time_sec;
-		ns = vvar->monotonic_time_snsec;
-		ns += vgetsns(vvar);
-		ns = __shr64(ns, vvar->clock.shift);
-	} while (unlikely(vvar_read_retry(vvar, seq)));
-
-	ts->tv_sec += __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
-	ts->tv_nsec = ns;
-
-	return 0;
-}
-
-notrace static __always_inline int do_monotonic_stick(struct vvar_data *vvar,
-						      struct __kernel_old_timespec *ts)
-{
-	unsigned long seq;
-	u64 ns;
-
-	do {
-		seq = vvar_read_begin(vvar);
-		ts->tv_sec = vvar->monotonic_time_sec;
-		ns = vvar->monotonic_time_snsec;
-		ns += vgetsns_stick(vvar);
-		ns = __shr64(ns, vvar->clock.shift);
-	} while (unlikely(vvar_read_retry(vvar, seq)));
-
-	ts->tv_sec += __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
-	ts->tv_nsec = ns;
-
-	return 0;
-}
-
-notrace static int do_realtime_coarse(struct vvar_data *vvar,
-				      struct __kernel_old_timespec *ts)
-{
-	unsigned long seq;
-
-	do {
-		seq = vvar_read_begin(vvar);
-		ts->tv_sec = vvar->wall_time_coarse_sec;
-		ts->tv_nsec = vvar->wall_time_coarse_nsec;
-	} while (unlikely(vvar_read_retry(vvar, seq)));
-	return 0;
-}
-
-notrace static int do_monotonic_coarse(struct vvar_data *vvar,
-				       struct __kernel_old_timespec *ts)
-{
-	unsigned long seq;
-
-	do {
-		seq = vvar_read_begin(vvar);
-		ts->tv_sec = vvar->monotonic_time_coarse_sec;
-		ts->tv_nsec = vvar->monotonic_time_coarse_nsec;
-	} while (unlikely(vvar_read_retry(vvar, seq)));
-
-	return 0;
-}
-
-notrace int
-__vdso_clock_gettime(clockid_t clock, struct __kernel_old_timespec *ts)
-{
-	struct vvar_data *vvd = get_vvar_data();
-
-	switch (clock) {
-	case CLOCK_REALTIME:
-		if (unlikely(vvd->vclock_mode == VCLOCK_NONE))
-			break;
-		return do_realtime(vvd, ts);
-	case CLOCK_MONOTONIC:
-		if (unlikely(vvd->vclock_mode == VCLOCK_NONE))
-			break;
-		return do_monotonic(vvd, ts);
-	case CLOCK_REALTIME_COARSE:
-		return do_realtime_coarse(vvd, ts);
-	case CLOCK_MONOTONIC_COARSE:
-		return do_monotonic_coarse(vvd, ts);
-	}
-	/*
-	 * Unknown clock ID ? Fall back to the syscall.
-	 */
-	return vdso_fallback_gettime(clock, ts);
-}
 int
 clock_gettime(clockid_t, struct __kernel_old_timespec *)
 	__attribute__((weak, alias("__vdso_clock_gettime")));
 
-notrace int
-__vdso_clock_gettime_stick(clockid_t clock, struct __kernel_old_timespec *ts)
-{
-	struct vvar_data *vvd = get_vvar_data();
-
-	switch (clock) {
-	case CLOCK_REALTIME:
-		if (unlikely(vvd->vclock_mode == VCLOCK_NONE))
-			break;
-		return do_realtime_stick(vvd, ts);
-	case CLOCK_MONOTONIC:
-		if (unlikely(vvd->vclock_mode == VCLOCK_NONE))
-			break;
-		return do_monotonic_stick(vvd, ts);
-	case CLOCK_REALTIME_COARSE:
-		return do_realtime_coarse(vvd, ts);
-	case CLOCK_MONOTONIC_COARSE:
-		return do_monotonic_coarse(vvd, ts);
-	}
-	/*
-	 * Unknown clock ID ? Fall back to the syscall.
-	 */
-	return vdso_fallback_gettime(clock, ts);
-}
-
 notrace int
 __vdso_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz)
 {
-	struct vvar_data *vvd = get_vvar_data();
+	register long num __asm__("g1") = __NR_gettimeofday;
+	register long o0 __asm__("o0") = (long) tv;
+	register long o1 __asm__("o1") = (long) tz;
 
-	if (likely(vvd->vclock_mode != VCLOCK_NONE)) {
-		if (likely(tv != NULL)) {
-			union tstv_t {
-				struct __kernel_old_timespec ts;
-				struct __kernel_old_timeval tv;
-			} *tstv = (union tstv_t *) tv;
-			do_realtime(vvd, &tstv->ts);
-			/*
-			 * Assign before dividing to ensure that the division is
-			 * done in the type of tv_usec, not tv_nsec.
-			 *
-			 * There cannot be > 1 billion usec in a second:
-			 * do_realtime() has already distributed such overflow
-			 * into tv_sec.  So we can assign it to an int safely.
-			 */
-			tstv->tv.tv_usec = tstv->ts.tv_nsec;
-			tstv->tv.tv_usec /= 1000;
-		}
-		if (unlikely(tz != NULL)) {
-			/* Avoid memcpy. Some old compilers fail to inline it */
-			tz->tz_minuteswest = vvd->tz_minuteswest;
-			tz->tz_dsttime = vvd->tz_dsttime;
-		}
-		return 0;
-	}
-	return vdso_fallback_gettimeofday(tv, tz);
+	__asm__ __volatile__(SYSCALL_STRING : "=r" (o0) : "r" (num),
+			     "0" (o0), "r" (o1) : SYSCALL_CLOBBERS);
+	return o0;
 }
 int
 gettimeofday(struct __kernel_old_timeval *, struct timezone *)
 	__attribute__((weak, alias("__vdso_gettimeofday")));
-
-notrace int
-__vdso_gettimeofday_stick(struct __kernel_old_timeval *tv, struct timezone *tz)
-{
-	struct vvar_data *vvd = get_vvar_data();
-
-	if (likely(vvd->vclock_mode != VCLOCK_NONE)) {
-		if (likely(tv != NULL)) {
-			union tstv_t {
-				struct __kernel_old_timespec ts;
-				struct __kernel_old_timeval tv;
-			} *tstv = (union tstv_t *) tv;
-			do_realtime_stick(vvd, &tstv->ts);
-			/*
-			 * Assign before dividing to ensure that the division is
-			 * done in the type of tv_usec, not tv_nsec.
-			 *
-			 * There cannot be > 1 billion usec in a second:
-			 * do_realtime() has already distributed such overflow
-			 * into tv_sec.  So we can assign it to an int safely.
-			 */
-			tstv->tv.tv_usec = tstv->ts.tv_nsec;
-			tstv->tv.tv_usec /= 1000;
-		}
-		if (unlikely(tz != NULL)) {
-			/* Avoid memcpy. Some old compilers fail to inline it */
-			tz->tz_minuteswest = vvd->tz_minuteswest;
-			tz->tz_dsttime = vvd->tz_dsttime;
-		}
-		return 0;
-	}
-	return vdso_fallback_gettimeofday(tv, tz);
-}
diff --git a/arch/sparc/vdso/vdso.lds.S b/arch/sparc/vdso/vdso.lds.S
index 629ab6900df7..f3caa29a331c 100644
--- a/arch/sparc/vdso/vdso.lds.S
+++ b/arch/sparc/vdso/vdso.lds.S
@@ -18,10 +18,8 @@ VERSION {
 	global:
 		clock_gettime;
 		__vdso_clock_gettime;
-		__vdso_clock_gettime_stick;
 		gettimeofday;
 		__vdso_gettimeofday;
-		__vdso_gettimeofday_stick;
 	local: *;
 	};
 }
diff --git a/arch/sparc/vdso/vdso32/vdso32.lds.S b/arch/sparc/vdso/vdso32/vdso32.lds.S
index 218930fdff03..cc6cac2429b3 100644
--- a/arch/sparc/vdso/vdso32/vdso32.lds.S
+++ b/arch/sparc/vdso/vdso32/vdso32.lds.S
@@ -17,10 +17,9 @@ VERSION {
 	global:
 		clock_gettime;
 		__vdso_clock_gettime;
-		__vdso_clock_gettime_stick;
+		__vdso_clock_gettime64;
 		gettimeofday;
 		__vdso_gettimeofday;
-		__vdso_gettimeofday_stick;
 	local: *;
 	};
 }
diff --git a/arch/sparc/vdso/vma.c b/arch/sparc/vdso/vma.c
index bab7a59575e8..4d88828fc45b 100644
--- a/arch/sparc/vdso/vma.c
+++ b/arch/sparc/vdso/vma.c
@@ -19,15 +19,10 @@
 #include <asm/cacheflush.h>
 #include <asm/spitfire.h>
 #include <asm/vdso.h>
-#include <asm/vvar.h>
 #include <asm/page.h>
 
 unsigned int __read_mostly vdso_enabled = 1;
 
-static struct vm_special_mapping vvar_mapping = {
-	.name = "[vvar]"
-};
-
 #ifdef	CONFIG_SPARC64
 static struct vm_special_mapping vdso_mapping64 = {
 	.name = "[vdso]"
@@ -40,207 +35,8 @@ static struct vm_special_mapping vdso_mapping32 = {
 };
 #endif
 
-struct vvar_data *vvar_data;
-
-struct vdso_elfinfo32 {
-	Elf32_Ehdr	*hdr;
-	Elf32_Sym	*dynsym;
-	unsigned long	dynsymsize;
-	const char	*dynstr;
-	unsigned long	text;
-};
-
-struct vdso_elfinfo64 {
-	Elf64_Ehdr	*hdr;
-	Elf64_Sym	*dynsym;
-	unsigned long	dynsymsize;
-	const char	*dynstr;
-	unsigned long	text;
-};
-
-struct vdso_elfinfo {
-	union {
-		struct vdso_elfinfo32 elf32;
-		struct vdso_elfinfo64 elf64;
-	} u;
-};
-
-static void *one_section64(struct vdso_elfinfo64 *e, const char *name,
-			   unsigned long *size)
-{
-	const char *snames;
-	Elf64_Shdr *shdrs;
-	unsigned int i;
-
-	shdrs = (void *)e->hdr + e->hdr->e_shoff;
-	snames = (void *)e->hdr + shdrs[e->hdr->e_shstrndx].sh_offset;
-	for (i = 1; i < e->hdr->e_shnum; i++) {
-		if (!strcmp(snames+shdrs[i].sh_name, name)) {
-			if (size)
-				*size = shdrs[i].sh_size;
-			return (void *)e->hdr + shdrs[i].sh_offset;
-		}
-	}
-	return NULL;
-}
-
-static int find_sections64(const struct vdso_image *image, struct vdso_elfinfo *_e)
-{
-	struct vdso_elfinfo64 *e = &_e->u.elf64;
-
-	e->hdr = image->data;
-	e->dynsym = one_section64(e, ".dynsym", &e->dynsymsize);
-	e->dynstr = one_section64(e, ".dynstr", NULL);
-
-	if (!e->dynsym || !e->dynstr) {
-		pr_err("VDSO64: Missing symbol sections.\n");
-		return -ENODEV;
-	}
-	return 0;
-}
-
-static Elf64_Sym *find_sym64(const struct vdso_elfinfo64 *e, const char *name)
-{
-	unsigned int i;
-
-	for (i = 0; i < (e->dynsymsize / sizeof(Elf64_Sym)); i++) {
-		Elf64_Sym *s = &e->dynsym[i];
-		if (s->st_name == 0)
-			continue;
-		if (!strcmp(e->dynstr + s->st_name, name))
-			return s;
-	}
-	return NULL;
-}
-
-static int patchsym64(struct vdso_elfinfo *_e, const char *orig,
-		      const char *new)
-{
-	struct vdso_elfinfo64 *e = &_e->u.elf64;
-	Elf64_Sym *osym = find_sym64(e, orig);
-	Elf64_Sym *nsym = find_sym64(e, new);
-
-	if (!nsym || !osym) {
-		pr_err("VDSO64: Missing symbols.\n");
-		return -ENODEV;
-	}
-	osym->st_value = nsym->st_value;
-	osym->st_size = nsym->st_size;
-	osym->st_info = nsym->st_info;
-	osym->st_other = nsym->st_other;
-	osym->st_shndx = nsym->st_shndx;
-
-	return 0;
-}
-
-static void *one_section32(struct vdso_elfinfo32 *e, const char *name,
-			   unsigned long *size)
-{
-	const char *snames;
-	Elf32_Shdr *shdrs;
-	unsigned int i;
-
-	shdrs = (void *)e->hdr + e->hdr->e_shoff;
-	snames = (void *)e->hdr + shdrs[e->hdr->e_shstrndx].sh_offset;
-	for (i = 1; i < e->hdr->e_shnum; i++) {
-		if (!strcmp(snames+shdrs[i].sh_name, name)) {
-			if (size)
-				*size = shdrs[i].sh_size;
-			return (void *)e->hdr + shdrs[i].sh_offset;
-		}
-	}
-	return NULL;
-}
-
-static int find_sections32(const struct vdso_image *image, struct vdso_elfinfo *_e)
-{
-	struct vdso_elfinfo32 *e = &_e->u.elf32;
-
-	e->hdr = image->data;
-	e->dynsym = one_section32(e, ".dynsym", &e->dynsymsize);
-	e->dynstr = one_section32(e, ".dynstr", NULL);
-
-	if (!e->dynsym || !e->dynstr) {
-		pr_err("VDSO32: Missing symbol sections.\n");
-		return -ENODEV;
-	}
-	return 0;
-}
-
-static Elf32_Sym *find_sym32(const struct vdso_elfinfo32 *e, const char *name)
-{
-	unsigned int i;
-
-	for (i = 0; i < (e->dynsymsize / sizeof(Elf32_Sym)); i++) {
-		Elf32_Sym *s = &e->dynsym[i];
-		if (s->st_name == 0)
-			continue;
-		if (!strcmp(e->dynstr + s->st_name, name))
-			return s;
-	}
-	return NULL;
-}
-
-static int patchsym32(struct vdso_elfinfo *_e, const char *orig,
-		      const char *new)
-{
-	struct vdso_elfinfo32 *e = &_e->u.elf32;
-	Elf32_Sym *osym = find_sym32(e, orig);
-	Elf32_Sym *nsym = find_sym32(e, new);
-
-	if (!nsym || !osym) {
-		pr_err("VDSO32: Missing symbols.\n");
-		return -ENODEV;
-	}
-	osym->st_value = nsym->st_value;
-	osym->st_size = nsym->st_size;
-	osym->st_info = nsym->st_info;
-	osym->st_other = nsym->st_other;
-	osym->st_shndx = nsym->st_shndx;
-
-	return 0;
-}
-
-static int find_sections(const struct vdso_image *image, struct vdso_elfinfo *e,
-			 bool elf64)
-{
-	if (elf64)
-		return find_sections64(image, e);
-	else
-		return find_sections32(image, e);
-}
-
-static int patch_one_symbol(struct vdso_elfinfo *e, const char *orig,
-			    const char *new_target, bool elf64)
-{
-	if (elf64)
-		return patchsym64(e, orig, new_target);
-	else
-		return patchsym32(e, orig, new_target);
-}
-
-static int stick_patch(const struct vdso_image *image, struct vdso_elfinfo *e, bool elf64)
-{
-	int err;
-
-	err = find_sections(image, e, elf64);
-	if (err)
-		return err;
-
-	err = patch_one_symbol(e,
-			       "__vdso_gettimeofday",
-			       "__vdso_gettimeofday_stick", elf64);
-	if (err)
-		return err;
-
-	return patch_one_symbol(e,
-				"__vdso_clock_gettime",
-				"__vdso_clock_gettime_stick", elf64);
-	return 0;
-}
-
 /*
- * Allocate pages for the vdso and vvar, and copy in the vdso text from the
+ * Allocate pages for the vdso, and copy in the vdso text from the
  * kernel image.
  */
 static int __init init_vdso_image(const struct vdso_image *image,
@@ -248,16 +44,8 @@ static int __init init_vdso_image(const struct vdso_image *image,
 				  bool elf64)
 {
 	int cnpages = (image->size) / PAGE_SIZE;
-	struct page *dp, **dpp = NULL;
 	struct page *cp, **cpp = NULL;
-	struct vdso_elfinfo ei;
-	int i, dnpages = 0;
-
-	if (tlb_type != spitfire) {
-		int err = stick_patch(image, &ei, elf64);
-		if (err)
-			return err;
-	}
+	int i;
 
 	/*
 	 * First, the vdso text.  This is initialied data, an integral number of
@@ -280,31 +68,6 @@ static int __init init_vdso_image(const struct vdso_image *image,
 		copy_page(page_address(cp), image->data + i * PAGE_SIZE);
 	}
 
-	/*
-	 * Now the vvar page.  This is uninitialized data.
-	 */
-
-	if (vvar_data == NULL) {
-		dnpages = (sizeof(struct vvar_data) / PAGE_SIZE) + 1;
-		if (WARN_ON(dnpages != 1))
-			goto oom;
-		dpp = kcalloc(dnpages, sizeof(struct page *), GFP_KERNEL);
-		vvar_mapping.pages = dpp;
-
-		if (!dpp)
-			goto oom;
-
-		dp = alloc_page(GFP_KERNEL);
-		if (!dp)
-			goto oom;
-
-		dpp[0] = dp;
-		vvar_data = page_address(dp);
-		memset(vvar_data, 0, PAGE_SIZE);
-
-		vvar_data->seq = 0;
-	}
-
 	return 0;
  oom:
 	if (cpp != NULL) {
@@ -316,15 +79,6 @@ static int __init init_vdso_image(const struct vdso_image *image,
 		vdso_mapping->pages = NULL;
 	}
 
-	if (dpp != NULL) {
-		for (i = 0; i < dnpages; i++) {
-			if (dpp[i] != NULL)
-				__free_page(dpp[i]);
-		}
-		kfree(dpp);
-		vvar_mapping.pages = NULL;
-	}
-
 	pr_warn("Cannot allocate vdso\n");
 	vdso_enabled = 0;
 	return -ENOMEM;
@@ -403,21 +157,8 @@ static int map_vdso(const struct vdso_image *image,
 				       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
 				       vdso_mapping);
 
-	if (IS_ERR(vma)) {
-		ret = PTR_ERR(vma);
-		goto up_fail;
-	}
-
-	vma = _install_special_mapping(mm,
-				       addr,
-				       -image->sym_vvar_start,
-				       VM_READ|VM_MAYREAD,
-				       &vvar_mapping);
-
-	if (IS_ERR(vma)) {
+	if (IS_ERR(vma))
 		ret = PTR_ERR(vma);
-		do_munmap(mm, text_start, image->size, NULL);
-	}
 
 up_fail:
 	if (ret)
-- 
2.39.5

[PATCH 2/2] clocksource: remove ARCH_CLOCKSOURCE_DATA

[Arnd Bergmann]

From: Arnd Bergmann <arnd@arndb.de>

Without the sparc64 vdso, there are no remaining users
of ARCH_CLOCKSOURCE_DATA, and it can just be removed.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 arch/sparc/Kconfig                   |  1 -
 arch/sparc/include/asm/clocksource.h | 17 -----------------
 arch/sparc/kernel/time_64.c          |  3 ---
 include/linux/clocksource.h          |  6 +-----
 kernel/time/Kconfig                  |  4 ----
 5 files changed, 1 insertion(+), 30 deletions(-)
 delete mode 100644 arch/sparc/include/asm/clocksource.h

diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
index 776ce79ef188..b126a421db9c 100644
--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -101,7 +101,6 @@ config SPARC64
 	select HAVE_REGS_AND_STACK_ACCESS_API
 	select ARCH_USE_QUEUED_RWLOCKS
 	select ARCH_USE_QUEUED_SPINLOCKS
-	select ARCH_CLOCKSOURCE_DATA
 	select ARCH_HAS_PTE_SPECIAL
 	select PCI_DOMAINS if PCI
 	select ARCH_HAS_GIGANTIC_PAGE
diff --git a/arch/sparc/include/asm/clocksource.h b/arch/sparc/include/asm/clocksource.h
deleted file mode 100644
index d63ef224befe..000000000000
--- a/arch/sparc/include/asm/clocksource.h
+++ /dev/null
@@ -1,17 +0,0 @@
-/*
- * Copyright (c) 2017 Oracle and/or its affiliates. All rights reserved.
- */
-
-#ifndef _ASM_SPARC_CLOCKSOURCE_H
-#define _ASM_SPARC_CLOCKSOURCE_H
-
-/* VDSO clocksources */
-#define VCLOCK_NONE   0  /* Nothing userspace can do. */
-#define VCLOCK_TICK   1  /* Use %tick.  */
-#define VCLOCK_STICK  2  /* Use %stick. */
-
-struct arch_clocksource_data {
-	int vclock_mode;
-};
-
-#endif /* _ASM_SPARC_CLOCKSOURCE_H */
diff --git a/arch/sparc/kernel/time_64.c b/arch/sparc/kernel/time_64.c
index 422ec5d03160..547c6f8bef36 100644
--- a/arch/sparc/kernel/time_64.c
+++ b/arch/sparc/kernel/time_64.c
@@ -838,14 +838,11 @@ void __init time_init_early(void)
 	if (tlb_type == spitfire) {
 		if (is_hummingbird()) {
 			init_tick_ops(&hbtick_operations);
-			clocksource_tick.archdata.vclock_mode = VCLOCK_NONE;
 		} else {
 			init_tick_ops(&tick_operations);
-			clocksource_tick.archdata.vclock_mode = VCLOCK_TICK;
 		}
 	} else {
 		init_tick_ops(&stick_operations);
-		clocksource_tick.archdata.vclock_mode = VCLOCK_STICK;
 	}
 }
 
diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index 65b7c41471c3..12d853b18832 100644
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -25,8 +25,7 @@ struct clocksource_base;
 struct clocksource;
 struct module;
 
-#if defined(CONFIG_ARCH_CLOCKSOURCE_DATA) || \
-    defined(CONFIG_GENERIC_GETTIMEOFDAY)
+#if defined(CONFIG_GENERIC_GETTIMEOFDAY)
 #include <asm/clocksource.h>
 #endif
 
@@ -106,9 +105,6 @@ struct clocksource {
 	u64			max_idle_ns;
 	u32			maxadj;
 	u32			uncertainty_margin;
-#ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
-	struct arch_clocksource_data archdata;
-#endif
 	u64			max_cycles;
 	u64			max_raw_delta;
 	const char		*name;
diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
index b0b97a60aaa6..d7e67d397c86 100644
--- a/kernel/time/Kconfig
+++ b/kernel/time/Kconfig
@@ -9,10 +9,6 @@
 config CLOCKSOURCE_WATCHDOG
 	bool
 
-# Architecture has extra clocksource data
-config ARCH_CLOCKSOURCE_DATA
-	bool
-
 # Architecture has extra clocksource init called from registration
 config ARCH_CLOCKSOURCE_INIT
 	bool
-- 
2.39.5

Re: [PATCH 1/2] vdso: sparc: stub out custom vdso implementation

[John Paul Adrian Glaubitz]

Hello Arnd,

On Mon, 2025-07-07 at 16:46 +0200, Arnd Bergmann wrote:
> Rip out the whole thing and replace it with a minimal stub as we do
> on parisc and uml. This introduces a small performance regression when
> using a libc that is aware of the vdso (glibc-2.29 or higher).

Can this performance hit quantified in any way?

And is there previous serious where this change was made for other archs?

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer
`. `'   Physicist
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913

Re: [PATCH 1/2] vdso: sparc: stub out custom vdso implementation

[Arnd Bergmann]

On Mon, Jul 7, 2025, at 17:22, John Paul Adrian Glaubitz wrote:
> Hello Arnd,
>
> On Mon, 2025-07-07 at 16:46 +0200, Arnd Bergmann wrote:
>> Rip out the whole thing and replace it with a minimal stub as we do
>> on parisc and uml. This introduces a small performance regression when
>> using a libc that is aware of the vdso (glibc-2.29 or higher).
>
> Can this performance hit quantified in any way?

It's trivial to test calling glibc clock_gettime() in a loop
on a specific piece of hardware, the difference should largely
depend on how long the timer hardware access takes compared
to the syscall overhead.

On machines that have neither TICK nor STICK clocksource, the
simpler version should even be minimally faster, on those that
have one of the two, there is an added cost for entering the
syscall on every clock_gettime() as we do on architectures without
vdso.

> And is there previous serious where this change was made for other archs?

See 
https://lore.kernel.org/lkml/2078551b-c0b0-4201-b8d7-1faafa3647e6@app.fastmail.com/#t
for the thread that led to this one.

There is also commit 5f55e098b8d0 ("parisc: Add 64-bit gettimeofday()
and clock_gettime() vDSO functions") that adds similar stubs on
parisc.

      Arnd

Re: [PATCH 1/2] vdso: sparc: stub out custom vdso implementation

[John Paul Adrian Glaubitz]

Hi,

On Mon, 2025-07-07 at 17:45 +0200, Arnd Bergmann wrote:
> On Mon, Jul 7, 2025, at 17:22, John Paul Adrian Glaubitz wrote:
> > Hello Arnd,
> > 
> > On Mon, 2025-07-07 at 16:46 +0200, Arnd Bergmann wrote:
> > > Rip out the whole thing and replace it with a minimal stub as we do
> > > on parisc and uml. This introduces a small performance regression when
> > > using a libc that is aware of the vdso (glibc-2.29 or higher).
> > 
> > Can this performance hit quantified in any way?
> 
> It's trivial to test calling glibc clock_gettime() in a loop
> on a specific piece of hardware, the difference should largely
> depend on how long the timer hardware access takes compared
> to the syscall overhead.
> 
> On machines that have neither TICK nor STICK clocksource, the
> simpler version should even be minimally faster, on those that
> have one of the two, there is an added cost for entering the
> syscall on every clock_gettime() as we do on architectures without
> vdso.

OK, thanks. Since Andreas has access to a SPARC T4 as of recently, he should
be able to test this. Please allow some time for him to review and test the
changes, so we can be sure this doesn't cause any serious regressions.

> > And is there previous serious where this change was made for other archs?
> 
> See 
> https://lore.kernel.org/lkml/2078551b-c0b0-4201-b8d7-1faafa3647e6@app.fastmail.com/#t
> for the thread that led to this one.
> 
> There is also commit 5f55e098b8d0 ("parisc: Add 64-bit gettimeofday()
> and clock_gettime() vDSO functions") that adds similar stubs on
> parisc.

OK, thanks for the pointer.

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer
`. `'   Physicist
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913

Re: [PATCH 2/2] clocksource: remove ARCH_CLOCKSOURCE_DATA

[John Stultz]

On Mon, Jul 7, 2025 at 7:48 AM Arnd Bergmann <arnd@kernel.org> wrote:
> From: Arnd Bergmann <arnd@arndb.de>
>
> Without the sparc64 vdso, there are no remaining users
> of ARCH_CLOCKSOURCE_DATA, and it can just be removed.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>  arch/sparc/Kconfig                   |  1 -
>  arch/sparc/include/asm/clocksource.h | 17 -----------------
>  arch/sparc/kernel/time_64.c          |  3 ---
>  include/linux/clocksource.h          |  6 +-----
>  kernel/time/Kconfig                  |  4 ----
>  5 files changed, 1 insertion(+), 30 deletions(-)
>  delete mode 100644 arch/sparc/include/asm/clocksource.h

Acked-by: John Stultz <jstultz@google.com>

Re: [PATCH 1/2] vdso: sparc: stub out custom vdso implementation

[Thomas Weißschuh]

On Mon, Jul 07, 2025 at 04:46:37PM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> 
> sparc64 is the only remaining architecture that has its own implementation
> of the vdso clock_gettime/gettimeofday helpers in place of the generic
> code. This causes a number of issues:
> 
>  - Changes to the vdso interfaces require adding sparc64 specific hacks
>    even when nothing else needs them
> 
>  - The prototypes in <vdso/gettime.h> don't match the function implementation,
>    and not including that header to avoid the build error from that causes
>    another warning:
> 
>   arch/sparc/vdso/vclock_gettime.c:274:1: error: no previous prototype for '__vdso_clock_gettime' [-Werror=missing-prototypes]
>     274 | __vdso_clock_gettime(clockid_t clock, struct __kernel_old_timespec *ts)
>         | ^~~~~~~~~~~~~~~~~~~~
> 
>  - Nobody has ever implemented the clock_gettime64() vdso that is required for
>    32-bit compat tasks
> 
>  - The warning about the missing executable-stack flag was missed:
> 
>   sparc-linux-ld: warning: arch/sparc/vdso/vdso-note.o: missing .note.GNU-stack section implies executable stack
>   sparc-linux-ld: NOTE: This behaviour is deprecated and will be removed in a future version of the linker

IMO this should be in its own patch.

> Most of the removed code only exists on sparc in order to dynamically
> patch the vdso based on the presence of the tick vs vtick based
> clocksource.
> 
> Rip out the whole thing and replace it with a minimal stub as we do
> on parisc and uml. This introduces a small performance regression when
> using a libc that is aware of the vdso (glibc-2.29 or higher).
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Thanks, this makes things easier.

Reviewed-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Tested-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>

But why do we even need the stubs? Removing the time functions from the
vDSO completely should also work, no?
For parisc there was no reasoning why stubs were used. On uml the stubs are
necessary to prevent the libc from calling into the host vsyscall [0], but
that looks irrelevant for SPARC.

[0] f1c2bb8b9964 ("um: implement a x86_64 vDSO")

Re: [PATCH 1/2] vdso: sparc: stub out custom vdso implementation

[Arnd Bergmann]

On Tue, Jul 8, 2025, at 07:39, Thomas Weißschuh wrote:
> On Mon, Jul 07, 2025 at 04:46:37PM +0200, Arnd Bergmann wrote:
>> 
>>   sparc-linux-ld: warning: arch/sparc/vdso/vdso-note.o: missing .note.GNU-stack section implies executable stack
>>   sparc-linux-ld: NOTE: This behaviour is deprecated and will be removed in a future version of the linker
>
> IMO this should be in its own patch.

Fair enough, I considered splitting up my patch further already but
tried to keep it simple. This one does make sense to split out though.

>> Most of the removed code only exists on sparc in order to dynamically
>> patch the vdso based on the presence of the tick vs vtick based
>> clocksource.
>> 
>> Rip out the whole thing and replace it with a minimal stub as we do
>> on parisc and uml. This introduces a small performance regression when
>> using a libc that is aware of the vdso (glibc-2.29 or higher).
>> 
>> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>
> Thanks, this makes things easier.
>
> Reviewed-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
> Tested-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
>
> But why do we even need the stubs? Removing the time functions from the
> vDSO completely should also work, no?
> For parisc there was no reasoning why stubs were used. On uml the stubs are
> necessary to prevent the libc from calling into the host vsyscall [0], but
> that looks irrelevant for SPARC.
>
> [0] f1c2bb8b9964 ("um: implement a x86_64 vDSO")

I was wondering about this myself, I thought this might have been
for runtime environments that just assume the vDSO is there, possibly
some non-C libraries, or future glibc versions that may error
out when the vdso is absent instead of falling back to the syscall.

The 5f55e098b8d0 ("parisc: Add 64-bit gettimeofday() and
clock_gettime() vDSO functions") commit and the corresponding
glibc patch one don't have any explanation unfortunately, but
maybe Helge can explain why this is needed.

The arch/x86/um/vdso/um_vdso.c version for 32-bit seems to still
be missing the clock_gettime64() entry, any idea what the
resulting behavior is for time64 userspace?

      Arnd

Re: [PATCH 1/2] vdso: sparc: stub out custom vdso implementation

[Thomas Weißschuh]

On Tue, Jul 08, 2025 at 08:40:27AM +0200, Arnd Bergmann wrote:
> On Tue, Jul 8, 2025, at 07:39, Thomas Weißschuh wrote:

(...)

> > But why do we even need the stubs? Removing the time functions from the
> > vDSO completely should also work, no?
> > For parisc there was no reasoning why stubs were used. On uml the stubs are
> > necessary to prevent the libc from calling into the host vsyscall [0], but
> > that looks irrelevant for SPARC.
> >
> > [0] f1c2bb8b9964 ("um: implement a x86_64 vDSO")
> 
> I was wondering about this myself, I thought this might have been
> for runtime environments that just assume the vDSO is there, possibly
> some non-C libraries, or future glibc versions that may error
> out when the vdso is absent instead of falling back to the syscall.

libc erroring out if the vdso is missing sounds unlikely to me.

(...)

> The arch/x86/um/vdso/um_vdso.c version for 32-bit seems to still
> be missing the clock_gettime64() entry, any idea what the
> resulting behavior is for time64 userspace?

The vsyscall page is for 64-bit userspace only, and I think always ways.

In any case, modern distro kernels don't provide the vsyscall page at all or
emulate it through syscall stubs, which are affected by the uml host access issue.
Also glibc dropped vsyscall page support in 2020.


Thomas

Re: [PATCH 1/2] vdso: sparc: stub out custom vdso implementation

[Andreas Larsson]

On 2025-07-07 18:05, John Paul Adrian Glaubitz wrote:
> Hi,
> 
> On Mon, 2025-07-07 at 17:45 +0200, Arnd Bergmann wrote:
>> On Mon, Jul 7, 2025, at 17:22, John Paul Adrian Glaubitz wrote:
>>> Hello Arnd,
>>>
>>> On Mon, 2025-07-07 at 16:46 +0200, Arnd Bergmann wrote:
>>>> Rip out the whole thing and replace it with a minimal stub as we do
>>>> on parisc and uml. This introduces a small performance regression when
>>>> using a libc that is aware of the vdso (glibc-2.29 or higher).
>>>
>>> Can this performance hit quantified in any way?
>>
>> It's trivial to test calling glibc clock_gettime() in a loop
>> on a specific piece of hardware, the difference should largely
>> depend on how long the timer hardware access takes compared
>> to the syscall overhead.
>>
>> On machines that have neither TICK nor STICK clocksource, the
>> simpler version should even be minimally faster, on those that
>> have one of the two, there is an added cost for entering the
>> syscall on every clock_gettime() as we do on architectures without
>> vdso.
> 
> OK, thanks. Since Andreas has access to a SPARC T4 as of recently, he should
> be able to test this. Please allow some time for him to review and test the
> changes, so we can be sure this doesn't cause any serious regressions.

I tested this patch (running Linux in an LDOM under Solaris) and
measuring the cost of clock_gettime(), running millions of calls. The
calls takes around 13-15 times as long (from around 82-94 nanoseconds
per call to around 1220 nanoseconds per call) with this patch compared
to without, so not an insignificant performance regression in this
environment.

Cheers,
Andreas

Re: [PATCH 1/2] vdso: sparc: stub out custom vdso implementation

[Arnd Bergmann]

On Thu, Jul 10, 2025, at 18:22, Andreas Larsson wrote:
> On 2025-07-07 18:05, John Paul Adrian Glaubitz wrote:
>> On Mon, 2025-07-07 at 17:45 +0200, Arnd Bergmann wrote:
>>> On Mon, Jul 7, 2025, at 17:22, John Paul Adrian Glaubitz wrote:
>>>>
>>>> On Mon, 2025-07-07 at 16:46 +0200, Arnd Bergmann wrote:
>>>>> Rip out the whole thing and replace it with a minimal stub as we do
>>>>> on parisc and uml. This introduces a small performance regression when
>>>>> using a libc that is aware of the vdso (glibc-2.29 or higher).
>>>>
>>>> Can this performance hit quantified in any way?
>>>
>>> It's trivial to test calling glibc clock_gettime() in a loop
>>> on a specific piece of hardware, the difference should largely
>>> depend on how long the timer hardware access takes compared
>>> to the syscall overhead.
>>>
>>> On machines that have neither TICK nor STICK clocksource, the
>>> simpler version should even be minimally faster, on those that
>>> have one of the two, there is an added cost for entering the
>>> syscall on every clock_gettime() as we do on architectures without
>>> vdso.
>> 
>> OK, thanks. Since Andreas has access to a SPARC T4 as of recently, he should
>> be able to test this. Please allow some time for him to review and test the
>> changes, so we can be sure this doesn't cause any serious regressions.
>
> I tested this patch (running Linux in an LDOM under Solaris) and
> measuring the cost of clock_gettime(), running millions of calls. The
> calls takes around 13-15 times as long (from around 82-94 nanoseconds
> per call to around 1220 nanoseconds per call) with this patch compared
> to without, so not an insignificant performance regression in this
> environment.

Ok, thanks a lot for testing! I guess the good news is that I didn't
break functionality here.

Obviously 15x slowdown sounds like a lot, but what I don't know is
whether 1.2µs is actually too slow. Is this CLOCK_REALTIME or some
other clock? I would expect to see a larger difference for the
COARSE version since that saves the hardware access as well.

From what I remember, the original driver for having a VDSO
clock_gettime/gettimeofday was Java applications that call it
too often. Do you know of anyone using Java on performance-critical
sparc64 servers any more, or any other type of workload that
depends on these functions being small?

It is probably not all that hard to convert the VDSO to use the
generic implementation if you remove the runtime patching between
TICK and STICK mode. From the code and the documentation, it
seems that any JPS1 compatible CPU (or newer) uses STICK,
this would be UltraSPARC III (Cheetah), SPARC64 V (Zeus)
and all UltraSPARC T. If you want to give it a try to do the
conversion to the generic VDSO, I could respin my patch to only
remove the older TICK version and the runtime patching but leave
the STICK one. I don't think it's worth my time trying to convert
STICK myself since I have no way of testing it.

Another option would be to start by adding a VDSO for LEON
CPUs using the ASR22:23 upcounter register. This should be
fairly easy to do if you copy the CSR_TIME code from riscv
and replace their __arch_get_hw_counter(), and this is probably more
relevant than the sparc64 version. Once that works, you
can extend it to use STICK on JPS1.

     Arnd

Re: [PATCH 1/2] vdso: sparc: stub out custom vdso implementation

[John Paul Adrian Glaubitz]

Hello Arnd,

On Fri, 2025-07-11 at 12:31 +0200, Arnd Bergmann wrote:
> It is probably not all that hard to convert the VDSO to use the
> generic implementation if you remove the runtime patching between
> TICK and STICK mode. From the code and the documentation, it
> seems that any JPS1 compatible CPU (or newer) uses STICK,
> this would be UltraSPARC III (Cheetah), SPARC64 V (Zeus)
> and all UltraSPARC T. If you want to give it a try to do the
> conversion to the generic VDSO, I could respin my patch to only
> remove the older TICK version and the runtime patching but leave
> the STICK one. I don't think it's worth my time trying to convert
> STICK myself since I have no way of testing it.

I could create an account for you on the SPARC T4 that Andreas is
currently using for testing, so you could test these changes on real
hardware (Linux LDOM running on Solaris 11.4).

In about one month, I could also create an account for you on a SPARC T5
which is much faster and where you have more RAM and disk space available
for testing.

Please send me a private email if you're interested.

I can also help with other architectures such as SuperH, MIPS, PowerPC or
Alpha. All on real hardware.

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer
`. `'   Physicist
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913

Re: [PATCH 1/2] vdso: sparc: stub out custom vdso implementation

[Thomas Gleixner]

On Fri, Jul 11 2025 at 12:31, Arnd Bergmann wrote:
> It is probably not all that hard to convert the VDSO to use the
> generic implementation if you remove the runtime patching between
> TICK and STICK mode. From the code and the documentation, it
> seems that any JPS1 compatible CPU (or newer) uses STICK,
> this would be UltraSPARC III (Cheetah), SPARC64 V (Zeus)
> and all UltraSPARC T. If you want to give it a try to do the
> conversion to the generic VDSO, I could respin my patch to only
> remove the older TICK version and the runtime patching but leave
> the STICK one. I don't think it's worth my time trying to convert
> STICK myself since I have no way of testing it.

Getting rid of the run-time patching is really trivial. The clocksource
setup initializes clocksource::archdata::vdso_clockmode already
correctly with VCLOCK_NONE, VCLOCK_TICK and VCLOCK_STICK.

So all you need is:

static inline u64 __arch_get_hw_counter(s32 clock_mode,	const struct vdso_time_data *vd)
{
	if (likely(clock_mode == VDSO_CLOCKMODE_STICK))
		return vread_stick();

        if (clock_mode == VDSO_CLOCKMODE_TICK))
		return vread_tick();

	return U64_MAX;
}

Plus a 32-bit specific version of vdso_shift_ns(), which means just
renaming the 32-bit variant of __shr64() and removing the then pointless
notrace annotation.

This should just work out of the box and the performance regression will
be minimal if even measurable.

Thanks,

        tglx

Re: [PATCH 1/2] vdso: sparc: stub out custom vdso implementation

[Thomas Weißschuh]

On Mon, Jul 07, 2025 at 04:46:37PM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> 
> sparc64 is the only remaining architecture that has its own implementation
> of the vdso clock_gettime/gettimeofday helpers in place of the generic
> code. This causes a number of issues:
> 
>  - Changes to the vdso interfaces require adding sparc64 specific hacks
>    even when nothing else needs them
> 
>  - The prototypes in <vdso/gettime.h> don't match the function implementation,
>    and not including that header to avoid the build error from that causes
>    another warning:
> 
>   arch/sparc/vdso/vclock_gettime.c:274:1: error: no previous prototype for '__vdso_clock_gettime' [-Werror=missing-prototypes]
>     274 | __vdso_clock_gettime(clockid_t clock, struct __kernel_old_timespec *ts)
>         | ^~~~~~~~~~~~~~~~~~~~
> 
>  - Nobody has ever implemented the clock_gettime64() vdso that is required for
>    32-bit compat tasks
> 
>  - The warning about the missing executable-stack flag was missed:
> 
>   sparc-linux-ld: warning: arch/sparc/vdso/vdso-note.o: missing .note.GNU-stack section implies executable stack
>   sparc-linux-ld: NOTE: This behaviour is deprecated and will be removed in a future version of the linker
> 
> Most of the removed code only exists on sparc in order to dynamically
> patch the vdso based on the presence of the tick vs vtick based
> clocksource.
> 
> Rip out the whole thing and replace it with a minimal stub as we do
> on parisc and uml. This introduces a small performance regression when
> using a libc that is aware of the vdso (glibc-2.29 or higher).
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

FYI I have a series prepared that will move SPARC to the generic vDSO and also
addresses the problems listed above and mentioned by tglx.

I'll send it after the merge window.

(...)


Thomas

Re: [PATCH 1/2] vdso: sparc: stub out custom vdso implementation

[John Paul Adrian Glaubitz]

Hi Thomas,

On Wed, 2025-07-23 at 12:57 +0200, Thomas Weißschuh wrote:
> On Mon, Jul 07, 2025 at 04:46:37PM +0200, Arnd Bergmann wrote:
> > From: Arnd Bergmann <arnd@arndb.de>
> > 
> > sparc64 is the only remaining architecture that has its own implementation
> > of the vdso clock_gettime/gettimeofday helpers in place of the generic
> > code. This causes a number of issues:
> > 
> >  - Changes to the vdso interfaces require adding sparc64 specific hacks
> >    even when nothing else needs them
> > 
> >  - The prototypes in <vdso/gettime.h> don't match the function implementation,
> >    and not including that header to avoid the build error from that causes
> >    another warning:
> > 
> >   arch/sparc/vdso/vclock_gettime.c:274:1: error: no previous prototype for '__vdso_clock_gettime' [-Werror=missing-prototypes]
> >     274 | __vdso_clock_gettime(clockid_t clock, struct __kernel_old_timespec *ts)
> >         | ^~~~~~~~~~~~~~~~~~~~
> > 
> >  - Nobody has ever implemented the clock_gettime64() vdso that is required for
> >    32-bit compat tasks
> > 
> >  - The warning about the missing executable-stack flag was missed:
> > 
> >   sparc-linux-ld: warning: arch/sparc/vdso/vdso-note.o: missing .note.GNU-stack section implies executable stack
> >   sparc-linux-ld: NOTE: This behaviour is deprecated and will be removed in a future version of the linker
> > 
> > Most of the removed code only exists on sparc in order to dynamically
> > patch the vdso based on the presence of the tick vs vtick based
> > clocksource.
> > 
> > Rip out the whole thing and replace it with a minimal stub as we do
> > on parisc and uml. This introduces a small performance regression when
> > using a libc that is aware of the vdso (glibc-2.29 or higher).
> > 
> > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> 
> FYI I have a series prepared that will move SPARC to the generic vDSO and also
> addresses the problems listed above and mentioned by tglx.
> 
> I'll send it after the merge window.

Great, thanks a lot! Andreas can then retest the patch and see if the performance
hit is measurable or acceptable at all.

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer
`. `'   Physicist
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913

Re: [PATCH 1/2] vdso: sparc: stub out custom vdso implementation

[Thomas Gleixner]

On Wed, Jul 23 2025 at 12:57, Thomas Weißschuh wrote:
> FYI I have a series prepared that will move SPARC to the generic vDSO and also
> addresses the problems listed above and mentioned by tglx.
>
> I'll send it after the merge window.

Just post it as an RFC, so people can test it.