mips: Add support for generic vDSO

The mips vDSO library requires some adaptations to use to take advantage
of the newly introduced generic vDSO library.

This patch introduces the following changes:
 - Modification of vdso.c to be compliant with the common vdso datapage
 - Use of lib/vdso for gettimeofday
 - Implementation of __vdso_time
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>

arch/mips/Kconfig

@@ -32,6 +32,7 @@ config MIPS
 	select GENERIC_SCHED_CLOCK if !CAVIUM_OCTEON_SOC
 	select GENERIC_SMP_IDLE_THREAD
 	select GENERIC_TIME_VSYSCALL
+	select GENERIC_GETTIMEOFDAY
 	select HANDLE_DOMAIN_IRQ
 	select HAVE_ARCH_COMPILER_H
 	select HAVE_ARCH_JUMP_LABEL
@@ -70,6 +71,8 @@ config MIPS
 	select HAVE_STACKPROTECTOR
 	select HAVE_SYSCALL_TRACEPOINTS
 	select HAVE_VIRT_CPU_ACCOUNTING_GEN if 64BIT || !SMP
+	select HAVE_GENERIC_VDSO
+	select HAVE_ARCH_TIMER
 	select IRQ_FORCED_THREADING
 	select MODULES_USE_ELF_RELA if MODULES && 64BIT
 	select MODULES_USE_ELF_REL if MODULES

arch/mips/include/asm/vdso.h

@@ -12,6 +12,7 @@
 #define __ASM_VDSO_H
 
 #include <linux/mm_types.h>
+#include <vdso/datapage.h>
 
 #include <asm/barrier.h>
 
@@ -54,12 +55,12 @@ extern struct mips_vdso_image vdso_image_n32;
 #endif
 
 /**
- * union mips_vdso_data - Data provided by the kernel for the VDSO.
+ * struct vdso_data - Data provided by the kernel for the VDSO.
  * @xtime_sec:		Current real time (seconds part).
  * @xtime_nsec:		Current real time (nanoseconds part, shifted).
  * @wall_to_mono_sec:	Wall-to-monotonic offset (seconds part).
  * @wall_to_mono_nsec:	Wall-to-monotonic offset (nanoseconds part).
- * @seq_count:		Counter to synchronise updates (odd = updating).
+ * @tb_seq_count:		Counter to synchronise updates (odd = updating).
  * @cs_shift:		Clocksource shift value.
  * @clock_mode:		Clocksource to use for time functions.
  * @cs_mult:		Clocksource multiplier value.
@@ -76,61 +77,23 @@ extern struct mips_vdso_image vdso_image_n32;
  * for both 64- and 32-bit (for 32-bit userland on 64-bit kernel).
  */
 union mips_vdso_data {
-	struct {
-		u64 xtime_sec;
-		u64 xtime_nsec;
-		u64 wall_to_mono_sec;
-		u64 wall_to_mono_nsec;
-		u32 seq_count;
-		u32 cs_shift;
-		u8 clock_mode;
-		u32 cs_mult;
-		u64 cs_cycle_last;
-		u64 cs_mask;
-		s32 tz_minuteswest;
-		s32 tz_dsttime;
-	};
-
+	struct vdso_data data;
 	u8 page[PAGE_SIZE];
 };
 
-static inline u32 vdso_data_read_begin(const union mips_vdso_data *data)
-{
-	u32 seq;
-
-	while (true) {
-		seq = READ_ONCE(data->seq_count);
-		if (likely(!(seq & 1))) {
-			/* Paired with smp_wmb() in vdso_data_write_*(). */
-			smp_rmb();
-			return seq;
-		}
-
-		cpu_relax();
-	}
-}
-
-static inline bool vdso_data_read_retry(const union mips_vdso_data *data,
-					u32 start_seq)
-{
-	/* Paired with smp_wmb() in vdso_data_write_*(). */
-	smp_rmb();
-	return unlikely(data->seq_count != start_seq);
-}
-
-static inline void vdso_data_write_begin(union mips_vdso_data *data)
+static inline void vdso_data_write_begin(struct vdso_data *data)
 {
-	++data->seq_count;
+	++data->tb_seq_count;
 
 	/* Ensure sequence update is written before other data page values. */
 	smp_wmb();
 }
 
-static inline void vdso_data_write_end(union mips_vdso_data *data)
+static inline void vdso_data_write_end(struct vdso_data *data)
 {
 	/* Ensure data values are written before updating sequence again. */
 	smp_wmb();
-	++data->seq_count;
+	++data->tb_seq_count;
 }
 
 #endif /* __ASM_VDSO_H */

arch/mips/vdso/gettimeofday.c → arch/mips/include/asm/vdso/gettimeofday.h

 /*
+ * Copyright (C) 2018 ARM Limited
  * Copyright (C) 2015 Imagination Technologies
  * Author: Alex Smith <alex.smith@imgtec.com>
  *
@@ -7,12 +8,15 @@
  * Free Software Foundation;  either version 2 of the  License, or (at your
  * option) any later version.
  */
+#ifndef __ASM_VDSO_GETTIMEOFDAY_H
+#define __ASM_VDSO_GETTIMEOFDAY_H
 
-#include "vdso.h"
+#ifndef __ASSEMBLY__
 
 #include <linux/compiler.h>
 #include <linux/time.h>
 
+#include <asm/vdso/vdso.h>
 #include <asm/clocksource.h>
 #include <asm/io.h>
 #include <asm/unistd.h>
@@ -20,8 +24,8 @@
 
 #ifdef CONFIG_MIPS_CLOCK_VSYSCALL
 
-static __always_inline long gettimeofday_fallback(struct timeval *_tv,
-					  struct timezone *_tz)
+static __always_inline notrace long gettimeofday_fallback(struct timeval *_tv,
+							  struct timezone *_tz)
 {
 	register struct timezone *tz asm("a1") = _tz;
 	register struct timeval *tv asm("a0") = _tv;
@@ -39,10 +43,18 @@ static __always_inline long gettimeofday_fallback(struct timeval *_tv,
 	return error ? -ret : ret;
 }
 
+#else
+
+static __always_inline notrace long gettimeofday_fallback(struct timeval *_tv,
+							  struct timezone *_tz)
+{
+	return -1;
+}
+
 #endif
 
-static __always_inline long clock_gettime_fallback(clockid_t _clkid,
-					   struct timespec *_ts)
+static __always_inline notrace long clock_gettime_fallback(clockid_t _clkid,
+							   struct timespec *_ts)
 {
 	register struct timespec *ts asm("a1") = _ts;
 	register clockid_t clkid asm("a0") = _clkid;
@@ -60,42 +72,23 @@ static __always_inline long clock_gettime_fallback(clockid_t _clkid,
 	return error ? -ret : ret;
 }
 
-static __always_inline int do_realtime_coarse(struct timespec *ts,
-					      const union mips_vdso_data *data)
-{
-	u32 start_seq;
-
-	do {
-		start_seq = vdso_data_read_begin(data);
-
-		ts->tv_sec = data->xtime_sec;
-		ts->tv_nsec = data->xtime_nsec >> data->cs_shift;
-	} while (vdso_data_read_retry(data, start_seq));
-
-	return 0;
-}
-
-static __always_inline int do_monotonic_coarse(struct timespec *ts,
-					       const union mips_vdso_data *data)
+static __always_inline notrace int clock_getres_fallback(clockid_t _clkid,
+							 struct timespec *_ts)
 {
-	u32 start_seq;
-	u64 to_mono_sec;
-	u64 to_mono_nsec;
-
-	do {
-		start_seq = vdso_data_read_begin(data);
-
-		ts->tv_sec = data->xtime_sec;
-		ts->tv_nsec = data->xtime_nsec >> data->cs_shift;
-
-		to_mono_sec = data->wall_to_mono_sec;
-		to_mono_nsec = data->wall_to_mono_nsec;
-	} while (vdso_data_read_retry(data, start_seq));
+	register struct timespec *ts asm("a1") = _ts;
+	register clockid_t clkid asm("a0") = _clkid;
+	register long ret asm("v0");
+	register long nr asm("v0") = __NR_clock_getres;
+	register long error asm("a3");
 
-	ts->tv_sec += to_mono_sec;
-	timespec_add_ns(ts, to_mono_nsec);
+	asm volatile(
+	"       syscall\n"
+	: "=r" (ret), "=r" (error)
+	: "r" (clkid), "r" (ts), "r" (nr)
+	: "$1", "$3", "$8", "$9", "$10", "$11", "$12", "$13",
+	  "$14", "$15", "$24", "$25", "hi", "lo", "memory");
 
-	return 0;
+	return error ? -ret : ret;
 }
 
 #ifdef CONFIG_CSRC_R4K
@@ -118,7 +111,7 @@ static __always_inline u64 read_r4k_count(void)
 
 #ifdef CONFIG_CLKSRC_MIPS_GIC
 
-static __always_inline u64 read_gic_count(const union mips_vdso_data *data)
+static __always_inline u64 read_gic_count(const struct vdso_data *data)
 {
 	void __iomem *gic = get_gic(data);
 	u32 hi, hi2, lo;
@@ -134,9 +127,10 @@ static __always_inline u64 read_gic_count(const union mips_vdso_data *data)
 
 #endif
 
-static __always_inline u64 get_ns(const union mips_vdso_data *data)
+static __always_inline notrace u64 clock_get_virtual_counter(void)
 {
-	u64 cycle_now, delta, nsec;
+	const struct vdso_data *data = get_vdso_data();
+	u64 cycle_now;
 
 	switch (data->clock_mode) {
 #ifdef CONFIG_CSRC_R4K
@@ -150,124 +144,18 @@ static __always_inline u64 get_ns(const union mips_vdso_data *data)
 		break;
 #endif
 	default:
-		return 0;
+		cycle_now = 0;
+		break;
 	}
 
-	delta = (cycle_now - data->cs_cycle_last) & data->cs_mask;
-
-	nsec = (delta * data->cs_mult) + data->xtime_nsec;
-	nsec >>= data->cs_shift;
-
-	return nsec;
-}
-
-static __always_inline int do_realtime(struct timespec *ts,
-				       const union mips_vdso_data *data)
-{
-	u32 start_seq;
-	u64 ns;
-
-	do {
-		start_seq = vdso_data_read_begin(data);
-
-		if (data->clock_mode == VDSO_CLOCK_NONE)
-			return -ENOSYS;
-
-		ts->tv_sec = data->xtime_sec;
-		ns = get_ns(data);
-	} while (vdso_data_read_retry(data, start_seq));
-
-	ts->tv_nsec = 0;
-	timespec_add_ns(ts, ns);
-
-	return 0;
+	return cycle_now;
 }
 
-static __always_inline int do_monotonic(struct timespec *ts,
-					const union mips_vdso_data *data)
+static __always_inline notrace const struct vdso_data *__arch_get_vdso_data(void)
 {
-	u32 start_seq;
-	u64 ns;
-	u64 to_mono_sec;
-	u64 to_mono_nsec;
-
-	do {
-		start_seq = vdso_data_read_begin(data);
-
-		if (data->clock_mode == VDSO_CLOCK_NONE)
-			return -ENOSYS;
-
-		ts->tv_sec = data->xtime_sec;
-		ns = get_ns(data);
-
-		to_mono_sec = data->wall_to_mono_sec;
-		to_mono_nsec = data->wall_to_mono_nsec;
-	} while (vdso_data_read_retry(data, start_seq));
-
-	ts->tv_sec += to_mono_sec;
-	ts->tv_nsec = 0;
-	timespec_add_ns(ts, ns + to_mono_nsec);
-
-	return 0;
+	return get_vdso_data();
 }
 
-#ifdef CONFIG_MIPS_CLOCK_VSYSCALL
-
-/*
- * This is behind the ifdef so that we don't provide the symbol when there's no
- * possibility of there being a usable clocksource, because there's nothing we
- * can do without it. When libc fails the symbol lookup it should fall back on
- * the standard syscall path.
- */
-int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
-{
-	const union mips_vdso_data *data = get_vdso_data();
-	struct timespec ts;
-	int ret;
-
-	ret = do_realtime(&ts, data);
-	if (ret)
-		return gettimeofday_fallback(tv, tz);
-
-	if (tv) {
-		tv->tv_sec = ts.tv_sec;
-		tv->tv_usec = ts.tv_nsec / 1000;
-	}
+#endif /* !__ASSEMBLY__ */
 
-	if (tz) {
-		tz->tz_minuteswest = data->tz_minuteswest;
-		tz->tz_dsttime = data->tz_dsttime;
-	}
-
-	return 0;
-}
-
-#endif /* CONFIG_MIPS_CLOCK_VSYSCALL */
-
-int __vdso_clock_gettime(clockid_t clkid, struct timespec *ts)
-{
-	const union mips_vdso_data *data = get_vdso_data();
-	int ret = -1;
-
-	switch (clkid) {
-	case CLOCK_REALTIME_COARSE:
-		ret = do_realtime_coarse(ts, data);
-		break;
-	case CLOCK_MONOTONIC_COARSE:
-		ret = do_monotonic_coarse(ts, data);
-		break;
-	case CLOCK_REALTIME:
-		ret = do_realtime(ts, data);
-		break;
-	case CLOCK_MONOTONIC:
-		ret = do_monotonic(ts, data);
-		break;
-	default:
-		break;
-	}
-
-	if (ret)
-		ret = clock_gettime_fallback(clkid, ts);
-
-	return ret;
-}
+#endif /* __ASM_VDSO_GETTIMEOFDAY_H */

arch/mips/vdso/vdso.h → arch/mips/include/asm/vdso/vdso.h

@@ -72,14 +72,14 @@ static inline unsigned long get_vdso_base(void)
 	return addr;
 }
 
-static inline const union mips_vdso_data *get_vdso_data(void)
+static inline const struct vdso_data *get_vdso_data(void)
 {
-	return (const union mips_vdso_data *)(get_vdso_base() - PAGE_SIZE);
+	return (const struct vdso_data *)(get_vdso_base() - PAGE_SIZE);
 }
 
 #ifdef CONFIG_CLKSRC_MIPS_GIC
 
-static inline void __iomem *get_gic(const union mips_vdso_data *data)
+static inline void __iomem *get_gic(const struct vdso_data *data)
 {
 	return (void __iomem *)data - PAGE_SIZE;
 }

arch/mips/kernel/vdso.c

@@ -26,7 +26,8 @@
 #include <asm/vdso.h>
 
 /* Kernel-provided data used by the VDSO. */
-static union mips_vdso_data vdso_data __page_aligned_data;
+static union mips_vdso_data mips_vdso_data __page_aligned_data;
+static struct vdso_data *vdso_data = &mips_vdso_data.data;
 
 /*
  * Mapping for the VDSO data/GIC pages. The real pages are mapped manually, as
@@ -72,29 +73,44 @@ subsys_initcall(init_vdso);
 
 void update_vsyscall(struct timekeeper *tk)
 {
-	vdso_data_write_begin(&vdso_data);
-
-	vdso_data.xtime_sec = tk->xtime_sec;
-	vdso_data.xtime_nsec = tk->tkr_mono.xtime_nsec;
-	vdso_data.wall_to_mono_sec = tk->wall_to_monotonic.tv_sec;
-	vdso_data.wall_to_mono_nsec = tk->wall_to_monotonic.tv_nsec;
-	vdso_data.cs_shift = tk->tkr_mono.shift;
-
-	vdso_data.clock_mode = tk->tkr_mono.clock->archdata.vdso_clock_mode;
-	if (vdso_data.clock_mode != VDSO_CLOCK_NONE) {
-		vdso_data.cs_mult = tk->tkr_mono.mult;
-		vdso_data.cs_cycle_last = tk->tkr_mono.cycle_last;
-		vdso_data.cs_mask = tk->tkr_mono.mask;
+	vdso_data_write_begin(vdso_data);
+
+	vdso_data->clock_mode = tk->tkr_mono.clock->archdata.vdso_clock_mode;
+#ifdef DISABLE_MIPS_VDSO
+	vdso_data->use_syscall = true;
+#else
+	vdso_data->use_syscall = !tk->tkr_mono.clock->archdata.vdso_direct;
+#endif /* DISABLE_MIPS_VDSO */
+	vdso_data->xtime_coarse_sec = tk->xtime_sec;
+	vdso_data->xtime_coarse_nsec = tk->tkr_mono.xtime_nsec >>
+						tk->tkr_mono.shift;
+	vdso_data->wtm_clock_sec = tk->wall_to_monotonic.tv_sec;
+	vdso_data->wtm_clock_nsec = tk->wall_to_monotonic.tv_nsec;
+
+	if (vdso_data->clock_mode != VDSO_CLOCK_NONE) {
+		vdso_data->cs_cycle_last = tk->tkr_mono.cycle_last;
+		vdso_data->raw_time_sec = tk->raw_sec;
+		vdso_data->raw_time_nsec = tk->tkr_raw.xtime_nsec;
+		vdso_data->xtime_clock_sec = tk->xtime_sec;
+		vdso_data->xtime_clock_nsec = tk->tkr_mono.xtime_nsec;
+		vdso_data->cs_mono_mult = tk->tkr_mono.mult;
+		vdso_data->cs_raw_mult = tk->tkr_raw.mult;
+		vdso_data->cs_shift = tk->tkr_mono.shift;
+		vdso_data->btm_nsec = ktime_to_ns(tk->offs_boot);
+		vdso_data->tai_sec = tk->xtime_sec +
+					tk->tai_offset;
+		vdso_data->cs_mono_mask = tk->tkr_mono.mask;
+		vdso_data->cs_raw_mask = tk->tkr_mono.mask;
 	}
 
-	vdso_data_write_end(&vdso_data);
+	vdso_data_write_end(vdso_data);
 }
 
 void update_vsyscall_tz(void)
 {
-	if (vdso_data.clock_mode != VDSO_CLOCK_NONE) {
-		vdso_data.tz_minuteswest = sys_tz.tz_minuteswest;
-		vdso_data.tz_dsttime = sys_tz.tz_dsttime;
+	if (vdso_data->clock_mode != VDSO_CLOCK_NONE) {
+		vdso_data->tz_minuteswest = sys_tz.tz_minuteswest;
+		vdso_data->tz_dsttime = sys_tz.tz_dsttime;
 	}
 }
 
@@ -167,7 +183,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 	 */
 	if (cpu_has_dc_aliases) {
 		base = __ALIGN_MASK(base, shm_align_mask);
-		base += ((unsigned long)&vdso_data - gic_size) & shm_align_mask;
+		base += ((unsigned long)vdso_data - gic_size) & shm_align_mask;
 	}
 
 	data_addr = base + gic_size;
@@ -193,7 +209,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 
 	/* Map data page. */
 	ret = remap_pfn_range(vma, data_addr,
-			      virt_to_phys(&vdso_data) >> PAGE_SHIFT,
+			      virt_to_phys(vdso_data) >> PAGE_SHIFT,
 			      PAGE_SIZE, PAGE_READONLY);
 	if (ret)
 		goto out;

arch/mips/vdso/Makefile

 # SPDX-License-Identifier: GPL-2.0
 # Objects to go into the VDSO.
-obj-vdso-y := elf.o gettimeofday.o sigreturn.o
+
+# Absolute relocation type $(ARCH_REL_TYPE_ABS) needs to be defined before
+# the inclusion of generic Makefile.
+ARCH_REL_TYPE_ABS := R_MIPS_JUMP_SLOT|R_MIPS_GLOB_DAT
+include $(srctree)/lib/vdso/Makefile
+
+obj-vdso-y := elf.o vgettimeofday.o sigreturn.o
 
 # Common compiler flags between ABIs.
 ccflags-vdso := \
@@ -14,15 +20,23 @@ ifdef CONFIG_CC_IS_CLANG
 ccflags-vdso += $(filter --target=%,$(KBUILD_CFLAGS))
 endif
 
+#
+# The -fno-jump-tables flag only prevents the compiler from generating
+# jump tables but does not prevent the compiler from emitting absolute
+# offsets.
 cflags-vdso := $(ccflags-vdso) \
 	$(filter -W%,$(filter-out -Wa$(comma)%,$(KBUILD_CFLAGS))) \
 	-O2 -g -fPIC -fno-strict-aliasing -fno-common -fno-builtin -G 0 \
-	-DDISABLE_BRANCH_PROFILING \
+	-fno-stack-protector -fno-jump-tables -DDISABLE_BRANCH_PROFILING \
 	$(call cc-option, -fno-asynchronous-unwind-tables) \
 	$(call cc-option, -fno-stack-protector)
 aflags-vdso := $(ccflags-vdso) \
 	-D__ASSEMBLY__ -Wa,-gdwarf-2
 
+ifneq ($(c-gettimeofday-y),)
+CFLAGS_vgettimeofday.o = -include $(c-gettimeofday-y)
+endif
+
 #
 # For the pre-R6 code in arch/mips/vdso/vdso.h for locating
 # the base address of VDSO, the linker will emit a R_MIPS_PC32
@@ -49,6 +63,8 @@ VDSO_LDFLAGS := \
 	$(call cc-ldoption, -Wl$(comma)--hash-style=sysv) \
 	$(call cc-ldoption, -Wl$(comma)--build-id)
 
+CFLAGS_REMOVE_vdso.o = -pg
+
 GCOV_PROFILE := n
 
 #
@@ -96,6 +112,7 @@ $(obj)/vdso.lds: KBUILD_CPPFLAGS := $(ccflags-vdso) $(native-abi)
 
 $(obj)/vdso.so.dbg.raw: $(obj)/vdso.lds $(obj-vdso) FORCE
 	$(call if_changed,vdsold)
+	$(call if_changed,vdso_check)
 
 $(obj)/vdso-image.c: $(obj)/vdso.so.dbg.raw $(obj)/vdso.so.raw \
                      $(obj)/genvdso FORCE
@@ -134,6 +151,7 @@ $(obj)/vdso-o32.lds: $(src)/vdso.lds.S FORCE
 
 $(obj)/vdso-o32.so.dbg.raw: $(obj)/vdso-o32.lds $(obj-vdso-o32) FORCE
 	$(call if_changed,vdsold)
+	$(call if_changed,vdso_check)
 
 $(obj)/vdso-o32-image.c: VDSO_NAME := o32
 $(obj)/vdso-o32-image.c: $(obj)/vdso-o32.so.dbg.raw $(obj)/vdso-o32.so.raw \
@@ -174,6 +192,7 @@ $(obj)/vdso-n32.lds: $(src)/vdso.lds.S FORCE
 
 $(obj)/vdso-n32.so.dbg.raw: $(obj)/vdso-n32.lds $(obj-vdso-n32) FORCE
 	$(call if_changed,vdsold)
+	$(call if_changed,vdso_check)
 
 $(obj)/vdso-n32-image.c: VDSO_NAME := n32
 $(obj)/vdso-n32-image.c: $(obj)/vdso-n32.so.dbg.raw $(obj)/vdso-n32.so.raw \

arch/mips/vdso/elf.S

@@ -8,7 +8,7 @@
  * option) any later version.
  */
 
-#include "vdso.h"
+#include <asm/vdso/vdso.h>
 
 #include <asm/isa-rev.h>
 

arch/mips/vdso/sigreturn.S

@@ -8,7 +8,7 @@
  * option) any later version.
  */
 
-#include "vdso.h"
+#include <asm/vdso/vdso.h>
 
 #include <uapi/asm/unistd.h>
 

arch/mips/vdso/vdso.lds.S

@@ -99,6 +99,8 @@ VERSION
 	global:
 		__vdso_clock_gettime;
 		__vdso_gettimeofday;
+		__vdso_clock_getres;
+		__vdso_time;
 #endif
 	local: *;
 	};

arch/mips/vdso/vgettimeofday.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * ARM64 compat userspace implementations of gettimeofday() and similar.
+ *
+ * Copyright (C) 2018 ARM Limited
+ *
+ */
+#include <linux/time.h>
+#include <linux/types.h>
+
+notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
+{
+	return __cvdso_clock_gettime(clock, ts);
+}
+
+notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
+{
+	return __cvdso_gettimeofday(tv, tz);
+}
+
+notrace time_t __vdso_time(time_t *time)
+{
+	return __cvdso_time(time);
+}
+
+notrace int __vdso_clock_getres(clockid_t clock_id, struct timespec *res)
+{
+	return __cvdso_clock_getres(clock_id, res);
+}
+