mips: Add support for generic vDSO

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

Introduce the following changes:
 - Modification of vdso.c to be compliant with the common vdso datapage
 - Use of lib/vdso for gettimeofday

Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Burton <paul.burton@mips.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
[paul.burton@mips.com: Prepend $(src) to config-n32-o32-env.c path.]
Signed-off-by: Paul Burton <paul.burton@mips.com>

arch/mips/Kconfig

@@ -22,6 +22,7 @@ config MIPS
 	select GENERIC_CLOCKEVENTS
 	select GENERIC_CMOS_UPDATE
 	select GENERIC_CPU_AUTOPROBE
+	select GENERIC_GETTIMEOFDAY
 	select GENERIC_IOMAP
 	select GENERIC_IRQ_PROBE
 	select GENERIC_IRQ_SHOW
@@ -74,6 +75,7 @@ config MIPS
 	select HAVE_STACKPROTECTOR
 	select HAVE_SYSCALL_TRACEPOINTS
 	select HAVE_VIRT_CPU_ACCOUNTING_GEN if 64BIT || !SMP
+	select HAVE_GENERIC_VDSO
 	select IRQ_FORCED_THREADING
 	select ISA if EISA
 	select MODULES_USE_ELF_RELA if MODULES && 64BIT

arch/mips/include/asm/vdso.h

@@ -8,6 +8,7 @@
 #define __ASM_VDSO_H
 
 #include <linux/mm_types.h>
+#include <vdso/datapage.h>
 
 #include <asm/barrier.h>
 
@@ -49,84 +50,9 @@ extern struct mips_vdso_image vdso_image_o32;
 extern struct mips_vdso_image vdso_image_n32;
 #endif
 
-/**
- * union mips_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).
- * @cs_shift:		Clocksource shift value.
- * @clock_mode:		Clocksource to use for time functions.
- * @cs_mult:		Clocksource multiplier value.
- * @cs_cycle_last:	Clock cycle value at last update.
- * @cs_mask:		Clocksource mask value.
- * @tz_minuteswest:	Minutes west of Greenwich (from timezone).
- * @tz_dsttime:		Type of DST correction (from timezone).
- *
- * This structure contains data needed by functions within the VDSO. It is
- * populated by the kernel and mapped read-only into user memory. The time
- * fields are mirrors of internal data from the timekeeping infrastructure.
- *
- * Note: Care should be taken when modifying as the layout must remain the same
- * 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[CS_BASES];
 	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)
-{
-	++data->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)
-{
-	/* Ensure data values are written before updating sequence again. */
-	smp_wmb();
-	++data->seq_count;
-}
-
 #endif /* __ASM_VDSO_H */

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

@@ -0,0 +1,151 @@
+/*
+ * Copyright (C) 2018 ARM Limited
+ * Copyright (C) 2015 Imagination Technologies
+ * Author: Alex Smith <alex.smith@imgtec.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * 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
+
+#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>
+#include <asm/vdso.h>
+
+#ifdef CONFIG_MIPS_CLOCK_VSYSCALL
+
+static __always_inline long gettimeofday_fallback(
+				struct __kernel_old_timeval *_tv,
+				struct timezone *_tz)
+{
+	register struct timezone *tz asm("a1") = _tz;
+	register struct __kernel_old_timeval *tv asm("a0") = _tv;
+	register long ret asm("v0");
+	register long nr asm("v0") = __NR_gettimeofday;
+	register long error asm("a3");
+
+	asm volatile(
+	"       syscall\n"
+	: "=r" (ret), "=r" (error)
+	: "r" (tv), "r" (tz), "r" (nr)
+	: "$1", "$3", "$8", "$9", "$10", "$11", "$12", "$13",
+	  "$14", "$15", "$24", "$25", "hi", "lo", "memory");
+
+	return error ? -ret : ret;
+}
+
+#else
+
+static __always_inline long gettimeofday_fallback(
+				struct __kernel_old_timeval *_tv,
+				struct timezone *_tz)
+{
+	return -1;
+}
+
+#endif
+
+static __always_inline long clock_gettime_fallback(
+					clockid_t _clkid,
+					struct __kernel_timespec *_ts)
+{
+	register struct __kernel_timespec *ts asm("a1") = _ts;
+	register clockid_t clkid asm("a0") = _clkid;
+	register long ret asm("v0");
+#if _MIPS_SIM == _MIPS_SIM_ABI64
+	register long nr asm("v0") = __NR_clock_gettime;
+#else
+	register long nr asm("v0") = __NR_clock_gettime64;
+#endif
+	register long error asm("a3");
+
+	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 error ? -ret : ret;
+}
+
+#ifdef CONFIG_CSRC_R4K
+
+static __always_inline u64 read_r4k_count(void)
+{
+	unsigned int count;
+
+	__asm__ __volatile__(
+	"	.set push\n"
+	"	.set mips32r2\n"
+	"	rdhwr	%0, $2\n"
+	"	.set pop\n"
+	: "=r" (count));
+
+	return count;
+}
+
+#endif
+
+#ifdef CONFIG_CLKSRC_MIPS_GIC
+
+static __always_inline u64 read_gic_count(const struct vdso_data *data)
+{
+	void __iomem *gic = get_gic(data);
+	u32 hi, hi2, lo;
+
+	do {
+		hi = __raw_readl(gic + sizeof(lo));
+		lo = __raw_readl(gic);
+		hi2 = __raw_readl(gic + sizeof(lo));
+	} while (hi2 != hi);
+
+	return (((u64)hi) << 32) + lo;
+}
+
+#endif
+
+static __always_inline u64 __arch_get_hw_counter(s32 clock_mode)
+{
+#ifdef CONFIG_CLKSRC_MIPS_GIC
+	const struct vdso_data *data = get_vdso_data();
+#endif
+	u64 cycle_now;
+
+	switch (clock_mode) {
+#ifdef CONFIG_CSRC_R4K
+	case VDSO_CLOCK_R4K:
+		cycle_now = read_r4k_count();
+		break;
+#endif
+#ifdef CONFIG_CLKSRC_MIPS_GIC
+	case VDSO_CLOCK_GIC:
+		cycle_now = read_gic_count(data);
+		break;
+#endif
+	default:
+		cycle_now = 0;
+		break;
+	}
+
+	return cycle_now;
+}
+
+static __always_inline const struct vdso_data *__arch_get_vdso_data(void)
+{
+	return get_vdso_data();
+}
+
+#endif /* !__ASSEMBLY__ */
+
+#endif /* __ASM_VDSO_GETTIMEOFDAY_H */

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

@@ -68,14 +68,14 @@ 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/include/asm/vdso/vsyscall.h

@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ASM_VDSO_VSYSCALL_H
+#define __ASM_VDSO_VSYSCALL_H
+
+#ifndef __ASSEMBLY__
+
+#include <linux/timekeeper_internal.h>
+#include <vdso/datapage.h>
+
+extern struct vdso_data *vdso_data;
+
+/*
+ * Update the vDSO data page to keep in sync with kernel timekeeping.
+ */
+static __always_inline
+struct vdso_data *__mips_get_k_vdso_data(void)
+{
+	return vdso_data;
+}
+#define __arch_get_k_vdso_data __mips_get_k_vdso_data
+
+static __always_inline
+int __mips_get_clock_mode(struct timekeeper *tk)
+{
+	u32 clock_mode = tk->tkr_mono.clock->archdata.vdso_clock_mode;
+
+	return clock_mode;
+}
+#define __arch_get_clock_mode __mips_get_clock_mode
+
+static __always_inline
+int __mips_use_vsyscall(struct vdso_data *vdata)
+{
+	return (vdata[CS_HRES_COARSE].clock_mode != VDSO_CLOCK_NONE);
+}
+#define __arch_use_vsyscall __mips_use_vsyscall
+
+/* The asm-generic header needs to be included after the definitions above */
+#include <asm-generic/vdso/vsyscall.h>
+
+#endif /* !__ASSEMBLY__ */
+
+#endif /* __ASM_VDSO_VSYSCALL_H */

arch/mips/kernel/vdso.c

@@ -20,9 +20,12 @@
 #include <asm/mips-cps.h>
 #include <asm/page.h>
 #include <asm/vdso.h>
+#include <vdso/helpers.h>
+#include <vdso/vsyscall.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;
+struct vdso_data *vdso_data = mips_vdso_data.data;
 
 /*
  * Mapping for the VDSO data/GIC pages. The real pages are mapped manually, as
@@ -66,34 +69,6 @@ static int __init init_vdso(void)
 }
 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_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;
-	}
-}
-
 static unsigned long vdso_base(void)
 {
 	unsigned long base;
@@ -163,7 +138,7 @@ 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;
@@ -189,7 +164,7 @@ 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;