[PATCH v3 0/2] riscv: introduce vDSO common flow

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* [PATCH v3 0/2] riscv: introduce vDSO common flow
@ 2020-04-23  8:05 Vincent Chen
  2020-04-23  8:05 ` [PATCH v3 1/2] riscv: use vDSO common flow to reduce the latency of the time-related functions Vincent Chen
  2020-04-23  8:05 ` [PATCH v3 2/2] riscv: set the permission of vdso_data to read-only Vincent Chen
  0 siblings, 2 replies; 3+ messages in thread
From: Vincent Chen @ 2020-04-23  8:05 UTC (permalink / raw)
  To: paul.walmsley, palmer; +Cc: Vincent Chen, linux-riscv

Even if RISC-V has supported the vDSO feature, the latency of the functions
for obtaining the system time is still expensive. It is because these
functions still trigger a corresponding system call in the process, which
slows down the response time. If we want to remove the system call to
reduce the latency, the kernel should have the ability to output the system
clock information to userspace. This patch introduces the vDSO common flow
to enable the kernel to achieve the above feature and uses "rdtime"
instruction to obtain the current time in the user space. Under this
condition, the latency cost by the ecall from U-mode to S-mode can be
eliminated. After applying this patch, the latency of gettimeofday()
measured on the HiFive unleashed board can be reduced by %61.


change since v2:
1. Fix build errors that occurred in the case of rv32 and nommu.

change since v1:
1. Modify the permission of vdso_data to read-only

Vincent Chen (2):
  riscv: use vDSO common flow to reduce the latency of the time-related
    functions
  riscv: set the permission of vdso_data to read-only

 arch/riscv/Kconfig                         |  4 ++
 arch/riscv/include/asm/clocksource.h       |  7 +++
 arch/riscv/include/asm/processor.h         | 12 +----
 arch/riscv/include/asm/vdso.h              |  2 +
 arch/riscv/include/asm/vdso/clocksource.h  |  8 +++
 arch/riscv/include/asm/vdso/gettimeofday.h | 79 ++++++++++++++++++++++++++++++
 arch/riscv/include/asm/vdso/processor.h    | 19 +++++++
 arch/riscv/include/asm/vdso/vsyscall.h     | 27 ++++++++++
 arch/riscv/kernel/time.c                   |  9 ++++
 arch/riscv/kernel/vdso.c                   | 24 +++++++--
 arch/riscv/kernel/vdso/Makefile            | 12 +++--
 arch/riscv/kernel/vdso/clock_getres.S      | 18 -------
 arch/riscv/kernel/vdso/clock_gettime.S     | 18 -------
 arch/riscv/kernel/vdso/gettimeofday.S      | 18 -------
 arch/riscv/kernel/vdso/vdso.lds.S          |  2 +
 arch/riscv/kernel/vdso/vgettimeofday.c     | 25 ++++++++++
 16 files changed, 213 insertions(+), 71 deletions(-)
 create mode 100644 arch/riscv/include/asm/clocksource.h
 create mode 100644 arch/riscv/include/asm/vdso/clocksource.h
 create mode 100644 arch/riscv/include/asm/vdso/gettimeofday.h
 create mode 100644 arch/riscv/include/asm/vdso/processor.h
 create mode 100644 arch/riscv/include/asm/vdso/vsyscall.h
 delete mode 100644 arch/riscv/kernel/vdso/clock_getres.S
 delete mode 100644 arch/riscv/kernel/vdso/clock_gettime.S
 delete mode 100644 arch/riscv/kernel/vdso/gettimeofday.S
 create mode 100644 arch/riscv/kernel/vdso/vgettimeofday.c

-- 
2.7.4



^ permalink raw reply	[flat|nested] 3+ messages in thread

* [PATCH v3 1/2] riscv: use vDSO common flow to reduce the latency of the time-related functions
  2020-04-23  8:05 [PATCH v3 0/2] riscv: introduce vDSO common flow Vincent Chen
@ 2020-04-23  8:05 ` Vincent Chen
  2020-04-23  8:05 ` [PATCH v3 2/2] riscv: set the permission of vdso_data to read-only Vincent Chen
  1 sibling, 0 replies; 3+ messages in thread
From: Vincent Chen @ 2020-04-23  8:05 UTC (permalink / raw)
  To: paul.walmsley, palmer; +Cc: Vincent Chen, linux-riscv

Even if RISC-V has supported the vDSO feature, the latency of the functions
for obtaining the system time is still expensive. It is because these
functions still trigger a corresponding system call in the process, which
slows down the response time. If we want to remove the system call to
reduce the latency, the kernel should have the ability to output the system
clock information to userspace. This patch introduces the vDSO common flow
to enable the kernel to achieve the above feature and uses "rdtime"
instruction to obtain the current time in the user space. Under this
condition, the latency cost by the ecall from U-mode to S-mode can be
eliminated. After applying this patch, the latency of gettimeofday()
measured on the HiFive unleashed board can be reduced by %61.

Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
---
 arch/riscv/Kconfig                         |  4 ++
 arch/riscv/include/asm/clocksource.h       |  7 +++
 arch/riscv/include/asm/processor.h         | 12 +----
 arch/riscv/include/asm/vdso.h              |  2 +
 arch/riscv/include/asm/vdso/clocksource.h  |  8 +++
 arch/riscv/include/asm/vdso/gettimeofday.h | 79 ++++++++++++++++++++++++++++++
 arch/riscv/include/asm/vdso/processor.h    | 19 +++++++
 arch/riscv/include/asm/vdso/vsyscall.h     | 27 ++++++++++
 arch/riscv/kernel/time.c                   |  9 ++++
 arch/riscv/kernel/vdso.c                   |  8 ++-
 arch/riscv/kernel/vdso/Makefile            | 12 +++--
 arch/riscv/kernel/vdso/clock_getres.S      | 18 -------
 arch/riscv/kernel/vdso/clock_gettime.S     | 18 -------
 arch/riscv/kernel/vdso/gettimeofday.S      | 18 -------
 arch/riscv/kernel/vdso/vdso.lds.S          |  2 +
 arch/riscv/kernel/vdso/vgettimeofday.c     | 25 ++++++++++
 16 files changed, 199 insertions(+), 69 deletions(-)
 create mode 100644 arch/riscv/include/asm/clocksource.h
 create mode 100644 arch/riscv/include/asm/vdso/clocksource.h
 create mode 100644 arch/riscv/include/asm/vdso/gettimeofday.h
 create mode 100644 arch/riscv/include/asm/vdso/processor.h
 create mode 100644 arch/riscv/include/asm/vdso/vsyscall.h
 delete mode 100644 arch/riscv/kernel/vdso/clock_getres.S
 delete mode 100644 arch/riscv/kernel/vdso/clock_gettime.S
 delete mode 100644 arch/riscv/kernel/vdso/gettimeofday.S
 create mode 100644 arch/riscv/kernel/vdso/vgettimeofday.c

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index a197258595ef..3838b865b01b 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -68,6 +68,10 @@ config RISCV
 	select ARCH_HAS_GCOV_PROFILE_ALL
 	select HAVE_COPY_THREAD_TLS
 	select HAVE_ARCH_KASAN if MMU && 64BIT
+	select ARCH_CLOCKSOURCE_INIT
+	select GENERIC_TIME_VSYSCALL if MMU && 64BIT
+	select HAVE_GENERIC_VDSO if MMU && 64BIT
+	select GENERIC_GETTIMEOFDAY if HAVE_GENERIC_VDSO
 
 config ARCH_MMAP_RND_BITS_MIN
 	default 18 if 64BIT
diff --git a/arch/riscv/include/asm/clocksource.h b/arch/riscv/include/asm/clocksource.h
new file mode 100644
index 000000000000..482185566b0c
--- /dev/null
+++ b/arch/riscv/include/asm/clocksource.h
@@ -0,0 +1,7 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_CLOCKSOURCE_H
+#define _ASM_CLOCKSOURCE_H
+
+#include <asm/vdso/clocksource.h>
+
+#endif
diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
index 3ddb798264f1..d6117b316e2b 100644
--- a/arch/riscv/include/asm/processor.h
+++ b/arch/riscv/include/asm/processor.h
@@ -8,6 +8,8 @@
 
 #include <linux/const.h>
 
+#include <vdso/processor.h>
+
 #include <asm/ptrace.h>
 
 /*
@@ -58,16 +60,6 @@ static inline void release_thread(struct task_struct *dead_task)
 extern unsigned long get_wchan(struct task_struct *p);
 
 
-static inline void cpu_relax(void)
-{
-#ifdef __riscv_muldiv
-	int dummy;
-	/* In lieu of a halt instruction, induce a long-latency stall. */
-	__asm__ __volatile__ ("div %0, %0, zero" : "=r" (dummy));
-#endif
-	barrier();
-}
-
 static inline void wait_for_interrupt(void)
 {
 	__asm__ __volatile__ ("wfi");
diff --git a/arch/riscv/include/asm/vdso.h b/arch/riscv/include/asm/vdso.h
index 7a7fce63c474..8454f746bbfd 100644
--- a/arch/riscv/include/asm/vdso.h
+++ b/arch/riscv/include/asm/vdso.h
@@ -10,8 +10,10 @@
 
 #include <linux/types.h>
 
+#ifndef GENERIC_TIME_VSYSCALL
 struct vdso_data {
 };
+#endif
 
 /*
  * The VDSO symbols are mapped into Linux so we can just use regular symbol
diff --git a/arch/riscv/include/asm/vdso/clocksource.h b/arch/riscv/include/asm/vdso/clocksource.h
new file mode 100644
index 000000000000..df6ea65c1dec
--- /dev/null
+++ b/arch/riscv/include/asm/vdso/clocksource.h
@@ -0,0 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ASM_VDSOCLOCKSOURCE_H
+#define __ASM_VDSOCLOCKSOURCE_H
+
+#define VDSO_ARCH_CLOCKMODES	\
+	VDSO_CLOCKMODE_ARCHTIMER
+
+#endif
diff --git a/arch/riscv/include/asm/vdso/gettimeofday.h b/arch/riscv/include/asm/vdso/gettimeofday.h
new file mode 100644
index 000000000000..c8e818688ec1
--- /dev/null
+++ b/arch/riscv/include/asm/vdso/gettimeofday.h
@@ -0,0 +1,79 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ASM_VDSO_GETTIMEOFDAY_H
+#define __ASM_VDSO_GETTIMEOFDAY_H
+
+#ifndef __ASSEMBLY__
+
+#include <asm/unistd.h>
+#include <asm/csr.h>
+#include <uapi/linux/time.h>
+
+#define VDSO_HAS_CLOCK_GETRES	1
+
+static __always_inline
+int gettimeofday_fallback(struct __kernel_old_timeval *_tv,
+			  struct timezone *_tz)
+{
+	register struct __kernel_old_timeval *tv asm("a0") = _tv;
+	register struct timezone *tz asm("a1") = _tz;
+	register long ret asm("a0");
+	register long nr asm("a7") = __NR_gettimeofday;
+
+	asm volatile ("ecall\n"
+		      : "=r" (ret)
+		      : "r"(tv), "r"(tz), "r"(nr)
+		      : "memory");
+
+	return ret;
+}
+
+static __always_inline
+long clock_gettime_fallback(clockid_t _clkid, struct __kernel_timespec *_ts)
+{
+	register clockid_t clkid asm("a0") = _clkid;
+	register struct __kernel_timespec *ts asm("a1") = _ts;
+	register long ret asm("a0");
+	register long nr asm("a7") = __NR_clock_gettime;
+
+	asm volatile ("ecall\n"
+		      : "=r" (ret)
+		      : "r"(clkid), "r"(ts), "r"(nr)
+		      : "memory");
+
+	return ret;
+}
+
+static __always_inline
+int clock_getres_fallback(clockid_t _clkid, struct __kernel_timespec *_ts)
+{
+	register clockid_t clkid asm("a0") = _clkid;
+	register struct __kernel_timespec *ts asm("a1") = _ts;
+	register long ret asm("a0");
+	register long nr asm("a7") = __NR_clock_getres;
+
+	asm volatile ("ecall\n"
+		      : "=r" (ret)
+		      : "r"(clkid), "r"(ts), "r"(nr)
+		      : "memory");
+
+	return ret;
+}
+
+static __always_inline u64 __arch_get_hw_counter(s32 clock_mode)
+{
+	/*
+	 * The purpose of csr_read(CSR_TIME) is to trap the system into
+	 * M-mode to obtain the value of CSR_TIME. Hence, unlike other
+	 * architecture, no fence instructions surround the csr_read()
+	 */
+	return csr_read(CSR_TIME);
+}
+
+static __always_inline const struct vdso_data *__arch_get_vdso_data(void)
+{
+	return _vdso_data;
+}
+
+#endif /* !__ASSEMBLY__ */
+
+#endif /* __ASM_VDSO_GETTIMEOFDAY_H */
diff --git a/arch/riscv/include/asm/vdso/processor.h b/arch/riscv/include/asm/vdso/processor.h
new file mode 100644
index 000000000000..82a5693b1861
--- /dev/null
+++ b/arch/riscv/include/asm/vdso/processor.h
@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef __ASM_VDSO_PROCESSOR_H
+#define __ASM_VDSO_PROCESSOR_H
+
+#ifndef __ASSEMBLY__
+
+static inline void cpu_relax(void)
+{
+#ifdef __riscv_muldiv
+	int dummy;
+	/* In lieu of a halt instruction, induce a long-latency stall. */
+	__asm__ __volatile__ ("div %0, %0, zero" : "=r" (dummy));
+#endif
+	barrier();
+}
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* __ASM_VDSO_PROCESSOR_H */
diff --git a/arch/riscv/include/asm/vdso/vsyscall.h b/arch/riscv/include/asm/vdso/vsyscall.h
new file mode 100644
index 000000000000..82fd5d83bd60
--- /dev/null
+++ b/arch/riscv/include/asm/vdso/vsyscall.h
@@ -0,0 +1,27 @@
+/* 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 *__riscv_get_k_vdso_data(void)
+{
+	return vdso_data;
+}
+
+#define __arch_get_k_vdso_data __riscv_get_k_vdso_data
+
+/* 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 */
diff --git a/arch/riscv/kernel/time.c b/arch/riscv/kernel/time.c
index 6a53c02e9c73..4d3a1048ad8b 100644
--- a/arch/riscv/kernel/time.c
+++ b/arch/riscv/kernel/time.c
@@ -26,3 +26,12 @@ void __init time_init(void)
 	lpj_fine = riscv_timebase / HZ;
 	timer_probe();
 }
+
+void clocksource_arch_init(struct clocksource *cs)
+{
+#ifdef CONFIG_GENERIC_GETTIMEOFDAY
+	cs->vdso_clock_mode = VDSO_CLOCKMODE_ARCHTIMER;
+#else
+	cs->vdso_clock_mode = VDSO_CLOCKMODE_NONE;
+#endif
+}
diff --git a/arch/riscv/kernel/vdso.c b/arch/riscv/kernel/vdso.c
index 484d95a70907..70b6461a6387 100644
--- a/arch/riscv/kernel/vdso.c
+++ b/arch/riscv/kernel/vdso.c
@@ -11,8 +11,12 @@
 #include <linux/slab.h>
 #include <linux/binfmts.h>
 #include <linux/err.h>
-
+#include <asm/page.h>
+#ifdef GENERIC_TIME_VSYSCALL
+#include <vdso/datapage.h>
+#else
 #include <asm/vdso.h>
+#endif
 
 extern char vdso_start[], vdso_end[];
 
@@ -26,7 +30,7 @@ static union {
 	struct vdso_data	data;
 	u8			page[PAGE_SIZE];
 } vdso_data_store __page_aligned_data;
-static struct vdso_data *vdso_data = &vdso_data_store.data;
+struct vdso_data *vdso_data = &vdso_data_store.data;
 
 static int __init vdso_init(void)
 {
diff --git a/arch/riscv/kernel/vdso/Makefile b/arch/riscv/kernel/vdso/Makefile
index 33b16f4212f7..9ad681e94ebe 100644
--- a/arch/riscv/kernel/vdso/Makefile
+++ b/arch/riscv/kernel/vdso/Makefile
@@ -1,12 +1,14 @@
 # SPDX-License-Identifier: GPL-2.0-only
 # Copied from arch/tile/kernel/vdso/Makefile
 
+# Absolute relocation type $(ARCH_REL_TYPE_ABS) needs to be defined before
+# the inclusion of generic Makefile.
+ARCH_REL_TYPE_ABS := R_RISCV_32|R_RISCV_64|R_RISCV_JUMP_SLOT
+include $(srctree)/lib/vdso/Makefile
 # Symbols present in the vdso
 vdso-syms  = rt_sigreturn
 ifdef CONFIG_64BIT
-vdso-syms += gettimeofday
-vdso-syms += clock_gettime
-vdso-syms += clock_getres
+vdso-syms += vgettimeofday
 endif
 vdso-syms += getcpu
 vdso-syms += flush_icache
@@ -14,6 +16,10 @@ vdso-syms += flush_icache
 # Files to link into the vdso
 obj-vdso = $(patsubst %, %.o, $(vdso-syms))
 
+ifneq ($(c-gettimeofday-y),)
+  CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y)
+endif
+
 # Build rules
 targets := $(obj-vdso) vdso.so vdso.so.dbg vdso.lds vdso-dummy.o
 obj-vdso := $(addprefix $(obj)/, $(obj-vdso))
diff --git a/arch/riscv/kernel/vdso/clock_getres.S b/arch/riscv/kernel/vdso/clock_getres.S
deleted file mode 100644
index 91378a52eb22..000000000000
--- a/arch/riscv/kernel/vdso/clock_getres.S
+++ /dev/null
@@ -1,18 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0-only */
-/*
- * Copyright (C) 2017 SiFive
- */
-
-#include <linux/linkage.h>
-#include <asm/unistd.h>
-
-	.text
-/* int __vdso_clock_getres(clockid_t clock_id, struct timespec *res); */
-ENTRY(__vdso_clock_getres)
-	.cfi_startproc
-	/* For now, just do the syscall. */
-	li a7, __NR_clock_getres
-	ecall
-	ret
-	.cfi_endproc
-ENDPROC(__vdso_clock_getres)
diff --git a/arch/riscv/kernel/vdso/clock_gettime.S b/arch/riscv/kernel/vdso/clock_gettime.S
deleted file mode 100644
index 5371fd9bc01f..000000000000
--- a/arch/riscv/kernel/vdso/clock_gettime.S
+++ /dev/null
@@ -1,18 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0-only */
-/*
- * Copyright (C) 2017 SiFive
- */
-
-#include <linux/linkage.h>
-#include <asm/unistd.h>
-
-	.text
-/* int __vdso_clock_gettime(clockid_t clock_id, struct timespec *tp); */
-ENTRY(__vdso_clock_gettime)
-	.cfi_startproc
-	/* For now, just do the syscall. */
-	li a7, __NR_clock_gettime
-	ecall
-	ret
-	.cfi_endproc
-ENDPROC(__vdso_clock_gettime)
diff --git a/arch/riscv/kernel/vdso/gettimeofday.S b/arch/riscv/kernel/vdso/gettimeofday.S
deleted file mode 100644
index e6fb8af88632..000000000000
--- a/arch/riscv/kernel/vdso/gettimeofday.S
+++ /dev/null
@@ -1,18 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0-only */
-/*
- * Copyright (C) 2017 SiFive
- */
-
-#include <linux/linkage.h>
-#include <asm/unistd.h>
-
-	.text
-/* int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz); */
-ENTRY(__vdso_gettimeofday)
-	.cfi_startproc
-	/* For now, just do the syscall. */
-	li a7, __NR_gettimeofday
-	ecall
-	ret
-	.cfi_endproc
-ENDPROC(__vdso_gettimeofday)
diff --git a/arch/riscv/kernel/vdso/vdso.lds.S b/arch/riscv/kernel/vdso/vdso.lds.S
index f66a091cb890..e6f558bca71b 100644
--- a/arch/riscv/kernel/vdso/vdso.lds.S
+++ b/arch/riscv/kernel/vdso/vdso.lds.S
@@ -2,11 +2,13 @@
 /*
  * Copyright (C) 2012 Regents of the University of California
  */
+#include <asm/page.h>
 
 OUTPUT_ARCH(riscv)
 
 SECTIONS
 {
+	PROVIDE(_vdso_data = . + PAGE_SIZE);
 	. = SIZEOF_HEADERS;
 
 	.hash		: { *(.hash) }			:text
diff --git a/arch/riscv/kernel/vdso/vgettimeofday.c b/arch/riscv/kernel/vdso/vgettimeofday.c
new file mode 100644
index 000000000000..d264943e2e47
--- /dev/null
+++ b/arch/riscv/kernel/vdso/vgettimeofday.c
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copied from arch/arm64/kernel/vdso/vgettimeofday.c
+ *
+ * Copyright (C) 2018 ARM Ltd.
+ * Copyright (C) 2020 SiFive
+ */
+
+#include <linux/time.h>
+#include <linux/types.h>
+
+int __vdso_clock_gettime(clockid_t clock, struct __kernel_timespec *ts)
+{
+	return __cvdso_clock_gettime(clock, ts);
+}
+
+int __vdso_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz)
+{
+	return __cvdso_gettimeofday(tv, tz);
+}
+
+int __vdso_clock_getres(clockid_t clock_id, struct __kernel_timespec *res)
+{
+	return __cvdso_clock_getres(clock_id, res);
+}
-- 
2.7.4



^ permalink raw reply related	[flat|nested] 3+ messages in thread

* [PATCH v3 2/2] riscv: set the permission of vdso_data to read-only
  2020-04-23  8:05 [PATCH v3 0/2] riscv: introduce vDSO common flow Vincent Chen
  2020-04-23  8:05 ` [PATCH v3 1/2] riscv: use vDSO common flow to reduce the latency of the time-related functions Vincent Chen
@ 2020-04-23  8:05 ` Vincent Chen
  1 sibling, 0 replies; 3+ messages in thread
From: Vincent Chen @ 2020-04-23  8:05 UTC (permalink / raw)
  To: paul.walmsley, palmer; +Cc: Vincent Chen, linux-riscv

The original vdso_data page is empty, so the permission of the vdso_data
page can be the same with the vdso text page. After introducing the vDSO
common flow, the vdso_data is not empty and the permission should be
changed to read-only.

Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
---
 arch/riscv/kernel/vdso.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/kernel/vdso.c b/arch/riscv/kernel/vdso.c
index 70b6461a6387..94450332aa4f 100644
--- a/arch/riscv/kernel/vdso.c
+++ b/arch/riscv/kernel/vdso.c
@@ -79,13 +79,22 @@ int arch_setup_additional_pages(struct linux_binprm *bprm,
 	 */
 	mm->context.vdso = (void *)vdso_base;
 
-	ret = install_special_mapping(mm, vdso_base, vdso_len,
+	ret =
+	   install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT,
 		(VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC),
 		vdso_pagelist);
 
-	if (unlikely(ret))
+	if (unlikely(ret)) {
 		mm->context.vdso = NULL;
+		goto end;
+	}
 
+	vdso_base += (vdso_pages << PAGE_SHIFT);
+	ret = install_special_mapping(mm, vdso_base, PAGE_SIZE,
+		(VM_READ | VM_MAYREAD), &vdso_pagelist[vdso_pages]);
+
+	if (unlikely(ret))
+		mm->context.vdso = NULL;
 end:
 	up_write(&mm->mmap_sem);
 	return ret;
@@ -95,5 +104,8 @@ const char *arch_vma_name(struct vm_area_struct *vma)
 {
 	if (vma->vm_mm && (vma->vm_start == (long)vma->vm_mm->context.vdso))
 		return "[vdso]";
+	if (vma->vm_mm && (vma->vm_start ==
+			   (long)vma->vm_mm->context.vdso + PAGE_SIZE))
+		return "[vdso_data]";
 	return NULL;
 }
-- 
2.7.4



^ permalink raw reply related	[flat|nested] 3+ messages in thread

end of thread, other threads:[~2020-04-23  8:05 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2020-04-23  8:05 [PATCH v3 0/2] riscv: introduce vDSO common flow Vincent Chen
2020-04-23  8:05 ` [PATCH v3 1/2] riscv: use vDSO common flow to reduce the latency of the time-related functions Vincent Chen
2020-04-23  8:05 ` [PATCH v3 2/2] riscv: set the permission of vdso_data to read-only Vincent Chen

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