[PATCH v2 24/28] arm: Add support for generic vDSO

Vincenzo Frascino
2018-11-29T17:11:02Z

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

This patch introduces the following changes:
- Modification vdso.c to be compliant with the common vdso datapage
- Use of lib/vdso for gettimeofday
- Implementation of elf note

Cc: Russell King <linux@armlinux.org.uk>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
---
arch/arm/Kconfig | 4 +
arch/arm/include/asm/vdso/gettimeofday.h | 82 +++++++
arch/arm/include/asm/vdso_datapage.h | 25 +--
arch/arm/kernel/vdso.c | 28 ++-
arch/arm/vdso/Makefile | 13 +-
arch/arm/vdso/note.c | 15 ++
arch/arm/vdso/vdso.lds.S | 1 +
arch/arm/vdso/vgettimeofday.c | 267 ++---------------------
8 files changed, 146 insertions(+), 289 deletions(-)
create mode 100644 arch/arm/include/asm/vdso/gettimeofday.h
create mode 100644 arch/arm/vdso/note.c

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 91be74d8df65..ebcbdcf02283 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -47,6 +47,8 @@ config ARM
select GENERIC_SMP_IDLE_THREAD
select GENERIC_STRNCPY_FROM_USER
select GENERIC_STRNLEN_USER
+ select GENERIC_GETTIMEOFDAY
+ select GENERIC_VDSO_32
select HANDLE_DOMAIN_IRQ
select HARDIRQS_SW_RESEND
select HAVE_ARCH_AUDITSYSCALL if (AEABI && !OABI_COMPAT)
@@ -96,6 +98,7 @@ config ARM
select HAVE_SYSCALL_TRACEPOINTS
select HAVE_UID16
select HAVE_VIRT_CPU_ACCOUNTING_GEN
+ select HAVE_GENERIC_VDSO
select IRQ_FORCED_THREADING
select MODULES_USE_ELF_REL
select NEED_DMA_MAP_STATE
@@ -1353,6 +1356,7 @@ config HAVE_ARM_ARCH_TIMER
bool "Architected timer support"
depends on CPU_V7
select ARM_ARCH_TIMER
+ select HAVE_ARCH_TIMER
select GENERIC_CLOCKEVENTS
help
This option enables support for the ARM architected timer
diff --git a/arch/arm/include/asm/vdso/gettimeofday.h b/arch/arm/include/asm/vdso/gettimeofday.h
new file mode 100644
index 000000000000..ccc4dccfd7b2
--- /dev/null
+++ b/arch/arm/include/asm/vdso/gettimeofday.h
@@ -0,0 +1,82 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2018 ARM Limited
+ */
+#ifndef __ASM_VDSO_GETTIMEOFDAY_H
+#define __ASM_VDSO_GETTIMEOFDAY_H
+
+#ifndef __ASSEMBLY__
+
+#include <asm/arch_timer.h>
+#include <asm/unistd.h>
+#include <uapi/linux/time.h>
+
+extern struct vdso_data *__get_datapage(void);
+
+static __always_inline notrace int gettimeofday_fallback(
+ struct __vdso_timeval *_tv,
+ struct timezone *_tz)
+{
+ register struct timezone *tz asm("r1") = _tz;
+ register struct __vdso_timeval *tv asm("r0") = _tv;
+ register long ret asm ("r0");
+ register long nr asm("r7") = __NR_gettimeofday;
+
+ asm volatile(
+ " swi #0\n"
+ : "=r" (ret)
+ : "r" (tv), "r" (tz), "r" (nr)
+ : "memory");
+
+ return ret;
+}
+
+static __always_inline notrace long clock_gettime_fallback(
+ clockid_t _clkid,
+ struct __vdso_timespec *_ts)
+{
+ register struct __vdso_timespec *ts asm("r1") = _ts;
+ register clockid_t clkid asm("r0") = _clkid;
+ register long ret asm ("r0");
+ register long nr asm("r7") = __NR_clock_gettime;
+
+ asm volatile(
+ " swi #0\n"
+ : "=r" (ret)
+ : "r" (clkid), "r" (ts), "r" (nr)
+ : "memory");
+
+ return ret;
+}
+
+static __always_inline notrace int clock_getres_fallback(
+ clockid_t _clkid,
+ struct __vdso_timespec *_ts)
+{
+ register struct __vdso_timespec *ts asm("r1") = _ts;
+ register clockid_t clkid asm("r0") = _clkid;
+ register long ret asm ("r0");
+ register long nr asm("r7") = __NR_clock_getres;
+
+ asm volatile(
+ " swi #0\n"
+ : "=r" (ret)
+ : "r" (clkid), "r" (ts), "r" (nr)
+ : "memory");
+
+ return ret;
+}
+
+static __always_inline notrace u64 clock_get_virtual_counter(void)
+{
+ return arch_counter_get_cntvct();
+}
+
+static __always_inline notrace const struct vdso_data *__arch_get_vdso_data(void)
+{
+ return __get_datapage();
+}
+
+#endif /* !__ASSEMBLY__ */
+
+#endif /* __ASM_VDSO_GETTIMEOFDAY_H */
diff --git a/arch/arm/include/asm/vdso_datapage.h b/arch/arm/include/asm/vdso_datapage.h
index 9be259442fca..b31df2467827 100644
--- a/arch/arm/include/asm/vdso_datapage.h
+++ b/arch/arm/include/asm/vdso_datapage.h
@@ -22,32 +22,9 @@

#ifndef __ASSEMBLY__

+#include <vdso/datapage.h>
#include <asm/page.h>

-/* Try to be cache-friendly on systems that don't implement the
- * generic timer: fit the unconditionally updated fields in the first
- * 32 bytes.
- */
-struct vdso_data {
- u32 seq_count; /* sequence count - odd during updates */
- u16 tk_is_cntvct; /* fall back to syscall if false */
- u16 cs_shift; /* clocksource shift */
- u32 xtime_coarse_sec; /* coarse time */
- u32 xtime_coarse_nsec;
-
- u32 wtm_clock_sec; /* wall to monotonic offset */
- u32 wtm_clock_nsec;
- u32 xtime_clock_sec; /* CLOCK_REALTIME - seconds */
- u32 cs_mult; /* clocksource multiplier */
-
- u64 cs_cycle_last; /* last cycle value */
- u64 cs_mask; /* clocksource mask */
-
- u64 xtime_clock_snsec; /* CLOCK_REALTIME sub-ns base */
- u32 tz_minuteswest; /* timezone info for gettimeofday(2) */
- u32 tz_dsttime;
-};
-
union vdso_data_store {
struct vdso_data data;
u8 page[PAGE_SIZE];
diff --git a/arch/arm/kernel/vdso.c b/arch/arm/kernel/vdso.c
index f4dd7f9663c1..b26fb6a1d5c7 100644
--- a/arch/arm/kernel/vdso.c
+++ b/arch/arm/kernel/vdso.c
@@ -276,14 +276,14 @@ void arm_install_vdso(struct mm_struct *mm, unsigned long addr)

static void vdso_write_begin(struct vdso_data *vdata)
{
- ++vdso_data->seq_count;
+ ++vdso_data->tb_seq_count;
smp_wmb(); /* Pairs with smp_rmb in vdso_read_retry */
}

static void vdso_write_end(struct vdso_data *vdata)
{
smp_wmb(); /* Pairs with smp_rmb in vdso_read_begin */
- ++vdso_data->seq_count;
+ ++vdso_data->tb_seq_count;
}

static bool tk_is_cntvct(const struct timekeeper *tk)
@@ -307,10 +307,10 @@ static bool tk_is_cntvct(const struct timekeeper *tk)
* counter again, making it even, indicating to userspace that the
* update is finished.
*
- * Userspace is expected to sample seq_count before reading any other
- * fields from the data page. If seq_count is odd, userspace is
+ * Userspace is expected to sample tb_seq_count before reading any other
+ * fields from the data page. If tb_seq_count is odd, userspace is
* expected to wait until it becomes even. After copying data from
- * the page, userspace must sample seq_count again; if it has changed
+ * the page, userspace must sample tb_seq_count again; if it has changed
* from its previous value, userspace must retry the whole sequence.
*
* Calls to update_vsyscall are serialized by the timekeeping core.
@@ -318,6 +318,7 @@ static bool tk_is_cntvct(const struct timekeeper *tk)
void update_vsyscall(struct timekeeper *tk)
{
struct timespec64 *wtm = &tk->wall_to_monotonic;
+ u32 __tk_is_cntvct = tk_is_cntvct(tk);

if (!cntvct_ok) {
/* The entry points have been zeroed, so there is no
@@ -328,20 +329,27 @@ void update_vsyscall(struct timekeeper *tk)

vdso_write_begin(vdso_data);

- vdso_data->tk_is_cntvct = tk_is_cntvct(tk);
+ vdso_data->use_syscall = !__tk_is_cntvct;
vdso_data->xtime_coarse_sec = tk->xtime_sec;
vdso_data->xtime_coarse_nsec = (u32)(tk->tkr_mono.xtime_nsec >>
tk->tkr_mono.shift);
vdso_data->wtm_clock_sec = wtm->tv_sec;
vdso_data->wtm_clock_nsec = wtm->tv_nsec;

- if (vdso_data->tk_is_cntvct) {
+ if (__tk_is_cntvct) {
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_snsec = tk->tkr_mono.xtime_nsec;
- vdso_data->cs_mult = tk->tkr_mono.mult;
+ 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->cs_mask = tk->tkr_mono.mask;
+ 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_raw.mask;
}

vdso_write_end(vdso_data);
diff --git a/arch/arm/vdso/Makefile b/arch/arm/vdso/Makefile
index f4efff9d3afb..05f8c6699d48 100644
--- a/arch/arm/vdso/Makefile
+++ b/arch/arm/vdso/Makefile
@@ -1,7 +1,13 @@
# SPDX-License-Identifier: GPL-2.0
+
+# Absolute relocation type $(ARCH_REL_TYPE_ABS) needs to be defined before
+# the inclusion of generic Makefile.
+ARCH_REL_TYPE_ABS := R_ARM_JUMP_SLOT|R_ARM_GLOB_DAT|R_ARM_ABS32
+include $(srctree)/lib/vdso/Makefile
+
hostprogs-y := vdsomunge

-obj-vdso := vgettimeofday.o datapage.o
+obj-vdso := vgettimeofday.o datapage.o note.o

# Build rules
targets := $(obj-vdso) vdso.so vdso.so.dbg vdso.so.raw vdso.lds
@@ -25,7 +31,11 @@ CFLAGS_REMOVE_vdso.o = -pg

# Force -O2 to avoid libgcc dependencies
CFLAGS_REMOVE_vgettimeofday.o = -pg -Os
+ifeq ($(c-gettimeofday-y),)
CFLAGS_vgettimeofday.o = -O2
+else
+CFLAGS_vgettimeofday.o = -O2 -include $(c-gettimeofday-y)
+endif

# Disable gcov profiling for VDSO code
GCOV_PROFILE := n
@@ -39,6 +49,7 @@ $(obj)/vdso.o : $(obj)/vdso.so
# Link rule for the .so file
$(obj)/vdso.so.raw: $(src)/vdso.lds $(obj-vdso) FORCE
$(call if_changed,vdsold)
+ $(call if_changed,vdso_check)

$(obj)/vdso.so.dbg: $(obj)/vdso.so.raw $(obj)/vdsomunge FORCE
$(call if_changed,vdsomunge)
diff --git a/arch/arm/vdso/note.c b/arch/arm/vdso/note.c
new file mode 100644
index 000000000000..eff5bf9efb8b
--- /dev/null
+++ b/arch/arm/vdso/note.c
@@ -0,0 +1,15 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2012-2018 ARM Limited
+ *
+ * This supplies .note.* sections to go into the PT_NOTE inside the vDSO text.
+ * Here we can supply some information useful to userland.
+ */
+
+#include <linux/uts.h>
+#include <linux/version.h>
+#include <linux/elfnote.h>
+#include <linux/build-salt.h>
+
+ELFNOTE32("Linux", 0, LINUX_VERSION_CODE);
+BUILD_SALT;
diff --git a/arch/arm/vdso/vdso.lds.S b/arch/arm/vdso/vdso.lds.S
index 89ca89f12d23..1d81e8c3acf6 100644
--- a/arch/arm/vdso/vdso.lds.S
+++ b/arch/arm/vdso/vdso.lds.S
@@ -82,6 +82,7 @@ VERSION
global:
__vdso_clock_gettime;
__vdso_gettimeofday;
+ __vdso_clock_getres;
local: *;
};
}
diff --git a/arch/arm/vdso/vgettimeofday.c b/arch/arm/vdso/vgettimeofday.c
index a9dd619c6c29..b470a8ed35a7 100644
--- a/arch/arm/vdso/vgettimeofday.c
+++ b/arch/arm/vdso/vgettimeofday.c
@@ -1,270 +1,29 @@
+// SPDX-License-Identifier: GPL-2.0
/*
- * Copyright 2015 Mentor Graphics Corporation.
+ * ARM64 compat userspace implementations of gettimeofday() and similar.
*
- * 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; version 2 of the
- * License.
+ * Copyright (C) 2018 ARM Limited
*
- * This program is distributed in the hope that it will be useful, but
- * WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- * General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
-
-#include <linux/compiler.h>
-#include <linux/hrtimer.h>
#include <linux/time.h>
-#include <asm/arch_timer.h>
-#include <asm/barrier.h>
-#include <asm/bug.h>
-#include <asm/page.h>
-#include <asm/unistd.h>
-#include <asm/vdso_datapage.h>
-
-#ifndef CONFIG_AEABI
-#error This code depends on AEABI system call conventions
-#endif
+#include <linux/types.h>

-extern struct vdso_data *__get_datapage(void);
-
-static notrace u32 __vdso_read_begin(const struct vdso_data *vdata)
+notrace int __vdso_clock_gettime(clockid_t clock,
+ struct __vdso_timespec *ts)
{
- u32 seq;
-repeat:
- seq = READ_ONCE(vdata->seq_count);
- if (seq & 1) {
- cpu_relax();
- goto repeat;
- }
- return seq;
+ return __cvdso_clock_gettime(clock, ts);
}

-static notrace u32 vdso_read_begin(const struct vdso_data *vdata)
+notrace int __vdso_gettimeofday(struct __vdso_timeval *tv,
+ struct timezone *tz)
{
- u32 seq;
-
- seq = __vdso_read_begin(vdata);
-
- smp_rmb(); /* Pairs with smp_wmb in vdso_write_end */
- return seq;
-}
-
-static notrace int vdso_read_retry(const struct vdso_data *vdata, u32 start)
-{
- smp_rmb(); /* Pairs with smp_wmb in vdso_write_begin */
- return vdata->seq_count != start;
-}
-
-static notrace long clock_gettime_fallback(clockid_t _clkid,
- struct timespec *_ts)
-{
- register struct timespec *ts asm("r1") = _ts;
- register clockid_t clkid asm("r0") = _clkid;
- register long ret asm ("r0");
- register long nr asm("r7") = __NR_clock_gettime;
-
- asm volatile(
- " swi #0\n"
- : "=r" (ret)
- : "r" (clkid), "r" (ts), "r" (nr)
- : "memory");
-
- return ret;
-}
-
-static notrace int do_realtime_coarse(struct timespec *ts,
- struct vdso_data *vdata)
-{
- u32 seq;
-
- do {
- seq = vdso_read_begin(vdata);
-
- ts->tv_sec = vdata->xtime_coarse_sec;
- ts->tv_nsec = vdata->xtime_coarse_nsec;
-
- } while (vdso_read_retry(vdata, seq));
-
- return 0;
+ return __cvdso_gettimeofday(tv, tz);
}

-static notrace int do_monotonic_coarse(struct timespec *ts,
- struct vdso_data *vdata)
+notrace int __vdso_clock_getres(clockid_t clock_id,
+ struct __vdso_timespec *res)
{
- struct timespec tomono;
- u32 seq;
-
- do {
- seq = vdso_read_begin(vdata);
-
- ts->tv_sec = vdata->xtime_coarse_sec;
- ts->tv_nsec = vdata->xtime_coarse_nsec;
-
- tomono.tv_sec = vdata->wtm_clock_sec;
- tomono.tv_nsec = vdata->wtm_clock_nsec;
-
- } while (vdso_read_retry(vdata, seq));
-
- ts->tv_sec += tomono.tv_sec;
- timespec_add_ns(ts, tomono.tv_nsec);
-
- return 0;
-}
-
-#ifdef CONFIG_ARM_ARCH_TIMER
-
-static notrace u64 get_ns(struct vdso_data *vdata)
-{
- u64 cycle_delta;
- u64 cycle_now;
- u64 nsec;
-
- cycle_now = arch_counter_get_cntvct();
-
- cycle_delta = (cycle_now - vdata->cs_cycle_last) & vdata->cs_mask;
-
- nsec = (cycle_delta * vdata->cs_mult) + vdata->xtime_clock_snsec;
- nsec >>= vdata->cs_shift;
-
- return nsec;
-}
-
-static notrace int do_realtime(struct timespec *ts, struct vdso_data *vdata)
-{
- u64 nsecs;
- u32 seq;
-
- do {
- seq = vdso_read_begin(vdata);
-
- if (!vdata->tk_is_cntvct)
- return -1;
-
- ts->tv_sec = vdata->xtime_clock_sec;
- nsecs = get_ns(vdata);
-
- } while (vdso_read_retry(vdata, seq));
-
- ts->tv_nsec = 0;
- timespec_add_ns(ts, nsecs);
-
- return 0;
-}
-
-static notrace int do_monotonic(struct timespec *ts, struct vdso_data *vdata)
-{
- struct timespec tomono;
- u64 nsecs;
- u32 seq;
-
- do {
- seq = vdso_read_begin(vdata);
-
- if (!vdata->tk_is_cntvct)
- return -1;
-
- ts->tv_sec = vdata->xtime_clock_sec;
- nsecs = get_ns(vdata);
-
- tomono.tv_sec = vdata->wtm_clock_sec;
- tomono.tv_nsec = vdata->wtm_clock_nsec;
-
- } while (vdso_read_retry(vdata, seq));
-
- ts->tv_sec += tomono.tv_sec;
- ts->tv_nsec = 0;
- timespec_add_ns(ts, nsecs + tomono.tv_nsec);
-
- return 0;
-}
-
-#else /* CONFIG_ARM_ARCH_TIMER */
-
-static notrace int do_realtime(struct timespec *ts, struct vdso_data *vdata)
-{
- return -1;
-}
-
-static notrace int do_monotonic(struct timespec *ts, struct vdso_data *vdata)
-{
- return -1;
-}
-
-#endif /* CONFIG_ARM_ARCH_TIMER */
-
-notrace int __vdso_clock_gettime(clockid_t clkid, struct timespec *ts)
-{
- struct vdso_data *vdata;
- int ret = -1;
-
- vdata = __get_datapage();
-
- switch (clkid) {
- case CLOCK_REALTIME_COARSE:
- ret = do_realtime_coarse(ts, vdata);
- break;
- case CLOCK_MONOTONIC_COARSE:
- ret = do_monotonic_coarse(ts, vdata);
- break;
- case CLOCK_REALTIME:
- ret = do_realtime(ts, vdata);
- break;
- case CLOCK_MONOTONIC:
- ret = do_monotonic(ts, vdata);
- break;
- default:
- break;
- }
-
- if (ret)
- ret = clock_gettime_fallback(clkid, ts);
-
- return ret;
-}
-
-static notrace long gettimeofday_fallback(struct timeval *_tv,
- struct timezone *_tz)
-{
- register struct timezone *tz asm("r1") = _tz;
- register struct timeval *tv asm("r0") = _tv;
- register long ret asm ("r0");
- register long nr asm("r7") = __NR_gettimeofday;
-
- asm volatile(
- " swi #0\n"
- : "=r" (ret)
- : "r" (tv), "r" (tz), "r" (nr)
- : "memory");
-
- return ret;
-}
-
-notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
-{
- struct timespec ts;
- struct vdso_data *vdata;
- int ret;
-
- vdata = __get_datapage();
-
- ret = do_realtime(&ts, vdata);
- if (ret)
- return gettimeofday_fallback(tv, tz);
-
- if (tv) {
- tv->tv_sec = ts.tv_sec;
- tv->tv_usec = ts.tv_nsec / 1000;
- }
- if (tz) {
- tz->tz_minuteswest = vdata->tz_minuteswest;
- tz->tz_dsttime = vdata->tz_dsttime;
- }
-
- return ret;
+ return __cvdso_clock_getres(clock_id, res);
}

/* Avoid unresolved references emitted by GCC */