LinuxLists.cc - RESEND and REBASE arm+arm64+aarch32 vdso rewrite

2018-10-01 17:59:28

Subject: RESEND and REBASE arm+arm64+aarch32 vdso rewrite

Last sent 23 Nov 2016.

The following 23 patches are rebased and resent, and represent a
rewrite of the arm and arm64 vDSO into C, adding support for arch32
(32-bit user space hosted 64-bit kernels) and into a common library
that other (arm, or non-arm) architectures may utilize.

[PATCH v5 01/12] arm: vdso: rename vdso_datapage variables
[PATCH v5 02/12] arm: vdso: add include file defining __get_datapage()
[PATCH v5 03/12] arm: vdso: inline assembler operations to compiler.h
[PATCH v5 04/12] arm: vdso: do calculations outside reader loops
[PATCH v6 05/12] arm: vdso: Add support for CLOCK_MONOTONIC_RAW
[PATCH v5 06/12] arm: vdso: add support for clock_getres
[PATCH v5 07/12] arm: vdso: disable profiling
[PATCH v5 08/12] arm: vdso: Add ARCH_CLOCK_FIXED_MASK
[PATCH v5 09/12] arm: vdso: move vgettimeofday.c to lib/vdso/
[PATCH v5 10/12] arm64: vdso: replace gettimeofday.S with global vgettimeofday.C
[PATCH v6 11/12] lib: vdso: Add support for CLOCK_BOOTTIME
[PATCH v5 12/12] lib: vdso: do not expose gettimeofday, if no arch supported timer
[PATCH] lib: vdso: add support for time
[PATCH v2 1/3] arm64: compat: Split the sigreturn trampolines and kuser helpers (C sources)
[PATCH v2 2/3] arm64: compat: Split the sigreturn trampolines and kuser helpers (assembler sources)
[PATCH v2 3/3] arm64: compat: Add CONFIG_KUSER_HELPERS
[PATCH] arm64: compat: Expose offset to registers in sigframes
[PATCH 1/6] arm64: compat: Use vDSO sigreturn trampolines if available
[PATCH 2/6] arm64: elf: Set AT_SYSINFO_EHDR in compat processes
[PATCH 3/6] arm64: Refactor vDSO init/setup
[PATCH v2 4/6] arm64: compat: Add a 32-bit vDSO
[PATCH 5/6] arm64: compat: 32-bit vDSO setup
[PATCH 6/6] arm64: Wire up and expose the new compat vDSO

This patch series' above has been applied to the latest Pixel phones
and resulted in a 0.4% battery improvement.

Signed-off-by: Mark Salyzyn <[email protected]>
Tested-by: Mark Salyzyn <[email protected]>
Cc: James Morse <[email protected]>
Cc: Russell King <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Dmitry Safonov <[email protected]>
Cc: John Stultz <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Laura Abbott <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Cc: Andy Gross <[email protected]>
Cc: Kevin Brodsky <[email protected]>
Cc: Andrew Pinski <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: Jeremy Linton <[email protected]>
Cc: [email protected]

Subject: RESEND [PATCH v5 06/12] arm: vdso: add support for clock_getres

2018-10-01 18:03:17

by Mark Salyzyn

[permalink] [raw]

Subject: RESEND [PATCH v5 09/12] arm: vdso: move vgettimeofday.c to lib/vdso/

Take an effort to recode the arm64 vdso code from assembler to C
previously submitted by Andrew Pinski <[email protected]>, rework
it for use in both arm and arm64, overlapping any optimizations
for each architecture. But instead of landing it in arm64, land the
result into lib/vdso and unify both implementations to simplify
future maintenance.

Declare arch/arm/vdso/vgettimeofday.c to be a candidate for a global
implementation of the vdso timer calls. The hope is that new
architectures can take advantage of the current unification of
arm and arm64 implementations.

We urge future efforts to merge their implementations into the
global vgettimeofday.c file and thus provide functional parity.

Signed-off-by: Mark Salyzyn <[email protected]>
Tested-by: Mark Salyzyn <[email protected]>
Cc: James Morse <[email protected]>
Cc: Russell King <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Dmitry Safonov <[email protected]>
Cc: John Stultz <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Laura Abbott <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Cc: Andy Gross <[email protected]>
Cc: Kevin Brodsky <[email protected]>
Cc: Andrew Pinski <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: Jeremy Linton <[email protected]>
Cc: [email protected]

v3:
- added this change
- move arch/arm/vdso/vgettimeofday.c to lib/vdso/vgettimeofday.c
- adjust vgettimeofday.c to be a better global candidate, switch to
using ARCH_PROVIDES_TIMER and __arch_counter_get() as more generic.

v4:
- update commit message to reflect overall reasoning
- adjust to reflect dropping of any forced inline

v5:
- rebase
---
arch/arm/vdso/compiler.h | 4 +
arch/arm/vdso/vgettimeofday.c | 343 +--------------------------------
lib/vdso/compiler.h | 24 +++
lib/vdso/datapage.h | 24 +++
lib/vdso/vgettimeofday.c | 344 ++++++++++++++++++++++++++++++++++
5 files changed, 397 insertions(+), 342 deletions(-)
create mode 100644 lib/vdso/compiler.h
create mode 100644 lib/vdso/datapage.h
create mode 100644 lib/vdso/vgettimeofday.c

diff --git a/arch/arm/vdso/compiler.h b/arch/arm/vdso/compiler.h
index c7751019246a..6fd88be2ff0e 100644
--- a/arch/arm/vdso/compiler.h
+++ b/arch/arm/vdso/compiler.h
@@ -34,6 +34,10 @@
#error This code depends on AEABI system call conventions
#endif

+#ifdef CONFIG_ARM_ARCH_TIMER
+#define ARCH_PROVIDES_TIMER
+#endif
+
#define DEFINE_FALLBACK(name, type_arg1, name_arg1, type_arg2, name_arg2) \
static notrace long name##_fallback(type_arg1 _##name_arg1, \
type_arg2 _##name_arg2) \
diff --git a/arch/arm/vdso/vgettimeofday.c b/arch/arm/vdso/vgettimeofday.c
index 3005479efbe8..4b241fe60d17 100644
--- a/arch/arm/vdso/vgettimeofday.c
+++ b/arch/arm/vdso/vgettimeofday.c
@@ -1,344 +1,3 @@
-/*
- * Userspace implementations of gettimeofday() and friends.
- *
- * Copyright (C) 2017 Cavium, Inc.
- * Copyright (C) 2015 Mentor Graphics Corporation
- * Copyright (C) 2012 ARM Limited
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
- *
- * 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/>.
- *
- * Author: Will Deacon <[email protected]>
- * Rewriten from arch64 version into C by: Andrew Pinski <[email protected]>
- * Reworked and rebased over arm version by: Mark Salyzyn <[email protected]>
- */
-
-#include <asm/barrier.h>
-#include <linux/compiler.h> /* for notrace */
-#include <linux/math64.h> /* for __iter_div_u64_rem() */
-#include <uapi/linux/time.h> /* for struct timespec */
-
#include "compiler.h"
#include "datapage.h"
-
-DEFINE_FALLBACK(gettimeofday, struct timeval *, tv, struct timezone *, tz)
-DEFINE_FALLBACK(clock_gettime, clockid_t, clock, struct timespec *, ts)
-DEFINE_FALLBACK(clock_getres, clockid_t, clock, struct timespec *, ts)
-
-static notrace u32 vdso_read_begin(const struct vdso_data *vd)
-{
- u32 seq;
-
- do {
- seq = READ_ONCE(vd->tb_seq_count);
-
- if ((seq & 1) == 0)
- break;
-
- cpu_relax();
- } while (true);
-
- smp_rmb(); /* Pairs with second smp_wmb in update_vsyscall */
- return seq;
-}
-
-static notrace int vdso_read_retry(const struct vdso_data *vd, u32 start)
-{
- u32 seq;
-
- smp_rmb(); /* Pairs with first smp_wmb in update_vsyscall */
- seq = READ_ONCE(vd->tb_seq_count);
- return seq != start;
-}
-
-static notrace int do_realtime_coarse(const struct vdso_data *vd,
- struct timespec *ts)
-{
- u32 seq;
-
- do {
- seq = vdso_read_begin(vd);
-
- ts->tv_sec = vd->xtime_coarse_sec;
- ts->tv_nsec = vd->xtime_coarse_nsec;
-
- } while (vdso_read_retry(vd, seq));
-
- return 0;
-}
-
-static notrace int do_monotonic_coarse(const struct vdso_data *vd,
- struct timespec *ts)
-{
- struct timespec tomono;
- u32 seq;
- u64 nsec;
-
- do {
- seq = vdso_read_begin(vd);
-
- ts->tv_sec = vd->xtime_coarse_sec;
- ts->tv_nsec = vd->xtime_coarse_nsec;
-
- tomono.tv_sec = vd->wtm_clock_sec;
- tomono.tv_nsec = vd->wtm_clock_nsec;
-
- } while (vdso_read_retry(vd, seq));
-
- ts->tv_sec += tomono.tv_sec;
- /* open coding timespec_add_ns */
- ts->tv_sec += __iter_div_u64_rem(ts->tv_nsec + tomono.tv_nsec,
- NSEC_PER_SEC, &nsec);
- ts->tv_nsec = nsec;
-
- return 0;
-}
-
-#ifdef CONFIG_ARM_ARCH_TIMER
-
-/*
- * Returns the clock delta, in nanoseconds left-shifted by the clock
- * shift.
- */
-static notrace u64 get_clock_shifted_nsec(const u64 cycle_last,
- const u32 mult,
- const u64 mask)
-{
- u64 res;
-
- /* Read the virtual counter. */
- res = arch_vdso_read_counter();
-
- res = res - cycle_last;
-
- res &= mask;
- return res * mult;
-}
-
-static notrace int do_realtime(const struct vdso_data *vd, struct timespec *ts)
-{
- u32 seq, mult, shift;
- u64 nsec, cycle_last;
-#ifdef ARCH_CLOCK_FIXED_MASK
- static const u64 mask = ARCH_CLOCK_FIXED_MASK;
-#else
- u64 mask;
-#endif
- vdso_xtime_clock_sec_t sec;
-
- do {
- seq = vdso_read_begin(vd);
-
- if (vd->use_syscall)
- return -1;
-
- cycle_last = vd->cs_cycle_last;
-
- mult = vd->cs_mono_mult;
- shift = vd->cs_shift;
-#ifndef ARCH_CLOCK_FIXED_MASK
- mask = vd->cs_mask;
-#endif
-
- sec = vd->xtime_clock_sec;
- nsec = vd->xtime_clock_snsec;
-
- } while (unlikely(vdso_read_retry(vd, seq)));
-
- nsec += get_clock_shifted_nsec(cycle_last, mult, mask);
- nsec >>= shift;
- /* open coding timespec_add_ns to save a ts->tv_nsec = 0 */
- ts->tv_sec = sec + __iter_div_u64_rem(nsec, NSEC_PER_SEC, &nsec);
- ts->tv_nsec = nsec;
-
- return 0;
-}
-
-static notrace int do_monotonic(const struct vdso_data *vd, struct timespec *ts)
-{
- u32 seq, mult, shift;
- u64 nsec, cycle_last;
-#ifdef ARCH_CLOCK_FIXED_MASK
- static const u64 mask = ARCH_CLOCK_FIXED_MASK;
-#else
- u64 mask;
-#endif
- vdso_wtm_clock_nsec_t wtm_nsec;
- __kernel_time_t sec;
-
- do {
- seq = vdso_read_begin(vd);
-
- if (vd->use_syscall)
- return -1;
-
- cycle_last = vd->cs_cycle_last;
-
- mult = vd->cs_mono_mult;
- shift = vd->cs_shift;
-#ifndef ARCH_CLOCK_FIXED_MASK
- mask = vd->cs_mask;
-#endif
-
- sec = vd->xtime_clock_sec;
- nsec = vd->xtime_clock_snsec;
-
- sec += vd->wtm_clock_sec;
- wtm_nsec = vd->wtm_clock_nsec;
-
- } while (unlikely(vdso_read_retry(vd, seq)));
-
- nsec += get_clock_shifted_nsec(cycle_last, mult, mask);
- nsec >>= shift;
- nsec += wtm_nsec;
- /* open coding timespec_add_ns to save a ts->tv_nsec = 0 */
- ts->tv_sec = sec + __iter_div_u64_rem(nsec, NSEC_PER_SEC, &nsec);
- ts->tv_nsec = nsec;
-
- return 0;
-}
-
-static notrace int do_monotonic_raw(const struct vdso_data *vd,
- struct timespec *ts)
-{
- u32 seq, mult, shift;
- u64 nsec, cycle_last;
-#ifdef ARCH_CLOCK_FIXED_MASK
- static const u64 mask = ARCH_CLOCK_FIXED_MASK;
-#else
- u64 mask;
-#endif
- vdso_raw_time_sec_t sec;
-
- do {
- seq = vdso_read_begin(vd);
-
- if (vd->use_syscall)
- return -1;
-
- cycle_last = vd->cs_cycle_last;
-
- mult = vd->cs_raw_mult;
- shift = vd->cs_shift;
-#ifndef ARCH_CLOCK_FIXED_MASK
- mask = vd->cs_mask;
-#endif
-
- sec = vd->raw_time_sec;
- nsec = vd->raw_time_nsec;
-
- } while (unlikely(vdso_read_retry(vd, seq)));
-
- nsec += get_clock_shifted_nsec(cycle_last, mult, mask);
- nsec >>= shift;
- /* open coding timespec_add_ns to save a ts->tv_nsec = 0 */
- ts->tv_sec = sec + __iter_div_u64_rem(nsec, NSEC_PER_SEC, &nsec);
- ts->tv_nsec = nsec;
-
- return 0;
-}
-
-#else /* CONFIG_ARM_ARCH_TIMER */
-
-static notrace int do_realtime(const struct vdso_data *vd, struct timespec *ts)
-{
- return -1;
-}
-
-static notrace int do_monotonic(const struct vdso_data *vd, struct timespec *ts)
-{
- return -1;
-}
-
-static notrace int do_monotonic_raw(const struct vdso_data *vd,
- struct timespec *ts)
-{
- return -1;
-}
-
-#endif /* CONFIG_ARM_ARCH_TIMER */
-
-notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
-{
- const struct vdso_data *vd = __get_datapage();
-
- switch (clock) {
- case CLOCK_REALTIME_COARSE:
- do_realtime_coarse(vd, ts);
- break;
- case CLOCK_MONOTONIC_COARSE:
- do_monotonic_coarse(vd, ts);
- break;
- case CLOCK_REALTIME:
- if (do_realtime(vd, ts))
- goto fallback;
- break;
- case CLOCK_MONOTONIC:
- if (do_monotonic(vd, ts))
- goto fallback;
- break;
- case CLOCK_MONOTONIC_RAW:
- if (do_monotonic_raw(vd, ts))
- goto fallback;
- break;
- default:
- goto fallback;
- }
-
- return 0;
-fallback:
- return clock_gettime_fallback(clock, ts);
-}
-
-notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
-{
- const struct vdso_data *vd = __get_datapage();
-
- if (likely(tv != NULL)) {
- struct timespec ts;
-
- if (do_realtime(vd, &ts))
- return gettimeofday_fallback(tv, tz);
-
- tv->tv_sec = ts.tv_sec;
- tv->tv_usec = ts.tv_nsec / 1000;
- }
-
- if (unlikely(tz != NULL)) {
- tz->tz_minuteswest = vd->tz_minuteswest;
- tz->tz_dsttime = vd->tz_dsttime;
- }
-
- return 0;
-}
-
-int __vdso_clock_getres(clockid_t clock, struct timespec *res)
-{
- long nsec;
-
- if (clock == CLOCK_REALTIME ||
- clock == CLOCK_MONOTONIC ||
- clock == CLOCK_MONOTONIC_RAW)
- nsec = MONOTONIC_RES_NSEC;
- else if (clock == CLOCK_REALTIME_COARSE ||
- clock == CLOCK_MONOTONIC_COARSE)
- nsec = LOW_RES_NSEC;
- else
- return clock_getres_fallback(clock, res);
-
- if (likely(res != NULL)) {
- res->tv_sec = 0;
- res->tv_nsec = nsec;
- }
-
- return 0;
-}
+#include "../../../lib/vdso/vgettimeofday.c"
diff --git a/lib/vdso/compiler.h b/lib/vdso/compiler.h
new file mode 100644
index 000000000000..0e618b73e064
--- /dev/null
+++ b/lib/vdso/compiler.h
@@ -0,0 +1,24 @@
+/*
+ * Userspace implementations of fallback calls
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * 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/>.
+ */
+
+#ifndef __VDSO_COMPILER_H
+#define __VDSO_COMPILER_H
+
+#error "vdso: Provide architectural overrides such as ARCH_PROVIDES_TIMER,"
+#error " DEFINE_FALLBACK and __arch_counter_get or any overrides. eg:"
+#error " vdso entry points or compilation time helpers."
+
+#endif /* __VDSO_COMPILER_H */
diff --git a/lib/vdso/datapage.h b/lib/vdso/datapage.h
new file mode 100644
index 000000000000..df4427e42d51
--- /dev/null
+++ b/lib/vdso/datapage.h
@@ -0,0 +1,24 @@
+/*
+ * Userspace implementations of __get_datapage
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * 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/>.
+ */
+
+#ifndef __VDSO_DATAPAGE_H
+#define __VDSO_DATAPAGE_H
+
+#error "vdso: Provide a user space architecture specific definition or"
+#error "prototype for struct vdso_data *__get_datapage(void). Also define"
+#error "ARCH_CLOCK_FIXED_MASK if not provided by cs_mask."
+
+#endif /* __VDSO_DATAPAGE_H */
diff --git a/lib/vdso/vgettimeofday.c b/lib/vdso/vgettimeofday.c
new file mode 100644
index 000000000000..33c5917fe9f8
--- /dev/null
+++ b/lib/vdso/vgettimeofday.c
@@ -0,0 +1,344 @@
+/*
+ * Userspace implementations of gettimeofday() and friends.
+ *
+ * Copyright (C) 2017 Cavium, Inc.
+ * Copyright (C) 2015 Mentor Graphics Corporation
+ * Copyright (C) 2012 ARM Limited
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * 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/>.
+ *
+ * Author: Will Deacon <[email protected]>
+ * Rewriten from arch64 version into C by: Andrew Pinski <[email protected]>
+ * Reworked and rebased over arm version by: Mark Salyzyn <[email protected]>
+ */
+
+#include <asm/barrier.h>
+#include <linux/compiler.h> /* for notrace */
+#include <linux/math64.h> /* for __iter_div_u64_rem() */
+#include <uapi/linux/time.h> /* for struct timespec */
+
+#include "compiler.h"
+#include "datapage.h"
+
+DEFINE_FALLBACK(gettimeofday, struct timeval *, tv, struct timezone *, tz)
+DEFINE_FALLBACK(clock_gettime, clockid_t, clock, struct timespec *, ts)
+DEFINE_FALLBACK(clock_getres, clockid_t, clock, struct timespec *, ts)
+
+static notrace u32 vdso_read_begin(const struct vdso_data *vd)
+{
+ u32 seq;
+
+ do {
+ seq = READ_ONCE(vd->tb_seq_count);
+
+ if ((seq & 1) == 0)
+ break;
+
+ cpu_relax();
+ } while (true);
+
+ smp_rmb(); /* Pairs with second smp_wmb in update_vsyscall */
+ return seq;
+}
+
+static notrace int vdso_read_retry(const struct vdso_data *vd, u32 start)
+{
+ u32 seq;
+
+ smp_rmb(); /* Pairs with first smp_wmb in update_vsyscall */
+ seq = READ_ONCE(vd->tb_seq_count);
+ return seq != start;
+}
+
+static notrace int do_realtime_coarse(const struct vdso_data *vd,
+ struct timespec *ts)
+{
+ u32 seq;
+
+ do {
+ seq = vdso_read_begin(vd);
+
+ ts->tv_sec = vd->xtime_coarse_sec;
+ ts->tv_nsec = vd->xtime_coarse_nsec;
+
+ } while (vdso_read_retry(vd, seq));
+
+ return 0;
+}
+
+static notrace int do_monotonic_coarse(const struct vdso_data *vd,
+ struct timespec *ts)
+{
+ struct timespec tomono;
+ u32 seq;
+ u64 nsec;
+
+ do {
+ seq = vdso_read_begin(vd);
+
+ ts->tv_sec = vd->xtime_coarse_sec;
+ ts->tv_nsec = vd->xtime_coarse_nsec;
+
+ tomono.tv_sec = vd->wtm_clock_sec;
+ tomono.tv_nsec = vd->wtm_clock_nsec;
+
+ } while (vdso_read_retry(vd, seq));
+
+ ts->tv_sec += tomono.tv_sec;
+ /* open coding timespec_add_ns */
+ ts->tv_sec += __iter_div_u64_rem(ts->tv_nsec + tomono.tv_nsec,
+ NSEC_PER_SEC, &nsec);
+ ts->tv_nsec = nsec;
+
+ return 0;
+}
+
+#ifdef ARCH_PROVIDES_TIMER
+
+/*
+ * Returns the clock delta, in nanoseconds left-shifted by the clock
+ * shift.
+ */
+static notrace u64 get_clock_shifted_nsec(const u64 cycle_last,
+ const u32 mult,
+ const u64 mask)
+{
+ u64 res;
+
+ /* Read the virtual counter. */
+ res = arch_vdso_read_counter();
+
+ res = res - cycle_last;
+
+ res &= mask;
+ return res * mult;
+}
+
+static notrace int do_realtime(const struct vdso_data *vd, struct timespec *ts)
+{
+ u32 seq, mult, shift;
+ u64 nsec, cycle_last;
+#ifdef ARCH_CLOCK_FIXED_MASK
+ static const u64 mask = ARCH_CLOCK_FIXED_MASK;
+#else
+ u64 mask;
+#endif
+ vdso_xtime_clock_sec_t sec;
+
+ do {
+ seq = vdso_read_begin(vd);
+
+ if (vd->use_syscall)
+ return -1;
+
+ cycle_last = vd->cs_cycle_last;
+
+ mult = vd->cs_mono_mult;
+ shift = vd->cs_shift;
+#ifndef ARCH_CLOCK_FIXED_MASK
+ mask = vd->cs_mask;
+#endif
+
+ sec = vd->xtime_clock_sec;
+ nsec = vd->xtime_clock_snsec;
+
+ } while (unlikely(vdso_read_retry(vd, seq)));
+
+ nsec += get_clock_shifted_nsec(cycle_last, mult, mask);
+ nsec >>= shift;
+ /* open coding timespec_add_ns to save a ts->tv_nsec = 0 */
+ ts->tv_sec = sec + __iter_div_u64_rem(nsec, NSEC_PER_SEC, &nsec);
+ ts->tv_nsec = nsec;
+
+ return 0;
+}
+
+static notrace int do_monotonic(const struct vdso_data *vd, struct timespec *ts)
+{
+ u32 seq, mult, shift;
+ u64 nsec, cycle_last;
+#ifdef ARCH_CLOCK_FIXED_MASK
+ static const u64 mask = ARCH_CLOCK_FIXED_MASK;
+#else
+ u64 mask;
+#endif
+ vdso_wtm_clock_nsec_t wtm_nsec;
+ __kernel_time_t sec;
+
+ do {
+ seq = vdso_read_begin(vd);
+
+ if (vd->use_syscall)
+ return -1;
+
+ cycle_last = vd->cs_cycle_last;
+
+ mult = vd->cs_mono_mult;
+ shift = vd->cs_shift;
+#ifndef ARCH_CLOCK_FIXED_MASK
+ mask = vd->cs_mask;
+#endif
+
+ sec = vd->xtime_clock_sec;
+ nsec = vd->xtime_clock_snsec;
+
+ sec += vd->wtm_clock_sec;
+ wtm_nsec = vd->wtm_clock_nsec;
+
+ } while (unlikely(vdso_read_retry(vd, seq)));
+
+ nsec += get_clock_shifted_nsec(cycle_last, mult, mask);
+ nsec >>= shift;
+ nsec += wtm_nsec;
+ /* open coding timespec_add_ns to save a ts->tv_nsec = 0 */
+ ts->tv_sec = sec + __iter_div_u64_rem(nsec, NSEC_PER_SEC, &nsec);
+ ts->tv_nsec = nsec;
+
+ return 0;
+}
+
+static notrace int do_monotonic_raw(const struct vdso_data *vd,
+ struct timespec *ts)
+{
+ u32 seq, mult, shift;
+ u64 nsec, cycle_last;
+#ifdef ARCH_CLOCK_FIXED_MASK
+ static const u64 mask = ARCH_CLOCK_FIXED_MASK;
+#else
+ u64 mask;
+#endif
+ vdso_raw_time_sec_t sec;
+
+ do {
+ seq = vdso_read_begin(vd);
+
+ if (vd->use_syscall)
+ return -1;
+
+ cycle_last = vd->cs_cycle_last;
+
+ mult = vd->cs_raw_mult;
+ shift = vd->cs_shift;
+#ifndef ARCH_CLOCK_FIXED_MASK
+ mask = vd->cs_mask;
+#endif
+
+ sec = vd->raw_time_sec;
+ nsec = vd->raw_time_nsec;
+
+ } while (unlikely(vdso_read_retry(vd, seq)));
+
+ nsec += get_clock_shifted_nsec(cycle_last, mult, mask);
+ nsec >>= shift;
+ /* open coding timespec_add_ns to save a ts->tv_nsec = 0 */
+ ts->tv_sec = sec + __iter_div_u64_rem(nsec, NSEC_PER_SEC, &nsec);
+ ts->tv_nsec = nsec;
+
+ return 0;
+}
+
+#else /* ARCH_PROVIDES_TIMER */
+
+static notrace int do_realtime(const struct vdso_data *vd, struct timespec *ts)
+{
+ return -1;
+}
+
+static notrace int do_monotonic(const struct vdso_data *vd, struct timespec *ts)
+{
+ return -1;
+}
+
+static notrace int do_monotonic_raw(const struct vdso_data *vd,
+ struct timespec *ts)
+{
+ return -1;
+}
+
+#endif /* ARCH_PROVIDES_TIMER */
+
+notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
+{
+ const struct vdso_data *vd = __get_datapage();
+
+ switch (clock) {
+ case CLOCK_REALTIME_COARSE:
+ do_realtime_coarse(vd, ts);
+ break;
+ case CLOCK_MONOTONIC_COARSE:
+ do_monotonic_coarse(vd, ts);
+ break;
+ case CLOCK_REALTIME:
+ if (do_realtime(vd, ts))
+ goto fallback;
+ break;
+ case CLOCK_MONOTONIC:
+ if (do_monotonic(vd, ts))
+ goto fallback;
+ break;
+ case CLOCK_MONOTONIC_RAW:
+ if (do_monotonic_raw(vd, ts))
+ goto fallback;
+ break;
+ default:
+ goto fallback;
+ }
+
+ return 0;
+fallback:
+ return clock_gettime_fallback(clock, ts);
+}
+
+notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
+{
+ const struct vdso_data *vd = __get_datapage();
+
+ if (likely(tv != NULL)) {
+ struct timespec ts;
+
+ if (do_realtime(vd, &ts))
+ return gettimeofday_fallback(tv, tz);
+
+ tv->tv_sec = ts.tv_sec;
+ tv->tv_usec = ts.tv_nsec / 1000;
+ }
+
+ if (unlikely(tz != NULL)) {
+ tz->tz_minuteswest = vd->tz_minuteswest;
+ tz->tz_dsttime = vd->tz_dsttime;
+ }
+
+ return 0;
+}
+
+int __vdso_clock_getres(clockid_t clock, struct timespec *res)
+{
+ long nsec;
+
+ if (clock == CLOCK_REALTIME ||
+ clock == CLOCK_MONOTONIC ||
+ clock == CLOCK_MONOTONIC_RAW)
+ nsec = MONOTONIC_RES_NSEC;
+ else if (clock == CLOCK_REALTIME_COARSE ||
+ clock == CLOCK_MONOTONIC_COARSE)
+ nsec = LOW_RES_NSEC;
+ else
+ return clock_getres_fallback(clock, res);
+
+ if (likely(res != NULL)) {
+ res->tv_sec = 0;
+ res->tv_nsec = nsec;
+ }
+
+ return 0;
+}
--
2.19.0.605.g01d371f741-goog

2018-10-01 18:03:25

by Mark Salyzyn

[permalink] [raw]

2018-10-01 18:04:48

by Mark Salyzyn

[permalink] [raw]

Subject: RESEND [PATCH] arm64: compat: Expose offset to registers in sigframes

From: Kevin Brodsky <[email protected]>

This will be needed to provide unwinding information in compat
sigreturn trampolines, part of the future compat vDSO. There is no
obvious header the compat_sig* struct's should be moved to, so let's
put them in signal32.h.

Also fix minor style issues reported by checkpatch.

Signed-off-by: Kevin Brodsky <[email protected]>
Signed-off-by: Mark Salyzyn <[email protected]>
Tested-by: Mark Salyzyn <[email protected]>
Cc: James Morse <[email protected]>
Cc: Russell King <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Dmitry Safonov <[email protected]>
Cc: John Stultz <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Laura Abbott <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Cc: Andy Gross <[email protected]>
Cc: Kevin Brodsky <[email protected]>
Cc: Andrew Pinski <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: Dave Martin <[email protected]>
Cc: Eric W. Biederman <[email protected]>
Cc: Jeremy Linton <[email protected]>
Cc: [email protected]

NB:
Basically unchanged as part of a vDSO32 effort through 4 revisions,
Resubmitted as a standalone change for quicker approval.
---
arch/arm64/include/asm/signal32.h | 46 +++++++++++++++++++++++++++++++
arch/arm64/kernel/asm-offsets.c | 13 +++++++++
arch/arm64/kernel/signal32.c | 46 -------------------------------
3 files changed, 59 insertions(+), 46 deletions(-)

diff --git a/arch/arm64/include/asm/signal32.h b/arch/arm64/include/asm/signal32.h
index 58e288aaf0ba..bcd0e139ee4a 100644
--- a/arch/arm64/include/asm/signal32.h
+++ b/arch/arm64/include/asm/signal32.h
@@ -20,6 +20,52 @@
#ifdef CONFIG_COMPAT
#include <linux/compat.h>

+struct compat_sigcontext {
+ /* We always set these two fields to 0 */
+ compat_ulong_t trap_no;
+ compat_ulong_t error_code;
+
+ compat_ulong_t oldmask;
+ compat_ulong_t arm_r0;
+ compat_ulong_t arm_r1;
+ compat_ulong_t arm_r2;
+ compat_ulong_t arm_r3;
+ compat_ulong_t arm_r4;
+ compat_ulong_t arm_r5;
+ compat_ulong_t arm_r6;
+ compat_ulong_t arm_r7;
+ compat_ulong_t arm_r8;
+ compat_ulong_t arm_r9;
+ compat_ulong_t arm_r10;
+ compat_ulong_t arm_fp;
+ compat_ulong_t arm_ip;
+ compat_ulong_t arm_sp;
+ compat_ulong_t arm_lr;
+ compat_ulong_t arm_pc;
+ compat_ulong_t arm_cpsr;
+ compat_ulong_t fault_address;
+};
+
+struct compat_ucontext {
+ compat_ulong_t uc_flags;
+ compat_uptr_t uc_link;
+ compat_stack_t uc_stack;
+ struct compat_sigcontext uc_mcontext;
+ compat_sigset_t uc_sigmask;
+ int __unused[32 - (sizeof(compat_sigset_t) / sizeof(int))];
+ compat_ulong_t uc_regspace[128] __aligned(8);
+};
+
+struct compat_sigframe {
+ struct compat_ucontext uc;
+ compat_ulong_t retcode[2];
+};
+
+struct compat_rt_sigframe {
+ struct compat_siginfo info;
+ struct compat_sigframe sig;
+};
+
int compat_setup_frame(int usig, struct ksignal *ksig, sigset_t *set,
struct pt_regs *regs);
int compat_setup_rt_frame(int usig, struct ksignal *ksig, sigset_t *set,
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index 8938a4223690..a79507c5d845 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -29,6 +29,7 @@
#include <asm/fixmap.h>
#include <asm/thread_info.h>
#include <asm/memory.h>
+#include <asm/signal32.h>
#include <asm/smp_plat.h>
#include <asm/suspend.h>
#include <asm/vdso_datapage.h>
@@ -81,6 +82,18 @@ int main(void)
DEFINE(S_STACKFRAME, offsetof(struct pt_regs, stackframe));
DEFINE(S_FRAME_SIZE, sizeof(struct pt_regs));
BLANK();
+#ifdef CONFIG_COMPAT
+ DEFINE(COMPAT_SIGFRAME_REGS_OFFSET,
+ offsetof(struct compat_sigframe, uc) +
+ offsetof(struct compat_ucontext, uc_mcontext) +
+ offsetof(struct compat_sigcontext, arm_r0));
+ DEFINE(COMPAT_RT_SIGFRAME_REGS_OFFSET,
+ offsetof(struct compat_rt_sigframe, sig) +
+ offsetof(struct compat_sigframe, uc) +
+ offsetof(struct compat_ucontext, uc_mcontext) +
+ offsetof(struct compat_sigcontext, arm_r0));
+ BLANK();
+#endif
DEFINE(MM_CONTEXT_ID, offsetof(struct mm_struct, context.id.counter));
BLANK();
DEFINE(VMA_VM_MM, offsetof(struct vm_area_struct, vm_mm));
diff --git a/arch/arm64/kernel/signal32.c b/arch/arm64/kernel/signal32.c
index 52f0d44417c8..6b421666b5b8 100644
--- a/arch/arm64/kernel/signal32.c
+++ b/arch/arm64/kernel/signal32.c
@@ -30,42 +30,6 @@
#include <linux/uaccess.h>
#include <asm/unistd.h>

-struct compat_sigcontext {
- /* We always set these two fields to 0 */
- compat_ulong_t trap_no;
- compat_ulong_t error_code;
-
- compat_ulong_t oldmask;
- compat_ulong_t arm_r0;
- compat_ulong_t arm_r1;
- compat_ulong_t arm_r2;
- compat_ulong_t arm_r3;
- compat_ulong_t arm_r4;
- compat_ulong_t arm_r5;
- compat_ulong_t arm_r6;
- compat_ulong_t arm_r7;
- compat_ulong_t arm_r8;
- compat_ulong_t arm_r9;
- compat_ulong_t arm_r10;
- compat_ulong_t arm_fp;
- compat_ulong_t arm_ip;
- compat_ulong_t arm_sp;
- compat_ulong_t arm_lr;
- compat_ulong_t arm_pc;
- compat_ulong_t arm_cpsr;
- compat_ulong_t fault_address;
-};
-
-struct compat_ucontext {
- compat_ulong_t uc_flags;
- compat_uptr_t uc_link;
- compat_stack_t uc_stack;
- struct compat_sigcontext uc_mcontext;
- compat_sigset_t uc_sigmask;
- int __unused[32 - (sizeof (compat_sigset_t) / sizeof (int))];
- compat_ulong_t uc_regspace[128] __attribute__((__aligned__(8)));
-};
-
struct compat_vfp_sigframe {
compat_ulong_t magic;
compat_ulong_t size;
@@ -92,16 +56,6 @@ struct compat_aux_sigframe {
unsigned long end_magic;
} __attribute__((__aligned__(8)));

-struct compat_sigframe {
- struct compat_ucontext uc;
- compat_ulong_t retcode[2];
-};
-
-struct compat_rt_sigframe {
- struct compat_siginfo info;
- struct compat_sigframe sig;
-};
-
#define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))

static inline int put_sigset_t(compat_sigset_t __user *uset, sigset_t *set)
--
2.19.0.605.g01d371f741-goog

2018-10-01 18:04:55

by Mark Salyzyn

[permalink] [raw]

Subject: RESEND [PATCH 1/6] arm64: compat: Use vDSO sigreturn trampolines if available

From: Kevin Brodsky <[email protected]>

If the compat vDSO is enabled, it replaces the sigreturn page.
Therefore, we use the sigreturn trampolines the vDSO provides instead.

Signed-off-by: Kevin Brodsky <[email protected]>
Signed-off-by: Mark Salyzyn <[email protected]>
Tested-by: Mark Salyzyn <[email protected]>
Cc: James Morse <[email protected]>
Cc: Russell King <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Dmitry Safonov <[email protected]>
Cc: John Stultz <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Laura Abbott <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Cc: Andy Gross <[email protected]>
Cc: Andrew Pinski <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: Jeremy Linton <[email protected]>
Cc: [email protected]
---
arch/arm64/include/asm/vdso.h | 3 +++
arch/arm64/kernel/signal32.c | 15 +++++++++++++++
2 files changed, 18 insertions(+)

diff --git a/arch/arm64/include/asm/vdso.h b/arch/arm64/include/asm/vdso.h
index 839ce0031bd5..f2a952338f1e 100644
--- a/arch/arm64/include/asm/vdso.h
+++ b/arch/arm64/include/asm/vdso.h
@@ -28,6 +28,9 @@
#ifndef __ASSEMBLY__

#include <generated/vdso-offsets.h>
+#ifdef CONFIG_VDSO32
+#include <generated/vdso32-offsets.h>
+#endif

#define VDSO_SYMBOL(base, name) \
({ \
diff --git a/arch/arm64/kernel/signal32.c b/arch/arm64/kernel/signal32.c
index 6b421666b5b8..c3d9a74e3945 100644
--- a/arch/arm64/kernel/signal32.c
+++ b/arch/arm64/kernel/signal32.c
@@ -29,6 +29,7 @@
#include <asm/traps.h>
#include <linux/uaccess.h>
#include <asm/unistd.h>
+#include <asm/vdso.h>

struct compat_vfp_sigframe {
compat_ulong_t magic;
@@ -352,6 +353,19 @@ static void compat_setup_return(struct pt_regs *regs, struct k_sigaction *ka,
retcode = ptr_to_compat(ka->sa.sa_restorer);
} else {
/* Set up sigreturn pointer */
+#ifdef CONFIG_VDSO32
+ void *vdso_base = current->mm->context.vdso;
+ void *trampoline =
+ (ka->sa.sa_flags & SA_SIGINFO
+ ? (thumb
+ ? VDSO_SYMBOL(vdso_base, compat_rt_sigreturn_thumb)
+ : VDSO_SYMBOL(vdso_base, compat_rt_sigreturn_arm))
+ : (thumb
+ ? VDSO_SYMBOL(vdso_base, compat_sigreturn_thumb)
+ : VDSO_SYMBOL(vdso_base, compat_sigreturn_arm)));
+
+ retcode = ptr_to_compat(trampoline) + thumb;
+#else
void *sigreturn_base = current->mm->context.vdso;
unsigned int idx = thumb << 1;

@@ -359,6 +373,7 @@ static void compat_setup_return(struct pt_regs *regs, struct k_sigaction *ka,
idx += 3;

retcode = ptr_to_compat(sigreturn_base) + (idx << 2) + thumb;
+#endif
}

regs->regs[0] = usig;
--
2.19.0.605.g01d371f741-goog

2018-10-01 18:04:56

by Mark Salyzyn

[permalink] [raw]

On 10/02/2018 01:50 AM, Russell King - ARM Linux wrote:
> On Mon, Oct 01, 2018 at 01:44:52PM -0700, Mark Salyzyn wrote:
>> Despite the gain of 0.4% for screen-on battery life, where Android has a mix
>> of 64 and 32 bit applications, thus still relevant _today_ on 64 bit
>> architectures (providing vDSO32 for 32-bit applications).
> I don't think the issue is what you think it is. 0.4% gain is
> equivalent to almost (but not quite) 1 minute extra for a lifetime of
> 4 hours. Is that really noticable, and is it worth the churn from
> merging this series?

Screen on battery life, all other components of the system active,
backlights, touchscreen, sensors etc and it still had a measurable
impact on power from the portion that came from the CPU complex. This
impact came solely from 32 bit applications left over on the 64-bit
platforms that did not formerly have vDSO support. 32-bit applications
are not going away even with the advent of 64-bit (sound media framework
on Android is 32-bit).

Reduction in power is also an increase in performance. The
microbenchmarks show ~3-10 fold improvement in the actions of acquiring
the time of various sorts for 32-bit applications on 64-bit. A savings
in the range of sub-microseconds each time(sic) adds up to 0.4% battery
improvement overall.
> Given that the gain is so marginal, I can see why people find it
> difficult to get excited about this series to spend the time reviewing
> it.
The reviews were intense over the years IMHO, appeasing several
stakeholders and testers. Its that final ACK that has been elusive. I
have gotten private emails from ARM many times promising some
engineering to look at these waiting patiently without feedback.

The changes, as requested in the reviews of the past, turned also into
moving most vdso maintenance for all architectures of ARM into lib/vdso
with no reduction in microbenchmark performance for the other
configurations, at least two additional non-arm architectures look like
they could readily switch over to using it as well. This is a major win
for maintenance (and was not part of the original set).

As a result switching 64-ARM vdso assembler to C is a win for
maintenance if upstream'd.

Given the Android will need to place these patches in their common tree
(not there yet because I have required upstream first, but with limits,
2 years seems a bit long to wait for a project started in ARM, then I
was asked to help push it forward), not having them upstream, tested,
with many eyes on the code, will be a pity and will result in a possible
maintenance burden on up to 13000 phone devices.

-- Mark

2018-10-02 15:11:15

by Mark Salyzyn

[permalink] [raw]

Subject: Re: RESEND and REBASE arm+arm64+aarch32 vdso rewrite

On 10/02/2018 03:00 AM, Catalin Marinas wrote:
> On Mon, Oct 01, 2018 at 01:44:52PM -0700, Mark Salyzyn wrote:
>> On 10/01/2018 11:49 AM, John Stultz wrote:
>>> On Mon, Oct 1, 2018 at 10:58 AM, Mark Salyzyn <[email protected]> wrote:
>>>> Last sent 23 Nov 2016.
>>>>
>>>> The following 23 patches are rebased and resent, and represent a
>>>> rewrite of the arm and arm64 vDSO into C, adding support for arch32
>>>> (32-bit user space hosted 64-bit kernels) and into a common library
>>>> that other (arm, or non-arm) architectures may utilize.
>>> So I feel like this has gone around a few times w/o much comment from
>>> the arm/arm64 maintainers. I'm not sure if there's a reason?
>> I am "forming an opinion"(tm) that ARM is not interested in any work on 32
>> bit arm architectures. They have no manpower that they are willing to devote
>> to this.
> Actually, we are interested in this work but, TBH, I find it a bit hard
> to read your series and have postponed looking into it in detail. Just
> look at the patch numbering/versioning for example:
>
>> [PATCH v5 01/12] arm: vdso: rename vdso_datapage variables
>> [PATCH v5 02/12] arm: vdso: add include file defining __get_datapage()
>> [PATCH v5 03/12] arm: vdso: inline assembler operations to compiler.h
>> [PATCH v5 04/12] arm: vdso: do calculations outside reader loops
>> [PATCH v6 05/12] arm: vdso: Add support for CLOCK_MONOTONIC_RAW
>> [PATCH v5 06/12] arm: vdso: add support for clock_getres
>> [PATCH v5 07/12] arm: vdso: disable profiling
>> [PATCH v5 08/12] arm: vdso: Add ARCH_CLOCK_FIXED_MASK
>> [PATCH v5 09/12] arm: vdso: move vgettimeofday.c to lib/vdso/
>> [PATCH v5 10/12] arm64: vdso: replace gettimeofday.S with global vgettimeofday.C
>> [PATCH v6 11/12] lib: vdso: Add support for CLOCK_BOOTTIME
>> [PATCH v5 12/12] lib: vdso: do not expose gettimeofday, if no arch supported timer
>> [PATCH] lib: vdso: add support for time
>> [PATCH v2 1/3] arm64: compat: Split the sigreturn trampolines and kuser helpers (C sources)
>> [PATCH v2 2/3] arm64: compat: Split the sigreturn trampolines and kuser helpers (assembler sources)
>> [PATCH v2 3/3] arm64: compat: Add CONFIG_KUSER_HELPERS
>> [PATCH] arm64: compat: Expose offset to registers in sigframes
>> [PATCH 1/6] arm64: compat: Use vDSO sigreturn trampolines if available
>> [PATCH 2/6] arm64: elf: Set AT_SYSINFO_EHDR in compat processes
>> [PATCH 3/6] arm64: Refactor vDSO init/setup
>> [PATCH v2 4/6] arm64: compat: Add a 32-bit vDSO
>> [PATCH 5/6] arm64: compat: 32-bit vDSO setup
>> [PATCH 6/6] arm64: Wire up and expose the new compat vDSO
> The above may look obvious to you as you've worked on it but not to
> maintainers who have to read lots of other patchsets.
Because the whole set was not taken, I split them into mostly orthogonal
pieces for divide and conquer as requested. I feel so betrayed by the
system ;-} :-)

There is an order, but you will find at least

[PATCH v2 1/3] arm64: compat: Split the sigreturn trampolines and kuser helpers (C sources)
[PATCH v2 2/3] arm64: compat: Split the sigreturn trampolines and kuser helpers (assembler sources)
[PATCH v2 3/3] arm64: compat: Add CONFIG_KUSER_HELPERS

can go independently at first and standalone providing a much needed rework and added security by allowing control over the troublesome kuser helpers.

>> Despite the gain of 0.4% for screen-on battery life, where Android has a mix
>> of 64 and 32 bit applications, thus still relevant _today_ on 64 bit
>> architectures (providing vDSO32 for 32-bit applications).
> As Russell said, if that's the only gain, you may need other selling
> points.
0.4% screen on means all other components on the phone including the
backlight taking power, and _still_ had a measurable power impact adding
arm64 vDSO32 (32 arm) applications that are a subset of the phone
ecosystem. There are 64-bit phones that have only a 32-bit user space
that no doubt will take plenty more from this.

Microbenchmarks for arm32 application on arm64 report ~3-10 fold
improvement in performance (time() call being the ten fold improvement,
a gain for both arm32 and arm64 applications)
> The main advantage I see is to avoid code duplication, hence a vdso
> library that could be shared by arm/arm64/arm64-compat _and_ future or
> existing architectures that need vdso support.

Thankfully added after being reviewed, but alas increased the complexity
of the set to fulfill.
>> ARM has complained that they want them all at one time because individually
>> they represent more work. So the whole set is here ready to go.
> Having five separate series without a clear dependency between them was
> worse than the current numbering scheme ;).

For that I apologize, I allowed others to ask it to be split up and
complied.
> Anyway, since I still think this series is important, some weeks ago I
> assigned Vincenzo Frascino in my team the task of de-cluttering this
> patchset and posting it to the list. So we may see a new series later
> this month (and any feedback welcome).

WooHoo (sorry for being so emotional)

-- Mark