RESEND [PATCH v5 03/12] arm: vdso: inline assembler operations to compiler.h

[Mark Salyzyn]

Take an effort to recode the arm64 vdso code from assembler to C
previously submitted by Andrew Pinski <apinski@xxxxxxxxxx>, 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.

Move compiler-specific code to a local compiler.h file:

- CONFIG_AEABI dependency check.
- System call fallback functions standardized into a
  DEFINE_FALLBACK macro.
- Replace arch_counter_get_cntvct() with arch_vdso_read_counter.
- Deal with architecture specific unresolved references emitted
  by GCC.
- Optimize handling of fallback calls in callers.
- For time functions that always return success, do not waste time
  checking return value for switch to fallback.
- Optimize unlikely nullptr checking in __vdso_gettimeofday,
  if tv null no need to proceed to fallback, as vdso is still
  capable of filling in the tv values.

Signed-off-by: Mark Salyzyn <salyzyn@xxxxxxxxxxx>
Cc: James Morse <james.morse@xxxxxxx>
Cc: Russell King <linux@xxxxxxxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Dmitry Safonov <dsafonov@xxxxxxxxxxxxx>
Cc: John Stultz <john.stultz@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Laura Abbott <labbott@xxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Cc: Andy Gross <andy.gross@xxxxxxxxxx>
Cc: Kevin Brodsky <kevin.brodsky@xxxxxxx>
Cc: Andrew Pinski <apinski@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: Jeremy Linton <Jeremy.Linton@xxxxxxx>

v2:
- split first CL into 3 of 7 pieces

v4:
- switch to arch_vdso_read_counter as common API
- update commit message to reflect overall reasoning

v5:
- comment about asm/arch_timer.h and asm/processor.h regarding why
  they have been added in compiler.h for porting clarity.
- add linux/compiler.h in vgettimeofday.c because of notrace.
- remove unnecessary dependency on linux/hrtimer.h
---
 arch/arm/vdso/compiler.h      |  69 +++++++++++++++++++++
 arch/arm/vdso/vgettimeofday.c | 109 +++++++++-------------------------
 2 files changed, 96 insertions(+), 82 deletions(-)
 create mode 100644 arch/arm/vdso/compiler.h

diff --git a/arch/arm/vdso/compiler.h b/arch/arm/vdso/compiler.h
new file mode 100644
index 000000000000..af24502797e8
--- /dev/null
+++ b/arch/arm/vdso/compiler.h
@@ -0,0 +1,69 @@
+/*
+ * Userspace implementations of fallback calls
+ *
+ * Copyright (C) 2017 Cavium, Inc.
+ * 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 <will.deacon@xxxxxxx>
+ * Rewriten into C by: Andrew Pinski <apinski@xxxxxxxxxx>
+ */
+
+#ifndef __VDSO_COMPILER_H
+#define __VDSO_COMPILER_H
+
+#include <asm/arch_timer.h>	/* for arch_counter_get_cntvct()	*/
+#include <asm/processor.h>	/* for cpu_relax()			*/
+#include <asm/unistd.h>
+#include <linux/compiler.h>
+
+#ifndef CONFIG_AEABI
+#error This code depends on AEABI system call conventions
+#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)		  \
+{									  \
+	register type_arg1 name_arg1 asm("r0") = _##name_arg1;		  \
+	register type_arg2 name_arg2 asm("r1") = _##name_arg2;		  \
+	register long ret asm ("r0");					  \
+	register long nr asm("r7") = __NR_##name;			  \
+									  \
+	asm volatile(							  \
+	"	swi #0\n"						  \
+	: "=r" (ret)							  \
+	: "r" (name_arg1), "r" (name_arg2), "r" (nr)			  \
+	: "memory");							  \
+									  \
+	return ret;							  \
+}
+
+#define arch_vdso_read_counter() arch_counter_get_cntvct()
+
+/* Avoid unresolved references emitted by GCC */
+
+void __aeabi_unwind_cpp_pr0(void)
+{
+}
+
+void __aeabi_unwind_cpp_pr1(void)
+{
+}
+
+void __aeabi_unwind_cpp_pr2(void)
+{
+}
+
+#endif /* __VDSO_COMPILER_H */
diff --git a/arch/arm/vdso/vgettimeofday.c b/arch/arm/vdso/vgettimeofday.c
index 2474c17dc356..522094b147a2 100644
--- a/arch/arm/vdso/vgettimeofday.c
+++ b/arch/arm/vdso/vgettimeofday.c
@@ -22,21 +22,16 @@
  * Reworked and rebased over arm version by: Mark Salyzyn <salyzyn@xxxxxxxxxxx>
  */
 
-#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>
-
-#ifndef CONFIG_AEABI
-#error This code depends on AEABI system call conventions
-#endif
+#include <linux/compiler.h>	/* for notrace				*/
+#include <linux/time.h>
 
+#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)
+
 static notrace u32 vdso_read_begin(const struct vdso_data *vd)
 {
 	u32 seq;
@@ -63,23 +58,6 @@ static notrace int vdso_read_retry(const struct vdso_data *vd, u32 start)
 	return seq != 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(const struct vdso_data *vd,
 				      struct timespec *ts)
 {
@@ -127,7 +105,7 @@ static notrace u64 get_ns(const struct vdso_data *vd)
 	u64 cycle_now;
 	u64 nsec;
 
-	cycle_now = arch_counter_get_cntvct();
+	cycle_now = arch_vdso_read_counter();
 
 	cycle_delta = (cycle_now - vd->cs_cycle_last) & vd->cs_mask;
 
@@ -200,85 +178,52 @@ static notrace int do_monotonic(const struct vdso_data *vd, struct timespec *ts)
 
 #endif /* CONFIG_ARM_ARCH_TIMER */
 
-notrace int __vdso_clock_gettime(clockid_t clkid, struct timespec *ts)
+notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
 {
-	int ret = -1;
-
 	const struct vdso_data *vd = __get_datapage();
 
-	switch (clkid) {
+	switch (clock) {
 	case CLOCK_REALTIME_COARSE:
-		ret = do_realtime_coarse(vd, ts);
+		do_realtime_coarse(vd, ts);
 		break;
 	case CLOCK_MONOTONIC_COARSE:
-		ret = do_monotonic_coarse(vd, ts);
+		do_monotonic_coarse(vd, ts);
 		break;
 	case CLOCK_REALTIME:
-		ret = do_realtime(vd, ts);
+		if (do_realtime(vd, ts))
+			goto fallback;
 		break;
 	case CLOCK_MONOTONIC:
-		ret = do_monotonic(vd, ts);
+		if (do_monotonic(vd, ts))
+			goto fallback;
 		break;
 	default:
-		break;
+		goto fallback;
 	}
 
-	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;
+	return 0;
+fallback:
+	return clock_gettime_fallback(clock, ts);
 }
 
 notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
 {
-	struct timespec ts;
-	int ret;
-
 	const struct vdso_data *vd = __get_datapage();
 
-	ret = do_realtime(vd, &ts);
-	if (ret)
-		return gettimeofday_fallback(tv, tz);
+	if (likely(tv != NULL)) {
+		struct timespec ts;
+
+		if (do_realtime(vd, &ts))
+			return gettimeofday_fallback(tv, tz);
 
-	if (tv) {
 		tv->tv_sec = ts.tv_sec;
 		tv->tv_usec = ts.tv_nsec / 1000;
 	}
-	if (tz) {
+
+	if (unlikely(tz != NULL)) {
 		tz->tz_minuteswest = vd->tz_minuteswest;
 		tz->tz_dsttime = vd->tz_dsttime;
 	}
 
-	return ret;
-}
-
-/* Avoid unresolved references emitted by GCC */
-
-void __aeabi_unwind_cpp_pr0(void)
-{
-}
-
-void __aeabi_unwind_cpp_pr1(void)
-{
-}
-
-void __aeabi_unwind_cpp_pr2(void)
-{
+	return 0;
 }
-- 
2.18.0.rc1.244.gcf134e6275-goog