[PATCH v4 12/12] lib: vdso: do not expose gettimeofday, if no arch supported timer

* [PATCH v4 12/12] lib: vdso: do not expose gettimeofday, if no arch supported timer
@ 2017-10-31 18:33 ` Mark Salyzyn
  0 siblings, 0 replies; 2+ messages in thread
From: Mark Salyzyn @ 2017-10-31 18:33 UTC (permalink / raw)
  To: linux-kernel
  Cc: Mark Salyzyn, James Morse, Russell King, Catalin Marinas,
	Will Deacon, Andy Lutomirski, Dmitry Safonov, John Stultz,
	Mark Rutland, Laura Abbott, Kees Cook, Ard Biesheuvel,
	Andy Gross, Kevin Brodsky, Andrew Pinski, Thomas Gleixner,
	linux-arm-kernel

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

If ARCH_PROVIDES_TIMER is not defined, do not expose gettimeofday.
libc will default directly to syscall.  Also ifdef clock_gettime
switch cases and stubs if not supported and other unused components.

Signed-off-by: Mark Salyzyn <salyzyn@android.com>
Cc: James Morse <james.morse@arm.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dmitry Safonov <dsafonov@virtuozzo.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Andy Gross <andy.gross@linaro.org>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Andrew Pinski <apinski@cavium.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org

v3:
- do not expose gettimeofday if arch does not support user space timer.

v4:
- update commit message to reflect overall reasoning of patch series.

---
 lib/vdso/vgettimeofday.c | 52 +++++++++++++++++++-----------------------------
 1 file changed, 20 insertions(+), 32 deletions(-)

diff --git a/lib/vdso/vgettimeofday.c b/lib/vdso/vgettimeofday.c
index 4f500aba7e60..896e20e34a23 100644
--- a/lib/vdso/vgettimeofday.c
+++ b/lib/vdso/vgettimeofday.c
@@ -29,7 +29,9 @@
 #include "compiler.h"
 #include "datapage.h"
 
+#ifdef ARCH_PROVIDES_TIMER
 DEFINE_FALLBACK(gettimeofday, struct timeval *, tv, struct timezone *, tz)
+#endif
 DEFINE_FALLBACK(clock_gettime, clockid_t, clock, struct timespec *, ts)
 DEFINE_FALLBACK(clock_getres, clockid_t, clock, struct timespec *, ts)
 
@@ -285,30 +287,6 @@ static notrace int do_boottime(const struct vdso_data *vd, struct timespec *ts)
 	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;
-}
-
-static notrace int do_boottime(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)
@@ -322,6 +300,7 @@ notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
 	case CLOCK_MONOTONIC_COARSE:
 		do_monotonic_coarse(vd, ts);
 		break;
+#ifdef ARCH_PROVIDES_TIMER
 	case CLOCK_REALTIME:
 		if (do_realtime(vd, ts))
 			goto fallback;
@@ -338,6 +317,7 @@ notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
 		if (do_boottime(vd, ts))
 			goto fallback;
 		break;
+#endif
 	default:
 		goto fallback;
 	}
@@ -347,6 +327,7 @@ notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
 	return clock_gettime_fallback(clock, ts);
 }
 
+#ifdef ARCH_PROVIDES_TIMER
 notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
 {
 	const struct vdso_data *vd = __get_datapage();
@@ -368,21 +349,28 @@ notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
 
 	return 0;
 }
+#endif
 
 int __vdso_clock_getres(clockid_t clock, struct timespec *res)
 {
 	long nsec;
 
-	if (clock == CLOCK_REALTIME ||
-	    clock == CLOCK_BOOTTIME ||
-	    clock == CLOCK_MONOTONIC ||
-	    clock == CLOCK_MONOTONIC_RAW)
-		nsec = MONOTONIC_RES_NSEC;
-	else if (clock == CLOCK_REALTIME_COARSE ||
-		 clock == CLOCK_MONOTONIC_COARSE)
+	switch (clock) {
+	case CLOCK_REALTIME_COARSE:
+	case CLOCK_MONOTONIC_COARSE:
 		nsec = LOW_RES_NSEC;
-	else
+		break;
+#ifdef ARCH_PROVIDES_TIMER
+	case CLOCK_REALTIME:
+	case CLOCK_MONOTONIC:
+	case CLOCK_MONOTONIC_RAW:
+	case CLOCK_BOOTTIME:
+		nsec = MONOTONIC_RES_NSEC;
+		break;
+#endif
+	default:
 		return clock_getres_fallback(clock, res);
+	}
 
 	if (likely(res != NULL)) {
 		res->tv_sec = 0;
-- 
2.15.0.rc2.357.g7e34df9404-goog

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