[PATCH v3 12/12] lib: vdso: do not expose gettimeofday, if no arch supported timer

From: Mark Salyzyn
Date: Fri Oct 27 2017 - 18:28:13 EST


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@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: linux-kernel@xxxxxxxxxxxxxxx
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx

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

---
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 0546ff12673d..22d0873778ed 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)

@@ -293,30 +295,6 @@ static __always_inline notrace int do_boottime(const struct vdso_data *vd,
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)
@@ -330,6 +308,7 @@ 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;
@@ -346,6 +325,7 @@ notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
if (do_boottime(vd, ts))
goto fallback;
break;
+#endif
default:
goto fallback;
}
@@ -355,6 +335,7 @@ 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();
@@ -376,21 +357,28 @@ notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)

return 0;
}
+#endif

int __vdso_clock_getres(clockid_t clock_id, struct timespec *res)
{
typeof(res->tv_nsec) nsec;

- if (clock_id == CLOCK_REALTIME ||
- clock_id == CLOCK_BOOTTIME ||
- clock_id == CLOCK_MONOTONIC ||
- clock_id == CLOCK_MONOTONIC_RAW)
- nsec = MONOTONIC_RES_NSEC;
- else if (clock_id == CLOCK_REALTIME_COARSE ||
- clock_id == CLOCK_MONOTONIC_COARSE)
+ switch (clock_id) {
+ 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_id, res);
+ }

if (likely(res != NULL)) {
res->tv_sec = 0;
--
2.15.0.rc2.357.g7e34df9404-goog