clock_getres in the vDSO library has to preserve the same behaviour
of posix_get_hrtimer_res().
In particular, posix_get_hrtimer_res() does:
sec = 0;
ns = hrtimer_resolution;
and hrtimer_resolution depends on the enablement of the high
resolution timers that can happen either at compile or at run time.
Fix the arm64 vdso implementation of clock_getres keeping a copy of
hrtimer_resolution in vdso data and using that directly.
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
---
arch/arm64/include/asm/vdso_datapage.h | 1 +
arch/arm64/kernel/asm-offsets.c | 2 +-
arch/arm64/kernel/vdso.c | 2 ++
arch/arm64/kernel/vdso/gettimeofday.S | 25 ++++++++++++++-----------
4 files changed, 18 insertions(+), 12 deletions(-)
diff --git a/arch/arm64/include/asm/vdso_datapage.h b/arch/arm64/include/asm/vdso_datapage.h
index 2b9a63771eda..f89263c8e11a 100644
--- a/arch/arm64/include/asm/vdso_datapage.h
+++ b/arch/arm64/include/asm/vdso_datapage.h
@@ -38,6 +38,7 @@ struct vdso_data {
__u32 tz_minuteswest; /* Whacky timezone stuff */
__u32 tz_dsttime;
__u32 use_syscall;
+ __u32 hrtimer_res;
};
#endif /* !__ASSEMBLY__ */
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index 7f40dcbdd51d..e10e2a5d9ddc 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -94,7 +94,7 @@ int main(void)
DEFINE(CLOCK_REALTIME, CLOCK_REALTIME);
DEFINE(CLOCK_MONOTONIC, CLOCK_MONOTONIC);
DEFINE(CLOCK_MONOTONIC_RAW, CLOCK_MONOTONIC_RAW);
- DEFINE(CLOCK_REALTIME_RES, MONOTONIC_RES_NSEC);
+ DEFINE(CLOCK_REALTIME_RES, offsetof(struct vdso_data, hrtimer_res));
DEFINE(CLOCK_REALTIME_COARSE, CLOCK_REALTIME_COARSE);
DEFINE(CLOCK_MONOTONIC_COARSE,CLOCK_MONOTONIC_COARSE);
DEFINE(CLOCK_COARSE_RES, LOW_RES_NSEC);
diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index 2d419006ad43..47ba72345739 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -245,6 +245,8 @@ void update_vsyscall(struct timekeeper *tk)
vdso_data->cs_shift = tk->tkr_mono.shift;
}
+ vdso_data->hrtimer_res = hrtimer_resolution;
+
smp_wmb();
++vdso_data->tb_seq_count;
}
diff --git a/arch/arm64/kernel/vdso/gettimeofday.S b/arch/arm64/kernel/vdso/gettimeofday.S
index c39872a7b03c..7a2cd2f8e13a 100644
--- a/arch/arm64/kernel/vdso/gettimeofday.S
+++ b/arch/arm64/kernel/vdso/gettimeofday.S
@@ -296,32 +296,35 @@ ENDPROC(__kernel_clock_gettime)
/* int __kernel_clock_getres(clockid_t clock_id, struct timespec *res); */
ENTRY(__kernel_clock_getres)
.cfi_startproc
+ adr vdso_data, _vdso_data
cmp w0, #CLOCK_REALTIME
ccmp w0, #CLOCK_MONOTONIC, #0x4, ne
ccmp w0, #CLOCK_MONOTONIC_RAW, #0x4, ne
- b.ne 1f
+ b.ne 2f
- ldr x2, 5f
- b 2f
-1:
+1: /* Get hrtimer_res */
+ seqcnt_acquire
+ syscall_check fail=5f
+ ldr x2, [vdso_data, #CLOCK_REALTIME_RES]
+ seqcnt_check fail=1b
+ b 3f
+2:
cmp w0, #CLOCK_REALTIME_COARSE
ccmp w0, #CLOCK_MONOTONIC_COARSE, #0x4, ne
- b.ne 4f
+ b.ne 5f
ldr x2, 6f
-2:
- cbz x1, 3f
+3:
+ cbz x1, 4f
stp xzr, x2, [x1]
-3: /* res == NULL. */
+4: /* res == NULL. */
mov w0, wzr
ret
-4: /* Syscall fallback. */
+5: /* Syscall fallback. */
mov x8, #__NR_clock_getres
svc #0
ret
-5:
- .quad CLOCK_REALTIME_RES
6:
.quad CLOCK_COARSE_RES
.cfi_endproc
--
2.21.0
