[ Upstream commit 81fb8736dd81da3fe94f28968dac60f392ec6746 ]
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;
where 'hrtimer_resolution' depends on whether or not high resolution timers are enabled, which is a runtime decision.
The vDSO incorrectly returns the constant CLOCK_REALTIME_RES. Fix this by exposing 'hrtimer_resolution' in the vDSO datapage and returning that instead.
Reviewed-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Vincenzo Frascino vincenzo.frascino@arm.com [will: Use WRITE_ONCE(), move adr off COARSE path, renumber labels, use 'w' reg] Signed-off-by: Will Deacon will.deacon@arm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/arm64/include/asm/vdso_datapage.h | 1 + arch/arm64/kernel/asm-offsets.c | 2 +- arch/arm64/kernel/vdso.c | 3 +++ arch/arm64/kernel/vdso/gettimeofday.S | 7 +++---- 4 files changed, 8 insertions(+), 5 deletions(-)
diff --git a/arch/arm64/include/asm/vdso_datapage.h b/arch/arm64/include/asm/vdso_datapage.h index 2b9a63771eda8..f89263c8e11af 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 bd239b1b7a681..95878bea27f93 100644 --- a/arch/arm64/kernel/asm-offsets.c +++ b/arch/arm64/kernel/asm-offsets.c @@ -92,7 +92,7 @@ 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 4bcfe01b5aad4..c9b9a5a322eb1 100644 --- a/arch/arm64/kernel/vdso.c +++ b/arch/arm64/kernel/vdso.c @@ -213,6 +213,9 @@ void update_vsyscall(struct timekeeper *tk) vdso_data->wtm_clock_sec = tk->wall_to_monotonic.tv_sec; vdso_data->wtm_clock_nsec = tk->wall_to_monotonic.tv_nsec;
+ /* Read without the seqlock held by clock_getres() */ + WRITE_ONCE(vdso_data->hrtimer_res, hrtimer_resolution); + if (!use_syscall) { /* tkr_mono.cycle_last == tkr_raw.cycle_last */ vdso_data->cs_cycle_last = tk->tkr_mono.cycle_last; diff --git a/arch/arm64/kernel/vdso/gettimeofday.S b/arch/arm64/kernel/vdso/gettimeofday.S index 76320e9209651..df829c4346fac 100644 --- a/arch/arm64/kernel/vdso/gettimeofday.S +++ b/arch/arm64/kernel/vdso/gettimeofday.S @@ -301,13 +301,14 @@ ENTRY(__kernel_clock_getres) ccmp w0, #CLOCK_MONOTONIC_RAW, #0x4, ne b.ne 1f
- ldr x2, 5f + adr vdso_data, _vdso_data + ldr w2, [vdso_data, #CLOCK_REALTIME_RES] b 2f 1: cmp w0, #CLOCK_REALTIME_COARSE ccmp w0, #CLOCK_MONOTONIC_COARSE, #0x4, ne b.ne 4f - ldr x2, 6f + ldr x2, 5f 2: cbz w1, 3f stp xzr, x2, [x1] @@ -321,8 +322,6 @@ ENTRY(__kernel_clock_getres) svc #0 ret 5: - .quad CLOCK_REALTIME_RES -6: .quad CLOCK_COARSE_RES .cfi_endproc ENDPROC(__kernel_clock_getres)