queue-4.9/arm64-vdso-fix-clock_getres-for-clock_realtime.patch

   1 From 796b5a9a42a8d56d008809b67c84d29c0766c84f Mon Sep 17 00:00:00 2001
   2 From: Vincenzo Frascino <vincenzo.frascino@arm.com>
   3 Date: Tue, 16 Apr 2019 17:14:30 +0100
   4 Subject: arm64: vdso: Fix clock_getres() for CLOCK_REALTIME
   5
   6 [ Upstream commit 81fb8736dd81da3fe94f28968dac60f392ec6746 ]
   7
   8 clock_getres() in the vDSO library has to preserve the same behaviour
   9 of posix_get_hrtimer_res().
  10
  11 In particular, posix_get_hrtimer_res() does:
  12
  13     sec = 0;
  14     ns = hrtimer_resolution;
  15
  16 where 'hrtimer_resolution' depends on whether or not high resolution
  17 timers are enabled, which is a runtime decision.
  18
  19 The vDSO incorrectly returns the constant CLOCK_REALTIME_RES. Fix this
  20 by exposing 'hrtimer_resolution' in the vDSO datapage and returning that
  21 instead.
  22
  23 Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
  24 Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
  25 [will: Use WRITE_ONCE(), move adr off COARSE path, renumber labels, use 'w' reg]
  26 Signed-off-by: Will Deacon <will.deacon@arm.com>
  27 Signed-off-by: Sasha Levin <sashal@kernel.org>
  28 ---
  29  arch/arm64/include/asm/vdso_datapage.h | 1 +
  30  arch/arm64/kernel/asm-offsets.c        | 2 +-
  31  arch/arm64/kernel/vdso.c               | 3 +++
  32  arch/arm64/kernel/vdso/gettimeofday.S  | 7 +++----
  33  4 files changed, 8 insertions(+), 5 deletions(-)
  34
  35 diff --git a/arch/arm64/include/asm/vdso_datapage.h b/arch/arm64/include/asm/vdso_datapage.h
  36 index 2b9a63771eda8..f89263c8e11af 100644
  37 --- a/arch/arm64/include/asm/vdso_datapage.h
  38 +++ b/arch/arm64/include/asm/vdso_datapage.h
  39 @@ -38,6 +38,7 @@ struct vdso_data {
  40         __u32 tz_minuteswest;   /* Whacky timezone stuff */
  41         __u32 tz_dsttime;
  42         __u32 use_syscall;
  43 +       __u32 hrtimer_res;
  44  };
  45
  46  #endif /* !__ASSEMBLY__ */
  47 diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
  48 index bd239b1b7a681..95878bea27f93 100644
  49 --- a/arch/arm64/kernel/asm-offsets.c
  50 +++ b/arch/arm64/kernel/asm-offsets.c
  51 @@ -92,7 +92,7 @@ int main(void)
  52    DEFINE(CLOCK_REALTIME,       CLOCK_REALTIME);
  53    DEFINE(CLOCK_MONOTONIC,      CLOCK_MONOTONIC);
  54    DEFINE(CLOCK_MONOTONIC_RAW,  CLOCK_MONOTONIC_RAW);
  55 -  DEFINE(CLOCK_REALTIME_RES,   MONOTONIC_RES_NSEC);
  56 +  DEFINE(CLOCK_REALTIME_RES,   offsetof(struct vdso_data, hrtimer_res));
  57    DEFINE(CLOCK_REALTIME_COARSE,        CLOCK_REALTIME_COARSE);
  58    DEFINE(CLOCK_MONOTONIC_COARSE,CLOCK_MONOTONIC_COARSE);
  59    DEFINE(CLOCK_COARSE_RES,     LOW_RES_NSEC);
  60 diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
  61 index 4bcfe01b5aad4..c9b9a5a322eb1 100644
  62 --- a/arch/arm64/kernel/vdso.c
  63 +++ b/arch/arm64/kernel/vdso.c
  64 @@ -213,6 +213,9 @@ void update_vsyscall(struct timekeeper *tk)
  65         vdso_data->wtm_clock_sec                = tk->wall_to_monotonic.tv_sec;
  66         vdso_data->wtm_clock_nsec               = tk->wall_to_monotonic.tv_nsec;
  67
  68 +       /* Read without the seqlock held by clock_getres() */
  69 +       WRITE_ONCE(vdso_data->hrtimer_res, hrtimer_resolution);
  70 +
  71         if (!use_syscall) {
  72                 /* tkr_mono.cycle_last == tkr_raw.cycle_last */
  73                 vdso_data->cs_cycle_last        = tk->tkr_mono.cycle_last;
  74 diff --git a/arch/arm64/kernel/vdso/gettimeofday.S b/arch/arm64/kernel/vdso/gettimeofday.S
  75 index 76320e9209651..df829c4346fac 100644
  76 --- a/arch/arm64/kernel/vdso/gettimeofday.S
  77 +++ b/arch/arm64/kernel/vdso/gettimeofday.S
  78 @@ -301,13 +301,14 @@ ENTRY(__kernel_clock_getres)
  79         ccmp    w0, #CLOCK_MONOTONIC_RAW, #0x4, ne
  80         b.ne    1f
  81
  82 -       ldr     x2, 5f
  83 +       adr     vdso_data, _vdso_data
  84 +       ldr     w2, [vdso_data, #CLOCK_REALTIME_RES]
  85         b       2f
  86  1:
  87         cmp     w0, #CLOCK_REALTIME_COARSE
  88         ccmp    w0, #CLOCK_MONOTONIC_COARSE, #0x4, ne
  89         b.ne    4f
  90 -       ldr     x2, 6f
  91 +       ldr     x2, 5f
  92  2:
  93         cbz     w1, 3f
  94         stp     xzr, x2, [x1]
  95 @@ -321,8 +322,6 @@ ENTRY(__kernel_clock_getres)
  96         svc     #0
  97         ret
  98  5:
  99 -       .quad   CLOCK_REALTIME_RES
 100 -6:
 101         .quad   CLOCK_COARSE_RES
 102         .cfi_endproc
 103  ENDPROC(__kernel_clock_getres)
 104 --
 105 2.20.1
 106