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SubjectRe: [patch 2/5] lib/vdso: Move fallback invocation to the callers
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On 7/28/19 2:12 PM, Thomas Gleixner wrote:
> To allow syscall fallbacks using the legacy 32bit syscall for 32bit VDSO
> builds, move the fallback invocation out into the callers.
>
> Split the common code out of __cvdso_clock_gettime/getres() and invoke the
> syscall fallback in the 64bit and 32bit variants.
>
> Preparatory work for using legacy syscalls in 32bit VDSO. No functional
> change.
>

Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Tested-by: Vincenzo Frascino <vincenzo.frascino@arm.com>

> Fixes: 00b26474c2f1 ("lib/vdso: Provide generic VDSO implementation")
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> ---
> lib/vdso/gettimeofday.c | 53 ++++++++++++++++++++++++++++++++----------------
> 1 file changed, 36 insertions(+), 17 deletions(-)
>
> --- a/lib/vdso/gettimeofday.c
> +++ b/lib/vdso/gettimeofday.c
> @@ -51,7 +51,7 @@ static int do_hres(const struct vdso_dat
> ns = vdso_ts->nsec;
> last = vd->cycle_last;
> if (unlikely((s64)cycles < 0))
> - return clock_gettime_fallback(clk, ts);
> + return -1;
>
> ns += vdso_calc_delta(cycles, last, vd->mask, vd->mult);
> ns >>= vd->shift;
> @@ -82,14 +82,14 @@ static void do_coarse(const struct vdso_
> }
>
> static __maybe_unused int
> -__cvdso_clock_gettime(clockid_t clock, struct __kernel_timespec *ts)
> +__cvdso_clock_gettime_common(clockid_t clock, struct __kernel_timespec *ts)
> {
> const struct vdso_data *vd = __arch_get_vdso_data();
> u32 msk;
>
> /* Check for negative values or invalid clocks */
> if (unlikely((u32) clock >= MAX_CLOCKS))
> - goto fallback;
> + return -1;
>
> /*
> * Convert the clockid to a bitmask and use it to check which
> @@ -104,9 +104,17 @@ static __maybe_unused int
> } else if (msk & VDSO_RAW) {
> return do_hres(&vd[CS_RAW], clock, ts);
> }
> + return -1;
> +}
>
> -fallback:
> - return clock_gettime_fallback(clock, ts);
> +static __maybe_unused int
> +__cvdso_clock_gettime(clockid_t clock, struct __kernel_timespec *ts)
> +{
> + int ret = __cvdso_clock_gettime_common(clock, ts);
> +
> + if (unlikely(ret))
> + return clock_gettime_fallback(clock, ts);
> + return 0;
> }
>
> static __maybe_unused int
> @@ -115,9 +123,12 @@ static __maybe_unused int
> struct __kernel_timespec ts;
> int ret;
>
> - ret = __cvdso_clock_gettime(clock, &ts);
> + ret = __cvdso_clock_gettime_common(clock, &ts);
>
> - if (ret == 0) {
> + if (unlikely(ret))
> + ret = clock_gettime_fallback(clock, &ts);
> +
> + if (likely(!ret)) {
> res->tv_sec = ts.tv_sec;
> res->tv_nsec = ts.tv_nsec;
> }
> @@ -163,17 +174,18 @@ static __maybe_unused time_t __cvdso_tim
>
> #ifdef VDSO_HAS_CLOCK_GETRES
> static __maybe_unused
> -int __cvdso_clock_getres(clockid_t clock, struct __kernel_timespec *res)
> +int __cvdso_clock_getres_common(clockid_t clock, struct __kernel_timespec *res)
> {
> const struct vdso_data *vd = __arch_get_vdso_data();
> - u64 ns;
> + u64 hrtimer_res;
> u32 msk;
> - u64 hrtimer_res = READ_ONCE(vd[CS_HRES_COARSE].hrtimer_res);
> + u64 ns;
>
> /* Check for negative values or invalid clocks */
> if (unlikely((u32) clock >= MAX_CLOCKS))
> - goto fallback;
> + return -1;
>
> + hrtimer_res = READ_ONCE(vd[CS_HRES_COARSE].hrtimer_res);
> /*
> * Convert the clockid to a bitmask and use it to check which
> * clocks are handled in the VDSO directly.
> @@ -195,16 +207,22 @@ int __cvdso_clock_getres(clockid_t clock
> */
> ns = hrtimer_res;
> } else {
> - goto fallback;
> + return -1;
> }
>
> res->tv_sec = 0;
> res->tv_nsec = ns;
>
> return 0;
> +}
> +
> +int __cvdso_clock_getres(clockid_t clock, struct __kernel_timespec *res)
> +{
> + int ret = __cvdso_clock_getres_common(clock, res);
>
> -fallback:
> - return clock_getres_fallback(clock, res);
> + if (unlikely(ret))
> + return clock_getres_fallback(clock, res);
> + return 0;
> }
>
> static __maybe_unused int
> @@ -213,13 +231,14 @@ static __maybe_unused int
> struct __kernel_timespec ts;
> int ret;
>
> - ret = __cvdso_clock_getres(clock, &ts);
> + ret = __cvdso_clock_getres_common(clock, &ts);
> + if (unlikely(ret))
> + ret = clock_getres_fallback(clock, &ts);
>
> - if (ret == 0) {
> + if (likely(!ret)) {
> res->tv_sec = ts.tv_sec;
> res->tv_nsec = ts.tv_nsec;
> }
> -
> return ret;
> }
> #endif /* VDSO_HAS_CLOCK_GETRES */
>
>

--
Regards,
Vincenzo

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