On Thu, 15 Aug 2019, Dmitry Safonov wrote:
> ---
> arch/Kconfig | 5 +++
> arch/x86/Kconfig | 1 +
> arch/x86/entry/vdso/vdso-layout.lds.S | 9 ++++-
> arch/x86/entry/vdso/vdso2c.c | 3 ++
> arch/x86/entry/vdso/vma.c | 12 +++++++
> arch/x86/include/asm/vdso.h | 1 +
> init/Kconfig | 1 +
> lib/vdso/gettimeofday.c | 47 +++++++++++++++++++++++++++
This needs to be split into the generic lib/vdso part and then x86 making
use of it.
> +#ifdef CONFIG_TIME_NS
This should be COMPILE_WITH_TIME_NS and not CONFIG_TIME_NS
> +extern u8 timens_page
> + __attribute__((visibility("hidden")));
> +
> +notrace static __always_inline void clk_to_ns(clockid_t clk, struct __kernel_timespec *ts)
This needs notrace because?
> +{
> + struct timens_offsets *timens = (struct timens_offsets *) &timens_page;
> + struct timespec64 *offset64;
> +
> + switch (clk) {
> + case CLOCK_MONOTONIC:
> + case CLOCK_MONOTONIC_COARSE:
> + case CLOCK_MONOTONIC_RAW:
> + offset64 = &timens->monotonic;
> + break;
> + case CLOCK_BOOTTIME:
> + offset64 = &timens->boottime;
> + break;
> + default:
> + return;
> + }
> +
> + /*
> + * The kernel allows to set a negative offset only if the current clock
> + * value in a namespace is positive, so the result tv_sec can't be
> + * negative here.
> + */
> + ts->tv_nsec += offset64->tv_nsec;
> + ts->tv_sec += offset64->tv_sec;
> + if (ts->tv_nsec >= NSEC_PER_SEC) {
> + ts->tv_nsec -= NSEC_PER_SEC;
> + ts->tv_sec++;
> + }
> + if (ts->tv_nsec < 0) {
> + ts->tv_nsec += NSEC_PER_SEC;
> + ts->tv_sec--;
> + }
That's broken for 32bit user space on 64bit hosts. On LE due to
misalignment and on BE because 32bit will read always 0.
> +}
> +#else
> +notrace static __always_inline void clk_to_ns(clockid_t clk, struct __kernel_timespec *ts) {}
> +#endif
> +
> static int do_hres(const struct vdso_data *vd, clockid_t clk,
> struct __kernel_timespec *ts)
> {
> @@ -65,6 +108,8 @@ static int do_hres(const struct vdso_data *vd, clockid_t clk,
> ts->tv_sec = sec + __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
> ts->tv_nsec = ns;
>
> + clk_to_ns(clk, ts);
> +
> return 0;
> }
>
> @@ -79,6 +124,8 @@ static void do_coarse(const struct vdso_data *vd, clockid_t clk,
> ts->tv_sec = vdso_ts->sec;
> ts->tv_nsec = vdso_ts->nsec;
> } while (unlikely(vdso_read_retry(vd, seq)));
> +
> + clk_to_ns(clk, ts);
> }
>
> static __maybe_unused int
> --
> 2.22.0
>
>
