Re: [PATCHv6 22/36] x86/vdso: Add offsets page in vvar
From: Thomas Gleixner <hidden>
Date: 2019-08-15 19:21:51
Also in:
lkml
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.
quoted hunk ↗ jump to hunk
+} +#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