On Thu, Apr 24, 2025 at 04:10:04PM +0200, Jan Stancek wrote:
> On Mon, Mar 03, 2025 at 12:11:10PM +0100, Thomas Weißschuh wrote:
> > From: Anna-Maria Behnsen <anna-ma...@linutronix.de>
> >
> > To support multiple PTP clocks, the VDSO data structure needs to be
> > reworked. All clock specific data will end up in struct vdso_clock and in
> > struct vdso_time_data there will be array of it. By now, vdso_clock is
> > simply a define which maps vdso_clock to vdso_time_data.
> >
> > Prepare for the rework of these structures by adding struct vdso_clock
> > pointer argument to do_hres_timens(), and replace the struct vdso_time_data
> > pointer with the new pointer arugment whenever applicable.
> >
> > No functional change.
> >
> > Signed-off-by: Anna-Maria Behnsen <anna-ma...@linutronix.de>
> > Signed-off-by: Nam Cao <nam...@linutronix.de>
> > Signed-off-by: Thomas Weißschuh <thomas.weisssc...@linutronix.de>
> > ---
> > lib/vdso/gettimeofday.c | 35 ++++++++++++++++++-----------------
> > 1 file changed, 18 insertions(+), 17 deletions(-)
> >
>
> starting with this patch, I'm seeing user-space crashes when using
> clock_gettime():
> BAD -> 83a2a6b8cfc5 vdso/gettimeofday: Prepare do_hres_timens() for
> introduction of struct vdso_clock
> GOOD -> 64c3613ce31a vdso/gettimeofday: Prepare do_hres() for introduction
> of struct vdso_clock
>
> It appears to be unique to aarch64 with 64k pages, and can be reproduced with
> LTP clock_gettime03 [1]:
> command: clock_gettime03 tst_kconfig.c:88: TINFO: Parsing kernel config
> '/lib/modules/6.15.0-0.rc3.20250423gitbc3372351d0c.30.eln147.aarch64+64k/build/.config'
> tst_test.c:1903: TINFO: LTP version: 20250130-231-gd02c2aea3
> tst_test.c:1907: TINFO: Tested kernel:
> 6.15.0-0.rc3.20250423gitbc3372351d0c.30.eln147.aarch64+64k #1 SMP
> PREEMPT_DYNAMIC Wed Apr 23 23:23:54 UTC 2025 aarch64
> tst_kconfig.c:88: TINFO: Parsing kernel config
> '/lib/modules/6.15.0-0.rc3.20250423gitbc3372351d0c.30.eln147.aarch64+64k/build/.config'
> tst_test.c:1720: TINFO: Overall timeout per run is 0h 05m 24s
> clock_gettime03.c:121: TINFO: Testing variant: vDSO or syscall with libc
> spec
> clock_gettime03.c:76: TPASS: Offset (CLOCK_MONOTONIC) is correct 10000ms
> clock_gettime03.c:86: TPASS: Offset (CLOCK_MONOTONIC) is correct 0ms
> clock_gettime03.c:76: TPASS: Offset (CLOCK_BOOTTIME) is correct 10000ms
> clock_gettime03.c:86: TPASS: Offset (CLOCK_BOOTTIME) is correct 0ms
> clock_gettime03.c:76: TPASS: Offset (CLOCK_MONOTONIC) is correct -10000ms
> clock_gettime03.c:86: TPASS: Offset (CLOCK_MONOTONIC) is correct 0ms
> clock_gettime03.c:76: TPASS: Offset (CLOCK_BOOTTIME) is correct -10000ms
> clock_gettime03.c:86: TPASS: Offset (CLOCK_BOOTTIME) is correct 0ms
> tst_test.c:438: TBROK: Child (233649) killed by signal SIGSEGV
>
> or with:
> --------------------- 8< ----------------------
> #define _GNU_SOURCE
> #include <sched.h>
> #include <time.h>
> #include <unistd.h>
>
>
> #include <sys/wait.h>
>
> int main(void)
> {
> struct timespec tp;
> pid_t child;
> int status;
>
> unshare(CLONE_NEWTIME);
>
> child = fork();
> if (child == 0) {
> clock_gettime(CLOCK_MONOTONIC_RAW, &tp);
> }
>
> wait(&status);
> return status;
> }
>
> # ./a.out ; echo $?
> 139
> --------------------- >8 ----------------------
>
> RPMs and configs can be found at Fedora koji, latest build is at [2] (look
> for kernel-64k).
Hi Jan,
Thanks for the great error report.
Can you try the following change (on top of v6.15-rc1, should also work with
current master)?
diff --git a/lib/vdso/gettimeofday.c b/lib/vdso/gettimeofday.c
index 93ef801a97ef..867ce53cca94 100644
--- a/lib/vdso/gettimeofday.c
+++ b/lib/vdso/gettimeofday.c
@@ -85,14 +85,18 @@ static __always_inline
int do_hres_timens(const struct vdso_time_data *vdns, const struct vdso_clock
*vcns,
clockid_t clk, struct __kernel_timespec *ts)
{
- const struct vdso_time_data *vd = __arch_get_vdso_u_timens_data(vdns);
const struct timens_offset *offs = &vcns->offset[clk];
- const struct vdso_clock *vc = vd->clock_data;
+ const struct vdso_time_data *vd;
+ const struct vdso_clock *vc;
const struct vdso_timestamp *vdso_ts;
u64 cycles, ns;
u32 seq;
s64 sec;
+ vd = vdns - (clk == CLOCK_MONOTONIC_RAW ? CS_RAW : CS_HRES_COARSE);
+ vd = __arch_get_vdso_u_timens_data(vd);
+ vc = vd->clock_data;
+
if (clk != CLOCK_MONOTONIC_RAW)
vc = &vc[CS_HRES_COARSE];
else
I'll do some proper testing tomorrow.
Thomas
> [1]
> https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/syscalls/clock_gettime/clock_gettime03.c
> [2] https://koji.fedoraproject.org/koji/buildinfo?buildID=2704401
