Re: [PATCH 08/19] vdso/gettimeofday: Prepare do_hres_timens() for introduction of struct vdso_clock

[Jan Stancek <jstancek@redhat.com>]

On Mon, Mar 03, 2025 at 12:11:10PM +0100, Thomas Weißschuh wrote:
>From: Anna-Maria Behnsen <anna-maria@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-maria@linutronix.de>
>Signed-off-by: Nam Cao <namcao@linutronix.de>
>Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
>---
> lib/vdso/gettimeofday.c | 35 ++++++++++++++++++-----------------
> 1 file changed, 18 insertions(+), 17 deletions(-)
>

Hi,

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).

Regards,
Jan

[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