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

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Message-ID: <aApGPAoctq_eoE2g@t14ultra>
Date: Thu, 24 Apr 2025 16:10:04 +0200
From: Jan Stancek <jstancek@...hat.com>
To: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Cc: Andy Lutomirski <luto@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
	Vincenzo Frascino <vincenzo.frascino@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Anna-Maria Behnsen <anna-maria@...utronix.de>,
	Frederic Weisbecker <frederic@...nel.org>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Madhavan Srinivasan <maddy@...ux.ibm.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	Naveen N Rao <naveen@...nel.org>,
	Heiko Carstens <hca@...ux.ibm.com>,
	Vasily Gorbik <gor@...ux.ibm.com>,
	Alexander Gordeev <agordeev@...ux.ibm.com>,
	Christian Borntraeger <borntraeger@...ux.ibm.com>,
	Sven Schnelle <svens@...ux.ibm.com>, Arnd Bergmann <arnd@...db.de>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
	linux-arch@...r.kernel.org, Nam Cao <namcao@...utronix.de>,
	jstancek@...hat.com
Subject: Re: [PATCH 08/19] vdso/gettimeofday: Prepare do_hres_timens() for
 introduction of struct vdso_clock

On Mon, Mar 03, 2025 at 12:11:10PM +0100, Thomas Weißschuh wrote:
>From: Anna-Maria Behnsen <anna-maria@...utronix.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@...utronix.de>
>Signed-off-by: Nam Cao <namcao@...utronix.de>
>Signed-off-by: Thomas Weißschuh <thomas.weissschuh@...utronix.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