On Wed, Mar 19, 2025 at 10:59:57AM +0800, Shuai Xue wrote:
> + ARM maintainers for review.
>
> 在 2025/3/12 14:15, Shuai Xue 写道:
> > The pidfd_test fails on the ARM64 platform with the following error:
> >
> > Bail out! pidfd_poll check for premature notification on child thread
> > exec test: Failed
> >
> > When exception-trace is enabled, the kernel logs the details:
> >
> > #echo 1 > /proc/sys/debug/exception-trace
> > #dmesg | tail -n 20
> > [48628.713023] pidfd_test[1082142]: unhandled exception: SP Alignment,
> > ESR 0x000000009a000000, SP/PC alignment exception in pidfd_test[400000+4000]
> > [48628.713049] CPU: 21 PID: 1082142 Comm: pidfd_test Kdump: loaded
> > Tainted: G W E 6.6.71-3_rc1.al8.aarch64 #1
> > [48628.713051] Hardware name: AlibabaCloud
> > AliServer-Xuanwu2.0AM-1UC1P-5B/AS1111MG1, BIOS 1.2.M1.AL.P.157.00 07/29/2023
> > [48628.713053] pstate: 60001800 (nZCv daif -PAN -UAO -TCO -DIT +SSBS
> > BTYPE=-c)
> > [48628.713055] pc : 0000000000402100
> > [48628.713056] lr : 0000ffff98288f9c
> > [48628.713056] sp : 0000ffffde49daa8
> > [48628.713057] x29: 0000000000000000 x28: 0000000000000000 x27:
> > 0000000000000000
> > [48628.713060] x26: 0000000000000000 x25: 0000000000000000 x24:
> > 0000000000000000
> > [48628.713062] x23: 0000000000000000 x22: 0000000000000000 x21:
> > 0000000000400e80
> > [48628.713065] x20: 0000000000000000 x19: 0000000000402650 x18:
> > 0000000000000000
> > [48628.713067] x17: 00000000004200d8 x16: 0000ffff98288f40 x15:
> > 0000ffffde49b92c
> > [48628.713070] x14: 0000000000000000 x13: 0000000000000000 x12:
> > 0000000000000000
> > [48628.713072] x11: 0000000000001011 x10: 0000000000402100 x9 :
> > 0000000000000010
> > [48628.713074] x8 : 00000000000000dc x7 : 3861616239346564 x6 :
> > 000000000000000a
> > [48628.713077] x5 : 0000ffffde49daa8 x4 : 000000000000000a x3 :
> > 0000ffffde49daa8
> > [48628.713079] x2 : 0000ffffde49dadc x1 : 0000ffffde49daa8 x0 :
> > 0000000000000000
> >
> > According to ARM ARM D1.3.10.2 SP alignment checking:
> >
> > > When the SP is used as the base address of a calculation, regardless of
> > > any offset applied by the instruction, if bits [3:0] of the SP are not
> > > 0b0000, there is a misaligned SP.
> >
> > To fix it, align the stack with 16 bytes.
> >
> > Signed-off-by: Shuai Xue <xuesh...@linux.alibaba.com>
> > ---
> > tools/testing/selftests/pidfd/pidfd_test.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/tools/testing/selftests/pidfd/pidfd_test.c
> > b/tools/testing/selftests/pidfd/pidfd_test.c
> > index c081ae91313a..ec161a7c3ff9 100644
> > --- a/tools/testing/selftests/pidfd/pidfd_test.c
> > +++ b/tools/testing/selftests/pidfd/pidfd_test.c
> > @@ -33,7 +33,7 @@ static bool have_pidfd_send_signal;
> > static pid_t pidfd_clone(int flags, int *pidfd, int (*fn)(void *))
> > {
> > size_t stack_size = 1024;
> > - char *stack[1024] = { 0 };
> > + char *stack[1024] __attribute__((aligned(16))) = {0};
> > #ifdef __ia64__
> > return __clone2(fn, stack, stack_size, flags | SIGCHLD, NULL, pidfd);
The arm64 alignment requirement is correct, but I don't really grok what
this code is trying to do. If it's not using CLONE_VM, why bother passing
a separate stack? If it _is_ using CLONE_VM, then surely the stack needs
to be allocated somewhere other than the caller stack?
Will
