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arch/arm/armv8-m: stack pointer should be 8-byte aligned in signal context

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Since the alignment of the signal context is affected by XCPTCONTEXT_SIZE in
different Kconfig,  sometimes the stack pointer is not aligned to 8 bytes, this
is not what the software and compiler expect, for example,  if va_list() obtains
wide data of type long long, the offset will be wrong, So in this commit, we set
stack-aligned the base offset so that the correct offset will be set during context
restoration.

1. test code:
|            void signal_handler(int signo, siginfo_t *info, void *context) {
|                long long ttt = 1024000;
|                printf("%lld\n", ttt);
|            }
|
|            struct itimerspec its = {   .it_value.tv_sec  = 1,
|                .it_value.tv_nsec = 0,
|                .it_interval.tv_sec  = 1,
|                .it_interval.tv_nsec = 0
|            };
|
|            int main(int argc, FAR char *argv[])
|            {
|                struct sigevent evp;
|                timer_t timer_id;
|
|                memset(&evp, 0, sizeof(evp));
|                evp.sigev_notify          = SIGEV_SIGNAL | SIGEV_THREAD_ID;
|                evp.sigev_signo           = SIGALRM;
|                evp.sigev_notify_thread_id = gettid();
|
|                timer_create(CLOCK_REALTIME, &evp, &timer_id);
|
|
|                struct sigaction sa;
|                memset(&sa, 0, sizeof(sa));
|                sa.sa_sigaction = signal_handler;
|                sa.sa_flags = SA_SIGINFO;
|                sigemptyset(&sa.sa_mask);
|
|                sigaction(SIGALRM, &sa, NULL);
|
|                timer_settime(timer_id, 0, &its, NULL);
|
|                while (1)
|                    sleep(1);
|
|                return 0;
|            }

2. before this change:

|            NuttShell (NSH) NuttX-12.10.0
|            nsh> hello
|            4398046527890440
|            4398046527890472
|            4398046527890504
|            4398046527890536

3. after this change:

|            NuttShell (NSH) NuttX-12.10.0
|            nsh> hello
|            1024000
|            1024000
|            1024000
|            1024000

Signed-off-by: chao an <anchao.archer@bytedance.com>
This commit is contained in:
chao an 2025-09-11 13:54:53 +08:00 • committed by Xiang Xiao
parent 754eab4687
commit cf616fd619
1 changed files with 5 additions and 0 deletions
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5
arch/arm/src/armv8-m/arm_schedulesigaction.c
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@ -119,6 +119,11 @@ void up_schedule_sigaction(struct tcb_s *tcb)
tcb->xcp.saved_regs = tcb->xcp.regs;
/* Stack pointer should be 8-byte aligned */
tcb->xcp.regs = (void *)STACK_ALIGN_DOWN(
(uint32_t)tcb->xcp.regs);
/* Duplicate the register context. These will be
* restored by the signal trampoline after the signal has been
* delivered.