| Message ID | f69ce25f-733d-7931-e59c-e3f1279b965a@redhat.com (mailing list archive) |
|---|---|
| State | Handled Elsewhere, archived |
| Headers | show |
| Series | target/hppa: clear the PSW 'N' bit when delivering signals | expand |
On 9/16/23 15:49, Mikulas Patocka wrote: > qemu-hppa may crash when delivering a signal. It can be demonstrated with > this program. Compile the program with "hppa-linux-gnu-gcc -O2 signal.c" > and run it with "qemu-hppa -one-insn-per-tb a.out". It reports that the > address of the flag is 0xb4 and it crashes when attempting to touch it. > > #include <stdio.h> > #include <stdlib.h> > #include <sys/time.h> > #include <signal.h> > > sig_atomic_t flag; > > void sig(int n) > { > printf("&flag: %p\n", &flag); > flag = 1; > } > > int main(void) > { > struct sigaction sa; > struct itimerval it; > > sa.sa_handler = sig; > sigemptyset(&sa.sa_mask); > sa.sa_flags = SA_RESTART; > if (sigaction(SIGALRM, &sa, NULL)) perror("sigaction"), exit(1); > > it.it_interval.tv_sec = 0; > it.it_interval.tv_usec = 100; > it.it_value.tv_sec = it.it_interval.tv_sec; > it.it_value.tv_usec = it.it_interval.tv_usec; > > if (setitimer(ITIMER_REAL, &it, NULL)) perror("setitimer"), exit(1); > > while (1) { > } > } > > The reason for the crash is that the signal handling routine doesn't clear > the 'N' flag in the PSW. If the signal interrupts a thread when the 'N' > flag is set, the flag remains set at the beginning of the signal handler > and the first instruction of the signal handler is skipped. > > Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Acked-by: Helge Deller <deller@gmx.de> Thank you! Helge > > --- > linux-user/hppa/signal.c | 1 + > 1 file changed, 1 insertion(+) > > Index: qemu/linux-user/hppa/signal.c > =================================================================== > --- qemu.orig/linux-user/hppa/signal.c > +++ qemu/linux-user/hppa/signal.c > @@ -159,6 +159,7 @@ void setup_rt_frame(int sig, struct targ > } > env->iaoq_f = haddr; > env->iaoq_b = haddr + 4; > + env->psw_n = 0; > return; > > give_sigsegv: >
On 9/16/23 18:49, Helge Deller wrote: >> The reason for the crash is that the signal handling routine doesn't clear >> the 'N' flag in the PSW. If the signal interrupts a thread when the 'N' >> flag is set, the flag remains set at the beginning of the signal handler >> and the first instruction of the signal handler is skipped. >> >> Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> > > Acked-by: Helge Deller <deller@gmx.de> FYI, I've queued by both patches in my btlb branch and added backport to stable request. Helge
Index: qemu/linux-user/hppa/signal.c =================================================================== --- qemu.orig/linux-user/hppa/signal.c +++ qemu/linux-user/hppa/signal.c @@ -159,6 +159,7 @@ void setup_rt_frame(int sig, struct targ } env->iaoq_f = haddr; env->iaoq_b = haddr + 4; + env->psw_n = 0; return; give_sigsegv:
qemu-hppa may crash when delivering a signal. It can be demonstrated with this program. Compile the program with "hppa-linux-gnu-gcc -O2 signal.c" and run it with "qemu-hppa -one-insn-per-tb a.out". It reports that the address of the flag is 0xb4 and it crashes when attempting to touch it. #include <stdio.h> #include <stdlib.h> #include <sys/time.h> #include <signal.h> sig_atomic_t flag; void sig(int n) { printf("&flag: %p\n", &flag); flag = 1; } int main(void) { struct sigaction sa; struct itimerval it; sa.sa_handler = sig; sigemptyset(&sa.sa_mask); sa.sa_flags = SA_RESTART; if (sigaction(SIGALRM, &sa, NULL)) perror("sigaction"), exit(1); it.it_interval.tv_sec = 0; it.it_interval.tv_usec = 100; it.it_value.tv_sec = it.it_interval.tv_sec; it.it_value.tv_usec = it.it_interval.tv_usec; if (setitimer(ITIMER_REAL, &it, NULL)) perror("setitimer"), exit(1); while (1) { } } The reason for the crash is that the signal handling routine doesn't clear the 'N' flag in the PSW. If the signal interrupts a thread when the 'N' flag is set, the flag remains set at the beginning of the signal handler and the first instruction of the signal handler is skipped. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> --- linux-user/hppa/signal.c | 1 + 1 file changed, 1 insertion(+)