[Stable-8.1.2 09/45] linux-user/hppa: clear the PSW 'N' bit when delivering signals

[Michael Tokarev]

From: Mikulas Patocka <mpatocka@redhat.com>

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>
Cc: qemu-stable@nongnu.org
Signed-off-by: Helge Deller <deller@gmx.de>
(cherry picked from commit 2529497cb6b298e732e8dbe5212da7925240b4f4)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

diff --git a/linux-user/hppa/signal.c b/linux-user/hppa/signal.c
index f253a15864..3a976ac693 100644
--- a/linux-user/hppa/signal.c
+++ b/linux-user/hppa/signal.c
@@ -159,6 +159,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
     }
     env->iaoq_f = haddr;
     env->iaoq_b = haddr + 4;
+    env->psw_n = 0;
     return;
 
  give_sigsegv:
-- 
2.39.2