On Fri, Sep 07, 2001 at 08:26:52PM +0900, Atsushi Nemoto wrote:
> I found that if setup_frame() fails in certain conditions the process
> which caused the signal grabs CPU and never be killed.
>
> Here is a sample test program.
>
> #include <stdio.h>
> #include <stdlib.h>
> #include <signal.h>
>
> void sighandler(int sig)
> {
> printf("SIGNAL %d!\n", sig);
> exit(2);
> }
> void setup_signal(int sig)
> {
> struct sigaction act;
> memset(&act, 0, sizeof(act));
> act.sa_handler = sighandler;
> act.sa_flags = SA_NOMASK | SA_RESTART;
> sigaction(sig, &act, 0);
> }
>
> int main(int argc, char **argv)
> {
> setup_signal(SIGILL);
> setup_signal(SIGQUIT);
> setup_signal(SIGINT);
>
> __asm__ __volatile__("move $29,$0");
> __asm__ __volatile__("mfc0 $0,$0");
> printf("done!\n");
> return 0;
> }
>
>
> This program setups signal handlers and causes Coprocessor Unusable
> Exception with $sp == 0.
>
> If we run this program,
>
> 1. "mfc1" instruction raises a exception.
> 2. The exception handler queues SIGILL(4).
> 3. do_signal() dequeue a signal with LOWEST number.
> 4. setup_frame() fails and queues SIGSEGV(11).
> 5. returns to user process.
> 6. again from 1. (forever)
>
> So, even SIGKILL can not kill the process. (SIGHUP can do it).
>
> I make a change for do_signal() to check failure of setup_frame() and
> continue processing pending signals. It seems work for me. Here is
> the patch. Any comments are welcome.
Nice test case. Thanks. I decied for a differnet fix attached below.
Ralf
Index: arch/mips64/kernel/traps.c
===================================================================
RCS file: /home/pub/cvs/linux/arch/mips64/kernel/traps.c,v
retrieving revision 1.20
diff -u -r1.20 traps.c
--- arch/mips64/kernel/traps.c 2001/07/11 23:32:54 1.20
+++ arch/mips64/kernel/traps.c 2001/09/07 23:29:16
@@ -347,11 +347,9 @@
void do_ri(struct pt_regs *regs)
{
- printk("Cpu%d[%s:%d] Illegal instruction at %08lx ra=%08lx\n",
- smp_processor_id(), current->comm, current->pid, regs->cp0_epc,
- regs->regs[31]);
if (compute_return_epc(regs))
return;
+
force_sig(SIGILL, current);
}
@@ -388,6 +386,7 @@
return;
bad_cid:
+ compute_return_epc(regs);
force_sig(SIGILL, current);
}
Index: arch/mips/kernel/traps.c
===================================================================
RCS file: /home/pub/cvs/linux/arch/mips/kernel/traps.c,v
retrieving revision 1.78
diff -u -r1.78 traps.c
--- arch/mips/kernel/traps.c 2001/09/06 13:22:24 1.78
+++ arch/mips/kernel/traps.c 2001/09/07 23:29:16
@@ -606,9 +606,6 @@
asmlinkage void do_ri(struct pt_regs *regs)
{
- unsigned int opcode;
-
- get_insn_opcode(regs, &opcode);
if (compute_return_epc(regs))
return;
@@ -659,6 +656,7 @@
return;
bad_cid:
+ compute_return_epc(regs);
force_sig(SIGILL, current);
}
