Re:sigcontext on Linux-ppc in user space, another hack.

jekacur@ca.ibm.com
Thu, 25 Jan 2001 15:31:38 -0500


It appears you can just use the siginfo_t * as the struct sigcontext *
!!!!!!
ie
void *signal_handler(int signo, siginfo_t *siginfoptr, struct sigcontext
*scp)
{
scp = (struct sigcontext_struct *)siginfoptr;
/* the rest of your code, here */
}

John Kacur/Toronto/IBM@IBMCA
jekacur@ca.ibm.com
(416) 448-2584 (phone)
778-2584 (tie line)

"Kevin B. Hendricks" <khendricks@ivey.uwo.ca> on 01/25/2001 02:02:20 PM

Please respond to khendricks@ivey.uwo.ca

To: John Kacur/Toronto/IBM@IBMCA
cc:
Subject: Re: [Fwd: sigcontext on Linux-ppc in user space]

Hi,

Just in case this helps, here is what I did to accomplish the same thing
in the green_threads jdk. It definitely is not portable.

Kevin

Inside the signal handler:

#elif defined(__linux__) && defined(__powerpc__)
/* get the value of r1 (the stack pointer) */
long * p;
struct sigcontext_struct * scp;
__asm__ ( "addi %0,1,0" : "=r" (p) : /* no inputs */ );
/* follow it back up the chain */
p = *p;
/* from here the sigcontext struct is 64 bytes away */
p = p + 16;
scp = (struct sigcontext_struct *)p;

On Thursday, January 25, 2001, at 01:50 PM, jekacur@ca.ibm.com wrote:

>
> Ok, actually the segfault was for a more complicated function, but the
> simplified example still gives the wrong answer. i.e scp should point to
a
> struct sigcontext and scp->signal should be 10 in the sample program.
>
> John Kacur/Toronto/IBM@IBMCA
> jekacur@ca.ibm.com
> (416) 448-2584 (phone)
> 778-2584 (tie line)
>
>
> "Kevin B. Hendricks" <khendricks@ivey.uwo.ca> on 01/25/2001 01:10:40 PM
>
> Please respond to khendricks@ivey.uwo.ca
>
> To: John Kacur/Toronto/IBM@IBMCA
> cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.linuxppc.org
> Subject: Re: [Fwd: sigcontext on Linux-ppc in user space]
>
>
> Hi,
>
> Here is what I get from running it on my system (ppc linux with 2.2.15
> kernel with some mods and glibc-2.1.3).
>
> But no segfault.
>
> Kevin
>
>
> [kbhend@localhost ~]$ gcc -O2 -ojunk junk.c
> [kbhend@localhost ~]$ ./junk
> SIGUSR1 = 10
> scp = 7fffe9a4
> scp->signal = 0
> [kbhend@localhost ~]$
>
>
>
>
> On Thursday, January 25, 2001, at 10:09 AM, jekacur@ca.ibm.com wrote:
>
> > #include <stdio.h>
> > #include <signal.h>
> >
> > /* Function Prototypes */
> > void install_sigusr1_handler(void);
> > void sigusr_handler(int , siginfo_t *, struct sigcontext * scp);
> >
> > int main(void)
> > {
> > install_sigusr1_handler();
> > printf("SIGUSR1 = %d\n", SIGUSR1);
> > raise(SIGUSR1);
> > exit(0);
> > }
> >
> > void install_sigusr1_handler(void)
> > {
> > struct sigaction newAct;
> >
> > if (sigemptyset(&newAct.sa_mask) != 0) {
> > fprintf(stderr, "Warning, sigemptyset failed.\n");
> > }
> >
> > newAct.sa_flags = 0;
> > newAct.sa_flags |= SA_SIGINFO | SA_RESTART;
> >
> > newAct.sa_sigaction = (void
> > (*)(int,siginfo_t*,void*))sigusr_handler;
> >
> > if (sigaction(SIGUSR1, &newAct, NULL) != 0) {
> > fprintf(stderr, "Couldn't install SIGUSR1 handler.\n");

> > fprintf(stderr, "Exiting.\n");
> > exit(1);
> > }
> > }
> >
> > void sigusr_handler(int signo, siginfo_t *siginfp, struct sigcontext *
> scp)
> > {
> > printf("scp = %08x\n", scp);
> > printf("scp->signal = %d\n", scp->signal);
> > }
> >
> >
>
>
>
>

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