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

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

[jekacur]

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

[Roman Zippel]

Hi,

On Thu, 25 Jan 2001 jekacur@ca.ibm.com wrote:

>
> 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 */
> }

Please ignore the last patch!
Anyway, in the code example the last argument is not a sigcontext
structure but an ucontext_t structure, which is defined in <ucontext.h>.

bye, Roman


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

[Kevin B. Hendricks]

Hi,

> Please ignore the last patch!
> Anyway, in the code example the last argument is not a sigcontext
> structure but an ucontext_t structure, which is defined in <ucontext.h>.

Yes.

Here is the revised sample program and it works:

[root@localhost kbhend]# ./junk
SIGUSR1 = 10
uc = 7ffff794
uc->uc_mcontext.signal = 10
[root@localhost kbhend]# cat junk.c
#include <stdio.h>
#include <signal.h>
#include <ucontext.h>

/* Function Prototypes */
void install_sigusr1_handler(void);
void sigusr_handler(int , siginfo_t *, struct ucontext * uc);

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 ucontext * uc)
{
  printf("uc = %08x\n", uc);
  printf("uc->uc_mcontext.signal = %d\n", uc->uc_mcontext.signal);
}

[[root@localhost kbhend]# cat junk.c
#include <stdio.h>
#include <signal.h>
#include <ucontext.h>

/* Function Prototypes */
void install_sigusr1_handler(void);
void sigusr_handler(int , siginfo_t *, struct ucontext * uc);

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 ucontext * uc)
{
  printf("uc = %08x\n", uc);
  printf("uc->uc_mcontext.signal = %d\n", uc->uc_mcontext.signal);
}



[root@localhost kbhend]# ./junk
SIGUSR1 = 10
uc = 7ffff794
uc->uc_mcontext.signal = 10

So no patch needed.

Thanks for finding that.

Kevin

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