Re: rpctrace / libpager / signal preemptor

[Samuel Thibault]

Samuel Thibault, on Wed 16 Nov 2016 19:46:52 +0100, wrote:
> The attached testcase does get the faulting address.

And the attached testcase doesn't.

> I really believe the issue is related to this:

Confirmed :)

> > Note that there is a 
> > 
> >   /* XXX what if handler != action->handler (for instance, if a signal
> >    * preemptor took over) ? */
> > 
> > above.  I'd say that when handler != action->handler we should assume
> > it's a legacy handler, and make 'action' point to a default-legacy
> > sigaction structure, so that it doesn't have SA_SIGINFO, and thus the
> > legacy parameters will be passeD.
> 
> Samuel

#define _GNU_SOURCE
#include <sys/types.h>
#include <math.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <hurd.h>
#include <hurd/sigpreempt.h>

char *c = (char*) 0xa0000000;

error_t
do_copy (struct hurd_signal_preemptor *preemptor)
{
        fprintf(stderr,"copying\n");
        memcpy(c, c+1, 999999);
        fprintf(stderr,"copied\n");
        return 0;
}

int main(int argc, char *argv[]) {
        jmp_buf buf;
        void fault(int signo, long int sigcode, struct sigcontext *scp)
        {
                fprintf(stderr,"%d %lx %p\n", signo, sigcode, scp);
                longjmp(buf, 1);
        }
        void sigfault(int signo, siginfo_t *info, void *a)
        {
                fprintf(stderr,"%d %p %p\n", signo, info, a);
                longjmp(buf, 1);
        }
        struct sigaction act = {};
        act.sa_sigaction = sigfault;
        act.sa_flags = SA_SIGINFO;
        sigaction(SIGSEGV, &act, NULL);
        if (setjmp(buf) == 0) {
                hurd_catch_signal(sigmask(SIGSEGV) | sigmask(SIGBUS),
                                (unsigned long) c, (unsigned long) c+1000000,
                        &do_copy, (sighandler_t) &fault);
        }
        fprintf(stderr,"done\n");
        return 0;
}