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#include <sys/types.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <signal.h>
#include <stdio.h>
char *stack; /* pointer to signal stack base */
int tooksig = 0; /* 1 after we take the signal */
main()
{
extern void x();
struct sigvec sv;
struct sigstack ss;
struct rlimit rlimit;
/*
* Set stack size limit to 50 kbytes.
*/
getrlimit(RLIMIT_STACK, &rlimit);
rlimit.rlim_cur = 50 * 1024;
if (setrlimit(RLIMIT_STACK, &rlimit) < 0) {
perror("setrlimit");
exit(1);
}
/*
* Take illegal instruction and process it with x,
* on the interrupt stack. For 4.2BSD, change
* sv_flags to sv_onstack and SV_ONSTACK to 1.
*/
sv.sv_mask = 0;
sv.sv_handler = x;
sv.sv_flags = SV_ONSTACK;
sigvec(SIGILL, &sv, (struct sigvec *) 0);
/*
* Allocate memory for the signal stack. The
* kernel assumes the addresses grow in the same
* direction as on the process stack (toward
* lower addresses, on a VAX).
*/
if ((stack = (char *) malloc(10240)) == NULL) {
fprintf(stderr, "Out of memory.\n");
exit(1);
}
/*
* Issue the call to tell the system about the
* signal stack. We pass the end of the signal
* stack, not the beginning, since the stack
* grows toward lower addresses.
*/
ss.ss_onstack = 0;
ss.ss_sp = (caddr_t) stack + 10240;
if (sigstack(&ss, (struct sigstack *) 0) < 0) {
perror("sigstack");
exit(1);
}
/*
* Start using up stack space.
*/
y();
}
y()
{
/*
* Take up 5k of stack space.
*/
char buf[5120];
printf("%s\n", tooksig ? "Now on extended stack." :
"On 50k stack.");
/*
* Recurse.
*/
y();
}
/*
* Handle the signal.
*/
void x(sig, code, scp)
int sig, code;
struct sigcontext *scp;
{
struct rlimit rlimit;
/*
* Increase the stack limit to the maximum.
*/
getrlimit(RLIMIT_STACK, &rlimit);
rlimit.rlim_cur = rlimit.rlim_max;
if (setrlimit(RLIMIT_STACK, &rlimit) < 0) {
perror("setrlimit");
exit(1);
}
tooksig = 1;
return;
}
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