none/tests/linux/pthread-stack.c

/* This test causes an error in 3.10.1 and earlier versions like so:

==8336== Can't extend stack to 0x4033f98 during signal delivery for thread 2:
==8336==   no stack segment

  The reason was that only AnonC segments were considered as stack
  segments. */
 
#include <sys/mman.h>
#include <sys/stat.h>
#include <stdio.h>
#include <pthread.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>
#include <setjmp.h>
#include <signal.h>
#include <fcntl.h>
#include <unistd.h>

static volatile char *lowest_j;
static jmp_buf goback;

static void sigsegv_handler(int signr)
{
   longjmp(goback, 1);
}

static void bad_things_till_guard_page(void)
{
   fprintf(stderr, "... doing bad things till guard page\n");
   char j = 0;
   char *p = &j;

   for (;;) {
      j = j + *p;
      p = p - 400;
      lowest_j = p;
   }
}

static void say_something(void)
{
  fprintf(stderr, "plugh\n");
}

static void* child_func ( void* arg )
{
   if (setjmp(goback)) {
      say_something();
   } else
      bad_things_till_guard_page();

   return NULL;
}

int main(int argc, const char** argv)
{
   int r, fd;

   /* We will discover the thread guard page using SEGV.
      So, prepare an handler. */
   struct sigaction sa;
   sa.sa_handler = sigsegv_handler;
   sigemptyset(&sa.sa_mask);
   sa.sa_flags = 0;
   if (sigaction (SIGSEGV, &sa, NULL) != 0)
      perror("sigaction");

   pthread_t child;

   /* Create a file that will be used as stack for a pthread.  */
   const size_t file_size = 1024 * 1024;
   const char file_name[] = "FILE";
   fd = open(file_name, O_CREAT|O_WRONLY, 
             S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH|S_IWOTH);
   assert(fd > 0);
   void *p = malloc(file_size);
   assert(p != 0);
   memset(p, 0, file_size);
   int written = write(fd, p, file_size);
   assert(written == file_size);
   close(fd);

   /* Create a file-based stack for the child */
   fd = open(file_name, O_CREAT|O_RDWR, 
             S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH|S_IWOTH);
   assert(fd > 0);
   const size_t stack_size = 256 * 1024;
   assert(stack_size < file_size);
   void *stack = mmap(NULL, stack_size, PROT_READ|PROT_WRITE, 
                      MAP_PRIVATE, fd, 0);
   assert(stack != (void *)-1);
   pthread_attr_t attr;
   pthread_attr_init(&attr);
   r = pthread_attr_setstack(&attr, stack, stack_size);
   assert(r == 0);
   
   /* Create child run */
   r = pthread_create(&child, &attr, child_func, NULL);
   assert(r == 0);
   r = pthread_join(child, NULL);
   assert(r == 0);

   /* Remove file */
   unlink(file_name);
   return 0;
}