Function redzone_check

freebsd/vm/redzone.c:129–184

* Verify redzones. * This function is called on free() and realloc(). */

 * This function is called on free() and realloc().
 */
void
redzone_check(caddr_t naddr)
{
	struct stack ast, fst;
	caddr_t haddr, faddr;
	u_int ncorruptions;
	u_long nsize;
	int i;

	haddr = naddr - REDZONE_HSIZE;
	bcopy(haddr, &ast, sizeof(ast));
	haddr += sizeof(ast);
	bcopy(haddr, &nsize, sizeof(nsize));
	haddr += sizeof(nsize);

	atomic_subtract_long(&redzone_extra_mem,
	    redzone_size_ntor(nsize) - nsize);

	/* Look for buffer underflow. */
	ncorruptions = 0;
	for (i = 0; i < REDZONE_CHSIZE; i++, haddr++) {
		if (*(u_char *)haddr != 0x42)
			ncorruptions++;
	}
	if (ncorruptions > 0) {
		printf("REDZONE: Buffer underflow detected. %u byte%s "
		    "corrupted before %p (%lu bytes allocated).\n",
		    ncorruptions, ncorruptions == 1 ? "" : "s", naddr, nsize);
		printf("Allocation backtrace:\n");
		stack_print_ddb(&ast);
		printf("Free backtrace:\n");
		stack_save(&fst);
		stack_print_ddb(&fst);
		if (redzone_panic)
			panic("Stopping here.");
	}
	faddr = naddr + nsize;
	/* Look for buffer overflow. */
	ncorruptions = 0;
	for (i = 0; i < REDZONE_CFSIZE; i++, faddr++) {
		if (*(u_char *)faddr != 0x42)
			ncorruptions++;
	}
	if (ncorruptions > 0) {
		printf("REDZONE: Buffer overflow detected. %u byte%s corrupted "
		    "after %p (%lu bytes allocated).\n", ncorruptions,
		    ncorruptions == 1 ? "" : "s", naddr + nsize, nsize);
		printf("Allocation backtrace:\n");
		stack_print_ddb(&ast);
		printf("Free backtrace:\n");
		stack_save(&fst);
		stack_print_ddb(&fst);
		if (redzone_panic)
			panic("Stopping here.");
	}
}