#include <stdio.h>
#include <ctype.h>

#define NBR_OF_BYTES 52

#define PRTSTK(fp) {\
  printf("%04.4lx ", (long)fp);\
  printf("%02x ", (unsigned char)*(fp));\
  printf("%c\n", isprint((unsigned char)*(fp))\
	? (unsigned char)*(fp) : ' ');\
}

fcn1b()
{
	unsigned char stk_top;
	static unsigned char *s;
	stk_top = 0xff;
	for (s = &stk_top + NBR_OF_BYTES; s >= &stk_top; --s)
		PRTSTK(s);
}

fcn1(a, b, c)
int a, b, c;
{
	int j;
	char s[7];
	j = 5;
	strcpy(s, "123456");
	fcn1b();
}

main()
{
	int i;
	i = 1;
	fcn1(2, 3, 4);
}
7ffffeef 00  
7ffffeee 00  
7ffffeed 00  
7ffffeec f6  
7ffffeeb 7f  
7ffffeea ff  
7ffffee9 fe  
7ffffee8 fc  
7ffffee7 00  
7ffffee6 00  
7ffffee5 00  
7ffffee4 01  
7ffffee3 00  
7ffffee2 00  
7ffffee1 00  
7ffffee0 04  
7ffffedf 00  
7ffffede 00  
7ffffedd 00  
7ffffedc 03  
7ffffedb 00  
7ffffeda 00  
7ffffed9 00  
7ffffed8 02  
7ffffed7 00  
7ffffed6 00  
7ffffed5 01  
7ffffed4 f3  
7ffffed3 7f  
7ffffed2 ff  
7ffffed1 fe  
7ffffed0 e8  
7ffffecf 00  
7ffffece 00  
7ffffecd 00  
7ffffecc 05  
7ffffecb 00  
7ffffeca 36 6
7ffffec9 35 5
7ffffec8 34 4
7ffffec7 33 3
7ffffec6 32 2
7ffffec5 31 1
7ffffec4 00  
7ffffec3 00  
7ffffec2 00  
7ffffec1 01  
7ffffec0 ce  
7ffffebf 7f      
7ffffebe ff  
7ffffebd fe  
7ffffebc d0  
7ffffebb ff     
/* badstk.c - writes data incorrectly into an automatic
   variable */

fcn2()
{
	char s[3];
	/* about to write over frame pointer and return address */
	strcpy(s, "1234567");
}

fcn()
{
	int x;
	x = 1;
	fcn2();
}

main()
{
	char a;
	a = '~';
	fcn();
	exit(0);
}
/* badstk.c - writes data incorrectly into an automatic
   variable */
#include "chkstk.h"

fcn2()
{
	char s[3];
	CHKSTK;
	/* about to write over frame pointer and return address */
	strcpy(s, "1234567");
	CHKSTK;
}

fcn()
{
	int x;
	CHKSTK;
	x = 1;
	fcn2();
	CHKSTK;
}

main()
{
	char a;
	CHKSTKINIT;
	a = '~';
	fcn();
	CHKSTK;
	exit(0);
}
Error: Stack is corrupted (badstk.c, 11)
7ffffecf 37 7 
7ffffece 36 6 
7ffffecd 35 5 
7ffffecc 34 4 <= Corrupted frame pointer
7ffffecb 33 3 
7ffffeca 32 2 
7ffffec9 31 1 
7ffffec8 f8   
7ffffec7 00   
7ffffec6 00   
7ffffec5 00   
7ffffec4 0b   
7ffffec3 00   
7ffffec2 40 @ 
7ffffec1 03   
7ffffec0 a5   
7ffffebf 00   
7ffffebe 00   
7ffffebd 01   
7ffffebc 41 A 
7ffffebb 7f   
7ffffeba ff   
7ffffeb9 fe   
7ffffeb8 cc   
7ffffeb7 ff   
7ffffeb6 ff   
7ffffeb5 fe   
7ffffeb4 c9   
7ffffeb3 7f   
7ffffeb2 ff   
7ffffeb1 fe   
7ffffeb0 cc   
7ffffeaf 00   
7ffffeae 00   
7ffffead 02   
7ffffeac ec   
7ffffeab 7f   
7ffffeaa ff   
7ffffea9 fe   
7ffffea8 b8   
7ffffea7 ff   <= stack top
/* interface to the chkstk module */

/*
Instructions:
-   Put CHKSTKINIT immediatly after declaring local variables
	in main()
-   Put CHKSTK anywhere you wish to have the integrity of
	the stack checked
*/

#define CHKSTKINIT \
	unsigned char no_conflict; \
	no_conflict = 0xaa; \
	chkstkinit();
/*
	For these functions to work with Microsoft compilers,
	main() must have at least one automatic variable,
	so we need the variable no_conflict in the macro 
	definition.
*/
#define CHKSTK chkstk(__FILE__, __LINE__);

void chkstkinit();
void chkstk();
#include <stdio.h>
#include <ctype.h>
#include "chkstk.h"

/* NCR UNIX on NCR tower */
#if defined(tower)
#define OFFSET 4
#define NEXTFP(nextfp, fp) \
  nextfp = *fp * 0x1000000 + *(fp + 1) * 0x10000 + \
  *(fp + 2) * 0x100 + *(fp + 3);
#endif

/* XENIX and UNIX 80386 */
#if defined(M_I386) | defined(i386)
#define OFFSET 1
#define NEXTFP(nextfp, fp) \
  nextfp = *fp + *(fp + 1) * 0x100 + \
  *(fp + 2) * 0x10000 + *(fp + 3) * 0x1000000;
#endif

/* Microsoft C 5.10, Quick C, SCO Xenix */
/* Huge, Large or Code models */
#if defined(M_I86LM) | defined(M_I86HM) | defined(M_I86CM)
#define OFFSET 2
#define NEXTFP(nextfp, fp) \
  nextfp = (long)fp & 0xffff0000;\
  nextfp = nextfp + *fp + *(fp + 1) * 0x100;
#endif

/* Microsoft C 5.10, Quick C, SCO Xenix */
/* Middle or Small models */
#if defined(M_I86MM) | defined(M_I86SM)
#define OFFSET 2
#define NEXTFP(nextfp, fp) \
  nextfp = *fp + *(fp + 1) * 0x100;
#endif

#define PRTSTK(fp, q) {\
  trace("%04.4lx ", (long)fp);\
  trace("%02x ", (unsigned char)*(fp));\
  trace("%c", isprint((unsigned char)*(fp))\
	 ? (unsigned char)*(fp) : ' ');\
  trace(" %s\n", q);\
}

static unsigned char *stk_bottom;
static long first_fp;
static void dumpstk();
static void trace();

void chkstkinit()
{
	unsigned char stk_top;
	static long nextfp;
	static unsigned char *fp;
	stk_top = 0xaa;
	fp = &stk_top + OFFSET;
	NEXTFP(nextfp, fp);
	stk_bottom = (unsigned char *)nextfp;
	first_fp = *stk_bottom + *(stk_bottom + 1) * 0x100;
}

void chkstk(file, line)
char *file;
int line;
{
	unsigned char stk_top;
	static unsigned char *fp;
	static long nextfp;
	stk_top = 0xff;
	fp = &stk_top + OFFSET;
	while (fp != stk_bottom) {
		NEXTFP(nextfp, fp);
		if ((unsigned char *)nextfp < fp ||
			 (unsigned char *)nextfp > stk_bottom) {
			trace("Error: Stack is corrupted (%s, %d)\n",
			  file, line);
			fprintf(stderr, "Error: Stack is corrupted (%s, %d)\n",
			  file, line);
			dumpstk(fp);
			exit(1);
		}
		fp = (unsigned char *)nextfp;
	}
	if ((*fp + *(fp + 1) * 0x100) != first_fp) {
		trace("Error: stack corrupted (%s, %d)\n",
		  file, line);
		fprintf(stderr, "Error: Stack is corrupted (%s, %d)\n",
		  file, line);
		dumpstk(fp);
		exit(1);
	}
}

static void dumpstk(bfp)
unsigned char *bfp;
{
	unsigned char stk_top;
	static unsigned char *fp, *x;
	static long nextfp;
	stk_top = 0xff;
	PRTSTK(bfp + 3, "");
	PRTSTK(bfp + 2, "");
	PRTSTK(bfp + 1, "");
	PRTSTK(bfp, "<= Corrupted frame pointer");
	fp = bfp - 1;
	while (fp != &stk_top) {
		PRTSTK(fp, "");
		--fp;
	}
	PRTSTK(fp, "<= stack top");
}

static void trace(f, a1, a2, a3, a4, a5, a6, a7, a8, a9)
char *f, *a1, *a2, *a3, *a4, *a5, *a6, *a7, *a8, *a9;
{
	static FILE *out = NULL;
	if (out == NULL) {
		unlink("chkstk");
		out = fopen("chkstk", "w");
		setbuf(out, NULL);
	}
	fprintf(out, f, a1, a2, a3, a4, a5, a6, a7, a8, a9);
}