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first version of bounds checker

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bellard 2002-01-03 23:12:29 +00:00
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/*
* Tiny C Memory and bounds checker
*
* Copyright (c) 2002 Fabrice Bellard
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
//#define BOUND_DEBUG
/* define so that bound array is static (faster, but use memory if
bound checking not used) */
//#define BOUND_STATIC
#define BOUND_T1_BITS 13
#define BOUND_T2_BITS 11
#define BOUND_T3_BITS (32 - BOUND_T1_BITS - BOUND_T2_BITS)
#define BOUND_T1_SIZE (1 << BOUND_T1_BITS)
#define BOUND_T2_SIZE (1 << BOUND_T2_BITS)
#define BOUND_T3_SIZE (1 << BOUND_T3_BITS)
#define BOUND_E_BITS 4
#define BOUND_T23_BITS (BOUND_T2_BITS + BOUND_T3_BITS)
#define BOUND_T23_SIZE (1 << BOUND_T23_BITS)
/* this pointer is generated when bound check is incorrect */
#define INVALID_POINTER ((void *)(-2))
/* size of an empty region */
#define EMPTY_SIZE 0xffffffff
/* size of an invalid region */
#define INVALID_SIZE 0
typedef struct BoundEntry {
unsigned long start;
unsigned long size;
struct BoundEntry *next;
unsigned long is_invalid; /* true if pointers outside region are invalid */
} BoundEntry;
/* external interface */
void __bound_init(void);
void __bound_new_region(void *p, unsigned long size);
void __bound_delete_region(void *p);
void *__bound_ptr_add(void *p, int offset) __attribute__((regparm(2)));
char __bound_ptr_indir_b(void *p, int offset) __attribute__((regparm(2)));
unsigned char __bound_ptr_indir_ub(void *p, int offset) __attribute__((regparm(2)));
short __bound_ptr_indir_w(void *p, int offset) __attribute__((regparm(2)));
unsigned short __bound_ptr_indir_uw(void *p, int offset) __attribute__((regparm(2)));
int __bound_ptr_indir_i(void *p, int offset) __attribute((regparm(2)));
void *__bound_calloc(size_t nmemb, size_t size);
void *__bound_malloc(size_t size);
void __bound_free(void *ptr);
void *__bound_realloc(void *ptr, size_t size);
extern char _end;
#ifdef BOUND_STATIC
static BoundEntry *__bound_t1[BOUND_T1_SIZE]; /* page table */
#else
static BoundEntry **__bound_t1; /* page table */
#endif
static BoundEntry *__bound_empty_t2; /* empty page, for unused pages */
static BoundEntry *__bound_invalid_t2; /* invalid page, for invalid pointers */
static BoundEntry *__bound_find_region(BoundEntry *e1, void *p)
{
unsigned long addr, tmp;
BoundEntry *e;
e = e1;
while (e != NULL) {
addr = (unsigned long)p;
addr -= e->start;
if (addr <= e->size) {
/* put region at the head */
tmp = e1->start;
e1->start = e->start;
e->start = tmp;
tmp = e1->size;
e1->size = e->size;
e->size = tmp;
return e1;
}
e = e->next;
}
/* no entry found: return empty entry or invalid entry */
if (e1->is_invalid)
return __bound_invalid_t2;
else
return __bound_empty_t2;
}
static void bound_error(const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
fprintf(stderr, "bounds check: ");
vfprintf(stderr, fmt, ap);
fprintf(stderr, "\n");
exit(1);
va_end(ap);
}
static void bound_alloc_error(void)
{
bound_error("not enough memory for bound checking code\n");
}
/* do: return (p + offset); */
void *__bound_ptr_add(void *p, int offset)
{
unsigned long addr = (unsigned long)p;
BoundEntry *e;
#ifdef BOUND_DEBUG
printf("add: 0x%x %d\n", (int)p, offset);
#endif
e = __bound_t1[addr >> (BOUND_T2_BITS + BOUND_T3_BITS)];
e = (BoundEntry *)((char *)e +
((addr >> (BOUND_T3_BITS - BOUND_E_BITS)) &
((BOUND_T2_SIZE - 1) << BOUND_E_BITS)));
addr -= e->start;
if (addr > e->size) {
e = __bound_find_region(e, p);
addr = (unsigned long)p - e->start;
}
addr += offset;
if (addr > e->size)
return INVALID_POINTER; /* return an invalid pointer */
return p + offset;
}
/* do: return *(type *)(p + offset); */
#define BOUND_PTR_INDIR(suffix, type) \
type __bound_ptr_indir_ ## suffix (void *p, int offset) \
{ \
unsigned long addr = (unsigned long)p; \
BoundEntry *e; \
\
e = __bound_t1[addr >> (BOUND_T2_BITS + BOUND_T3_BITS)]; \
e = (BoundEntry *)((char *)e + \
((addr >> (BOUND_T3_BITS - BOUND_E_BITS)) & \
((BOUND_T2_SIZE - 1) << BOUND_E_BITS))); \
addr -= e->start; \
if (addr > e->size) { \
e = __bound_find_region(e, p); \
addr = (unsigned long)p - e->start; \
} \
addr += offset + sizeof(type); \
if (addr > e->size) \
bound_error("dereferencing invalid pointer"); \
return *(type *)(p + offset); \
}
BOUND_PTR_INDIR(b, char)
BOUND_PTR_INDIR(ub, unsigned char)
BOUND_PTR_INDIR(w, short)
BOUND_PTR_INDIR(uw, unsigned short)
BOUND_PTR_INDIR(i, int)
static BoundEntry *__bound_new_page(void)
{
BoundEntry *page;
int i;
page = malloc(sizeof(BoundEntry) * BOUND_T2_SIZE);
if (!page)
bound_alloc_error();
for(i=0;i<BOUND_T2_SIZE;i++) {
/* put empty entries */
page[i].start = 0;
page[i].size = EMPTY_SIZE;
page[i].next = NULL;
page[i].is_invalid = 0;
}
return page;
}
/* currently we use malloc(). Should use bound_new_page() */
static BoundEntry *bound_new_entry(void)
{
BoundEntry *e;
e = malloc(sizeof(BoundEntry));
return e;
}
static void bound_free_entry(BoundEntry *e)
{
free(e);
}
static inline BoundEntry *get_page(int index)
{
BoundEntry *page;
page = __bound_t1[index];
if (page == __bound_empty_t2 || page == __bound_invalid_t2) {
/* create a new page if necessary */
page = __bound_new_page();
__bound_t1[index] = page;
}
return page;
}
/* mark a region as being invalid (can only be used during init) */
static void mark_invalid(unsigned long addr, unsigned long size)
{
unsigned long start, end;
BoundEntry *page;
int t1_start, t1_end, i, j, t2_start, t2_end;
start = addr;
end = addr + size;
t2_start = (start + BOUND_T3_SIZE - 1) >> BOUND_T3_BITS;
if (end != 0)
t2_end = end >> BOUND_T3_BITS;
else
t2_end = 1 << (BOUND_T1_BITS + BOUND_T2_BITS);
printf("mark_invalid: start = %x %x\n", t2_start, t2_end);
/* first we handle full pages */
t1_start = (t2_start + BOUND_T2_SIZE - 1) >> BOUND_T2_BITS;
t1_end = t2_end >> BOUND_T2_BITS;
i = t2_start & (BOUND_T2_SIZE - 1);
j = t2_end & (BOUND_T2_SIZE - 1);
if (t1_start == t1_end) {
page = get_page(t2_start >> BOUND_T2_BITS);
for(; i < j; i++) {
page[i].size = INVALID_SIZE;
page[i].is_invalid = 1;
}
} else {
if (i > 0) {
page = get_page(t2_start >> BOUND_T2_BITS);
for(; i < BOUND_T2_SIZE; i++) {
page[i].size = INVALID_SIZE;
page[i].is_invalid = 1;
}
}
for(i = t1_start; i < t1_end; i++) {
__bound_t1[i] = __bound_invalid_t2;
}
if (j != 0) {
page = get_page(t1_end);
for(i = 0; i < j; i++) {
page[i].size = INVALID_SIZE;
page[i].is_invalid = 1;
}
}
}
}
void __bound_init(void)
{
int i;
BoundEntry *page;
unsigned long start, size;
#ifndef BOUND_STATIC
__bound_t1 = malloc(BOUND_T1_SIZE * sizeof(BoundEntry *));
if (!__bound_t1)
bound_alloc_error();
#endif
__bound_empty_t2 = __bound_new_page();
for(i=0;i<BOUND_T1_SIZE;i++) {
__bound_t1[i] = __bound_empty_t2;
}
page = __bound_new_page();
for(i=0;i<BOUND_T2_SIZE;i++) {
/* put invalid entries */
page[i].start = 0;
page[i].size = INVALID_SIZE;
page[i].next = NULL;
page[i].is_invalid = 1;
}
__bound_invalid_t2 = page;
/* invalid pointer zone */
start = (unsigned long)INVALID_POINTER & ~(BOUND_T23_SIZE - 1);
size = BOUND_T23_SIZE;
mark_invalid(start, size);
/* malloc zone is also marked invalid */
start = (unsigned long)&_end;
size = 128 * 0x100000;
mark_invalid(start, size);
}
static inline void add_region(BoundEntry *e,
unsigned long start, unsigned long size)
{
BoundEntry *e1;
if (e->start == 0) {
/* no region : add it */
e->start = start;
e->size = size;
} else {
/* already regions in the list: add it at the head */
e1 = bound_new_entry();
e1->start = e->start;
e1->size = e->size;
e1->next = e->next;
e->start = start;
e->size = size;
e->next = e1;
}
}
/* create a new region. It should not already exist in the region list */
void __bound_new_region(void *p, unsigned long size)
{
unsigned long start, end;
BoundEntry *page, *e, *e2;
int t1_start, t1_end, i, t2_start, t2_end;
start = (unsigned long)p;
end = start + size;
t1_start = start >> (BOUND_T2_BITS + BOUND_T3_BITS);
t1_end = end >> (BOUND_T2_BITS + BOUND_T3_BITS);
/* start */
page = get_page(t1_start);
t2_start = (start >> (BOUND_T3_BITS - BOUND_E_BITS)) &
((BOUND_T2_SIZE - 1) << BOUND_E_BITS);
t2_end = (end >> (BOUND_T3_BITS - BOUND_E_BITS)) &
((BOUND_T2_SIZE - 1) << BOUND_E_BITS);
#ifdef BOUND_DEBUG
printf("new %lx %lx %x %x %x %x\n",
start, end, t1_start, t1_end, t2_start, t2_end);
#endif
e = (BoundEntry *)((char *)page + t2_start);
add_region(e, start, size);
if (t1_end == t1_start) {
/* same ending page */
e2 = (BoundEntry *)((char *)page + t2_end);
if (e2 > e) {
e++;
for(;e<e2;e++) {
e->start = start;
e->size = size;
}
add_region(e, start, size);
}
} else {
/* mark until end of page */
e2 = page + BOUND_T2_SIZE;
e++;
for(;e<e2;e++) {
e->start = start;
e->size = size;
}
/* mark intermediate pages, if any */
for(i=t1_start+1;i<t1_end;i++) {
page = get_page(i);
e2 = page + BOUND_T2_SIZE;
for(e=page;e<e2;e++) {
e->start = start;
e->size = size;
}
}
/* last page */
page = get_page(t2_end);
e2 = (BoundEntry *)((char *)page + t2_end);
for(e=page;e<e2;e++) {
e->start = start;
e->size = size;
}
add_region(e, start, size);
}
}
/* delete a region */
static inline void delete_region(BoundEntry *e,
void *p, unsigned long empty_size)
{
unsigned long addr;
BoundEntry *e1;
addr = (unsigned long)p;
addr -= e->start;
if (addr <= e->size) {
/* region found is first one */
e1 = e->next;
if (e1 == NULL) {
/* no more region: mark it empty */
e->start = 0;
e->size = empty_size;
} else {
/* copy next region in head */
e->start = e1->start;
e->size = e1->size;
e->next = e1->next;
bound_free_entry(e1);
}
} else {
/* find the matching region */
for(;;) {
e1 = e;
e = e->next;
/* region not found: do nothing */
if (e == NULL)
break;
addr = (unsigned long)p - e->start;
if (addr <= e->size) {
/* found: remove entry */
e1->next = e->next;
bound_free_entry(e);
break;
}
}
}
}
/* WARNING: 'p' must be the starting point of the region. */
void __bound_delete_region(void *p)
{
unsigned long start, end, addr, size, empty_size;
BoundEntry *page, *e, *e2;
int t1_start, t1_end, t2_start, t2_end, i;
start = (unsigned long)p;
t1_start = start >> (BOUND_T2_BITS + BOUND_T3_BITS);
t2_start = (start >> (BOUND_T3_BITS - BOUND_E_BITS)) &
((BOUND_T2_SIZE - 1) << BOUND_E_BITS);
/* find region size */
page = __bound_t1[t1_start];
e = (BoundEntry *)((char *)page + t2_start);
addr = start - e->start;
if (addr > e->size)
e = __bound_find_region(e, p);
/* test if invalid region */
if (e->size == EMPTY_SIZE || (unsigned long)p != e->start)
bound_error("deleting invalid region");
/* compute the size we put in invalid regions */
if (e->is_invalid)
empty_size = INVALID_SIZE;
else
empty_size = EMPTY_SIZE;
size = e->size;
end = start + size;
/* now we can free each entry */
t1_end = end >> (BOUND_T2_BITS + BOUND_T3_BITS);
t2_end = (end >> (BOUND_T3_BITS - BOUND_E_BITS)) &
((BOUND_T2_SIZE - 1) << BOUND_E_BITS);
delete_region(e, p, empty_size);
if (t1_end == t1_start) {
/* same ending page */
e2 = (BoundEntry *)((char *)page + t2_end);
if (e2 > e) {
e++;
for(;e<e2;e++) {
e->start = 0;
e->size = empty_size;
}
delete_region(e, p, empty_size);
}
} else {
/* mark until end of page */
e2 = page + BOUND_T2_SIZE;
e++;
for(;e<e2;e++) {
e->start = 0;
e->size = empty_size;
}
/* mark intermediate pages, if any */
/* XXX: should free them */
for(i=t1_start+1;i<t1_end;i++) {
page = get_page(i);
e2 = page + BOUND_T2_SIZE;
for(e=page;e<e2;e++) {
e->start = 0;
e->size = empty_size;
}
}
/* last page */
page = get_page(t2_end);
e2 = (BoundEntry *)((char *)page + t2_end);
for(e=page;e<e2;e++) {
e->start = 0;
e->size = empty_size;
}
delete_region(e, p, empty_size);
}
}
/* return the size of the region starting at p, or EMPTY_SIZE if non
existant region. */
static unsigned long get_region_size(void *p)
{
unsigned long addr = (unsigned long)p;
BoundEntry *e;
e = __bound_t1[addr >> (BOUND_T2_BITS + BOUND_T3_BITS)];
e = (BoundEntry *)((char *)e +
((addr >> (BOUND_T3_BITS - BOUND_E_BITS)) &
((BOUND_T2_SIZE - 1) << BOUND_E_BITS)));
addr -= e->start;
if (addr > e->size)
e = __bound_find_region(e, p);
if (e->start != (unsigned long)p)
return EMPTY_SIZE;
return e->size;
}
/* patched memory functions */
/* XXX: we should use a malloc which ensure that it is unlikely that
two malloc'ed data have the same address if 'free' are made in
between. */
void *__bound_malloc(size_t size)
{
void *ptr;
/* we allocate one more byte to ensure the regions will be
separated by at least one byte. With the glibc malloc, it may
be in fact not necessary */
ptr = malloc(size + 1);
if (!ptr)
return NULL;
__bound_new_region(ptr, size);
return ptr;
}
void __bound_free(void *ptr)
{
if (ptr == NULL)
return;
__bound_delete_region(ptr);
free(ptr);
}
void *__bound_realloc(void *ptr, size_t size)
{
void *ptr1;
int old_size;
if (size == 0) {
__bound_free(ptr);
return NULL;
} else {
ptr1 = __bound_malloc(size);
if (ptr == NULL || ptr1 == NULL)
return ptr1;
old_size = get_region_size(ptr);
if (old_size == EMPTY_SIZE)
bound_error("realloc'ing invalid pointer");
memcpy(ptr1, ptr, old_size);
__bound_free(ptr);
return ptr1;
}
}
void *__bound_calloc(size_t nmemb, size_t size)
{
void *ptr;
size = size * nmemb;
ptr = __bound_malloc(size);
if (!ptr)
return NULL;
memset(ptr, 0, size);
return ptr;
}
#if 0
static void bound_dump(void)
{
BoundEntry *page, *e;
int i, j;
printf("region dump:\n");
for(i=0;i<BOUND_T1_SIZE;i++) {
page = __bound_t1[i];
for(j=0;j<BOUND_T2_SIZE;j++) {
e = page + j;
/* do not print invalid or empty entries */
if (e->size != EMPTY_SIZE && e->start != 0) {
printf("%08x:",
(i << (BOUND_T2_BITS + BOUND_T3_BITS)) +
(j << BOUND_T3_BITS));
do {
printf(" %08lx:%08lx", e->start, e->start + e->size);
e = e->next;
} while (e != NULL);
printf("\n");
}
}
}
}
#endif