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http://bugs.python.org/issue6836 

The debug memory api now keeps track of which external API (PyMem_* or PyObject_*) was used to allocate each block and treats any API violation as an error.  Added separate _PyMem_DebugMalloc functions for the Py_Mem API instead of having it use the _PyObject_DebugMalloc functions.
This commit is contained in:
Kristján Valur Jónsson 2009-09-28 13:12:38 +00:00
parent d12f86ce96
commit 02ca57ce4c
3 changed files with 97 additions and 20 deletions
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7
Include/objimpl.h
View File

@ -108,6 +108,13 @@ PyAPI_FUNC(void) _PyObject_DebugFree(void *p);
PyAPI_FUNC(void) _PyObject_DebugDumpAddress(const void *p);
PyAPI_FUNC(void) _PyObject_DebugCheckAddress(const void *p);
PyAPI_FUNC(void) _PyObject_DebugMallocStats(void);
PyAPI_FUNC(void *) _PyObject_DebugMallocApi(char api, size_t nbytes);
PyAPI_FUNC(void *) _PyObject_DebugReallocApi(char api, void *p, size_t nbytes);
PyAPI_FUNC(void) _PyObject_DebugFreeApi(char api, void *p);
PyAPI_FUNC(void) _PyObject_DebugCheckAddressApi(char api, const void *p);
PyAPI_FUNC(void *) _PyMem_DebugMalloc(size_t nbytes);
PyAPI_FUNC(void *) _PyMem_DebugRealloc(void *p, size_t nbytes);
PyAPI_FUNC(void) _PyMem_DebugFree(void *p);
#define PyObject_MALLOC _PyObject_DebugMalloc
#define PyObject_Malloc _PyObject_DebugMalloc
#define PyObject_REALLOC _PyObject_DebugRealloc

6
Include/pymem.h
View File

@ -59,9 +59,9 @@ PyAPI_FUNC(void) PyMem_Free(void *);
/* Macros. */
#ifdef PYMALLOC_DEBUG
/* Redirect all memory operations to Python's debugging allocator. */
#define PyMem_MALLOC PyObject_MALLOC
#define PyMem_REALLOC PyObject_REALLOC
#define PyMem_FREE PyObject_FREE
#define PyMem_MALLOC _PyMem_DebugMalloc
#define PyMem_REALLOC _PyMem_DebugRealloc
#define PyMem_FREE _PyMem_DebugFree
#else /* ! PYMALLOC_DEBUG */

104
Objects/obmalloc.c
View File

@ -1241,6 +1241,10 @@ PyObject_Free(void *p)
#define DEADBYTE 0xDB /* dead (newly freed) memory */
#define FORBIDDENBYTE 0xFB /* untouchable bytes at each end of a block */
/* We tag each block with an API ID in order to tag API violations */
#define _PYMALLOC_MEM_ID 'm' /* the PyMem_Malloc() API */
#define _PYMALLOC_OBJ_ID 'o' /* The PyObject_Malloc() API */
static size_t serialno = 0; /* incremented on each debug {m,re}alloc */
/* serialno is always incremented via calling this routine. The point is
@ -1331,8 +1335,49 @@ p[2*S+n+S: 2*S+n+2*S]
instant at which this block was passed out.
*/
/* debug replacements for the PyMem_* memory API */
void *
_PyMem_DebugMalloc(size_t nbytes)
{
return _PyObject_DebugMallocApi(_PYMALLOC_MEM_ID, nbytes);
}
void *
_PyMem_DebugRealloc(void *p, size_t nbytes)
{
return _PyObject_DebugReallocApi(_PYMALLOC_MEM_ID, p, nbytes);
}
void
_PyMem_DebugFree(void *p)
{
_PyObject_DebugFreeApi(_PYMALLOC_MEM_ID, p);
}
/* debug replacements for the PyObject_* memory API */
void *
_PyObject_DebugMalloc(size_t nbytes)
{
return _PyObject_DebugMallocApi(_PYMALLOC_OBJ_ID, nbytes);
}
void *
_PyObject_DebugRealloc(void *p, size_t nbytes)
{
return _PyObject_DebugReallocApi(_PYMALLOC_OBJ_ID, p, nbytes);
}
void
_PyObject_DebugFree(void *p)
{
_PyObject_DebugFreeApi(_PYMALLOC_OBJ_ID, p);
}
void
_PyObject_DebugCheckAddress(void *p)
{
_PyObject_DebugCheckAddressApi(_PYMALLOC_OBJ_ID, p);
}
/* generic debug memory api, with an "id" to identify the API in use */
void *
_PyObject_DebugMallocApi(char id, size_t nbytes)
{
uchar *p; /* base address of malloc'ed block */
uchar *tail; /* p + 2*SST + nbytes == pointer to tail pad bytes */
@ -1348,12 +1393,15 @@ _PyObject_DebugMalloc(size_t nbytes)
if (p == NULL)
return NULL;
/* at p, write size (SST bytes), id (1 byte), pad (SST-1 bytes) */
write_size_t(p, nbytes);
memset(p + SST, FORBIDDENBYTE, SST);
p[SST] = (uchar)id;
memset(p + SST + 1 , FORBIDDENBYTE, SST-1);
if (nbytes > 0)
memset(p + 2*SST, CLEANBYTE, nbytes);
/* at tail, write pad (SST bytes) and serialno (SST bytes) */
tail = p + 2*SST + nbytes;
memset(tail, FORBIDDENBYTE, SST);
write_size_t(tail + SST, serialno);
@ -1362,27 +1410,28 @@ _PyObject_DebugMalloc(size_t nbytes)
}
/* The debug free first checks the 2*SST bytes on each end for sanity (in
particular, that the FORBIDDENBYTEs are still intact).
particular, that the FORBIDDENBYTEs with the api ID are still intact).
Then fills the original bytes with DEADBYTE.
Then calls the underlying free.
*/
void
_PyObject_DebugFree(void *p)
_PyObject_DebugFreeApi(char api, void *p)
{
uchar *q = (uchar *)p - 2*SST; /* address returned from malloc */
size_t nbytes;
if (p == NULL)
return;
_PyObject_DebugCheckAddress(p);
_PyObject_DebugCheckAddressApi(api, p);
nbytes = read_size_t(q);
nbytes += 4*SST;
if (nbytes > 0)
memset(q, DEADBYTE, nbytes);
PyObject_Free(q);
}
void *
_PyObject_DebugRealloc(void *p, size_t nbytes)
_PyObject_DebugReallocApi(char api, void *p, size_t nbytes)
{
uchar *q = (uchar *)p;
uchar *tail;
@ -1391,9 +1440,9 @@ _PyObject_DebugRealloc(void *p, size_t nbytes)
int i;
if (p == NULL)
return _PyObject_DebugMalloc(nbytes);
return _PyObject_DebugMallocApi(api, nbytes);
_PyObject_DebugCheckAddress(p);
_PyObject_DebugCheckAddressApi(api, p);
bumpserialno();
original_nbytes = read_size_t(q - 2*SST);
total = nbytes + 4*SST;
@ -1403,16 +1452,20 @@ _PyObject_DebugRealloc(void *p, size_t nbytes)
if (nbytes < original_nbytes) {
/* shrinking: mark old extra memory dead */
memset(q + nbytes, DEADBYTE, original_nbytes - nbytes);
memset(q + nbytes, DEADBYTE, original_nbytes - nbytes + 2*SST);
}
/* Resize and add decorations. */
/* Resize and add decorations. We may get a new pointer here, in which
* case we didn't get the chance to mark the old memory with DEADBYTE,
* but we live with that.
*/
q = (uchar *)PyObject_Realloc(q - 2*SST, total);
if (q == NULL)
return NULL;
write_size_t(q, nbytes);
for (i = 0; i < SST; ++i)
assert(q[SST] == (uchar)api);
for (i = 1; i < SST; ++i)
assert(q[SST + i] == FORBIDDENBYTE);
q += 2*SST;
tail = q + nbytes;
@ -1431,26 +1484,38 @@ _PyObject_DebugRealloc(void *p, size_t nbytes)
/* Check the forbidden bytes on both ends of the memory allocated for p.
* If anything is wrong, print info to stderr via _PyObject_DebugDumpAddress,
* and call Py_FatalError to kill the program.
* The API id, is also checked.
*/
void
_PyObject_DebugCheckAddress(const void *p)
_PyObject_DebugCheckAddressApi(char api, const void *p)
{
const uchar *q = (const uchar *)p;
char msgbuf[64];
char *msg;
size_t nbytes;
const uchar *tail;
int i;
char id;
if (p == NULL) {
msg = "didn't expect a NULL pointer";
goto error;
}
/* Check the API id */
id = (char)q[-SST];
if (id != api) {
msg = msgbuf;
snprintf(msg, sizeof(msgbuf), "bad ID: Allocated using API '%c', verified using API '%c'", id, api);
msgbuf[sizeof(msgbuf)-1] = 0;
goto error;
}
/* Check the stuff at the start of p first: if there's underwrite
* corruption, the number-of-bytes field may be nuts, and checking
* the tail could lead to a segfault then.
*/
for (i = SST; i >= 1; --i) {
for (i = SST-1; i >= 1; --i) {
if (*(q-i) != FORBIDDENBYTE) {
msg = "bad leading pad byte";
goto error;
@ -1482,19 +1547,24 @@ _PyObject_DebugDumpAddress(const void *p)
size_t nbytes, serial;
int i;
int ok;
char id;
fprintf(stderr, "Debug memory block at address p=%p:\n", p);
if (p == NULL)
fprintf(stderr, "Debug memory block at address p=%p:", p);
if (p == NULL) {
fprintf(stderr, "\n");
return;
}
id = (char)q[-SST];
fprintf(stderr, " API '%c'\n", id);
nbytes = read_size_t(q - 2*SST);
fprintf(stderr, " %" PY_FORMAT_SIZE_T "u bytes originally "
"requested\n", nbytes);
/* In case this is nuts, check the leading pad bytes first. */
fprintf(stderr, " The %d pad bytes at p-%d are ", SST, SST);
fprintf(stderr, " The %d pad bytes at p-%d are ", SST-1, SST-1);
ok = 1;
for (i = 1; i <= SST; ++i) {
for (i = 1; i <= SST-1; ++i) {
if (*(q-i) != FORBIDDENBYTE) {
ok = 0;
break;
@ -1505,7 +1575,7 @@ _PyObject_DebugDumpAddress(const void *p)
else {
fprintf(stderr, "not all FORBIDDENBYTE (0x%02x):\n",
FORBIDDENBYTE);
for (i = SST; i >= 1; --i) {
for (i = SST-1; i >= 1; --i) {
const uchar byte = *(q-i);
fprintf(stderr, " at p-%d: 0x%02x", i, byte);
if (byte != FORBIDDENBYTE)