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Copy pathobmalloc.c
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2024 lines (1741 loc) · 60 KB
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#include "Python.h"
#include "internal/mem.h"
#include "internal/pystate.h"
#include <stdbool.h>
/* Defined in tracemalloc.c */
extern void _PyMem_DumpTraceback(int fd, const void *ptr);
/* Python's malloc wrappers (see pymem.h) */
#undef uint
#define uint unsigned int /* assuming >= 16 bits */
/* Forward declaration */
static void* _PyMem_DebugRawMalloc(void *ctx, size_t size);
static void* _PyMem_DebugRawCalloc(void *ctx, size_t nelem, size_t elsize);
static void* _PyMem_DebugRawRealloc(void *ctx, void *ptr, size_t size);
static void _PyMem_DebugRawFree(void *ctx, void *ptr);
static void* _PyMem_DebugMalloc(void *ctx, size_t size);
static void* _PyMem_DebugCalloc(void *ctx, size_t nelem, size_t elsize);
static void* _PyMem_DebugRealloc(void *ctx, void *ptr, size_t size);
static void _PyMem_DebugFree(void *ctx, void *p);
static void _PyObject_DebugDumpAddress(const void *p);
static void _PyMem_DebugCheckAddress(char api_id, const void *p);
#if defined(__has_feature) /* Clang */
#if __has_feature(address_sanitizer) /* is ASAN enabled? */
#define ATTRIBUTE_NO_ADDRESS_SAFETY_ANALYSIS \
__attribute__((no_address_safety_analysis))
#else
#define ATTRIBUTE_NO_ADDRESS_SAFETY_ANALYSIS
#endif
#else
#if defined(__SANITIZE_ADDRESS__) /* GCC 4.8.x, is ASAN enabled? */
#define ATTRIBUTE_NO_ADDRESS_SAFETY_ANALYSIS \
__attribute__((no_address_safety_analysis))
#else
#define ATTRIBUTE_NO_ADDRESS_SAFETY_ANALYSIS
#endif
#endif
#ifdef WITH_PYMALLOC
#ifdef MS_WINDOWS
# include <windows.h>
#elif defined(HAVE_MMAP)
# include <sys/mman.h>
# ifdef MAP_ANONYMOUS
# define ARENAS_USE_MMAP
# endif
#endif
/* Forward declaration */
static void* _PyObject_Malloc(void *ctx, size_t size);
static void* _PyObject_Calloc(void *ctx, size_t nelem, size_t elsize);
static void _PyObject_Free(void *ctx, void *p);
static void* _PyObject_Realloc(void *ctx, void *ptr, size_t size);
#endif
static void *
_PyMem_RawMalloc(void *ctx, size_t size)
{
/* PyMem_RawMalloc(0) means malloc(1). Some systems would return NULL
for malloc(0), which would be treated as an error. Some platforms would
return a pointer with no memory behind it, which would break pymalloc.
To solve these problems, allocate an extra byte. */
if (size == 0)
size = 1;
return malloc(size);
}
static void *
_PyMem_RawCalloc(void *ctx, size_t nelem, size_t elsize)
{
/* PyMem_RawCalloc(0, 0) means calloc(1, 1). Some systems would return NULL
for calloc(0, 0), which would be treated as an error. Some platforms
would return a pointer with no memory behind it, which would break
pymalloc. To solve these problems, allocate an extra byte. */
if (nelem == 0 || elsize == 0) {
nelem = 1;
elsize = 1;
}
return calloc(nelem, elsize);
}
static void *
_PyMem_RawRealloc(void *ctx, void *ptr, size_t size)
{
if (size == 0)
size = 1;
return realloc(ptr, size);
}
static void
_PyMem_RawFree(void *ctx, void *ptr)
{
free(ptr);
}
#ifdef MS_WINDOWS
static void *
_PyObject_ArenaVirtualAlloc(void *ctx, size_t size)
{
return VirtualAlloc(NULL, size,
MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
}
static void
_PyObject_ArenaVirtualFree(void *ctx, void *ptr, size_t size)
{
VirtualFree(ptr, 0, MEM_RELEASE);
}
#elif defined(ARENAS_USE_MMAP)
static void *
_PyObject_ArenaMmap(void *ctx, size_t size)
{
void *ptr;
ptr = mmap(NULL, size, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
if (ptr == MAP_FAILED)
return NULL;
assert(ptr != NULL);
return ptr;
}
static void
_PyObject_ArenaMunmap(void *ctx, void *ptr, size_t size)
{
munmap(ptr, size);
}
#else
static void *
_PyObject_ArenaMalloc(void *ctx, size_t size)
{
return malloc(size);
}
static void
_PyObject_ArenaFree(void *ctx, void *ptr, size_t size)
{
free(ptr);
}
#endif
#define PYRAW_FUNCS _PyMem_RawMalloc, _PyMem_RawCalloc, _PyMem_RawRealloc, _PyMem_RawFree
#ifdef WITH_PYMALLOC
# define PYOBJ_FUNCS _PyObject_Malloc, _PyObject_Calloc, _PyObject_Realloc, _PyObject_Free
#else
# define PYOBJ_FUNCS PYRAW_FUNCS
#endif
#define PYMEM_FUNCS PYOBJ_FUNCS
typedef struct {
/* We tag each block with an API ID in order to tag API violations */
char api_id;
PyMemAllocatorEx alloc;
} debug_alloc_api_t;
static struct {
debug_alloc_api_t raw;
debug_alloc_api_t mem;
debug_alloc_api_t obj;
} _PyMem_Debug = {
{'r', {NULL, PYRAW_FUNCS}},
{'m', {NULL, PYMEM_FUNCS}},
{'o', {NULL, PYOBJ_FUNCS}}
};
#define PYRAWDBG_FUNCS \
_PyMem_DebugRawMalloc, _PyMem_DebugRawCalloc, _PyMem_DebugRawRealloc, _PyMem_DebugRawFree
#define PYDBG_FUNCS \
_PyMem_DebugMalloc, _PyMem_DebugCalloc, _PyMem_DebugRealloc, _PyMem_DebugFree
#define _PyMem_Raw _PyRuntime.mem.allocators.raw
#define _PyMem _PyRuntime.mem.allocators.mem
#define _PyObject _PyRuntime.mem.allocators.obj
void
_PyMem_GetDefaultRawAllocator(PyMemAllocatorEx *alloc_p)
{
PyMemAllocatorEx alloc = {NULL, PYRAW_FUNCS};
*alloc_p = alloc;
}
int
_PyMem_SetupAllocators(const char *opt)
{
if (opt == NULL || *opt == '\0') {
/* PYTHONMALLOC is empty or is not set or ignored (-E/-I command line
options): use default allocators */
#ifdef Py_DEBUG
# ifdef WITH_PYMALLOC
opt = "pymalloc_debug";
# else
opt = "malloc_debug";
# endif
#else
/* !Py_DEBUG */
# ifdef WITH_PYMALLOC
opt = "pymalloc";
# else
opt = "malloc";
# endif
#endif
}
if (strcmp(opt, "debug") == 0) {
PyMem_SetupDebugHooks();
}
else if (strcmp(opt, "malloc") == 0 || strcmp(opt, "malloc_debug") == 0)
{
PyMemAllocatorEx alloc = {NULL, PYRAW_FUNCS};
PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &alloc);
PyMem_SetAllocator(PYMEM_DOMAIN_MEM, &alloc);
PyMem_SetAllocator(PYMEM_DOMAIN_OBJ, &alloc);
if (strcmp(opt, "malloc_debug") == 0)
PyMem_SetupDebugHooks();
}
#ifdef WITH_PYMALLOC
else if (strcmp(opt, "pymalloc") == 0
|| strcmp(opt, "pymalloc_debug") == 0)
{
PyMemAllocatorEx raw_alloc = {NULL, PYRAW_FUNCS};
PyMemAllocatorEx mem_alloc = {NULL, PYMEM_FUNCS};
PyMemAllocatorEx obj_alloc = {NULL, PYOBJ_FUNCS};
PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &raw_alloc);
PyMem_SetAllocator(PYMEM_DOMAIN_MEM, &mem_alloc);
PyMem_SetAllocator(PYMEM_DOMAIN_OBJ, &obj_alloc);
if (strcmp(opt, "pymalloc_debug") == 0)
PyMem_SetupDebugHooks();
}
#endif
else {
/* unknown allocator */
return -1;
}
return 0;
}
void
_PyObject_Initialize(struct _pyobj_runtime_state *state)
{
PyObjectArenaAllocator _PyObject_Arena = {NULL,
#ifdef MS_WINDOWS
_PyObject_ArenaVirtualAlloc, _PyObject_ArenaVirtualFree
#elif defined(ARENAS_USE_MMAP)
_PyObject_ArenaMmap, _PyObject_ArenaMunmap
#else
_PyObject_ArenaMalloc, _PyObject_ArenaFree
#endif
};
state->allocator_arenas = _PyObject_Arena;
}
void
_PyMem_Initialize(struct _pymem_runtime_state *state)
{
PyMemAllocatorEx pymem_raw = {
#ifdef Py_DEBUG
&_PyMem_Debug.raw, PYRAWDBG_FUNCS
#else
NULL, PYRAW_FUNCS
#endif
};
PyMemAllocatorEx pymem = {
#ifdef Py_DEBUG
&_PyMem_Debug.mem, PYDBG_FUNCS
#else
NULL, PYMEM_FUNCS
#endif
};
PyMemAllocatorEx pyobject = {
#ifdef Py_DEBUG
&_PyMem_Debug.obj, PYDBG_FUNCS
#else
NULL, PYOBJ_FUNCS
#endif
};
state->allocators.raw = pymem_raw;
state->allocators.mem = pymem;
state->allocators.obj = pyobject;
#ifdef WITH_PYMALLOC
Py_BUILD_ASSERT(NB_SMALL_SIZE_CLASSES == 64);
for (int i = 0; i < 8; i++) {
for (int j = 0; j < 8; j++) {
int x = i * 8 + j;
poolp *addr = &(state->usedpools[2*(x)]);
poolp val = (poolp)((uint8_t *)addr - 2*sizeof(pyblock *));
state->usedpools[x * 2] = val;
state->usedpools[x * 2 + 1] = val;
};
};
#endif /* WITH_PYMALLOC */
}
#ifdef WITH_PYMALLOC
static int
_PyMem_DebugEnabled(void)
{
return (_PyObject.malloc == _PyMem_DebugMalloc);
}
int
_PyMem_PymallocEnabled(void)
{
if (_PyMem_DebugEnabled()) {
return (_PyMem_Debug.obj.alloc.malloc == _PyObject_Malloc);
}
else {
return (_PyObject.malloc == _PyObject_Malloc);
}
}
#endif
void
PyMem_SetupDebugHooks(void)
{
PyMemAllocatorEx alloc;
alloc.malloc = _PyMem_DebugRawMalloc;
alloc.calloc = _PyMem_DebugRawCalloc;
alloc.realloc = _PyMem_DebugRawRealloc;
alloc.free = _PyMem_DebugRawFree;
if (_PyMem_Raw.malloc != _PyMem_DebugRawMalloc) {
alloc.ctx = &_PyMem_Debug.raw;
PyMem_GetAllocator(PYMEM_DOMAIN_RAW, &_PyMem_Debug.raw.alloc);
PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &alloc);
}
alloc.malloc = _PyMem_DebugMalloc;
alloc.calloc = _PyMem_DebugCalloc;
alloc.realloc = _PyMem_DebugRealloc;
alloc.free = _PyMem_DebugFree;
if (_PyMem.malloc != _PyMem_DebugMalloc) {
alloc.ctx = &_PyMem_Debug.mem;
PyMem_GetAllocator(PYMEM_DOMAIN_MEM, &_PyMem_Debug.mem.alloc);
PyMem_SetAllocator(PYMEM_DOMAIN_MEM, &alloc);
}
if (_PyObject.malloc != _PyMem_DebugMalloc) {
alloc.ctx = &_PyMem_Debug.obj;
PyMem_GetAllocator(PYMEM_DOMAIN_OBJ, &_PyMem_Debug.obj.alloc);
PyMem_SetAllocator(PYMEM_DOMAIN_OBJ, &alloc);
}
}
void
PyMem_GetAllocator(PyMemAllocatorDomain domain, PyMemAllocatorEx *allocator)
{
switch(domain)
{
case PYMEM_DOMAIN_RAW: *allocator = _PyMem_Raw; break;
case PYMEM_DOMAIN_MEM: *allocator = _PyMem; break;
case PYMEM_DOMAIN_OBJ: *allocator = _PyObject; break;
default:
/* unknown domain: set all attributes to NULL */
allocator->ctx = NULL;
allocator->malloc = NULL;
allocator->calloc = NULL;
allocator->realloc = NULL;
allocator->free = NULL;
}
}
void
PyMem_SetAllocator(PyMemAllocatorDomain domain, PyMemAllocatorEx *allocator)
{
switch(domain)
{
case PYMEM_DOMAIN_RAW: _PyMem_Raw = *allocator; break;
case PYMEM_DOMAIN_MEM: _PyMem = *allocator; break;
case PYMEM_DOMAIN_OBJ: _PyObject = *allocator; break;
/* ignore unknown domain */
}
}
void
PyObject_GetArenaAllocator(PyObjectArenaAllocator *allocator)
{
*allocator = _PyRuntime.obj.allocator_arenas;
}
void
PyObject_SetArenaAllocator(PyObjectArenaAllocator *allocator)
{
_PyRuntime.obj.allocator_arenas = *allocator;
}
void *
PyMem_RawMalloc(size_t size)
{
/*
* Limit ourselves to PY_SSIZE_T_MAX bytes to prevent security holes.
* Most python internals blindly use a signed Py_ssize_t to track
* things without checking for overflows or negatives.
* As size_t is unsigned, checking for size < 0 is not required.
*/
if (size > (size_t)PY_SSIZE_T_MAX)
return NULL;
return _PyMem_Raw.malloc(_PyMem_Raw.ctx, size);
}
void *
PyMem_RawCalloc(size_t nelem, size_t elsize)
{
/* see PyMem_RawMalloc() */
if (elsize != 0 && nelem > (size_t)PY_SSIZE_T_MAX / elsize)
return NULL;
return _PyMem_Raw.calloc(_PyMem_Raw.ctx, nelem, elsize);
}
void*
PyMem_RawRealloc(void *ptr, size_t new_size)
{
/* see PyMem_RawMalloc() */
if (new_size > (size_t)PY_SSIZE_T_MAX)
return NULL;
return _PyMem_Raw.realloc(_PyMem_Raw.ctx, ptr, new_size);
}
void
PyMem_RawFree(void *ptr)
{
_PyMem_Raw.free(_PyMem_Raw.ctx, ptr);
}
void *
PyMem_Malloc(size_t size)
{
/* see PyMem_RawMalloc() */
if (size > (size_t)PY_SSIZE_T_MAX)
return NULL;
return _PyMem.malloc(_PyMem.ctx, size);
}
void *
PyMem_Calloc(size_t nelem, size_t elsize)
{
/* see PyMem_RawMalloc() */
if (elsize != 0 && nelem > (size_t)PY_SSIZE_T_MAX / elsize)
return NULL;
return _PyMem.calloc(_PyMem.ctx, nelem, elsize);
}
void *
PyMem_Realloc(void *ptr, size_t new_size)
{
/* see PyMem_RawMalloc() */
if (new_size > (size_t)PY_SSIZE_T_MAX)
return NULL;
return _PyMem.realloc(_PyMem.ctx, ptr, new_size);
}
void
PyMem_Free(void *ptr)
{
_PyMem.free(_PyMem.ctx, ptr);
}
char *
_PyMem_RawStrdup(const char *str)
{
size_t size;
char *copy;
size = strlen(str) + 1;
copy = PyMem_RawMalloc(size);
if (copy == NULL)
return NULL;
memcpy(copy, str, size);
return copy;
}
char *
_PyMem_Strdup(const char *str)
{
size_t size;
char *copy;
size = strlen(str) + 1;
copy = PyMem_Malloc(size);
if (copy == NULL)
return NULL;
memcpy(copy, str, size);
return copy;
}
void *
PyObject_Malloc(size_t size)
{
/* see PyMem_RawMalloc() */
if (size > (size_t)PY_SSIZE_T_MAX)
return NULL;
return _PyObject.malloc(_PyObject.ctx, size);
}
void *
PyObject_Calloc(size_t nelem, size_t elsize)
{
/* see PyMem_RawMalloc() */
if (elsize != 0 && nelem > (size_t)PY_SSIZE_T_MAX / elsize)
return NULL;
return _PyObject.calloc(_PyObject.ctx, nelem, elsize);
}
void *
PyObject_Realloc(void *ptr, size_t new_size)
{
/* see PyMem_RawMalloc() */
if (new_size > (size_t)PY_SSIZE_T_MAX)
return NULL;
return _PyObject.realloc(_PyObject.ctx, ptr, new_size);
}
void
PyObject_Free(void *ptr)
{
_PyObject.free(_PyObject.ctx, ptr);
}
#ifdef WITH_PYMALLOC
#ifdef WITH_VALGRIND
#include <valgrind/valgrind.h>
/* If we're using GCC, use __builtin_expect() to reduce overhead of
the valgrind checks */
#if defined(__GNUC__) && (__GNUC__ > 2) && defined(__OPTIMIZE__)
# define UNLIKELY(value) __builtin_expect((value), 0)
#else
# define UNLIKELY(value) (value)
#endif
/* -1 indicates that we haven't checked that we're running on valgrind yet. */
static int running_on_valgrind = -1;
#endif
Py_ssize_t
_Py_GetAllocatedBlocks(void)
{
return _PyRuntime.mem.num_allocated_blocks;
}
/* Allocate a new arena. If we run out of memory, return NULL. Else
* allocate a new arena, and return the address of an arena_object
* describing the new arena. It's expected that the caller will set
* `usable_arenas` to the return value.
*/
static struct arena_object*
new_arena(void)
{
struct arena_object* arenaobj;
uint excess; /* number of bytes above pool alignment */
void *address;
static int debug_stats = -1;
if (debug_stats == -1) {
char *opt = Py_GETENV("PYTHONMALLOCSTATS");
debug_stats = (opt != NULL && *opt != '\0');
}
if (debug_stats)
_PyObject_DebugMallocStats(stderr);
if (_PyRuntime.mem.unused_arena_objects == NULL) {
uint i;
uint numarenas;
size_t nbytes;
/* Double the number of arena objects on each allocation.
* Note that it's possible for `numarenas` to overflow.
*/
numarenas = _PyRuntime.mem.maxarenas ? _PyRuntime.mem.maxarenas << 1 : INITIAL_ARENA_OBJECTS;
if (numarenas <= _PyRuntime.mem.maxarenas)
return NULL; /* overflow */
#if SIZEOF_SIZE_T <= SIZEOF_INT
if (numarenas > SIZE_MAX / sizeof(*_PyRuntime.mem.arenas))
return NULL; /* overflow */
#endif
nbytes = numarenas * sizeof(*_PyRuntime.mem.arenas);
arenaobj = (struct arena_object *)PyMem_RawRealloc(_PyRuntime.mem.arenas, nbytes);
if (arenaobj == NULL)
return NULL;
_PyRuntime.mem.arenas = arenaobj;
/* We might need to fix pointers that were copied. However,
* new_arena only gets called when all the pages in the
* previous arenas are full. Thus, there are *no* pointers
* into the old array. Thus, we don't have to worry about
* invalid pointers. Just to be sure, some asserts:
*/
assert(_PyRuntime.mem.usable_arenas == NULL);
assert(_PyRuntime.mem.unused_arena_objects == NULL);
/* Put the new arenas on the unused_arena_objects list. */
for (i = _PyRuntime.mem.maxarenas; i < numarenas; ++i) {
_PyRuntime.mem.arenas[i].address = 0; /* mark as unassociated */
_PyRuntime.mem.arenas[i].nextarena = i < numarenas - 1 ?
&_PyRuntime.mem.arenas[i+1] : NULL;
}
/* Update globals. */
_PyRuntime.mem.unused_arena_objects = &_PyRuntime.mem.arenas[_PyRuntime.mem.maxarenas];
_PyRuntime.mem.maxarenas = numarenas;
}
/* Take the next available arena object off the head of the list. */
assert(_PyRuntime.mem.unused_arena_objects != NULL);
arenaobj = _PyRuntime.mem.unused_arena_objects;
_PyRuntime.mem.unused_arena_objects = arenaobj->nextarena;
assert(arenaobj->address == 0);
address = _PyRuntime.obj.allocator_arenas.alloc(_PyRuntime.obj.allocator_arenas.ctx, ARENA_SIZE);
if (address == NULL) {
/* The allocation failed: return NULL after putting the
* arenaobj back.
*/
arenaobj->nextarena = _PyRuntime.mem.unused_arena_objects;
_PyRuntime.mem.unused_arena_objects = arenaobj;
return NULL;
}
arenaobj->address = (uintptr_t)address;
++_PyRuntime.mem.narenas_currently_allocated;
++_PyRuntime.mem.ntimes_arena_allocated;
if (_PyRuntime.mem.narenas_currently_allocated > _PyRuntime.mem.narenas_highwater)
_PyRuntime.mem.narenas_highwater = _PyRuntime.mem.narenas_currently_allocated;
arenaobj->freepools = NULL;
/* pool_address <- first pool-aligned address in the arena
nfreepools <- number of whole pools that fit after alignment */
arenaobj->pool_address = (pyblock*)arenaobj->address;
arenaobj->nfreepools = ARENA_SIZE / POOL_SIZE;
assert(POOL_SIZE * arenaobj->nfreepools == ARENA_SIZE);
excess = (uint)(arenaobj->address & POOL_SIZE_MASK);
if (excess != 0) {
--arenaobj->nfreepools;
arenaobj->pool_address += POOL_SIZE - excess;
}
arenaobj->ntotalpools = arenaobj->nfreepools;
return arenaobj;
}
/*
address_in_range(P, POOL)
Return true if and only if P is an address that was allocated by pymalloc.
POOL must be the pool address associated with P, i.e., POOL = POOL_ADDR(P)
(the caller is asked to compute this because the macro expands POOL more than
once, and for efficiency it's best for the caller to assign POOL_ADDR(P) to a
variable and pass the latter to the macro; because address_in_range is
called on every alloc/realloc/free, micro-efficiency is important here).
Tricky: Let B be the arena base address associated with the pool, B =
arenas[(POOL)->arenaindex].address. Then P belongs to the arena if and only if
B <= P < B + ARENA_SIZE
Subtracting B throughout, this is true iff
0 <= P-B < ARENA_SIZE
By using unsigned arithmetic, the "0 <=" half of the test can be skipped.
Obscure: A PyMem "free memory" function can call the pymalloc free or realloc
before the first arena has been allocated. `arenas` is still NULL in that
case. We're relying on that maxarenas is also 0 in that case, so that
(POOL)->arenaindex < maxarenas must be false, saving us from trying to index
into a NULL arenas.
Details: given P and POOL, the arena_object corresponding to P is AO =
arenas[(POOL)->arenaindex]. Suppose obmalloc controls P. Then (barring wild
stores, etc), POOL is the correct address of P's pool, AO.address is the
correct base address of the pool's arena, and P must be within ARENA_SIZE of
AO.address. In addition, AO.address is not 0 (no arena can start at address 0
(NULL)). Therefore address_in_range correctly reports that obmalloc
controls P.
Now suppose obmalloc does not control P (e.g., P was obtained via a direct
call to the system malloc() or realloc()). (POOL)->arenaindex may be anything
in this case -- it may even be uninitialized trash. If the trash arenaindex
is >= maxarenas, the macro correctly concludes at once that obmalloc doesn't
control P.
Else arenaindex is < maxarena, and AO is read up. If AO corresponds to an
allocated arena, obmalloc controls all the memory in slice AO.address :
AO.address+ARENA_SIZE. By case assumption, P is not controlled by obmalloc,
so P doesn't lie in that slice, so the macro correctly reports that P is not
controlled by obmalloc.
Finally, if P is not controlled by obmalloc and AO corresponds to an unused
arena_object (one not currently associated with an allocated arena),
AO.address is 0, and the second test in the macro reduces to:
P < ARENA_SIZE
If P >= ARENA_SIZE (extremely likely), the macro again correctly concludes
that P is not controlled by obmalloc. However, if P < ARENA_SIZE, this part
of the test still passes, and the third clause (AO.address != 0) is necessary
to get the correct result: AO.address is 0 in this case, so the macro
correctly reports that P is not controlled by obmalloc (despite that P lies in
slice AO.address : AO.address + ARENA_SIZE).
Note: The third (AO.address != 0) clause was added in Python 2.5. Before
2.5, arenas were never free()'ed, and an arenaindex < maxarena always
corresponded to a currently-allocated arena, so the "P is not controlled by
obmalloc, AO corresponds to an unused arena_object, and P < ARENA_SIZE" case
was impossible.
Note that the logic is excruciating, and reading up possibly uninitialized
memory when P is not controlled by obmalloc (to get at (POOL)->arenaindex)
creates problems for some memory debuggers. The overwhelming advantage is
that this test determines whether an arbitrary address is controlled by
obmalloc in a small constant time, independent of the number of arenas
obmalloc controls. Since this test is needed at every entry point, it's
extremely desirable that it be this fast.
*/
static bool ATTRIBUTE_NO_ADDRESS_SAFETY_ANALYSIS
address_in_range(void *p, poolp pool)
{
// Since address_in_range may be reading from memory which was not allocated
// by Python, it is important that pool->arenaindex is read only once, as
// another thread may be concurrently modifying the value without holding
// the GIL. The following dance forces the compiler to read pool->arenaindex
// only once.
uint arenaindex = *((volatile uint *)&pool->arenaindex);
return arenaindex < _PyRuntime.mem.maxarenas &&
(uintptr_t)p - _PyRuntime.mem.arenas[arenaindex].address < ARENA_SIZE &&
_PyRuntime.mem.arenas[arenaindex].address != 0;
}
/*==========================================================================*/
/* pymalloc allocator
The basic blocks are ordered by decreasing execution frequency,
which minimizes the number of jumps in the most common cases,
improves branching prediction and instruction scheduling (small
block allocations typically result in a couple of instructions).
Unless the optimizer reorders everything, being too smart...
Return 1 if pymalloc allocated memory and wrote the pointer into *ptr_p.
Return 0 if pymalloc failed to allocate the memory block: on bigger
requests, on error in the code below (as a last chance to serve the request)
or when the max memory limit has been reached. */
static int
pymalloc_alloc(void *ctx, void **ptr_p, size_t nbytes)
{
pyblock *bp;
poolp pool;
poolp next;
uint size;
#ifdef WITH_VALGRIND
if (UNLIKELY(running_on_valgrind == -1)) {
running_on_valgrind = RUNNING_ON_VALGRIND;
}
if (UNLIKELY(running_on_valgrind)) {
return 0;
}
#endif
if (nbytes == 0) {
return 0;
}
if (nbytes > SMALL_REQUEST_THRESHOLD) {
return 0;
}
LOCK();
/*
* Most frequent paths first
*/
size = (uint)(nbytes - 1) >> ALIGNMENT_SHIFT;
pool = _PyRuntime.mem.usedpools[size + size];
if (pool != pool->nextpool) {
/*
* There is a used pool for this size class.
* Pick up the head block of its free list.
*/
++pool->ref.count;
bp = pool->freeblock;
assert(bp != NULL);
if ((pool->freeblock = *(pyblock **)bp) != NULL) {
goto success;
}
/*
* Reached the end of the free list, try to extend it.
*/
if (pool->nextoffset <= pool->maxnextoffset) {
/* There is room for another block. */
pool->freeblock = (pyblock*)pool +
pool->nextoffset;
pool->nextoffset += INDEX2SIZE(size);
*(pyblock **)(pool->freeblock) = NULL;
goto success;
}
/* Pool is full, unlink from used pools. */
next = pool->nextpool;
pool = pool->prevpool;
next->prevpool = pool;
pool->nextpool = next;
goto success;
}
/* There isn't a pool of the right size class immediately
* available: use a free pool.
*/
if (_PyRuntime.mem.usable_arenas == NULL) {
/* No arena has a free pool: allocate a new arena. */
#ifdef WITH_MEMORY_LIMITS
if (_PyRuntime.mem.narenas_currently_allocated >= MAX_ARENAS) {
goto failed;
}
#endif
_PyRuntime.mem.usable_arenas = new_arena();
if (_PyRuntime.mem.usable_arenas == NULL) {
goto failed;
}
_PyRuntime.mem.usable_arenas->nextarena =
_PyRuntime.mem.usable_arenas->prevarena = NULL;
}
assert(_PyRuntime.mem.usable_arenas->address != 0);
/* Try to get a cached free pool. */
pool = _PyRuntime.mem.usable_arenas->freepools;
if (pool != NULL) {
/* Unlink from cached pools. */
_PyRuntime.mem.usable_arenas->freepools = pool->nextpool;
/* This arena already had the smallest nfreepools
* value, so decreasing nfreepools doesn't change
* that, and we don't need to rearrange the
* usable_arenas list. However, if the arena has
* become wholly allocated, we need to remove its
* arena_object from usable_arenas.
*/
--_PyRuntime.mem.usable_arenas->nfreepools;
if (_PyRuntime.mem.usable_arenas->nfreepools == 0) {
/* Wholly allocated: remove. */
assert(_PyRuntime.mem.usable_arenas->freepools == NULL);
assert(_PyRuntime.mem.usable_arenas->nextarena == NULL ||
_PyRuntime.mem.usable_arenas->nextarena->prevarena ==
_PyRuntime.mem.usable_arenas);
_PyRuntime.mem.usable_arenas = _PyRuntime.mem.usable_arenas->nextarena;
if (_PyRuntime.mem.usable_arenas != NULL) {
_PyRuntime.mem.usable_arenas->prevarena = NULL;
assert(_PyRuntime.mem.usable_arenas->address != 0);
}
}
else {
/* nfreepools > 0: it must be that freepools
* isn't NULL, or that we haven't yet carved
* off all the arena's pools for the first
* time.
*/
assert(_PyRuntime.mem.usable_arenas->freepools != NULL ||
_PyRuntime.mem.usable_arenas->pool_address <=
(pyblock*)_PyRuntime.mem.usable_arenas->address +
ARENA_SIZE - POOL_SIZE);
}
init_pool:
/* Frontlink to used pools. */
next = _PyRuntime.mem.usedpools[size + size]; /* == prev */
pool->nextpool = next;
pool->prevpool = next;
next->nextpool = pool;
next->prevpool = pool;
pool->ref.count = 1;
if (pool->szidx == size) {
/* Luckily, this pool last contained blocks
* of the same size class, so its header
* and free list are already initialized.
*/
bp = pool->freeblock;
assert(bp != NULL);
pool->freeblock = *(pyblock **)bp;
goto success;
}
/*
* Initialize the pool header, set up the free list to
* contain just the second block, and return the first
* block.
*/
pool->szidx = size;
size = INDEX2SIZE(size);
bp = (pyblock *)pool + POOL_OVERHEAD;
pool->nextoffset = POOL_OVERHEAD + (size << 1);
pool->maxnextoffset = POOL_SIZE - size;
pool->freeblock = bp + size;
*(pyblock **)(pool->freeblock) = NULL;
goto success;
}
/* Carve off a new pool. */
assert(_PyRuntime.mem.usable_arenas->nfreepools > 0);
assert(_PyRuntime.mem.usable_arenas->freepools == NULL);
pool = (poolp)_PyRuntime.mem.usable_arenas->pool_address;
assert((pyblock*)pool <= (pyblock*)_PyRuntime.mem.usable_arenas->address +
ARENA_SIZE - POOL_SIZE);
pool->arenaindex = (uint)(_PyRuntime.mem.usable_arenas - _PyRuntime.mem.arenas);
assert(&_PyRuntime.mem.arenas[pool->arenaindex] == _PyRuntime.mem.usable_arenas);
pool->szidx = DUMMY_SIZE_IDX;
_PyRuntime.mem.usable_arenas->pool_address += POOL_SIZE;
--_PyRuntime.mem.usable_arenas->nfreepools;
if (_PyRuntime.mem.usable_arenas->nfreepools == 0) {
assert(_PyRuntime.mem.usable_arenas->nextarena == NULL ||
_PyRuntime.mem.usable_arenas->nextarena->prevarena ==
_PyRuntime.mem.usable_arenas);
/* Unlink the arena: it is completely allocated. */
_PyRuntime.mem.usable_arenas = _PyRuntime.mem.usable_arenas->nextarena;
if (_PyRuntime.mem.usable_arenas != NULL) {
_PyRuntime.mem.usable_arenas->prevarena = NULL;
assert(_PyRuntime.mem.usable_arenas->address != 0);
}
}
goto init_pool;
success:
UNLOCK();
assert(bp != NULL);
*ptr_p = (void *)bp;
return 1;
failed:
UNLOCK();
return 0;
}
static void *
_PyObject_Malloc(void *ctx, size_t nbytes)
{
void* ptr;
if (pymalloc_alloc(ctx, &ptr, nbytes)) {
_PyRuntime.mem.num_allocated_blocks++;
return ptr;
}
ptr = PyMem_RawMalloc(nbytes);
if (ptr != NULL) {
_PyRuntime.mem.num_allocated_blocks++;
}
return ptr;
}
static void *
_PyObject_Calloc(void *ctx, size_t nelem, size_t elsize)
{
void* ptr;
assert(elsize == 0 || nelem <= (size_t)PY_SSIZE_T_MAX / elsize);
size_t nbytes = nelem * elsize;
if (pymalloc_alloc(ctx, &ptr, nbytes)) {
memset(ptr, 0, nbytes);
_PyRuntime.mem.num_allocated_blocks++;
return ptr;
}
ptr = PyMem_RawCalloc(nelem, elsize);