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Check that alignment is power of 2 in mj_stackAlloc.

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PiperOrigin-RevId: 562024496
Change-Id: I9230c6dc05ebb78e935f9b2f606aa77c921d67e5
This commit is contained in:
Saran Tunyasuvunakool
2023-09-01 12:44:53 -07:00
committed by Copybara-Service
parent 29aa5e4a41
commit 33f51856c1
7 changed files with 34 additions and 24 deletions
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src/engine/engine_io.c
+14 -10
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@@ -26,7 +26,7 @@
#include <mujoco/mjmacro.h>
#include <mujoco/mjplugin.h>
#include <mujoco/mjxmacro.h>
#include "engine/engine_array_safety.h" // IWYU pragma: keep
#include "engine/engine_crossplatform.h"
#include "engine/engine_resource.h"
#include "engine/engine_macro.h"
#include "engine/engine_plugin.h"
@@ -45,9 +45,13 @@
static const int MAX_ARRAY_SIZE = INT_MAX / 4;
// compute a % b assuming that the second argument is a power of 2
static inline size_t modpow2(size_t a, size_t b) {
return a & (b - 1);
// compute a % b with a fast code path if the second argument is a power of 2
static inline size_t fastmod(size_t a, size_t b) {
// (b & (b - 1)) == 0 implies that b is a power of 2
if (mjLIKELY((b & (b - 1)) == 0)) {
return a & (b - 1);
}
return a % b;
}
//------------------------------ mjLROpt -----------------------------------------------------------
@@ -1187,12 +1191,12 @@ mjData* mj_copyData(mjData* dest, const mjModel* m, const mjData* src) {
// allocate memory from the mjData arena
void* mj_arenaAlloc(mjData* d, size_t bytes, size_t alignment) {
size_t misalignment = modpow2(d->parena, alignment);
size_t misalignment = fastmod(d->parena, alignment);
size_t padding = misalignment ? alignment - misalignment : 0;
// check size
size_t bytes_available = d->narena - d->pstack;
if (d->parena + padding + bytes > bytes_available) {
if (mjUNLIKELY(d->parena + padding + bytes > bytes_available)) {
return NULL;
}
@@ -1218,7 +1222,7 @@ void* mj_arenaAlloc(mjData* d, size_t bytes, size_t alignment) {
// declared inline so that modular arithmetic with specific alignments can be optimized out
static inline void* stackalloc(mjData* d, size_t size, size_t alignment) {
// return NULL if empty
if (!size) {
if (mjUNLIKELY(!size)) {
return NULL;
}
@@ -1242,7 +1246,7 @@ static inline void* stackalloc(mjData* d, size_t size, size_t alignment) {
uintptr_t start_ptr = end_ptr - (size + mjREDZONE);
// align the pointer
start_ptr -= modpow2(start_ptr, alignment);
start_ptr -= fastmod(start_ptr, alignment);
// new top of the stack
uintptr_t new_pstack_ptr = start_ptr - mjREDZONE;
@@ -1255,8 +1259,8 @@ static inline void* stackalloc(mjData* d, size_t size, size_t alignment) {
// check size
size_t stack_available_bytes = end_ptr - ((uintptr_t)d->arena + d->parena);
size_t stack_required_bytes = end_ptr - new_pstack_ptr;
if (stack_required_bytes > stack_available_bytes) {
mju_error("mjData stack overflow: max = %zu, available = %zu, requested = %zu "
if (mjUNLIKELY(stack_required_bytes > stack_available_bytes)) {
mju_error("mj_stackAlloc: insufficient memory: max = %zu, available = %zu, requested = %zu "
"(ne = %d, nf = %d, nefc = %d, ncon = %d)",
stack_size_bytes, stack_available_bytes, stack_required_bytes,
d->ne, d->nf, d->nefc, d->ncon);