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scratch: add magic bytes to beginning of structure

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This commit is contained in:
Andrew Poelstra 2019-03-13 22:35:08 +00:00
parent 92a48a764d
commit 0be1a4ae62
2 changed files with 22 additions and 0 deletions
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1
src/scratch.h
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@ -12,6 +12,7 @@
/* The typedef is used internally; the struct name is used in the public API /* The typedef is used internally; the struct name is used in the public API
* (where it is exposed as a different typedef) */ * (where it is exposed as a different typedef) */
typedef struct secp256k1_scratch_space_struct { typedef struct secp256k1_scratch_space_struct {
unsigned char magic[8];
void *data; void *data;
void *current_frame; void *current_frame;
size_t offset[SECP256K1_SCRATCH_MAX_FRAMES]; size_t offset[SECP256K1_SCRATCH_MAX_FRAMES];

21
src/scratch_impl.h
View File

@ -14,6 +14,7 @@ static secp256k1_scratch* secp256k1_scratch_create(const secp256k1_callback* err
secp256k1_scratch* ret = (secp256k1_scratch*)checked_malloc(error_callback, sizeof(*ret)); secp256k1_scratch* ret = (secp256k1_scratch*)checked_malloc(error_callback, sizeof(*ret));
if (ret != NULL) { if (ret != NULL) {
memset(ret, 0, sizeof(*ret)); memset(ret, 0, sizeof(*ret));
memcpy(ret->magic, "scratch", 8);
ret->data = (secp256k1_scratch*)checked_malloc(error_callback, max_size); ret->data = (secp256k1_scratch*)checked_malloc(error_callback, max_size);
ret->max_size = max_size; ret->max_size = max_size;
} }
@ -23,6 +24,10 @@ static secp256k1_scratch* secp256k1_scratch_create(const secp256k1_callback* err
static void secp256k1_scratch_destroy(secp256k1_scratch* scratch) { static void secp256k1_scratch_destroy(secp256k1_scratch* scratch) {
if (scratch != NULL) { if (scratch != NULL) {
VERIFY_CHECK(scratch->frame == 0); VERIFY_CHECK(scratch->frame == 0);
if (memcmp(scratch->magic, "scratch", 8) != 0) {
return;
}
memset(scratch->magic, 0, sizeof(scratch->magic));
free(scratch->data); free(scratch->data);
free(scratch); free(scratch);
} }
@ -31,6 +36,9 @@ static void secp256k1_scratch_destroy(secp256k1_scratch* scratch) {
static size_t secp256k1_scratch_max_allocation(const secp256k1_scratch* scratch, size_t objects) { static size_t secp256k1_scratch_max_allocation(const secp256k1_scratch* scratch, size_t objects) {
size_t i = 0; size_t i = 0;
size_t allocated = 0; size_t allocated = 0;
if (memcmp(scratch->magic, "scratch", 8) != 0) {
return 0;
}
for (i = 0; i < scratch->frame; i++) { for (i = 0; i < scratch->frame; i++) {
allocated += scratch->frame_size[i]; allocated += scratch->frame_size[i];
} }
@ -43,6 +51,10 @@ static size_t secp256k1_scratch_max_allocation(const secp256k1_scratch* scratch,
static int secp256k1_scratch_allocate_frame(secp256k1_scratch* scratch, size_t n, size_t objects) { static int secp256k1_scratch_allocate_frame(secp256k1_scratch* scratch, size_t n, size_t objects) {
VERIFY_CHECK(scratch->frame < SECP256K1_SCRATCH_MAX_FRAMES); VERIFY_CHECK(scratch->frame < SECP256K1_SCRATCH_MAX_FRAMES);
if (memcmp(scratch->magic, "scratch", 8) != 0) {
return 0;
}
if (n <= secp256k1_scratch_max_allocation(scratch, objects)) { if (n <= secp256k1_scratch_max_allocation(scratch, objects)) {
n += objects * ALIGNMENT; n += objects * ALIGNMENT;
scratch->current_frame = scratch->data; scratch->current_frame = scratch->data;
@ -58,6 +70,11 @@ static int secp256k1_scratch_allocate_frame(secp256k1_scratch* scratch, size_t n
static void secp256k1_scratch_deallocate_frame(secp256k1_scratch* scratch) { static void secp256k1_scratch_deallocate_frame(secp256k1_scratch* scratch) {
VERIFY_CHECK(scratch->frame > 0); VERIFY_CHECK(scratch->frame > 0);
if (memcmp(scratch->magic, "scratch", 8) != 0) {
return;
}
scratch->frame--; scratch->frame--;
scratch->data = (void *) ((char *) scratch->data - scratch->frame_size[scratch->frame]); scratch->data = (void *) ((char *) scratch->data - scratch->frame_size[scratch->frame]);
} }
@ -67,6 +84,10 @@ static void *secp256k1_scratch_alloc(secp256k1_scratch* scratch, size_t size) {
size_t frame = scratch->frame - 1; size_t frame = scratch->frame - 1;
size = ROUND_TO_ALIGN(size); size = ROUND_TO_ALIGN(size);
if (memcmp(scratch->magic, "scratch", 8) != 0) {
return NULL;
}
if (scratch->frame == 0 || size + scratch->offset[frame] > scratch->frame_size[frame]) { if (scratch->frame == 0 || size + scratch->offset[frame] > scratch->frame_size[frame]) {
return NULL; return NULL;
} }