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#include "arch.h"
#include "kern/mem.h"
#include "kern/common.h"
#ifdef ARCH_STM32L4
/* Provide a definition for memset() when not provided for the
* microcontroller. */
void* memset(void* dest, int c, size_t n)
{
uint8_t c8 = (uint8_t) c;
uint8_t* dest8 = (uint8_t*) dest;
uint8_t* to = dest8 + n;
while(dest8 < to) {
*(dest8 ++) = c8;
}
return dest;
}
#else
void* memset(void* dest, int c, size_t n);
#endif
typedef uint16_t halloc_off_t;
// The sizes will count the number of WORDS allocated.
// Since there's a max size of 16k, only 12 bits will be
// needed for this.
typedef struct HALLOC_NODE {
union {
uint32_t header;
struct {
/* Is this memory block currently in use (hasn't been hfree'd) */
bool used:1;
/* Number of words allocated. Does not include the header. */
uint16_t size:15;
/* The location of the previous block (in WORDS from offest) */
halloc_off_t prev;
} PACKED;
};
uint8_t mem[]; /* The memory to use. */
} halloc_node_t;
halloc_node_t* halloc_start;
#define halloc_node_next(cur) \
((halloc_node_t*)(((uint8_t*)(cur)) + (((cur)->size + 1) * 4)))
#define halloc_node_prev(cur) halloc_node_at_off(cur->prev)
#define halloc_node_at_off(offset) \
((halloc_node_t*)(((uint8_t*) halloc_start) + (offset) * 4))
#define halloc_node_get_off(node) \
(((uint32_t)(((uint8_t*)(node)) - ((uint8_t*)(halloc_start)))) / 4)
#define size_for(n) \
(((n) / 4) + ((n) % 4 != 0))
void* halloc(size_t size)
{
if (!halloc_start) {
halloc_start = (halloc_node_t*) DATA_SEGMENT_STOP_ADDR;
memset(halloc_start, 0, sizeof(halloc_node_t));
halloc_start->size = (MAX_HEAP_SIZE / 4) - 1;
}
size_t realsz = size_for(size); /* Clip the size to the nearest word. */
halloc_off_t offset = 0;
while (offset < (MAX_HEAP_SIZE / 4)) {
halloc_node_t* cur = halloc_node_at_off(offset);
if (!cur->used && (cur->size >= realsz)) {
cur->used = true;
size_t orig_size = cur->size;
cur->size = realsz;
if (orig_size > realsz) {
/* This halloc node needs to split into two blocks. */
halloc_node_t* next = halloc_node_next(cur);
next->used = 0;
next->size = orig_size - realsz - sizeof(halloc_node_t) / 4;
next->prev = offset;
halloc_node_t* nextnext = halloc_node_next(next);
if (halloc_node_get_off(nextnext) < (MAX_HEAP_SIZE / 4)) {
nextnext->prev = halloc_node_get_off(next);
}
}
return (void*) cur->mem;
}
offset += (sizeof(halloc_node_t) / 4) + cur->size;
}
return NULL;
}
/* Joins this node with the previous and next nodes if they're free. */
static void coalesce(halloc_node_t* cur)
{
if (cur->used) return;
halloc_node_t* next = halloc_node_next(cur);
if (!next->used) {
cur->size += next->size + sizeof(halloc_node_t) / 4;
}
if (cur != halloc_start) {
coalesce(halloc_node_prev(cur));
}
}
void hfree(void* mem)
{
/* TODO this should be a critical section. */
if (!mem) {
/* Consistent with C, freeing a NULL pointer does nothing. */
return;
}
halloc_node_t* header = ((halloc_node_t*) mem) - 1;
if (!header->used) {
#ifdef FOR_TESTING
assert(header->used);
#endif
return; // TODO make this fail on ARM.
}
header->used = 0;
coalesce(header);
}
#ifdef FOR_TESTING
#include <stdio.h>
void* debug_halloc_get_next_ptr(void* ptr)
{
halloc_node_t* node = ptr - sizeof(halloc_node_t);
halloc_node_t* next = halloc_node_next(node);
return next->mem;
}
void* debug_halloc_get_prev_ptr(void* ptr)
{
halloc_node_t* node = ptr - sizeof(halloc_node_t);
halloc_node_t* prev = halloc_node_prev(node);
return prev->mem;
}
/* Tests that we can walk up and down the allocated blocks and that they
* are properly aligned. */
int debug_halloc_assert_consistency(char* error, size_t len)
{
halloc_node_t* cur = halloc_node_at_off(0);
size_t total_size = 0;
size_t loop_check = 0;
while(1) {
total_size += cur->size + 1;
halloc_node_t* next = halloc_node_next(cur);
if ((uint8_t*) next == ((uint8_t*)&DATA_SEGMENT_STOP) + MAX_HEAP_SIZE) {
break;
} else if ((uint8_t*) next > (uint8_t*)DATA_SEGMENT_STOP_ADDR + MAX_HEAP_SIZE){
snprintf(
error, len, "Next node points is out of bounds. %p vs max of %p\n",
next,
(void*)(DATA_SEGMENT_STOP_ADDR + MAX_HEAP_SIZE));
return 1;
}
cur = next;
}
if (total_size * 4 != MAX_HEAP_SIZE) {
snprintf(
error, len, "Total recorded size is inconsistent. %lu vs %lu\n",
total_size * 4, MAX_HEAP_SIZE);
return 1;
}
while (loop_check < 10000) {
halloc_node_t* prev = halloc_node_prev(cur);
if (prev == halloc_start) {
return 0;
}
cur = prev;
++ loop_check;
}
snprintf(error, len, "Loop check failed.\n");
return 1;
}
#endif
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