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![Jessica Clarke](/assets/img/avatar_default.png)
mem_pool_alloc uses sizeof(uintmax_t) as a proxy for what should be _Alignof(max_align_t) in C11. On most architectures this is sufficient (though on m68k it is in fact overly strict, since the de-facto ABI, which differs from the specified System V ABI, has the maximum alignment of all types as 2 bytes), but on CHERI, and thus Arm's Morello prototype, it is insufficient for any type that stores a pointer, which must be aligned to 128 bits (on 64-bit architectures extended with CHERI), whilst uintmax_t is a 64-bit integer. Fix this by introducing our own approximation for max_align_t and a means to compute _Alignof it without relying on C11. Currently this union only contains uintmax_t and void *, but more types can be added as needed. Signed-off-by: Jessica Clarke <jrtc27@jrtc27.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
179 lines
4.2 KiB
C
179 lines
4.2 KiB
C
/*
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* Memory Pool implementation logic.
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*/
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#include "cache.h"
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#include "mem-pool.h"
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#define BLOCK_GROWTH_SIZE (1024 * 1024 - sizeof(struct mp_block))
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/*
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* The inner union is an approximation for C11's max_align_t, and the
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* struct + offsetof computes _Alignof. This can all just be replaced
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* with _Alignof(max_align_t) if/when C11 is part of the baseline.
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* Note that _Alignof(X) need not be the same as sizeof(X); it's only
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* required to be a (possibly trivial) factor. They are the same for
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* most architectures, but m68k for example has only 2-byte alignment
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* for its 4-byte and 8-byte types, so using sizeof would waste space.
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*
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* Add more types to the union if the current set is insufficient.
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*/
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struct git_max_alignment {
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char unalign;
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union {
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uintmax_t max_align_uintmax;
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void *max_align_pointer;
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} aligned;
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};
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#define GIT_MAX_ALIGNMENT offsetof(struct git_max_alignment, aligned)
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/*
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* Allocate a new mp_block and insert it after the block specified in
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* `insert_after`. If `insert_after` is NULL, then insert block at the
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* head of the linked list.
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*/
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static struct mp_block *mem_pool_alloc_block(struct mem_pool *pool,
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size_t block_alloc,
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struct mp_block *insert_after)
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{
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struct mp_block *p;
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pool->pool_alloc += sizeof(struct mp_block) + block_alloc;
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p = xmalloc(st_add(sizeof(struct mp_block), block_alloc));
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p->next_free = (char *)p->space;
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p->end = p->next_free + block_alloc;
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if (insert_after) {
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p->next_block = insert_after->next_block;
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insert_after->next_block = p;
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} else {
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p->next_block = pool->mp_block;
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pool->mp_block = p;
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}
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return p;
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}
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void mem_pool_init(struct mem_pool *pool, size_t initial_size)
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{
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memset(pool, 0, sizeof(*pool));
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pool->block_alloc = BLOCK_GROWTH_SIZE;
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if (initial_size > 0)
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mem_pool_alloc_block(pool, initial_size, NULL);
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}
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void mem_pool_discard(struct mem_pool *pool, int invalidate_memory)
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{
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struct mp_block *block, *block_to_free;
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block = pool->mp_block;
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while (block)
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{
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block_to_free = block;
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block = block->next_block;
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if (invalidate_memory)
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memset(block_to_free->space, 0xDD, ((char *)block_to_free->end) - ((char *)block_to_free->space));
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free(block_to_free);
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}
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pool->mp_block = NULL;
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pool->pool_alloc = 0;
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}
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void *mem_pool_alloc(struct mem_pool *pool, size_t len)
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{
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struct mp_block *p = NULL;
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void *r;
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/* round up to a 'GIT_MAX_ALIGNMENT' alignment */
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if (len & (GIT_MAX_ALIGNMENT - 1))
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len += GIT_MAX_ALIGNMENT - (len & (GIT_MAX_ALIGNMENT - 1));
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if (pool->mp_block &&
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pool->mp_block->end - pool->mp_block->next_free >= len)
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p = pool->mp_block;
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if (!p) {
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if (len >= (pool->block_alloc / 2))
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return mem_pool_alloc_block(pool, len, pool->mp_block);
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p = mem_pool_alloc_block(pool, pool->block_alloc, NULL);
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}
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r = p->next_free;
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p->next_free += len;
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return r;
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}
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void *mem_pool_calloc(struct mem_pool *pool, size_t count, size_t size)
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{
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size_t len = st_mult(count, size);
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void *r = mem_pool_alloc(pool, len);
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memset(r, 0, len);
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return r;
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}
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char *mem_pool_strdup(struct mem_pool *pool, const char *str)
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{
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size_t len = strlen(str) + 1;
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char *ret = mem_pool_alloc(pool, len);
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return memcpy(ret, str, len);
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}
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char *mem_pool_strndup(struct mem_pool *pool, const char *str, size_t len)
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{
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char *p = memchr(str, '\0', len);
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size_t actual_len = (p ? p - str : len);
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char *ret = mem_pool_alloc(pool, actual_len+1);
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ret[actual_len] = '\0';
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return memcpy(ret, str, actual_len);
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}
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int mem_pool_contains(struct mem_pool *pool, void *mem)
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{
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struct mp_block *p;
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/* Check if memory is allocated in a block */
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for (p = pool->mp_block; p; p = p->next_block)
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if ((mem >= ((void *)p->space)) &&
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(mem < ((void *)p->end)))
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return 1;
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return 0;
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}
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void mem_pool_combine(struct mem_pool *dst, struct mem_pool *src)
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{
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struct mp_block *p;
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/* Append the blocks from src to dst */
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if (dst->mp_block && src->mp_block) {
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/*
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* src and dst have blocks, append
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* blocks from src to dst.
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*/
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p = dst->mp_block;
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while (p->next_block)
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p = p->next_block;
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p->next_block = src->mp_block;
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} else if (src->mp_block) {
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/*
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* src has blocks, dst is empty.
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*/
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dst->mp_block = src->mp_block;
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} else {
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/* src is empty, nothing to do. */
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}
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dst->pool_alloc += src->pool_alloc;
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src->pool_alloc = 0;
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src->mp_block = NULL;
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}
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