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https://gitlab.torproject.org/tpo/core/tor.git
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memarea.c: use flexible array member for mem
This make clang's memory sanitizer happier that we aren't reading off the end of a char[1]. We hadn't replaced the char[1] with a char[FLEXIBLE_ARRAY_MEMBER] before because we were doing a union trick to force alignment. Now we use __attribute__(aligned) where available, and we do the union trick elsewhere. Most of this patch is just replacing accesses to (x)->u.mem with (x)->U_MEM, where U_MEM is defined as "u.mem" or "mem" depending on our implementation.
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@ -29,6 +29,13 @@
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#error "void* is neither 4 nor 8 bytes long. I don't know how to align stuff."
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#endif
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#if defined(__GNUC__) && defined(FLEXIBLE_ARRAY_MEMBER)
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#define USE_ALIGNED_ATTRIBUTE
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#define U_MEM mem
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#else
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#define U_MEM u.mem
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#endif
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#ifdef USE_SENTINELS
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/** Magic value that we stick at the end of a memarea so we can make sure
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* there are no run-off-the-end bugs. */
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@ -39,12 +46,12 @@
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* end, set those bytes. */
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#define SET_SENTINEL(chunk) \
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STMT_BEGIN \
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set_uint32( &(chunk)->u.mem[chunk->mem_size], SENTINEL_VAL ); \
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set_uint32( &(chunk)->U_MEM[chunk->mem_size], SENTINEL_VAL ); \
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STMT_END
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/** Assert that the sentinel on a memarea is set correctly. */
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#define CHECK_SENTINEL(chunk) \
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STMT_BEGIN \
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uint32_t sent_val = get_uint32(&(chunk)->u.mem[chunk->mem_size]); \
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uint32_t sent_val = get_uint32(&(chunk)->U_MEM[chunk->mem_size]); \
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tor_assert(sent_val == SENTINEL_VAL); \
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STMT_END
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#else
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@ -71,19 +78,23 @@ realign_pointer(void *ptr)
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typedef struct memarea_chunk_t {
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/** Next chunk in this area. Only kept around so we can free it. */
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struct memarea_chunk_t *next_chunk;
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size_t mem_size; /**< How much RAM is available in u.mem, total? */
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char *next_mem; /**< Next position in u.mem to allocate data at. If it's
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size_t mem_size; /**< How much RAM is available in mem, total? */
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char *next_mem; /**< Next position in mem to allocate data at. If it's
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* greater than or equal to mem+mem_size, this chunk is
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* full. */
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#ifdef USE_ALIGNED_ATTRIBUTE
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char mem[FLEXIBLE_ARRAY_MEMBER] __attribute__((aligned(MEMAREA_ALIGN)));
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#else
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union {
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char mem[1]; /**< Memory space in this chunk. */
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void *void_for_alignment_; /**< Dummy; used to make sure mem is aligned. */
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} u;
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#endif
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} memarea_chunk_t;
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/** How many bytes are needed for overhead before we get to the memory part
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* of a chunk? */
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#define CHUNK_HEADER_SIZE STRUCT_OFFSET(memarea_chunk_t, u)
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#define CHUNK_HEADER_SIZE STRUCT_OFFSET(memarea_chunk_t, U_MEM)
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/** What's the smallest that we'll allocate a chunk? */
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#define CHUNK_SIZE 4096
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@ -121,7 +132,7 @@ alloc_chunk(size_t sz, int freelist_ok)
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res = tor_malloc(chunk_size);
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res->next_chunk = NULL;
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res->mem_size = chunk_size - CHUNK_HEADER_SIZE - SENTINEL_LEN;
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res->next_mem = res->u.mem;
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res->next_mem = res->U_MEM;
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tor_assert(res->next_mem+res->mem_size+SENTINEL_LEN ==
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((char*)res)+chunk_size);
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tor_assert(realign_pointer(res->next_mem) == res->next_mem);
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@ -140,7 +151,7 @@ chunk_free_unchecked(memarea_chunk_t *chunk)
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++freelist_len;
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chunk->next_chunk = freelist;
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freelist = chunk;
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chunk->next_mem = chunk->u.mem;
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chunk->next_mem = chunk->U_MEM;
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} else {
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tor_free(chunk);
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}
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@ -183,7 +194,7 @@ memarea_clear(memarea_t *area)
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}
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area->first->next_chunk = NULL;
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}
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area->first->next_mem = area->first->u.mem;
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area->first->next_mem = area->first->U_MEM;
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}
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/** Remove all unused memarea chunks from the internal freelist. */
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@ -207,7 +218,7 @@ memarea_owns_ptr(const memarea_t *area, const void *p)
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memarea_chunk_t *chunk;
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const char *ptr = p;
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for (chunk = area->first; chunk; chunk = chunk->next_chunk) {
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if (ptr >= chunk->u.mem && ptr < chunk->next_mem)
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if (ptr >= chunk->U_MEM && ptr < chunk->next_mem)
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return 1;
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}
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return 0;
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@ -226,7 +237,7 @@ memarea_alloc(memarea_t *area, size_t sz)
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tor_assert(sz < SIZE_T_CEILING);
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if (sz == 0)
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sz = 1;
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if (chunk->next_mem+sz > chunk->u.mem+chunk->mem_size) {
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if (chunk->next_mem+sz > chunk->U_MEM+chunk->mem_size) {
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if (sz+CHUNK_HEADER_SIZE >= CHUNK_SIZE) {
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/* This allocation is too big. Stick it in a special chunk, and put
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* that chunk second in the list. */
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@ -244,8 +255,8 @@ memarea_alloc(memarea_t *area, size_t sz)
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result = chunk->next_mem;
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chunk->next_mem = chunk->next_mem + sz;
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/* Reinstate these if bug 930 ever comes back
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tor_assert(chunk->next_mem >= chunk->u.mem);
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tor_assert(chunk->next_mem <= chunk->u.mem+chunk->mem_size);
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tor_assert(chunk->next_mem >= chunk->U_MEM);
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tor_assert(chunk->next_mem <= chunk->U_MEM+chunk->mem_size);
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*/
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chunk->next_mem = realign_pointer(chunk->next_mem);
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return result;
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@ -304,8 +315,8 @@ memarea_get_stats(memarea_t *area, size_t *allocated_out, size_t *used_out)
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for (chunk = area->first; chunk; chunk = chunk->next_chunk) {
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CHECK_SENTINEL(chunk);
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a += CHUNK_HEADER_SIZE + chunk->mem_size;
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tor_assert(chunk->next_mem >= chunk->u.mem);
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u += CHUNK_HEADER_SIZE + (chunk->next_mem - chunk->u.mem);
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tor_assert(chunk->next_mem >= chunk->U_MEM);
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u += CHUNK_HEADER_SIZE + (chunk->next_mem - chunk->U_MEM);
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}
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*allocated_out = a;
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*used_out = u;
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@ -320,9 +331,9 @@ memarea_assert_ok(memarea_t *area)
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for (chunk = area->first; chunk; chunk = chunk->next_chunk) {
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CHECK_SENTINEL(chunk);
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tor_assert(chunk->next_mem >= chunk->u.mem);
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tor_assert(chunk->next_mem >= chunk->U_MEM);
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tor_assert(chunk->next_mem <=
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(char*) realign_pointer(chunk->u.mem+chunk->mem_size));
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(char*) realign_pointer(chunk->U_MEM+chunk->mem_size));
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}
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}
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