X-Git-Url: https://git.kernel.dk/?p=fio.git;a=blobdiff_plain;f=smalloc.c;h=a2ad25a0a0d03bf5010c743325ed17e594e0fb83;hp=28f82633b23661c9e49f80612ac2c6d550c4fa8e;hb=fd98fb689d5ad7e9977461e961fff3fdd37f9cb8;hpb=adf57099338307b3a4a129475a12aad31e35ade3

diff --git a/smalloc.c b/smalloc.c
index 28f82633..a2ad25a0 100644
--- a/smalloc.c
+++ b/smalloc.c
@@ -3,294 +3,228 @@
  * that can be shared across processes and threads
  */
 #include <sys/mman.h>
-#include <stdio.h>
-#include <stdlib.h>
 #include <assert.h>
 #include <string.h>
-#include <unistd.h>
-#include <sys/types.h>
-#include <limits.h>
 
-#include "mutex.h"
+#include "fio.h"
+#include "fio_sem.h"
+#include "os/os.h"
+#include "smalloc.h"
+#include "log.h"
 
-#undef ENABLE_RESIZE		/* define to enable pool resizing */
-#define MP_SAFE			/* define to made allocator thread safe */
+#define SMALLOC_REDZONE		/* define to detect memory corruption */
 
-#define INITIAL_SIZE	1048576	/* new pool size */
-#define MAX_POOLS	32	/* maximum number of pools to setup */
+#define SMALLOC_BPB	32	/* block size, bytes-per-bit in bitmap */
+#define SMALLOC_BPI	(sizeof(unsigned int) * 8)
+#define SMALLOC_BPL	(SMALLOC_BPB * SMALLOC_BPI)
 
-unsigned int smalloc_pool_size = INITIAL_SIZE;
+#define INITIAL_SIZE	16*1024*1024	/* new pool size */
+#define INITIAL_POOLS	8		/* maximum number of pools to setup */
+
+#define MAX_POOLS	16
+
+#define SMALLOC_PRE_RED		0xdeadbeefU
+#define SMALLOC_POST_RED	0x5aa55aa5U
 
-#ifdef ENABLE_RESIZE
-#define MAX_SIZE	8 * smalloc_pool_size
-static unsigned int resize_error;
+unsigned int smalloc_pool_size = INITIAL_SIZE;
+#ifdef SMALLOC_REDZONE
+static const int int_mask = sizeof(int) - 1;
 #endif
 
 struct pool {
-	struct fio_mutex *lock;			/* protects this pool */
+	struct fio_sem *lock;			/* protects this pool */
 	void *map;				/* map of blocks */
-	void *last;				/* next free block hint */
-	unsigned int size;			/* size of pool */
-	unsigned int room;			/* size left in pool */
-	unsigned int largest_block;		/* largest block free */
-	unsigned int free_since_compact;	/* sfree() since compact() */
-	int fd;					/* memory backing fd */
-	char file[PATH_MAX];			/* filename for fd */
+	unsigned int *bitmap;			/* blocks free/busy map */
+	size_t free_blocks;		/* free blocks */
+	size_t nr_blocks;			/* total blocks */
+	size_t next_non_full;
+	size_t mmap_size;
+};
+
+struct block_hdr {
+	size_t size;
+#ifdef SMALLOC_REDZONE
+	unsigned int prered;
+#endif
 };
 
 static struct pool mp[MAX_POOLS];
 static unsigned int nr_pools;
 static unsigned int last_pool;
-static struct fio_mutex *lock;
 
-struct mem_hdr {
-	unsigned int size;
-};
-
-static inline void pool_lock(struct pool *pool)
+static inline int ptr_valid(struct pool *pool, void *ptr)
 {
-	if (pool->lock)
-		fio_mutex_down(pool->lock);
-}
+	unsigned int pool_size = pool->nr_blocks * SMALLOC_BPL;
 
-static inline void pool_unlock(struct pool *pool)
-{
-	if (pool->lock)
-		fio_mutex_up(pool->lock);
+	return (ptr >= pool->map) && (ptr < pool->map + pool_size);
 }
 
-static inline void global_read_lock(void)
+static inline size_t size_to_blocks(size_t size)
 {
-	if (lock)
-		fio_mutex_down_read(lock);
+	return (size + SMALLOC_BPB - 1) / SMALLOC_BPB;
 }
 
-static inline void global_read_unlock(void)
+static int blocks_iter(struct pool *pool, unsigned int pool_idx,
+		       unsigned int idx, size_t nr_blocks,
+		       int (*func)(unsigned int *map, unsigned int mask))
 {
-	if (lock)
-		fio_mutex_up_read(lock);
-}
 
-static inline void global_write_lock(void)
-{
-	if (lock)
-		fio_mutex_down_write(lock);
-}
+	while (nr_blocks) {
+		unsigned int this_blocks, mask;
+		unsigned int *map;
 
-static inline void global_write_unlock(void)
-{
-	if (lock)
-		fio_mutex_up_write(lock);
-}
+		if (pool_idx >= pool->nr_blocks)
+			return 0;
 
-#define hdr_free(hdr)		((hdr)->size & 0x80000000)
-#define hdr_size(hdr)		((hdr)->size & ~0x80000000)
-#define hdr_mark_free(hdr)	((hdr)->size |= 0x80000000)
+		map = &pool->bitmap[pool_idx];
 
-static inline int ptr_valid(struct pool *pool, void *ptr)
-{
-	return (ptr >= pool->map) && (ptr < pool->map + pool->size);
-}
+		this_blocks = nr_blocks;
+		if (this_blocks + idx > SMALLOC_BPI) {
+			this_blocks = SMALLOC_BPI - idx;
+			idx = SMALLOC_BPI - this_blocks;
+		}
 
-static inline int __hdr_valid(struct pool *pool, struct mem_hdr *hdr,
-			      unsigned int size)
-{
-	return ptr_valid(pool, hdr) && ptr_valid(pool, (void *) hdr + size - 1);
+		if (this_blocks == SMALLOC_BPI)
+			mask = -1U;
+		else
+			mask = ((1U << this_blocks) - 1) << idx;
+
+		if (!func(map, mask))
+			return 0;
+
+		nr_blocks -= this_blocks;
+		idx = 0;
+		pool_idx++;
+	}
+
+	return 1;
 }
 
-static inline int hdr_valid(struct pool *pool, struct mem_hdr *hdr)
+static int mask_cmp(unsigned int *map, unsigned int mask)
 {
-	return __hdr_valid(pool, hdr, hdr_size(hdr));
+	return !(*map & mask);
 }
 
-static inline int region_free(struct mem_hdr *hdr)
+static int mask_clear(unsigned int *map, unsigned int mask)
 {
-	return hdr_free(hdr) || (!hdr_free(hdr) && !hdr_size(hdr));
+	assert((*map & mask) == mask);
+	*map &= ~mask;
+	return 1;
 }
 
-static inline struct mem_hdr *__hdr_nxt(struct pool *pool, struct mem_hdr *hdr,
-					unsigned int size)
+static int mask_set(unsigned int *map, unsigned int mask)
 {
-	struct mem_hdr *nxt = (void *) hdr + size + sizeof(*hdr);
-
-	if (__hdr_valid(pool, nxt, size))
-		return nxt;
-
-	return NULL;
+	assert(!(*map & mask));
+	*map |= mask;
+	return 1;
 }
 
-static inline struct mem_hdr *hdr_nxt(struct pool *pool, struct mem_hdr *hdr)
+static int blocks_free(struct pool *pool, unsigned int pool_idx,
+		       unsigned int idx, size_t nr_blocks)
 {
-	return __hdr_nxt(pool, hdr, hdr_size(hdr));
+	return blocks_iter(pool, pool_idx, idx, nr_blocks, mask_cmp);
 }
 
-static void merge(struct pool *pool, struct mem_hdr *hdr, struct mem_hdr *nxt)
+static void set_blocks(struct pool *pool, unsigned int pool_idx,
+		       unsigned int idx, size_t nr_blocks)
 {
-	unsigned int hfree = hdr_free(hdr);
-	unsigned int nfree = hdr_free(nxt);
-
-	hdr->size = hdr_size(hdr) + hdr_size(nxt) + sizeof(*nxt);
-	nxt->size = 0;
-
-	if (hfree)
-		hdr_mark_free(hdr);
-	if (nfree)
-		hdr_mark_free(nxt);
-
-	if (pool->last == nxt)
-		pool->last = hdr;
+	blocks_iter(pool, pool_idx, idx, nr_blocks, mask_set);
 }
 
-static int combine(struct pool *pool, struct mem_hdr *prv, struct mem_hdr *hdr)
+static void clear_blocks(struct pool *pool, unsigned int pool_idx,
+			 unsigned int idx, size_t nr_blocks)
 {
-	if (prv && hdr_free(prv) && hdr_free(hdr)) {
-		merge(pool, prv, hdr);
-		return 1;
-	}
-
-	return 0;
+	blocks_iter(pool, pool_idx, idx, nr_blocks, mask_clear);
 }
 
-static int compact_pool(struct pool *pool)
+static int find_next_zero(int word, int start)
 {
-	struct mem_hdr *hdr = pool->map, *nxt;
-	unsigned int compacted = 0;
-
-	if (pool->free_since_compact < 50)
-		return 1;
-
-	while (hdr) {
-		nxt = hdr_nxt(pool, hdr);
-		if (!nxt)
-			break;
-		if (hdr_free(nxt) && hdr_free(hdr)) {
-			merge(pool, hdr, nxt);
-			compacted++;
-			continue;
-		}
-		hdr = hdr_nxt(pool, hdr);
-	}
-
-	pool->free_since_compact = 0;
-	return !!compacted;
+	assert(word != -1U);
+	word >>= start;
+	return ffz(word) + start;
 }
 
-static int resize_pool(struct pool *pool)
+static bool add_pool(struct pool *pool, unsigned int alloc_size)
 {
-#ifdef ENABLE_RESIZE
-	unsigned int new_size = pool->size << 1;
-	struct mem_hdr *hdr, *last_hdr;
+	int bitmap_blocks;
+	int mmap_flags;
 	void *ptr;
 
-	if (new_size >= MAX_SIZE || resize_error)
-		return 1;
-
-	if (ftruncate(pool->fd, new_size) < 0)
-		goto fail;
+	if (nr_pools == MAX_POOLS)
+		return false;
 
-	ptr = mremap(pool->map, pool->size, new_size, 0);
-	if (ptr == MAP_FAILED)
-		goto fail;
-
-	pool->map = ptr;
-	hdr = pool;
-	do {
-		last_hdr = hdr;
-	} while ((hdr = hdr_nxt(hdr)) != NULL);
-
-	if (hdr_free(last_hdr)) {
-		last_hdr->size = hdr_size(last_hdr) + new_size - pool_size;
-		hdr_mark_free(last_hdr);
-	} else {
-		struct mem_hdr *nxt;
-
-		nxt = (void *) last_hdr + hdr_size(last_hdr) + sizeof(*hdr);
-		nxt->size = new_size - pool_size - sizeof(*hdr);
-		hdr_mark_free(nxt);
-	}
-
-	pool_room += new_size - pool_size;
-	pool_size = new_size;
-	return 0;
-fail:
-	perror("resize");
-	resize_error = 1;
+#ifdef SMALLOC_REDZONE
+	alloc_size += sizeof(unsigned int);
+#endif
+	alloc_size += sizeof(struct block_hdr);
+	if (alloc_size < INITIAL_SIZE)
+		alloc_size = INITIAL_SIZE;
+
+	/* round up to nearest full number of blocks */
+	alloc_size = (alloc_size + SMALLOC_BPL - 1) & ~(SMALLOC_BPL - 1);
+	bitmap_blocks = alloc_size / SMALLOC_BPL;
+	alloc_size += bitmap_blocks * sizeof(unsigned int);
+	pool->mmap_size = alloc_size;
+
+	pool->nr_blocks = bitmap_blocks;
+	pool->free_blocks = bitmap_blocks * SMALLOC_BPB;
+
+	mmap_flags = OS_MAP_ANON;
+#ifdef CONFIG_ESX
+	mmap_flags |= MAP_PRIVATE;
 #else
-	return 1;
+	mmap_flags |= MAP_SHARED;
 #endif
-}
-
-static int add_pool(struct pool *pool, unsigned int alloc_size)
-{
-	struct mem_hdr *hdr;
-	void *ptr;
-	int fd;
+	ptr = mmap(NULL, alloc_size, PROT_READ|PROT_WRITE, mmap_flags, -1, 0);
 
-	strcpy(pool->file, "/tmp/.fio_smalloc.XXXXXX");
-	fd = mkstemp(pool->file);
-	if (fd < 0)
-		goto out_close;
-
-	if (alloc_size > smalloc_pool_size)
-		pool->size = alloc_size;
-	else
-		pool->size = smalloc_pool_size;
-
-	if (ftruncate(fd, pool->size) < 0)
-		goto out_unlink;
-
-	ptr = mmap(NULL, pool->size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
 	if (ptr == MAP_FAILED)
-		goto out_unlink;
+		goto out_fail;
 
-	memset(ptr, 0, pool->size);
-	pool->map = pool->last = ptr;
+	pool->map = ptr;
+	pool->bitmap = (unsigned int *)((char *) ptr + (pool->nr_blocks * SMALLOC_BPL));
+	memset(pool->bitmap, 0, bitmap_blocks * sizeof(unsigned int));
 
-#ifdef MP_SAFE
-	pool->lock = fio_mutex_init(1);
+	pool->lock = fio_sem_init(FIO_SEM_UNLOCKED);
 	if (!pool->lock)
-		goto out_unlink;
-#endif
-
-	pool->fd = fd;
+		goto out_fail;
 
-	hdr = pool->map;
-	pool->room = hdr->size = pool->size - sizeof(*hdr);
-	pool->largest_block = pool->room;
-	hdr_mark_free(hdr);
-	global_write_lock();
 	nr_pools++;
-	global_write_unlock();
-	return 0;
-out_unlink:
+	return true;
+out_fail:
+	log_err("smalloc: failed adding pool\n");
 	if (pool->map)
-		munmap(pool->map, pool->size);
-	unlink(pool->file);
-out_close:
-	if (fd >= 0)
-		close(fd);
-	return 1;
+		munmap(pool->map, pool->mmap_size);
+	return false;
 }
 
 void sinit(void)
 {
-	int ret;
+	bool ret;
+	int i;
 
-#ifdef MP_SAFE
-	lock = fio_mutex_rw_init();
-#endif
-	ret = add_pool(&mp[0], INITIAL_SIZE);
-	assert(!ret);
+	for (i = 0; i < INITIAL_POOLS; i++) {
+		ret = add_pool(&mp[nr_pools], smalloc_pool_size);
+		if (!ret)
+			break;
+	}
+
+	/*
+	 * If we added at least one pool, we should be OK for most
+	 * cases.
+	 */
+	assert(i);
 }
 
 static void cleanup_pool(struct pool *pool)
 {
-	unlink(pool->file);
-	close(pool->fd);
-	munmap(pool->map, pool->size);
+	/*
+	 * This will also remove the temporary file we used as a backing
+	 * store, it was already unlinked
+	 */
+	munmap(pool->map, pool->mmap_size);
 
 	if (pool->lock)
-		fio_mutex_remove(pool->lock);
+		fio_sem_remove(pool->lock);
 }
 
 void scleanup(void)
@@ -299,35 +233,80 @@ void scleanup(void)
 
 	for (i = 0; i < nr_pools; i++)
 		cleanup_pool(&mp[i]);
+}
+
+#ifdef SMALLOC_REDZONE
+static void *postred_ptr(struct block_hdr *hdr)
+{
+	uintptr_t ptr;
+
+	ptr = (uintptr_t) hdr + hdr->size - sizeof(unsigned int);
+	ptr = (uintptr_t) PTR_ALIGN(ptr, int_mask);
+
+	return (void *) ptr;
+}
+
+static void fill_redzone(struct block_hdr *hdr)
+{
+	unsigned int *postred = postred_ptr(hdr);
 
-	if (lock)
-		fio_mutex_remove(lock);
+	hdr->prered = SMALLOC_PRE_RED;
+	*postred = SMALLOC_POST_RED;
+}
+
+static void sfree_check_redzone(struct block_hdr *hdr)
+{
+	unsigned int *postred = postred_ptr(hdr);
+
+	if (hdr->prered != SMALLOC_PRE_RED) {
+		log_err("smalloc pre redzone destroyed!\n"
+			" ptr=%p, prered=%x, expected %x\n",
+				hdr, hdr->prered, SMALLOC_PRE_RED);
+		assert(0);
+	}
+	if (*postred != SMALLOC_POST_RED) {
+		log_err("smalloc post redzone destroyed!\n"
+			"  ptr=%p, postred=%x, expected %x\n",
+				hdr, *postred, SMALLOC_POST_RED);
+		assert(0);
+	}
+}
+#else
+static void fill_redzone(struct block_hdr *hdr)
+{
 }
 
+static void sfree_check_redzone(struct block_hdr *hdr)
+{
+}
+#endif
+
 static void sfree_pool(struct pool *pool, void *ptr)
 {
-	struct mem_hdr *hdr, *nxt;
+	struct block_hdr *hdr;
+	unsigned int i, idx;
+	unsigned long offset;
 
 	if (!ptr)
 		return;
 
-	assert(ptr_valid(pool, ptr));
+	ptr -= sizeof(*hdr);
+	hdr = ptr;
 
-	pool_lock(pool);
-	hdr = ptr - sizeof(*hdr);
-	assert(!hdr_free(hdr));
-	hdr_mark_free(hdr);
-	pool->room -= hdr_size(hdr);
+	assert(ptr_valid(pool, ptr));
 
-	nxt = hdr_nxt(pool, hdr);
-	if (nxt && hdr_free(nxt))
-		merge(pool, hdr, nxt);
+	sfree_check_redzone(hdr);
 
-	if (hdr_size(hdr) > pool->largest_block)
-		pool->largest_block = hdr_size(hdr);
+	offset = ptr - pool->map;
+	i = offset / SMALLOC_BPL;
+	idx = (offset % SMALLOC_BPL) / SMALLOC_BPB;
 
-	pool->free_since_compact++;
-	pool_unlock(pool);
+	fio_sem_down(pool->lock);
+	clear_blocks(pool, i, idx, size_to_blocks(hdr->size));
+	if (i < pool->next_non_full)
+		pool->next_non_full = i;
+	pool->free_blocks += size_to_blocks(hdr->size);
+	fio_sem_up(pool->lock);
 }
 
 void sfree(void *ptr)
@@ -335,7 +314,8 @@ void sfree(void *ptr)
 	struct pool *pool = NULL;
 	unsigned int i;
 
-	global_read_lock();
+	if (!ptr)
+		return;
 
 	for (i = 0; i < nr_pools; i++) {
 		if (ptr_valid(&mp[i], ptr)) {
@@ -344,140 +324,141 @@ void sfree(void *ptr)
 		}
 	}
 
-	global_read_unlock();
+	if (pool) {
+		sfree_pool(pool, ptr);
+		return;
+	}
 
-	assert(pool);
-	sfree_pool(pool, ptr);
+	log_err("smalloc: ptr %p not from smalloc pool\n", ptr);
 }
 
-static void *smalloc_pool(struct pool *pool, unsigned int size)
+static void *__smalloc_pool(struct pool *pool, size_t size)
 {
-	struct mem_hdr *hdr, *prv;
-	int did_restart = 0;
-	void *ret;
-
-	/*
-	 * slight chance of race with sfree() here, but acceptable
-	 */
-	if (!size || size > pool->room + sizeof(*hdr) ||
-	    ((size > pool->largest_block) && pool->largest_block))
-		return NULL;
+	size_t nr_blocks;
+	unsigned int i;
+	unsigned int offset;
+	unsigned int last_idx;
+	void *ret = NULL;
 
-	pool_lock(pool);
-restart:
-	hdr = pool->last;
-	prv = NULL;
-	do {
-		if (combine(pool, prv, hdr))
-			hdr = prv;
+	fio_sem_down(pool->lock);
 
-		if (hdr_free(hdr) && hdr_size(hdr) >= size)
-			break;
+	nr_blocks = size_to_blocks(size);
+	if (nr_blocks > pool->free_blocks)
+		goto fail;
 
-		prv = hdr;
-	} while ((hdr = hdr_nxt(pool, hdr)) != NULL);
+	i = pool->next_non_full;
+	last_idx = 0;
+	offset = -1U;
+	while (i < pool->nr_blocks) {
+		unsigned int idx;
 
-	if (!hdr)
-		goto fail;
+		if (pool->bitmap[i] == -1U) {
+			i++;
+			pool->next_non_full = i;
+			last_idx = 0;
+			continue;
+		}
 
-	/*
-	 * more room, adjust next header if any
-	 */
-	if (hdr_size(hdr) - size >= 2 * sizeof(*hdr)) {
-		struct mem_hdr *nxt = __hdr_nxt(pool, hdr, size);
-
-		if (nxt) {
-			nxt->size = hdr_size(hdr) - size - sizeof(*hdr);
-			if (hdr_size(hdr) == pool->largest_block)
-				pool->largest_block = hdr_size(nxt);
-			hdr_mark_free(nxt);
-		} else
-			size = hdr_size(hdr);
-	} else
-		size = hdr_size(hdr);
-
-	if (size == hdr_size(hdr) && size == pool->largest_block)
-		pool->largest_block = 0;
+		idx = find_next_zero(pool->bitmap[i], last_idx);
+		if (!blocks_free(pool, i, idx, nr_blocks)) {
+			idx += nr_blocks;
+			if (idx < SMALLOC_BPI)
+				last_idx = idx;
+			else {
+				last_idx = 0;
+				while (idx >= SMALLOC_BPI) {
+					i++;
+					idx -= SMALLOC_BPI;
+				}
+			}
+			continue;
+		}
+		set_blocks(pool, i, idx, nr_blocks);
+		offset = i * SMALLOC_BPL + idx * SMALLOC_BPB;
+		break;
+	}
 
-	/*
-	 * also clears free bit
-	 */
-	hdr->size = size;
-	pool->last = hdr_nxt(pool, hdr);
-	if (!pool->last)
-		pool->last = pool->map;
-	pool->room -= size;
-	pool_unlock(pool);
-
-	ret = (void *) hdr + sizeof(*hdr);
-	memset(ret, 0, size);
-	return ret;
+	if (i < pool->nr_blocks) {
+		pool->free_blocks -= nr_blocks;
+		ret = pool->map + offset;
+	}
 fail:
+	fio_sem_up(pool->lock);
+	return ret;
+}
+
+static void *smalloc_pool(struct pool *pool, size_t size)
+{
+	size_t alloc_size = size + sizeof(struct block_hdr);
+	void *ptr;
+
 	/*
-	 * if we fail to allocate, first compact the entries that we missed.
-	 * if that also fails, increase the size of the pool
+	 * Round to int alignment, so that the postred pointer will
+	 * be naturally aligned as well.
 	 */
-	++did_restart;
-	if (did_restart <= 1) {
-		if (!compact_pool(pool)) {
-			pool->last = pool->map;
-			goto restart;
-		}
-	}
-	++did_restart;
-	if (did_restart <= 2) {
-		if (!resize_pool(pool)) {
-			pool->last = pool->map;
-			goto restart;
-		}
+#ifdef SMALLOC_REDZONE
+	alloc_size += sizeof(unsigned int);
+	alloc_size = (alloc_size + int_mask) & ~int_mask;
+#endif
+
+	ptr = __smalloc_pool(pool, alloc_size);
+	if (ptr) {
+		struct block_hdr *hdr = ptr;
+
+		hdr->size = alloc_size;
+		fill_redzone(hdr);
+
+		ptr += sizeof(*hdr);
+		memset(ptr, 0, size);
 	}
-	pool_unlock(pool);
-	return NULL;
+
+	return ptr;
 }
 
-void *smalloc(unsigned int size)
+void *smalloc(size_t size)
 {
-	unsigned int i;
+	unsigned int i, end_pool;
+
+	if (size != (unsigned int) size)
+		return NULL;
 
-	global_read_lock();
 	i = last_pool;
+	end_pool = nr_pools;
 
 	do {
-		for (; i < nr_pools; i++) {
+		for (; i < end_pool; i++) {
 			void *ptr = smalloc_pool(&mp[i], size);
 
 			if (ptr) {
 				last_pool = i;
-				global_read_unlock();
 				return ptr;
 			}
 		}
 		if (last_pool) {
-			last_pool = 0;
+			end_pool = last_pool;
+			last_pool = i = 0;
 			continue;
 		}
 
-		if (nr_pools + 1 >= MAX_POOLS)
-			break;
-		else {
-			i = nr_pools;
-			global_read_unlock();
-			if (add_pool(&mp[nr_pools], size))
-				goto out;
-			global_read_lock();
-		}
+		break;
 	} while (1);
 
-	global_read_unlock();
-out:
+	log_err("smalloc: OOM. Consider using --alloc-size to increase the "
+		"shared memory available.\n");
 	return NULL;
 }
 
+void *scalloc(size_t nmemb, size_t size)
+{
+	return smalloc(nmemb * size);
+}
+
 char *smalloc_strdup(const char *str)
 {
-	char *ptr;
+	char *ptr = NULL;
 
 	ptr = smalloc(strlen(str) + 1);
-	strcpy(ptr, str);
+	if (ptr)
+		strcpy(ptr, str);
 	return ptr;
 }