diff --git a/bwa.h b/bwa.h
index 5d40aae..6fcc82e 100644
--- a/bwa.h
+++ b/bwa.h
@@ -10,8 +10,7 @@
 #define BWA_IDX_PAC 0x4
 #define BWA_IDX_ALL 0x7
 
-#define BWA_SHM_KEY  5291
-#define BWA_SHM_SIZE 0x10000
+#define BWA_CTL_SIZE 0x10000
 
 typedef struct {
 	bwt_t    *bwt; // FM-index
diff --git a/bwashm.c b/bwashm.c
new file mode 100644
index 0000000..683d608
--- /dev/null
+++ b/bwashm.c
@@ -0,0 +1,169 @@
+#include <sys/types.h>
+#include <sys/mman.h>
+#include <string.h>
+#include <stdlib.h>
+#include <limits.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <stdio.h>
+#include "bwa.h"
+
+int bwa_shm_stage(bwaidx_t *idx, const char *hint)
+{
+	const char *name;
+	uint8_t *shm, *shm_idx;
+	uint16_t *cnt, i;
+	int shmid, to_init = 0, l;
+	char path[PATH_MAX + 1], *p;
+
+	if (hint == 0 || hint[0] == 0) return -1;
+	for (name = hint + strlen(hint) - 1; name >= hint && *name != '/'; --name);
+	++name;
+
+	if ((shmid = shm_open("/bwactl", O_RDWR, 0444)) < 0) {
+		shmid = shm_open("/bwactl", O_CREAT|O_RDWR|O_EXCL, 0644);
+		to_init = 1;
+	}
+	if (shmid < 0) return -1;
+	ftruncate(shmid, BWA_CTL_SIZE);
+	shm = mmap(0, BWA_CTL_SIZE, PROT_READ|PROT_WRITE, MAP_SHARED, shmid, 0);
+	cnt = (uint16_t*)shm;
+	if (to_init) {
+		memset(shm, 0, BWA_CTL_SIZE);
+		cnt[1] = 4;
+	} else {
+		for (i = 0, p = (char*)shm + 4; i < cnt[0]; ++i) {
+			if (strcmp(p + 8, name) == 0) break;
+			p += 9 + strlen(p + 8);
+		}
+		if (i < cnt[0]) {
+			fprintf(stderr, "[W::%s] index '%s' is already in shared memory\n", __func__, name);
+			return -1;
+		}
+	}
+
+	if (idx->mem == 0) bwa_idx2mem(idx);
+
+	strcat(strcpy(path, "/bwaidx-"), name);
+	l = 8 + strlen(name) + 1;
+	if (cnt[1] + l > BWA_CTL_SIZE) return -1;
+	memcpy(shm + cnt[1], &idx->l_mem, 8);
+	memcpy(shm + cnt[1] + 8, name, l - 8);
+	if ((shmid = shm_open(path, O_CREAT|O_RDWR|O_EXCL, 0644)) < 0) {
+		shm_unlink(path);
+		perror("shm_open()");
+		return -1;
+	}
+	cnt[1] += l; ++cnt[0];
+	ftruncate(shmid, idx->l_mem);
+	shm_idx = mmap(0, idx->l_mem, PROT_READ|PROT_WRITE, MAP_SHARED, shmid, 0);
+	memcpy(shm_idx, idx->mem, idx->l_mem);
+	free(idx->mem);
+	idx->mem = shm_idx;
+	idx->is_shm = 1;
+	return 0;
+}
+
+bwaidx_t *bwa_idx_load_from_shm(const char *hint)
+{
+	const char *name;
+	uint8_t *shm, *shm_idx;
+	uint16_t *cnt, i;
+	char *p, path[PATH_MAX + 1];
+	int shmid;
+	int64_t l_mem;
+	bwaidx_t *idx;
+
+	if (hint == 0 || hint[0] == 0) return 0;
+	for (name = hint + strlen(hint) - 1; name >= hint && *name != '/'; --name);
+	++name;
+	if ((shmid = shm_open("/bwactl", O_RDONLY, 0444)) < 0) return 0;
+	shm = mmap(0, BWA_CTL_SIZE, PROT_READ, MAP_SHARED, shmid, 0);
+	cnt = (uint16_t*)shm;
+	if (cnt[0] == 0) return 0;
+	for (i = 0, p = (char*)(shm + 4); i < cnt[0]; ++i) {
+		memcpy(&l_mem, p, 8); p += 8;
+		if (strcmp(p, name) == 0) break;
+		p += strlen(p) + 1;
+	}
+	if (i == cnt[0]) return 0;
+
+	strcat(strcpy(path, "/bwaidx-"), name);
+	if ((shmid = shm_open(path, O_RDONLY, 0444)) < 0) return 0;
+	shm_idx = mmap(0, l_mem, PROT_READ, MAP_SHARED, shmid, 0);
+	idx = calloc(1, sizeof(bwaidx_t));
+	bwa_mem2idx(l_mem, shm_idx, idx);
+	idx->is_shm = 1;
+	return idx;
+}
+
+int bwa_shm_list(void)
+{
+	int shmid;
+	uint16_t *cnt, i;
+	char *p, *shm;
+	if ((shmid = shm_open("/bwactl", O_RDONLY, 0444)) < 0) return -1;
+	shm = mmap(0, BWA_CTL_SIZE, PROT_READ, MAP_SHARED, shmid, 0);
+	cnt = (uint16_t*)shm;
+	for (i = 0, p = shm + 4; i < cnt[0]; ++i) {
+		int64_t l_mem;
+		memcpy(&l_mem, p, 8); p += 8;
+		printf("%s\t%ld\n", p, (long)l_mem);
+		p += strlen(p) + 1;
+	}
+	return 0;
+}
+
+int bwa_shm_destroy(void)
+{
+	int shmid;
+	uint16_t *cnt, i;
+	char *p, *shm;
+	char path[PATH_MAX + 1];
+
+	if ((shmid = shm_open("/bwactl", O_RDONLY, 0444)) < 0) return -1;
+	shm = mmap(0, BWA_CTL_SIZE, PROT_READ, MAP_SHARED, shmid, 0);
+	cnt = (uint16_t*)shm;
+	for (i = 0, p = shm + 4; i < cnt[0]; ++i) {
+		int64_t l_mem;
+		memcpy(&l_mem, p, 8); p += 8;
+		strcat(strcpy(path, "/bwaidx-"), p);
+		shm_unlink(path);
+		p += strlen(p) + 1;
+	}
+	munmap(shm, BWA_CTL_SIZE);
+	shm_unlink("/bwactl");
+	return 0;
+}
+
+int main_shm(int argc, char *argv[])
+{
+	int c, to_list = 0, to_drop = 0, ret = 0;
+	while ((c = getopt(argc, argv, "ld")) >= 0) {
+		if (c == 'l') to_list = 1;
+		else if (c == 'd') to_drop = 1;
+	}
+	if (optind == argc && !to_list && !to_drop) {
+		fprintf(stderr, "\nUsage: bwa shm [-d|-l] [idxbase]\n\n");
+		fprintf(stderr, "Options: -d      destroy all indices in shared memory\n");
+		fprintf(stderr, "         -l      list names of indices in shared memory\n\n");
+		return 1;
+	}
+	if (optind < argc && (to_list || to_drop)) {
+		fprintf(stderr, "[E::%s] open -l or -d cannot be used when 'idxbase' is present\n", __func__);
+		return 1;
+	}
+	if (optind < argc) {
+		bwaidx_t *idx;
+		idx = bwa_idx_load_from_disk(argv[optind], BWA_IDX_ALL);
+		if (bwa_shm_stage(idx, argv[optind]) < 0) {
+			fprintf(stderr, "[E::%s] failed to stage the index in shared memory\n", __func__);
+			ret = 1;
+		}
+		bwa_idx_destroy(idx);
+	}
+	if (to_list) bwa_shm_list();
+	if (to_drop) bwa_shm_destroy();
+	return ret;
+}