diff --git a/sim/csupport/run.c b/sim/csupport/run.c
new file mode 100644
index 0000000..677f40c
--- /dev/null
+++ b/sim/csupport/run.c
@@ -0,0 +1,195 @@
+/* Run the boot image. */
+
+#include <setjmp.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <bootutil/bootutil.h>
+#include <bootutil/image.h>
+#include "flash_map/flash_map.h"
+
+#include "../../boot/bootutil/src/bootutil_priv.h"
+
+extern int sim_flash_erase(void *flash, uint32_t offset, uint32_t size);
+extern int sim_flash_read(void *flash, uint32_t offset, uint8_t *dest, uint32_t size);
+extern int sim_flash_write(void *flash, uint32_t offset, const uint8_t *src, uint32_t size);
+
+static void *flash_device;
+static jmp_buf boot_jmpbuf;
+int flash_counter;
+
+int jumped = 0;
+
+struct area {
+	struct flash_area whole;
+	struct flash_area *areas;
+	uint32_t num_areas;
+	uint8_t id;
+};
+
+struct area_desc {
+	struct area slots[16];
+	uint32_t num_slots;
+};
+
+static struct area_desc *flash_areas;
+
+int invoke_boot_go(void *flash, struct area_desc *adesc)
+{
+	int res;
+	struct boot_rsp rsp;
+
+	flash_device = flash;
+	flash_areas = adesc;
+	if (setjmp(boot_jmpbuf) == 0) {
+		res = boot_go(&rsp);
+		printf("boot_go result: %d (0x%08x)\n", res, rsp.br_image_addr);
+		return res;
+	} else {
+		return -0x13579;
+	}
+}
+
+int hal_flash_read(uint8_t flash_id, uint32_t address, void *dst,
+		   uint32_t num_bytes)
+{
+	// printf("hal_flash_read: %d, 0x%08x (0x%x)\n",
+	//        flash_id, address, num_bytes);
+	return sim_flash_read(flash_device, address, dst, num_bytes);
+}
+
+int hal_flash_write(uint8_t flash_id, uint32_t address,
+		    const void *src, int32_t num_bytes)
+{
+	// printf("hal_flash_write: 0x%08x (0x%x)\n", address, num_bytes);
+	// fflush(stdout);
+	if (--flash_counter == 0) {
+		jumped++;
+		longjmp(boot_jmpbuf, 1);
+	}
+	return sim_flash_write(flash_device, address, src, num_bytes);
+}
+
+int hal_flash_erase(uint8_t flash_id, uint32_t address,
+		    uint32_t num_bytes)
+{
+	// printf("hal_flash_erase: 0x%08x, (0x%x)\n", address, num_bytes);
+	// fflush(stdout);
+	if (--flash_counter == 0) {
+		jumped++;
+		longjmp(boot_jmpbuf, 1);
+	}
+	return sim_flash_erase(flash_device, address, num_bytes);
+}
+
+uint8_t hal_flash_align(uint8_t flash_id)
+{
+	return 1;
+}
+
+void *os_malloc(size_t size)
+{
+	// printf("os_malloc 0x%x bytes\n", size);
+	return malloc(size);
+}
+
+int flash_area_id_from_image_slot(int slot)
+{
+	return slot + 1;
+}
+
+int flash_area_open(uint8_t id, const struct flash_area **area)
+{
+	int i;
+	struct area *slot;
+
+	for (i = 0; i < flash_areas->num_slots; i++) {
+		if (flash_areas->slots[i].id == id)
+			break;
+	}
+	if (i == flash_areas->num_slots) {
+		printf("Unsupported area\n");
+		abort();
+	}
+
+	/* Unsure if this is right, just returning the first area. */
+	*area = &flash_areas->slots[i].whole;
+	return 0;
+}
+
+void flash_area_close(const struct flash_area *area)
+{
+}
+
+/*
+ * Read/write/erase. Offset is relative from beginning of flash area.
+ */
+int flash_area_read(const struct flash_area *area, uint32_t off, void *dst,
+		    uint32_t len)
+{
+	return hal_flash_read(area->fa_id,
+			      area->fa_off + off,
+			      dst, len);
+}
+
+int flash_area_write(const struct flash_area *area, uint32_t off, const void *src,
+		     uint32_t len)
+{
+	return hal_flash_write(area->fa_id,
+			       area->fa_off + off,
+			       src, len);
+}
+
+int flash_area_erase(const struct flash_area *area, uint32_t off, uint32_t len)
+{
+	return hal_flash_erase(area->fa_id,
+			       area->fa_off + off,
+			       len);
+}
+
+int flash_area_to_sectors(int idx, int *cnt, struct flash_area *ret)
+{
+	int i;
+	struct area *slot;
+
+	for (i = 0; i < flash_areas->num_slots; i++) {
+		if (flash_areas->slots[i].id == idx)
+			break;
+	}
+	if (i == flash_areas->num_slots) {
+		printf("Unsupported area\n");
+		abort();
+	}
+
+	slot = &flash_areas->slots[i];
+
+	if (slot->num_areas > *cnt) {
+		printf("Too many areas in slot\n");
+		abort();
+	}
+
+	*cnt = slot->num_areas;
+	memcpy(ret, slot->areas, slot->num_areas * sizeof(struct flash_area));
+
+	return 0;
+}
+
+uint8_t sim_flash_align = 1;
+uint8_t flash_area_align(const struct flash_area *area)
+{
+	return sim_flash_align;
+}
+
+
+int bootutil_img_validate(struct image_header *hdr,
+                          const struct flash_area *fap,
+                          uint8_t *tmp_buf, uint32_t tmp_buf_sz,
+                          uint8_t *seed, int seed_len, uint8_t *out_hash)
+{
+	if (hal_flash_read(fap->fa_id, fap->fa_off, tmp_buf, 4)) {
+		printf("Flash read error\n");
+		abort();
+	}
+
+	return (*((uint32_t *) tmp_buf) != 0x96f3b83c);
+}