diff --git a/boot/zephyr/firmware_loader.c b/boot/zephyr/firmware_loader.c
new file mode 100644
index 0000000..38b121c
--- /dev/null
+++ b/boot/zephyr/firmware_loader.c
@@ -0,0 +1,194 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Copyright (c) 2020 Arm Limited
+ * Copyright (c) 2020-2023 Nordic Semiconductor ASA
+ */
+
+#include <assert.h>
+#include <zephyr/kernel.h>
+#include <zephyr/devicetree.h>
+#include <zephyr/drivers/gpio.h>
+#include "bootutil/image.h"
+#include "bootutil_priv.h"
+#include "bootutil/bootutil_log.h"
+#include "bootutil/bootutil_public.h"
+#include "bootutil/fault_injection_hardening.h"
+
+#include "io/io.h"
+#include "mcuboot_config/mcuboot_config.h"
+
+BOOT_LOG_MODULE_DECLARE(mcuboot);
+
+/* Variables passed outside of unit via poiters. */
+static const struct flash_area *_fa_p;
+static struct image_header _hdr = { 0 };
+
+#if defined(MCUBOOT_VALIDATE_PRIMARY_SLOT) || defined(MCUBOOT_VALIDATE_PRIMARY_SLOT_ONCE)
+/**
+ * Validate hash of a primary boot image.
+ *
+ * @param[in]	fa_p	flash area pointer
+ * @param[in]	hdr	boot image header pointer
+ *
+ * @return		FIH_SUCCESS on success, error code otherwise
+ */
+fih_ret
+boot_image_validate(const struct flash_area *fa_p,
+                    struct image_header *hdr)
+{
+    static uint8_t tmpbuf[BOOT_TMPBUF_SZ];
+    FIH_DECLARE(fih_rc, FIH_FAILURE);
+
+    /* NOTE: The first argument to boot_image_validate, for enc_state pointer,
+     * is allowed to be NULL only because the single image loader compiles
+     * with BOOT_IMAGE_NUMBER == 1, which excludes the code that uses
+     * the pointer from compilation.
+     */
+    /* Validate hash */
+    if (IS_ENCRYPTED(hdr))
+    {
+        /* Clear the encrypted flag we didn't supply a key
+         * This flag could be set if there was a decryption in place
+         * was performed. We will try to validate the image, and if still
+         * encrypted the validation will fail, and go in panic mode
+         */
+        hdr->ih_flags &= ~(ENCRYPTIONFLAGS);
+    }
+    FIH_CALL(bootutil_img_validate, fih_rc, NULL, 0, hdr, fa_p, tmpbuf,
+             BOOT_TMPBUF_SZ, NULL, 0, NULL);
+
+    FIH_RET(fih_rc);
+}
+#endif /* MCUBOOT_VALIDATE_PRIMARY_SLOT || MCUBOOT_VALIDATE_PRIMARY_SLOT_ONCE*/
+
+inline static fih_ret
+boot_image_validate_once(const struct flash_area *fa_p,
+                    struct image_header *hdr)
+{
+    static struct boot_swap_state state;
+    int rc;
+    FIH_DECLARE(fih_rc, FIH_FAILURE);
+
+    memset(&state, 0, sizeof(struct boot_swap_state));
+    rc = boot_read_swap_state(fa_p, &state);
+    if (rc != 0)
+        FIH_RET(FIH_FAILURE);
+    if (state.magic != BOOT_MAGIC_GOOD
+            || state.image_ok != BOOT_FLAG_SET) {
+        /* At least validate the image once */
+        FIH_CALL(boot_image_validate, fih_rc, fa_p, hdr);
+        if (FIH_NOT_EQ(fih_rc, FIH_SUCCESS)) {
+            FIH_RET(FIH_FAILURE);
+        }
+        if (state.magic != BOOT_MAGIC_GOOD) {
+            rc = boot_write_magic(fa_p);
+            if (rc != 0)
+                FIH_RET(FIH_FAILURE);
+        }
+        rc = boot_write_image_ok(fa_p);
+        if (rc != 0)
+            FIH_RET(FIH_FAILURE);
+    }
+    FIH_RET(FIH_SUCCESS);
+}
+
+/**
+ * Validates that an image in a slot is OK to boot.
+ *
+ * @param[in]	slot	Slot number to check
+ * @param[out]	rsp	Parameters for booting image, on success
+ *
+ * @return		FIH_SUCCESS on success; non-zero on failure.
+ */
+static fih_ret validate_image_slot(int slot, struct boot_rsp *rsp)
+{
+    int rc = -1;
+    FIH_DECLARE(fih_rc, FIH_FAILURE);
+
+    rc = flash_area_open(slot, &_fa_p);
+    assert(rc == 0);
+
+    rc = boot_image_load_header(_fa_p, &_hdr);
+    if (rc != 0) {
+        goto other;
+    }
+
+#ifdef MCUBOOT_VALIDATE_PRIMARY_SLOT
+    FIH_CALL(boot_image_validate, fih_rc, _fa_p, &_hdr);
+    if (FIH_NOT_EQ(fih_rc, FIH_SUCCESS)) {
+        goto other;
+    }
+#elif defined(MCUBOOT_VALIDATE_PRIMARY_SLOT_ONCE)
+    FIH_CALL(boot_image_validate_once, fih_rc, _fa_p, &_hdr);
+    if (FIH_NOT_EQ(fih_rc, FIH_SUCCESS)) {
+        goto other;
+    }
+#else
+    fih_rc = FIH_SUCCESS;
+#endif /* MCUBOOT_VALIDATE_PRIMARY_SLOT */
+
+    rsp->br_flash_dev_id = flash_area_get_device_id(_fa_p);
+    rsp->br_image_off = flash_area_get_off(_fa_p);
+    rsp->br_hdr = &_hdr;
+
+other:
+    flash_area_close(_fa_p);
+
+    FIH_RET(fih_rc);
+}
+
+/**
+ * Gather information on image and prepare for booting. Will boot from main
+ * image if none of the enabled entrance modes for the firmware loader are set,
+ * otherwise will boot the firmware loader. Note: firmware loader must be a
+ * valid signed image with the same signing key as the application image.
+ *
+ * @param[out]	rsp	Parameters for booting image, on success
+ *
+ * @return		FIH_SUCCESS on success; non-zero on failure.
+ */
+fih_ret
+boot_go(struct boot_rsp *rsp)
+{
+    bool boot_firmware_loader = false;
+    FIH_DECLARE(fih_rc, FIH_FAILURE);
+
+#ifdef CONFIG_BOOT_FIRMWARE_LOADER_ENTRANCE_GPIO
+    if (io_detect_pin() &&
+            !io_boot_skip_serial_recovery()) {
+        boot_firmware_loader = true;
+    }
+#endif
+
+#ifdef CONFIG_BOOT_FIRMWARE_LOADER_PIN_RESET
+    if (io_detect_pin_reset()) {
+        boot_firmware_loader = true;
+    }
+#endif
+
+#ifdef CONFIG_BOOT_FIRMWARE_LOADER_BOOT_MODE
+    if (io_detect_boot_mode()) {
+        boot_firmware_loader = true;
+    }
+#endif
+
+    /* Check if firmware loader button is pressed. TODO: check all entrance methods */
+    if (boot_firmware_loader == true) {
+        FIH_CALL(validate_image_slot, fih_rc, FLASH_AREA_IMAGE_SECONDARY(0), rsp);
+
+        if (FIH_EQ(fih_rc, FIH_SUCCESS)) {
+            FIH_RET(fih_rc);
+        }
+    }
+
+    FIH_CALL(validate_image_slot, fih_rc, FLASH_AREA_IMAGE_PRIMARY(0), rsp);
+
+#ifdef CONFIG_BOOT_FIRMWARE_LOADER_NO_APPLICATION
+    if (FIH_NOT_EQ(fih_rc, FIH_SUCCESS)) {
+        FIH_CALL(validate_image_slot, fih_rc, FLASH_AREA_IMAGE_SECONDARY(0), rsp);
+    }
+#endif
+
+    FIH_RET(fih_rc);
+}