platform/ext/common/boot_hal.c

/*
 * Copyright (c) 2019-2020, Arm Limited. All rights reserved.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 *
 */

#include "target_cfg.h"
#include "cmsis.h"
#include "boot_hal.h"
#include "Driver_Flash.h"
#include "flash_layout.h"

/* Flash device name must be specified by target */
extern ARM_DRIVER_FLASH FLASH_DEV_NAME;

/*!
 * \brief Chain-loading the next image in the boot sequence.
 *
 * This function calls the Reset_Handler of the next image in the boot sequence,
 * usually it is the secure firmware. Before passing the execution to next image
 * there is conditional rule to remove the secrets from the memory. This must be
 * done if the following conditions are satisfied:
 *  - Memory is shared between SW components at different stages of the trusted
 *    boot process.
 *  - There are secrets in the memory: KDF parameter, symmetric key,
 *    manufacturer sensitive code/data, etc.
 */
#if defined(__ICCARM__)
#pragma required = boot_clear_bl2_ram_area
#endif

__WEAK __attribute__((naked)) void boot_jump_to_next_image(uint32_t reset_handler_addr)
{
    __ASM volatile(
#if !defined(__ICCARM__)
        ".syntax unified                 \n"
#endif
        "mov     r7, r0                  \n"
        "bl      boot_clear_bl2_ram_area \n" /* Clear RAM before jump */
        "movs    r0, #0                  \n" /* Clear registers: R0-R12, */
        "mov     r1, r0                  \n" /* except R7 */
        "mov     r2, r0                  \n"
        "mov     r3, r0                  \n"
        "mov     r4, r0                  \n"
        "mov     r5, r0                  \n"
        "mov     r6, r0                  \n"
        "mov     r8, r0                  \n"
        "mov     r9, r0                  \n"
        "mov     r10, r0                 \n"
        "mov     r11, r0                 \n"
        "mov     r12, r0                 \n"
        "mov     lr,  r0                 \n"
        "bx      r7                      \n" /* Jump to Reset_handler */
    );
}

/* bootloader platform-specific hw initialization */
__WEAK int32_t boot_platform_init(void)
{
    int32_t result;

    result = FLASH_DEV_NAME.Initialize(NULL);
    if (result == ARM_DRIVER_OK) {
        return 0;
    }

    return 1;
}

__WEAK void boot_platform_quit(struct boot_arm_vector_table *vt)
{
    /* Clang at O0, stores variables on the stack with SP relative addressing.
     * When manually set the SP then the place of reset vector is lost.
     * Static variables are stored in 'data' or 'bss' section, change of SP has
     * no effect on them.
     */
    static struct boot_arm_vector_table *vt_cpy;

    vt_cpy = vt;
#if defined(__ARM_ARCH_8M_MAIN__) || defined(__ARM_ARCH_8M_BASE__)
    /* Restore the Main Stack Pointer Limit register's reset value
     * before passing execution to runtime firmware to make the
     * bootloader transparent to it.
     */
    __set_MSPLIM(0);
#endif
    __set_MSP(vt_cpy->msp);
    __DSB();
    __ISB();

    boot_jump_to_next_image(vt_cpy->reset);
}