揭阳网站制作价格,网站设计评级,网页设计师联盟qq群,深圳的小型网络公司目录 前言流程图autoboot_commandrun_command_listdo_bootmdo_bootm_statesdo_bootm_linuxboot_prep_linuxboot_jump_linux 前言
本文在u-boot启动流程分析这篇文章的基础上#xff0c;简要梳理uboot启动linux kernel的流程。
流程图 其中#xff0c;
autoboot_command位于… 目录 前言流程图autoboot_commandrun_command_listdo_bootmdo_bootm_statesdo_bootm_linuxboot_prep_linuxboot_jump_linux 前言
本文在u-boot启动流程分析这篇文章的基础上简要梳理uboot启动linux kernel的流程。
流程图 其中
autoboot_command位于uboot/common/autoboot.crun_command_list位于uboot/common/cli.cdo_bootm位于uboot/cmd/bootm.cdo_bootm_states位于uboot/common/bootm.cdo_bootm_linux位于uboot/arch/arm/lib/bootm.cboot_prep_linux位于uboot/arch/arm/lib/bootm.cboot_jump_linux位于uboot/arch/arm/lib/bootm.c
autoboot_command
void autoboot_command(const char *s)
{debug(### main_loop: bootcmd\%s\\n, s ? s : UNDEFINED);if (s (stored_bootdelay -2 ||(stored_bootdelay ! -1 !abortboot(stored_bootdelay)))) {bool lock;int prev;lock IS_ENABLED(CONFIG_AUTOBOOT_KEYED) !IS_ENABLED(CONFIG_AUTOBOOT_KEYED_CTRLC);if (lock)prev disable_ctrlc(1); /* disable Ctrl-C checking */run_command_list(s, -1, 0);if (lock)disable_ctrlc(prev); /* restore Ctrl-C checking */}if (IS_ENABLED(CONFIG_USE_AUTOBOOT_MENUKEY) menukey AUTOBOOT_MENUKEY) {s env_get(menucmd);if (s)run_command_list(s, -1, 0);}
}其中abortboot会等待一段时间timeout由环境变量bootdelay设定 如果有按键被按下则会返回1此时将停止启动linux kernel返回命令行。如果在timeout后依然无按键被按下则继续执行启动linux kernel的命令。
run_command_list
run_command_list调用do_bootm的流程实现的关键点 在上面的代码中,将bootm和do_bootm这个函数绑定。
U_BOOT_CMD的定义在uboot/include/command.h中可以自行查看源代码。
do_bootm
int do_bootm(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
{
#ifdef CONFIG_NEEDS_MANUAL_RELOCstatic int relocated 0;if (!relocated) {int i;/* relocate names of sub-command table */for (i 0; i ARRAY_SIZE(cmd_bootm_sub); i)cmd_bootm_sub[i].name gd-reloc_off;relocated 1;}
#endif/* determine if we have a sub command */argc--; argv;if (argc 0) {char *endp;simple_strtoul(argv[0], endp, 16);/* endp pointing to NULL means that argv[0] was just a* valid number, pass it along to the normal bootm processing** If endp is : or # assume a FIT identifier so pass* along for normal processing.** Right now we assume the first arg should never be -*/if ((*endp ! 0) (*endp ! :) (*endp ! #))return do_bootm_subcommand(cmdtp, flag, argc, argv);}return do_bootm_states(cmdtp, flag, argc, argv, BOOTM_STATE_START |BOOTM_STATE_FINDOS | BOOTM_STATE_FINDOTHER |BOOTM_STATE_LOADOS |
#ifdef CONFIG_SYS_BOOT_RAMDISK_HIGHBOOTM_STATE_RAMDISK |
#endif
#if defined(CONFIG_PPC) || defined(CONFIG_MIPS)BOOTM_STATE_OS_CMDLINE |
#endifBOOTM_STATE_OS_PREP | BOOTM_STATE_OS_FAKE_GO |BOOTM_STATE_OS_GO, images, 1);
}这个函数最核心的部分就是调用do_bootm_states。
do_bootm_states
int do_bootm_states(struct cmd_tbl *cmdtp, int flag, int argc,char *const argv[], int states, bootm_headers_t *images,int boot_progress)
{boot_os_fn *boot_fn;ulong iflag 0;int ret 0, need_boot_fn;images-state | states;/** Work through the states and see how far we get. We stop on* any error.*/if (states BOOTM_STATE_START)ret bootm_start(cmdtp, flag, argc, argv);if (!ret (states BOOTM_STATE_FINDOS))ret bootm_find_os(cmdtp, flag, argc, argv);if (!ret (states BOOTM_STATE_FINDOTHER))ret bootm_find_other(cmdtp, flag, argc, argv);/* Load the OS */if (!ret (states BOOTM_STATE_LOADOS)) {iflag bootm_disable_interrupts();ret bootm_load_os(images, 0);if (ret ret ! BOOTM_ERR_OVERLAP)goto err;else if (ret BOOTM_ERR_OVERLAP)ret 0;}/* Relocate the ramdisk */
#ifdef CONFIG_SYS_BOOT_RAMDISK_HIGHif (!ret (states BOOTM_STATE_RAMDISK)) {ulong rd_len images-rd_end - images-rd_start;ret boot_ramdisk_high(images-lmb, images-rd_start,rd_len, images-initrd_start, images-initrd_end);if (!ret) {env_set_hex(initrd_start, images-initrd_start);env_set_hex(initrd_end, images-initrd_end);}}
#endif
#if IMAGE_ENABLE_OF_LIBFDT defined(CONFIG_LMB)if (!ret (states BOOTM_STATE_FDT)) {boot_fdt_add_mem_rsv_regions(images-lmb, images-ft_addr);ret boot_relocate_fdt(images-lmb, images-ft_addr,images-ft_len);}
#endif/* From now on, we need the OS boot function */if (ret)return ret;boot_fn bootm_os_get_boot_func(images-os.os);need_boot_fn states (BOOTM_STATE_OS_CMDLINE |BOOTM_STATE_OS_BD_T | BOOTM_STATE_OS_PREP |BOOTM_STATE_OS_FAKE_GO | BOOTM_STATE_OS_GO);if (boot_fn NULL need_boot_fn) {if (iflag)enable_interrupts();printf(ERROR: booting os %s (%d) is not supported\n,genimg_get_os_name(images-os.os), images-os.os);bootstage_error(BOOTSTAGE_ID_CHECK_BOOT_OS);return 1;}/* Call various other states that are not generally used */if (!ret (states BOOTM_STATE_OS_CMDLINE))ret boot_fn(BOOTM_STATE_OS_CMDLINE, argc, argv, images);if (!ret (states BOOTM_STATE_OS_BD_T))ret boot_fn(BOOTM_STATE_OS_BD_T, argc, argv, images);if (!ret (states BOOTM_STATE_OS_PREP)) {ret bootm_process_cmdline_env(images-os.os IH_OS_LINUX);if (ret) {printf(Cmdline setup failed (err%d)\n, ret);ret CMD_RET_FAILURE;goto err;}ret boot_fn(BOOTM_STATE_OS_PREP, argc, argv, images);}#ifdef CONFIG_TRACE/* Pretend to run the OS, then run a user command */if (!ret (states BOOTM_STATE_OS_FAKE_GO)) {char *cmd_list env_get(fakegocmd);ret boot_selected_os(argc, argv, BOOTM_STATE_OS_FAKE_GO,images, boot_fn);if (!ret cmd_list)ret run_command_list(cmd_list, -1, flag);}
#endif/* Check for unsupported subcommand. */if (ret) {puts(subcommand not supported\n);return ret;}/* Now run the OS! We hope this doesnt return */if (!ret (states BOOTM_STATE_OS_GO))ret boot_selected_os(argc, argv, BOOTM_STATE_OS_GO,images, boot_fn);/* Deal with any fallout */
err:if (iflag)enable_interrupts();if (ret BOOTM_ERR_UNIMPLEMENTED)bootstage_error(BOOTSTAGE_ID_DECOMP_UNIMPL);else if (ret BOOTM_ERR_RESET)do_reset(cmdtp, flag, argc, argv);return ret;
}
该函数的核心部分
bootm_load_os将kernel镜像加载到内存中。调用do_bootm_linux启动kernel。
do_bootm_linux
int do_bootm_linux(int flag, int argc, char *const argv[],bootm_headers_t *images)
{/* No need for those on ARM */if (flag BOOTM_STATE_OS_BD_T || flag BOOTM_STATE_OS_CMDLINE)return -1;if (flag BOOTM_STATE_OS_PREP) {boot_prep_linux(images);return 0;}if (flag (BOOTM_STATE_OS_GO | BOOTM_STATE_OS_FAKE_GO)) {boot_jump_linux(images, flag);return 0;}boot_prep_linux(images);boot_jump_linux(images, flag);return 0;
}boot_prep_linux负责准备传递给kernel的参数。boot_jump_linux负责跳转执行kernel代码。
boot_prep_linux
static void boot_prep_linux(bootm_headers_t *images)
{char *commandline env_get(bootargs);if (IMAGE_ENABLE_OF_LIBFDT images-ft_len) {
#ifdef CONFIG_OF_LIBFDTdebug(using: FDT\n);if (image_setup_linux(images)) {printf(FDT creation failed! hanging...);hang();}
#endif} else if (BOOTM_ENABLE_TAGS) {debug(using: ATAGS\n);setup_start_tag(gd-bd);if (BOOTM_ENABLE_SERIAL_TAG)setup_serial_tag(params);if (BOOTM_ENABLE_CMDLINE_TAG)setup_commandline_tag(gd-bd, commandline);if (BOOTM_ENABLE_REVISION_TAG)setup_revision_tag(params);if (BOOTM_ENABLE_MEMORY_TAGS)setup_memory_tags(gd-bd);if (BOOTM_ENABLE_INITRD_TAG) {/** In boot_ramdisk_high(), it may relocate ramdisk to* a specified location. And set images-initrd_start * images-initrd_end to relocated ramdisks start/end* addresses. So use them instead of images-rd_start * images-rd_end when possible.*/if (images-initrd_start images-initrd_end) {setup_initrd_tag(gd-bd, images-initrd_start,images-initrd_end);} else if (images-rd_start images-rd_end) {setup_initrd_tag(gd-bd, images-rd_start,images-rd_end);}}setup_board_tags(params);setup_end_tag(gd-bd);} else {printf(FDT and ATAGS support not compiled in - hanging\n);hang();}board_prep_linux(images);
}可以看到u-boot使用的是tag的方式传参。共计分为以下几类tag:
setup_serial_tag设定与板子序列号64位相关的参数。setup_commandline_tag设置命令行启动参数参数来自环境变量bootargs。setup_revision_tag 设置修订版本。setup_memory_tags设置内存区块相关参数。setup_initrd_tag设置ramdisk相关的参数。
注以上参数并非都是必要的。
boot_jump_linux
static void boot_jump_linux(bootm_headers_t *images, int flag)
{
#ifdef CONFIG_ARM64void (*kernel_entry)(void *fdt_addr, void *res0, void *res1,void *res2);int fake (flag BOOTM_STATE_OS_FAKE_GO);kernel_entry (void (*)(void *fdt_addr, void *res0, void *res1,void *res2))images-ep;debug(## Transferring control to Linux (at address %lx)...\n,(ulong) kernel_entry);bootstage_mark(BOOTSTAGE_ID_RUN_OS);announce_and_cleanup(fake);if (!fake) {
#ifdef CONFIG_ARMV8_PSCIarmv8_setup_psci();
#endifdo_nonsec_virt_switch();update_os_arch_secondary_cores(images-os.arch);#ifdef CONFIG_ARMV8_SWITCH_TO_EL1armv8_switch_to_el2((u64)images-ft_addr, 0, 0, 0,(u64)switch_to_el1, ES_TO_AARCH64);
#elseif ((IH_ARCH_DEFAULT IH_ARCH_ARM64) (images-os.arch IH_ARCH_ARM))armv8_switch_to_el2(0, (u64)gd-bd-bi_arch_number,(u64)images-ft_addr, 0,(u64)images-ep,ES_TO_AARCH32);elsearmv8_switch_to_el2((u64)images-ft_addr, 0, 0, 0,images-ep,ES_TO_AARCH64);
#endif}
#elseunsigned long machid gd-bd-bi_arch_number;char *s;void (*kernel_entry)(int zero, int arch, uint params);unsigned long r2;int fake (flag BOOTM_STATE_OS_FAKE_GO);kernel_entry (void (*)(int, int, uint))images-ep;
#ifdef CONFIG_CPU_V7Mulong addr (ulong)kernel_entry | 1;kernel_entry (void *)addr;
#endifs env_get(machid);if (s) {if (strict_strtoul(s, 16, machid) 0) {debug(strict_strtoul failed!\n);return;}printf(Using machid 0x%lx from environment\n, machid);}debug(## Transferring control to Linux (at address %08lx) \...\n, (ulong) kernel_entry);bootstage_mark(BOOTSTAGE_ID_RUN_OS);announce_and_cleanup(fake);if (IMAGE_ENABLE_OF_LIBFDT images-ft_len)r2 (unsigned long)images-ft_addr;elser2 gd-bd-bi_boot_params;if (!fake) {
#ifdef CONFIG_ARMV7_NONSECif (armv7_boot_nonsec()) {armv7_init_nonsec();secure_ram_addr(_do_nonsec_entry)(kernel_entry,0, machid, r2);} else
#endifkernel_entry(0, machid, r2);}
#endif
}r2 gd-bd-bi_boot_params; 是将TAG列表所在的内存地址赋值给通用寄存器R2。 kernel_entry(0, machid, r2); 跳转执行kernel的代码自此uboot的使命完成生命周期结束。
综上Uboot传递给linux kernel的参数是通过R2传递的。当linux kernel启动后会从R2中拿到TAG列表的地址然后将TAG参数解析出来使用。
