uboot 如何启动内核解析 + uboot 添加命令

robe.zhang · 发表于 2019-6-9 13:42:46

本帖最后由 robe.zhang 于 2019-6-9 14:38 编辑

本文基于米尔 mys_y6ull 开发板 uboot 源码 2016.03 版本：

uboot 启动 kernel 的指令是：bootz 0x83000000 - 0x84000000
bootz 是 uboot 的一个命令，可以在源码 uboot/cmd/bootm.c 中找到，如下：
U_BOOT_CMD(
bootz, CONFIG_SYS_MAXARGS, 1, do_bootz,
"boot Linux zImage image from memory", bootz_help_text
);
0x83000000 是 kernel 地址
- 是 initrd image 地址
0x84000000 是 fdt 地址

U_BOOT_CMD 是个宏，经过一系列分析：

#define U_BOOT_CMD_MKENT_COMPLETE(_name, _maxargs, _rep, _cmd, \
_usage, _help, _comp) \
{ #_name, _maxargs, _rep, _cmd, _usage, \
_CMD_HELP(_help) _CMD_COMPLETE(_comp) }
#define U_BOOT_CMD_MKENT(_name, _maxargs, _rep, _cmd, _usage, _help) \
U_BOOT_CMD_MKENT_COMPLETE(_name, _maxargs, _rep, _cmd, \
_usage, _help, NULL)
#define U_BOOT_CMD_COMPLETE(_name, _maxargs, _rep, _cmd, _usage, _help, _comp) \
ll_entry_declare(cmd_tbl_t, _name, cmd) = \
U_BOOT_CMD_MKENT_COMPLETE(_name, _maxargs, _rep, _cmd, \
_usage, _help, _comp);
#define U_BOOT_CMD(_name, _maxargs, _rep, _cmd, _usage, _help) \
U_BOOT_CMD_COMPLETE(_name, _maxargs, _rep, _cmd, _usage, _help, NULL)
#define ll_entry_declare(_type, _name, _list) \
_type _u_boot_list_2_##_list##_2_##_name __aligned(4) \
__attribute__((unused, \
section(".u_boot_list_2_"#_list"_2_"#_name)))
# define _CMD_HELP(x) x,
# define _CMD_COMPLETE(x) x,
struct cmd_tbl_s {
char *name; /* Command Name */
int maxargs; /* maximum number of arguments */
int repeatable; /* autorepeat allowed? */
/* Implementation function */
int (*cmd)(struct cmd_tbl_s *, int, int, char * const []);
char *usage; /* Usage message (short) */
#ifdef CONFIG_SYS_LONGHELP
char *help; /* Help message (long) */
#endif
#ifdef CONFIG_AUTO_COMPLETE
/* do auto completion on the arguments */
int (*complete)(int argc, char * const argv[], char last_char, int maxv, char *cmdv[]);
#endif
};
typedef struct cmd_tbl_s cmd_tbl_t;
U_BOOT_CMD(_name, _maxargs, _rep, _cmd, _usage, _help)
= U_BOOT_CMD_COMPLETE(_name, _maxargs, _rep, _cmd, _usage, _help, NULL)
= ll_entry_declare(cmd_tbl_t, _name, cmd) = U_BOOT_CMD_MKENT_COMPLETE(_name, _maxargs, _rep, _cmd, _usage, _help, _comp);
= _type _u_boot_list_2_##_list##_2_##_name __aligned(4) __attribute__((unused, section(".u_boot_list_2_"#_list"_2_"#_name)))
= U_BOOT_CMD_MKENT_COMPLETE(_name, _maxargs, _rep, _cmd, _usage, _help, _comp);
= _u_boot_list_2_##_list##_2_##_name = { #_name, _maxargs, _rep, _cmd, _usage, _CMD_HELP(_help) _CMD_COMPLETE(_comp) }
= _u_boot_list_2_##_list##_2_##_name = { #_name, _maxargs, _rep, _cmd, _usage, _help, _comp, }
U_BOOT_CMD(_name, _maxargs, _rep, _cmd, _usage, _help) // U_BOOT_CMD 宏定义，是 U_BOOT_CMD_COMPLETE 的一个特例
= _u_boot_list_2_##_list##_2_##_name = { #_name, _maxargs, _rep, _cmd, _usage, _help, _comp, }
U_BOOT_CMD_COMPLETE // U_BOOT_CMD_COMPLETE 多一个参数

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其实还需要从 uboot main_loop 中分析，更清楚看到 U_BOOT_CMD 定义的宏是如何被调用使用的。
得出的结论是：bootz 命令实际执行的是 do_bootz 函数，继续追踪：

// ================================== bootz 解析
bootz 0x83000000 - 0x84000000
int do_bootz(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
{
int ret;
/* Consume 'bootz' */
argc--; argv++; 调整 argc | argv 参数，去掉 bootz
if (bootz_start(cmdtp, flag, argc, argv, &images)) 清空 image ，设置 verify，states，设置 image->ep 入口地址
获取 ramdisk，fdt，设置 image.rd_addr / rd_len / image.ft_addr / ft_len
return 1;
/*
* We are doing the BOOTM_STATE_LOADOS state ourselves, so must
* disable interrupts ourselves
*/
bootm_disable_interrupts(); 关中断，关网口，关usb
images.os.os = IH_OS_LINUX;
ret = do_bootm_states(cmdtp, flag, argc, argv, 设置 boot_fn = do_bootm_linux
BOOTM_STATE_OS_PREP | BOOTM_STATE_OS_FAKE_GO | 设置 tag，开始tag，串口，commandline(bootargs)，revision(cpuver), memory, initrd, board(空), end tag ---- (BOOTM_STATE_OS_PREP)
BOOTM_STATE_OS_GO, 获取 machid(env), 获取 ft_addr/tag 地址，进入kernel_entry(0, machid, r2); ---- (BOOTM_STATE_OS_FAKE_GO | BOOTM_STATE_OS_GO)
&images, 1);
return ret;
}

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详细内容看注释，最终调用 boot_jump_linux 函数，boot_jump_linux 又调用 kernel_entry(0, machid, r2); ，进入 kernel 程序的入口，之后就开始运行 kernel 代码了

static void boot_jump_linux(bootm_headers_t *images, int flag)
{
#ifdef CONFIG_ARM64
void (*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) {
do_nonsec_virt_switch();
kernel_entry(images->ft_addr, NULL, NULL, NULL);
}
#else
unsigned 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;
s = getenv("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;
else
r2 = gd->bd->bi_boot_params;
if (!fake) {
#ifdef CONFIG_ARMV7_NONSEC
if (armv7_boot_nonsec()) {
armv7_init_nonsec();
secure_ram_addr(_do_nonsec_entry)(kernel_entry,
0, machid, r2);
} else
#endif
kernel_entry(0, machid, r2);
}
#endif
}

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代码中用到的两个结构体，要给是 image ，一个是 tag，如下：

// ================================
typedef struct bootm_headers {
/*
* Legacy os image header, if it is a multi component image
* then boot_get_ramdisk() and get_fdt() will attempt to get
* data from second and third component accordingly.
*/
image_header_t *legacy_hdr_os; /* image header pointer */
image_header_t legacy_hdr_os_copy; /* header copy */
ulong legacy_hdr_valid;
#if defined(CONFIG_FIT)
const char *fit_uname_cfg; /* configuration node unit name */
void *fit_hdr_os; /* os FIT image header */
const char *fit_uname_os; /* os subimage node unit name */
int fit_noffset_os; /* os subimage node offset */
void *fit_hdr_rd; /* init ramdisk FIT image header */
const char *fit_uname_rd; /* init ramdisk subimage node unit name */
int fit_noffset_rd; /* init ramdisk subimage node offset */
void *fit_hdr_fdt; /* FDT blob FIT image header */
const char *fit_uname_fdt; /* FDT blob subimage node unit name */
int fit_noffset_fdt;/* FDT blob subimage node offset */
void *fit_hdr_setup; /* x86 setup FIT image header */
const char *fit_uname_setup; /* x86 setup subimage node name */
int fit_noffset_setup;/* x86 setup subimage node offset */
#endif
#ifndef USE_HOSTCC
image_info_t os; /* os image info */
ulong ep; /* entry point of OS */
ulong rd_start, rd_end;/* ramdisk start/end */
char *ft_addr; /* flat dev tree address */
ulong ft_len; /* length of flat device tree */
ulong initrd_start;
ulong initrd_end;
ulong cmdline_start;
ulong cmdline_end;
bd_t *kbd;
#endif
int verify; /* getenv("verify")[0] != 'n' */
#define BOOTM_STATE_START (0x00000001)
#define BOOTM_STATE_FINDOS (0x00000002)
#define BOOTM_STATE_FINDOTHER (0x00000004)
#define BOOTM_STATE_LOADOS (0x00000008)
#define BOOTM_STATE_RAMDISK (0x00000010)
#define BOOTM_STATE_FDT (0x00000020)
#define BOOTM_STATE_OS_CMDLINE (0x00000040)
#define BOOTM_STATE_OS_BD_T (0x00000080)
#define BOOTM_STATE_OS_PREP (0x00000100)
#define BOOTM_STATE_OS_FAKE_GO (0x00000200) /* 'Almost' run the OS */
#define BOOTM_STATE_OS_GO (0x00000400)
int state;
#ifdef CONFIG_LMB
struct lmb lmb; /* for memory mgmt */
#endif
} bootm_headers_t;
// -----------------------------------
typedef struct image_header {
__be32 ih_magic; /* Image Header Magic Number */
__be32 ih_hcrc; /* Image Header CRC Checksum */
__be32 ih_time; /* Image Creation Timestamp */
__be32 ih_size; /* Image Data Size */
__be32 ih_load; /* Data Load Address */
__be32 ih_ep; /* Entry Point Address */
__be32 ih_dcrc; /* Image Data CRC Checksum */
uint8_t ih_os; /* Operating System */
uint8_t ih_arch; /* CPU architecture */
uint8_t ih_type; /* Image Type */
uint8_t ih_comp; /* Compression Type */
uint8_t ih_name[IH_NMLEN]; /* Image Name */
} image_header_t;
// -----------------------------------
typedef struct image_info {
ulong start, end; /* start/end of blob */
ulong image_start, image_len; /* start of image within blob, len of image */
ulong load; /* load addr for the image */
uint8_t comp, type, os; /* compression, type of image, os type */
uint8_t arch; /* CPU architecture */
} image_info_t;
// -----------------------------------
struct lmb {
struct lmb_region memory;
struct lmb_region reserved;
};
// -----------------------------------
struct lmb_region {
unsigned long cnt;
phys_size_t size;
struct lmb_property region[MAX_LMB_REGIONS+1];
};
// -----------------------------------
struct lmb_property {
phys_addr_t base;
phys_size_t size;
};
// -----------------------------------
struct tag {
struct tag_header hdr;
union {
struct tag_core core;
struct tag_mem32 mem;
struct tag_videotext videotext;
struct tag_ramdisk ramdisk;
struct tag_initrd initrd;
struct tag_serialnr serialnr;
struct tag_revision revision;
struct tag_videolfb videolfb;
struct tag_cmdline cmdline;
/*
* Acorn specific
*/
struct tag_acorn acorn;
/*
* DC21285 specific
*/
struct tag_memclk memclk;
} u;
};
struct tag_header {
u32 size;
u32 tag;
};
struct tag_core {
u32 flags; /* bit 0 = read-only */
u32 pagesize;
u32 rootdev;
};
struct tag_mem32 {
u32 size;
u32 start; /* physical start address */
};
struct tag_videotext {
u8 x;
u8 y;
u16 video_page;
u8 video_mode;
u8 video_cols;
u16 video_ega_bx;
u8 video_lines;
u8 video_isvga;
u16 video_points;
};
struct tag_ramdisk {
u32 flags; /* bit 0 = load, bit 1 = prompt */
u32 size; /* decompressed ramdisk size in _kilo_ bytes */
u32 start; /* starting block of floppy-based RAM disk image */
};
struct tag_initrd {
u32 start; /* physical start address */
u32 size; /* size of compressed ramdisk image in bytes */
};
struct tag_serialnr {
u32 low;
u32 high;
};
struct tag_revision {
u32 rev;
};
struct tag_videolfb {
u16 lfb_width;
u16 lfb_height;
u16 lfb_depth;
u16 lfb_linelength;
u32 lfb_base;
u32 lfb_size;
u8 red_size;
u8 red_pos;
u8 green_size;
u8 green_pos;
u8 blue_size;
u8 blue_pos;
u8 rsvd_size;
u8 rsvd_pos;
};
struct tag_cmdline {
char cmdline[1]; /* this is the minimum size */
};
struct tag_acorn {
u32 memc_control_reg;
u32 vram_pages;
u8 sounddefault;
u8 adfsdrives;
};
struct tag_memclk {
u32 fmemclk;
};

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<完>

看有的嵌入式培训教程中，往 uboot 添加自己的命令，也会当作培训的内容

其实从本帖来看，可以更深层次的知道如何往 uboot 添加自己的命令。
1，添加一个 name.c 文件， name 自己选             // 添加命令的源码文件

2，修改 makefile ，把 name.c 添加作为目标          // 添加到 uboot 程序中

3，打开 name.c 文件，使用 U_BOOT_CMD 定义一个自己的命令。    // 第一个参数就是 uboot 中使用的命令名字，第四个参数是函数名，函数也要自己实现
uboot 中添加自己的命令就完成了。编译后进 uboot 看看有么有自己的命令，会不会执行。

=============  demo

1，添加 robe.c 文件

2，修改 makefile 文件，添加 robe.o 目标

3，编码实现 robe 命令

4，编译 uboot，烧录：

5，启动 uboot 查看有没有 robe 命令

6，运行 robe 命令看看会不会执行

本贴从更深层次分析 uboot 命令的实现，知道如何实现的之后，不用什么教程跟着感觉添加 CMD 命令就可以。

<完>

[原创] uboot 如何启动内核解析 + uboot 添加命令

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