cmdline -[command line,__fdt_pointer,initial_boot_params] boot_command_line 获取
[boot_command_line,cmdline,commandline,devicetree地址]
head.S->start_kernel(), head.S 中主要是获取dt的地址：
str_l x21, __fdt_pointer, x5 // Save FDT pointer
>>start_kernel() -- main.c
>>setup_arch() --setup.c
>>setup_machine_fdt()
>>early_init_dt_scan() --fdt.c
>>early_init_dt_verify() --fdt.c ;check __fdt_pointer后，赋给initial_boot_params
>>early_init_dt_scan_nodes() --fdt.c ;最终获取devicetree参数
>>early_init_dt_scan_chosen --fdt.c; 获取command line 参数
setup_arch(&command_line);
command_line 是对 全局变量boot_command_line的一个引用
setup_machine_fdt()
__fdt_pointer 经过fixmap_remap_fdt(dt_phys) 映射后，往下传参
early_init_dt_scan_nodes
获取 command_line参数,给boot_command_line 赋值
获取memory参数
int __init early_init_dt_scan_chosen(unsigned long node, const char *uname,
int depth, void *data)
{
int l;
const char *p;pr_debug("search \"chosen\", depth: %d, uname: %s\n", depth, uname);
if (depth != 1 || !data ||
(strcmp(uname, "chosen") != 0 && strcmp(uname, "chosen@0") != 0))
return 0;early_init_dt_check_for_initrd(node);
/* Retrieve command line */
p = of_get_flat_dt_prop(node, "bootargs", &l);
if (p != NULL && l > 0)
strlcpy(data, p, min((int)l, COMMAND_LINE_SIZE)); //拷贝到 boot_command_line/*
* CONFIG_CMDLINE is meant to be a default in case nothing else
* managed to set the command line, unless CONFIG_CMDLINE_FORCE
* is set in which case we override whatever was found earlier.
*/
#ifdef CONFIG_CMDLINE
#if defined(CONFIG_CMDLINE_EXTEND)
strlcat(data, " ", COMMAND_LINE_SIZE);
strlcat(data, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
#elif defined(CONFIG_CMDLINE_FORCE)
strlcpy(data, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
#else
/* No arguments from boot loader, use kernel's cmdl*/
if (!((char *)data)[0])
strlcpy(data, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
#endif
#endif /* CONFIG_CMDLINE */pr_debug("Command line is: %s\n", (char*)data);
/* break now */
return 1;
}
void __init early_init_dt_scan_nodes(void)
{
/* Retrieve various information from the /chosen node */
of_scan_flat_dt(early_init_dt_scan_chosen, boot_command_line);/* Initialize {size,address}-cells info */
of_scan_flat_dt(early_init_dt_scan_root, NULL);/* Setup memory, calling early_init_dt_add_memory_arch */
of_scan_flat_dt(early_init_dt_scan_memory, NULL);
}
bootloader 参数传递
我们常用的方式是在bootload中通过bootargs直接传递(arm64) ,只需要在BootLinux函数中修改即可，往BootParamlistPtr.CmdLine变量后面粘贴一个字符串(ql_crash_mode=0,0)。在UpdateCmdLine函数中会对一系列（很多很多）的cmdline进行预处理
EFI_STATUS BootLinux (BootInfo *Info)
{xxxxxxxxxx
#ifdef QL_DEBUG_MODE
if ( Info->BootWithDebug == TRUE){
AsciiStrCatS (BootParamlistPtr.CmdLine, BOOT_ARGS_SIZE, " debug=1");
}
#endif#ifdef QL_DUMP_MODE
if ( Info->BootWithDump == TRUE){
AsciiStrCatS (BootParamlistPtr.CmdLine, BOOT_ARGS_SIZE, " ql_crash_mode=0,0");
}
#endif
Status = UpdateCmdLine (BootParamlistPtr.CmdLine, FfbmStr, Recovery,
AlarmBoot, Info->VBCmdLine, &BootParamlistPtr.FinalCmdLine,
&BootParamlistPtr.FinalBootConfig,
&BootParamlistPtr.FinalBootConfigLen,
Info->HeaderVersion,
(VOID *)BootParamlistPtr.DeviceTreeLoadAddr);xxxxxxxxxx
Status = LoadAddrAndDTUpdate (Info, &BootParamlistPtr);
if (Status != EFI_SUCCESS) {
return Status;
}
xxxxxxxxxx
}
UpdateCmdLine处理完成后，由LoadAddrAndDTUpdate携带BootParamlistPtr参数经过后续一系列调用后，最终会在UpdateDeviceTree 函数中将cmdline中记录的所有数据全部添加到bootargs的设备节点中
EFI_STATUS UpdateDeviceTree (VOID *fdt,CONST CHAR8 *cmdline,VOID *ramdisk,UINT32 RamDiskSize,BOOLEAN BootWith32Bit)
{
xxxxxxxxxxxx
if (cmdline) {
/* Adding the cmdline to the chosen node */
FdtPropUpdateFunc (fdt, offset, (CONST char *)"bootargs",
(CONST VOID *)cmdline, fdt_appendprop_string, ret);
if (ret) {
DEBUG ((EFI_D_ERROR,
"ERROR: Cannot update chosen node [bootargs] - 0x%x\n", ret));
return EFI_LOAD_ERROR;
}
}
xxxxxxxxxxxx
}
FdtPropUpdateFunc ：将参数添加到fdt bootargs中
参数接收处理
bootload传输过来cmdline之后，我们只需要在适当的位置添加内核参数的处理函数。假如bootloader在启动kernel时传递的参数是"ql_crash_mode=xxx"，kernel运行的时候就会自动调用set_crash_mode函数，通过s参数将cmdline携带的参数带入函数。
static int __init set_crash_mode(char *s)
{
xxxxxxxxxx
}
__setup("ql_crash_mode=", set_crash_mode);
注：参照 内核参数cmdline后续处理源码分析-1