通过dmesg分析linux启动过程

通过dmesg分析linux的启动过程，几种放入dmesg文件的方法
第三种形式：log_info("starting version " VERSION);
[ 2.755560] systemd-udevd[96]: starting version 204
cheng@chpc:~/download/systemd-218$ grep -r "starting version" ./*
./src/udev/udevd.c: log_info("starting version " VERSION);
/usr/src/linux-3.18.4/include/linux/syslog.h中有do_syslog()函数的声明
int do_syslog(int type, char __user *buf, int count, bool from_file);
/usr/src/linux-3.18.4/kernel/printk/printk.c文件中有do_syslog()函数的定义
[ 1.496584] Trying to unpack rootfs image as initramfs...
initrd.img.version里面init脚本会调用
usr/share/initramfs-tools/scripts/init-top/udev脚本
udev脚本有对systemd-udevd的调用
/lib/systemd/systemd-udevd --daemon --resolve-names=never
[ 2.755560] systemd-udevd[96]: starting version 204
第一种形式： pr_notice("%s", linux_banner);
init/main.c 中有
pr_notice("%s", linux_banner);
setup_arch(&command_line);
mm_init_cpumask(&init_mm);
setup_command_line(command_line);
setup_nr_cpu_ids();
setup_per_cpu_areas();
smp_prepare_boot_cpu(); /* arch-specific boot-cpu hooks */
build_all_zonelists(NULL, NULL);
page_alloc_init();
pr_notice("Kernel command line: %s\n", boot_command_line);
version.c 中有linux_banner[]定义
const char linux_banner[] =
"Linux version " UTS_RELEASE " (" LINUX_COMPILE_BY "@"
LINUX_COMPILE_HOST ") (" LINUX_COMPILER ") " UTS_VERSION "\n";
dmesg中的信息显示：
[ 0.000000] Linux version 3.18.4 (root@chpc) (gcc version 4.8.2 (Ubuntu 4.8.2-19ubuntu1) ) #1 SMP Wed Feb 4 08:53:13 CST 2015
...
...
[ 0.000000] Kernel command line: BOOT_IMAGE=/boot/vmlinuz-3.18.4 root=UUID=588558ea-103e-4a08-9e09-1b23f25c9ee7 ro quiet splash vt.handoff=7
[ 0.000000] PID hash table entries: 4096 (order: 2, 16384 bytes)
第二种形式：printk(KERN_INFO "virtual kernel memory layout:\n"
cheng@chpc:/usr/src/linux-3.18.4$ grep -rn "virtual kernel memory layout" ./*
./arch/xtensa/mm/init.c:330: pr_info("virtual kernel memory layout:\n"
./arch/sh/mm/init.c:431: pr_info("virtual kernel memory layout:\n"
./arch/parisc/mm/init.c:619: printk("virtual kernel memory layout:\n"
匹配到二进制文件 ./arch/x86/boot/compressed/vmlinux.bin
./arch/x86/mm/init_32.c:762: printk(KERN_INFO "virtual kernel memory layout:\n"
匹配到二进制文件 ./arch/x86/mm/init_32.o
匹配到二进制文件 ./arch/x86/mm/built-in.o
匹配到二进制文件 ./arch/x86/built-in.o
./Documentation/arm64/memory.txt:56:For details of the virtual kernel memory layout please see the kernel
匹配到二进制文件 ./vmlinux
匹配到二进制文件 ./vmlinux.o
./arch/x86/mm/init_32.c:762
printk(KERN_INFO "virtual kernel memory layout:\n"
" fixmap : 0x%08lx - 0x%08lx (%4ld kB)\n"
#ifdef CONFIG_HIGHMEM
" pkmap : 0x%08lx - 0x%08lx (%4ld kB)\n"
#endif
" vmalloc : 0x%08l

x - 0x%08lx (%4ld MB)\n"
" lowmem : 0x%08lx - 0x%08lx (%4ld MB)\n"
" .init : 0x%08lx - 0x%08lx (%4ld kB)\n"
" .data : 0x%08lx - 0x%08lx (%4ld kB)\n"
" .text : 0x%08lx - 0x%08lx (%4ld kB)\n",
FIXADDR_START, FIXADDR_TOP,
(FIXADDR_TOP - FIXADDR_START) >> 10,
#ifdef CONFIG_HIGHMEM
PKMAP_BASE, PKMAP_BASE+LAST_PKMAP*PAGE_SIZE,
(LAST_PKMAP*PAGE_SIZE) >> 10,
#endif
VMALLOC_START, VMALLOC_END,
(VMALLOC_END - VMALLOC_START) >> 20,
(unsigned long)__va(0), (unsigned long)high_memory,
((unsigned long)high_memory - (unsigned long)__va(0)) >> 20,
(unsigned long)&__init_begin, (unsigned long)&__init_end,
((unsigned long)&__init_end -
(unsigned long)&__init_begin) >> 10,
(unsigned long)&_etext, (unsigned long)&_edata,
((unsigned long)&_edata - (unsigned long)&_etext) >> 10,
(unsigned long)&_text, (unsigned long)&_etext,
((unsigned long)&_etext - (unsigned long)&_text) >> 10);
[ 0.000000] virtual kernel memory layout:
[ 0.000000] fixmap : 0xfff17000 - 0xfffff000 ( 928 kB)
[ 0.000000] pkmap : 0xff800000 - 0xffc00000 (4096 kB)
[ 0.000000] vmalloc : 0xf7ffe000 - 0xff7fe000 ( 120 MB)
[ 0.000000] lowmem : 0xc0000000 - 0xf77fe000 ( 887 MB)
[ 0.000000] .init : 0xc16ae000 - 0xc1722000 ( 464 kB)
[ 0.000000] .data : 0xc149861e - 0xc16ac540 (2127 kB)
[ 0.000000] .text : 0xc1000000 - 0xc149861e (4705 kB)