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grub越过实模式直接跳转到保护模式的内核，找到自己的位置
ENTRY(startup_32) //head_32.S (arch\x86\boot\compressed) 3871 2010/8/3 testb $(1<<6), BP_loadflags(%esi) //来源于grub的struct linux_kernel_params.loadflags jnz 1f cli movl $__BOOT_DS, %eax movl %eax, %ds movl %eax, %es movl %eax, %fs movl %eax, %gs movl %eax, %ss1: leal (BP_scratch+4)(%esi), %esp //建立临时堆栈, 只有4Byte, 来源于grub的struct linux_kernel_params.padding8[0x1e8 - 0x1e4] call 1f1: popl %ebp subl $1b, %ebp //ebp为 startup_32 实际运行地址, 也就是bootloader加载地址 movl $LOAD_PHYSICAL_ADDR, %ebx //LOAD_PHYSICAL_ADDR为linux内核解压缩后的起始物理地址 =>#define LOAD_PHYSICAL_ADDR ((CONFIG_PHYSICAL_START \ + (CONFIG_PHYSICAL_ALIGN - 1)) \ & ~(CONFIG_PHYSICAL_ALIGN - 1)) [xxx@cliffr linux-2.6.32]$ ll .config -rw-r--r--. 1 root root 101479 Feb 8 2020 .config [xxx@cliffr linux-2.6.32]$ cat .config | grep CONFIG_PHYSICAL_START CONFIG_PHYSICAL_START=0x400000 [xxx@cliffr linux-2.6.32]$ cat .config | grep CONFIG_PHYSICAL_ALIGN CONFIG_PHYSICAL_ALIGN=0x400000 [xxx@cliffr linux-2.6.32]$
搬移内核，为解压缩做准备
/* Target address to relocate to for decompression */ addl $z_extract_offset, %ebx //搬移当前内核, ebx为搬移后的压缩内核物理地址 /* Set up the stack */ leal boot_stack_end(%ebx), %esp /* 搬移当前内核, 从后向前搬移, 搬移后, ebx为新的 startup_32的物理地址 */ pushl %esi leal (_bss-4)(%ebp), %esi leal (_bss-4)(%ebx), %edi movl $(_bss - startup_32), %ecx shrl $2, %ecx std rep movsl cld popl %esi /* 调整eip地址 */ leal relocated(%ebx), %eax jmp *%eax ENDPROC(startup_32) .textrelocated:/* * Clear BSS (stack is currently empty) */ xorl %eax, %eax leal _bss(%ebx), %edi leal _ebss(%ebx), %ecx subl %edi, %ecx shrl $2, %ecx rep stosl
解压缩内核，并跳转到解压缩后的内核
/* * Do the decompression, and jump to the new kernel.. */ leal z_extract_offset_negative(%ebx), %ebp /* push arguments for decompress_kernel: */ pushl %ebp /* output address */ pushl $z_input_len /* input_len */ leal input_data(%ebx), %eax pushl %eax /* input_data */ leal boot_heap(%ebx), %eax pushl %eax /* heap area */ pushl %esi /* real mode pointer */ call decompress_kernel addl $20, %esp /* * Jump to the decompressed kernel. */ xorl %ebx, %ebx jmp *%ebp/* * Stack and heap for uncompression */ .bss .balign 4boot_heap: .fill BOOT_HEAP_SIZE, 1, 0boot_stack: .fill BOOT_STACK_SIZE, 1, 0boot_stack_end:
Linux Kernel 2.6.37 启动过程：startup_32
http://blog.chinaunix.net/uid-1701789-id-148056.htmllinux内核-x86_32位内核启动流程
https://blog.csdn.net/chentaoxie/article/details/86352305[原创]linux-5.6.6 内核引导
https://bbs.pediy.com/thread-261718.htmllinux有意避开了分段机制
https://blog.csdn.net/u012566181/article/details/38253937?utm_source=blogxgwz64. 切换到64位模式
https://blog.csdn.net/GerryLee93/article/details/106475973内核引导过程. Part 4.
切换到64位模式 https://www.javascriptc.com/books/linux-insides-cn/Booting/linux-bootstrap-4.html混沌初开--内核启动笔记
http://www.voidcn.com/article/p-dbwptazw-up.htmlhttps://blog.csdn.net/richardysteven/article/details/52629731
Linux内核启动流程分析(一)
http://blog.chinaunix.net/uid-25909619-id-3380535.htmlLinux内存初始化（汇编部分）
https://blog.csdn.net/shuanhuoguo/article/details/80122253Linux内存初始化(汇编部分)
https://www.sohu.com/a/63559761_115128内核启动之启动内核——startup_32
https://blog.csdn.net/yu616568/article/details/7581919Linux内核启动过程分析
https://blog.csdn.net/chuifuhuo6864/article/details/100883445