diff options
Diffstat (limited to 'arch/x86/boot/compressed/head_32.S')
| -rw-r--r-- | arch/x86/boot/compressed/head_32.S | 180 |
1 files changed, 180 insertions, 0 deletions
diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S new file mode 100644 index 0000000..f35ea22 --- /dev/null +++ b/arch/x86/boot/compressed/head_32.S @@ -0,0 +1,180 @@ +/* + * linux/boot/head.S + * + * Copyright (C) 1991, 1992, 1993 Linus Torvalds + */ + +/* + * head.S contains the 32-bit startup code. + * + * NOTE!!! Startup happens at absolute address 0x00001000, which is also where + * the page directory will exist. The startup code will be overwritten by + * the page directory. [According to comments etc elsewhere on a compressed + * kernel it will end up at 0x1000 + 1Mb I hope so as I assume this. - AC] + * + * Page 0 is deliberately kept safe, since System Management Mode code in + * laptops may need to access the BIOS data stored there. This is also + * useful for future device drivers that either access the BIOS via VM86 + * mode. + */ + +/* + * High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996 + */ +.text + +#include <linux/linkage.h> +#include <asm/segment.h> +#include <asm/page.h> +#include <asm/boot.h> + +.section ".text.head","ax",@progbits + .globl startup_32 + +startup_32: + cld + cli + movl $(__BOOT_DS),%eax + movl %eax,%ds + movl %eax,%es + movl %eax,%fs + movl %eax,%gs + movl %eax,%ss + +/* Calculate the delta between where we were compiled to run + * at and where we were actually loaded at. This can only be done + * with a short local call on x86. Nothing else will tell us what + * address we are running at. The reserved chunk of the real-mode + * data at 0x1e4 (defined as a scratch field) are used as the stack + * for this calculation. Only 4 bytes are needed. + */ + leal (0x1e4+4)(%esi), %esp + call 1f +1: popl %ebp + subl $1b, %ebp + +/* %ebp contains the address we are loaded at by the boot loader and %ebx + * contains the address where we should move the kernel image temporarily + * for safe in-place decompression. + */ + +#ifdef CONFIG_RELOCATABLE + movl %ebp, %ebx + addl $(CONFIG_PHYSICAL_ALIGN - 1), %ebx + andl $(~(CONFIG_PHYSICAL_ALIGN - 1)), %ebx +#else + movl $LOAD_PHYSICAL_ADDR, %ebx +#endif + + /* Replace the compressed data size with the uncompressed size */ + subl input_len(%ebp), %ebx + movl output_len(%ebp), %eax + addl %eax, %ebx + /* Add 8 bytes for every 32K input block */ + shrl $12, %eax + addl %eax, %ebx + /* Add 32K + 18 bytes of extra slack */ + addl $(32768 + 18), %ebx + /* Align on a 4K boundary */ + addl $4095, %ebx + andl $~4095, %ebx + +/* Copy the compressed kernel to the end of our buffer + * where decompression in place becomes safe. + */ + pushl %esi + leal _end(%ebp), %esi + leal _end(%ebx), %edi + movl $(_end - startup_32), %ecx + std + rep + movsb + cld + popl %esi + +/* Compute the kernel start address. + */ +#ifdef CONFIG_RELOCATABLE + addl $(CONFIG_PHYSICAL_ALIGN - 1), %ebp + andl $(~(CONFIG_PHYSICAL_ALIGN - 1)), %ebp +#else + movl $LOAD_PHYSICAL_ADDR, %ebp +#endif + +/* + * Jump to the relocated address. + */ + leal relocated(%ebx), %eax + jmp *%eax +.section ".text" +relocated: + +/* + * Clear BSS + */ + xorl %eax,%eax + leal _edata(%ebx),%edi + leal _end(%ebx), %ecx + subl %edi,%ecx + cld + rep + stosb + +/* + * Setup the stack for the decompressor + */ + leal stack_end(%ebx), %esp + +/* + * Do the decompression, and jump to the new kernel.. + */ + movl output_len(%ebx), %eax + pushl %eax + pushl %ebp # output address + movl input_len(%ebx), %eax + pushl %eax # input_len + leal input_data(%ebx), %eax + pushl %eax # input_data + leal _end(%ebx), %eax + pushl %eax # end of the image as third argument + pushl %esi # real mode pointer as second arg + call decompress_kernel + addl $20, %esp + popl %ecx + +#if CONFIG_RELOCATABLE +/* Find the address of the relocations. + */ + movl %ebp, %edi + addl %ecx, %edi + +/* Calculate the delta between where vmlinux was compiled to run + * and where it was actually loaded. + */ + movl %ebp, %ebx + subl $LOAD_PHYSICAL_ADDR, %ebx + jz 2f /* Nothing to be done if loaded at compiled addr. */ +/* + * Process relocations. + */ + +1: subl $4, %edi + movl 0(%edi), %ecx + testl %ecx, %ecx + jz 2f + addl %ebx, -__PAGE_OFFSET(%ebx, %ecx) + jmp 1b +2: +#endif + +/* + * Jump to the decompressed kernel. + */ + xorl %ebx,%ebx + jmp *%ebp + +.bss +.balign 4 +stack: + .fill 4096, 1, 0 +stack_end: |
