kernel_optimize_test/arch/x86/boot/compressed/head_32.S
H. Peter Anvin 22a57f5896 x86, setup: Allow global variables and functions in the decompressor
In order for global variables and functions to work in the
decompressor, we need to fix up the GOT in assembly code.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
LKML-Reference: <4C57382E.8050501@zytor.com>
2010-08-02 15:34:44 -07:00

196 lines
3.9 KiB
ArmAsm

/*
* 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/init.h>
#include <linux/linkage.h>
#include <asm/segment.h>
#include <asm/page_types.h>
#include <asm/boot.h>
#include <asm/asm-offsets.h>
__HEAD
ENTRY(startup_32)
cld
/*
* Test KEEP_SEGMENTS flag to see if the bootloader is asking
* us to not reload segments
*/
testb $(1<<6), BP_loadflags(%esi)
jnz 1f
cli
movl $__BOOT_DS, %eax
movl %eax, %ds
movl %eax, %es
movl %eax, %fs
movl %eax, %gs
movl %eax, %ss
1:
/*
* 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 (BP_scratch+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
movl BP_kernel_alignment(%esi), %eax
decl %eax
addl %eax, %ebx
notl %eax
andl %eax, %ebx
#else
movl $LOAD_PHYSICAL_ADDR, %ebx
#endif
/* Target address to relocate to for decompression */
addl $z_extract_offset, %ebx
/* Set up the stack */
leal boot_stack_end(%ebx), %esp
/* Zero EFLAGS */
pushl $0
popfl
/*
* Copy the compressed kernel to the end of our buffer
* where decompression in place becomes safe.
*/
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
/*
* Jump to the relocated address.
*/
leal relocated(%ebx), %eax
jmp *%eax
ENDPROC(startup_32)
.text
relocated:
/*
* 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
/*
* Adjust our own GOT
*/
leal _got(%ebx), %edx
leal _egot(%ebx), %ecx
1:
cmpl %ecx, %edx
jae 2f
addl %ebx, (%edx)
addl $4, %edx
jmp 1b
2:
/*
* 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
#if CONFIG_RELOCATABLE
/*
* Find the address of the relocations.
*/
leal z_output_len(%ebp), %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 (%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
/*
* Stack and heap for uncompression
*/
.bss
.balign 4
boot_heap:
.fill BOOT_HEAP_SIZE, 1, 0
boot_stack:
.fill BOOT_STACK_SIZE, 1, 0
boot_stack_end: