linux/arch/i386/boot/compressed/head.S
Eric W. Biederman 3d345e3fc9 [PATCH] kexec: x86: add CONFIG_PYSICAL_START
For one kernel to report a crash another kernel has created we need
to have 2 kernels loaded simultaneously in memory.  To accomplish this
the two kernels need to built to run at different physical addresses.

This patch adds the CONFIG_PHYSICAL_START option to the x86 kernel
so we can do just that.  You need to know what you are doing and
the ramifications are before changing this value, and most users
won't care so I have made it depend on CONFIG_EMBEDDED

bzImage kernels will work and run at a different address when compiled
with this option but they will still load at 1MB.  If you need a kernel
loaded at a different address as well you need to boot a vmlinux.

Signed-off-by: Eric Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-25 16:24:48 -07:00

129 lines
2.8 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/linkage.h>
#include <asm/segment.h>
#include <asm/page.h>
.globl startup_32
startup_32:
cld
cli
movl $(__BOOT_DS),%eax
movl %eax,%ds
movl %eax,%es
movl %eax,%fs
movl %eax,%gs
lss stack_start,%esp
xorl %eax,%eax
1: incl %eax # check that A20 really IS enabled
movl %eax,0x000000 # loop forever if it isn't
cmpl %eax,0x100000
je 1b
/*
* Initialize eflags. Some BIOS's leave bits like NT set. This would
* confuse the debugger if this code is traced.
* XXX - best to initialize before switching to protected mode.
*/
pushl $0
popfl
/*
* Clear BSS
*/
xorl %eax,%eax
movl $_edata,%edi
movl $_end,%ecx
subl %edi,%ecx
cld
rep
stosb
/*
* Do the decompression, and jump to the new kernel..
*/
subl $16,%esp # place for structure on the stack
movl %esp,%eax
pushl %esi # real mode pointer as second arg
pushl %eax # address of structure as first arg
call decompress_kernel
orl %eax,%eax
jnz 3f
popl %esi # discard address
popl %esi # real mode pointer
xorl %ebx,%ebx
ljmp $(__BOOT_CS), $__PHYSICAL_START
/*
* We come here, if we were loaded high.
* We need to move the move-in-place routine down to 0x1000
* and then start it with the buffer addresses in registers,
* which we got from the stack.
*/
3:
movl $move_routine_start,%esi
movl $0x1000,%edi
movl $move_routine_end,%ecx
subl %esi,%ecx
addl $3,%ecx
shrl $2,%ecx
cld
rep
movsl
popl %esi # discard the address
popl %ebx # real mode pointer
popl %esi # low_buffer_start
popl %ecx # lcount
popl %edx # high_buffer_start
popl %eax # hcount
movl $__PHYSICAL_START,%edi
cli # make sure we don't get interrupted
ljmp $(__BOOT_CS), $0x1000 # and jump to the move routine
/*
* Routine (template) for moving the decompressed kernel in place,
* if we were high loaded. This _must_ PIC-code !
*/
move_routine_start:
movl %ecx,%ebp
shrl $2,%ecx
rep
movsl
movl %ebp,%ecx
andl $3,%ecx
rep
movsb
movl %edx,%esi
movl %eax,%ecx # NOTE: rep movsb won't move if %ecx == 0
addl $3,%ecx
shrl $2,%ecx
rep
movsl
movl %ebx,%esi # Restore setup pointer
xorl %ebx,%ebx
ljmp $(__BOOT_CS), $__PHYSICAL_START
move_routine_end: