mirror of
https://github.com/torvalds/linux.git
synced 2024-11-08 21:21:47 +00:00
7806a49ab6
The use of base for %ebx in this file is arbitrary, *except* that we also use it to compute the real-mode segment. Therefore, make it so that r_base really is the true address to which %ebx points. This resolves kernel bugzilla 33302. Reported-and-tested-by: Alexey Zaytsev <alexey.zaytsev@gmail.com> Signed-off-by: H. Peter Anvin <hpa@zytor.com> Link: http://lkml.kernel.org/n/tip-08os5wi3yq1no0y4i5m4z7he@git.kernel.org
136 lines
3.8 KiB
ArmAsm
136 lines
3.8 KiB
ArmAsm
#include <linux/linkage.h>
|
|
#include <linux/init.h>
|
|
#include <asm/segment.h>
|
|
#include <asm/page_types.h>
|
|
|
|
/*
|
|
* The following code and data reboots the machine by switching to real
|
|
* mode and jumping to the BIOS reset entry point, as if the CPU has
|
|
* really been reset. The previous version asked the keyboard
|
|
* controller to pulse the CPU reset line, which is more thorough, but
|
|
* doesn't work with at least one type of 486 motherboard. It is easy
|
|
* to stop this code working; hence the copious comments.
|
|
*
|
|
* This code is called with the restart type (0 = BIOS, 1 = APM) in %eax.
|
|
*/
|
|
.section ".x86_trampoline","a"
|
|
.balign 16
|
|
.code32
|
|
ENTRY(machine_real_restart_asm)
|
|
r_base = .
|
|
/* Get our own relocated address */
|
|
call 1f
|
|
1: popl %ebx
|
|
subl $(1b - r_base), %ebx
|
|
|
|
/* Compute the equivalent real-mode segment */
|
|
movl %ebx, %ecx
|
|
shrl $4, %ecx
|
|
|
|
/* Patch post-real-mode segment jump */
|
|
movw (dispatch_table - r_base)(%ebx,%eax,2),%ax
|
|
movw %ax, (101f - r_base)(%ebx)
|
|
movw %cx, (102f - r_base)(%ebx)
|
|
|
|
/* Set up the IDT for real mode. */
|
|
lidtl (machine_real_restart_idt - r_base)(%ebx)
|
|
|
|
/*
|
|
* Set up a GDT from which we can load segment descriptors for real
|
|
* mode. The GDT is not used in real mode; it is just needed here to
|
|
* prepare the descriptors.
|
|
*/
|
|
lgdtl (machine_real_restart_gdt - r_base)(%ebx)
|
|
|
|
/*
|
|
* Load the data segment registers with 16-bit compatible values
|
|
*/
|
|
movl $16, %ecx
|
|
movl %ecx, %ds
|
|
movl %ecx, %es
|
|
movl %ecx, %fs
|
|
movl %ecx, %gs
|
|
movl %ecx, %ss
|
|
ljmpl $8, $1f - r_base
|
|
|
|
/*
|
|
* This is 16-bit protected mode code to disable paging and the cache,
|
|
* switch to real mode and jump to the BIOS reset code.
|
|
*
|
|
* The instruction that switches to real mode by writing to CR0 must be
|
|
* followed immediately by a far jump instruction, which set CS to a
|
|
* valid value for real mode, and flushes the prefetch queue to avoid
|
|
* running instructions that have already been decoded in protected
|
|
* mode.
|
|
*
|
|
* Clears all the flags except ET, especially PG (paging), PE
|
|
* (protected-mode enable) and TS (task switch for coprocessor state
|
|
* save). Flushes the TLB after paging has been disabled. Sets CD and
|
|
* NW, to disable the cache on a 486, and invalidates the cache. This
|
|
* is more like the state of a 486 after reset. I don't know if
|
|
* something else should be done for other chips.
|
|
*
|
|
* More could be done here to set up the registers as if a CPU reset had
|
|
* occurred; hopefully real BIOSs don't assume much. This is not the
|
|
* actual BIOS entry point, anyway (that is at 0xfffffff0).
|
|
*
|
|
* Most of this work is probably excessive, but it is what is tested.
|
|
*/
|
|
.code16
|
|
1:
|
|
xorl %ecx, %ecx
|
|
movl %cr0, %eax
|
|
andl $0x00000011, %eax
|
|
orl $0x60000000, %eax
|
|
movl %eax, %cr0
|
|
movl %ecx, %cr3
|
|
movl %cr0, %edx
|
|
andl $0x60000000, %edx /* If no cache bits -> no wbinvd */
|
|
jz 2f
|
|
wbinvd
|
|
2:
|
|
andb $0x10, %al
|
|
movl %eax, %cr0
|
|
.byte 0xea /* ljmpw */
|
|
101: .word 0 /* Offset */
|
|
102: .word 0 /* Segment */
|
|
|
|
bios:
|
|
ljmpw $0xf000, $0xfff0
|
|
|
|
apm:
|
|
movw $0x1000, %ax
|
|
movw %ax, %ss
|
|
movw $0xf000, %sp
|
|
movw $0x5307, %ax
|
|
movw $0x0001, %bx
|
|
movw $0x0003, %cx
|
|
int $0x15
|
|
|
|
END(machine_real_restart_asm)
|
|
|
|
.balign 16
|
|
/* These must match <asm/reboot.h */
|
|
dispatch_table:
|
|
.word bios - r_base
|
|
.word apm - r_base
|
|
END(dispatch_table)
|
|
|
|
.balign 16
|
|
machine_real_restart_idt:
|
|
.word 0xffff /* Length - real mode default value */
|
|
.long 0 /* Base - real mode default value */
|
|
END(machine_real_restart_idt)
|
|
|
|
.balign 16
|
|
ENTRY(machine_real_restart_gdt)
|
|
.quad 0 /* Self-pointer, filled in by PM code */
|
|
.quad 0 /* 16-bit code segment, filled in by PM code */
|
|
/*
|
|
* 16-bit data segment with the selector value 16 = 0x10 and
|
|
* base value 0x100; since this is consistent with real mode
|
|
* semantics we don't have to reload the segments once CR0.PE = 0.
|
|
*/
|
|
.quad GDT_ENTRY(0x0093, 0x100, 0xffff)
|
|
END(machine_real_restart_gdt)
|