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x86: bios: Synchronize stack between real and protected mode

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PCI option rom may use different SS during its execution, so it is not
safe to assume esp pointed to the same location in the protected mode.

Signed-off-by: Jian Luo <jian.luo4@boschrexroth.de>
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>
This commit is contained in:
Jian Luo 2015-07-06 16:42:06 +08:00 • committed by Simon Glass
parent b018a8c716
commit 7b5c349890
1 changed files with 23 additions and 0 deletions
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23
arch/x86/lib/bios_asm.S
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@ -246,6 +246,9 @@ __interrupt_handler_16bit = PTR_TO_REAL_MODE(.)
push %fs
push %gs
/* Save real mode SS */
movw %ss, %cs:__realmode_ss
/* Clear DF to not break ABI assumptions */
cld
@ -258,12 +261,29 @@ __interrupt_handler_16bit = PTR_TO_REAL_MODE(.)
enter_protected_mode
/*
* Now we are in protected mode. We need compute the right ESP based
* on saved real mode SS otherwise interrupt_handler() won't get
* correct parameters from the stack.
*/
movzwl %cs:__realmode_ss, %ecx
shll $4, %ecx
addl %ecx, %esp
/* Call the C interrupt handler */
movl $interrupt_handler, %eax
call *%eax
/* Restore real mode ESP based on saved SS */
movzwl %cs:__realmode_ss, %ecx
shll $4, %ecx
subl %ecx, %esp
enter_real_mode
/* Restore real mode SS */
movw %cs:__realmode_ss, %ss
/*
* Restore all registers, including those manipulated by the C
* handler
@ -276,6 +296,9 @@ __interrupt_handler_16bit = PTR_TO_REAL_MODE(.)
popal
iret
__realmode_ss = PTR_TO_REAL_MODE(.)
.word 0
.globl asm_realmode_code_size
asm_realmode_code_size:
.long . - asm_realmode_code