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[libflat] Remove now-obsolete flatten_real_mode call
Flat real mode will have been set up as a side-effect of the
protected-mode call invoked during install_block() for .text16.early;
there is no need to do so explicitly.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
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mcb30 committed Jan 26, 2011
1 parent a84e152 commit 7f2d0f1
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Showing 2 changed files with 5 additions and 122 deletions.
5 changes: 4 additions & 1 deletion src/arch/i386/prefix/libprefix.S
Expand Up @@ -649,7 +649,10 @@ install_prealloc:
popl %esi

#ifndef KEEP_IT_REAL
/* Access high memory */
/* Access high memory by enabling the A20 gate. (We will
* already have 4GB segment limits as a result of calling
* install_block.)
*/
pushw %cs
pushw $1f
pushw %ax
Expand Down
122 changes: 1 addition & 121 deletions src/arch/i386/transitions/libflat.S
Expand Up @@ -21,124 +21,6 @@ FILE_LICENCE ( GPL2_OR_LATER )

.arch i386

#define CR0_PE 1

/****************************************************************************
* flatten_real_mode
*
* Set up 4GB segment limits
*
* Parameters:
* none
* Returns:
* none
* Corrupts:
* none
****************************************************************************
*/
/* GDT for protected-mode calls */
.section ".text16.early.data", "aw", @progbits
.align 16
flatten_gdt:
flatten_gdt_limit: .word flatten_gdt_length - 1
flatten_gdt_base: .long 0
.word 0 /* padding */
flatten_cs: /* 16-bit protected-mode flat code segment */
.equ FLAT_CS, flatten_cs - flatten_gdt
.word 0xffff, 0
.byte 0, 0x9b, 0x8f, 0
flatten_ss: /* 16-bit protected-mode flat stack segment */
.equ FLAT_SS, flatten_ss - flatten_gdt
.word 0xffff, 0
.byte 0, 0x93, 0x8f, 0
flatten_gdt_end:
.equ flatten_gdt_length, . - flatten_gdt
.size flatten_gdt, . - flatten_gdt

.section ".text16.early.data", "aw", @progbits
.align 16
flatten_saved_gdt:
.long 0, 0
.size flatten_saved_gdt, . - flatten_saved_gdt

.section ".text16.early", "awx", @progbits
.code16
flatten_real_mode:
/* Preserve registers and flags */
pushfl
pushl %eax
pushw %si
pushw %gs
pushw %fs
pushw %es
pushw %ds
pushw %ss

/* Set %ds for access to .text16.early.data variables */
pushw %cs
popw %ds

/* Preserve original GDT */
sgdt flatten_saved_gdt

/* Set up GDT bases */
xorl %eax, %eax
movw %cs, %ax
shll $4, %eax
addl $flatten_gdt, %eax
movl %eax, flatten_gdt_base
movw %cs, %ax
movw $flatten_cs, %si
call set_seg_base
movw %ss, %ax
movw $flatten_ss, %si
call set_seg_base

/* Switch temporarily to protected mode and set segment registers */
pushw %cs
pushw $2f
cli
data32 lgdt flatten_gdt
movl %cr0, %eax
orb $CR0_PE, %al
movl %eax, %cr0
ljmp $FLAT_CS, $1f
1: movw $FLAT_SS, %ax
movw %ax, %ss
movw %ax, %ds
movw %ax, %es
movw %ax, %fs
movw %ax, %gs
movl %cr0, %eax
andb $0!CR0_PE, %al
movl %eax, %cr0
lret
2: /* lret will ljmp to here */

/* Restore GDT, registers and flags */
data32 lgdt flatten_saved_gdt
popw %ss
popw %ds
popw %es
popw %fs
popw %gs
popw %si
popl %eax
popfl
ret
.size flatten_real_mode, . - flatten_real_mode

.section ".text16.early", "awx", @progbits
.code16
set_seg_base:
rolw $4, %ax
movw %ax, 2(%si)
andw $0xfff0, 2(%si)
movb %al, 4(%si)
andb $0x0f, 4(%si)
ret
.size set_seg_base, . - set_seg_base

/****************************************************************************
* test_a20_short, test_a20_long
*
Expand Down Expand Up @@ -403,7 +285,7 @@ enable_a20_method:
/****************************************************************************
* access_highmem (real mode far call)
*
* Open up access to high memory in flat real mode with A20 enabled
* Open up access to high memory with A20 enabled
*
* Parameters:
* none
Expand All @@ -419,7 +301,5 @@ enable_a20_method:
access_highmem:
/* Enable A20 line */
call enable_a20
/* Set up 4GB limits */
call flatten_real_mode
lret
.size access_highmem, . - access_highmem

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