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[prefix] Move flatten_real_mode to .text16.early

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The flatten_real_mode routine is not needed until after decompressing
.text16.early, and currently performs various contortions to
compensate for the fact that .prefix may not be writable.  Move
flatten_real_mode to .text16.early to save on (compressed) binary size
and simplify the code.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown 2010-04-20 12:59:48 +01:00
parent 9068249e24
commit d931d4bd9c
1 changed files with 32 additions and 42 deletions
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74
src/arch/i386/prefix/libprefix.S
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@ -233,7 +233,7 @@ print_kill_line:
.size print_kill_line, . - print_kill_line
/****************************************************************************
* flatten_real_mode
* flatten_real_mode (real-mode far call)
*
* Set up 4GB segment limits
*
@ -248,9 +248,8 @@ print_kill_line:
#ifndef KEEP_IT_REAL
/* GDT for protected-mode calls */
.section ".prefix.lib", "awx", @progbits
.section ".text16.early.data", "aw", @progbits
.align 16
flatten_vars:
flatten_gdt:
flatten_gdt_limit: .word flatten_gdt_length - 1
flatten_gdt_base: .long 0
@ -267,62 +266,50 @@ flatten_gdt_end:
.equ flatten_gdt_length, . - flatten_gdt
.size flatten_gdt, . - flatten_gdt
.section ".prefix.lib", "awx", @progbits
.section ".text16.early.data", "aw", @progbits
.align 16
flatten_saved_gdt:
.long 0, 0
.size flatten_saved_gdt, . - flatten_saved_gdt
.equ flatten_vars_size, . - flatten_vars
#define FLATTEN_VAR(x) ( -flatten_vars_size + ( (x) - flatten_vars ) )
.section ".prefix.lib", "awx", @progbits
.section ".text16.early", "awx", @progbits
.code16
flatten_real_mode:
/* Preserve registers and flags, allocate local variable block */
pushw %bp
movw %sp, %bp
subw $flatten_vars_size, %sp
andw $0xfff0, %sp
/* Preserve registers and flags */
pushfl
pushl %eax
pushl %edi
pushw %si
pushw %cx
pushw %gs
pushw %fs
pushw %es
pushw %ds
pushw %ss
/* Fill local variable block and preserve GDT */
pushw %ss
popw %es
movw $flatten_vars, %si
leaw FLATTEN_VAR(flatten_vars)(%bp), %di
movw $flatten_vars_size, %cx
cs rep movsb
sgdt FLATTEN_VAR(flatten_saved_gdt)(%bp)
/* 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 %ss, %ax
shll $4, %eax
movzwl %bp, %edi
addr32 leal FLATTEN_VAR(flatten_gdt)(%eax, %edi), %eax
movl %eax, FLATTEN_VAR(flatten_gdt_base)(%bp)
movw %cs, %ax
movw $FLATTEN_VAR(flatten_cs), %di
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_VAR(flatten_ss), %di
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_VAR(flatten_gdt)(%bp)
data32 lgdt flatten_gdt
movl %cr0, %eax
orb $CR0_PE, %al
movl %eax, %cr0
@ -340,28 +327,26 @@ flatten_real_mode:
2: /* lret will ljmp to here */
/* Restore GDT, registers and flags */
data32 lgdt FLATTEN_VAR(flatten_saved_gdt)(%bp)
data32 lgdt flatten_saved_gdt
popw %ss
popw %ds
popw %es
popw %fs
popw %gs
popw %cx
popw %si
popl %edi
popl %eax
popfl
movw %bp, %sp
popw %bp
ret
lret
.size flatten_real_mode, . - flatten_real_mode
.section ".text16.early", "awx", @progbits
.code16
set_seg_base:
rolw $4, %ax
movw %ax, 2(%bp,%di)
andw $0xfff0, 2(%bp,%di)
movb %al, 4(%bp,%di)
andb $0x0f, 4(%bp,%di)
movw %ax, 2(%si)
andw $0xfff0, 2(%si)
movb %al, 4(%si)
andb $0x0f, 4(%si)
ret
.size set_seg_base, . - set_seg_base
@ -650,7 +635,12 @@ install_prealloc:
/* Open up access to payload */
#ifndef KEEP_IT_REAL
/* Flatten real mode */
call flatten_real_mode
pushw %cs
pushw $1f
pushw %ax
pushw $flatten_real_mode
lret
1:
#endif
/* Calculate physical address of payload (i.e. first source) */