diff --git a/src/arch/i386/prefix/libprefix.S b/src/arch/i386/prefix/libprefix.S index b820f2a3..d7cad05f 100644 --- a/src/arch/i386/prefix/libprefix.S +++ b/src/arch/i386/prefix/libprefix.S @@ -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) */