diff options
Diffstat (limited to 'bootasm.S')
| -rw-r--r-- | bootasm.S | 21 |
1 files changed, 12 insertions, 9 deletions
@@ -5,15 +5,16 @@ # memory at physical address 0x7c00 and starts executing in real mode # with %cs=0 %ip=7c00. -.set CSEG32, 0x8 # kernel code segment selector -.set DSEG32, 0x10 # kernel data segment selector -.set CR0_PE, 0x1 # protected mode enable flag +#define SEG_KCODE 1 // kernel code +#define SEG_KDATA 2 // kernel data+stack +#define SEG_KCPU 3 // kernel per-cpu data + +#define CR0_PE 1 // protected mode enable bit .code16 # Assemble for 16-bit mode .globl start start: cli # Disable interrupts - cld # String operations increment # Set up the important data segment registers (DS, ES, SS). xorw %ax,%ax # Segment number zero @@ -53,18 +54,19 @@ seta20.2: # Jump to next instruction, but in 32-bit code segment. # Switches processor into 32-bit mode. - ljmp $CSEG32, $start32 + ljmp $(SEG_KCODE<<3), $start32 .code32 # Assemble for 32-bit mode start32: # Set up the protected-mode data segment registers - movw $DSEG32, %ax # Our data segment selector + movw $(SEG_KDATA<<3), %ax # Our data segment selector movw %ax, %ds # -> DS: Data Segment movw %ax, %es # -> ES: Extra Segment + movw %ax, %ss # -> SS: Stack Segment + movw $(SEG_KCPU<<3), %ax # Our per-cpu segment selector movw %ax, %fs # -> FS movw %ax, %gs # -> GS - movw %ax, %ss # -> SS: Stack Segment - + # Set up the stack pointer and call into C. movl $start, %esp call bootmain @@ -85,7 +87,8 @@ gdt: SEG_NULLASM # null seg SEG_ASM(STA_X|STA_R, 0x0, 0xffffffff) # code seg SEG_ASM(STA_W, 0x0, 0xffffffff) # data seg + SEG_ASM(STA_W, 0x100, 0xffffffff) # per-cpu data seg; 0x100 is okay for now gdtdesc: - .word 0x17 # sizeof(gdt) - 1 + .word 0x1f # sizeof(gdt) - 1 .long gdt # address gdt |