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authorRuss Cox <[email protected]>2009-07-11 19:15:32 -0700
committerRuss Cox <[email protected]>2009-07-11 19:15:32 -0700
commit887f19686cf377db55953dac651ca8147c268092 (patch)
tree4657092bb085b53a043e2af0f885ba6d3c880b71
parent8b75366ce4ae7ad5f77225b247d097955574ba0b (diff)
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bootasm cleanup
-rw-r--r--bootasm.S3
-rw-r--r--bootother.S21
2 files changed, 12 insertions, 12 deletions
diff --git a/bootasm.S b/bootasm.S
index 4b2e012..0d8f2a5 100644
--- a/bootasm.S
+++ b/bootasm.S
@@ -86,8 +86,7 @@ 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 0x1f # sizeof(gdt) - 1
+ .word (gdtdesc - gdt - 1) # sizeof(gdt) - 1
.long gdt # address gdt
diff --git a/bootother.S b/bootother.S
index cb3ff4c..47f547e 100644
--- a/bootother.S
+++ b/bootother.S
@@ -19,15 +19,15 @@
# - it uses the address at start-4 for the %esp
# - it jumps to the address at start-8 instead of calling bootmain
-.set PROT_MODE_CSEG, 0x8 # kernel code segment selector
-.set PROT_MODE_DSEG, 0x10 # kernel data segment selector
-.set CR0_PE_ON, 0x1 # protected mode enable flag
+#define SEG_KCODE 1 // kernel code
+#define SEG_KDATA 2 // kernel data+stack
+#define CR0_PE 1 // protected mode enable bit
+
+.code16 # Assemble for 16-bit mode
.globl start
start:
- .code16 # Assemble for 16-bit mode
cli # Disable interrupts
- cld # String operations increment
# Set up the important data segment registers (DS, ES, SS).
xorw %ax,%ax # Segment number zero
@@ -42,22 +42,23 @@ start:
# effective memory map does not change during the switch.
lgdt gdtdesc
movl %cr0, %eax
- orl $CR0_PE_ON, %eax
+ orl $CR0_PE, %eax
movl %eax, %cr0
# Jump to next instruction, but in 32-bit code segment.
# Switches processor into 32-bit mode.
- ljmp $PROT_MODE_CSEG, $protcseg
+ ljmp $(SEG_KCODE<<3), $protcseg
.code32 # Assemble for 32-bit mode
protcseg:
# Set up the protected-mode data segment registers
- movw $PROT_MODE_DSEG, %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 $0, %ax # Zero segments not ready for use
movw %ax, %fs # -> FS
movw %ax, %gs # -> GS
- movw %ax, %ss # -> SS: Stack Segment
movl start-4, %esp
movl start-8, %eax
@@ -81,5 +82,5 @@ gdt:
SEG_ASM(STA_W, 0x0, 0xffffffff) # data seg
gdtdesc:
- .word 0x17 # sizeof(gdt) - 1
+ .word (gdtdesc - gdt - 1) # sizeof(gdt) - 1
.long gdt # address gdt