From 7ea16c73d587f804079e45b46746e2a456ce6d2e Mon Sep 17 00:00:00 2001
From: Jeremy Soller <jackpot51@gmail.com>
Date: Thu, 18 Aug 2016 07:56:47 -0600
Subject: [PATCH] Prepare for higher half - map entire lower 4 GB
---
x86/kernel.ld | 26 +++++++++++++++++---------
x86/startup-x86_64.asm | 11 ++++++++---
2 files changed, 25 insertions(+), 12 deletions(-)
diff --git a/x86/kernel.ld b/x86/kernel.ld
index 19f0f2c..09d9958 100644
--- a/x86/kernel.ld
+++ b/x86/kernel.ld
@@ -1,31 +1,38 @@
ENTRY(kstart)
+OUTPUT_FORMAT(elf64-x86-64)
+
+KERNEL_OFFSET = 0;
SECTIONS {
- kernel_base = 0x101000;
- . = kernel_base;
+ . = 0x100000;
+
+ . += SIZEOF_HEADERS;
+ . = ALIGN(4096);
+
+ . += KERNEL_OFFSET;
- .text : AT(ADDR(.text) - kernel_base) {
+ .text : AT(ADDR(.text) - KERNEL_OFFSET) {
__text_start = .;
*(.text*)
. = ALIGN(4096);
__text_end = .;
}
- .rodata : AT(ADDR(.rodata) - kernel_base) {
+ .rodata : AT(ADDR(.rodata) - KERNEL_OFFSET) {
__rodata_start = .;
*(.rodata*)
. = ALIGN(4096);
__rodata_end = .;
}
- .data : AT(ADDR(.data) - kernel_base) {
+ .data : AT(ADDR(.data) - KERNEL_OFFSET) {
__data_start = .;
*(.data*)
. = ALIGN(4096);
__data_end = .;
}
- .bss : AT(ADDR(.bss) - kernel_base) {
+ .bss : AT(ADDR(.bss) - KERNEL_OFFSET) {
__bss_start = .;
*(.bss*)
. = ALIGN(4096);
@@ -33,8 +40,9 @@ SECTIONS {
}
/DISCARD/ : {
- *(.comment)
- *(.eh_frame)
- *(.rel.eh_frame)
+ *(.comment*)
+ *(.eh_frame*)
+ *(.note*)
+ *(.rel.eh_frame*)
}
}
diff --git a/x86/startup-x86_64.asm b/x86/startup-x86_64.asm
index 1e4c57a..bd5a6db 100644
--- a/x86/startup-x86_64.asm
+++ b/x86/startup-x86_64.asm
@@ -53,7 +53,7 @@ startup_arch:
xor edi, edi
xor eax, eax
- mov ecx, 3 * 4096 / 4 ;PML4, PDP, PD / moves 4 Bytes at once
+ mov ecx, 6 * 4096 / 4 ;PML4, PDP, 4 PD / moves 4 Bytes at once
cld
rep stosd
@@ -63,12 +63,15 @@ startup_arch:
add edi, 0x1000
;Link last PML4 to PML4
mov DWORD [es:edi - 8], 0x70000 | 1 << 1 | 1
- ;Link first PDP to PD
+ ;Link first four PDP to PD
mov DWORD [es:edi], 0x72000 | 1 << 1 | 1
+ mov DWORD [es:edi + 8], 0x73000 | 1 << 1 | 1
+ mov DWORD [es:edi + 16], 0x74000 | 1 << 1 | 1
+ mov DWORD [es:edi + 24], 0x75000 | 1 << 1 | 1
add edi, 0x1000
;Link all PD's (512 per PDP, 2MB each)y
mov ebx, 1 << 7 | 1 << 1 | 1
- mov ecx, 512
+ mov ecx, 4*512
.setpd:
mov [es:edi], ebx
add ebx, 0x200000
@@ -100,6 +103,8 @@ startup_arch:
or ebx, 1 << 31 | 1 << 16 | 1 ;Bit 31: Paging, Bit 16: write protect kernel, Bit 0: Protected Mode
mov cr0, ebx
+ xchg bx, bx
+
; far jump to enable Long Mode and load CS with 64 bit segment
jmp gdt.kernel_code:long_mode
--
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