From 5c73cacd283b9c17fd5777f29707ae87f8150714 Mon Sep 17 00:00:00 2001
From: Amelia Coutard <eliottulio.coutard@gmail.com>
Date: Thu, 5 May 2022 19:11:06 +0200
Subject: [PATCH] Moved the kernel to 1MiB (to avoid problems with low
memory-mapped IO).
Also had to change the low mapping to 2GiB instead of 2MiB, because the stack finished after 2MiB.
---
linker.ld | 2 ++
src/boot.S | 27 ++++++++++-----------------
2 files changed, 12 insertions(+), 17 deletions(-)
diff --git a/linker.ld b/linker.ld
index 60de5eb..7c4e9f6 100644
--- a/linker.ld
+++ b/linker.ld
@@ -3,6 +3,8 @@ ENTRY(_start)
KERNEL_VMA = 0xFFFFFFFF80000000;
SECTIONS {
+ . = 1M;
+
.bootstrap ALIGN(4K) : {
*(.multiboot_header)
. = ALIGN(4K);
diff --git a/src/boot.S b/src/boot.S
index e745a0f..53a9162 100644
--- a/src/boot.S
+++ b/src/boot.S
@@ -77,16 +77,21 @@ TSS:
TSS_END:
.set TSS_SIZE, TSS_END - TSS
.align 0x1000
+#TODO replace with actual RAM detection
+.globl test_ram
+test_ram: .quad 256
+ .quad 0
+ .skip 0x1000 * 256 - 16 # 1MiB RAM
+PDPT_low: .quad 0x83
+ .quad 0x83 + 1024 * 1024 * 1024
+ .skip 0x1000 - 16
PDPT_high: .skip 0x1000 - 16
.quad 0x83
.quad 0x83 + 1024 * 1024 * 1024
.section .bss
.align 0x1000
-PML4T: .skip 0x1000
-PDPT_low: .skip 0x1000
-PDT: .skip 0x1000
-PT: .skip 0x1000
+PML4T: .skip 0x1000
phys_mem_map: .skip 0x1000 * 128 - 8
.align 16
stack_bottom:
@@ -152,21 +157,9 @@ _start:
mov $PML4T - KERNEL_VMA, %eax
mov %eax, %cr3
mov $PDPT_low - KERNEL_VMA + 3, %eax
- mov %eax, PML4T - KERNEL_VMA + 0 * 8
+ mov %eax, PML4T - KERNEL_VMA + 0 * 8
mov $PDPT_high - KERNEL_VMA + 3, %eax
mov %eax, PML4T - KERNEL_VMA + 511 * 8
- mov $PDT - KERNEL_VMA + 3, %eax
- mov %eax, PDPT_low - KERNEL_VMA + 0 * 8
- mov $PT - KERNEL_VMA + 3, %eax
- mov %eax, PDT - KERNEL_VMA + 0 * 8
-
- mov $PT - KERNEL_VMA, %edi
- mov $0x0003, %ebx
- mov $512, %ecx
-1: mov %ebx, (%edi)
- add $0x1000, %ebx
- add $8, %edi
- loop 1b
# Enable PAE paging:
mov %cr4, %eax
--
2.46.0