From ef52650c4a0723b242deb72ce2726f6846a6e986 Mon Sep 17 00:00:00 2001
From: dzwdz
Date: Sat, 21 May 2022 21:24:15 +0200
Subject: kernel/i386: only map what's absolutely necessary in the user

---
 src/kernel/arch/i386/interrupts/idt.c      |  2 +-
 src/kernel/arch/i386/interrupts/isr_stub.s | 31 +++++++++++++++++++-----------
 2 files changed, 21 insertions(+), 12 deletions(-)

(limited to 'src/kernel/arch/i386/interrupts')

diff --git a/src/kernel/arch/i386/interrupts/idt.c b/src/kernel/arch/i386/interrupts/idt.c
index d27bc61..d295d84 100644
--- a/src/kernel/arch/i386/interrupts/idt.c
+++ b/src/kernel/arch/i386/interrupts/idt.c
@@ -23,7 +23,7 @@ struct lidt_arg {
 	uint32_t base;
 } __attribute__((packed));
 
-
+__attribute__((section(".text.early")))
 static struct idt_entry IDT[256];
 static struct lidt_arg lidt_arg;
 
diff --git a/src/kernel/arch/i386/interrupts/isr_stub.s b/src/kernel/arch/i386/interrupts/isr_stub.s
index 8efb1b7..9a903f6 100644
--- a/src/kernel/arch/i386/interrupts/isr_stub.s
+++ b/src/kernel/arch/i386/interrupts/isr_stub.s
@@ -1,4 +1,4 @@
-.section .text
+.section .text.early
 
 .global _isr_stubs
 _isr_stubs:
@@ -9,25 +9,34 @@ _isr_stubs:
 .endr
 
 _isr_stage2:
-	cld
+	cli
 
 	// convert the return address into the vector nr
 	pop %eax
 	add $-_isr_stubs, %eax
 	shr $3, %eax
 
-		// disable paging, if present
-		// it's done here so the stuff on the stack is in the right order
-		mov %cr0, %ebx
-		push %ebx
-		and $0x7FFFFFFF, %ebx
-		mov %ebx, %cr0
+	// disable paging, if present
+	mov %cr0, %ebx
+	push %ebx // push original cr0
+	and $0x7FFFFFFF, %ebx
+	mov %ebx, %cr0
 
-	push %eax       // push the vector nr
+	mov %esp, %ebp
+	mov $_bss_end, %esp // switch to kernel stack
+	push %eax // push the vector nr
 	call isr_stage3
-	add $4, %esp    // "pop" the vector nr
-	pop %eax        // restore old cr0
+
+	mov %ebp, %esp // switch back to isr_stack
+	pop %eax // restore old cr0
 	mov %eax, %cr0
 
 	popal
 	iret
+
+.align 8
+_ist_stack_btm:
+// TODO overflow check
+.skip 64 // seems to be enough
+.global _isr_stack_top
+_isr_stack_top:
-- 
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