5 files changed, 57 insertions, 43 deletions

diff --git a/src/kernel/arch/i386/gdt/gdt.c b/src/kernel/arch/i386/gdt/gdt.c
index 56df995..f016caa 100644
--- a/src/kernel/arch/i386/gdt/gdt.c
+++ b/src/kernel/arch/i386/gdt/gdt.c
@@ -4,6 +4,7 @@
 #include <stdbool.h>
 #include <stdint.h>
 
+extern char _isr_stack_top;
 
 struct gdt_entry {
 	uint64_t limit_low  : 16;
@@ -37,7 +38,9 @@ struct lgdt_arg {
 	uint32_t base;
 } __attribute__((packed));
 
+__attribute__((section(".text.early")))
 static struct gdt_entry GDT[SEG_end];
+__attribute__((section(".text.early")))
 static struct tss_entry TSS;
 static struct lgdt_arg lgdt_arg; // probably doesn't need to be global
 
@@ -80,7 +83,7 @@ static void gdt_prepare(void) {
 	// tss
 	memset(&TSS, 0, sizeof(TSS));
 	TSS.ss0 = SEG_r0data << 3; // kernel data segment
-	TSS.esp0 = (uintptr_t) &_bss_end;
+	TSS.esp0 = (uintptr_t) &_isr_stack_top;
 
 	GDT[SEG_TSS] = (struct gdt_entry) {
 		.limit_low  = sizeof(TSS),
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:
diff --git a/src/kernel/arch/i386/multiboot.s b/src/kernel/arch/i386/multiboot.s
index 62bc9fd..dc19b36 100644
--- a/src/kernel/arch/i386/multiboot.s
+++ b/src/kernel/arch/i386/multiboot.s
@@ -1,9 +1,7 @@
 .set MAGIC, 0x1BADB002
 
-/* 1<<0  - align modules on page boundaries.
-   1<<1  - fill the mem_ fields in multiboot_info
-   1<<16 - enable manual addressing */
-.set FLAGS,        1<<0 | 1<<16
+/* 1<<0  - align modules on page boundaries. */
+.set FLAGS,        1<<0
 .set CHECKSUM, -(MAGIC + FLAGS)
 
 .section .multiboot
@@ -12,8 +10,3 @@ multiboot_header:
 	.long MAGIC
 	.long FLAGS
 	.long CHECKSUM
-	.long multiboot_header // header_addr
-	.long multiboot_header // load_addr
-	.long _data_end        // load_end_addr
-	.long _bss_end         // bss_end_addr
-	.long _start           // entry_addr
diff --git a/src/kernel/arch/i386/sysenter.s b/src/kernel/arch/i386/sysenter.s
index ade69ec..70e9f13 100644
--- a/src/kernel/arch/i386/sysenter.s
+++ b/src/kernel/arch/i386/sysenter.s
@@ -8,26 +8,6 @@
 .set IA32_SYSENTER_EIP, 0x176
 
 .section .text
-.global _sysexit_real
-.type _sysexit_real, @function
-_sysexit_real:
-	mov $(SEG_r3data << 3 | 3), %ax
-	mov %ax, %ds
-	mov %ax, %es
-	mov %ax, %fs
-	mov %ax, %gs
-
-	// enable paging
-	mov %cr0, %eax
-	or $0x80000000, %eax
-	mov %eax, %cr0
-
-	// restore the registers
-	mov $_sysexit_regs, %esp
-	popal
-	sysexit
-
-
 .global sysenter_setup
 .type sysenter_setup, @function
 sysenter_setup:
@@ -38,7 +18,7 @@ sysenter_setup:
 	wrmsr
 
 	mov $IA32_SYSENTER_ESP, %ecx
-	mov $_bss_end, %eax
+	mov $0, %eax // unused
 	wrmsr
 
 	mov $IA32_SYSENTER_EIP, %ecx
@@ -47,6 +27,35 @@ sysenter_setup:
 
 	ret
 
+
+.section .text.early
+
+.global stored_eax
+stored_eax:
+.long 0
+
+.global _sysexit_real
+.type _sysexit_real, @function
+_sysexit_real:
+	mov $(SEG_r3data << 3 | 3), %ax
+	mov %ax, %ds
+	mov %ax, %es
+	mov %ax, %fs
+	mov %ax, %gs
+
+	// restore the registers
+	mov $_sysexit_regs, %esp
+	popal
+
+	// enable paging
+	mov %eax, stored_eax
+	mov %cr0, %eax
+	or $0x80000000, %eax
+	mov %eax, %cr0
+	mov stored_eax, %eax
+
+	sysexit
+
 sysenter_stage1:
 	cli /* prevent random IRQs in the middle of kernel code */