amd64: barely boot into kernel code

1 files changed, 86 insertions, 0 deletions

diff --git a/src/kernel/arch/amd64/32/boot.s b/src/kernel/arch/amd64/32/boot.s
new file mode 100644
index 0000000..eb33c28
--- /dev/null
+++ b/src/kernel/arch/amd64/32/boot.s
@@ -0,0 +1,86 @@
+.section .text
+.global _start
+.type _start, @function
+_start:
+	mov $_stack_top, %esp
+	push %ebx // save the address of the multiboot struct
+
+	mov $0x80000000, %eax // check CPUID extended functions
+	cpuid
+	cmp $0x80000001, %eax
+	jb panic_early
+
+	mov $0x80000001, %eax
+	cpuid
+	test $(1<<29), %edx // check long mode support
+	jz panic_early
+
+	mov %cr4, %eax
+	or $(1<<5), %eax // PAE
+	mov %eax, %cr4
+
+	call pml4_identity_init
+	mov $pml4_identity, %eax
+	mov %eax, %cr3
+
+	mov $0xC0000080, %ecx // EFER MSR
+	rdmsr
+	or $(1 | 1<<8 | 1<<11), %eax // sysenter | long mode | NX
+	wrmsr
+
+	mov %cr0, %eax
+	or $0x80000000, %eax
+	mov %eax, %cr0
+
+	call gdt_init
+	lgdt (lgdt_arg)
+
+	pop %edi
+
+	// TODO import gdt.h for globals
+	mov $(2<<3), %eax
+	mov %eax, %ds // SEG_r0data
+	mov %eax, %ss
+	mov %eax, %es
+	mov %eax, %fs
+	mov %eax, %gs
+
+	ljmp $(1<<3), $boot64 // SEG_r0code
+
+panic_early:
+	// output a vga Fuck
+	movl $0x4F754F46, 0xB872A
+	movl $0x4F6B4F63, 0xB872E
+	jmp cpu_halt
+
+// TODO not part of anything yet
+	call sysenter_setup
+	// TODO will fail
+	push %ebx // address of the Multiboot struct
+	call kmain_early
+
+.global cpu_shutdown
+.type cpu_shutdown, @function
+cpu_shutdown:
+/* This quits QEMU. While I couldn't find this officially documented anywhere,
+ * it is used by QEMU in tests/tcg/i386/system/boot.S (as of commit 40d6ee), so
+ * I assume that this is safe-ish to use */
+	mov $0x604, %edx
+	mov $0x2000, %eax
+	outw %ax, %dx
+
+.global cpu_halt
+.type cpu_halt, @function
+cpu_halt:
+	cli
+1:	hlt
+	jmp 1b
+
+
+.global cpu_pause
+.type cpu_pause, @function
+cpu_pause:
+	sti
+	hlt
+	cli
+	ret