a sensible source structure

The idea is that src/kernel/ is only allowed to interface with the
hardware using whatever's defined in src/arch/generic.h. I'll probably
write a small script for checking this later on.

This is a giant commit so I've probably fucked something up. It boots
fine on Bochs and QEMU, so at least there's that.

23 files changed, 97 insertions, 88 deletions

diff --git a/src/arch/generic.h b/src/arch/generic.h
new file mode 100644
index 0000000..7807316
--- /dev/null
+++ b/src/arch/generic.h
@@ -0,0 +1,14 @@
+#pragma once
+
+// i have no idea where else to put it
+#define PAGE_SIZE 4096
+
+// src/arch/i386/boot.s
+extern void stack_top;
+
+__attribute__((noreturn))
+void halt_cpu();
+
+// src/arch/i386/sysenter.s
+void sysexit(void (*fun)(), void *stack_top);
+void sysenter_setup();
diff --git a/src/arch/i386/boot.c b/src/arch/i386/boot.c
new file mode 100644
index 0000000..b2b84f0
--- /dev/null
+++ b/src/arch/i386/boot.c
@@ -0,0 +1,16 @@
+#include <arch/i386/gdt.h>
+#include <arch/i386/interrupts/idt.h>
+#include <arch/i386/sysenter.h>
+#include <arch/i386/tty.h>
+#include <kernel/main.h>
+
+void kmain_early() {
+	tty_clear();
+	tty_const("gdt...");
+	gdt_init();
+	tty_const("idt...");
+	idt_init();
+	tty_const("sysenter...");
+	sysenter_setup();
+	kmain();
+}
diff --git a/src/arch/i386/boot.s b/src/arch/i386/boot.s
new file mode 100644
index 0000000..74ec312
--- /dev/null
+++ b/src/arch/i386/boot.s
@@ -0,0 +1,25 @@
+/* a lil stack TODO move to linker.ld */
+.section .bss
+.global stack_top
+.type stack_top, @object
+.align 16
+stack_bottom:
+.skip 16384
+stack_top:
+
+
+.section .text
+.global _start
+.type _start, @function
+_start:
+	mov $stack_top, %esp
+	call kmain_early
+
+.global halt_cpu
+.type halt_cpu, @function
+halt_cpu:
+	cli
+1:	hlt
+	jmp 1b
+
+.size _start, . - _start
diff --git a/src/kernel/gdt.h b/src/arch/i386/gdt.h
index 9e5a6a5..bcb9870 100644
--- a/src/kernel/gdt.h
+++ b/src/arch/i386/gdt.h
@@ -13,3 +13,4 @@ enum {
 };
 
 void gdt_init();
+void gdt_farjump(int segment);
diff --git a/src/arch/i386/gdt/farjump.s b/src/arch/i386/gdt/farjump.s
new file mode 100644
index 0000000..85d8ba5
--- /dev/null
+++ b/src/arch/i386/gdt/farjump.s
@@ -0,0 +1,9 @@
+.section .text
+.global gdt_farjump
+.type gdt_farjump, @function
+gdt_farjump:
+	/* retf pops off the return address and code segment off the stack.
+	 * it turns out that in the i386 cdecl calling convention they're in
+	 * the correct place already.
+	 */
+	retf
diff --git a/src/kernel/gdt.c b/src/arch/i386/gdt/gdt.c
index b0d6320..3e0647b 100644
--- a/src/kernel/gdt.c
+++ b/src/arch/i386/gdt/gdt.c
@@ -1,8 +1,8 @@
-#include <kernel/gdt.h>
+#include <arch/generic.h>
+#include <arch/i386/gdt.h>
 #include <kernel/util.h>
 #include <stdint.h>
 
-extern void stack_top; // platform/boot.s
 
 struct gdt_entry {
 	uint64_t limit_low  : 16;
@@ -95,8 +95,6 @@ static void gdt_prepare() {
 	GDT[SEG_TSS].base_high  = (((uint32_t) &TSS) >> 24) & 0xff;
 }
 
-void change_cs(int seg); // temporary
-
 static void gdt_load() {
 	lgdt_arg.limit = sizeof(GDT) - 1;
 	lgdt_arg.base = (uint32_t) &GDT;
@@ -106,7 +104,7 @@ static void gdt_load() {
 	    : : "a" (SEG_TSS << 3 | 3) : "memory");
 
 	// update all segment registers
-	change_cs(SEG_r0code << 3);
+	gdt_farjump(SEG_r0code << 3);
 	asm("mov %0, %%ds;"
 	    "mov %0, %%ss;"
 	    "mov %0, %%es;"
diff --git a/src/kernel/idt.c b/src/arch/i386/interrupts/idt.c
index 65f511f..4e23118 100644
--- a/src/kernel/idt.c
+++ b/src/arch/i386/interrupts/idt.c
@@ -1,6 +1,6 @@
-#include <kernel/gdt.h>
-#include <kernel/idt.h>
-#include <kernel/isr.h>
+#include <arch/i386/gdt.h>
+#include <arch/i386/interrupts/idt.h>
+#include <arch/i386/interrupts/isr.h>
 #include <kernel/panic.h>
 #include <stdbool.h>
 #include <stdint.h>
diff --git a/src/kernel/idt.h b/src/arch/i386/interrupts/idt.h
index 5627657..5627657 100644
--- a/src/kernel/idt.h
+++ b/src/arch/i386/interrupts/idt.h
diff --git a/src/kernel/isr.c b/src/arch/i386/interrupts/isr.c
index b715de0..03399ea 100644
--- a/src/kernel/isr.c
+++ b/src/arch/i386/interrupts/isr.c
@@ -1,6 +1,6 @@
-#include <kernel/isr.h>
+#include <arch/i386/interrupts/isr.h>
+#include <arch/i386/tty.h>
 #include <kernel/panic.h>
-#include <kernel/tty.h>
 #include <stdbool.h>
 #include <stdint.h>
 
diff --git a/src/kernel/isr.h b/src/arch/i386/interrupts/isr.h
index 150fc46..150fc46 100644
--- a/src/kernel/isr.h
+++ b/src/arch/i386/interrupts/isr.h
diff --git a/src/arch/i386/multiboot.s b/src/arch/i386/multiboot.s
new file mode 100644
index 0000000..2194982
--- /dev/null
+++ b/src/arch/i386/multiboot.s
@@ -0,0 +1,11 @@
+.set MAGIC, 0x1BADB002
+.set FLAG_ALIGN,   1<<0 /* align modules on page boundaries */
+.set FLAG_MEMINFO, 1<<1 /* memory map */
+.set FLAGS,        FLAG_ALIGN | FLAG_MEMINFO
+.set CHECKSUM, -(MAGIC + FLAGS)
+
+.section .multiboot
+.align 4
+.long MAGIC
+.long FLAGS
+.long CHECKSUM
diff --git a/src/arch/i386/sysenter.h b/src/arch/i386/sysenter.h
new file mode 100644
index 0000000..b531fe8
--- /dev/null
+++ b/src/arch/i386/sysenter.h
@@ -0,0 +1,2 @@
+#pragma once
+void sysenter_setup();
diff --git a/src/platform/sysenter.s b/src/arch/i386/sysenter.s
index 270dc08..666c0f0 100644
--- a/src/platform/sysenter.s
+++ b/src/arch/i386/sysenter.s
@@ -1,4 +1,4 @@
-/* kernel/gdt.c */
+/* arch/i386/gdt.c */
 .set SEG_r0code, 1
 .set SEG_r3code, 3
 .set SEG_r3data, 4
diff --git a/src/kernel/tty.c b/src/arch/i386/tty.c
index 5c4c47d..a7c74f5 100644
--- a/src/kernel/tty.c
+++ b/src/arch/i386/tty.c
@@ -1,6 +1,4 @@
-/* will be moved to userspace later on */
-
-#include <kernel/tty.h>
+#include <arch/i386/tty.h>
 
 struct vga_cell {
 	unsigned char c;
diff --git a/src/kernel/tty.h b/src/arch/i386/tty.h
index 3dc1525..3dc1525 100644
--- a/src/kernel/tty.h
+++ b/src/arch/i386/tty.h
diff --git a/src/kernel/main.c b/src/kernel/main.c
index 0193514..aa67d7c 100644
--- a/src/kernel/main.c
+++ b/src/kernel/main.c
@@ -1,22 +1,11 @@
-#include <kernel/gdt.h>
-#include <kernel/idt.h>
+#include <arch/generic.h>
 #include <kernel/mem.h>
 #include <kernel/panic.h>
 #include <kernel/proc.h>
-#include <kernel/tty.h>
-#include <platform/asm.h>
 
 void r3_test();
 
-void kmain()
-{
-	tty_clear();
-	tty_const("gdt...");
-	gdt_init();
-	tty_const("idt...");
-	idt_init();
-	tty_const("sysenter...");
-	sysenter_setup();
+void kmain() {
 	tty_const("mem...");
 	mem_init();
 
diff --git a/src/kernel/main.h b/src/kernel/main.h
new file mode 100644
index 0000000..6f27386
--- /dev/null
+++ b/src/kernel/main.h
@@ -0,0 +1,3 @@
+#pragma once
+
+void kmain();
diff --git a/src/kernel/mem.c b/src/kernel/mem.c
index 08eb285..f383e8b 100644
--- a/src/kernel/mem.c
+++ b/src/kernel/mem.c
@@ -1,3 +1,4 @@
+#include <arch/generic.h>
 #include <kernel/mem.h>
 
 extern void *_kernel_end;
diff --git a/src/kernel/mem.h b/src/kernel/mem.h
index e8e6a4f..efa65d6 100644
--- a/src/kernel/mem.h
+++ b/src/kernel/mem.h
@@ -1,8 +1,6 @@
 #pragma once
 #include <stddef.h>
 
-#define PAGE_SIZE 4096
-
 void mem_init();
 
 // allocates `pages` consecutive pages
diff --git a/src/kernel/panic.h b/src/kernel/panic.h
index 7d2ea5f..54a0b8b 100644
--- a/src/kernel/panic.h
+++ b/src/kernel/panic.h
@@ -1,6 +1,6 @@
 #pragma once
-#include <kernel/tty.h>
-#include <platform/asm.h>
+#include <arch/generic.h>
+#include <arch/i386/tty.h> // TODO abstract away
 
 // dumb c shit
 #define panic_tostr2(x) #x
diff --git a/src/kernel/proc.c b/src/kernel/proc.c
index 776238c..7d42bce 100644
--- a/src/kernel/proc.c
+++ b/src/kernel/proc.c
@@ -1,6 +1,6 @@
+#include <arch/generic.h>
 #include <kernel/mem.h>
 #include <kernel/proc.h>
-#include <platform/asm.h>
 
 struct process *process_current;
 
diff --git a/src/platform/asm.h b/src/platform/asm.h
deleted file mode 100644
index 6f72617..0000000
--- a/src/platform/asm.h
+++ /dev/null
@@ -1,9 +0,0 @@
-#pragma once
-
-// boot.s
-__attribute__((noreturn))
-void halt_cpu();
-
-// sysenter.c
-void sysexit(void (*fun)(), void *stack_top);
-void sysenter_setup();
diff --git a/src/platform/boot.s b/src/platform/boot.s
deleted file mode 100644
index d5bfda5..0000000
--- a/src/platform/boot.s
+++ /dev/null
@@ -1,47 +0,0 @@
-.set MAGIC, 0x1BADB002
-.set FLAG_ALIGN,   1<<0 /* align modules on page boundaries */
-.set FLAG_MEMINFO, 1<<1 /* memory map */
-.set FLAGS,        FLAG_ALIGN | FLAG_MEMINFO
-.set CHECKSUM, -(MAGIC + FLAGS)
-
-.section .multiboot
-.align 4
-.long MAGIC
-.long FLAGS
-.long CHECKSUM
-
-/* a lil stack */
-.section .bss
-.global stack_top
-.type stack_top, @object
-.align 16
-stack_bottom:
-.skip 16384
-stack_top:
-
-
-.section .text
-.global _start
-.type _start, @function
-_start:
-	mov $stack_top, %esp
-	call kmain
-
-.global halt_cpu
-.type halt_cpu, @function
-halt_cpu:
-	cli
-1:	hlt
-	jmp 1b
-
-// temporary, will be moved to another file soon
-.global change_cs
-.type change_cs, @function
-change_cs:
-	/* retf pops off the return address and code segment off the stack.
-	 * it turns out that in the i386 cdecl calling convention they're in
-	 * the correct place already.
-	 */
-	retf
-
-.size _start, . - _start