basic boot module support

This loads a file from the boot disk into memory. Currently it just gets
printed, but it's going to become a real executable soon.

8 files changed, 69 insertions, 5 deletions

diff --git a/Makefile b/Makefile
index 666c226..4b9ab02 100644
--- a/Makefile
+++ b/Makefile
@@ -9,13 +9,17 @@ QFLAGS  = -no-reboot -d guest_errors,int,pcall,cpu_reset
 OBJ  = $(patsubst src/%.s,out/obj/%.s.o,$(shell find src/ -type f -name '*.s'))
 OBJ += $(patsubst src/%.c,out/obj/%.c.o,$(shell find src/ -type f -name '*.c'))
 
-out/boot.iso: out/fs/boot/kernel.bin out/fs/boot/grub/grub.cfg
+out/boot.iso: out/fs/boot/kernel.bin out/fs/boot/grub/grub.cfg out/fs/boot/init
 	grub-mkrescue -o $@ out/fs/
 
 out/fs/boot/grub/grub.cfg: grub.cfg
 	@mkdir -p $(@D)
 	cp $< $@
 
+out/fs/boot/init: src/test_module
+	@mkdir -p $(@D)
+	cp $< $@
+
 out/fs/boot/kernel.bin: $(OBJ)
 	@mkdir -p $(@D)
 	$(CC) $(LFLAGS) -T linker.ld $^ -o $@
diff --git a/grub.cfg b/grub.cfg
index 5f66c18..36f116d 100644
--- a/grub.cfg
+++ b/grub.cfg
@@ -2,4 +2,5 @@ set timeout=0
 
 menuentry "Camellia" {
 	multiboot /boot/kernel.bin
+	module /boot/init
 }
diff --git a/src/arch/i386/boot.c b/src/arch/i386/boot.c
index 37e1aff..242d070 100644
--- a/src/arch/i386/boot.c
+++ b/src/arch/i386/boot.c
@@ -1,11 +1,16 @@
 #include <arch/generic.h>
 #include <arch/i386/gdt.h>
 #include <arch/i386/interrupts/idt.h>
+#include <arch/i386/multiboot.h>
 #include <arch/i386/sysenter.h>
 #include <arch/i386/tty.h>
 #include <kernel/main.h>
+#include <kernel/panic.h>
 
-void kmain_early() {
+void kmain_early(struct multiboot_info *multiboot) {
+	struct kmain_info info;
+
+	// setup some basic stuff
 	tty_clear();
 	log_const("gdt...");
 	gdt_init();
@@ -13,5 +18,16 @@ void kmain_early() {
 	idt_init();
 	log_const("sysenter...");
 	sysenter_setup();
-	kmain();
+	
+	{ // find the init module
+		struct multiboot_mod *module = &multiboot->mods[0];
+		if (multiboot->mods_count < 1) {
+			log_const("can't find init! ");
+			panic();
+		}
+		info.init.at   = module->start;
+		info.init.size = module->end - module->start;
+	}
+	
+	kmain(info);
 }
diff --git a/src/arch/i386/boot.s b/src/arch/i386/boot.s
index 2578e87..74de9b7 100644
--- a/src/arch/i386/boot.s
+++ b/src/arch/i386/boot.s
@@ -3,6 +3,7 @@
 .type _start, @function
 _start:
 	mov $stack_top, %esp
+	push %ebx // address of the Multiboot struct
 	call kmain_early
 
 .global halt_cpu
diff --git a/src/arch/i386/multiboot.h b/src/arch/i386/multiboot.h
new file mode 100644
index 0000000..f030247
--- /dev/null
+++ b/src/arch/i386/multiboot.h
@@ -0,0 +1,31 @@
+#pragma once
+#include <stdint.h>
+
+// TODO assert that pointers have 4 bytes.
+
+struct multiboot_mod {
+	void *start;
+	void *end;
+	const char *str;
+	uint32_t _reserved;
+} __attribute__((packed));
+
+struct multiboot_info {
+	uint32_t flag_mem         : 1;
+	uint32_t flag_boot_device : 1;
+	uint32_t flag_cmdline     : 1;
+	uint32_t flag_mods        : 1;
+	uint32_t _flag_other      : 28; // unimplemented
+	
+	uint32_t mem_lower;
+	uint32_t mem_upper;
+
+	uint32_t boot_device;
+
+	const char *cmdline;
+
+	uint32_t mods_count;
+	struct multiboot_mod *mods;
+
+	// [...]
+} __attribute__((packed));
diff --git a/src/kernel/main.c b/src/kernel/main.c
index d2d7dda..d2f2e7f 100644
--- a/src/kernel/main.c
+++ b/src/kernel/main.c
@@ -1,11 +1,13 @@
 #include <arch/generic.h>
+#include <kernel/main.h>
 #include <kernel/mem.h>
 #include <kernel/panic.h>
 #include <kernel/proc.h>
 
 void r3_test();
 
-void kmain() {
+void kmain(struct kmain_info info) {
+	log_write(info.init.at, info.init.size);
 	log_const("mem...");
 	mem_init();
 
diff --git a/src/kernel/main.h b/src/kernel/main.h
index 6f27386..f7f5f04 100644
--- a/src/kernel/main.h
+++ b/src/kernel/main.h
@@ -1,3 +1,11 @@
 #pragma once
+#include <stddef.h>
 
-void kmain();
+struct kmain_info {
+	struct {
+		void *at;    // page aligned
+		size_t size;
+	} init; // a boot module loaded by GRUB, containing the initrd driver
+};
+
+void kmain(struct kmain_info);
diff --git a/src/test_module b/src/test_module
new file mode 100644
index 0000000..4e809fd
--- /dev/null
+++ b/src/test_module
@@ -0,0 +1 @@
+[init binary goes here]