[amd64] Add initrd loading support

include/sys/amd64/loader/util.h

@@ -6,6 +6,7 @@
 void *memset(void *blk, int v, size_t sz);
 void *memcpy(void *dst, const void *src, size_t sz);
 int strcmp(const char *a, const char *b);
+int strncmp(const char *a, const char *b, size_t lim);
 
 // Debug utils
 void panic(const char *s);

sys/amd64/conf.mk

@@ -56,7 +56,8 @@ kernel_CFLAGS=-ffreestanding \
 DIRS+=$(O)/sys/amd64/mm \
 	  $(O)/sys/amd64/hw \
 	  $(O)/sys/amd64/acpi \
-	  $(O)/sys/amd64/sys
+	  $(O)/sys/amd64/sys \
+	  $(O)/sys/amd64/image/boot/grub
 # add .inc includes for asm
 HEADERS+=$(shell find include -name "*.inc")
 
@@ -73,7 +74,7 @@ $(O)/sys/%.o: sys/%.c $(HEADERS)
 	@$(CC64) $(kernel_CFLAGS) -c -o $@ $<
 
 ### Kernel loader build
-TARGETS+=$(O)/sys/amd64/loader.elf $(O)/sys/amd64/kernel.elf
+TARGETS+=$(O)/sys/amd64/image.iso
 DIRS+=$(O)/sys/amd64/loader
 loader_OBJS+=$(O)/sys/amd64/loader/boot.o \
 			 $(O)/sys/amd64/loader/loader.o \
@@ -109,7 +110,14 @@ QEMU_OPTS?=-nographic \
 		   -serial mon:stdio \
 		   -m 512
 
+$(O)/sys/amd64/image.iso: $(O)/sys/amd64/kernel.elf $(O)/sys/amd64/loader.elf sys/amd64/grub.cfg
+	@printf " ISO\t%s\n" $(@:$(O)/%=%)
+	@cp sys/amd64/grub.cfg $(O)/sys/amd64/image/boot/grub/grub.cfg
+	@cp $(O)/sys/amd64/kernel.elf $(O)/sys/amd64/image/boot/kernel
+	@cp $(O)/sys/amd64/loader.elf $(O)/sys/amd64/image/boot/loader
+	@grub-mkrescue -o $(O)/sys/amd64/image.iso $(O)/sys/amd64/image 2>/dev/null
+
 qemu: all
 	@$(QEMU_BIN) \
-		-kernel $(O)/sys/amd64/loader.elf \
-		-initrd $(O)/sys/amd64/kernel.elf $(QEMU_OPTS)
+		-cdrom $(O)/sys/amd64/image.iso \
+		$(QEMU_OPTS)

sys/amd64/grub.cfg

@@ -0,0 +1,5 @@
+menuentry "yggdrasil" {
+    multiboot /boot/loader
+    module /boot/kernel kernel
+    module /boot/test-mod.img initrd
+}

sys/amd64/loader/loader.c

@@ -91,9 +91,37 @@ void loader_main(uint32_t magic, struct multiboot_info *mb_info) {
     loader_data.multiboot_info_ptr = (uintptr_t) mb_info;
 
     struct multiboot_mod_list *mod_list = (struct multiboot_mod_list *) (uintptr_t) mb_info->mods_addr;
+    const char *kernel_cmdline = NULL;
+    uintptr_t kernel_mod = 0;
+    uintptr_t initrd_mod = 0;
 
-    if (mb_info->mods_count != 1) {
-        panic("Expected 1 module");
+    if (mb_info->mods_count == 1) {
+        // Only kernel is provided, ignore cmdline
+        kernel_mod = mod_list[0].mod_start;
+    } else if (mb_info->mods_count == 2) {
+        // initrd and kernel provided
+        // Find out which is which
+
+        for (size_t i = 0; i < mb_info->mods_count; ++i) {
+            if (!strncmp((const char *) (uintptr_t) mod_list[i].cmdline, "kernel", 6)) {
+                if (kernel_mod) {
+                    panic("Two \"kernel\"s provided!");
+                }
+                kernel_mod = mod_list[i].mod_start;
+                kernel_cmdline = (const char *) (uintptr_t) mod_list[i].cmdline;
+            } else {
+                if (initrd_mod) {
+                    panic("Two \"initrd\"s provided!");
+                }
+                initrd_mod = mod_list[i].mod_start;
+            }
+        }
+    } else {
+        panic("More than two modules provided");
+    }
+
+    if (!kernel_mod) {
+        panic("No kernel to load");
     }
 
     // Calculate boundaries so we don't overwrite something accidentally
@@ -103,6 +131,11 @@ void loader_main(uint32_t magic, struct multiboot_info *mb_info) {
         }
     }
 
+    if (kernel_cmdline) {
+        puts("Kernel cmdline: ");
+        puts(kernel_cmdline);
+        putc('\n');
+    }
     puts("Modules end addr: ");
     putx(modules_end);
     putc('\n');

sys/amd64/loader/util.c

@@ -23,6 +23,16 @@ int strcmp(const char *a, const char *b) {
     return *a != *b;
 }
 
+int strncmp(const char *a, const char *b, size_t n) {
+    size_t c = 0;
+    for (; c < n && (*a || *b); ++c, ++a, ++b) {
+        if (*a != *b) {
+            return -1;
+        }
+    }
+    return 0;
+}
+
 static inline void outb(uint16_t addr, uint8_t v) {
     asm volatile("outb %0, %1"::"a"(v), "Nd"(addr));
 }
@@ -74,6 +84,7 @@ void putx(uint64_t v) {
 
 void panic(const char *s) {
     memset((void *) 0xB8000, 0, 80 * 25 * 2);
+    puts(s);
 
     for (size_t i = 0; *s; ++i, ++s) {
         ((uint16_t *) 0xB8000)[i] = *s | 0x700;