diff options
| -rw-r--r-- | Makefile | 24 | ||||
| -rw-r--r-- | multiboot.S | 75 |
2 files changed, 97 insertions, 2 deletions
@@ -82,6 +82,11 @@ xv6.img: bootblock kernel fs.img dd if=bootblock of=xv6.img conv=notrunc dd if=kernel of=xv6.img seek=1 conv=notrunc +xv6memfs.img: bootblock kernelmemfs + dd if=/dev/zero of=xv6memfs.img count=10000 + dd if=bootblock of=xv6memfs.img conv=notrunc + dd if=kernelmemfs of=xv6memfs.img seek=1 conv=notrunc + bootblock: bootasm.S bootmain.c $(CC) $(CFLAGS) -fno-pic -O -nostdinc -I. -c bootmain.c $(CC) $(CFLAGS) -fno-pic -nostdinc -I. -c bootasm.S @@ -102,11 +107,23 @@ initcode: initcode.S $(OBJCOPY) -S -O binary initcode.out initcode $(OBJDUMP) -S initcode.o > initcode.asm -kernel: $(OBJS) bootother initcode - $(LD) $(LDFLAGS) -Ttext 0x100000 -e main -o kernel $(OBJS) -b binary initcode bootother +kernel: $(OBJS) multiboot.o bootother initcode + $(LD) $(LDFLAGS) -Ttext 0x100000 -e main -o kernel multiboot.o $(OBJS) -b binary initcode bootother fs.img $(OBJDUMP) -S kernel > kernel.asm $(OBJDUMP) -t kernel | sed '1,/SYMBOL TABLE/d; s/ .* / /; /^$$/d' > kernel.sym +# kernelmemfs is a copy of kernel that maintains the +# disk image in memory instead of writing to a disk. +# This is not so useful for testing persistent storage or +# exploring disk buffering implementations, but it is +# great for testing the kernel on real hardware without +# needing a scratch disk. +MEMFSOBJS = $(filter-out ide.o,$(OBJS)) memide.o +kernelmemfs: $(MEMFSOBJS) multiboot.o bootother initcode fs.img + $(LD) $(LDFLAGS) -Ttext 0x100000 -e main -o kernelmemfs multiboot.o $(MEMFSOBJS) -b binary initcode bootother fs.img + $(OBJDUMP) -S kernelmemfs > kernelmemfs.asm + $(OBJDUMP) -t kernelmemfs | sed '1,/SYMBOL TABLE/d; s/ .* / /; /^$$/d' > kernelmemfs.sym + tags: $(OBJS) bootother.S _init etags *.S *.c @@ -187,6 +204,9 @@ QEMUOPTS = -hdb fs.img xv6.img -smp $(CPUS) qemu: fs.img xv6.img $(QEMU) -serial mon:stdio $(QEMUOPTS) +qemu-memfs: xv6memfs.img + $(QEMU) xv6memfs.img -smp $(CPUS) + qemu-nox: fs.img xv6.img $(QEMU) -nographic $(QEMUOPTS) diff --git a/multiboot.S b/multiboot.S new file mode 100644 index 0000000..2579b6d --- /dev/null +++ b/multiboot.S @@ -0,0 +1,75 @@ +# Multiboot header, for multiboot boot loaders like GNU Grub. +# http://www.gnu.org/software/grub/manual/multiboot/multiboot.html +# +# Using GRUB 2, you can boot xv6 from a file stored in a +# Linux file system by copying kernel or kernelmemfs to /boot +# and then adding this menu entry: +# +# menuentry "xv6" { +# insmod ext2 +# set root='(hd0,msdos1)' +# set kernel='/boot/kernel' +# echo "Loading ${kernel}..." +# multiboot ${kernel} ${kernel} +# boot +# } + +#include "asm.h" + +#define STACK 4096 + +#define SEG_KCODE 1 // kernel code +#define SEG_KDATA 2 // kernel data+stack + +# Multiboot header. Data to direct multiboot loader. +.p2align 2 +.text +.globl multiboot_header +multiboot_header: + #define magic 0x1badb002 + #define flags (1<<16 | 1<<0) + .long magic + .long flags + .long (-magic-flags) + .long multiboot_header # beginning of image + .long multiboot_header + .long edata + .long end + .long multiboot_entry + +# Multiboot entry point. Machine is mostly set up. +# Configure the GDT to match the environment that our usual +# boot loader - bootasm.S - sets up. +.globl multiboot_entry +multiboot_entry: + lgdt gdtdesc + ljmp $(SEG_KCODE<<3), $mbstart32 + +mbstart32: + # Set up the protected-mode data segment registers + movw $(SEG_KDATA<<3), %ax # Our data segment selector + movw %ax, %ds # -> DS: Data Segment + movw %ax, %es # -> ES: Extra Segment + movw %ax, %ss # -> SS: Stack Segment + movw $0, %ax # Zero segments not ready for use + movw %ax, %fs # -> FS + movw %ax, %gs # -> GS + + # Set up the stack pointer and call into C. + movl $(stack + STACK), %esp + call main +spin: + jmp spin + +# Bootstrap GDT +.p2align 2 # force 4 byte alignment +gdt: + SEG_NULLASM # null seg + SEG_ASM(STA_X|STA_R, 0x0, 0xffffffff) # code seg + SEG_ASM(STA_W, 0x0, 0xffffffff) # data seg + +gdtdesc: + .word (gdtdesc - gdt - 1) # sizeof(gdt) - 1 + .long gdt # address gdt + +.comm stack, STACK |