multiboot support and memory-only (no disk) kernel
This commit is contained in:
Russ Cox
parent
af6a6a4775
commit
89bfdd4db1
2 changed files with 97 additions and 2 deletions
24
Makefile
24
Makefile
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@ -82,6 +82,11 @@ xv6.img: bootblock kernel fs.img
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dd if=bootblock of=xv6.img conv=notrunc
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dd if=kernel of=xv6.img seek=1 conv=notrunc
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xv6memfs.img: bootblock kernelmemfs
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dd if=/dev/zero of=xv6memfs.img count=10000
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dd if=bootblock of=xv6memfs.img conv=notrunc
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dd if=kernelmemfs of=xv6memfs.img seek=1 conv=notrunc
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bootblock: bootasm.S bootmain.c
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$(CC) $(CFLAGS) -fno-pic -O -nostdinc -I. -c bootmain.c
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$(CC) $(CFLAGS) -fno-pic -nostdinc -I. -c bootasm.S
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@ -102,11 +107,23 @@ initcode: initcode.S
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$(OBJCOPY) -S -O binary initcode.out initcode
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$(OBJDUMP) -S initcode.o > initcode.asm
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kernel: $(OBJS) bootother initcode
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$(LD) $(LDFLAGS) -Ttext 0x100000 -e main -o kernel $(OBJS) -b binary initcode bootother
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kernel: $(OBJS) multiboot.o bootother initcode
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$(LD) $(LDFLAGS) -Ttext 0x100000 -e main -o kernel multiboot.o $(OBJS) -b binary initcode bootother fs.img
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$(OBJDUMP) -S kernel > kernel.asm
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$(OBJDUMP) -t kernel | sed '1,/SYMBOL TABLE/d; s/ .* / /; /^$$/d' > kernel.sym
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# kernelmemfs is a copy of kernel that maintains the
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# disk image in memory instead of writing to a disk.
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# This is not so useful for testing persistent storage or
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# exploring disk buffering implementations, but it is
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# great for testing the kernel on real hardware without
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# needing a scratch disk.
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MEMFSOBJS = $(filter-out ide.o,$(OBJS)) memide.o
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kernelmemfs: $(MEMFSOBJS) multiboot.o bootother initcode fs.img
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$(LD) $(LDFLAGS) -Ttext 0x100000 -e main -o kernelmemfs multiboot.o $(MEMFSOBJS) -b binary initcode bootother fs.img
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$(OBJDUMP) -S kernelmemfs > kernelmemfs.asm
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$(OBJDUMP) -t kernelmemfs | sed '1,/SYMBOL TABLE/d; s/ .* / /; /^$$/d' > kernelmemfs.sym
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tags: $(OBJS) bootother.S _init
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etags *.S *.c
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@ -187,6 +204,9 @@ QEMUOPTS = -hdb fs.img xv6.img -smp $(CPUS)
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qemu: fs.img xv6.img
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$(QEMU) -serial mon:stdio $(QEMUOPTS)
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qemu-memfs: xv6memfs.img
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$(QEMU) xv6memfs.img -smp $(CPUS)
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qemu-nox: fs.img xv6.img
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$(QEMU) -nographic $(QEMUOPTS)
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75
multiboot.S
Normal file
75
multiboot.S
Normal file
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@ -0,0 +1,75 @@
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# Multiboot header, for multiboot boot loaders like GNU Grub.
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# http://www.gnu.org/software/grub/manual/multiboot/multiboot.html
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#
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# Using GRUB 2, you can boot xv6 from a file stored in a
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# Linux file system by copying kernel or kernelmemfs to /boot
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# and then adding this menu entry:
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#
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# menuentry "xv6" {
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# insmod ext2
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# set root='(hd0,msdos1)'
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# set kernel='/boot/kernel'
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# echo "Loading ${kernel}..."
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# multiboot ${kernel} ${kernel}
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# boot
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# }
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#include "asm.h"
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#define STACK 4096
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#define SEG_KCODE 1 // kernel code
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#define SEG_KDATA 2 // kernel data+stack
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# Multiboot header. Data to direct multiboot loader.
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.p2align 2
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.text
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.globl multiboot_header
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multiboot_header:
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#define magic 0x1badb002
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#define flags (1<<16 | 1<<0)
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.long magic
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.long flags
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.long (-magic-flags)
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.long multiboot_header # beginning of image
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.long multiboot_header
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.long edata
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.long end
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.long multiboot_entry
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# Multiboot entry point. Machine is mostly set up.
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# Configure the GDT to match the environment that our usual
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# boot loader - bootasm.S - sets up.
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.globl multiboot_entry
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multiboot_entry:
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lgdt gdtdesc
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ljmp $(SEG_KCODE<<3), $mbstart32
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mbstart32:
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# Set up the protected-mode data segment registers
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movw $(SEG_KDATA<<3), %ax # Our data segment selector
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movw %ax, %ds # -> DS: Data Segment
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movw %ax, %es # -> ES: Extra Segment
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movw %ax, %ss # -> SS: Stack Segment
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movw $0, %ax # Zero segments not ready for use
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movw %ax, %fs # -> FS
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movw %ax, %gs # -> GS
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# Set up the stack pointer and call into C.
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movl $(stack + STACK), %esp
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call main
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spin:
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jmp spin
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# Bootstrap GDT
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.p2align 2 # force 4 byte alignment
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gdt:
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SEG_NULLASM # null seg
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SEG_ASM(STA_X|STA_R, 0x0, 0xffffffff) # code seg
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SEG_ASM(STA_W, 0x0, 0xffffffff) # data seg
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gdtdesc:
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.word (gdtdesc - gdt - 1) # sizeof(gdt) - 1
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.long gdt # address gdt
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.comm stack, STACK
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