Checkpoint port of xv6 to x86-64. Passed usertests on 2 processors a few times.
The x86-64 doesn't just add two levels to page tables to support 64 bit addresses, but is a different processor. For example, calling conventions, system calls, and segmentation are different from 32-bit x86. Segmentation is basically gone, but gs/fs in combination with MSRs can be used to hold a per-core pointer. In general, x86-64 is more straightforward than 32-bit x86. The port uses code from sv6 and the xv6 "rsc-amd64" branch. A summary of the changes is as follows: - Booting: switch to grub instead of xv6's bootloader (pass -kernel to qemu), because xv6's boot loader doesn't understand 64bit ELF files. And, we don't care anymore about booting. - Makefile: use -m64 instead of -m32 flag for gcc, delete boot loader, xv6.img, bochs, and memfs. For now dont' use -O2, since usertests with -O2 is bigger than MAXFILE! - Update gdb.tmpl to be for i386 or x86-64 - Console/printf: use stdarg.h and treat 64-bit addresses different from ints (32-bit) - Update elfhdr to be 64 bit - entry.S/entryother.S: add code to switch to 64-bit mode: build a simple page table in 32-bit mode before switching to 64-bit mode, share code for entering boot processor and APs, and tweak boot gdt. The boot gdt is the gdt that the kernel proper also uses. (In 64-bit mode, the gdt/segmentation and task state mostly disappear.) - exec.c: fix passing argv (64-bit now instead of 32-bit). - initcode.c: use syscall instead of int. - kernel.ld: load kernel very high, in top terabyte. 64 bits is a lot of address space! - proc.c: initial return is through new syscall path instead of trapret. - proc.h: update struct cpu to have some scratch space since syscall saves less state than int, update struct context to reflect x86-64 calling conventions. - swtch: simplify for x86-64 calling conventions. - syscall: add fetcharg to handle x86-64 calling convetions (6 arguments are passed through registers), and fetchaddr to read a 64-bit value from user space. - sysfile: update to handle pointers from user space (e.g., sys_exec), which are 64 bits. - trap.c: no special trap vector for sys calls, because x86-64 has a different plan for system calls. - trapasm: one plan for syscalls and one plan for traps (interrupt and exceptions). On x86-64, the kernel is responsible for switching user/kernel stacks. To do, xv6 keeps some scratch space in the cpu structure, and uses MSR GS_KERN_BASE to point to the core's cpu structure (using swapgs). - types.h: add uint64, and change pde_t to uint64 - usertests: exit() when fork fails, which helped in tracking down one of the bugs in the switch from 32-bit to 64-bit - vectors: update to make them 64 bits - vm.c: use bootgdt in kernel too, program MSRs for syscalls and core-local state (for swapgs), walk 4 levels in walkpgdir, add DEVSPACETOP, use task segment to set kernel stack for interrupts (but simpler than in 32-bit mode), add an extra argument to freevm (size of user part of address space) to avoid checking all entries till KERNBASE (there are MANY TB before the top 1TB). - x86: update trapframe to have 64-bit entries, which is what the processor pushes on syscalls and traps. simplify lgdt and lidt, using struct desctr, which needs the gcc directives packed and aligned. TODO: - use int32 instead of int? - simplify curproc(). xv6 has per-cpu state again, but this time it must have it. - avoid repetition in walkpgdir - fix validateint() in usertests.c - fix bugs (e.g., observed one a case of entering kernel with invalid gs or proc
This commit is contained in:
Frans Kaashoek
parent
b818915f79
commit
ab0db651af
39 changed files with 1039 additions and 762 deletions
79
Makefile
79
Makefile
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@ -51,7 +51,7 @@ TOOLPREFIX := $(shell if i386-jos-elf-objdump -i 2>&1 | grep '^elf32-i386$$' >/d
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endif
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# If the makefile can't find QEMU, specify its path here
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# QEMU = qemu-system-i386
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QEMU = qemu-system-x86_64
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# Try to infer the correct QEMU
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ifndef QEMU
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@ -76,11 +76,16 @@ AS = $(TOOLPREFIX)gas
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LD = $(TOOLPREFIX)ld
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OBJCOPY = $(TOOLPREFIX)objcopy
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OBJDUMP = $(TOOLPREFIX)objdump
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CFLAGS = -fno-pic -static -fno-builtin -fno-strict-aliasing -O2 -Wall -MD -ggdb -m32 -Werror -fno-omit-frame-pointer
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XFLAGS = -m64 -mcmodel=large -ggdb
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# CFLAGS = -fno-pic -static -fno-builtin -fno-strict-aliasing -O2 -Wall -MD -ggdb -Werror -fno-omit-frame-pointer
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CFLAGS = -fno-pic -static -fno-builtin -fno-strict-aliasing -Wall -MD -ggdb -Werror -fno-omit-frame-pointer
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CFLAGS += -ffreestanding -fno-common -nostdlib $(XFLAGS)
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CFLAGS += $(shell $(CC) -fno-stack-protector -E -x c /dev/null >/dev/null 2>&1 && echo -fno-stack-protector)
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ASFLAGS = -m32 -gdwarf-2 -Wa,-divide
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ASFLAGS = -gdwarf-2 -Wa,-divide $(XFLAGS)
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# FreeBSD ld wants ``elf_i386_fbsd''
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LDFLAGS += -m $(shell $(LD) -V | grep elf_i386 2>/dev/null | head -n 1)
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LDFLAGS += -m $(shell $(LD) -V | grep elf_x86_64 2>/dev/null | head -n 1)
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LDFLAGS += -z max-page-size=4096
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# Disable PIE when possible (for Ubuntu 16.10 toolchain)
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ifneq ($(shell $(CC) -dumpspecs 2>/dev/null | grep -e '[^f]no-pie'),)
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@ -90,23 +95,10 @@ ifneq ($(shell $(CC) -dumpspecs 2>/dev/null | grep -e '[^f]nopie'),)
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CFLAGS += -fno-pie -nopie
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endif
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xv6.img: bootblock kernel
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dd if=/dev/zero of=xv6.img count=10000
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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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$(LD) $(LDFLAGS) -N -e start -Ttext 0x7C00 -o bootblock.o bootasm.o bootmain.o
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$(OBJDUMP) -S bootblock.o > bootblock.asm
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$(OBJCOPY) -S -O binary -j .text bootblock.o bootblock
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./sign.pl bootblock
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kernel: $(OBJS) entry.o entryother initcode kernel.ld
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$(LD) $(LDFLAGS) -T kernel.ld -o kernel entry.o $(OBJS) -b binary initcode entryother
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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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entryother: entryother.S
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$(CC) $(CFLAGS) -fno-pic -nostdinc -I. -c entryother.S
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@ -120,23 +112,6 @@ initcode: initcode.S
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$(OBJCOPY) -S -O binary initcode.out initcode
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$(OBJDUMP) -S initcode.o > initcode.asm
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kernel: $(OBJS) entry.o entryother initcode kernel.ld
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$(LD) $(LDFLAGS) -T kernel.ld -o kernel entry.o $(OBJS) -b binary initcode entryother
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$(OBJDUMP) -S kernel > kernel.asm
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$(OBJDUMP) -t kernel | sed '1,/SYMBOL TABLE/d; s/ .* / /; /^$$/d' > kernel.sym
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# kernelmemfs is a copy of kernel that maintains the
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# disk image in memory instead of writing to a disk.
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# This is not so useful for testing persistent storage or
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# exploring disk buffering implementations, but it is
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# great for testing the kernel on real hardware without
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# needing a scratch disk.
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MEMFSOBJS = $(filter-out ide.o,$(OBJS)) memide.o
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kernelmemfs: $(MEMFSOBJS) entry.o entryother initcode kernel.ld fs.img
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$(LD) $(LDFLAGS) -T kernel.ld -o kernelmemfs entry.o $(MEMFSOBJS) -b binary initcode entryother fs.img
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$(OBJDUMP) -S kernelmemfs > kernelmemfs.asm
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$(OBJDUMP) -t kernelmemfs | sed '1,/SYMBOL TABLE/d; s/ .* / /; /^$$/d' > kernelmemfs.sym
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tags: $(OBJS) entryother.S _init
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etags *.S *.c
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@ -190,8 +165,8 @@ fs.img: mkfs README $(UPROGS)
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clean:
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rm -f *.tex *.dvi *.idx *.aux *.log *.ind *.ilg \
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*.o *.d *.asm *.sym vectors.S bootblock entryother \
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initcode initcode.out kernel xv6.img fs.img kernelmemfs \
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xv6memfs.img mkfs .gdbinit \
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initcode initcode.out kernel fs.img kernelmemfs \
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mkfs .gdbinit \
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$(UPROGS)
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# make a printout
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@ -204,12 +179,6 @@ xv6.pdf: $(PRINT)
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print: xv6.pdf
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# run in emulators
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bochs : fs.img xv6.img
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if [ ! -e .bochsrc ]; then ln -s dot-bochsrc .bochsrc; fi
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bochs -q
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# try to generate a unique GDB port
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GDBPORT = $(shell expr `id -u` % 5000 + 25000)
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# QEMU's gdb stub command line changed in 0.11
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@ -219,25 +188,21 @@ QEMUGDB = $(shell if $(QEMU) -help | grep -q '^-gdb'; \
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ifndef CPUS
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CPUS := 2
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endif
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QEMUOPTS = -drive file=fs.img,index=1,media=disk,format=raw -drive file=xv6.img,index=0,media=disk,format=raw -smp $(CPUS) -m 512 $(QEMUEXTRA)
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qemu: fs.img xv6.img
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QEMUOPTS = -kernel kernel -drive file=fs.img,index=1,media=disk,format=raw -smp $(CPUS) -m 512 $(QEMUEXTRA)
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qemu: fs.img
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$(QEMU) -serial mon:stdio $(QEMUOPTS)
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qemu-memfs: xv6memfs.img
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$(QEMU) -drive file=xv6memfs.img,index=0,media=disk,format=raw -smp $(CPUS) -m 256
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qemu-nox: fs.img xv6.img
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qemu-nox: fs.img kernel
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$(QEMU) -nographic $(QEMUOPTS)
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.gdbinit: .gdbinit.tmpl
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.gdbinit: .gdbinit.tmpl-x64
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sed "s/localhost:1234/localhost:$(GDBPORT)/" < $^ > $@
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qemu-gdb: fs.img xv6.img .gdbinit
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qemu-gdb: fs.img kernel .gdbinit
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@echo "*** Now run 'gdb'." 1>&2
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$(QEMU) -serial mon:stdio $(QEMUOPTS) -S $(QEMUGDB)
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$(QEMU) $(QEMUOPTS) -S $(QEMUGDB)
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qemu-nox-gdb: fs.img xv6.img .gdbinit
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qemu-nox-gdb: fs.img kernel .gdbinit
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@echo "*** Now run 'gdb'." 1>&2
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$(QEMU) -nographic $(QEMUOPTS) -S $(QEMUGDB)
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