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2018-09-23Checkpoint port of xv6 to x86-64. Passed usertests on 2 processors a few times.Frans Kaashoek1-88/+0
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
2016-08-10nitsRobert Morris1-1/+1
2011-09-12comment nitsRobert Morris1-3/+3
2011-08-26segment register -> segment descriptorRobert Morris1-1/+1
2011-08-08One definition of several macros and constantsFrans Kaashoek1-5/+3
2011-02-19xv6: formatting, cleanup, rev5 (take 2)Russ Cox1-21/+12
2010-09-13change some comments, maybe more informativeRobert Morris1-3/+8
delete most comments from bootother.S (since copy of bootasm.S) ksegment() -> seginit() move more stuff from main() to mainc()
2010-08-05add some commentsRobert Morris1-2/+4
find out the hard way why user and kernel must have separate segment descriptors
2010-07-02Initial version of single-cpu xv6 with page tablesFrans Kaashoek1-1/+1
2009-12-018ae0 instead of 8e00, thanks yandongFrans Kaashoek1-1/+1
2009-07-11bootasm cleanupRuss Cox1-2/+1
2009-05-31clean up %fs %gs usersc1-2/+1
2009-05-31sync with c; .text is impliedrsc1-9/+12
2009-03-08xv6: boot loader adjustmentsrsc1-10/+16
do Bochs breakpoint and spin in bootasm.S. not needed in bootmain too. fix readseg bug (rounding of va). zero segments when memsz > filesz. no need to clear BSS in kernel main. make bootother.S like bootasm.S
2007-09-15fix commentsrtm1-1/+1
2007-08-28nitsrsc1-2/+2
2007-08-28cmain -> bootmainrsc1-2/+2
2007-08-24bring bootasm and bootother more in syncrsc1-31/+25
2007-08-24Rework comments a bit.rsc1-29/+25
Move initialization of %sp after protected mode jump and change to %esp.
2007-08-22better commentrsc1-7/+3
2006-09-08shortenrsc1-13/+9
2006-09-08some comment changeskaashoek1-1/+1
2006-09-06wrap long linesrsc1-23/+23
2006-09-06standardize various * conventionsrsc1-15/+15
2006-09-06spacing fixes: no tabs, 2-space indents (for rtm)rsc1-66/+73
2006-09-03remove duplicationkaashoek1-3/+3
don't use the same name for two different pieces of code
2006-09-03centralize creditskaashoek1-4/+0
2006-08-29prune unneeded panics and debug outputrtm1-0/+4
2006-06-22checkpoint. booting second processor. stack is messed up, but thanks to cliffkaashoek1-14/+1
and plan 9 code, at least boots and gets into C code.
2006-06-12importrtm1-0/+109