summaryrefslogtreecommitdiff
path: root/trapasm.S
AgeCommit message (Collapse)AuthorFilesLines
2019-05-31-initrd fs.img, ramdisk.c, file systemRobert Morris1-132/+0
2018-10-09Separate system call path from trap path. Passes usertests on 1 and 2 cpus.Frans Kaashoek1-43/+35
2018-09-29xFrans Kaashoek1-2/+5
2018-09-29Make sysexit and trapret paths the same, so that forkret can return throughFrans Kaashoek1-5/+6
either path. This helped tracking down a bug: use 144 instead of 32 to find cs in trapframe so that gs is correctly saved and restored. For good measure update linker script, because newer versions of GCC sometimes places symbols passed end.
2018-09-23Checkpoint port of xv6 to x86-64. Passed usertests on 2 processors a few times.Frans Kaashoek1-23/+127
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
2017-08-09Update comment to reflect xv6 doesn't have per-cpu segments anymoreFrans Kaashoek1-1/+1
2017-02-01Eliminate code for gs trick to track per-cpu state. We rely on lapiccpunum()Frans Kaashoek1-3/+0
to find a per-cpu id with which we locate a cpu's cpu struct.
2011-08-08One definition of several macros and constantsFrans Kaashoek1-3/+1
2009-07-11initproc, usegment, swtch tweaksRuss Cox1-8/+0
2009-05-31clean up %fs %gs usersc1-3/+0
2009-05-31sync with c; .text is impliedrsc1-7/+13
2008-09-24always save and restore %fs, %gs to ensure old segment entries are neverkolya1-0/+4
accessible to user from the hidden CPU segment registers.
2007-08-28nitsrsc1-3/+1
2007-08-27Replace yield system call with sleep.rsc1-1/+1
2007-08-27formatting, fix commentrsc1-16/+21
2007-08-22PDF at http://am.lcs.mit.edu/~rsc/xv6.pdfrsc1-3/+0
Various changes made while offline. + bwrite sector argument is redundant; use b->sector. + reformatting of files for nicer PDF page breaks + distinguish between locked, unlocked inodes in type signatures + change FD_FILE to FD_INODE + move userinit (nee proc0init) to proc.c + move ROOTDEV to param.h + always parenthesize sizeof argument
2006-09-06standardize various * conventionsrsc1-2/+2
2006-09-06spacing fixes: no tabs, 2-space indents (for rtm)rsc1-27/+27
2006-08-29prune unneeded panics and debug outputrtm1-2/+0
2006-07-16Attempt to clean up newproc somewhat.rsc1-3/+3
Also remove all calls to memcpy in favor of memmove, which has defined semantics when the ranges overlap. The fact that memcpy was working in console.c to scroll the screen is not guaranteed by all implementations.
2006-07-16New scheduler.rsc1-3/+9
Removed cli and sti stack in favor of tracking number of locks held on each CPU and explicit conditionals in spinlock.c.
2006-07-12no more big kernel lockrtm1-4/+0
succeeds at usertests.c pipe test
2006-07-11Changes to allow use of native x86 ELF compilers, which on myrsc1-2/+3
Linux 2.4 box using gcc 3.4.6 don't seem to follow the same conventions as the i386-jos-elf-gcc compilers. Can run make 'TOOLPREFIX=' or edit the Makefile. curproc[cpu()] can now be NULL, indicating that no proc is running. This seemed safer to me than having curproc[0] and curproc[1] both pointing at proc[0] potentially. The old implementation of swtch depended on the stack frame layout used inside swtch being okay to return from on the other stack (exactly the V6 you are not expected to understand this). It also could be called in two contexts: at boot time, to schedule the very first process, and later, on behalf of a process, to sleep or schedule some other process. I split this into two functions: scheduler and swtch. The scheduler is now a separate never-returning function, invoked by each cpu once set up. The scheduler looks like: scheduler() { setjmp(cpu.context); pick proc to schedule blah blah blah longjmp(proc.context) } The new swtch is intended to be called only when curproc[cpu()] is not NULL, that is, only on behalf of a user proc. It does: swtch() { if(setjmp(proc.context) == 0) longjmp(cpu.context) } to save the current proc context and then jump over to the scheduler, running on the cpu stack. Similarly the system call stubs are now in assembly in usys.S to avoid needing to know the details of stack frame layout used by the compiler. Also various changes in the debugging prints.
2006-06-22bug in trapretrtm1-0/+1
2006-06-22compile "user programs"rtm1-0/+2
curproc array
2006-06-22checkpoint. booting second processor. stack is messed up, but thanks to cliffkaashoek1-0/+5
and plan 9 code, at least boots and gets into C code.
2006-06-15primitive fork and exit system callsrtm1-0/+1
2006-06-13more or less take traps/interruptsrtm1-0/+16
2006-06-12importrtm1-0/+12