ab0db651af
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
104 lines
2.6 KiB
C
104 lines
2.6 KiB
C
#include "types.h"
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#include "defs.h"
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#include "param.h"
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#include "memlayout.h"
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#include "mmu.h"
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#include "proc.h"
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#include "x86.h"
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extern pde_t *kpgdir;
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extern char end[]; // first address after kernel loaded from ELF file
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static void main(void) __attribute__((noreturn));
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static void startothers(void);
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// Bootstrap processor starts running C code here.
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// Allocate a real stack and switch to it, first
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// doing some setup required for memory allocator to work.
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int
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bpmain(uint64 mbmagic, uint64 mbaddr)
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{
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if(mbmagic != 0x2badb002)
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panic("multiboot header not found");
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kinit1(end, P2V(4*1024*1024)); // phys page allocator
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kvmalloc(); // kernel page table
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mpinit(); // detect other processors
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lapicinit(); // interrupt controller
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seginit(); // segment descriptors
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picinit(); // disable pic
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ioapicinit(); // another interrupt controller
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consoleinit(); // console hardware
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uartinit(); // serial port
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pinit(); // process table
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tvinit(); // trap vectors
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binit(); // buffer cache
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fileinit(); // file table
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ideinit(); // disk
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startothers(); // start other processors
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kinit2(P2V(4*1024*1024), P2V(PHYSTOP)); // must come after startothers()
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userinit(); // first user process
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main();
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return 0;
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}
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// Common CPU setup code.
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static void
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main(void)
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{
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cprintf("cpu%d: starting %d\n", cpuid(), cpuid());
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idtinit(); // load idt register
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xchg(&(mycpu()->started), 1); // tell startothers() we're up
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scheduler(); // start running processes
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}
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// Other CPUs jump here from entryother.S.
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void
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apmain(void)
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{
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switchkvm();
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seginit();
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lapicinit();
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main();
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}
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void apstart(void);
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// Start the non-boot (AP) processors.
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static void
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startothers(void)
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{
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extern uchar _binary_entryother_start[], _binary_entryother_size[];
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uchar *code;
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struct cpu *c;
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char *stack;
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// Write entry code to unused memory at 0x7000.
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// The linker has placed the image of entryother.S in
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// _binary_entryother_start.
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code = P2V(0x7000);
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memmove(code, _binary_entryother_start, (uint64)_binary_entryother_size);
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for(c = cpus; c < cpus+ncpu; c++){
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if(c == mycpu()) // We've started already.
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continue;
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// Tell entryother.S what stack to use, where to enter, and what
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// pgdir to use. We cannot use kpgdir yet, because the AP processor
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// is running in low memory, so we use entrypgdir for the APs too.
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stack = kalloc();
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*(uint32*)(code-4) = V2P(apstart);
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*(uint64*)(code-12) = (uint64) (stack+KSTACKSIZE);
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lapicstartap(c->apicid, V2P(code));
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// wait for cpu to finish mpmain()
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while(c->started == 0)
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;
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}
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}
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