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authorFrans Kaashoek <[email protected]>2018-09-23 08:24:42 -0400
committerFrans Kaashoek <[email protected]>2018-09-23 08:35:30 -0400
commitab0db651af6f1ffa8fe96909ce16ae314d65c3fb (patch)
treec429f8ee36fa7da1e25f564a160b031613ca05e9 /exec.c
parentb818915f793cd20c5d1e24f668534a9d690f3cc8 (diff)
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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
Diffstat (limited to 'exec.c')
-rw-r--r--exec.c30
1 files changed, 18 insertions, 12 deletions
diff --git a/exec.c b/exec.c
index b40134f..b1a9229 100644
--- a/exec.c
+++ b/exec.c
@@ -4,6 +4,8 @@
#include "mmu.h"
#include "proc.h"
#include "defs.h"
+#include "traps.h"
+#include "msr.h"
#include "x86.h"
#include "elf.h"
@@ -12,18 +14,18 @@ exec(char *path, char **argv)
{
char *s, *last;
int i, off;
- uint argc, sz, sp, ustack[3+MAXARG+1];
+ uint64 argc, sz, sp, ustack[3+MAXARG+1];
struct elfhdr elf;
struct inode *ip;
struct proghdr ph;
pde_t *pgdir, *oldpgdir;
struct proc *curproc = myproc();
-
+ uint64 oldsz = curproc->sz;
+
begin_op();
if((ip = namei(path)) == 0){
end_op();
- cprintf("exec: fail\n");
return -1;
}
ilock(ip);
@@ -72,7 +74,7 @@ exec(char *path, char **argv)
for(argc = 0; argv[argc]; argc++) {
if(argc >= MAXARG)
goto bad;
- sp = (sp - (strlen(argv[argc]) + 1)) & ~3;
+ sp = (sp - (strlen(argv[argc]) + 1)) & ~(sizeof(uint64)-1);
if(copyout(pgdir, sp, argv[argc], strlen(argv[argc]) + 1) < 0)
goto bad;
ustack[3+argc] = sp;
@@ -81,10 +83,13 @@ exec(char *path, char **argv)
ustack[0] = 0xffffffff; // fake return PC
ustack[1] = argc;
- ustack[2] = sp - (argc+1)*4; // argv pointer
+ ustack[2] = sp - (argc+1)*sizeof(uint64); // argv pointer
+
+ curproc->tf->rdi = argc;
+ curproc->tf->rsi = sp - (argc+1)*sizeof(uint64);
- sp -= (3+argc+1) * 4;
- if(copyout(pgdir, sp, ustack, (3+argc+1)*4) < 0)
+ sp -= (3+argc+1) * sizeof(uint64);
+ if(copyout(pgdir, sp, ustack, (3+argc+1)*sizeof(uint64)) < 0)
goto bad;
// Save program name for debugging.
@@ -92,20 +97,21 @@ exec(char *path, char **argv)
if(*s == '/')
last = s+1;
safestrcpy(curproc->name, last, sizeof(curproc->name));
-
+
// Commit to the user image.
oldpgdir = curproc->pgdir;
curproc->pgdir = pgdir;
curproc->sz = sz;
- curproc->tf->eip = elf.entry; // main
- curproc->tf->esp = sp;
+ curproc->tf->rip = elf.entry; // main
+ curproc->tf->rcx = elf.entry;
+ curproc->tf->rsp = sp;
switchuvm(curproc);
- freevm(oldpgdir);
+ freevm(oldpgdir, oldsz);
return 0;
bad:
if(pgdir)
- freevm(pgdir);
+ freevm(pgdir, sz);
if(ip){
iunlockput(ip);
end_op();