exec compiles but argstr() doesn't work yet

This commit is contained in:
Robert Morris 2019-05-31 12:43:20 -04:00
parent 5d34fa2a48
commit 7fd1f1eb0a
8 changed files with 207 additions and 69 deletions

View file

@ -19,7 +19,9 @@ OBJS = \
sleeplock.o \
file.o \
pipe.o \
ramdisk.o
ramdisk.o \
exec.o \
sysfile.o
XXXOBJS = \
bio.o\

7
defs.h
View file

@ -107,6 +107,8 @@ int cpuid(void);
void exit(void);
int fork(void);
int growproc(int);
pagetable_t proc_pagetable(struct proc *);
void proc_freepagetable(pagetable_t, uint64);
int kill(int);
struct cpu* mycpu(void);
struct cpu* getmycpu(void);
@ -178,11 +180,14 @@ void kvminit(void);
void kvmswitch(void);
pagetable_t uvmcreate(void);
void uvminit(pagetable_t, char *, uint);
int uvmdealloc(pagetable_t, uint64, uint64);
uint64 uvmalloc(pagetable_t, uint64, uint64);
uint64 uvmdealloc(pagetable_t, uint64, uint64);
void uvmcopy(pagetable_t, pagetable_t, uint64);
void uvmfree(pagetable_t, uint64);
void mappages(pagetable_t, uint64, uint64, uint64, int);
void unmappages(pagetable_t, uint64, uint64, int);
uint64 walkaddr(pagetable_t, uint64);
int copyout(pagetable_t, uint64, char *, uint64);
// number of elements in fixed-size array
#define NELEM(x) (sizeof(x)/sizeof((x)[0]))

74
exec.c
View file

@ -1,14 +1,13 @@
#include "types.h"
#include "param.h"
#include "memlayout.h"
#include "mmu.h"
#include "riscv.h"
#include "proc.h"
#include "defs.h"
#include "traps.h"
#include "msr.h"
#include "x86.h"
#include "elf.h"
static int loadseg(pde_t *pgdir, uint64 addr, struct inode *ip, uint offset, uint sz);
int
exec(char *path, char **argv)
{
@ -18,10 +17,12 @@ exec(char *path, char **argv)
struct elfhdr elf;
struct inode *ip;
struct proghdr ph;
pde_t *pgdir, *oldpgdir;
pagetable_t pagetable = 0, oldpagetable;
struct proc *p = myproc();
uint64 oldsz = p->sz;
printf("EXEC\n");
begin_op();
if((ip = namei(path)) == 0){
@ -29,7 +30,6 @@ exec(char *path, char **argv)
return -1;
}
ilock(ip);
pgdir = 0;
// Check ELF header
if(readi(ip, (char*)&elf, 0, sizeof(elf)) != sizeof(elf))
@ -37,7 +37,7 @@ exec(char *path, char **argv)
if(elf.magic != ELF_MAGIC)
goto bad;
if((pgdir = setupkvm()) == 0)
if((pagetable = proc_pagetable(p)) == 0)
goto bad;
// Load program into memory.
@ -51,11 +51,11 @@ exec(char *path, char **argv)
goto bad;
if(ph.vaddr + ph.memsz < ph.vaddr)
goto bad;
if((sz = allocuvm(pgdir, sz, ph.vaddr + ph.memsz)) == 0)
if((sz = uvmalloc(pagetable, sz, ph.vaddr + ph.memsz)) == 0)
goto bad;
if(ph.vaddr % PGSIZE != 0)
goto bad;
if(loaduvm(pgdir, (char*)ph.vaddr, ip, ph.off, ph.filesz) < 0)
if(loadseg(pagetable, ph.vaddr, ip, ph.off, ph.filesz) < 0)
goto bad;
}
iunlockput(ip);
@ -63,11 +63,10 @@ exec(char *path, char **argv)
ip = 0;
// Allocate two pages at the next page boundary.
// Make the first inaccessible. Use the second as the user stack.
// Use the second as the user stack.
sz = PGROUNDUP(sz);
if((sz = allocuvm(pgdir, sz, sz + 2*PGSIZE)) == 0)
if((sz = uvmalloc(pagetable, sz, sz + 2*PGSIZE)) == 0)
goto bad;
clearpteu(pgdir, (char*)(sz - 2*PGSIZE));
sp = sz;
// Push argument strings, prepare rest of stack in ustack.
@ -75,7 +74,7 @@ exec(char *path, char **argv)
if(argc >= MAXARG)
goto bad;
sp = (sp - (strlen(argv[argc]) + 1)) & ~(sizeof(uint64)-1);
if(copyout(pgdir, sp, argv[argc], strlen(argv[argc]) + 1) < 0)
if(copyout(pagetable, sp, argv[argc], strlen(argv[argc]) + 1) < 0)
goto bad;
ustack[3+argc] = sp;
}
@ -85,11 +84,12 @@ exec(char *path, char **argv)
ustack[1] = argc;
ustack[2] = sp - (argc+1)*sizeof(uint64); // argv pointer
p->sf->rdi = argc;
p->sf->rsi = sp - (argc+1)*sizeof(uint64);
// arguments to user main(argc, argv)
p->tf->a0 = argc;
p->tf->a1 = sp - (argc+1)*sizeof(uint64);
sp -= (3+argc+1) * sizeof(uint64);
if(copyout(pgdir, sp, ustack, (3+argc+1)*sizeof(uint64)) < 0)
if(copyout(pagetable, sp, (char *)ustack, (3+argc+1)*sizeof(uint64)) < 0)
goto bad;
// Save program name for debugging.
@ -99,21 +99,47 @@ exec(char *path, char **argv)
safestrcpy(p->name, last, sizeof(p->name));
// Commit to the user image.
oldpgdir = p->pgdir;
p->pgdir = pgdir;
oldpagetable = p->pagetable;
p->pagetable = pagetable;
p->sz = sz;
p->sf->rcx = elf.entry; // main
p->sf->rsp = sp;
switchuvm(p);
freevm(oldpgdir, oldsz);
p->tf->epc = elf.entry; // initial program counter = main
p->tf->sp = sp; // initial stack pointer
proc_freepagetable(oldpagetable, oldsz);
return 0;
bad:
if(pgdir)
freevm(pgdir, sz);
if(pagetable)
proc_freepagetable(pagetable, sz);
if(ip){
iunlockput(ip);
end_op();
}
return -1;
}
// Load a program segment into pagetable at virtual address va.
// va must be page-aligned
// and the pages from va to va+sz must already be mapped.
// Returns 0 on success, -1 on failure.
static int
loadseg(pagetable_t pagetable, uint64 va, struct inode *ip, uint offset, uint sz)
{
uint i, n;
uint64 pa;
pte_t *pte;
if((va % PGSIZE) != 0)
panic("loadseg: va must be page aligned");
for(i = 0; i < sz; i += PGSIZE){
pa = walkaddr(pagetable, va + i);
if(pa == 0)
panic("loadseg: address should exist");
if(sz - i < PGSIZE)
n = sz - i;
else
n = PGSIZE;
if(readi(ip, (char *)pa, offset+i, n) != n)
return -1;
}
return 0;
}

56
proc.c
View file

@ -94,18 +94,7 @@ found:
}
// An empty user page table.
p->pagetable = uvmcreate();
// map the trampoline code (for system call return)
// at the highest user virtual address.
// only the supervisor uses it, on the way
// to/from user space, so not PTE_U.
mappages(p->pagetable, TRAMPOLINE, PGSIZE,
(uint64)trampstart, PTE_R | PTE_X);
// map the trapframe, for trampoline.S.
mappages(p->pagetable, (TRAMPOLINE - PGSIZE), PGSIZE,
(uint64)(p->tf), PTE_R | PTE_W);
p->pagetable = proc_pagetable(p);
// Set up new context to start executing at forkret,
// which returns to user space.
@ -116,6 +105,45 @@ found:
return p;
}
// Create a page table for a given process,
// with no users pages, but with trampoline pages.
// Called both when creating a process, and
// by exec() when building tentative new memory image,
// which might fail.
pagetable_t
proc_pagetable(struct proc *p)
{
pagetable_t pagetable;
// An empty user page table.
pagetable = uvmcreate();
// map the trampoline code (for system call return)
// at the highest user virtual address.
// only the supervisor uses it, on the way
// to/from user space, so not PTE_U.
mappages(pagetable, TRAMPOLINE, PGSIZE,
(uint64)trampstart, PTE_R | PTE_X);
// map the trapframe, for trampoline.S.
mappages(pagetable, (TRAMPOLINE - PGSIZE), PGSIZE,
(uint64)(p->tf), PTE_R | PTE_W);
return pagetable;
}
// Free a process's page table, and free the
// physical memory the page table refers to.
// Called both when a process exits and from
// exec() if it fails.
void
proc_freepagetable(pagetable_t pagetable, uint64 sz)
{
unmappages(pagetable, TRAMPOLINE, PGSIZE, 0);
unmappages(pagetable, TRAMPOLINE-PGSIZE, PGSIZE, 0);
uvmfree(pagetable, sz);
}
// a user program that calls exec("/init")
// od -t xC initcode
unsigned char initcode[] = {
@ -295,9 +323,7 @@ wait(void)
np->kstack = 0;
kfree((void*)np->tf);
np->tf = 0;
unmappages(np->pagetable, TRAMPOLINE, PGSIZE, 0);
unmappages(np->pagetable, TRAMPOLINE-PGSIZE, PGSIZE, 0);
uvmfree(np->pagetable, np->sz);
proc_freepagetable(np->pagetable, np->sz);
np->pagetable = 0;
np->pid = 0;
np->parent = 0;

View file

@ -148,24 +148,24 @@ static int (*syscalls[])(void) = {
[SYS_fork] sys_fork,
[SYS_exit] sys_exit,
[SYS_wait] sys_wait,
//[SYS_pipe] sys_pipe,
//[SYS_read] sys_read,
[SYS_pipe] sys_pipe,
[SYS_read] sys_read,
//[SYS_kill] sys_kill,
//[SYS_exec] sys_exec,
//[SYS_fstat] sys_fstat,
//[SYS_chdir] sys_chdir,
//[SYS_dup] sys_dup,
[SYS_exec] sys_exec,
[SYS_fstat] sys_fstat,
[SYS_chdir] sys_chdir,
[SYS_dup] sys_dup,
[SYS_getpid] sys_getpid,
//[SYS_sbrk] sys_sbrk,
//[SYS_sleep] sys_sleep,
//[SYS_uptime] sys_uptime,
//[SYS_open] sys_open,
//[SYS_write] sys_write,
//[SYS_mknod] sys_mknod,
//[SYS_unlink] sys_unlink,
//[SYS_link] sys_link,
//[SYS_mkdir] sys_mkdir,
//[SYS_close] sys_close,
[SYS_open] sys_open,
[SYS_write] sys_write,
[SYS_mknod] sys_mknod,
[SYS_unlink] sys_unlink,
[SYS_link] sys_link,
[SYS_mkdir] sys_mkdir,
[SYS_close] sys_close,
};
static void

View file

@ -5,10 +5,10 @@
//
#include "types.h"
#include "riscv.h"
#include "defs.h"
#include "param.h"
#include "stat.h"
#include "mmu.h"
#include "proc.h"
#include "fs.h"
#include "spinlock.h"
@ -401,22 +401,32 @@ sys_exec(void)
int i;
uint64 uargv, uarg;
printf("sys_exec\n");
if(argstr(0, &path) < 0 || argaddr(1, &uargv) < 0){
printf("error 1\n");
return -1;
}
memset(argv, 0, sizeof(argv));
for(i=0;; i++){
if(i >= NELEM(argv))
if(i >= NELEM(argv)){
printf("error 2\n");
return -1;
if(fetchaddr(uargv+sizeof(uint64)*i, (uint64*)&uarg) < 0)
}
if(fetchaddr(uargv+sizeof(uint64)*i, (uint64*)&uarg) < 0){
printf("error 3\n");
return -1;
}
if(uarg == 0){
argv[i] = 0;
break;
}
if(fetchstr(uarg, &argv[i]) < 0)
if(fetchstr(uarg, &argv[i]) < 0){
printf("error 4\n");
return -1;
}
}
printf("calling exec\n");
return exec(path, argv);
}

1
trap.c
View file

@ -45,7 +45,6 @@ usertrap(void)
if(r_scause() == 8){
// system call
printf("usertrap(): system call pid=%d syscall=%d\n", p->pid, p->tf->a7);
// sepc points to the ecall instruction,
// but we want to return to the next instruction.

90
vm.c
View file

@ -71,9 +71,9 @@ kvmswitch(void)
// 12..20 -- 9 bits of level-0 index.
// 0..12 -- 12 bits of byte offset within the page.
static pte_t *
walk(pagetable_t pagetable, const void *va, int alloc)
walk(pagetable_t pagetable, uint64 va, int alloc)
{
if((uint64)va >= MAXVA)
if(va >= MAXVA)
panic("walk");
for(int level = 2; level > 0; level--) {
@ -90,17 +90,38 @@ walk(pagetable_t pagetable, const void *va, int alloc)
return &pagetable[PX(0, va)];
}
// Look up a virtual address, return the physical address,
// Can only be used to look up user pages.
// or 0 if not mapped.
uint64
walkaddr(pagetable_t pagetable, uint64 va)
{
pte_t *pte;
uint64 pa;
pte = walk(pagetable, va, 0);
if(pte == 0)
return 0;
if((*pte & PTE_V) == 0)
return 0;
if((*pte & PTE_U) == 0)
return 0;
pa = PTE2PA(*pte);
return pa;
}
// Create PTEs for virtual addresses starting at va that refer to
// physical addresses starting at pa. va and size might not
// be page-aligned.
void
mappages(pagetable_t pagetable, uint64 va, uint64 size, uint64 pa, int perm)
{
char *a, *last;
uint64 a, last;
pte_t *pte;
a = (char*)PGROUNDDOWN(va);
last = (char*)PGROUNDDOWN(va + size - 1);
a = PGROUNDDOWN(va);
last = PGROUNDDOWN(va + size - 1);
for(;;){
if((pte = walk(pagetable, a, 1)) == 0)
panic("mappages: walk");
@ -120,12 +141,12 @@ mappages(pagetable_t pagetable, uint64 va, uint64 size, uint64 pa, int perm)
void
unmappages(pagetable_t pagetable, uint64 va, uint64 size, int do_free)
{
char *a, *last;
uint64 a, last;
pte_t *pte;
uint64 pa;
a = (char*)PGROUNDDOWN(va);
last = (char*)PGROUNDDOWN(va + size - 1);
a = PGROUNDDOWN(va);
last = PGROUNDDOWN(va + size - 1);
for(;;){
if((pte = walk(pagetable, a, 0)) == 0)
panic("unmappages: walk");
@ -173,11 +194,35 @@ uvminit(pagetable_t pagetable, char *src, uint sz)
memmove(mem, src, sz);
}
// Allocate PTEs and physical memory to grow process from oldsz to
// newsz, which need not be page aligned. Returns new size or 0 on error.
uint64
uvmalloc(pagetable_t pagetable, uint64 oldsz, uint64 newsz)
{
char *mem;
uint64 a;
if(newsz < oldsz)
return oldsz;
a = PGROUNDUP(oldsz);
for(; a < newsz; a += PGSIZE){
mem = kalloc();
if(mem == 0){
uvmdealloc(pagetable, newsz, oldsz);
return 0;
}
memset(mem, 0, PGSIZE);
mappages(pagetable, a, PGSIZE, (uint64)mem, PTE_W|PTE_X|PTE_R);
}
return newsz;
}
// Deallocate user pages to bring the process size from oldsz to
// newsz. oldsz and newsz need not be page-aligned, nor does newsz
// need to be less than oldsz. oldsz can be larger than the actual
// process size. Returns the new process size.
int
uint64
uvmdealloc(pagetable_t pagetable, uint64 oldsz, uint64 newsz)
{
if(newsz >= oldsz)
@ -229,7 +274,7 @@ uvmcopy(pagetable_t old, pagetable_t new, uint64 sz)
char *mem;
for(i = 0; i < sz; i += PGSIZE){
if((pte = walk(old, (void *) i, 0)) == 0)
if((pte = walk(old, i, 0)) == 0)
panic("copyuvm: pte should exist");
if((*pte & PTE_V) == 0)
panic("copyuvm: page not present");
@ -241,3 +286,28 @@ uvmcopy(pagetable_t old, pagetable_t new, uint64 sz)
mappages(new, i, PGSIZE, (uint64)mem, flags);
}
}
// Copy len bytes from src to virtual address dstva in a given page table.
// Most useful when pagetable is not the current page table.
// Return 0 on success, -1 on error.
int
copyout(pagetable_t pagetable, uint64 dstva, char *src, uint64 len)
{
uint64 n, va0, pa0;
while(len > 0){
va0 = (uint)PGROUNDDOWN(dstva);
pa0 = walkaddr(pagetable, va0);
if(pa0 == 0)
return -1;
n = PGSIZE - (dstva - va0);
if(n > len)
n = len;
memmove((void *)(pa0 + (dstva - va0)), src, n);
len -= n;
src += n;
dstva = va0 + PGSIZE;
}
return 0;
}