#include "types.h"

#include "param.h"

#include "memlayout.h"

#include "mmu.h"

#include "proc.h"

#include "defs.h"

#include "x86.h"

#include "elf.h"

int

exec(char *path, char **argv)

{

char *s, *last;

int i, off;

uint argc, sz, sp, ustack[3+MAXARG+1];

struct elfhdr elf;

struct inode *ip;

struct proghdr ph;

pde_t *pgdir, *oldpgdir;

if((ip = namei(path)) == 0)

return -1;

ilock(ip);

pgdir = 0;

// Check ELF header

if(readi(ip, (char*)&elf, 0, sizeof(elf)) < sizeof(elf))

goto bad;

if(elf.magic != ELF_MAGIC)

goto bad;

if((pgdir = setupkvm(kalloc)) == 0)

goto bad;

// Load program into memory.

// leave first page inaccessible (to make NULL ref fail)

sz = PGSIZE-1;

for(i=0, off=elf.phoff; i<elf.phnum; i++, off+=sizeof(ph)){

if(readi(ip, (char*)&ph, off, sizeof(ph)) != sizeof(ph))

goto bad;

if(ph.type != ELF_PROG_LOAD)

continue;

if(ph.memsz < ph.filesz)

goto bad;

if((sz = allocuvm(pgdir, sz, ph.vaddr + ph.memsz)) == 0)

goto bad;

if(loaduvm(pgdir, (char*)ph.vaddr, ip, ph.off, ph.filesz) < 0)

goto bad;

}

iunlockput(ip);

ip = 0;

// Allocate two pages at the next page boundary.

// Make the first inaccessible. Use the second as the user stack.

sz = PGROUNDUP(sz);

if((sz = allocuvm(pgdir, sz, sz + 2*PGSIZE)) == 0)

goto bad;

clearpteu(pgdir, (char*)(sz - 2*PGSIZE));

sp = sz;

// Push argument strings, prepare rest of stack in ustack.

for(argc = 0; argv[argc]; argc++) {

if(argc >= MAXARG)

goto bad;

sp = (sp - (strlen(argv[argc]) + 1)) & ~3;

if(copyout(pgdir, sp, argv[argc], strlen(argv[argc]) + 1) < 0)

goto bad;

ustack[3+argc] = sp;

}

ustack[3+argc] = 0;

ustack[0] = 0xffffffff; // fake return PC

ustack[1] = argc;

ustack[2] = sp - (argc+1)*4; // argv pointer

sp -= (3+argc+1) * 4;

if(copyout(pgdir, sp, ustack, (3+argc+1)*4) < 0)

goto bad;

// Save program name for debugging.

for(last=s=path; *s; s++)

if(*s == '/')

last = s+1;

safestrcpy(proc->name, last, sizeof(proc->name));

// hook up the old shared memory to the new addr space

// (no need to change refcount, because the old ref goes away with

// this exec, so it's +1 then -1 => 0 change

if (proc->shared) {

extern void mappages(pde_t *pgdir, void *va, uint size, uint pa, int perm);

mappages(pgdir, (char *)SHARED_V, PGSIZE, v2p(proc->shared->page), PTE_W|PTE_U);

}

// Commit to the user image.

oldpgdir = proc->pgdir;

proc->pgdir = pgdir;

proc->sz = sz;

proc->tf->eip = elf.entry; // main

proc->tf->esp = sp;

switchuvm(proc);

freevm(oldpgdir);

return 0;

bad:

if(pgdir)

freevm(pgdir);

if(ip)

iunlockput(ip);

return -1;

}