exec.c

#include "types.h"
#include "param.h"
#include "memlayout.h"
#include "mmu.h"
#include "spinlock.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, alive;
  uint argc, sz, sp, ustack[3+MAXARG+1];
  struct elfhdr elf;
  struct inode *ip;
  struct proghdr ph;
  pde_t *pgdir, *oldpgdir;
  struct proc *curproc = myproc();
  struct proc *p;

  
  // Kill all other threads in the process
  acquire(&ptable.lock);

  if(curproc->killed){
    release(&ptable.lock);
    return -1;
  }

  for (p = ptable.proc; p < &ptable.proc[NPROC]; p++) {
    if (p->tgid == curproc->tgid && p->pid != curproc->pid) {
      p->killed = 1;
      if (p->state == SLEEPING) 
        p->state = RUNNABLE;
    }
  }
  release(&ptable.lock);

  // Wait for them to die
  acquire(&ptable.lock);
  for (;;) {
    alive = 0;
    for (p = ptable.proc; p < &ptable.proc[NPROC]; p++) {
      // assumption: wait() will clear PID, TID
      if (p->tgid == curproc->tgid && p != curproc 
                                   && p->state != ZOMBIE) {
        alive = 1;
	break;
      }
    }
    if (alive) {
      sleep(curproc->process, &ptable.lock);
    }
    else {
      break;
    }
  }
  release(&ptable.lock);

  // become the thread group leader
  curproc->process->pid = curproc->pid;
  curproc->pid = curproc->tgid;
  
  // "ensure" that threadcount is 1
  curproc->process->threadcount = 1;

  // flush the locks
  initlock(&curproc->process->vlock, "vlock");
  initlock(&curproc->process->cwdlock, "cwdlock");

  // the process is running, and does not need wakeups
  curproc->process->lostwakeup = 0;

  begin_op();

  if((ip = namei(path)) == 0){
    end_op();
    cprintf("exec: fail\n");
    return -1;
  }
  ilock(ip);
  pgdir = 0;

  // Check ELF header
  if(readi(ip, (char*)&elf, 0, sizeof(elf), 0) != sizeof(elf))
    goto bad;
  if(elf.magic != ELF_MAGIC)
    goto bad;

  if((pgdir = setupkvm()) == 0)
    goto bad;

  // Load program into memory.
  sz = 0;
  for(i=0, off=elf.phoff; i<elf.phnum; i++, off+=sizeof(ph)){
    if(readi(ip, (char*)&ph, off, sizeof(ph), 0) != sizeof(ph))
      goto bad;
    if(ph.type != ELF_PROG_LOAD)
      continue;
    if(ph.memsz < ph.filesz)
      goto bad;
    if(ph.vaddr + ph.memsz < ph.vaddr)
      goto bad;
    if((sz = allocuvm(pgdir, 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)
      goto bad;
  }
  iunlockput(ip);
  end_op();
  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(curproc->name, last, sizeof(curproc->name));

  initlock(&curproc->vlock, "vlock");

  // Commit to the user image.

  acquire(&curproc->vlock);
  oldpgdir = curproc->pgdir;
  curproc->pgdir = pgdir;
  curproc->sz = sz;
  release(&curproc->vlock);

  curproc->tf->eip = elf.entry;  // main
  curproc->tf->esp = sp;
  switchuvm(curproc);
  freevm(oldpgdir);
  return 0;

 bad:
  if(pgdir)
    freevm(pgdir);
  if(ip){
    iunlockput(ip);
    end_op();
  }
  return -1;
}