exec.c

#include "types.h"
#include "param.h"
#include "mmu.h"
#include "proc.h"
#include "defs.h"
#include "sh4.h"
#include "elf.h"

int
exec(char *path, char **argv)
{
#ifdef DEBUG
  cprintf("%s: path=%s\n", __func__, path);
  char **tmp;
  for(tmp=argv; *tmp != 0; ++tmp) {
    cprintf("%s: argv[%d]=%s\n", __func__, tmp-argv, *tmp);
  }
#endif
#ifdef DEBUGxxx
  cprintf("%s: oldpgdir=0x%x\n", __func__, proc->pgdir);
  dump_pde(proc->pgdir, 0, 2);
#endif
  char *mem, *s, *last;
  int i, argc, arglen, len, off;
  uint sz, sp, spbottom, argp;
  struct elfhdr elf;
  struct inode *ip;
  struct proghdr ph;
  pde_t *pgdir, *oldpgdir;

  pgdir = 0;
  sz = 0;

  if((ip = namei(path)) == 0)
    return -1;
  ilock(ip);

  // 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()))
    goto bad;

#ifdef DEBUG
  cprintf("%s: start of loading\n", __func__);
#endif
  // Load program into memory.
  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.va + ph.memsz)))
      goto bad;
    if(!loaduvm(pgdir, (char *)ph.va, ip, ph.offset, ph.filesz))
      goto bad;
  }
  iunlockput(ip);
#ifdef DEBUG
  cprintf("%s: end of loading\n", __func__);
#endif

  // Allocate and initialize stack at sz
  sz = spbottom = PGROUNDUP(sz);
  if(!(sz = allocuvm(pgdir, sz, sz + PGSIZE)))
    goto bad;
  mem = uva2ka(pgdir, (char *)spbottom);
#ifdef DEBUGxxx
  cprintf("%s: allocated user stack\n", __func__);
  dump_pgd(pgdir, 2);
#endif

  arglen = 0;
  for(argc=0; argv[argc]; argc++)
    arglen += strlen(argv[argc]) + 1;
  arglen = (arglen+3) & ~3;

  sp = sz;
  argp = sz - arglen - 4*(argc+1);

  // Copy argv strings and pointers to stack.
  *(uint*)(mem+argp-spbottom + 4*argc) = 0;  // argv[argc]
  for(i=argc-1; i>=0; i--){
    len = strlen(argv[i]) + 1;
    sp -= len;
    memmove(mem+sp-spbottom, argv[i], len);
    *(uint*)(mem+argp-spbottom + 4*i) = sp;  // argv[i]
  }

  // Stack frame for main(argc, argv), below arguments.
#if 0
  sp = argp;
  sp -= 4;
  *(uint*)(mem+sp-spbottom) = argp;
  sp -= 4;
  *(uint*)(mem+sp-spbottom) = argc;
  sp -= 4;
  *(uint*)(mem+sp-spbottom) = 0xffffffff;   // fake return pc
#else
  sp = argp;
  uint fakeret = 0xffffffff;
  asm volatile("ldc %0, r4_bank" :: "r"(argc));
  asm volatile("ldc %0, r5_bank" :: "r"(argp));
  asm volatile("lds %0, pr" :: "r"(fakeret));  // fake return pc
#endif

  // Save program name for debugging.
  for(last=s=path; *s; s++)
    if(*s == '/')
      last = s+1;
  safestrcpy(proc->name, last, sizeof(proc->name));

  // Commit to the user image.
  oldpgdir = proc->pgdir;
  proc->pgdir = pgdir;
  proc->sz = sz;
#if 0
  proc->tf->eip = elf.entry;  // main
  proc->tf->esp = sp;
#else
  proc->tf->spc = elf.entry;
  proc->tf->sgr = sp;
#ifdef DEBUG
  cprintf("%s: spc=0x%x, sgr=0x%x\n", 
      __func__, proc->tf->spc, proc->tf->sgr);
#endif
#endif

  switchuvm(proc); 

  freevm(oldpgdir);

#ifdef DEBUG
  cprintf("%s: finish\n", __func__);
#endif
  return 0;

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