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#include "types.h"
#include "param.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 sz = 0;
struct elfhdr elf;
struct inode *ip = 0;
struct proghdr ph;
pde_t *pgdir = 0, *oldpgdir;
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;
// 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);
// Allocate a one-page stack at the next page boundary
sz = PGROUNDUP(sz);
if(!(sz = allocuvm(pgdir, sz, sz + PGSIZE)))
goto bad;
// initialize stack content:
// "argumentN" -- nul-terminated string
// ...
// "argument0"
// 0 -- argv[argc]
// address of argumentN
// ...
// address of argument0 -- argv[0]
// address of address of argument0 -- argv argument to main()
// argc -- argc argument to main()
// ffffffff -- return PC for main() call
uint sp = sz;
// count arguments
int argc;
for(argc = 0; argv[argc]; argc++)
;
if(argc >= MAXARG)
goto bad;
// push strings and remember where they are
uint strings[MAXARG];
for(i = argc - 1; i >= 0; --i){
sp -= strlen(argv[i]) + 1;
strings[i] = sp;
copyout(pgdir, sp, argv[i], strlen(argv[i]) + 1);
}
// push 0 for argv[argc]
sp -= 4;
int zero = 0;
copyout(pgdir, sp, &zero, 4);
// push argv[] elements
for(i = argc - 1; i >= 0; --i){
sp -= 4;
copyout(pgdir, sp, &strings[i], 4);
}
// push argv
uint argvaddr = sp;
sp -= 4;
copyout(pgdir, sp, &argvaddr, 4);
// push argc
sp -= 4;
copyout(pgdir, sp, &argc, 4);
// push 0 in case main returns
sp -= 4;
uint ffffffff = 0xffffffff;
copyout(pgdir, sp, &ffffffff, 4);
// 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;
proc->tf->eip = elf.entry; // main
proc->tf->esp = sp;
switchuvm(proc);
freevm(oldpgdir);
return 0;
bad:
cprintf("kernel: exec failed\n");
if(pgdir) freevm(pgdir);
iunlockput(ip);
return -1;
}
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