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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 *mem, *s, *last;
int i, argc, arglen, len, off;
uint sz, sp, argp;
struct elfhdr elf;
struct inode *ip;
struct proghdr ph;
if((ip = namei(path)) == 0)
return -1;
ilock(ip);
// Compute memory size of new process.
mem = 0;
sz = 0;
// Program segments.
if(readi(ip, (char*)&elf, 0, sizeof(elf)) < sizeof(elf))
goto bad;
if(elf.magic != ELF_MAGIC)
goto bad;
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;
sz += ph.memsz;
}
// Arguments.
arglen = 0;
for(argc=0; argv[argc]; argc++)
arglen += strlen(argv[argc]) + 1;
arglen = (arglen+3) & ~3;
sz += arglen + 4*(argc+1);
// Stack.
sz += PAGE;
// Allocate program memory.
sz = (sz+PAGE-1) & ~(PAGE-1);
mem = kalloc(sz);
if(mem == 0)
goto bad;
memset(mem, 0, sz);
// 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.va + ph.memsz > sz)
goto bad;
if(readi(ip, mem + ph.va, ph.offset, ph.filesz) != ph.filesz)
goto bad;
memset(mem + ph.va + ph.filesz, 0, ph.memsz - ph.filesz);
}
iunlockput(ip);
// Initialize stack.
sp = sz;
argp = sz - arglen - 4*(argc+1);
// Copy argv strings and pointers to stack.
*(uint*)(mem+argp + 4*argc) = 0; // argv[argc]
for(i=argc-1; i>=0; i--){
len = strlen(argv[i]) + 1;
sp -= len;
memmove(mem+sp, argv[i], len);
*(uint*)(mem+argp + 4*i) = sp; // argv[i]
}
// Stack frame for main(argc, argv), below arguments.
sp = argp;
sp -= 4;
*(uint*)(mem+sp) = argp;
sp -= 4;
*(uint*)(mem+sp) = argc;
sp -= 4;
*(uint*)(mem+sp) = 0xffffffff; // fake return pc
// Save program name for debugging.
for(last=s=path; *s; s++)
if(*s == '/')
last = s+1;
safestrcpy(cp->name, last, sizeof(cp->name));
// Commit to the new image.
kfree(cp->mem, cp->sz);
cp->mem = mem;
cp->sz = sz;
cp->tf->eip = elf.entry; // main
cp->tf->esp = sp;
setupsegs(cp);
return 0;
bad:
if(mem)
kfree(mem, sz);
iunlockput(ip);
return -1;
}