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exec.c
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exec.c
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#include "types.h"
#include "param.h"
#include "memlayout.h"
#include "mmu.h"
#include "proc.h"
#include "defs.h"
#include "x86.h"
#include "elf.h"
void pseudo_main(int (*entry)(int, char**), int argc, char **argv) {
(*entry)(argc,argv);
__asm__ ("push %eax \n\t"
"push $0 \n\t"
"movl $2, %eax \n\t"
"int $64");
}
int exec(char *path, char **argv) {
char *s, *last;
int i, off;
uint argc, sz, sp, ustack[3+MAXARG+1];
uint pointer_pseudo_main;
struct elfhdr elf;
struct inode *ip;
struct proghdr ph;
pde_t *pgdir, *oldpgdir;
begin_op();
if((ip = namei(path)) == 0){
end_op();
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()) == 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)) != 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;
pointer_pseudo_main = sz;
// 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 + 3*PGSIZE)) == 0)
goto bad;
clearpteu(pgdir, (char*)(sz - 2*PGSIZE));
if (copyout(pgdir, pointer_pseudo_main, pseudo_main, (uint)exec - (uint)pseudo_main) < 0)
goto bad;
sp = sz;
// Push argument strings, prepare rest of stack in ustack.
//////////added code////////// args: entry,argc,argv
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[4+argc] = sp;
}
ustack[4+argc] = 0;
ustack[0] = 0xffffffff; // fake return PC
ustack[1] = elf.entry;
ustack[2] = argc;
ustack[3] = sp - (argc+1)*4; //argv of original main
sp -= (4+argc+1) * 4;
if(copyout(pgdir, sp, ustack, (4+argc+1)*4) < 0)
goto bad;
//////////added code//////////
// 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 = pointer_pseudo_main; // main
proc->tf->esp = sp;
switchuvm(proc);
freevm(oldpgdir);
return 0;
bad:
if(pgdir)
freevm(pgdir);
if(ip){
iunlockput(ip);
end_op();
}
return -1;
}