1 #include "types.h"
2 #include "param.h"
3 #include "memlayout.h"
4 #include "mmu.h"
5 #include "proc.h"
6 #include "defs.h"
7 #include "x86.h"
8 #include "elf.h"
9
10 int
exec(char * path,char ** argv)11 exec(char *path, char **argv)
12 {
13 char *s, *last;
14 int i, off;
15 uint argc, sz, sp, ustack[3+MAXARG+1];
16 struct elfhdr elf;
17 struct inode *ip;
18 struct proghdr ph;
19 pde_t *pgdir, *oldpgdir;
20 struct proc *curproc = myproc();
21
22 begin_op();
23
24 if((ip = namei(path)) == 0){
25 end_op();
26 cprintf("exec: fail\n");
27 return -1;
28 }
29 ilock(ip);
30 pgdir = 0;
31
32 // Check ELF header
33 if(readi(ip, (char*)&elf, 0, sizeof(elf)) != sizeof(elf))
34 goto bad;
35 if(elf.magic != ELF_MAGIC)
36 goto bad;
37
38 if((pgdir = setupkvm()) == 0)
39 goto bad;
40
41 // Load program into memory.
42 sz = 0;
43 for(i=0, off=elf.phoff; i<elf.phnum; i++, off+=sizeof(ph)){
44 if(readi(ip, (char*)&ph, off, sizeof(ph)) != sizeof(ph))
45 goto bad;
46 if(ph.type != ELF_PROG_LOAD)
47 continue;
48 if(ph.memsz < ph.filesz)
49 goto bad;
50 if(ph.vaddr + ph.memsz < ph.vaddr)
51 goto bad;
52 if((sz = allocuvm(pgdir, sz, ph.vaddr + ph.memsz)) == 0)
53 goto bad;
54 if(ph.vaddr % PGSIZE != 0)
55 goto bad;
56 if(loaduvm(pgdir, (char*)ph.vaddr, ip, ph.off, ph.filesz) < 0)
57 goto bad;
58 }
59 iunlockput(ip);
60 end_op();
61 ip = 0;
62
63 // Allocate two pages at the next page boundary.
64 // Make the first inaccessible. Use the second as the user stack.
65 sz = PGROUNDUP(sz);
66 if((sz = allocuvm(pgdir, sz, sz + 2*PGSIZE)) == 0)
67 goto bad;
68 clearpteu(pgdir, (char*)(sz - 2*PGSIZE));
69 sp = sz;
70
71 // Push argument strings, prepare rest of stack in ustack.
72 for(argc = 0; argv[argc]; argc++) {
73 if(argc >= MAXARG)
74 goto bad;
75 sp = (sp - (strlen(argv[argc]) + 1)) & ~3;
76 if(copyout(pgdir, sp, argv[argc], strlen(argv[argc]) + 1) < 0)
77 goto bad;
78 ustack[3+argc] = sp;
79 }
80 ustack[3+argc] = 0;
81
82 ustack[0] = 0xffffffff; // fake return PC
83 ustack[1] = argc;
84 ustack[2] = sp - (argc+1)*4; // argv pointer
85
86 sp -= (3+argc+1) * 4;
87 if(copyout(pgdir, sp, ustack, (3+argc+1)*4) < 0)
88 goto bad;
89
90 // Save program name for debugging.
91 for(last=s=path; *s; s++)
92 if(*s == '/')
93 last = s+1;
94 safestrcpy(curproc->name, last, sizeof(curproc->name));
95
96 // Commit to the user image.
97 oldpgdir = curproc->pgdir;
98 curproc->pgdir = pgdir;
99 curproc->sz = sz;
100 curproc->tf->eip = elf.entry; // main
101 curproc->tf->esp = sp;
102 switchuvm(curproc);
103 freevm(oldpgdir);
104 return 0;
105
106 bad:
107 if(pgdir)
108 freevm(pgdir);
109 if(ip){
110 iunlockput(ip);
111 end_op();
112 }
113 return -1;
114 }
115