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DEFINITIONS
This source file includes following definitions.
- exec
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
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
21 begin_op();
22 if((ip = namei(path)) == 0){
23 end_op();
24 return -1;
25 }
26 ilock(ip);
27 pgdir = 0;
28
29 // Check ELF header
30 if(readi(ip, (char*)&elf, 0, sizeof(elf)) < sizeof(elf))
31 goto bad;
32 if(elf.magic != ELF_MAGIC)
33 goto bad;
34
35 if((pgdir = setupkvm()) == 0)
36 goto bad;
37
38 // Load program into memory.
39 sz = 0;
40 for(i=0, off=elf.phoff; i<elf.phnum; i++, off+=sizeof(ph)){
41 if(readi(ip, (char*)&ph, off, sizeof(ph)) != sizeof(ph))
42 goto bad;
43 if(ph.type != ELF_PROG_LOAD)
44 continue;
45 if(ph.memsz < ph.filesz)
46 goto bad;
47 if((sz = allocuvm(pgdir, sz, ph.vaddr + ph.memsz)) == 0)
48 goto bad;
49 if(loaduvm(pgdir, (char*)ph.vaddr, ip, ph.off, ph.filesz) < 0)
50 goto bad;
51 }
52 iunlockput(ip);
53 end_op();
54 ip = 0;
55
56 // Allocate two pages at the next page boundary.
57 // Make the first inaccessible. Use the second as the user stack.
58 sz = PGROUNDUP(sz);
59 if((sz = allocuvm(pgdir, sz, sz + 2*PGSIZE)) == 0)
60 goto bad;
61 clearpteu(pgdir, (char*)(sz - 2*PGSIZE));
62 sp = sz;
63
64 // Push argument strings, prepare rest of stack in ustack.
65 for(argc = 0; argv[argc]; argc++) {
66 if(argc >= MAXARG)
67 goto bad;
68 sp = (sp - (strlen(argv[argc]) + 1)) & ~3;
69 if(copyout(pgdir, sp, argv[argc], strlen(argv[argc]) + 1) < 0)
70 goto bad;
71 ustack[3+argc] = sp;
72 }
73 ustack[3+argc] = 0;
74
75 ustack[0] = 0xffffffff; // fake return PC
76 ustack[1] = argc;
77 ustack[2] = sp - (argc+1)*4; // argv pointer
78
79 sp -= (3+argc+1) * 4;
80 if(copyout(pgdir, sp, ustack, (3+argc+1)*4) < 0)
81 goto bad;
82
83 // Save program name for debugging.
84 for(last=s=path; *s; s++)
85 if(*s == '/')
86 last = s+1;
87 safestrcpy(proc->name, last, sizeof(proc->name));
88
89 // Commit to the user image.
90 oldpgdir = proc->pgdir;
91 proc->pgdir = pgdir;
92 proc->sz = sz;
93 proc->tf->eip = elf.entry; // main
94 proc->tf->esp = sp;
95 switchuvm(proc);
96 freevm(oldpgdir);
97 return 0;
98
99 bad:
100 if(pgdir)
101 freevm(pgdir);
102 if(ip){
103 iunlockput(ip);
104 end_op();
105 }
106 return -1;
107 }