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