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