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(ph.vaddr % PGSIZE != 0) 50 goto bad; 51 if(loaduvm(pgdir, (char*)ph.vaddr, ip, ph.off, ph.filesz) < 0) 52 goto bad; 53 } 54 iunlockput(ip); 55 end_op(); 56 ip = 0; 57 58 // Allocate two pages at the next page boundary. 59 // Make the first inaccessible. Use the second as the user stack. 60 sz = PGROUNDUP(sz); 61 if((sz = allocuvm(pgdir, sz, sz + 2*PGSIZE)) == 0) 62 goto bad; 63 clearpteu(pgdir, (char*)(sz - 2*PGSIZE)); 64 sp = sz; 65 66 // Push argument strings, prepare rest of stack in ustack. 67 for(argc = 0; argv[argc]; argc++) { 68 if(argc >= MAXARG) 69 goto bad; 70 sp = (sp - (strlen(argv[argc]) + 1)) & ~3; 71 if(copyout(pgdir, sp, argv[argc], strlen(argv[argc]) + 1) < 0) 72 goto bad; 73 ustack[3+argc] = sp; 74 } 75 ustack[3+argc] = 0; 76 77 ustack[0] = 0xffffffff; // fake return PC 78 ustack[1] = argc; 79 ustack[2] = sp - (argc+1)*4; // argv pointer 80 81 sp -= (3+argc+1) * 4; 82 if(copyout(pgdir, sp, ustack, (3+argc+1)*4) < 0) 83 goto bad; 84 85 // Save program name for debugging. 86 for(last=s=path; *s; s++) 87 if(*s == '/') 88 last = s+1; 89 safestrcpy(proc->name, last, sizeof(proc->name)); 90 91 // Commit to the user image. 92 oldpgdir = proc->pgdir; 93 proc->pgdir = pgdir; 94 proc->sz = sz; 95 proc->tf->eip = elf.entry; // main 96 proc->tf->esp = sp; 97 switchuvm(proc); 98 freevm(oldpgdir); 99 return 0; 100 101 bad: 102 if(pgdir) 103 freevm(pgdir); 104 if(ip){ 105 iunlockput(ip); 106 end_op(); 107 } 108 return -1; 109 } 110