1 #include "types.h" 2 #include "param.h" 3 #include "mmu.h" 4 #include "proc.h" 5 #include "defs.h" 6 #include "x86.h" 7 #include "elf.h" 8 9 int 10 exec(char *path, char **argv) 11 { 12 char *s, *last; 13 int i, off; 14 uint sz = 0; 15 struct elfhdr elf; 16 struct inode *ip = 0; 17 struct proghdr ph; 18 pde_t *pgdir = 0, *oldpgdir; 19 20 if((ip = namei(path)) == 0) 21 return -1; 22 ilock(ip); 23 24 // Check ELF header 25 if(readi(ip, (char*)&elf, 0, sizeof(elf)) < sizeof(elf)) 26 goto bad; 27 if(elf.magic != ELF_MAGIC) 28 goto bad; 29 30 if(!(pgdir = setupkvm())) 31 goto bad; 32 33 // Load program into memory. 34 for(i=0, off=elf.phoff; i<elf.phnum; i++, off+=sizeof(ph)){ 35 if(readi(ip, (char*)&ph, off, sizeof(ph)) != sizeof(ph)) 36 goto bad; 37 if(ph.type != ELF_PROG_LOAD) 38 continue; 39 if(ph.memsz < ph.filesz) 40 goto bad; 41 if(!(sz = allocuvm(pgdir, sz, ph.va + ph.memsz))) 42 goto bad; 43 if(!loaduvm(pgdir, (char *)ph.va, ip, ph.offset, ph.filesz)) 44 goto bad; 45 } 46 iunlockput(ip); 47 ip = 0; 48 49 // Allocate a one-page stack at the next page boundary 50 sz = PGROUNDUP(sz); 51 if(!(sz = allocuvm(pgdir, sz, sz + PGSIZE))) 52 goto bad; 53 54 // initialize stack content: 55 56 // "argumentN" -- nul-terminated string 57 // ... 58 // "argument0" 59 // 0 -- argv[argc] 60 // address of argumentN 61 // ... 62 // address of argument0 -- argv[0] 63 // address of address of argument0 -- argv argument to main() 64 // argc -- argc argument to main() 65 // ffffffff -- return PC for main() call 66 67 uint sp = sz; 68 69 // count arguments 70 int argc; 71 for(argc = 0; argv[argc]; argc++) 72 ; 73 if(argc >= MAXARG) 74 goto bad; 75 76 // push strings and remember where they are 77 uint strings[MAXARG]; 78 for(i = argc - 1; i >= 0; --i){ 79 sp -= strlen(argv[i]) + 1; 80 strings[i] = sp; 81 copyout(pgdir, sp, argv[i], strlen(argv[i]) + 1); 82 } 83 84 // push 0 for argv[argc] 85 sp -= 4; 86 int zero = 0; 87 copyout(pgdir, sp, &zero, 4); 88 89 // push argv[] elements 90 for(i = argc - 1; i >= 0; --i){ 91 sp -= 4; 92 copyout(pgdir, sp, &strings[i], 4); 93 } 94 95 // push argv 96 uint argvaddr = sp; 97 sp -= 4; 98 copyout(pgdir, sp, &argvaddr, 4); 99 100 // push argc 101 sp -= 4; 102 copyout(pgdir, sp, &argc, 4); 103 104 // push 0 in case main returns 105 sp -= 4; 106 uint ffffffff = 0xffffffff; 107 copyout(pgdir, sp, &ffffffff, 4); 108 109 if(sp < sz - PGSIZE) 110 goto bad; 111 112 // Save program name for debugging. 113 for(last=s=path; *s; s++) 114 if(*s == '/') 115 last = s+1; 116 safestrcpy(proc->name, last, sizeof(proc->name)); 117 118 // Commit to the user image. 119 oldpgdir = proc->pgdir; 120 proc->pgdir = pgdir; 121 proc->sz = sz; 122 proc->tf->eip = elf.entry; // main 123 proc->tf->esp = sp; 124 125 switchuvm(proc); 126 127 freevm(oldpgdir); 128 129 return 0; 130 131 bad: 132 if(pgdir) 133 freevm(pgdir); 134 if(ip) 135 iunlockput(ip); 136 return -1; 137 } 138