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