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1 #include "types.h"
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2 #include "param.h"
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3 #include "defs.h"
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4 #include "memlayout.h"
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5 #include "mmu.h"
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6 #include "proc.h"
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7 #include "elf.h"
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8 #include "arm.h"
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9
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10 // load a user program for execution
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11 int exec (char *path, char **argv)
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12 {
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13 struct elfhdr elf;
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14 struct inode *ip;
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15 struct proghdr ph;
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16 pde_t *pgdir;
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17 pde_t *oldpgdir;
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18 char *s;
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19 char *last;
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20 int i;
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21 int off;
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22 uint argc;
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23 uint sz;
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24 uint sp;
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25 uint ustack[3 + MAXARG + 1];
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26
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27 if ((ip = namei(path)) == 0) {
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28 return -1;
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29 }
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30
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31 ilock(ip);
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32
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33 // Check ELF header
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34 if (readi(ip, (char*) &elf, 0, sizeof(elf)) < sizeof(elf)) {
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35 goto bad;
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36 }
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37
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38 if (elf.magic != ELF_MAGIC) {
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39 goto bad;
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40 }
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41
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42 pgdir = 0;
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43
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44 if ((pgdir = kpt_alloc()) == 0) {
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45 goto bad;
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46 }
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47
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48 // Load program into memory.
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49 sz = 0;
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50
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51 for (i = 0, off = elf.phoff; i < elf.phnum; i++, off += sizeof(ph)) {
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52 if (readi(ip, (char*) &ph, off, sizeof(ph)) != sizeof(ph)) {
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53 goto bad;
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54 }
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55
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56 if (ph.type != ELF_PROG_LOAD) {
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57 continue;
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58 }
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59
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60 if (ph.memsz < ph.filesz) {
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61 goto bad;
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62 }
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63
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64 if ((sz = allocuvm(pgdir, sz, ph.vaddr + ph.memsz)) == 0) {
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65 goto bad;
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66 }
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67
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68 if (loaduvm(pgdir, (char*) ph.vaddr, ip, ph.off, ph.filesz) < 0) {
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69 goto bad;
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70 }
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71 }
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72
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73 iunlockput(ip);
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74 ip = 0;
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75
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76 // Allocate two pages at the next page boundary.
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77 // Make the first inaccessible. Use the second as the user stack.
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78 sz = align_up (sz, PTE_SZ);
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79
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80 if ((sz = allocuvm(pgdir, sz, sz + 2 * PTE_SZ)) == 0) {
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81 goto bad;
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82 }
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83
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84 clearpteu(pgdir, (char*) (sz - 2 * PTE_SZ));
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85
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86 sp = sz;
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87
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88 // Push argument strings, prepare rest of stack in ustack.
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89 for (argc = 0; argv[argc]; argc++) {
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90 if (argc >= MAXARG) {
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91 goto bad;
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92 }
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93
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94 sp = (sp - (strlen(argv[argc]) + 1)) & ~3;
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95
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96 if (copyout(pgdir, sp, argv[argc], strlen(argv[argc]) + 1) < 0) {
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97 goto bad;
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98 }
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99
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100 ustack[argc] = sp;
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101 }
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102
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103 ustack[argc] = 0;
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104
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105 // in ARM, parameters are passed in r0 and r1
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106 proc->tf->r0 = argc;
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107 proc->tf->r1 = sp - (argc + 1) * 4;
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108
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109 sp -= (argc + 1) * 4;
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110
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111 if (copyout(pgdir, sp, ustack, (argc + 1) * 4) < 0) {
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112 goto bad;
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113 }
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114
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115 // Save program name for debugging.
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116 for (last = s = path; *s; s++) {
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117 if (*s == '/') {
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118 last = s + 1;
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119 }
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120 }
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121
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122 safestrcpy(proc->name, last, sizeof(proc->name));
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123
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124 // Commit to the user image.
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125 oldpgdir = proc->pgdir;
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126 proc->pgdir = pgdir;
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127 proc->sz = sz;
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128 proc->tf->pc = elf.entry;
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129 proc->tf->sp_usr = sp;
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130
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131 switchuvm(proc);
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132 freevm(oldpgdir);
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133 return 0;
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134
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135 bad: if (pgdir) {
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136 freevm(pgdir);
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137 }
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138
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139 if (ip) {
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140 iunlockput(ip);
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141 }
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142 return -1;
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143 }
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