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0
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1 //
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2 // File-system system calls.
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3 // Mostly argument checking, since we don't trust
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4 // user code, and calls into file.c and fs.c.
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5 //
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6
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7 #include "types.h"
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8 #include "defs.h"
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9 #include "param.h"
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10 #include "stat.h"
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11 #include "mmu.h"
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12 #include "proc.h"
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13 #include "fs.h"
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14 #include "file.h"
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15 #include "fcntl.h"
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16
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17 // Fetch the nth word-sized system call argument as a file descriptor
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18 // and return both the descriptor and the corresponding struct file.
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19 static int argfd(int n, int *pfd, struct file **pf)
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20 {
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21 int fd;
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22 struct file *f;
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23
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24 if(argint(n, &fd) < 0) {
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25 return -1;
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26 }
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27
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28 if(fd < 0 || fd >= NOFILE || (f=proc->ofile[fd]) == 0) {
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29 return -1;
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30 }
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31
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32 if(pfd) {
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33 *pfd = fd;
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34 }
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35
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36 if(pf) {
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37 *pf = f;
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38 }
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39
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40 return 0;
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41 }
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42
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43 // Allocate a file descriptor for the given file.
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44 // Takes over file reference from caller on success.
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45 static int fdalloc(struct file *f)
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46 {
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47 int fd;
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48
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49 for(fd = 0; fd < NOFILE; fd++){
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50 if(proc->ofile[fd] == 0){
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51 proc->ofile[fd] = f;
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52 return fd;
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53 }
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54 }
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55
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56 return -1;
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57 }
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58
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59 int sys_dup(void)
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60 {
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61 struct file *f;
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62 int fd;
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63
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64 if(argfd(0, 0, &f) < 0) {
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65 return -1;
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66 }
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67
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68 if((fd=fdalloc(f)) < 0) {
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69 return -1;
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70 }
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71
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72 filedup(f);
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73
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74 return fd;
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75 }
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76
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77 int sys_read(void)
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78 {
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79 struct file *f;
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80 int n;
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81 char *p;
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82
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83 if(argfd(0, 0, &f) < 0 || argint(2, &n) < 0 || argptr(1, &p, n) < 0) {
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84 return -1;
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85 }
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86
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87 return fileread(f, p, n);
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88 }
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89
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90 int sys_write(void)
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91 {
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92 struct file *f;
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93 int n;
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94 char *p;
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95
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96 if(argfd(0, 0, &f) < 0 || argint(2, &n) < 0 || argptr(1, &p, n) < 0) {
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97 return -1;
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98 }
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99
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100 return filewrite(f, p, n);
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101 }
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102
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103 int sys_close(void)
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104 {
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105 int fd;
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106 struct file *f;
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107
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108 if(argfd(0, &fd, &f) < 0) {
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109 return -1;
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110 }
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111
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112 proc->ofile[fd] = 0;
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113 fileclose(f);
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114
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115 return 0;
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116 }
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117
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118 int sys_fstat(void)
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119 {
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120 struct file *f;
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121 struct stat *st;
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122
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123 if(argfd(0, 0, &f) < 0 || argptr(1, (void*)&st, sizeof(*st)) < 0) {
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124 return -1;
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125 }
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126
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127 return filestat(f, st);
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128 }
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129
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130 // Create the path new as a link to the same inode as old.
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131 int sys_link(void)
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132 {
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133 char name[DIRSIZ], *new, *old;
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134 struct inode *dp, *ip;
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135
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136 if(argstr(0, &old) < 0 || argstr(1, &new) < 0) {
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137 return -1;
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138 }
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139
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140 if((ip = namei(old)) == 0) {
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141 return -1;
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142 }
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143
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144 begin_trans();
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145
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146 ilock(ip);
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147
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148 if(ip->type == T_DIR){
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149 iunlockput(ip);
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150 commit_trans();
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151 return -1;
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152 }
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153
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154 ip->nlink++;
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155 iupdate(ip);
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156 iunlock(ip);
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157
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158 if((dp = nameiparent(new, name)) == 0) {
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159 goto bad;
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160 }
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161
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162 ilock(dp);
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163
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164 if(dp->dev != ip->dev || dirlink(dp, name, ip->inum) < 0){
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165 iunlockput(dp);
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166 goto bad;
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167 }
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168
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169 iunlockput(dp);
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170 iput(ip);
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171
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172 commit_trans();
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173
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174 return 0;
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175
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176 bad:
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177 ilock(ip);
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178 ip->nlink--;
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179 iupdate(ip);
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180 iunlockput(ip);
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181 commit_trans();
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182 return -1;
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183 }
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184
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185 // Is the directory dp empty except for "." and ".." ?
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186 static int isdirempty(struct inode *dp)
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187 {
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188 int off;
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189 struct dirent de;
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190
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191 for(off=2*sizeof(de); off<dp->size; off+=sizeof(de)){
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192 if(readi(dp, (char*)&de, off, sizeof(de)) != sizeof(de)) {
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193 panic("isdirempty: readi");
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194 }
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195
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196 if(de.inum != 0) {
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197 return 0;
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198 }
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199 }
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200 return 1;
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201 }
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202
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203 //PAGEBREAK!
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204 int sys_unlink(void)
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205 {
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206 struct inode *ip, *dp;
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207 struct dirent de;
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208 char name[DIRSIZ], *path;
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209 uint off;
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210
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211 if(argstr(0, &path) < 0) {
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212 return -1;
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213 }
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214
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215 if((dp = nameiparent(path, name)) == 0) {
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216 return -1;
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217 }
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218
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219 begin_trans();
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220
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221 ilock(dp);
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222
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223 // Cannot unlink "." or "..".
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224 if(namecmp(name, ".") == 0 || namecmp(name, "..") == 0) {
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225 goto bad;
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226 }
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227
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228 if((ip = dirlookup(dp, name, &off)) == 0) {
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229 goto bad;
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230 }
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231
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232 ilock(ip);
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233
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234 if(ip->nlink < 1) {
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235 panic("unlink: nlink < 1");
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236 }
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237
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238 if(ip->type == T_DIR && !isdirempty(ip)){
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239 iunlockput(ip);
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240 goto bad;
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241 }
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242
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243 memset(&de, 0, sizeof(de));
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244
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245 if(writei(dp, (char*)&de, off, sizeof(de)) != sizeof(de)) {
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246 panic("unlink: writei");
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247 }
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248
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249 if(ip->type == T_DIR){
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250 dp->nlink--;
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251 iupdate(dp);
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252 }
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253
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254 iunlockput(dp);
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255
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256 ip->nlink--;
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257 iupdate(ip);
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258 iunlockput(ip);
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259
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260 commit_trans();
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261
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262 return 0;
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263
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264 bad:
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265 iunlockput(dp);
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266 commit_trans();
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267 return -1;
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268 }
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269
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270 static struct inode* create(char *path, short type, short major, short minor)
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271 {
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272 uint off;
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273 struct inode *ip, *dp;
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274 char name[DIRSIZ];
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275
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276 if((dp = nameiparent(path, name)) == 0) {
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277 return 0;
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278 }
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279
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280 ilock(dp);
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281
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282 if((ip = dirlookup(dp, name, &off)) != 0){
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283 iunlockput(dp);
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284 ilock(ip);
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285
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286 if(type == T_FILE && ip->type == T_FILE) {
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287 return ip;
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288 }
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289
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290 iunlockput(ip);
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291
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292 return 0;
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293 }
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294
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295 if((ip = ialloc(dp->dev, type)) == 0) {
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296 panic("create: ialloc");
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297 }
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298
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299 ilock(ip);
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300 ip->major = major;
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301 ip->minor = minor;
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302 ip->nlink = 1;
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303 iupdate(ip);
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304
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305 if(type == T_DIR){ // Create . and .. entries.
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306 dp->nlink++; // for ".."
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307 iupdate(dp);
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308
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309 // No ip->nlink++ for ".": avoid cyclic ref count.
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310 if(dirlink(ip, ".", ip->inum) < 0 || dirlink(ip, "..", dp->inum) < 0) {
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311 panic("create dots");
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312 }
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313 }
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314
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315 if(dirlink(dp, name, ip->inum) < 0) {
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316 panic("create: dirlink");
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317 }
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318
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319 iunlockput(dp);
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320
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321 return ip;
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322 }
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323
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324 int sys_open(void)
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325 {
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326 char *path;
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327 int fd, omode;
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328 struct file *f;
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329 struct inode *ip;
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330
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331 if(argstr(0, &path) < 0 || argint(1, &omode) < 0) {
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332 return -1;
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333 }
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334
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335 if(omode & O_CREATE){
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336 begin_trans();
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337 ip = create(path, T_FILE, 0, 0);
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338 commit_trans();
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339
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340 if(ip == 0) {
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341 return -1;
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342 }
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343
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344 } else {
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345 if((ip = namei(path)) == 0) {
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346 return -1;
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347 }
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348
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349 ilock(ip);
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350
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351 if(ip->type == T_DIR && omode != O_RDONLY){
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352 iunlockput(ip);
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353 return -1;
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354 }
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355 }
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356
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357 if((f = filealloc()) == 0 || (fd = fdalloc(f)) < 0){
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358 if(f) {
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359 fileclose(f);
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360 }
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361
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362 iunlockput(ip);
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363 return -1;
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364 }
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365
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366 iunlock(ip);
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367
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368 f->type = FD_INODE;
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369 f->ip = ip;
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370 f->off = 0;
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371 f->readable = !(omode & O_WRONLY);
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372 f->writable = (omode & O_WRONLY) || (omode & O_RDWR);
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373
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374 return fd;
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375 }
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376
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377 int sys_mkdir(void)
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378 {
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379 char *path;
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380 struct inode *ip;
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381
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382 begin_trans();
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383
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384 if(argstr(0, &path) < 0 || (ip = create(path, T_DIR, 0, 0)) == 0){
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385 commit_trans();
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386 return -1;
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387 }
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388
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389 iunlockput(ip);
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390 commit_trans();
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391
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392 return 0;
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393 }
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394
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395 int sys_mknod(void)
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396 {
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397 struct inode *ip;
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398 char *path;
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399 int len;
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400 int major, minor;
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401
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402 begin_trans();
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403
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404 if((len=argstr(0, &path)) < 0 ||
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405 argint(1, &major) < 0 || argint(2, &minor) < 0 ||
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406 (ip = create(path, T_DEV, major, minor)) == 0){
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407
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408 commit_trans();
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409 return -1;
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410 }
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411
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412 iunlockput(ip);
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413 commit_trans();
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414
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415 return 0;
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416 }
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417
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418 int sys_chdir(void)
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419 {
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420 char *path;
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421 struct inode *ip;
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422
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423 if(argstr(0, &path) < 0 || (ip = namei(path)) == 0) {
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424 return -1;
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425 }
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426
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427 ilock(ip);
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428
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429 if(ip->type != T_DIR){
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430 iunlockput(ip);
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431 return -1;
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432 }
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433
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434 iunlock(ip);
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435
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436 iput(proc->cwd);
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437 proc->cwd = ip;
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438
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439 return 0;
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440 }
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441
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442 int sys_exec(void)
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443 {
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444 char *path, *argv[MAXARG];
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445 int i;
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446 uint uargv, uarg;
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447
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448 if(argstr(0, &path) < 0 || argint(1, (int*)&uargv) < 0){
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449 return -1;
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450 }
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451
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452 memset(argv, 0, sizeof(argv));
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453
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454 for(i=0;; i++){
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455 if(i >= NELEM(argv)) {
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456 return -1;
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457 }
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458
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459 if(fetchint(uargv+4*i, (int*)&uarg) < 0) {
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460 return -1;
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461 }
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462
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463 if(uarg == 0){
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464 argv[i] = 0;
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465 break;
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466 }
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467
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468 if(fetchstr(uarg, &argv[i]) < 0) {
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469 return -1;
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470 }
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471 }
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472
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473 return exec(path, argv);
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474 }
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475
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476 int sys_pipe(void)
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477 {
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478 int *fd;
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479 struct file *rf, *wf;
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480 int fd0, fd1;
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481
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482 if(argptr(0, (void*)&fd, 2*sizeof(fd[0])) < 0) {
|
|
|
483 return -1;
|
|
|
484 }
|
|
|
485
|
|
|
486 if(pipealloc(&rf, &wf) < 0) {
|
|
|
487 return -1;
|
|
|
488 }
|
|
|
489
|
|
|
490 fd0 = -1;
|
|
|
491
|
|
|
492 if((fd0 = fdalloc(rf)) < 0 || (fd1 = fdalloc(wf)) < 0){
|
|
|
493 if(fd0 >= 0) {
|
|
|
494 proc->ofile[fd0] = 0;
|
|
|
495 }
|
|
|
496
|
|
|
497 fileclose(rf);
|
|
|
498 fileclose(wf);
|
|
|
499
|
|
|
500 return -1;
|
|
|
501 }
|
|
|
502
|
|
|
503 fd[0] = fd0;
|
|
|
504 fd[1] = fd1;
|
|
|
505
|
|
|
506 return 0;
|
|
|
507 }
|
