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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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52
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17 #define __ncode __code
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18
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0
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19 // Fetch the nth word-sized system call argument as a file descriptor
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20 // and return both the descriptor and the corresponding struct file.
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21 static int argfd(int n, int *pfd, struct file **pf)
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22 {
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23 int fd;
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24 struct file *f;
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25
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26 if(argint(n, &fd) < 0) {
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27 return -1;
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28 }
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29
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30 if(fd < 0 || fd >= NOFILE || (f=proc->ofile[fd]) == 0) {
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31 return -1;
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32 }
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33
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34 if(pfd) {
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35 *pfd = fd;
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36 }
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37
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38 if(pf) {
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39 *pf = f;
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40 }
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41
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42 return 0;
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43 }
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44
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45 // Allocate a file descriptor for the given file.
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46 // Takes over file reference from caller on success.
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47 static int fdalloc(struct file *f)
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48 {
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49 int fd;
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50
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51 for(fd = 0; fd < NOFILE; fd++){
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52 if(proc->ofile[fd] == 0){
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53 proc->ofile[fd] = f;
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54 return fd;
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55 }
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56 }
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57
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58 return -1;
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59 }
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60
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61 int sys_dup(void)
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62 {
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63 struct file *f;
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64 int fd;
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65
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66 if(argfd(0, 0, &f) < 0) {
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67 return -1;
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68 }
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69
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70 if((fd=fdalloc(f)) < 0) {
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71 return -1;
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72 }
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73
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74 filedup(f);
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75
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76 return fd;
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77 }
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78
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52
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79 __ncode cbc_read(__code (*next)(int ret)){
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24
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80 struct file *f;
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81 int n;
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82 char *p;
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83
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84 if(argfd(0, 0, &f) < 0 || argint(2, &n) < 0 || argptr(1, &p, n) < 0) {
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85 goto next(-1);
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86 }
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87 goto cbc_fileread(f, p, n, next);
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88 }
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89
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0
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90 int sys_read(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 fileread(f, p, n);
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101 }
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102
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103 int sys_write(void)
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104 {
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105 struct file *f;
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106 int n;
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107 char *p;
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108
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109 if(argfd(0, 0, &f) < 0 || argint(2, &n) < 0 || argptr(1, &p, n) < 0) {
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110 return -1;
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111 }
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112
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113 return filewrite(f, p, n);
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114 }
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115
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116 int sys_close(void)
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117 {
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118 int fd;
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119 struct file *f;
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120
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121 if(argfd(0, &fd, &f) < 0) {
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122 return -1;
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123 }
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124
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125 proc->ofile[fd] = 0;
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126 fileclose(f);
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127
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128 return 0;
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129 }
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130
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131 int sys_fstat(void)
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132 {
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133 struct file *f;
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134 struct stat *st;
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135
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136 if(argfd(0, 0, &f) < 0 || argptr(1, (void*)&st, sizeof(*st)) < 0) {
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137 return -1;
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138 }
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139
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140 return filestat(f, st);
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141 }
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142
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143 // Create the path new as a link to the same inode as old.
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144 int sys_link(void)
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145 {
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146 char name[DIRSIZ], *new, *old;
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147 struct inode *dp, *ip;
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148
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149 if(argstr(0, &old) < 0 || argstr(1, &new) < 0) {
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150 return -1;
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151 }
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152
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153 if((ip = namei(old)) == 0) {
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154 return -1;
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155 }
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156
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157 begin_trans();
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158
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159 ilock(ip);
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160
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161 if(ip->type == T_DIR){
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162 iunlockput(ip);
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163 commit_trans();
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164 return -1;
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165 }
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166
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167 ip->nlink++;
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168 iupdate(ip);
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169 iunlock(ip);
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170
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171 if((dp = nameiparent(new, name)) == 0) {
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172 goto bad;
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173 }
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174
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175 ilock(dp);
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176
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177 if(dp->dev != ip->dev || dirlink(dp, name, ip->inum) < 0){
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178 iunlockput(dp);
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179 goto bad;
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180 }
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181
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182 iunlockput(dp);
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183 iput(ip);
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184
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185 commit_trans();
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186
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187 return 0;
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188
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189 bad:
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190 ilock(ip);
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191 ip->nlink--;
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192 iupdate(ip);
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193 iunlockput(ip);
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194 commit_trans();
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195 return -1;
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196 }
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197
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198 // Is the directory dp empty except for "." and ".." ?
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199 static int isdirempty(struct inode *dp)
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200 {
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201 int off;
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202 struct dirent de;
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203
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204 for(off=2*sizeof(de); off<dp->size; off+=sizeof(de)){
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205 if(readi(dp, (char*)&de, off, sizeof(de)) != sizeof(de)) {
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206 panic("isdirempty: readi");
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207 }
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208
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209 if(de.inum != 0) {
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210 return 0;
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211 }
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212 }
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213 return 1;
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214 }
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215
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216 //PAGEBREAK!
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217 int sys_unlink(void)
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218 {
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219 struct inode *ip, *dp;
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220 struct dirent de;
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221 char name[DIRSIZ], *path;
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222 uint off;
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223
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224 if(argstr(0, &path) < 0) {
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225 return -1;
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226 }
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227
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228 if((dp = nameiparent(path, name)) == 0) {
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229 return -1;
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230 }
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231
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232 begin_trans();
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233
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234 ilock(dp);
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235
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236 // Cannot unlink "." or "..".
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237 if(namecmp(name, ".") == 0 || namecmp(name, "..") == 0) {
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238 goto bad;
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239 }
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240
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241 if((ip = dirlookup(dp, name, &off)) == 0) {
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242 goto bad;
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243 }
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244
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245 ilock(ip);
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246
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247 if(ip->nlink < 1) {
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248 panic("unlink: nlink < 1");
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249 }
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250
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251 if(ip->type == T_DIR && !isdirempty(ip)){
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252 iunlockput(ip);
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253 goto bad;
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254 }
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255
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256 memset(&de, 0, sizeof(de));
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257
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258 if(writei(dp, (char*)&de, off, sizeof(de)) != sizeof(de)) {
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259 panic("unlink: writei");
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260 }
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261
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262 if(ip->type == T_DIR){
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263 dp->nlink--;
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264 iupdate(dp);
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265 }
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266
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267 iunlockput(dp);
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268
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269 ip->nlink--;
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270 iupdate(ip);
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271 iunlockput(ip);
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272
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273 commit_trans();
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274
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275 return 0;
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276
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277 bad:
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278 iunlockput(dp);
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279 commit_trans();
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280 return -1;
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281 }
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282
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283 static struct inode* create(char *path, short type, short major, short minor)
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284 {
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285 uint off;
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286 struct inode *ip, *dp;
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287 char name[DIRSIZ];
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288
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289 if((dp = nameiparent(path, name)) == 0) {
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290 return 0;
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291 }
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292
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293 ilock(dp);
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294
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295 if((ip = dirlookup(dp, name, &off)) != 0){
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296 iunlockput(dp);
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297 ilock(ip);
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298
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299 if(type == T_FILE && ip->type == T_FILE) {
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300 return ip;
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301 }
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302
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303 iunlockput(ip);
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304
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305 return 0;
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306 }
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307
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308 if((ip = ialloc(dp->dev, type)) == 0) {
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309 panic("create: ialloc");
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310 }
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311
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312 ilock(ip);
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313 ip->major = major;
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314 ip->minor = minor;
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315 ip->nlink = 1;
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316 iupdate(ip);
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317
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318 if(type == T_DIR){ // Create . and .. entries.
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319 dp->nlink++; // for ".."
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320 iupdate(dp);
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321
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322 // No ip->nlink++ for ".": avoid cyclic ref count.
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323 if(dirlink(ip, ".", ip->inum) < 0 || dirlink(ip, "..", dp->inum) < 0) {
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324 panic("create dots");
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325 }
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326 }
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327
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328 if(dirlink(dp, name, ip->inum) < 0) {
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329 panic("create: dirlink");
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330 }
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331
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332 iunlockput(dp);
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333
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334 return ip;
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335 }
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336
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337 int sys_open(void)
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338 {
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339 char *path;
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340 int fd, omode;
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341 struct file *f;
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342 struct inode *ip;
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343
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344 if(argstr(0, &path) < 0 || argint(1, &omode) < 0) {
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345 return -1;
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346 }
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347
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348 if(omode & O_CREATE){
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349 begin_trans();
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350 ip = create(path, T_FILE, 0, 0);
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351 commit_trans();
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352
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353 if(ip == 0) {
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354 return -1;
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355 }
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356
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357 } else {
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358 if((ip = namei(path)) == 0) {
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359 return -1;
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360 }
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361
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362 ilock(ip);
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363
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364 if(ip->type == T_DIR && omode != O_RDONLY){
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365 iunlockput(ip);
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366 return -1;
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367 }
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368 }
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369
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370 if((f = filealloc()) == 0 || (fd = fdalloc(f)) < 0){
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371 if(f) {
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372 fileclose(f);
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373 }
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374
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375 iunlockput(ip);
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376 return -1;
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377 }
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378
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379 iunlock(ip);
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380
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381 f->type = FD_INODE;
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382 f->ip = ip;
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383 f->off = 0;
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384 f->readable = !(omode & O_WRONLY);
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385 f->writable = (omode & O_WRONLY) || (omode & O_RDWR);
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386
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387 return fd;
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388 }
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389
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390 int sys_mkdir(void)
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391 {
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392 char *path;
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393 struct inode *ip;
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394
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395 begin_trans();
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396
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397 if(argstr(0, &path) < 0 || (ip = create(path, T_DIR, 0, 0)) == 0){
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398 commit_trans();
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399 return -1;
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400 }
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401
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402 iunlockput(ip);
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403 commit_trans();
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404
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405 return 0;
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406 }
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407
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408 int sys_mknod(void)
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409 {
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410 struct inode *ip;
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411 char *path;
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412 int len;
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413 int major, minor;
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414
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415 begin_trans();
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416
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417 if((len=argstr(0, &path)) < 0 ||
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418 argint(1, &major) < 0 || argint(2, &minor) < 0 ||
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419 (ip = create(path, T_DEV, major, minor)) == 0){
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420
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421 commit_trans();
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422 return -1;
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423 }
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424
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425 iunlockput(ip);
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426 commit_trans();
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427
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428 return 0;
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429 }
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430
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431 int sys_chdir(void)
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432 {
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433 char *path;
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434 struct inode *ip;
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435
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436 if(argstr(0, &path) < 0 || (ip = namei(path)) == 0) {
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437 return -1;
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438 }
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439
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440 ilock(ip);
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441
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442 if(ip->type != T_DIR){
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443 iunlockput(ip);
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444 return -1;
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445 }
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446
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447 iunlock(ip);
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448
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449 iput(proc->cwd);
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450 proc->cwd = ip;
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451
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452 return 0;
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453 }
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454
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455 int sys_exec(void)
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456 {
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457 char *path, *argv[MAXARG];
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458 int i;
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459 uint uargv, uarg;
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460
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461 if(argstr(0, &path) < 0 || argint(1, (int*)&uargv) < 0){
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462 return -1;
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463 }
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464
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465 memset(argv, 0, sizeof(argv));
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466
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467 for(i=0;; i++){
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468 if(i >= NELEM(argv)) {
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469 return -1;
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470 }
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471
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472 if(fetchint(uargv+4*i, (int*)&uarg) < 0) {
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473 return -1;
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474 }
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475
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476 if(uarg == 0){
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477 argv[i] = 0;
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478 break;
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479 }
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480
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|
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481 if(fetchstr(uarg, &argv[i]) < 0) {
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482 return -1;
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483 }
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484 }
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485
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486 return exec(path, argv);
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|
|
487 }
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|
|
488
|
|
|
489 int sys_pipe(void)
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490 {
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|
|
491 int *fd;
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|
|
492 struct file *rf, *wf;
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|
|
493 int fd0, fd1;
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|
|
494
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|
|
495 if(argptr(0, (void*)&fd, 2*sizeof(fd[0])) < 0) {
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|
|
496 return -1;
|
|
|
497 }
|
|
|
498
|
|
|
499 if(pipealloc(&rf, &wf) < 0) {
|
|
|
500 return -1;
|
|
|
501 }
|
|
|
502
|
|
|
503 fd0 = -1;
|
|
|
504
|
|
|
505 if((fd0 = fdalloc(rf)) < 0 || (fd1 = fdalloc(wf)) < 0){
|
|
|
506 if(fd0 >= 0) {
|
|
|
507 proc->ofile[fd0] = 0;
|
|
|
508 }
|
|
|
509
|
|
|
510 fileclose(rf);
|
|
|
511 fileclose(wf);
|
|
|
512
|
|
|
513 return -1;
|
|
|
514 }
|
|
|
515
|
|
|
516 fd[0] = fd0;
|
|
|
517 fd[1] = fd1;
|
|
|
518
|
|
|
519 return 0;
|
|
|
520 }
|
