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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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24
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77 __code cbc_read(__code (*next)(int ret)){
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78 struct file *f;
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79 int n;
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80 char *p;
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81
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82 if(argfd(0, 0, &f) < 0 || argint(2, &n) < 0 || argptr(1, &p, n) < 0) {
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83 goto next(-1);
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84 }
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85 goto cbc_fileread(f, p, n, next);
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86 }
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87
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0
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88 int sys_read(void)
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89 {
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90 struct file *f;
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91 int n;
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92 char *p;
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93
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94 if(argfd(0, 0, &f) < 0 || argint(2, &n) < 0 || argptr(1, &p, n) < 0) {
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95 return -1;
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96 }
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97
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98 return fileread(f, p, n);
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99 }
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100
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101 int sys_write(void)
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102 {
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103 struct file *f;
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104 int n;
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105 char *p;
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106
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107 if(argfd(0, 0, &f) < 0 || argint(2, &n) < 0 || argptr(1, &p, n) < 0) {
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108 return -1;
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109 }
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110
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111 return filewrite(f, p, n);
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112 }
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113
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114 int sys_close(void)
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115 {
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116 int fd;
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117 struct file *f;
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118
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119 if(argfd(0, &fd, &f) < 0) {
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120 return -1;
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121 }
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122
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123 proc->ofile[fd] = 0;
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124 fileclose(f);
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125
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126 return 0;
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127 }
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128
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129 int sys_fstat(void)
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130 {
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131 struct file *f;
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132 struct stat *st;
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133
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134 if(argfd(0, 0, &f) < 0 || argptr(1, (void*)&st, sizeof(*st)) < 0) {
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135 return -1;
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136 }
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137
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138 return filestat(f, st);
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139 }
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140
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141 // Create the path new as a link to the same inode as old.
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142 int sys_link(void)
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143 {
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144 char name[DIRSIZ], *new, *old;
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145 struct inode *dp, *ip;
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146
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147 if(argstr(0, &old) < 0 || argstr(1, &new) < 0) {
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148 return -1;
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149 }
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150
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151 if((ip = namei(old)) == 0) {
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152 return -1;
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153 }
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154
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155 begin_trans();
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156
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157 ilock(ip);
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158
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159 if(ip->type == T_DIR){
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160 iunlockput(ip);
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161 commit_trans();
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162 return -1;
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163 }
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164
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165 ip->nlink++;
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166 iupdate(ip);
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167 iunlock(ip);
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168
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169 if((dp = nameiparent(new, name)) == 0) {
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170 goto bad;
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171 }
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172
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173 ilock(dp);
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174
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175 if(dp->dev != ip->dev || dirlink(dp, name, ip->inum) < 0){
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176 iunlockput(dp);
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177 goto bad;
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178 }
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179
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180 iunlockput(dp);
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181 iput(ip);
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182
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183 commit_trans();
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184
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185 return 0;
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186
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187 bad:
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188 ilock(ip);
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189 ip->nlink--;
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190 iupdate(ip);
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191 iunlockput(ip);
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192 commit_trans();
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193 return -1;
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194 }
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195
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196 // Is the directory dp empty except for "." and ".." ?
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197 static int isdirempty(struct inode *dp)
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198 {
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199 int off;
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200 struct dirent de;
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201
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202 for(off=2*sizeof(de); off<dp->size; off+=sizeof(de)){
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203 if(readi(dp, (char*)&de, off, sizeof(de)) != sizeof(de)) {
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204 panic("isdirempty: readi");
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205 }
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206
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207 if(de.inum != 0) {
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208 return 0;
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209 }
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210 }
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211 return 1;
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212 }
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213
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214 //PAGEBREAK!
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215 int sys_unlink(void)
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216 {
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217 struct inode *ip, *dp;
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218 struct dirent de;
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219 char name[DIRSIZ], *path;
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220 uint off;
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221
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222 if(argstr(0, &path) < 0) {
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223 return -1;
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224 }
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225
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226 if((dp = nameiparent(path, name)) == 0) {
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227 return -1;
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228 }
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229
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230 begin_trans();
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231
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232 ilock(dp);
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233
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234 // Cannot unlink "." or "..".
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235 if(namecmp(name, ".") == 0 || namecmp(name, "..") == 0) {
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236 goto bad;
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237 }
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238
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239 if((ip = dirlookup(dp, name, &off)) == 0) {
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240 goto bad;
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241 }
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242
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243 ilock(ip);
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244
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245 if(ip->nlink < 1) {
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246 panic("unlink: nlink < 1");
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247 }
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248
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249 if(ip->type == T_DIR && !isdirempty(ip)){
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250 iunlockput(ip);
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251 goto bad;
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252 }
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253
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254 memset(&de, 0, sizeof(de));
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255
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256 if(writei(dp, (char*)&de, off, sizeof(de)) != sizeof(de)) {
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257 panic("unlink: writei");
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258 }
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259
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260 if(ip->type == T_DIR){
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261 dp->nlink--;
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262 iupdate(dp);
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263 }
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264
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265 iunlockput(dp);
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266
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267 ip->nlink--;
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268 iupdate(ip);
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269 iunlockput(ip);
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270
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271 commit_trans();
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272
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273 return 0;
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274
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275 bad:
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276 iunlockput(dp);
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277 commit_trans();
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278 return -1;
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279 }
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280
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281 static struct inode* create(char *path, short type, short major, short minor)
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282 {
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283 uint off;
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284 struct inode *ip, *dp;
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285 char name[DIRSIZ];
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286
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287 if((dp = nameiparent(path, name)) == 0) {
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288 return 0;
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289 }
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290
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291 ilock(dp);
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292
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293 if((ip = dirlookup(dp, name, &off)) != 0){
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294 iunlockput(dp);
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295 ilock(ip);
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296
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297 if(type == T_FILE && ip->type == T_FILE) {
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298 return ip;
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299 }
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300
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301 iunlockput(ip);
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302
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303 return 0;
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304 }
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305
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306 if((ip = ialloc(dp->dev, type)) == 0) {
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307 panic("create: ialloc");
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308 }
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309
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310 ilock(ip);
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311 ip->major = major;
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312 ip->minor = minor;
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313 ip->nlink = 1;
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314 iupdate(ip);
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315
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316 if(type == T_DIR){ // Create . and .. entries.
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317 dp->nlink++; // for ".."
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318 iupdate(dp);
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319
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320 // No ip->nlink++ for ".": avoid cyclic ref count.
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321 if(dirlink(ip, ".", ip->inum) < 0 || dirlink(ip, "..", dp->inum) < 0) {
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322 panic("create dots");
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323 }
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324 }
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325
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326 if(dirlink(dp, name, ip->inum) < 0) {
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327 panic("create: dirlink");
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328 }
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329
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330 iunlockput(dp);
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331
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332 return ip;
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333 }
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334
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335 int sys_open(void)
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336 {
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337 char *path;
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338 int fd, omode;
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339 struct file *f;
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340 struct inode *ip;
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341
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342 if(argstr(0, &path) < 0 || argint(1, &omode) < 0) {
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343 return -1;
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344 }
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345
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346 if(omode & O_CREATE){
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347 begin_trans();
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348 ip = create(path, T_FILE, 0, 0);
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349 commit_trans();
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350
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351 if(ip == 0) {
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352 return -1;
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353 }
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354
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355 } else {
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356 if((ip = namei(path)) == 0) {
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357 return -1;
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358 }
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359
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360 ilock(ip);
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361
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362 if(ip->type == T_DIR && omode != O_RDONLY){
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363 iunlockput(ip);
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364 return -1;
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365 }
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366 }
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367
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368 if((f = filealloc()) == 0 || (fd = fdalloc(f)) < 0){
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369 if(f) {
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370 fileclose(f);
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371 }
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372
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373 iunlockput(ip);
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374 return -1;
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375 }
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376
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377 iunlock(ip);
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378
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379 f->type = FD_INODE;
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380 f->ip = ip;
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381 f->off = 0;
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382 f->readable = !(omode & O_WRONLY);
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383 f->writable = (omode & O_WRONLY) || (omode & O_RDWR);
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384
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385 return fd;
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386 }
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387
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388 int sys_mkdir(void)
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389 {
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390 char *path;
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391 struct inode *ip;
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392
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393 begin_trans();
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394
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395 if(argstr(0, &path) < 0 || (ip = create(path, T_DIR, 0, 0)) == 0){
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396 commit_trans();
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397 return -1;
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398 }
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399
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400 iunlockput(ip);
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401 commit_trans();
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402
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403 return 0;
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404 }
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405
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406 int sys_mknod(void)
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407 {
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408 struct inode *ip;
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409 char *path;
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410 int len;
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411 int major, minor;
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412
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413 begin_trans();
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414
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415 if((len=argstr(0, &path)) < 0 ||
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416 argint(1, &major) < 0 || argint(2, &minor) < 0 ||
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417 (ip = create(path, T_DEV, major, minor)) == 0){
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418
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419 commit_trans();
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420 return -1;
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421 }
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422
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423 iunlockput(ip);
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424 commit_trans();
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425
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426 return 0;
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427 }
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428
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429 int sys_chdir(void)
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430 {
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431 char *path;
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432 struct inode *ip;
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433
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434 if(argstr(0, &path) < 0 || (ip = namei(path)) == 0) {
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435 return -1;
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436 }
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437
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438 ilock(ip);
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439
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440 if(ip->type != T_DIR){
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441 iunlockput(ip);
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442 return -1;
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443 }
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444
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445 iunlock(ip);
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446
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447 iput(proc->cwd);
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448 proc->cwd = ip;
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449
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450 return 0;
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451 }
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452
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453 int sys_exec(void)
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454 {
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455 char *path, *argv[MAXARG];
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456 int i;
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457 uint uargv, uarg;
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458
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459 if(argstr(0, &path) < 0 || argint(1, (int*)&uargv) < 0){
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460 return -1;
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461 }
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462
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463 memset(argv, 0, sizeof(argv));
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464
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465 for(i=0;; i++){
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466 if(i >= NELEM(argv)) {
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467 return -1;
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468 }
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469
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470 if(fetchint(uargv+4*i, (int*)&uarg) < 0) {
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471 return -1;
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472 }
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473
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474 if(uarg == 0){
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475 argv[i] = 0;
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476 break;
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477 }
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478
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479 if(fetchstr(uarg, &argv[i]) < 0) {
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480 return -1;
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481 }
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482 }
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483
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484 return exec(path, argv);
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485 }
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486
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487 int sys_pipe(void)
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488 {
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|
|
489 int *fd;
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|
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490 struct file *rf, *wf;
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|
|
491 int fd0, fd1;
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|
492
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|
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493 if(argptr(0, (void*)&fd, 2*sizeof(fd[0])) < 0) {
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|
494 return -1;
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|
|
495 }
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|
|
496
|
|
|
497 if(pipealloc(&rf, &wf) < 0) {
|
|
|
498 return -1;
|
|
|
499 }
|
|
|
500
|
|
|
501 fd0 = -1;
|
|
|
502
|
|
|
503 if((fd0 = fdalloc(rf)) < 0 || (fd1 = fdalloc(wf)) < 0){
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|
|
504 if(fd0 >= 0) {
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|
|
505 proc->ofile[fd0] = 0;
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|
|
506 }
|
|
|
507
|
|
|
508 fileclose(rf);
|
|
|
509 fileclose(wf);
|
|
|
510
|
|
|
511 return -1;
|
|
|
512 }
|
|
|
513
|
|
|
514 fd[0] = fd0;
|
|
|
515 fd[1] = fd1;
|
|
|
516
|
|
|
517 return 0;
|
|
|
518 }
|
