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1 /*
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2 * CDDL HEADER START
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3 *
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4 * The contents of this file are subject to the terms of the
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5 * Common Development and Distribution License, Version 1.0 only
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6 * (the "License"). You may not use this file except in compliance
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7 * with the License.
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8 *
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9 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
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10 * or http://www.opensolaris.org/os/licensing.
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11 * See the License for the specific language governing permissions
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12 * and limitations under the License.
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13 *
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14 * When distributing Covered Code, include this CDDL HEADER in each
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15 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
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16 * If applicable, add the following below this CDDL HEADER, with the
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17 * fields enclosed by brackets "[]" replaced with your own identifying
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18 * information: Portions Copyright [yyyy] [name of copyright owner]
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19 *
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20 * CDDL HEADER END
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21 */
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22 /* Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
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23 /* All Rights Reserved */
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24
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25
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26 /*
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27 * University Copyright- Copyright (c) 1982, 1986, 1988
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28 * The Regents of the University of California
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29 * All Rights Reserved
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30 *
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31 * University Acknowledgment- Portions of this document are derived from
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32 * software developed by the University of California, Berkeley, and its
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33 * contributors.
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34 */
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35
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36 #pragma ident "@(#)sigretro.c 1.11 05/06/08 SMI"
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37
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38 /*
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39 * mailx -- a modified version of a University of California at Berkeley
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40 * mail program
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41 */
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42
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43 /*
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44 * This code is only compiled in if SIG_HOLD is not defined!
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45 *
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46 * Retrofit new signal interface to old signal primitives.
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47 * Supported routines:
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48 * sigsys(sig, func)
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49 * sigset(sig, func)
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50 * sighold(sig)
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51 * sigrelse(sig)
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52 * sigignore(sig)
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53 * sigpause(sig)
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54 * Also,
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55 * sigchild()
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56 * to set all held signals to ignored signals in the
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57 * child process after fork(2)
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58 */
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59 #include <signal.h>
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60
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61 #ifndef SIG_HOLD
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62 # include <errno.h>
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63 # include <setjmp.h>
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64 # include <stdio.h>
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65
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66 extern int errno;
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67
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68 typedef void (*sigtype)();
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69
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70 #define SIG_HOLD ((sigtype) 2)
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71 #ifndef SIG_ERR
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72 # define SIG_ERR ((sigtype) -1)
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73 #endif
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74
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75 sigtype sigdisp(), sighold(), sigignore();
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76 void _Sigtramp();
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77
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78 /*
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79 * The following helps us keep the extended signal semantics together.
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80 * We remember for each signal the address of the function we're
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81 * supposed to call. s_func is SIG_DFL / SIG_IGN if appropriate.
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82 */
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83 static struct sigtable {
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84 sigtype s_func; /* What to call */
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85 int s_flag; /* Signal flags; see below */
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86 } sigtable[NSIG + 1];
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87
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88 /*
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89 * Signal flag values.
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90 */
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91 #define SHELD 1 /* Signal is being held */
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92 #define SDEFER 2 /* Signal occured while held */
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93 #define SSET 4 /* s_func is believable */
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94 #define SPAUSE 8 /* are pausing, waiting for sig */
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95
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96 jmp_buf _pause; /* For doing sigpause() */
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97
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98 /*
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99 * Approximate sigsys() system call
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100 * This is almost useless since one only calls sigsys()
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101 * in the child of a vfork(). If you have vfork(), you have new signals
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102 * anyway. The real sigsys() does all the stuff needed to support
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103 * the real sigset() library. We don't bother here, assuming that
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104 * you are either ignoring or defaulting a signal in the child.
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105 */
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106 sigtype
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107 sigsys(int sig, sigtype func)
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108 {
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109 sigtype old;
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110
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111 old = sigdisp(sig);
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112 signal(sig, func);
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113 return(old);
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114 }
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115
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116
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117 /*
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118 * Set the (permanent) disposition of a signal.
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119 * If the signal is subsequently (or even now) held,
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120 * the action you set here can be enabled using sigrelse().
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121 */
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122 sigtype
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123 sigset(int sig, sigtype func)
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124 {
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125 sigtype old;
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126
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127 if (sig < 1 || sig > NSIG) {
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128 errno = EINVAL;
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129 return(SIG_ERR);
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130 }
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131 old = sigdisp(sig);
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132 /*
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133 * Does anyone actually call sigset with SIG_HOLD!?
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134 */
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135 if (func == SIG_HOLD) {
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136 sighold(sig);
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137 return(old);
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138 }
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139 sigtable[sig].s_flag |= SSET;
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140 sigtable[sig].s_func = func;
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141 if (func == SIG_DFL) {
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142 /*
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143 * If signal has been held, must retain
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144 * the catch so that we can note occurrance
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145 * of signal.
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146 */
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147 if ((sigtable[sig].s_flag & SHELD) == 0)
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148 signal(sig, SIG_DFL);
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149 else
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150 signal(sig, _Sigtramp);
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151 return(old);
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152 }
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153 if (func == SIG_IGN) {
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154 /*
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155 * Clear pending signal
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156 */
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157 signal(sig, SIG_IGN);
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158 sigtable[sig].s_flag &= ~SDEFER;
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159 return(old);
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160 }
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161 signal(sig, _Sigtramp);
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162 return(old);
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163 }
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164
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165 /*
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166 * Hold a signal.
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167 * This CAN be tricky if the signal's disposition is SIG_DFL.
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168 * In that case, we still catch the signal so we can note it
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169 */
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170 sigtype
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171 sighold(int sig)
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172 {
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173 sigtype old;
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174
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175 if (sig < 1 || sig > NSIG) {
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176 errno = EINVAL;
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177 return(SIG_ERR);
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178 }
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179 old = sigdisp(sig);
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180 if (sigtable[sig].s_flag & SHELD)
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181 return(old);
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182 /*
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183 * When the default action is required, we have to
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184 * set up to catch the signal to note signal's occurrance.
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185 */
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186 if (old == SIG_DFL) {
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187 sigtable[sig].s_flag |= SSET;
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188 signal(sig, _Sigtramp);
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189 }
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190 sigtable[sig].s_flag |= SHELD;
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191 return(old);
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192 }
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193
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194 /*
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195 * Release a signal
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196 * If the signal occurred while we had it held, cause the signal.
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197 */
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198 sigtype
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199 sigrelse(int sig)
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200 {
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201 sigtype old;
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202
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203 if (sig < 1 || sig > NSIG) {
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204 errno = EINVAL;
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205 return(SIG_ERR);
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206 }
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207 old = sigdisp(sig);
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208 if ((sigtable[sig].s_flag & SHELD) == 0)
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209 return(old);
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210 sigtable[sig].s_flag &= ~SHELD;
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211 if (sigtable[sig].s_flag & SDEFER)
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212 _Sigtramp(sig);
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213 /*
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214 * If disposition was the default, then we can unset the
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215 * catch to _Sigtramp() and let the system do the work.
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216 */
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217 if (sigtable[sig].s_func == SIG_DFL)
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218 signal(sig, SIG_DFL);
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219 return(old);
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220 }
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221
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222 /*
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223 * Ignore a signal.
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224 */
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225 sigtype
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226 sigignore(int sig)
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227 {
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228 return(sigset(sig, SIG_IGN));
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229 }
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230
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231 /*
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232 * Pause, waiting for sig to occur.
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233 * We assume LUSER called us with the signal held.
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234 * When we got the signal, mark the signal as having
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235 * occurred. It will actually cause something when
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236 * the signal is released.
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237 */
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238 int
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239 sigpause(int sig)
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240 {
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241 if (sig < 1 || sig > NSIG) {
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242 errno = EINVAL;
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243 return;
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244 }
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245 sigtable[sig].s_flag |= SHELD|SPAUSE;
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246 if (setjmp(_pause) == 0)
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247 pause();
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248 sigtable[sig].s_flag &= ~SPAUSE;
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249 sigtable[sig].s_flag |= SDEFER;
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250 }
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251
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252 /*
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253 * In the child process after fork(2), set the disposition of all held
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254 * signals to SIG_IGN. This is a new procedure not in the real sigset()
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255 * package, provided for retrofitting purposes.
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256 */
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257 int
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258 sigchild(void)
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259 {
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260 register int i;
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261
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262 for (i = 1; i <= NSIG; i++)
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263 if (sigtable[i].s_flag & SHELD)
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264 signal(i, SIG_IGN);
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265 }
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266
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267
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268 /*
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269 * Return the current disposition of a signal
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270 * If we have not set this signal before, we have to
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271 * ask the system
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272 */
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273 sigtype
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274 sigdisp(int sig)
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275 {
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276 sigtype old;
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277
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278 if (sig < 1 || sig > NSIG) {
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279 errno = EINVAL;
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280 return(SIG_ERR);
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281 }
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282 /*
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283 * If we have no knowledge of this signal,
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284 * ask the system, then save the result for later.
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285 */
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286 if ((sigtable[sig].s_flag & SSET) == 0) {
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287 old = signal(sig, SIG_IGN);
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288 sigtable[sig].s_func = old;
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289 sigtable[sig].s_flag |= SSET;
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290 signal(sig, old);
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291 return(old);
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292 }
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293 /*
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294 * If we have set this signal before, then sigset()
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295 * will have been careful to leave something meaningful
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296 * in s_func.
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297 */
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298 return(sigtable[sig].s_func);
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299 }
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300
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301 /*
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302 * The following routine gets called for any signal
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303 * that is to be trapped to a user function.
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304 */
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305 void
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306 _Sigtramp(int sig)
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307 {
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308 sigtype old;
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309
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310 if (sig < 1 || sig > NSIG) {
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311 errno = EINVAL;
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312 return;
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313 }
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314
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315 top:
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316 old = signal(sig, SIG_IGN);
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317 /*
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318 * If signal being paused on, wakeup sigpause()
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319 */
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320 if (sigtable[sig].s_flag & SPAUSE)
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321 longjmp(_pause, 1);
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322 /*
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323 * If signal is being held, mark its table entry
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324 * so we can trigger it when signal is released.
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325 * Then just return.
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326 */
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327 if (sigtable[sig].s_flag & SHELD) {
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328 sigtable[sig].s_flag |= SDEFER;
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329 signal(sig, _Sigtramp);
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330 return;
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331 }
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332 /*
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333 * If the signal is being ignored, just return.
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334 * This would make SIGCONT more normal, but of course
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335 * any system with SIGCONT also has the new signal pkg, so...
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336 */
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337 if (sigtable[sig].s_func == SIG_IGN)
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338 return;
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339 /*
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340 * If the signal is SIG_DFL, then we probably got here
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341 * by holding the signal, having it happen, then releasing
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342 * the signal.
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343 */
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344 if (sigtable[sig].s_func == SIG_DFL) {
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345 signal(sig, SIG_DFL);
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346 kill(getpid(), sig);
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347 /* Will we get back here? */
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348 return;
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349 }
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350 /*
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351 * Looks like we should just cause the signal...
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352 * We hold the signal for the duration of the user's
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353 * code with the signal re-enabled. If the signal
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354 * happens again while in user code, we will recursively
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355 * trap here and mark that we had another occurance
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356 * and return to the user's trap code. When we return
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357 * from there, we can cause the signal again.
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358 */
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359 sigtable[sig].s_flag &= ~SDEFER;
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360 sigtable[sig].s_flag |= SHELD;
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361 signal(sig, _Sigtramp);
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362 (*sigtable[sig].s_func)(sig);
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363 /*
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364 * If the signal re-occurred while in the user's routine,
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365 * just go try it again...
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366 */
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367 sigtable[sig].s_flag &= ~SHELD;
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368 if (sigtable[sig].s_flag & SDEFER)
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369 goto top;
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370 }
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371 #endif
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