malloc.htm

这是一个Linux内核。是0.11版本的

<a name=L107 href="source/lib/malloc.c#L107">107</a>                 bdesc++;
<a name=L108 href="source/lib/malloc.c#L108">108</a>         }
<a name=L109 href="source/lib/malloc.c#L109">109</a>         <b><i>/*</i></b>
<a name=L110 href="source/lib/malloc.c#L110">110</a> <b><i>         * This is done last, to avoid race conditions in case </i></b>
<a name=L111 href="source/lib/malloc.c#L111">111</a> <b><i>         * get_free_page() sleeps and this routine gets called again....</i></b>
<a name=L112 href="source/lib/malloc.c#L112">112</a> <b><i>         */</i></b>
<a name=L113 href="source/lib/malloc.c#L113">113</a>         bdesc-&gt;next = <a href="ident?i=free_bucket_desc">free_bucket_desc</a>;
<a name=L114 href="source/lib/malloc.c#L114">114</a>         <a href="ident?i=free_bucket_desc">free_bucket_desc</a> = first;
<a name=L115 href="source/lib/malloc.c#L115">115</a> }
<a name=L116 href="source/lib/malloc.c#L116">116</a> 
<a name=L117 href="source/lib/malloc.c#L117">117</a> void *<a href="ident?i=malloc">malloc</a>(unsigned int len)
<a name=L118 href="source/lib/malloc.c#L118">118</a> {
<a name=L119 href="source/lib/malloc.c#L119">119</a>         struct <a href="ident?i=_bucket_dir">_bucket_dir</a>      *bdir;
<a name=L120 href="source/lib/malloc.c#L120">120</a>         struct <a href="ident?i=bucket_desc">bucket_desc</a>      *bdesc;
<a name=L121 href="source/lib/malloc.c#L121">121</a>         void                    *retval;
<a name=L122 href="source/lib/malloc.c#L122">122</a> 
<a name=L123 href="source/lib/malloc.c#L123">123</a>         <b><i>/*</i></b>
<a name=L124 href="source/lib/malloc.c#L124">124</a> <b><i>         * First we search the bucket_dir to find the right bucket change</i></b>
<a name=L125 href="source/lib/malloc.c#L125">125</a> <b><i>         * for this request.</i></b>
<a name=L126 href="source/lib/malloc.c#L126">126</a> <b><i>         */</i></b>
<a name=L127 href="source/lib/malloc.c#L127">127</a>         for (bdir = <a href="ident?i=bucket_dir">bucket_dir</a>; bdir-&gt;size; bdir++)
<a name=L128 href="source/lib/malloc.c#L128">128</a>                 if (bdir-&gt;size &gt;= len)
<a name=L129 href="source/lib/malloc.c#L129">129</a>                         break;
<a name=L130 href="source/lib/malloc.c#L130">130</a>         if (!bdir-&gt;size) {
<a name=L131 href="source/lib/malloc.c#L131">131</a>                 <a href="ident?i=printk">printk</a>(<i>"malloc called with impossibly large argument (%d)\n"</i>,
<a name=L132 href="source/lib/malloc.c#L132">132</a>                         len);
<a name=L133 href="source/lib/malloc.c#L133">133</a>                 <a href="ident?i=panic">panic</a>(<i>"malloc: bad arg"</i>);
<a name=L134 href="source/lib/malloc.c#L134">134</a>         }
<a name=L135 href="source/lib/malloc.c#L135">135</a>         <b><i>/*</i></b>
<a name=L136 href="source/lib/malloc.c#L136">136</a> <b><i>         * Now we search for a bucket descriptor which has free space</i></b>
<a name=L137 href="source/lib/malloc.c#L137">137</a> <b><i>         */</i></b>
<a name=L138 href="source/lib/malloc.c#L138">138</a>         <a href="ident?i=cli">cli</a>();  <b><i>/* Avoid race conditions */</i></b>
<a name=L139 href="source/lib/malloc.c#L139">139</a>         for (bdesc = bdir-&gt;chain; bdesc; bdesc = bdesc-&gt;next) 
<a name=L140 href="source/lib/malloc.c#L140">140</a>                 if (bdesc-&gt;freeptr)
<a name=L141 href="source/lib/malloc.c#L141">141</a>                         break;
<a name=L142 href="source/lib/malloc.c#L142">142</a>         <b><i>/*</i></b>
<a name=L143 href="source/lib/malloc.c#L143">143</a> <b><i>         * If we didn't find a bucket with free space, then we'll </i></b>
<a name=L144 href="source/lib/malloc.c#L144">144</a> <b><i>         * allocate a new one.</i></b>
<a name=L145 href="source/lib/malloc.c#L145">145</a> <b><i>         */</i></b>
<a name=L146 href="source/lib/malloc.c#L146">146</a>         if (!bdesc) {
<a name=L147 href="source/lib/malloc.c#L147">147</a>                 char            *cp;
<a name=L148 href="source/lib/malloc.c#L148">148</a>                 int             i;
<a name=L149 href="source/lib/malloc.c#L149">149</a> 
<a name=L150 href="source/lib/malloc.c#L150">150</a>                 if (!<a href="ident?i=free_bucket_desc">free_bucket_desc</a>)  
<a name=L151 href="source/lib/malloc.c#L151">151</a>                         <a href="ident?i=init_bucket_desc">init_bucket_desc</a>();
<a name=L152 href="source/lib/malloc.c#L152">152</a>                 bdesc = <a href="ident?i=free_bucket_desc">free_bucket_desc</a>;
<a name=L153 href="source/lib/malloc.c#L153">153</a>                 <a href="ident?i=free_bucket_desc">free_bucket_desc</a> = bdesc-&gt;next;
<a name=L154 href="source/lib/malloc.c#L154">154</a>                 bdesc-&gt;refcnt = 0;
<a name=L155 href="source/lib/malloc.c#L155">155</a>                 bdesc-&gt;bucket_size = bdir-&gt;size;
<a name=L156 href="source/lib/malloc.c#L156">156</a>                 bdesc-&gt;page = bdesc-&gt;freeptr = (void *) cp = <a href="ident?i=get_free_page">get_free_page</a>();
<a name=L157 href="source/lib/malloc.c#L157">157</a>                 if (!cp)
<a name=L158 href="source/lib/malloc.c#L158">158</a>                         <a href="ident?i=panic">panic</a>(<i>"Out of memory in kernel malloc()"</i>);
<a name=L159 href="source/lib/malloc.c#L159">159</a>                 <b><i>/* Set up the chain of free objects */</i></b>
<a name=L160 href="source/lib/malloc.c#L160">160</a>                 for (i=<a href="ident?i=PAGE_SIZE">PAGE_SIZE</a>/bdir-&gt;size; i &gt; 1; i--) {
<a name=L161 href="source/lib/malloc.c#L161">161</a>                         *((char **) cp) = cp + bdir-&gt;size;
<a name=L162 href="source/lib/malloc.c#L162">162</a>                         cp += bdir-&gt;size;
<a name=L163 href="source/lib/malloc.c#L163">163</a>                 }
<a name=L164 href="source/lib/malloc.c#L164">164</a>                 *((char **) cp) = 0;
<a name=L165 href="source/lib/malloc.c#L165">165</a>                 bdesc-&gt;next = bdir-&gt;chain; <b><i>/* OK, link it in! */</i></b>
<a name=L166 href="source/lib/malloc.c#L166">166</a>                 bdir-&gt;chain = bdesc;
<a name=L167 href="source/lib/malloc.c#L167">167</a>         }
<a name=L168 href="source/lib/malloc.c#L168">168</a>         retval = (void *) bdesc-&gt;freeptr;
<a name=L169 href="source/lib/malloc.c#L169">169</a>         bdesc-&gt;freeptr = *((void **) retval);
<a name=L170 href="source/lib/malloc.c#L170">170</a>         bdesc-&gt;refcnt++;
<a name=L171 href="source/lib/malloc.c#L171">171</a>         <a href="ident?i=sti">sti</a>();  <b><i>/* OK, we're safe again */</i></b>
<a name=L172 href="source/lib/malloc.c#L172">172</a>         return(retval);
<a name=L173 href="source/lib/malloc.c#L173">173</a> }
<a name=L174 href="source/lib/malloc.c#L174">174</a> 
<a name=L175 href="source/lib/malloc.c#L175">175</a> <b><i>/*</i></b>
<a name=L176 href="source/lib/malloc.c#L176">176</a> <b><i> * Here is the free routine.  If you know the size of the object that you</i></b>
<a name=L177 href="source/lib/malloc.c#L177">177</a> <b><i> * are freeing, then free_s() will use that information to speed up the</i></b>
<a name=L178 href="source/lib/malloc.c#L178">178</a> <b><i> * search for the bucket descriptor.</i></b>
<a name=L179 href="source/lib/malloc.c#L179">179</a> <b><i> * </i></b>
<a name=L180 href="source/lib/malloc.c#L180">180</a> <b><i> * We will #define a macro so that "free(x)" is becomes "free_s(x, 0)"</i></b>
<a name=L181 href="source/lib/malloc.c#L181">181</a> <b><i> */</i></b>
<a name=L182 href="source/lib/malloc.c#L182">182</a> void <a href="ident?i=free_s">free_s</a>(void *obj, int size)
<a name=L183 href="source/lib/malloc.c#L183">183</a> {
<a name=L184 href="source/lib/malloc.c#L184">184</a>         void            *page;
<a name=L185 href="source/lib/malloc.c#L185">185</a>         struct <a href="ident?i=_bucket_dir">_bucket_dir</a>      *bdir;
<a name=L186 href="source/lib/malloc.c#L186">186</a>         struct <a href="ident?i=bucket_desc">bucket_desc</a>      *bdesc, *prev;
<a name=L187 href="source/lib/malloc.c#L187">187</a> 
<a name=L188 href="source/lib/malloc.c#L188">188</a>         <b><i>/* Calculate what page this object lives in */</i></b>
<a name=L189 href="source/lib/malloc.c#L189">189</a>         page = (void *)  ((unsigned long) obj &amp; 0xfffff000);
<a name=L190 href="source/lib/malloc.c#L190">190</a>         <b><i>/* Now search the buckets looking for that page */</i></b>
<a name=L191 href="source/lib/malloc.c#L191">191</a>         for (bdir = <a href="ident?i=bucket_dir">bucket_dir</a>; bdir-&gt;size; bdir++) {
<a name=L192 href="source/lib/malloc.c#L192">192</a>                 prev = 0;
<a name=L193 href="source/lib/malloc.c#L193">193</a>                 <b><i>/* If size is zero then this conditional is always false */</i></b>
<a name=L194 href="source/lib/malloc.c#L194">194</a>                 if (bdir-&gt;size &lt; size)
<a name=L195 href="source/lib/malloc.c#L195">195</a>                         continue;
<a name=L196 href="source/lib/malloc.c#L196">196</a>                 for (bdesc = bdir-&gt;chain; bdesc; bdesc = bdesc-&gt;next) {
<a name=L197 href="source/lib/malloc.c#L197">197</a>                         if (bdesc-&gt;page == page) 
<a name=L198 href="source/lib/malloc.c#L198">198</a>                                 goto found;
<a name=L199 href="source/lib/malloc.c#L199">199</a>                         prev = bdesc;
<a name=L200 href="source/lib/malloc.c#L200">200</a>                 }
<a name=L201 href="source/lib/malloc.c#L201">201</a>         }
<a name=L202 href="source/lib/malloc.c#L202">202</a>         <a href="ident?i=panic">panic</a>(<i>"Bad address passed to kernel free_s()"</i>);
<a name=L203 href="source/lib/malloc.c#L203">203</a> found:
<a name=L204 href="source/lib/malloc.c#L204">204</a>         <a href="ident?i=cli">cli</a>(); <b><i>/* To avoid race conditions */</i></b>
<a name=L205 href="source/lib/malloc.c#L205">205</a>         *((void **)obj) = bdesc-&gt;freeptr;
<a name=L206 href="source/lib/malloc.c#L206">206</a>         bdesc-&gt;freeptr = obj;
<a name=L207 href="source/lib/malloc.c#L207">207</a>         bdesc-&gt;refcnt--;
<a name=L208 href="source/lib/malloc.c#L208">208</a>         if (bdesc-&gt;refcnt == 0) {
<a name=L209 href="source/lib/malloc.c#L209">209</a>                 <b><i>/*</i></b>
<a name=L210 href="source/lib/malloc.c#L210">210</a> <b><i>                 * We need to make sure that prev is still accurate.  It</i></b>
<a name=L211 href="source/lib/malloc.c#L211">211</a> <b><i>                 * may not be, if someone rudely interrupted us....</i></b>
<a name=L212 href="source/lib/malloc.c#L212">212</a> <b><i>                 */</i></b>
<a name=L213 href="source/lib/malloc.c#L213">213</a>                 if ((prev &amp;&amp; (prev-&gt;next != bdesc)) ||
<a name=L214 href="source/lib/malloc.c#L214">214</a>                     (!prev &amp;&amp; (bdir-&gt;chain != bdesc)))
<a name=L215 href="source/lib/malloc.c#L215">215</a>                         for (prev = bdir-&gt;chain; prev; prev = prev-&gt;next)
<a name=L216 href="source/lib/malloc.c#L216">216</a>                                 if (prev-&gt;next == bdesc)
<a name=L217 href="source/lib/malloc.c#L217">217</a>                                         break;
<a name=L218 href="source/lib/malloc.c#L218">218</a>                 if (prev)
<a name=L219 href="source/lib/malloc.c#L219">219</a>                         prev-&gt;next = bdesc-&gt;next;
<a name=L220 href="source/lib/malloc.c#L220">220</a>                 else {
<a name=L221 href="source/lib/malloc.c#L221">221</a>                         if (bdir-&gt;chain != bdesc)
<a name=L222 href="source/lib/malloc.c#L222">222</a>                                 <a href="ident?i=panic">panic</a>(<i>"malloc bucket chains corrupted"</i>);
<a name=L223 href="source/lib/malloc.c#L223">223</a>                         bdir-&gt;chain = bdesc-&gt;next;
<a name=L224 href="source/lib/malloc.c#L224">224</a>                 }
<a name=L225 href="source/lib/malloc.c#L225">225</a>                 <a href="ident?i=free_page">free_page</a>((unsigned long) bdesc-&gt;page);
<a name=L226 href="source/lib/malloc.c#L226">226</a>                 bdesc-&gt;next = <a href="ident?i=free_bucket_desc">free_bucket_desc</a>;
<a name=L227 href="source/lib/malloc.c#L227">227</a>                 <a href="ident?i=free_bucket_desc">free_bucket_desc</a> = bdesc;
<a name=L228 href="source/lib/malloc.c#L228">228</a>         }
<a name=L229 href="source/lib/malloc.c#L229">229</a>         <a href="ident?i=sti">sti</a>();
<a name=L230 href="source/lib/malloc.c#L230">230</a>         return;
<a name=L231 href="source/lib/malloc.c#L231">231</a> }
<a name=L232 href="source/lib/malloc.c#L232">232</a> 
<a name=L233 href="source/lib/malloc.c#L233">233</a> </pre><hr>
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