{"id":3993,"date":"2012-05-15T22:10:44","date_gmt":"2012-05-15T14:10:44","guid":{"rendered":"http:\/\/edsionte.com\/techblog\/?p=3993"},"modified":"2012-05-16T11:37:53","modified_gmt":"2012-05-16T03:37:53","slug":"linux%e5%86%85%e5%ad%98%e7%ae%a1%e7%90%86%e5%ae%9e%e8%b7%b5-%e4%bd%bf%e7%94%a8fault%e6%98%a0%e5%b0%84%e5%86%85%e5%ad%981","status":"publish","type":"post","link":"http:\/\/edsionte.com\/techblog\/archives\/3993","title":{"rendered":"Linux\u5185\u5b58\u7ba1\u7406\u5b9e\u8df5-\u4f7f\u7528fault()\u5b9e\u73b0\u5185\u5b58\u6620\u5c04"},"content":{"rendered":"<p>\u5185\u6838\u6001\u4e0e\u7528\u6237\u6001\u8fdb\u884c\u6570\u636e\u4ea4\u4e92\u901a\u5e38\u662f\u8fd9\u6837\u4e00\u79cd\u6a21\u578b\uff1a\u5185\u6838\u5229\u7528\u81ea\u8eab\u7684\u7279\u6743\u901a\u8fc7\u7279\u5b9a\u7684\u670d\u52a1\u7a0b\u5e8f\u91c7\u96c6\u3001\u63a5\u6536\u548c\u5904\u7406\u6570\u636e\uff1b\u63a5\u7740\uff0c\u7528\u6237\u6001\u7a0b\u5e8f\u548c\u5185\u6838\u670d\u52a1\u7a0b\u5e8f\u8fdb\u884c\u6570\u636e\u4ea4\u4e92\uff0c\u6216\u63a5\u6536\u5185\u6838\u6001\u7684\u6570\u636e\uff0c\u6216\u5411\u5185\u6838\u6001\u5199\u5165\u6570\u636e\u3002\u901a\u8fc7\u4f20\u7edf\u7684\u90a3\u4e9b\u5bf9\u6587\u4ef6\u64cd\u4f5c\u7684\u7cfb\u7edf\u8c03\u7528\u5c31\u53ef\u4ee5\u5b8c\u6210\u8fd9\u6837\u7684\u5de5\u4f5c\uff0c\u4f46\u662f\u6211\u4eec\u6709\u65f6\u5019\u9700\u8981\u901a\u8fc7\u8bbf\u95ee\u7528\u6237\u7a7a\u95f4\u7684\u5185\u5b58\u6765\u76f4\u63a5\u8bfb\u53d6\u5185\u6838\u6570\u636e\uff0c\u56e0\u4e3a\u8fd9\u6837\u53ef\u4ee5\u514d\u53bb\u6570\u636e\u5728\u5185\u6838\u6001\u4e0e\u7528\u6237\u6001\u4e4b\u95f4\u62f7\u8d1d\u6240\u82b1\u8d39\u7684\u65f6\u95f4\u3002<\/p>\n<p>\u672c\u6587\u57fa\u4e8e\u4ee5\u4e0a\u80cc\u666f\uff0c\u4ee5Linux\u5b57\u7b26\u8bbe\u5907\u9a71\u52a8\u4e3a\u57fa\u7840\uff0c\u901a\u8fc7\u5185\u5b58\u6620\u5c04\u5c06\u5185\u6838\u4e2d\u7684\u4e00\u90e8\u5206\u865a\u62df\u5185\u5b58\u76f4\u63a5\u6620\u5c04\u5230\u7528\u6237\u7a7a\u95f4\uff0c\u4f7f\u5f97\u7528\u6237\u5728\u8bbf\u95ee\u5185\u5b58\u65f6\u7b49\u540c\u4e8e\u76f4\u63a5\u8bbf\u95ee\u5185\u6838\u7a7a\u95f4\uff0c\u4ece\u800c\u76f4\u63a5\u83b7\u53d6\u5185\u6838\u7a7a\u95f4\u7684\u6570\u636e\u3002<\/p>\n<h3>1.\u5b9e\u73b0\u539f\u7406<\/h3>\n<p>\u4e0d\u7ba1\u8fdb\u7a0b\u662f\u5728\u7528\u6237\u7a7a\u95f4\u8bbf\u95ee\u6570\u636e\u8fd8\u662f\u5728\u5185\u6838\u7a7a\u95f4\u8bbf\u95ee\u6570\u636e\uff0c\u5b83\u6240\u9762\u4e34\u7684\u90fd\u662f\u865a\u62df\u5730\u5740\u3002\u7531\u4e8eLinux\u5bf9\u5206\u6bb5\u673a\u5236\u8fdb\u884c\u4e86\u7279\u6b8a\u5904\u7406\uff0c\u56e0\u6b64\u8fd9\u91cc\u7684\u865a\u62df\u5730\u5740\u5c31\u7b49\u540c\u4e8e\u7ebf\u6027\u5730\u5740\u3002\u6309\u7167\u4e00\u5f00\u59cb\u6211\u4eec\u63d0\u51fa\u7684\u8981\u6c42\uff0c\u8fdb\u7a0b\u901a\u8fc7\u8bbf\u95ee\u7528\u6237\u865a\u62df\u5730\u5740A\u6765\u8fbe\u5230\u76f4\u63a5\u8bbf\u95ee\u5185\u6838\u865a\u62df\u5730\u5740B\u4e2d\u6240\u5b58\u50a8\u6570\u636e\u7684\u76ee\u7684\uff0c\u8fd9\u91cc\u7684\u5730\u5740A\u548cB\u5fc5\u7136\u4e0d\u76f8\u540c\u3002\u90a3\u4e48\uff0c\u5982\u4f55\u901a\u8fc7\u4e0d\u540c\u7684\u865a\u62df\u5730\u5740\u6765\u8bbf\u95ee\u76f8\u540c\u7684\u6570\u636e\uff1f\u6211\u4eec\u53ef\u4ee5\u5c06\u865a\u62df\u5730\u5740A\u548cB\u90fd\u6620\u5c04\u5230\u540c\u4e00\u5757\u7269\u7406\u5185\u5b58\uff0c\u5c31\u53ef\u4ee5\u5b9e\u73b0\u5185\u6838\u7a7a\u95f4\u548c\u7528\u6237\u7a7a\u95f4\u4e4b\u95f4\u7684\u6570\u636e\u5171\u4eab\u3002<\/p>\n<p>\u793a\u610f\u56fe\u5982\u4e0b\uff1a<\/p>\n<p>\u865a\u62df\u5185\u5b58\u548c\u7269\u7406\u5185\u5b58\u4e4b\u95f4\u5982\u4f55\u8054\u7cfb\uff1f\u5f53\u7136\u662f\u901a\u8fc7\u9875\u8868\u4e86\u3002\u6211\u4eec\u5728\u5185\u6838\u7a7a\u95f4\u63d0\u524d\u5206\u914d\u597d\u7f13\u51b2\u533a\uff0c\u5e76\u4e14\u5411\u8be5\u7f13\u51b2\u533a\u5199\u5165\u6570\u636e\uff0c\u6b64\u65f6\u5185\u6838\u4f1a\u81ea\u52a8\u5c06\u8be5\u7f13\u51b2\u533a\u5bf9\u5e94\u7684\u5185\u6838\u865a\u62df\u5730\u5740\u4e0e\u5b9e\u9645\u7684\u67d0\u4e00\u5feb\u7269\u7406\u5185\u5b58\u8fdb\u884c\u5173\u8054\uff0c\u5e76\u5c06\u5b83\u4eec\u7684\u6620\u5c04\u5173\u7cfb\u4fdd\u5b58\u5728\u5185\u6838\u9875\u8868\u4e2d\u3002\u5f53\u5728\u5185\u6838\u7a7a\u95f4\u5206\u914d\u5185\u5b58\u65f6\u65f6\uff0c\u4e0a\u8ff0\u5de5\u4f5c\u81ea\u52a8\u88ab\u5b8c\u6210\uff0c\u6bd4\u5982\u901a\u8fc7kmalloc()\u5206\u914d\u5185\u5b58\u65f6\u3002<\/p>\n<p>\u4e00\u65e6\u5728\u5185\u6838\u7a7a\u95f4\u4e2d\u5206\u914d\u4e86\u5185\u5b58\uff0c\u968f\u4e4b\u5c31\u786e\u5b9a\u4e86\u7269\u7406\u5185\u5b58\u3002\u73b0\u5728\u6211\u4eec\u9700\u8981\u505a\u7684\u662f\u5c06\u7528\u6237\u865a\u62df\u5730\u5740\u4e0e\u7269\u7406\u5185\u5b58\u8fdb\u884c\u5173\u8054\uff0c\u4e5f\u5c31\u662f\u8bf4\u6211\u4eec\u8981\u5c06\u8fd9\u4e2a\u6620\u5c04\u5173\u7cfb\u5199\u5165\u8fdb\u7a0b\u7684\u7528\u6237\u9875\u8868\u3002\u6574\u4e2a\u5173\u8054\u7684\u8fc7\u7a0b\u662f\u5185\u6838\u7f3a\u9875\u5f02\u5e38\u5904\u7406\u7a0b\u5e8f\u5b8c\u6210\u7684\uff0c\u8fd9\u4e2a\u5904\u7406\u8fc7\u7a0b\u6bd4\u8f83\u590d\u6742\u3002\u6211\u4eec\u8981\u5728\u5185\u6838\u4e2d\u5b9e\u73b0\u7684\u5e76\u4e0d\u662f\u7f3a\u9875\u5f02\u5e38\u5904\u7406\u7a0b\u5e8f\uff0c\u56e0\u4e3a\u5185\u6838\u5df2\u7ecf\u5b9e\u73b0\u7684\u5f88\u5b8c\u7f8e\uff0c\u800c\u53ea\u9700\u5b8c\u6210\u5176\u4e2d\u7684\u4e00\u5c0f\u90e8\u95e8\u3002\u5177\u4f53\u5982\u4f55\u5b9e\u73b0\u4e0b\u95ee\u4f1a\u8be6\u7ec6\u8bf4\u660e\u3002<\/p>\n<h3>2.\u7528\u6237\u6001\u7a0b\u5e8f\u7684\u5b9e\u73b0<\/h3>\n<p>\u5728\u672c\u6587\u6240\u63cf\u8ff0\u7684\u5185\u5b58\u7ba1\u7406\u8bd5\u9a8c\uff0c\u7528\u6237\u6001\u7a0b\u5e8f\u9996\u5148\u901a\u8fc7open()\u6253\u5f00\u5b57\u7b26\u8bbe\u5907\u6587\u4ef6mapdrv\uff0c\u8be5\u7cfb\u7edf\u8c03\u7528\u6267\u884c\u6210\u529f\u65f6\u8fd4\u56de\u6587\u4ef6\u63cf\u8ff0\u7b26\uff1b\u901a\u8fc7mmap()\u5c06\u8be5\u8bbe\u5907\u6587\u4ef6\u6620\u5c04\u5230\u5f53\u524d\u8fdb\u7a0b\u7684\u7528\u6237\u7a7a\u95f4\u4e2d\uff0c\u8be5\u7cfb\u7edf\u8c03\u7528\u6267\u884c\u6210\u529f\u65f6\u8fd4\u56de\u6307\u5411\u6620\u5c04\u533a\u57df\u7684\u6307\u9488\uff1b\u6700\u540e\u901a\u8fc7\u8be5\u6307\u9488\u6253\u5370\u6570\u636e\u3002\u7528\u6237\u6001\u7a0b\u5e8f\u7684\u5b9e\u73b0\u5982\u4e0b\u6240\u793a\uff1a<\/p>\n<pre class=\"brush: cpp; title: ; notranslate\" title=\"\">\r\n#define LEN (10 * 4096)\r\n\r\nint main(void)\r\n{\r\n\tint fd, ret = 0;\r\n\tchar *vadr;\r\n\tint i;\r\n\r\n\tif ((fd = open(&quot;\/dev\/mapdrv_k&quot;, O_RDWR)) &lt; 0) {\r\n\t\tperror(&quot;open&quot;);\r\n\t\tret = -1;\r\n\t\tgoto fail;\r\n\t}\r\n\tvadr = mmap(0, LEN, PROT_READ, MAP_PRIVATE | MAP_NORESERVE, fd, 0);\r\n\r\n\tif (vadr == MAP_FAILED) {\r\n\t\tperror(&quot;mmap&quot;);\r\n\t\tret = -1;\r\n\t\tgoto fail_close;\r\n\t}\r\n\r\n\tprintf(&quot;%s\\n&quot;, vadr);\r\n\r\n\tif (-1 == munmap(vadr, LEN))\r\n\t\tret = -1;\r\nfail_close:\r\n\tclose(fd);\r\nfail:\r\n\texit(ret);\r\n}\r\n<\/pre>\n<p>\u7528\u6237\u6001\u7a0b\u5e8f\u7684\u5b9e\u73b0\u5e76\u4e0d\u590d\u6742\uff0c\u56e0\u4e3a\u5b83\u7684\u4e3b\u8981\u4f5c\u7528\u662f\u5bf9\u5185\u6838\u6a21\u5757\u7a0b\u5e8f\u7684\u6d4b\u8bd5\u3002\u7531\u4e8e\u7528\u6237\u6001\u7a0b\u5e8f\u662f\u5bf9\u7279\u5b9a\u7684\u5b57\u7b26\u8bbe\u5907\u6587\u4ef6mapdrv\u8fdb\u884c\u64cd\u4f5c\uff0c\u6240\u4ee5\u7a0b\u5e8f\u4e2d\u6240\u4f7f\u7528\u7684\u7cfb\u7edf\u8c03\u7528\u5c06\u4f1a\u8c03\u7528file_operations\u7ed3\u6784\u4e2d\u5bf9\u5e94\u7684\u94a9\u5b50\u51fd\u6570\u3002\u6bd4\u5982mmap\u7cfb\u7edf\u8c03\u7528\u5728\u6267\u884c\u65f6\u4f1a\u8c03\u7528mapdrv\u8bbe\u5907\u9a71\u52a8\u4e2d\u7684mmap\u94a9\u5b50\u51fd\u6570\uff0c\u867d\u7136\u4e24\u8005\u540c\u540d\uff0c\u4f46\u662fmmap\u94a9\u5b50\u51fd\u6570\u6240\u5b9e\u73b0\u7684\u529f\u80fd\u53ea\u662fmmap\u7cfb\u7edf\u8c03\u7528\u6267\u884c\u8fc7\u7a0b\u4e2d\u7684\u4e00\u90e8\u95e8\uff0c\u8be5\u94a9\u5b50\u51fd\u6570\u662ffile_operations\u7ed3\u6784\u4e2d\u7684\u6210\u5458\u3002\u4e24\u8005\u7684\u51fd\u6570\u539f\u578b\u5982\u4e0b\uff1a<\/p>\n<pre class=\"brush: cpp; title: ; notranslate\" title=\"\">\r\nvoid *mmap(void *addr, size_t length, int prot, int flags, int fd, off_t offset);\r\nint (*mmap) (struct file *, struct vm_area_struct *);\r\n<\/pre>\n<p>\u5982\u4f55\u5b9e\u4f8b\u5316open\u548cmmap\u7b49\u94a9\u5b50\u51fd\u6570\u4fbf\u662f\u6574\u4e2a\u5185\u6838\u6a21\u5757\u7a0b\u5e8f\u5b9e\u73b0\u7684\u5173\u952e\u3002<\/p>\n<h3>3.\u5b57\u7b26\u8bbe\u5907\u9a71\u52a8\u7a0b\u5e8f\u7684\u5b9e\u73b0<\/h3>\n<p>\u6574\u4e2a\u5185\u6838\u6a21\u5757\u7a0b\u5e8f\u662f\u4ee5\u5b57\u7b26\u8bbe\u5907\u9a71\u52a8\u4e3a\u57fa\u7840\u8fdb\u884c\u5b9e\u73b0\u7684\u3002\u8be5\u7a0b\u5e8f\u6a21\u5757\u52a0\u8f7d\u51fd\u6570\u4e0e\u4e00\u822c\u5b57\u7b26\u8bbe\u5907\u9a71\u52a8\u7a0b\u5e8f\u5b8c\u6210\u7684\u5de5\u4f5c\u4e00\u81f4\uff1a<\/p>\n<p>1.\u7533\u8bf7\u8bbe\u5907\u53f7\uff1b<\/p>\n<p>2.\u4e3a\u63cf\u8ff0\u5b57\u7b26\u8bbe\u5907\u7684\u6570\u636e\u7ed3\u6784\u5206\u914d\u7a7a\u95f4\uff0c\u5e76\u8fdb\u884c\u521d\u59cb\u5316\uff1b<\/p>\n<p>3.\u5c06\u8be5\u5b57\u7b26\u8bbe\u5907\u6ce8\u518c\u5230\u5185\u6838\u4e2d\uff1b<\/p>\n<p>\u5728\u672c\u6587\u6240\u63cf\u8ff0\u7684\u5b9e\u9a8c\u4e2d\uff0c\u6a21\u5757\u52a0\u8f7d\u51fd\u6570\u9664\u4e86\u5b8c\u6210\u4e0a\u8ff0\u529f\u80fd\uff0c\u8fd8\u8981\u5b8c\u6210\u4ee5\u4e0b\u529f\u80fd\uff1a<\/p>\n<pre class=\"brush: cpp; title: ; notranslate\" title=\"\">\r\n\tkmalloc_area = kmalloc(MAPLEN, GFP_KERNEL);\r\n\tif (!kmalloc_area)\r\n\t\tgoto fail4;\r\n\r\n\tfor (page = virt_to_page(kmalloc_area);\r\n\t\t\tpage &lt; virt_to_page(kmalloc_area + MAPLEN); page++) {\r\n\t\tSetPageReserved(page);\r\n\t}\r\n<\/pre>\n<p>\u9996\u5148\uff0c\u901a\u8fc7kmalloc()\u5206\u914d\u4e00\u5757\u5185\u5b58\u7528\u4e8e\u5728\u5185\u6838\u7a7a\u95f4\u4fdd\u5b58\u6570\u636e\uff1b\u901a\u8fc7SetPageReserved()\u5c06\u7f13\u5b58\u6570\u636e\u7684\u9875\u9762\u5e38\u9a7b\u5185\u5b58\uff0c\u9632\u6b62\u88ab\u6362\u51fa\u5230\u78c1\u76d8\uff1b\u5c06\u4e00\u6bb5\u5b57\u7b26\u4e32\u62f7\u8d1d\u5230\u8fd9\u7247\u5185\u5b58\u4e2d\u3002\u5b8c\u6210\u521d\u59cb\u5316\u51fd\u6570\u540e\uff0c\u5b57\u7b26\u8bbe\u5907\u9a71\u52a8\u4e2d\u6700\u91cd\u8981\u7684\u5c31\u662f\u5b9e\u73b0file_operations\u7ed3\u6784\u4e2d\u7684\u94a9\u5b50\u51fd\u6570\u3002\u5728\u672c\u6587\u6240\u8ff0\u7684\u5b9e\u9a8c\u4e2d\uff0c\u6211\u4eec\u53ea\u9700\u5b9e\u73b0\u4e09\u4e2a\u94a9\u5b50\u51fd\u6570\u3002<\/p>\n<pre class=\"brush: cpp; title: ; notranslate\" title=\"\">\r\nstatic struct file_operations mapdrv_fops = {\r\n\t.owner = THIS_MODULE,\r\n\t.mmap = mapdrv_mmap,\r\n\t.open = mapdrv_open,\r\n\t.release = mapdrv_release,\r\n};\r\n\r\nint mapdrv_open(struct inode *inode, struct file *file)\r\n{\r\n\tstruct mapdrv *md;\r\n\r\n\tprintk(&quot;device is opened..\\n&quot;);\r\n\tmd = container_of(inode-&gt;i_cdev, struct mapdrv, mapdev);\r\n\tatomic_inc(&amp;md-&gt;usage);\r\n\treturn 0;\r\n}\r\n\r\nint mapdrv_release(struct inode *inode, struct file *file)\r\n{\r\n        struct mapdrv* md;\r\n\r\n        printk(&quot;device is closed..\\n&quot;);\r\n        md = container_of(inode-&gt;i_cdev, struct mapdrv, mapdev);\r\n        atomic_dec(&amp;md-&gt;usage);\r\n        return 0;\r\n}\r\n<\/pre>\n<p>\u53ef\u4ee5\u770b\u5230\uff0copen\u548crelease\u94a9\u5b50\u51fd\u6570\u7684\u5b9e\u73b0\u5341\u5206\u7b80\u5355\uff0c\u53ea\u662f\u6253\u5370\u76f8\u5e94\u8bed\u53e5\u4ee5\u53ca\u66f4\u65b0\u8bbe\u5907\u7684\u5f15\u7528\u8ba1\u6570\u3002\u4e8b\u5b9e\u4e0a\uff0c\u6211\u4eec\u4e0d\u5b9e\u73b0\u8fd9\u4e24\u4e2a\u94a9\u5b50\u51fd\u6570\u5bf9\u6574\u4e2a\u9a71\u52a8\u7a0b\u5e8f\u4e5f\u6ca1\u6709\u4efb\u4f55\u5f71\u54cd\u3002\u56e0\u4e3a\u4ed6\u4eec\u5206\u522b\u5728open\u548cclose\u7cfb\u7edf\u8c03\u7528\u6267\u884c\u7684\u8fc7\u7a0b\u4e2d\u88ab\u8c03\u7528\uff0c\u800c\u8fd9\u4e24\u4e2a\u7cfb\u7edf\u8c03\u7528\u5df2\u7ecf\u5b8c\u6210\u4e86\u6253\u5f00\u6587\u4ef6\u548c\u5173\u95ed\u6587\u4ef6\u7684\u6240\u6709\u5de5\u4f5c\u3002\u56e0\u6b64\uff0copen\u548crelease\u94a9\u5b50\u51fd\u6570\u53ea\u662f\u6253\u5370\u4e00\u4e9b\u65e5\u5fd7\u4fe1\u606f\uff0c\u65b9\u4fbf\u7528\u6237\u67e5\u770b\u3002\u56e0\u6b64\uff0c\u540c\u540d\u7684\u94a9\u5b50\u51fd\u6570\u548c\u7cfb\u7edf\u8c03\u7528\u5e76\u4e0d\u662f\u7b49\u4ef7\u7684\u5173\u7cfb\u3002<\/p>\n<h3>4.\u901a\u8fc7fault()\u5b9e\u73b0\u5185\u5b58\u6620\u5c04<\/h3>\n<p>mmap\u7cfb\u7edf\u8c03\u7528\u662f\u5c06\u672c\u5730\u6587\u4ef6\u6620\u5c04\u5230\u8fdb\u7a0b\u7684\u7528\u6237\u7a7a\u95f4\uff0c\u5982\u679c\u6267\u884c\u6210\u529f\uff0c\u8fdb\u7a0b\u7684\u5730\u5740\u7a7a\u95f4\u4e2d\u4f1a\u65b0\u589e\u4e00\u5757\u865a\u62df\u5185\u5b58\u533a\u57df\uff08\u4f46\u5e76\u4e0d\u662f\u6bcf\u6b21\u8c03\u7528mmap()\u90fd\u4f1a\u589e\u52a0\u4e00\u4e2avma\uff0c\u56e0\u4e3a\u53ef\u80fd\u4f1a\u51fa\u73b0\u5185\u5b58\u533a\u57df\u4e4b\u95f4\u7684\u5408\u5e76\uff09<\/p>\n<p>mmap\u94a9\u5b50\u51fd\u6570\u7684\u56de\u8c03\u53ea\u662f\u6574\u4e2a\u7cfb\u7edf\u8c03\u7528\u6267\u884c\u8fc7\u7a0b\u4e2d\u7684\u4e00\u90e8\u5206\uff0c\u8fd9\u4e2a\u94a9\u5b50\u51fd\u6570\u5b8c\u6210\u7684\u4e3b\u8981\u529f\u80fd\u662f\u5c06\u65b0\u589e\u7684vma\u4e2d\u7684\u64cd\u4f5c\u96c6\u8fdb\u884c\u5b9e\u4f8b\u5316\u3002\u5177\u4f53\u5b9e\u73b0\u4ee3\u7801\u5982\u4e0b\uff1a<\/p>\n<pre class=\"brush: cpp; title: ; notranslate\" title=\"\">\r\nint mapdrv_mmap(struct file *file, struct vm_area_struct *vma)\r\n{\r\n\tunsigned long offset = vma-&gt;vm_pgoff &lt;&lt; PAGE_SHIFT;\r\n\r\n\tunsigned long size = vma-&gt;vm_end - vma-&gt;vm_start;\r\n\tif (offset &amp; ~PAGE_MASK) {\r\n\t\tprintk(&quot;offset not aligned: %ld\\n&quot;, offset);\r\n\t\treturn -ENXIO;\r\n\t}\r\n\tif (size &gt; MAPLEN) {\r\n\t\tprintk(&quot;size too big\\n&quot;);\r\n\t\treturn -ENXIO;\r\n\t}\r\n\r\n\tif ((vma-&gt;vm_flags &amp; VM_WRITE) &amp;&amp; !(vma-&gt;vm_flags &amp; VM_SHARED)) {\r\n\t\tprintk(&quot;writeable mappings must be shared, rejecting\\n&quot;);\r\n\t\treturn -EINVAL;\r\n\t}\r\n\r\n\tvma-&gt;vm_flags |= VM_LOCKED;\r\n\tif (offset == 0) {\r\n\t\tvma-&gt;vm_ops = &amp;map_vm_ops;\r\n\t\tmap_vopen(vma);\r\n\t} else {\r\n\t\tprintk(&quot;offset out of range\\n&quot;);\r\n\t\treturn -ENXIO;\r\n\t}\r\n\treturn 0;\r\n}\r\n<\/pre>\n<p>\u9996\u5148\uff0coffset\u4e2d\u4fdd\u5b58\u6620\u5c04\u7684\u9996\u9875\u5728\u6587\u4ef6\u4e2d\u7684\u504f\u79fb\u91cf\uff0c\u8be5\u504f\u79fb\u91cf\u5fc5\u987b\u662f\u9875\u5927\u5c0f\u7684\u6574\u6570\u500d\uff0c\u5426\u5219\u5c06\u4e0d\u80fd\u8fdb\u884c\u6620\u5c04\u3002\u8fd9\u4e00\u70b9\u5728\u5b9e\u73b0\u4e0a\u5c06offset\u4e0ePAGE_MASK\u5b8f\u8fdb\u884c\u4f4d\u8fd0\u7b97\u5373\u53ef\u5224\u65ad\u3002\u63a5\u7740\uff0c\u5224\u65ad\u6620\u5c04\u533a\u57df\u7684\u957f\u5ea6\u662f\u5426\u8d85\u51fa\u4e86\u672c\u5b9e\u9a8c\u4e2d\u9884\u8bbe\u7684\u957f\u5ea6\u5927\u5c0f\u3002<\/p>\n<p>\u5982\u679c\u4e0a\u8ff0\u4e24\u4e2a\u6761\u4ef6\u90fd\u5408\u6cd5\uff0c\u90a3\u4e48\u63a5\u4e0b\u6765\u5c06\u8fdb\u884c\u6700\u4e3a\u91cd\u8981\u7684\u64cd\u4f5c\uff0c\u5c06vma\u4e2d\u7684\u64cd\u4f5c\u96c6\u8fdb\u884c\u5b9e\u4f8b\u5316\u3002vma\u7684\u64cd\u4f5c\u96c6\u5c31\u662f\u4e13\u95e8\u5bf9\u6240\u5c5evma\u8fdb\u884c\u64cd\u4f5c\u7684\u94a9\u5b50\u51fd\u6570\u96c6\u5408\uff0c\u5185\u6838\u4e2d\u901a\u8fc7vm_operations_struct\u7ed3\u6784\u5bf9\u5176\u63cf\u8ff0\uff1a<\/p>\n<pre class=\"brush: cpp; title: ; notranslate\" title=\"\">\r\nstruct vm_operations_struct {\r\n        void (*open)(struct vm_area_struct * area);\r\n        void (*close)(struct vm_area_struct * area);\r\n        int (*fault)(struct vm_area_struct *vma, struct vm_fault *vmf);\r\n        \u2026\u2026\r\n}\r\n<\/pre>\n<p>\u53c2\u8003\u4e0a\u8ff0\u4ee3\u7801\uff0c\u5177\u4f53\u7684\u5b9e\u4f8b\u5316\u64cd\u4f5c\u5c31\u662f\u5b9a\u4e49\u8be5\u7c7b\u578b\u7684\u53d8\u91cfmap_vm_ops\uff0c\u5b9e\u73b0\u6240\u9700\u94a9\u5b50\u51fd\u6570\uff0c\u5e76\u5c06\u8be5\u53d8\u91cf\u4e0evm\u4e2d\u7684\u64cd\u4f5c\u96c6\u5b57\u6bb5\u8fdb\u884c\u6302\u63a5\u3002<\/p>\n<p>\u6211\u4eec\u8fd9\u91cc\u7528\u5230\u7684\u4e3b\u8981\u6709\u4ee5\u4e0b\u4e09\u4e2a\u94a9\u5b50\u51fd\u6570\uff1a<\/p>\n<p>open\uff1a\u5f53\u6307\u5b9a\u7684vma\u52a0\u5165\u5230\u4e00\u4e2a\u5730\u5740\u7a7a\u95f4\u65f6\uff0c\u8be5\u51fd\u6570\u88ab\u8c03\u7528\u3002<\/p>\n<p>close\uff1a\u5f53\u6307\u5b9a\u7684vma\u4ece\u5730\u5740\u7a7a\u95f4\u5220\u9664\u65f6\uff0c\u8be5\u51fd\u6570\u88ab\u8c03\u7528\u3002<\/p>\n<p>fault\uff1a\u5f53\u8981\u8bbf\u95ee\u7684\u9875\u4e0d\u518d\u7269\u7406\u5185\u5b58\u65f6\uff0c\u8be5\u51fd\u6570\u88ab\u7f3a\u9875\u5904\u7406\u7a0b\u5e8f\u8c03\u7528\u3002<\/p>\n<p>\u8fd9\u4e09\u4e2a\u94a9\u5b50\u51fd\u6570\u7684\u5b9e\u73b0\u4ee3\u7801\u5982\u4e0b\uff1a<\/p>\n<pre class=\"brush: cpp; title: ; notranslate\" title=\"\">\r\nstatic struct vm_operations_struct map_vm_ops = {\r\n\t.open = map_vopen,\r\n\t.close = map_vclose,\r\n\t.fault = map_fault,\r\n};\r\n\r\nvoid map_vopen(struct vm_area_struct *vma)\r\n{\r\n\tprintk(&quot;mapping vma is opened..\\n&quot;);\r\n}\r\n\r\nvoid map_vclose(struct vm_area_struct *vma)\r\n{\r\n\tprintk(&quot;mapping vma is closed..\\n&quot;);\r\n}\r\n<\/pre>\n<p>\u53ef\u4ee5\u770b\u5230\uff0cvma\u7684open\u548cclose\u4e24\u4e2a\u94a9\u5b50\u51fd\u6570\u6ca1\u6709\u505a\u4ec0\u4e48\u5177\u4f53\u5de5\u4f5c\uff0c\u56e0\u4e3a\u6253\u5f00\u548c\u5173\u95ed\u4e00\u4e2avma\u7684\u5de5\u4f5c\u5168\u90e8\u7531\u5185\u6838\u8d1f\u8d23\uff0c\u4f46\u662f\u5728mmap\u94a9\u5b50\u51fd\u6570\u4e2d\u6211\u4eec\u5fc5\u987b\u663e\u793a\u7684\u8c03\u7528map_open()\u3002<\/p>\n<p>\u8fd9\u91cc\u6211\u4eec\u91cd\u70b9\u8bf4\u660efalut\u94a9\u5b50\u51fd\u6570\u7684\u5b9e\u73b0\u3002\u5f53\u7528\u6237\u8981\u8bbf\u95eevma\u4e2d\u7684\u9875\uff0c\u800c\u8be5\u9875\u53c8\u4e0d\u5728\u5185\u5b58\u65f6\uff0c\u5c06\u53d1\u751f\u7f3a\u9875\u5f02\u5e38\uff0cfault\u94a9\u5b50\u51fd\u6570\u4f1a\u5728\u6574\u4e2a\u7f3a\u9875\u5904\u7406\u7a0b\u5e8f\u4e2d\u88ab\u8c03\u7528\u3002\u6574\u4e2a\u8fc7\u7a0b\u5927\u81f4\u5982\u4e0b\uff1a<\/p>\n<p>1.\u627e\u5230\u7f3a\u9875\u5730\u5740\u6240\u5728\u7684vma\u3002<\/p>\n<p>2.\u5982\u679c\u6709\u5fc5\u8981\u5206\u914d\u5404\u7ea7\u9875\u8868\u9879\u3002<\/p>\n<p>3.\u5982\u679c\u9875\u8868\u9879\u5bf9\u5e94\u7684\u7269\u7406\u9875\u9762\u4e0d\u5b58\u5728\uff0c\u5219\u56de\u8c03\u5f53\u524dvma\u4e2d\u7684fault\u94a9\u5b50\u51fd\u6570\uff0c\u5b83\u8fd4\u56de\u7269\u7406\u9875\u9762\u63cf\u8ff0\u7b26\u3002<\/p>\n<p>4.\u5c06\u7269\u7406\u9875\u9762\u5730\u5740\u586b\u5145\u5230\u76f8\u5e94\u9875\u8868\u9879\u4e2d\u3002<\/p>\n<p>5.\u5b8c\u6bd5\u3002<\/p>\n<p>\u53ef\u4ee5\u770b\u5230\uff0cfault\u94a9\u5b50\u51fd\u6570\u6240\u5b9e\u73b0\u7684\u4e3b\u8981\u529f\u80fd\u5c31\u662f\u8fd4\u56de\u6240\u9700\u7684\u7269\u7406\u5185\u5b58\u63cf\u8ff0\u7b26\u3002<\/p>\n<p>\u6839\u636e\u672c\u6587\u7b2c\u4e00\u90e8\u5206\u6240\u63cf\u8ff0\u5b9e\u73b0\u539f\u7406\uff0c\u6211\u4eec\u901a\u8fc7kmalloc()\u5206\u914d\u4e00\u5757\u865a\u62df\u5185\u5b58\uff0c\u53ef\u4ee5\u901a\u8fc7virt_to_page()\u83b7\u5f97\u8be5\u865a\u62df\u5185\u5b58\u5bf9\u5e94\u7684\u7269\u7406\u9875\u6846\u63cf\u8ff0\u7b26\uff0c\u6700\u540e\u5c06\u8be5\u7269\u7406\u9875\u6846\u63cf\u8ff0\u7b26\u8fd4\u56de\u5230\u7f3a\u9875\u5f02\u5e38\u5904\u7406\u7a0b\u5e8f\u4e2d\u3002\u81f3\u4e8e\u7528\u6237\u9875\u8868\u7684\u66f4\u65b0\uff0c\u90a3\u662f\u7f3a\u9875\u5f02\u5e38\u5904\u7406\u7a0b\u5e8f\u8d1f\u8d23\u7684\u4e8b\u60c5\uff0c\u6211\u4eec\u4e0d\u5fc5\u7406\u4f1a\u3002<\/p>\n<pre class=\"brush: cpp; title: ; notranslate\" title=\"\">\r\nint map_fault(struct vm_area_struct *vma, struct vm_fault *vmf)\r\n{\r\n\tstruct page *page = virt_to_page(kmalloc_area);\r\n\r\n\tget_page(page);\r\n\tvmf-&gt;page = page;\r\n\tprintk(&quot;the requiring page is returned..\\n&quot;);\r\n\r\n\treturn 0;\r\n}\r\n<\/pre>\n<p>\u901a\u8fc7\u4e0a\u8ff0\u5b9e\u73b0\u8fc7\u7a0b\uff0c\u6211\u4eec\u5c31\u5c06\u7528\u6237\u865a\u62df\u5730\u5740A\u548c\u5185\u6838\u865a\u62df\u5730\u5740B\u6620\u5c04\u5230\u4e86\u540c\u4e00\u7684\u7269\u7406\u5185\u5b58\u4e0a\uff0c\u4ece\u800c\u5b9e\u73b0\u8fdb\u7a0b\u8bbf\u95ee\u7528\u6237\u5730\u5740\u65f6\u76f4\u63a5\u83b7\u5f97\u5185\u6838\u6570\u636e\u7684\u529f\u80fd\u3002<\/p>\n<p>\u672c\u5b9e\u9a8c\u6d89\u53ca\u7684\u77e5\u8bc6\u70b9\u6bd4\u8f83\u591a\uff0c\u6bd4\u5982\u5b57\u7b26\u8bbe\u5907\u9a71\u52a8\u7a0b\u5e8f\u7684\u57fa\u672c\u6a21\u578b\uff0cLinux\u5185\u5b58\u7ba1\u7406\u7b49\u76f8\u5173\u77e5\u8bc6\u3002\u611f\u5174\u8da3\u7684\u7ae5\u978b\u53ef\u4ee5\u53c2\u8003\uff1a<\/p>\n<p>1.\u5185\u6838\u4e4b\u65c5\u7f51\u7ad9\uff0c<a href=\"http:\/\/www.kerneltravel.net\/journal\/v\/mem.htm\">http:\/\/www.kerneltravel.net\/journal\/v\/mem.htm<\/a><\/p>\n<p>2.Linux\u8bbe\u5907\u9a71\u52a8\u7a0b\u5e8f\uff0c\u7b2c\u5341\u4e94\u7ae0<\/p>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u5185\u6838\u6001\u4e0e\u7528\u6237\u6001\u8fdb\u884c\u6570\u636e\u4ea4\u4e92\u901a\u5e38\u662f\u8fd9\u6837\u4e00\u79cd\u6a21\u578b\uff1a\u5185\u6838\u5229\u7528\u81ea\u8eab\u7684\u7279\u6743\u901a\u8fc7\u7279\u5b9a\u7684\u670d\u52a1\u7a0b\u5e8f\u91c7\u96c6\u3001\u63a5\u6536\u548c\u5904\u7406\u6570\u636e\uff1b\u63a5\u7740\uff0c [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[266],"tags":[297,407,335],"class_list":["post-3993","post","type-post","status-publish","format-standard","hentry","category-266","tag-297","tag-407","tag-335"],"views":20219,"_links":{"self":[{"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/posts\/3993","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/comments?post=3993"}],"version-history":[{"count":0,"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/posts\/3993\/revisions"}],"wp:attachment":[{"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/media?parent=3993"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/categories?post=3993"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/tags?post=3993"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}