{"id":46,"date":"2024-06-17T21:13:10","date_gmt":"2024-06-17T13:13:10","guid":{"rendered":"https:\/\/www.swreader.com\/?p=46"},"modified":"2024-06-17T21:16:55","modified_gmt":"2024-06-17T13:16:55","slug":"linux-kernel-system-call-%e6%b5%81%e7%a8%8b%e5%88%86%e6%9e%90","status":"publish","type":"post","link":"https:\/\/www.swreader.com\/index.php\/2024\/06\/17\/linux-kernel-system-call-%e6%b5%81%e7%a8%8b%e5%88%86%e6%9e%90\/","title":{"rendered":"Linux Kernel System Call \u6d41\u7a0b\u5206\u6790"},"content":{"rendered":"<p>\u7cfb\u7edf\u8c03\u7528\u662f\u7528\u6237\u6001\u7a0b\u5e8f\u4e0e\u64cd\u4f5c\u7cfb\u7edf\u5185\u6838\u4e4b\u95f4\u4ea4\u4e92\u7684\u91cd\u8981\u673a\u5236\uff0c\u901a\u8fc7\u7cfb\u7edf\u8c03\u7528\uff0c\u7528\u6237\u7a0b\u5e8f\u53ef\u4ee5\u8bf7\u6c42\u5185\u6838\u6267\u884c\u7279\u6743\u64cd\u4f5c\uff0c\u5982\u6587\u4ef6\u64cd\u4f5c\u3001\u8fdb\u7a0b\u7ba1\u7406\u548c\u7f51\u7edc\u901a\u4fe1\u7b49\u3002\u672c\u6587\u5c06\u8be6\u7ec6\u8bf4\u660eLinux\u5185\u6838\u4e2d\u7cfb\u7edf\u8c03\u7528\u7684\u6267\u884c\u8fc7\u7a0b\uff0c\u5e76\u6df1\u5165\u63a2\u8ba8\u5176\u4e2d\u7684\u7ec6\u8282\u3002<\/p>\n<h2>\u7cfb\u7edf\u8c03\u7528\u6982\u8ff0<\/h2>\n<p>\u7cfb\u7edf\u8c03\u7528\uff08System Call\uff09\u662f\u7528\u6237\u6001\u7a0b\u5e8f\u4e0e\u5185\u6838\u901a\u4fe1\u7684\u4e3b\u8981\u63a5\u53e3\u3002\u4e0e\u666e\u901a\u7684\u51fd\u6570\u8c03\u7528\u4e0d\u540c\uff0c\u7cfb\u7edf\u8c03\u7528\u9700\u8981\u4ece\u7528\u6237\u6001\u5207\u6362\u5230\u5185\u6838\u6001\uff0c\u4ece\u800c\u4f7f\u7528\u6237\u7a0b\u5e8f\u80fd\u591f\u6267\u884c\u7279\u6743\u64cd\u4f5c\u3002<\/p>\n<h2>\u7cfb\u7edf\u8c03\u7528\u7684\u57fa\u672c\u6d41\u7a0b<\/h2>\n<p>\u7cfb\u7edf\u8c03\u7528\u7684\u6267\u884c\u8fc7\u7a0b\u4e3b\u8981\u5305\u62ec\u4ee5\u4e0b\u51e0\u4e2a\u6b65\u9aa4\uff1a<\/p>\n<ol>\n<li>\u7528\u6237\u6001\u7a0b\u5e8f\u53d1\u8d77\u7cfb\u7edf\u8c03\u7528\u3002<\/li>\n<li>\u5207\u6362\u5230\u5185\u6838\u6001\u3002<\/li>\n<li>\u5185\u6838\u5904\u7406\u7cfb\u7edf\u8c03\u7528\u3002<\/li>\n<li>\u8fd4\u56de\u5230\u7528\u6237\u6001\u3002<\/li>\n<\/ol>\n<p>\u4e0b\u9762\uff0c\u6211\u4eec\u5c06\u8be6\u7ec6\u8ba8\u8bba\u6bcf\u4e2a\u6b65\u9aa4\u7684\u5177\u4f53\u5b9e\u73b0\u548c\u7ec6\u8282\u3002<\/p>\n<h3>1. \u7528\u6237\u6001\u7a0b\u5e8f\u53d1\u8d77\u7cfb\u7edf\u8c03\u7528<\/h3>\n<p>\u7528\u6237\u7a0b\u5e8f\u901a\u8fc7\u8c03\u7528C\u6807\u51c6\u5e93\u4e2d\u7684\u5c01\u88c5\u51fd\u6570\u6765\u53d1\u8d77\u7cfb\u7edf\u8c03\u7528\u3002\u8fd9\u4e9b\u51fd\u6570\u901a\u5e38\u5728<code>glibc<\/code>\u5e93\u4e2d\u5b9e\u73b0\u3002\u4ee5<code>read()<\/code>\u51fd\u6570\u4e3a\u4f8b\uff0c\u7528\u6237\u7a0b\u5e8f\u53ef\u80fd\u4f1a\u8fd9\u6837\u8c03\u7528\uff1a<\/p>\n<pre><code class=\"language-c\">ssize_t bytes_read = read(file_descriptor, buffer, count);<\/code><\/pre>\n<p>\u5728<code>glibc<\/code>\u5e93\u4e2d\uff0c<code>read()<\/code>\u51fd\u6570\u7684\u5b9e\u73b0\u4f1a\u901a\u8fc7<code>syscall<\/code>\u51fd\u6570\u5b9e\u9645\u6267\u884c\u7cfb\u7edf\u8c03\u7528\uff1a<\/p>\n<pre><code class=\"language-c\">ssize_t read(int fd, void *buf, size_t count) {\n    return syscall(SYS_read, fd, buf, count);\n}<\/code><\/pre>\n<p><code>SYS_read<\/code>\u662f\u7cfb\u7edf\u8c03\u7528\u53f7\uff0c\u5728\u5934\u6587\u4ef6<code>unistd.h<\/code>\u4e2d\u5b9a\u4e49\uff1a<\/p>\n<pre><code class=\"language-c\">#define SYS_read 0<\/code><\/pre>\n<h3>2. \u5207\u6362\u5230\u5185\u6838\u6001<\/h3>\n<p>\u7528\u6237\u6001\u901a\u8fc7\u7279\u5b9a\u7684\u6307\u4ee4\uff08\u5982<code>syscall<\/code>\u6307\u4ee4\uff09\u5c06\u7cfb\u7edf\u8c03\u7528\u53f7\u548c\u53c2\u6570\u4f20\u9012\u7ed9\u5185\u6838\uff0c\u5e76\u89e6\u53d1\u4e00\u4e2a\u9677\u9631\uff08trap\uff09\uff0c\u5bfc\u81f4CPU\u5207\u6362\u5230\u5185\u6838\u6001\u3002\u4ee5\u4e0b\u662f<code>syscall<\/code>\u6307\u4ee4\u7684\u793a\u4f8b\uff1a<\/p>\n<pre><code class=\"language-c\">ssize_t result;\nasm volatile (\n    &quot;syscall&quot;                        \/\/ \u53d1\u8d77\u7cfb\u7edf\u8c03\u7528\n    : &quot;=a&quot; (result)                  \/\/ \u8fd4\u56de\u503c\u5b58\u653e\u5728rax\u5bc4\u5b58\u5668\u4e2d\n    : &quot;a&quot; (SYS_read),                \/\/ \u7cfb\u7edf\u8c03\u7528\u53f7\u653e\u5728rax\u5bc4\u5b58\u5668\u4e2d\n      &quot;D&quot; (file_descriptor),         \/\/ \u7b2c\u4e00\u4e2a\u53c2\u6570\u653e\u5728rdi\u5bc4\u5b58\u5668\u4e2d\n      &quot;S&quot; (buffer),                  \/\/ \u7b2c\u4e8c\u4e2a\u53c2\u6570\u653e\u5728rsi\u5bc4\u5b58\u5668\u4e2d\n      &quot;d&quot; (count)                    \/\/ \u7b2c\u4e09\u4e2a\u53c2\u6570\u653e\u5728rdx\u5bc4\u5b58\u5668\u4e2d\n    : &quot;rcx&quot;, &quot;r11&quot;, &quot;memory&quot;\n);<\/code><\/pre>\n<p>\u8fd9\u6bb5\u4ee3\u7801\u4e2d\uff0c<code>syscall<\/code>\u6307\u4ee4\u4f1a\u5bfc\u81f4\u5904\u7406\u5668\u8fdb\u5165\u5185\u6838\u6001\uff0c\u5e76\u8df3\u8f6c\u5230\u5185\u6838\u4e2d\u5bf9\u5e94\u7684\u7cfb\u7edf\u8c03\u7528\u5904\u7406\u7a0b\u5e8f\u3002<\/p>\n<h3>3. \u5185\u6838\u5904\u7406\u7cfb\u7edf\u8c03\u7528<\/h3>\n<p>\u8fdb\u5165\u5185\u6838\u6001\u540e\uff0cCPU\u4f1a\u6839\u636e\u7cfb\u7edf\u8c03\u7528\u53f7\u67e5\u627e\u76f8\u5e94\u7684\u5185\u6838\u5904\u7406\u51fd\u6570\u3002\u5728Linux\u5185\u6838\u4e2d\uff0c\u7cfb\u7edf\u8c03\u7528\u53f7\u548c\u5904\u7406\u51fd\u6570\u7684\u5bf9\u5e94\u5173\u7cfb\u5b58\u50a8\u5728\u4e00\u4e2a\u7cfb\u7edf\u8c03\u7528\u8868\u4e2d\u3002\u8fd9\u5f20\u8868\u5728\u5185\u6838\u521d\u59cb\u5316\u65f6\u88ab\u586b\u5145\uff0c\u5305\u542b\u6240\u6709\u652f\u6301\u7684\u7cfb\u7edf\u8c03\u7528\u51fd\u6570\u6307\u9488\u3002<\/p>\n<p>\u4ee5\u4e0b\u662f\u4e00\u4e2a\u7b80\u5316\u7684\u7cfb\u7edf\u8c03\u7528\u8868\u793a\u4f8b\uff1a<\/p>\n<pre><code class=\"language-c\">extern void *sys_call_table[];\n\nasmlinkage long sys_read(unsigned int fd, char __user *buf, size_t count);\n\nvoid *sys_call_table[] = {\n    [SYS_read] = sys_read,\n    \/\/ \u5176\u4ed6\u7cfb\u7edf\u8c03\u7528\n};<\/code><\/pre>\n<p>\u5f53CPU\u6267\u884c<code>syscall<\/code>\u6307\u4ee4\u65f6\uff0c\u5185\u6838\u4f1a\u901a\u8fc7\u7cfb\u7edf\u8c03\u7528\u53f7\u67e5\u627e<code>sys_call_table<\/code>\uff0c\u627e\u5230\u5bf9\u5e94\u7684\u5904\u7406\u51fd\u6570\u5e76\u6267\u884c\u3002\u4f8b\u5982\uff0c\u5bf9\u4e8e<code>read<\/code>\u7cfb\u7edf\u8c03\u7528\uff0c\u5185\u6838\u4f1a\u8c03\u7528<code>sys_read<\/code>\u51fd\u6570\uff1a<\/p>\n<pre><code class=\"language-c\">asmlinkage long sys_read(unsigned int fd, char __user *buf, size_t count) {\n    \/\/ \u5185\u6838\u5b9e\u73b0\u7684\u8bfb\u53d6\u64cd\u4f5c\n    struct file *file;\n    ssize_t ret;\n\n    file = fget(fd);\n    if (!file) {\n        return -EBADF;\n    }\n\n    ret = vfs_read(file, buf, count, &amp;file-&gt;f_pos);\n    fput(file);\n\n    return ret;\n}<\/code><\/pre>\n<p><code>sys_read<\/code>\u51fd\u6570\u9996\u5148\u68c0\u67e5\u6587\u4ef6\u63cf\u8ff0\u7b26\u662f\u5426\u6709\u6548\uff0c\u7136\u540e\u8c03\u7528<code>vfs_read<\/code>\u51fd\u6570\u6267\u884c\u5b9e\u9645\u7684\u6587\u4ef6\u8bfb\u53d6\u64cd\u4f5c\u3002<code>vfs_read<\/code>\u51fd\u6570\u662f\u865a\u62df\u6587\u4ef6\u7cfb\u7edf\uff08VFS\uff09\u5c42\u7684\u4e00\u90e8\u5206\uff0c\u8d1f\u8d23\u4e0e\u5177\u4f53\u7684\u6587\u4ef6\u7cfb\u7edf\u4ea4\u4e92\u3002<\/p>\n<h3>4. \u8fd4\u56de\u7528\u6237\u6001<\/h3>\n<p>\u7cfb\u7edf\u8c03\u7528\u5904\u7406\u5b8c\u6210\u540e\uff0c\u5185\u6838\u4f1a\u5c06\u7ed3\u679c\uff08\u5982\u8bfb\u53d6\u7684\u5b57\u8282\u6570\uff09\u4fdd\u5b58\u5728\u5bc4\u5b58\u5668\u4e2d\uff0c\u5e76\u901a\u8fc7<code>sysret<\/code>\u6307\u4ee4\u8fd4\u56de\u5230\u7528\u6237\u6001\u3002\u8fd4\u56de\u65f6\uff0cCPU\u4f1a\u5207\u6362\u56de\u7528\u6237\u6a21\u5f0f\uff0c\u6062\u590d\u7528\u6237\u7a0b\u5e8f\u7684\u6267\u884c\u73af\u5883\u3002<\/p>\n<p>\u4ee5\u4e0b\u662f\u8fd4\u56de\u7528\u6237\u6001\u7684\u8fc7\u7a0b\u793a\u4f8b\uff1a<\/p>\n<pre><code class=\"language-c\">\/\/ \u5185\u6838\u5904\u7406\u5b8c\u6210\uff0c\u5c06\u7ed3\u679c\u5b58\u653e\u5728rax\u5bc4\u5b58\u5668\u4e2d\nmov %rax, result\n\n\/\/ \u8fd4\u56de\u7528\u6237\u6001\nsysret<\/code><\/pre>\n<p>\u7528\u6237\u7a0b\u5e8f\u53ef\u4ee5\u901a\u8fc7\u8fd4\u56de\u503c\u83b7\u5f97\u7cfb\u7edf\u8c03\u7528\u7684\u7ed3\u679c\uff1a<\/p>\n<pre><code class=\"language-c\">if (bytes_read &lt; 0) {\n    perror(&quot;read&quot;);\n} else {\n    printf(&quot;Read %zd bytes\\n&quot;, bytes_read);\n}<\/code><\/pre>\n<h2>\u5177\u4f53\u793a\u4f8b\uff1a<code>read<\/code>\u7cfb\u7edf\u8c03\u7528\u7684\u5b8c\u6574\u8def\u5f84<\/h2>\n<p>\u4ee5\u4e0b\u662f\u4e00\u4e2a\u5177\u4f53\u7684\u793a\u4f8b\uff0c\u6f14\u793a\u4ece\u7528\u6237\u6001\u53d1\u8d77<code>read<\/code>\u7cfb\u7edf\u8c03\u7528\u5230\u5185\u6838\u6001\u5904\u7406\u7684\u5b8c\u6574\u8def\u5f84\uff1a<\/p>\n<ol>\n<li>\n<p><strong>\u7528\u6237\u6001\u7a0b\u5e8f<\/strong>\uff1a<\/p>\n<pre><code class=\"language-c\">ssize_t bytes_read = read(file_descriptor, buffer, count);<\/code><\/pre>\n<\/li>\n<li>\n<p><strong>C\u5e93\u5c01\u88c5<\/strong>\uff1a<\/p>\n<pre><code class=\"language-c\">ssize_t read(int fd, void *buf, size_t count) {\n    return syscall(SYS_read, fd, buf, count);\n}<\/code><\/pre>\n<\/li>\n<li>\n<p><strong>\u6c47\u7f16\u4ee3\u7801\u5207\u6362\u5230\u5185\u6838\u6001<\/strong>\uff1a<\/p>\n<pre><code class=\"language-c\">ssize_t result;\nasm volatile (\n    \"syscall\"\n    : \"=a\" (result)\n    : \"a\" (SYS_read), \"D\" (fd), \"S\" (buf), \"d\" (count)\n    : \"rcx\", \"r11\", \"memory\"\n);<\/code><\/pre>\n<\/li>\n<li>\n<p><strong>\u5185\u6838\u7cfb\u7edf\u8c03\u7528\u5165\u53e3<\/strong>\uff1a<\/p>\n<pre><code class=\"language-c\">asmlinkage long sys_read(unsigned int fd, char __user *buf, size_t count) {\n    struct file *file;\n    ssize_t ret;\n\n    file = fget(fd);\n    if (!file) {\n        return -EBADF;\n    }\n\n    ret = vfs_read(file, buf, count, &file->f_pos);\n    fput(file);\n\n    return ret;\n}<\/code><\/pre>\n<\/li>\n<li>\n<p><strong>\u8fd4\u56de\u7528\u6237\u6001<\/strong>\uff1a<\/p>\n<pre><code class=\"language-c\">\/\/ \u5185\u6838\u5904\u7406\u5b8c\u6210\uff0c\u8fd4\u56de\u7528\u6237\u6001<\/code><\/pre>\n<\/li>\n<\/ol>\n<h3>\u7cfb\u7edf\u8c03\u7528\u8868\uff08<code>sys_call_table<\/code>\uff09<\/h3>\n<p>\u7cfb\u7edf\u8c03\u7528\u8868<code>sys_call_table<\/code>\u662f\u4e00\u4e2a\u5305\u542b\u6240\u6709\u7cfb\u7edf\u8c03\u7528\u5904\u7406\u51fd\u6570\u6307\u9488\u7684\u6570\u7ec4\u3002\u5185\u6838\u521d\u59cb\u5316\u65f6\uff0c\u4f1a\u586b\u5145\u8fd9\u5f20\u8868\uff1a<\/p>\n<pre><code class=\"language-c\">void *sys_call_table[] = {\n    [SYS_read] = sys_read,\n    [SYS_write] = sys_write,\n    [SYS_open] = sys_open,\n    \/\/ \u5176\u4ed6\u7cfb\u7edf\u8c03\u7528\n};<\/code><\/pre>\n<p>\u7cfb\u7edf\u8c03\u7528\u53f7<code>SYS_read<\/code>\u5bf9\u5e94\u6570\u7ec4\u4e2d\u7684\u7d22\u5f15\u3002\u901a\u8fc7\u67e5\u627e\u8fd9\u4e2a\u7d22\u5f15\uff0c\u5185\u6838\u53ef\u4ee5\u627e\u5230\u5904\u7406<code>read<\/code>\u7cfb\u7edf\u8c03\u7528\u7684\u51fd\u6570\u6307\u9488<code>sys_read<\/code>\u3002<\/p>\n<h3>\u5185\u6838\u6001\u5230\u7528\u6237\u6001\u7684\u5207\u6362<\/h3>\n<p>\u7cfb\u7edf\u8c03\u7528\u5904\u7406\u5b8c\u6210\u540e\uff0c\u5185\u6838\u9700\u8981\u5c06\u7ed3\u679c\u8fd4\u56de\u7ed9\u7528\u6237\u7a0b\u5e8f\uff0c\u5e76\u5207\u6362\u56de\u7528\u6237\u6001\u3002\u5185\u6838\u4f1a\u6062\u590d\u7528\u6237\u7a0b\u5e8f\u7684\u6267\u884c\u73af\u5883\uff0c\u5305\u62ec\u5bc4\u5b58\u5668\u548c\u6808\u6307\u9488\u7b49\uff0c\u7136\u540e\u6267\u884c<code>sysret<\/code>\u6307\u4ee4\u8fd4\u56de\u7528\u6237\u6001\u3002<\/p>\n<h2>\u7ed3\u8bba<\/h2>\n<p>\u7cfb\u7edf\u8c03\u7528\u662fLinux\u5185\u6838\u4e2d\u4e00\u4e2a\u81f3\u5173\u91cd\u8981\u7684\u673a\u5236\uff0c\u5b83\u5141\u8bb8\u7528\u6237\u7a0b\u5e8f\u8bf7\u6c42\u5185\u6838\u63d0\u4f9b\u5404\u79cd\u670d\u52a1\u3002\u901a\u8fc7\u7279\u5b9a\u7684\u6307\u4ee4\u548c\u4e2d\u65ad\uff0c\u7528\u6237\u7a0b\u5e8f\u53ef\u4ee5\u5b89\u5168\u5730\u5207\u6362\u5230\u5185\u6838\u6001\uff0c\u6267\u884c\u7279\u6743\u64cd\u4f5c\uff0c\u7136\u540e\u8fd4\u56de\u7528\u6237\u6001\u3002\u7406\u89e3\u7cfb\u7edf\u8c03\u7528\u7684\u6267\u884c\u8fc7\u7a0b\uff0c\u5bf9\u4e8e\u6df1\u5165\u7406\u89e3\u64cd\u4f5c\u7cfb\u7edf\u5185\u6838\u7684\u5de5\u4f5c\u539f\u7406\u548c\u7f16\u5199\u9ad8\u6548\u7684\u7cfb\u7edf\u7ea7\u7a0b\u5e8f\u5177\u6709\u91cd\u8981\u610f\u4e49\u3002<\/p>\n<p>\u5e0c\u671b\u672c\u6587\u80fd\u5e2e\u52a9\u4f60\u66f4\u597d\u5730\u7406\u89e3Linux\u5185\u6838\u4e2d\u7684\u7cfb\u7edf\u8c03\u7528\u6267\u884c\u8fc7\u7a0b\u3002\u5982\u679c\u4f60\u6709\u4efb\u4f55\u95ee\u9898\u6216\u5efa\u8bae\uff0c\u6b22\u8fce\u5728\u8bc4\u8bba\u533a\u7559\u8a00\u8ba8\u8bba\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u7cfb\u7edf\u8c03\u7528\u662f\u7528\u6237\u6001\u7a0b\u5e8f\u4e0e\u64cd\u4f5c\u7cfb\u7edf\u5185\u6838\u4e4b\u95f4\u4ea4\u4e92\u7684\u91cd\u8981\u673a\u5236\uff0c\u901a\u8fc7\u7cfb\u7edf\u8c03\u7528\uff0c\u7528\u6237\u7a0b\u5e8f\u53ef\u4ee5\u8bf7\u6c42\u5185\u6838\u6267\u884c\u7279\u6743\u64cd\u4f5c\uff0c\u5982\u6587\u4ef6\u64cd\u4f5c\u3001\u8fdb\u7a0b\u7ba1\u7406\u548c\u7f51\u7edc\u901a\u4fe1\u7b49\u3002\u672c\u6587\u5c06\u8be6\u7ec6\u8bf4\u660eLinux\u5185\u6838\u4e2d\u7cfb\u7edf\u8c03\u7528\u7684\u6267\u884c\u8fc7\u7a0b\uff0c\u5e76\u6df1\u5165\u63a2\u8ba8\u5176\u4e2d\u7684\u7ec6\u8282\u3002 \u7cfb\u7edf\u8c03\u7528\u6982\u8ff0 \u7cfb\u7edf\u8c03\u7528\uff08System Call\uff09\u662f\u7528\u6237\u6001\u7a0b\u5e8f\u4e0e\u5185\u6838\u901a\u4fe1\u7684\u4e3b\u8981\u63a5\u53e3\u3002\u4e0e\u666e\u901a\u7684\u51fd\u6570\u8c03\u7528\u4e0d\u540c\uff0c\u7cfb\u7edf\u8c03\u7528\u9700\u8981\u4ece\u7528\u6237\u6001\u5207\u6362\u5230\u5185\u6838\u6001\uff0c\u4ece\u800c\u4f7f\u7528\u6237\u7a0b\u5e8f\u80fd\u591f\u6267\u884c\u7279\u6743\u64cd\u4f5c\u3002 \u7cfb\u7edf\u8c03\u7528\u7684\u57fa\u672c\u6d41\u7a0b \u7cfb\u7edf\u8c03\u7528\u7684\u6267\u884c\u8fc7\u7a0b\u4e3b\u8981\u5305\u62ec\u4ee5\u4e0b\u51e0\u4e2a\u6b65\u9aa4\uff1a \u7528\u6237\u6001\u7a0b\u5e8f\u53d1\u8d77\u7cfb\u7edf\u8c03\u7528\u3002 \u5207\u6362\u5230\u5185\u6838\u6001\u3002 \u5185\u6838\u5904\u7406\u7cfb\u7edf\u8c03\u7528\u3002 \u8fd4\u56de\u5230\u7528\u6237\u6001\u3002 \u4e0b\u9762\uff0c\u6211\u4eec\u5c06\u8be6\u7ec6\u8ba8\u8bba\u6bcf\u4e2a\u6b65\u9aa4\u7684\u5177\u4f53\u5b9e\u73b0\u548c\u7ec6\u8282\u3002 1. \u7528\u6237\u6001\u7a0b\u5e8f\u53d1\u8d77\u7cfb\u7edf\u8c03\u7528 \u7528\u6237\u7a0b\u5e8f\u901a\u8fc7\u8c03\u7528C\u6807\u51c6\u5e93\u4e2d\u7684\u5c01\u88c5\u51fd\u6570\u6765\u53d1\u8d77\u7cfb\u7edf\u8c03\u7528\u3002\u8fd9\u4e9b\u51fd\u6570\u901a\u5e38\u5728glibc\u5e93\u4e2d\u5b9e\u73b0\u3002\u4ee5read()\u51fd\u6570\u4e3a\u4f8b\uff0c\u7528\u6237\u7a0b\u5e8f\u53ef\u80fd\u4f1a\u8fd9\u6837\u8c03\u7528\uff1a ssize_t bytes_read = read(file_descriptor, buffer, count); \u5728glibc\u5e93\u4e2d\uff0cread()\u51fd\u6570\u7684\u5b9e\u73b0\u4f1a\u901a\u8fc7syscall\u51fd\u6570\u5b9e\u9645\u6267\u884c\u7cfb\u7edf\u8c03\u7528\uff1a ssize_t read(int fd, void *buf, size_t count) { return syscall(SYS_read, fd, buf, count); } SYS_read\u662f\u7cfb\u7edf\u8c03\u7528\u53f7\uff0c\u5728\u5934\u6587\u4ef6unistd.h\u4e2d\u5b9a\u4e49\uff1a #define SYS_read 0 2. \u5207\u6362\u5230\u5185\u6838\u6001 \u7528\u6237\u6001\u901a\u8fc7\u7279\u5b9a\u7684\u6307\u4ee4\uff08\u5982syscall\u6307\u4ee4\uff09\u5c06\u7cfb\u7edf\u8c03\u7528\u53f7\u548c\u53c2\u6570\u4f20\u9012\u7ed9\u5185\u6838\uff0c\u5e76\u89e6\u53d1\u4e00\u4e2a\u9677\u9631\uff08trap\uff09\uff0c\u5bfc\u81f4CPU\u5207\u6362\u5230\u5185\u6838\u6001\u3002\u4ee5\u4e0b\u662fsyscall\u6307\u4ee4\u7684\u793a\u4f8b\uff1a ssize_t result; asm volatile ( &quot;syscall&quot; \/\/ \u53d1\u8d77\u7cfb\u7edf\u8c03\u7528 : &quot;=a&quot; (result) \/\/ \u8fd4\u56de\u503c\u5b58\u653e\u5728rax\u5bc4\u5b58\u5668\u4e2d : &quot;a&quot; (SYS_read), \/\/ \u7cfb\u7edf\u8c03\u7528\u53f7\u653e\u5728rax\u5bc4\u5b58\u5668\u4e2d &quot;D&quot; (file_descriptor), \/\/ \u7b2c\u4e00\u4e2a\u53c2\u6570\u653e\u5728rdi\u5bc4\u5b58\u5668\u4e2d &quot;S&quot; (buffer), \/\/ \u7b2c\u4e8c\u4e2a\u53c2\u6570\u653e\u5728rsi\u5bc4\u5b58\u5668\u4e2d &quot;d&quot; (count) \/\/ \u7b2c\u4e09\u4e2a\u53c2\u6570\u653e\u5728rdx\u5bc4\u5b58\u5668\u4e2d : &quot;rcx&quot;, &quot;r11&quot;, &quot;memory&quot; ); \u8fd9\u6bb5\u4ee3\u7801\u4e2d\uff0csyscall\u6307\u4ee4\u4f1a\u5bfc\u81f4\u5904\u7406\u5668\u8fdb\u5165\u5185\u6838\u6001\uff0c\u5e76\u8df3\u8f6c\u5230\u5185\u6838\u4e2d\u5bf9\u5e94\u7684\u7cfb\u7edf\u8c03\u7528\u5904\u7406\u7a0b\u5e8f\u3002 3. \u5185\u6838\u5904\u7406\u7cfb\u7edf\u8c03\u7528 \u8fdb\u5165\u5185\u6838\u6001\u540e\uff0cCPU\u4f1a\u6839\u636e\u7cfb\u7edf\u8c03\u7528\u53f7\u67e5\u627e\u76f8\u5e94\u7684\u5185\u6838\u5904\u7406\u51fd\u6570\u3002\u5728Linux\u5185\u6838\u4e2d\uff0c\u7cfb\u7edf\u8c03\u7528\u53f7\u548c\u5904\u7406\u51fd\u6570\u7684\u5bf9\u5e94\u5173\u7cfb\u5b58\u50a8\u5728\u4e00\u4e2a\u7cfb\u7edf\u8c03\u7528\u8868\u4e2d\u3002\u8fd9\u5f20\u8868\u5728\u5185\u6838\u521d\u59cb\u5316\u65f6\u88ab\u586b\u5145\uff0c\u5305\u542b\u6240\u6709\u652f\u6301\u7684\u7cfb\u7edf\u8c03\u7528\u51fd\u6570\u6307\u9488\u3002 \u4ee5\u4e0b\u662f\u4e00\u4e2a\u7b80\u5316\u7684\u7cfb\u7edf\u8c03\u7528\u8868\u793a\u4f8b\uff1a extern void *sys_call_table[]; asmlinkage long sys_read(unsigned int fd, char __user *buf, size_t count); void *sys_call_table[] = { [SYS_read] = sys_read, \/\/ \u5176\u4ed6\u7cfb\u7edf\u8c03\u7528 }; \u5f53CPU\u6267\u884csyscall\u6307\u4ee4\u65f6\uff0c\u5185\u6838\u4f1a\u901a\u8fc7\u7cfb\u7edf\u8c03\u7528\u53f7\u67e5\u627esys_call_table\uff0c\u627e\u5230\u5bf9\u5e94\u7684\u5904\u7406\u51fd\u6570\u5e76\u6267\u884c\u3002\u4f8b\u5982\uff0c\u5bf9\u4e8eread\u7cfb\u7edf\u8c03\u7528\uff0c\u5185\u6838\u4f1a\u8c03\u7528sys_read\u51fd\u6570\uff1a asmlinkage long sys_read(unsigned int fd, char __user *buf, size_t count) { \/\/ \u5185\u6838\u5b9e\u73b0\u7684\u8bfb\u53d6\u64cd\u4f5c struct file *file; ssize_t ret; file = fget(fd); if (!file) { return -EBADF; } ret = vfs_read(file, buf, count, &amp;file-&gt;f_pos); fput(file); return ret; } sys_read\u51fd\u6570\u9996\u5148\u68c0\u67e5\u6587\u4ef6\u63cf\u8ff0\u7b26\u662f\u5426\u6709\u6548\uff0c\u7136\u540e\u8c03\u7528vfs_read\u51fd\u6570\u6267\u884c\u5b9e\u9645\u7684\u6587\u4ef6\u8bfb\u53d6\u64cd\u4f5c\u3002vfs_read\u51fd\u6570\u662f\u865a\u62df\u6587\u4ef6\u7cfb\u7edf\uff08VFS\uff09\u5c42\u7684\u4e00\u90e8\u5206\uff0c\u8d1f\u8d23\u4e0e\u5177\u4f53\u7684\u6587\u4ef6\u7cfb\u7edf\u4ea4\u4e92\u3002 4. \u8fd4\u56de\u7528\u6237\u6001 \u7cfb\u7edf\u8c03\u7528\u5904\u7406\u5b8c\u6210\u540e\uff0c\u5185\u6838\u4f1a\u5c06\u7ed3\u679c\uff08\u5982\u8bfb\u53d6\u7684\u5b57\u8282\u6570\uff09\u4fdd\u5b58\u5728\u5bc4\u5b58\u5668\u4e2d\uff0c\u5e76\u901a\u8fc7sysret\u6307\u4ee4\u8fd4\u56de\u5230\u7528\u6237\u6001\u3002\u8fd4\u56de\u65f6\uff0cCPU\u4f1a\u5207\u6362\u56de\u7528\u6237\u6a21\u5f0f\uff0c\u6062\u590d\u7528\u6237\u7a0b\u5e8f\u7684\u6267\u884c\u73af\u5883\u3002 \u4ee5\u4e0b\u662f\u8fd4\u56de\u7528\u6237\u6001\u7684\u8fc7\u7a0b\u793a\u4f8b\uff1a \/\/ \u5185\u6838\u5904\u7406\u5b8c\u6210\uff0c\u5c06\u7ed3\u679c\u5b58\u653e\u5728rax\u5bc4\u5b58\u5668\u4e2d mov %rax, result \/\/ \u8fd4\u56de\u7528\u6237\u6001 sysret \u7528\u6237\u7a0b\u5e8f\u53ef\u4ee5\u901a\u8fc7\u8fd4\u56de\u503c\u83b7\u5f97\u7cfb\u7edf\u8c03\u7528\u7684\u7ed3\u679c\uff1a if&#8230;<\/p>\n","protected":false},"author":1,"featured_media":49,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_crdt_document":"","fifu_image_url":"","fifu_image_alt":"","footnotes":""},"categories":[2,10],"tags":[21,5,23,22],"class_list":["post-46","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-blog","category-linux","tag-kernel","tag-linux","tag-read","tag-syscall"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.5 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Linux Kernel System Call \u6d41\u7a0b\u5206\u6790 - TianYa Blog<\/title>\n<meta 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