{"id":3498,"date":"2011-11-08T11:06:32","date_gmt":"2011-11-08T03:06:32","guid":{"rendered":"http:\/\/edsionte.com\/techblog\/?p=3498"},"modified":"2011-11-08T11:55:46","modified_gmt":"2011-11-08T03:55:46","slug":"x86%e6%9e%b6%e6%9e%84%e4%b8%8b%e4%b8%8e%e5%88%86%e9%a1%b5%e6%9c%ba%e5%88%b6%e6%9c%89%e5%85%b3%e7%9a%84%e5%ae%8f%e5%92%8c%e5%87%bd%e6%95%b0","status":"publish","type":"post","link":"http:\/\/edsionte.com\/techblog\/archives\/3498","title":{"rendered":"x86\u67b6\u6784\u4e0b\u4e0e\u5206\u9875\u673a\u5236\u6709\u5173\u7684\u5b8f\u548c\u51fd\u6570"},"content":{"rendered":"<p>Linux\u91c7\u7528\u4e86\u901a\u7528\u7684\u56db\u7ea7\u5206\u9875\u673a\u5236\uff0c\u6240\u8c13\u901a\u7528\u5c31\u662f\u6307Linux\u4f7f\u7528\u8fd9\u79cd\u5206\u9875\u673a\u5236\u7ba1\u7406\u6240\u6709\u67b6\u6784\u7684\u5206\u9875\u6a21\u578b\uff0c\u5373\u4fbf\u67d0\u4e9b\u67b6\u6784\u5e76\u4e0d\u652f\u6301\u56db\u7ea7\u5206\u9875\u3002\u5bf9\u4e8e\u5e38\u89c1\u7684x86\u67b6\u6784\uff0c\u5982\u679c\u7cfb\u7edf\u662f32\u4f4d\uff0c\u4e8c\u7ea7\u5206\u9875\u6a21\u578b\u5c31\u53ef\u6ee1\u8db3\u7cfb\u7edf\u9700\u6c42\uff1b\u5982\u679c32\u4f4d\u7cfb\u7edf\u91c7\u7528PAE(\u7269\u7406\u5730\u5740\u6269\u5c55)\u6a21\u5f0f\uff0cLinux\u4f7f\u7528\u4e09\u7ea7\u5206\u9875\u6a21\u578b\uff1b\u5982\u679c\u662f64\u4f4d\u7cfb\u7edf\uff0cLinux\u4f7f\u7528\u56db\u7ea7\u5206\u9875\u6a21\u578b\uff0c\u4e5f\u5c31\u662f\u8bf4x86\u67b6\u6784\u7684\u5206\u9875\u6a21\u578b\u53ef\u80fd\u662f\u4e8c\u7ea7\u3001\u4e09\u7ea7\u6216\u56db\u7ea7\u3002<\/p>\n<p>\u6b63\u5982\u4e0a\u9762\u6240\u8bf4\uff0cLinux\u901a\u7528\u7684\u56db\u7ea7\u5206\u9875\u673a\u5236\u5747\u53ef\u4ee5\u6ee1\u8db3\u4e0a\u8ff0\u4e09\u79cd\u60c5\u51b5\u3002\u672c\u6587\u5c06\u5206\u6790x86\u67b6\u6784\u4e0b\u4e0e\u5206\u9875\u673a\u5236\u76f8\u5173\u7684\u4e00\u4e9b\u5b8f\u548c\u51fd\u6570\uff0c\u6765\u5c55\u73b0\u8fd9\u79cd\u5206\u9875\u673a\u5236\u7684\u901a\u7528\u578b\u3002<\/p>\n<h3>\u56db\u7ea7\u5206\u9875\u6a21\u578b<\/h3>\n<p>x86-64\u67b6\u6784\u91c7\u7528\u56db\u7ea7\u5206\u9875\u6a21\u578b\uff0c\u5b83\u662fLinux\u56db\u7ea7\u5206\u9875\u673a\u5236\u7684\u4e00\u4e2a\u5f88\u597d\u7684\u5b9e\u73b0\u3002\u6211\u4eec\u5c06x86-64\u67b6\u6784\u7684\u5206\u9875\u6a21\u578b\u4f5c\u4e3a\u5206\u6790\u7684\u5165\u53e3\u70b9\uff0c\u5b83\u5f88\u597d\u7684\u201c\u8fce\u5408\u201d\u4e86Linux\u7684\u56db\u7ea7\u5206\u9875\u673a\u5236\u3002\u7a0d\u5019\u6211\u4eec\u518d\u5206\u6790\u8fd9\u79cd\u673a\u5236\u5982\u4f55\u540c\u6837\u505a\u5230\u9002\u5408\u4e09\u7ea7\u548c\u4e8c\u7ea7\u5206\u9875\u6a21\u578b\u3002<\/p>\n<p><strong>PGDIR_SHIFT\u53ca\u76f8\u5173\u5b8f<\/strong><\/p>\n<p>\u8868\u793a\u7ebf\u6027\u5730\u5740\u4e2doffset\u5b57\u6bb5\u3001Table\u5b57\u6bb5\u3001Middle Dir\u5b57\u6bb5\u548cUpper Dir\u5b57\u6bb5\u7684\u4f4d\u6570\u3002PGDIR_SIZE\u7528\u4e8e\u8ba1\u7b97\u9875\u5168\u5c40\u76ee\u5f55\u4e2d\u4e00\u4e2a\u8868\u9879\u80fd\u6620\u5c04\u533a\u57df\u7684\u5927\u5c0f\u3002PGDIR_MASK\u7528\u4e8e\u5c4f\u853d\u7ebf\u6027\u5730\u5740\u4e2dMiddle Dir\u5b57\u6bb5\u3001Table\u5b57\u6bb5\u548coffset\u5b57\u6bb5\u6240\u5728\u4f4d\u3002<\/p>\n<p>\u5728\u56db\u7ea7\u5206\u9875\u6a21\u578b\u4e2d\uff0cPGDIR_SHIFT\u5360\u636e39\u4f4d\uff0c\u53739\u4f4d\u9875\u4e0a\u7ea7\u76ee\u5f55\u30019\u4f4d\u9875\u4e2d\u95f4\u76ee\u5f55\u30019\u4f4d\u9875\u8868\u548c12\u4f4d\u504f\u79fb\u3002\u9875\u5168\u5c40\u76ee\u5f55\u540c\u6837\u5360\u7ebf\u6027\u5730\u5740\u76849\u4f4d\uff0c\u56e0\u6b64PTRS_PER_PGD\u4e3a512\u3002<\/p>\n<pre class=\"brush:c\">arch\/x86\/include\/asm\/pgtable_64_types.h\r\n#define PGDIR_SHIFT 39\r\n#define PTRS_PER_PGD 512\r\n#define PGDIR_SIZE (_AC(1, UL) &lt;&lt; PGDIR_SHIFT)\r\n#define PGDIR_MASK (~(PGDIR_SIZE - 1))<\/pre>\n<p><strong>pgd_offset()<\/strong><\/p>\n<p>\u8be5\u51fd\u6570\u8fd4\u56de\u7ebf\u6027\u5730\u5740address\u5728\u9875\u5168\u5c40\u76ee\u5f55\u4e2d\u5bf9\u5e94\u8868\u9879\u7684\u7ebf\u6027\u5730\u5740\u3002mm\u4e3a\u6307\u5411\u4e00\u4e2a\u5185\u5b58\u63cf\u8ff0\u7b26\u7684\u6307\u9488\uff0caddress\u4e3a\u8981\u8f6c\u6362\u7684\u7ebf\u6027\u5730\u5740\u3002\u8be5\u5b8f\u6700\u7ec8\u8fd4\u56deaddrress\u5728\u9875\u5168\u5c40\u76ee\u5f55\u4e2d\u76f8\u5e94\u8868\u9879\u7684\u7ebf\u6027\u5730\u5740\u3002<\/p>\n<pre class=\"brush:c\">arch\/x86\/include\/asm\/pgtable.h\r\n#define pgd_index(address) (((address) &gt;&gt; PGDIR_SHIFT) &amp; (PTRS_PER_PGD - 1))\r\n#define pgd_offset(mm, address) ((mm)-&gt;pgd + pgd_index((address)))<\/pre>\n<p><strong>PUD_SHIFT\u53ca\u76f8\u5173\u5b8f<\/strong><\/p>\n<p>\u8868\u793a\u7ebf\u6027\u5730\u5740\u4e2doffset\u5b57\u6bb5\u3001Table\u5b57\u6bb5\u548cMiddle Dir\u5b57\u6bb5\u7684\u4f4d\u6570\u3002PUD_SIZE\u7528\u4e8e\u8ba1\u7b97\u9875\u4e0a\u7ea7\u76ee\u5f55\u4e00\u4e2a\u8868\u9879\u6620\u5c04\u7684\u533a\u57df\u5927\u5c0f\uff0cPUD_MASK\u7528\u4e8e\u5c4f\u853d\u7ebf\u6027\u5730\u5740\u4e2dMiddle Dir\u5b57\u6bb5\u3001Table\u5b57\u6bb5\u548coffset\u5b57\u6bb5\u6240\u5728\u4f4d\u3002<\/p>\n<p>\u572864\u4f4d\u7cfb\u7edf\u56db\u7ea7\u5206\u9875\u6a21\u578b\u4e0b\uff0cPUD_SHIFT\u7684\u5927\u5c0f\u4e3a30\uff0c\u5305\u62ec12\u4f4d\u7684offset\u5b57\u6bb5\u30019\u4f4dTable\u5b57\u6bb5\u548c9\u4f4dMiddle Dir\u5b57\u6bb5\u3002\u7531\u4e8e\u9875\u4e0a\u7ea7\u76ee\u5f55\u5728\u7ebf\u6027\u5730\u5740\u4e2d\u53609\u4f4d\uff0c\u56e0\u6b64\u9875\u4e0a\u7ea7\u76ee\u5f55\u7684\u8868\u9879\u6570\u4e3a512\u3002<\/p>\n<pre class=\"brush:c\">arch\/x86\/include\/asm\/pgtable_64_types.h\r\n#define PUD_SHIFT 30\r\n#define PTRS_PER_PUD 512\r\n#define PUD_SIZE        (_AC(1, UL) &lt;&lt; PUD_SHIFT)\r\n#define PUD_MASK        (~(PUD_SIZE - 1))<\/pre>\n<p><strong>pud_offset()<\/strong><\/p>\n<p>pgd_val(pgd)\u83b7\u5f97pgd\u6240\u6307\u7684\u9875\u5168\u5c40\u76ee\u5f55\u9879\uff0c\u5b83\u4e0ePTE_PFN_MASK\u76f8\u4e0e\u5f97\u5230\u8be5\u9879\u6240\u5bf9\u5e94\u7684\u7269\u7406\u9875\u6846\u53f7\u3002__va()\u7528\u4e8e\u5c06\u7269\u7406\u5730\u5740\u8f6c\u5316\u4e3a\u865a\u62df\u5730\u5740\u3002\u4e5f\u5c31\u662f\u8bf4\uff0cpgd_page_vaddr\u6700\u7ec8\u8fd4\u56de\u9875\u5168\u5c40\u76ee\u5f55\u9879pgd\u6240\u5bf9\u5e94\u7684\u7ebf\u6027\u5730\u5740\u3002\u56e0\u4e3apud_index()\u8fd4\u56de\u7ebf\u6027\u5730\u5740\u5728\u9875\u4e0a\u7ea7\u76ee\u5f55\u4e2d\u6240\u5728\u8868\u9879\u7684\u7d22\u5f15\uff0c\u56e0\u6b64pud_offset()\u6700\u7ec8\u8fd4\u56deaddrress\u5bf9\u5e94\u7684\u9875\u4e0a\u7ea7\u76ee\u5f55\u9879\u7684\u7ebf\u6027\u5730\u5740\u3002<\/p>\n<pre class=\"brush:c\">arch\/x86\/include\/asm\/page.h\r\n#define __va(x)                 ((void *)((unsigned long)(x)+PAGE_OFFSET))\r\narch\/x86\/include\/asm\/pgtable_types.h\r\n#define PTE_PFN_MASK            ((pteval_t)PHYSICAL_PAGE_MASK)\r\narch\/x86\/include\/asm\/pgtable.h\r\nstatic inline unsigned long pgd_page_vaddr(pgd_t pgd)\r\n{\r\n        return (unsigned long)__va((unsigned long)pgd_val(pgd) &amp; PTE_PFN_MASK);\r\n}\r\nstatic inline pud_t *pud_offset(pgd_t *pgd, unsigned long address)\r\n{\r\n        return (pud_t *)pgd_page_vaddr(*pgd) + pud_index(address);\r\n}<\/pre>\n<p><strong>PMD_SHIFT\u53ca\u76f8\u5173\u5b8f<\/strong><\/p>\n<p>\u8868\u793a\u7ebf\u6027\u5730\u5740\u4e2doffset\u5b57\u6bb5\u548cTable\u5b57\u6bb5\u7684\u4f4d\u6570\uff0c2\u7684PMD_SHIFT\u6b21\u5e42\u8868\u793a\u4e00\u4e2a\u9875\u4e2d\u95f4\u76ee\u5f55\u9879\u53ef\u4ee5\u6620\u5c04\u7684\u5185\u5b58\u533a\u57df\u5927\u5c0f\u3002PMD_SIZE\u7528\u4e8e\u8ba1\u7b97\u8fd9\u4e2a\u533a\u57df\u7684\u5927\u5c0f\uff0cPMD_MASK\u7528\u6765\u5c4f\u853doffset\u5b57\u6bb5\u548cTable\u5b57\u6bb5\u7684\u6240\u6709\u4f4d\u3002PTRS_PER_PMD\u8868\u793a\u9875\u4e2d\u95f4\u76ee\u5f55\u4e2d\u8868\u9879\u7684\u4e2a\u6570\u3002<\/p>\n<p>\u572864\u4f4d\u7cfb\u7edf\u4e2d\uff0cLinux\u91c7\u7528\u56db\u7ea7\u5206\u9875\u6a21\u578b\u3002\u7ebf\u6027\u5730\u5740\u5305\u542b\u9875\u5168\u5c40\u76ee\u5f55\u3001\u9875\u4e0a\u7ea7\u76ee\u5f55\u3001\u9875\u4e2d\u95f4\u76ee\u5f55\u3001\u9875\u8868\u548c\u504f\u79fb\u91cf\u4e94\u90e8\u5206\u3002\u5728\u8fd9\u4e24\u79cd\u6a21\u578b\u4e2dPMD_SHIFT\u536021\u4f4d\uff0c\u5373\u5305\u62ecTable\u5b57\u6bb5\u76849\u4f4d\u548coffset\u5b57\u6bb5\u768412\u4f4d\u3002PTRS_PER_PMD\u7684\u503c\u4e3a512\uff0c\u53732\u76849\u6b21\u5e42\uff0c\u8868\u793a\u9875\u4e2d\u95f4\u76ee\u5f55\u5305\u542b\u7684\u8868\u9879\u4e2a\u6570\u3002<\/p>\n<pre class=\"brush:c\">#define PMD_SHIFT 21\r\n#define PTRS_PER_PMD 512\r\n#define PMD_SIZE (_AC(1, UL) &lt;&lt; PMD_SHIFT)\r\n#define PMD_MASK (~(PMD_SIZE - 1))<\/pre>\n<p><strong>pmd_offset()<\/strong><\/p>\n<p>\u8be5\u51fd\u6570\u8fd4\u56deaddress\u5728\u9875\u4e2d\u95f4\u76ee\u5f55\u4e2d\u5bf9\u5e94\u8868\u9879\u7684\u7ebf\u6027\u5730\u5740\u3002<\/p>\n<pre class=\"brush:c\">static inline pmd_t *pmd_offset(pud_t *pud, unsigned long address)\r\n{\r\n        return (pmd_t *)pud_page_vaddr(*pud) + pmd_index(address);\r\n}\r\nstatic inline unsigned long pud_page_vaddr(pud_t pud)\r\n{\r\n        return (unsigned long)__va((unsigned long)pud_val(pud) &amp; PTE_PFN_MASK);\r\n}<\/pre>\n<p><strong>PAGE_SHIFT\u53ca\u76f8\u5173\u5b8f<\/strong><\/p>\n<p>\u8868\u793a\u7ebf\u6027\u5730\u5740offset\u5b57\u6bb5\u7684\u4f4d\u6570\u3002\u8be5\u5b8f\u7684\u503c\u88ab\u5b9a\u4e49\u4e3a12\u4f4d\uff0c\u5373\u9875\u7684\u5927\u5c0f\u4e3a4KB\u3002\u4e0e\u5b83\u5bf9\u5e94\u7684\u5b8f\u6709PAGE_SIZE\uff0c\u5b83\u8fd4\u56de\u4e00\u4e2a\u9875\u7684\u5927\u5c0f\uff1bPAGE_MASK\u7528\u6765\u5c4f\u853doffset\u5b57\u6bb5\uff0c\u5176\u503c\u4e3aoxfffff000\u3002PTRS_PER_PTE\u8868\u660e\u9875\u8868\u5728\u7ebf\u6027\u5730\u5740\u4e2d\u5360\u636e9\u4f4d\u3002<\/p>\n<pre class=\"brush:c\">arch\/x86\/include\/asm\/page_types.h\r\n\/* PAGE_SHIFT determines the page size *\/\r\n#define PAGE_SHIFT 12\r\n#define PTRS_PER_PTE    512\r\n#define PAGE_SIZE (_AC(1,UL) &lt;&lt; PAGE_SHIFT)\r\n#define PAGE_MASK (~(PAGE_SIZE-1))<\/pre>\n<p>\u901a\u8fc7\u4e0a\u9762\u7684\u5206\u6790\u53ef\u77e5\uff0c\u5728x86-64\u67b6\u6784\u4e0b64\u4f4d\u7684\u7ebf\u6027\u5730\u5740\u88ab\u5212\u5206\u4e3a\u4e94\u90e8\u5206\uff0c\u6bcf\u90e8\u5206\u5360\u636e\u7684\u4f4d\u6570\u5206\u522b\u4e3a9\uff0c9\uff0c9\uff0c9\uff0c12\uff0c\u5b9e\u9645\u4e0a\u53ea\u7528\u4e8664\u4f4d\u4e2d\u768448\u4f4d\u3002\u5bf9\u4e8e\u56db\u7ea7\u9875\u8868\u800c\u8a00\uff0c\u7ea7\u522b\u4ece\u9ad8\u5230\u5e95\u6bcf\u7ea7\u9875\u8868\u4e2d\u8868\u9879\u7684\u4e2a\u6570\u4e3a512\uff0c512\uff0c512\uff0c512\u3002<\/p>\n<h3>\u4e09\u7ea7\u5206\u9875\u6a21\u578b<\/h3>\n<p>Linux\u56db\u7ea7\u5206\u9875\u673a\u5236\u5728x86-64\u67b6\u6784\u4e0b\u6709\u5b8c\u7f8e\u7684\u4f53\u73b0\uff0c\u56e0\u4e3a\u6bcf\u4e2a\u9875\u8868\u5b9e\u9645\u4e0a\u90fd\u662f\u6709\u6548\u7684\u3002\u800c\u5728\u63a5\u4e0b\u6765\u8981\u5206\u6790\u7684\u4f7f\u7528PAE\u7684x86-32\u67b6\u6784\u4e2d\uff0c\u9875\u4e0a\u7ea7\u76ee\u5f55\u5b9e\u9645\u4e0a\u662f\u4e0d\u5b58\u5728\u7684\uff0c\u4f46\u662fLinux\u91c7\u7528\u4e86\u4e00\u79cd\u6709\u6548\u7684\u65b9\u6cd5\u4f7f\u4e09\u7ea7\u5206\u9875\u6a21\u578b\u4ecd\u7136\u53ef\u4ee5\u7528\u56db\u7ea7\u5206\u9875\u6a21\u578b\u6765\u7ba1\u7406\u3002<\/p>\n<p><strong>PGDIR_SHIFT\u53ca\u76f8\u5173\u5b8f<\/strong><\/p>\n<p>\u5728x86-32\u7684PAE\u6a21\u5f0f\u4e0b\uff0cPGDIR_SHIFT\u7684\u503c\u4e3a30\uff0c\u5b83\u5305\u542boffset\u768412\u4f4d\uff0cTable\u5b57\u6bb5\u76849\u4f4d\uff0cMiddle Dir\u5b57\u6bb5\u76849\u4f4d\u3002\u901a\u8fc7PTRS_PER_PGD\u53ef\u77e5\uff0c\u9875\u5168\u5c40\u76ee\u5f55\u5360\u7ebf\u6027\u5730\u5740\u6700\u9ad8\u76842\u4f4d\u3002<\/p>\n<pre class=\"brush:c\">#define PGDIR_SHIFT 30\r\n#define PTRS_PER_PGD 4<\/pre>\n<p><strong>pgd_offset()<\/strong><\/p>\n<p>\u5728\u6b64\u6a21\u5f0f\u4e0b\uff0cpgd_offset()\u7684\u5b9e\u73b0\u4e0e\u56db\u7ea7\u5206\u9875\u673a\u5236\u76f8\u540c\u3002<\/p>\n<p><strong>PUD_SHIFT\u53ca\u76f8\u5173\u5b8f<\/strong><\/p>\n<p>\u5728\u4e09\u7ea7\u5206\u9875\u6a21\u578b\u4e2d\uff0c\u9875\u4e0a\u7ea7\u76ee\u5f55\u662f\u4e0d\u5b58\u5728\u7684\uff0c\u4f46\u662fLinux\u4ecd\u7136\u4fdd\u7559\u4e86\u5b83\u5e94\u6709\u7684\u4f4d\u7f6e\u3002\u5177\u4f53\u7684\u505a\u6cd5\u662f\u5c06PUD_SHIFT\u7684\u503c\u8bbe\u4e3aPGDIR_SHIFT\uff0c\u90a3\u4e48\u4e0e\u6b64\u503c\u6709\u5173\u7684\u5b8f\u4e5f\u5c31\u4e0e\u9875\u5168\u5c40\u76ee\u5f55\u5bf9\u5e94\u7684\u5b8f\u76f8\u7b49\u3002\u5728\u8fd9\u79cd\u6a21\u5f0f\u4e0b\uff0c\u9875\u4e0a\u7ea7\u76ee\u5f55\u5728\u7ebf\u6027\u5730\u5740\u5360\u636e\u7684\u4f4d\u6570\u4e3a0\uff0c\u56e0\u6b64\u9875\u4e0a\u7ea7\u76ee\u5f55\u7684\u8868\u9879\u4ec5\u6709\u4e00\u9879\u3002<\/p>\n<pre class=\"brush:c\">typedef struct { pgd_t pgd; } pud_t;\r\n\r\n#define PUD_SHIFT PGDIR_SHIFT\r\n#define PTRS_PER_PUD 1\r\n#define PUD_SIZE (1UL &lt;&lt; PUD_SHIFT)\r\n#define PUD_MASK (~(PUD_SIZE-1))<\/pre>\n<p><strong>pud_offset()<\/strong><\/p>\n<p>pud_offset()\u672c\u5e94\u8be5\u8fd4\u56de\u7ebf\u6027\u5730\u5740addrress\u5728\u9875\u4e0a\u7ea7\u76ee\u5f55\u5bf9\u5e94\u7684\u8868\u9879\u5730\u5740\uff0c\u7531\u4e8e\u4e09\u7ea7\u5206\u9875\u6a21\u578b\u4e2d\u5e76\u4e0d\u5b58\u5728\u8be5\u9875\u76ee\u5f55\uff0c\u56e0\u6b64pud_offset()\u76f4\u63a5\u8fd4\u56deaddress\u5728\u9875\u5168\u5c40\u76ee\u5f55\u4e2d\u8868\u9879\u7684\u5730\u5740\u3002\u8fd9\u4e5f\u6b63\u662fLinux\u56db\u7ea7\u5206\u9875\u673a\u5236\u901a\u7528\u578b\u7684\u4f53\u73b0\u3002<\/p>\n<pre class=\"brush:c\">static inline pud_t * pud_offset(pgd_t * pgd, unsigned long address)\r\n{\r\n        return (pud_t *)pgd;\r\n}<\/pre>\n<p><strong>PMD_SHIFT\u53ca\u76f8\u5173\u5b8f<\/strong><\/p>\n<p>\u5728x86-32\u7684PAE\u6a21\u5f0f\u4e0b\uff0cPMD_SHIFT\u7684\u503c\u4e0e\u4e0a\u8ff0\u56db\u7ea7\u5206\u9875\u6a21\u578b\u76f8\u540c\u3002\u56e0\u6b64\u4e0e\u6b64\u503c\u5bf9\u5e94\u7684PTRS_PER_PMD\u3001PMD_SIZE\u548cPMD_MASK\u90fd\u4e0e\u56db\u7ea7\u5206\u9875\u6a21\u578b\u4e2d\u7684\u503c\u76f8\u7b49\u3002<\/p>\n<pre class=\"brush:c\">arch\/x86\/include\/asm\/pgtable-3level_types.h\r\n#define PMD_SHIFT 21\r\n#define PTRS_PER_PMD 512<\/pre>\n<p><strong>pmd_offset()<\/strong><\/p>\n<p>\u8be5\u51fd\u6570\u4e0e\u56db\u7ea7\u5206\u9875\u6a21\u578b\u4e2d\u7684\u5bf9\u5e94\u51fd\u6570\u76f8\u540c\u3002<\/p>\n<p>\u901a\u8fc7\u4e0a\u9762\u7684\u5206\u6790\u53ef\u77e5\uff0c\u91c7\u7528PAE\u7684x86-32\u67b6\u6784\u672c\u8d28\u4e0a\u91c7\u7528\u4e86\u4e09\u7ea7\u5206\u9875\u6a21\u578b\uff0c\u4f46\u662fLinux\u4f9d\u7136\u5c06\u5b83\u6309\u7167\u56db\u7ea7\u5206\u9875\u6a21\u578b\u5bf9\u5f85\u3002\u56e0\u6b64\u7ebf\u6027\u5730\u5740\u4f9d\u65e7\u88ab\u5212\u5206\u4e3a5\u90e8\u5206\uff0c\u6bcf\u90e8\u5206\u5360\u636e2\uff0c0\uff0c9\uff0c9\uff0c12\u4f4d\u3002\u4e0e\u6b64\u5bf9\u5e94\uff0c\u6bcf\u7ea7\u9875\u8868\u4e2d\u4f9d\u6b21\u5305\u542b\u7684\u8868\u9879\u4e2a\u6570\u4e3a4\uff0c1\uff0c512\uff0c512\u3002<\/p>\n<h3>\u4e8c\u7ea7\u5206\u9875\u6a21\u578b<\/h3>\n<p>x86-32\u91c7\u7528\u4e8c\u7ea7\u5206\u9875\u6a21\u578b\uff0c\u5728\u6b64\u5206\u9875\u6a21\u578b\u4e2d\u53ea\u5305\u542b\u9875\u5168\u5c40\u76ee\u5f55\u548c\u9875\u8868\uff0c\u5e76\u4e0d\u5b58\u5728\u9875\u4e2d\u95f4\u76ee\u5f55\u548c\u9875\u4e0a\u7ea7\u76ee\u5f55\u3002<\/p>\n<p><strong>PGDIR_SHIFT<\/strong><\/p>\n<p>\u5728\u4e09\u7ea7\u5206\u9875\u6a21\u578b\u4e2d\uff0cPGDIR_SHIFT\u5360\u636e22\u4f4d\uff0c\u53730\u4f4d\u9875\u4e0a\u7ea7\u76ee\u5f55\u30010\u4f4d\u9875\u4e2d\u95f4\u76ee\u5f55\u300110\u4f4d\u9875\u8868\u548c12\u4f4d\u504f\u79fb\u3002\u9875\u5168\u5c40\u76ee\u5f55\u540c\u6837\u5360\u7ebf\u6027\u5730\u5740\u768410\u4f4d\uff0c\u56e0\u6b64PTRS_PER_PGD\u4e3a1024\u3002<\/p>\n<pre class=\"brush:c\">arch\/x86\/include\/asm\/pgtable-2level_types.h\r\n#define PGDIR_SHIFT 22\r\n#define PTRS_PER_PGD 1024<\/pre>\n<p><strong>pgd_offset()<\/strong><\/p>\n<p>\u5b9e\u73b0\u65b9\u6cd5\u548c\u4e0a\u8ff0\u4e24\u79cd\u5206\u9875\u673a\u5236\u76f8\u540c\u3002<\/p>\n<p><strong>PMD_SHIFT\u548cPUD_SHIFT\u53ca\u76f8\u5173\u5b8f<\/strong><\/p>\n<p>\u5728\u4e8c\u7ea7\u5206\u9875\u6a21\u578b\u4e2d\uff0cPMD_SHIFT\u548cPUD_SHIFT\u6700\u540e\u90fd\u6307\u5411PGDIR_SHIFT\uff0c\u56e0\u6b64\u4e0e\u8be5\u503c\u76f8\u5173\u7684\u5b8f\u90fd\u4e0e\u9875\u5168\u5c40\u76ee\u5f55\u5bf9\u5e94\u7684\u503c\u76f8\u540c\u3002<\/p>\n<pre class=\"brush:c\">include\/asm-generic\/pgtable-nopmd.h\r\n#define PUD_SHIFT PGDIR_SHIFT\r\n#define PTRS_PER_PUD 1\r\n#define PUD_SIZE (1UL &lt;&lt; PUD_SHIFT)\r\n#define PUD_MASK (~(PUD_SIZE-1))\r\n\r\ntypedef struct { pud_t pud; } pmd_t;\r\n#define PMD_SHIFT PUD_SHIFT\r\n#define PTRS_PER_PMD 1\r\n#define PMD_SIZE (1UL &lt;&lt; PMD_SHIFT)\r\n#define PMD_MASK (~(PMD_SIZE-1))<\/pre>\n<p><strong>pmd_offset()\u548cpud_offset()<\/strong><\/p>\n<p>\u8fd9\u4e24\u4e2a\u5b8f\u6700\u7ec8\u90fd\u662f\u8fd4\u56deaddress\u5728\u9875\u5168\u5c40\u76ee\u5f55\u4e2d\u5bf9\u5e94\u7684\u8868\u9879\u3002<\/p>\n<pre class=\"brush:c\">static inline pmd_t * pmd_offset(pud_t * pud, unsigned long address)\r\n{\r\n        return (pmd_t *)pud;\r\n}\r\nstatic inline pud_t * pud_offset(pgd_t * pgd, unsigned long address)\r\n{\r\n        return (pud_t *)pgd;\r\n}<\/pre>\n<p>\u901a\u8fc7\u4e0a\u9762\u7684\u5206\u6790\u53ef\u77e5\uff0c\u5bf9\u4e8e\u91c7\u7528\u4e8c\u7ea7\u5206\u9875\u6a21\u578b\u7684x86-32\u67b6\u6784\uff0cLinux\u4ecd\u7136\u4f7f\u7528\u56db\u7ea7\u5206\u9875\u673a\u5236\u8fdb\u884c\u7ba1\u7406\uff0c\u53ea\u4e0d\u8fc7\u5c06\u9875\u4e0a\u7ea7\u76ee\u5f55\u548c\u9875\u4e2d\u95f4\u76ee\u5f55\u90fd\u7b49\u4ef7\u4e8e\u9875\u5168\u5c40\u76ee\u5f55\u3002\u56e0\u6b64\uff0c\u7ebf\u6027\u5730\u5740\u88ab\u5212\u5206\u4e3a\u4e94\u90e8\u5206\uff0c\u6bcf\u90e8\u5206\u4f9d\u6b21\u5360\u636e10\uff0c0\uff0c0\uff0c10\uff0c12\u3002\u6bcf\u7ea7\u9875\u8868\u4e2d\u5305\u542b\u7684\u8868\u9879\u4e2a\u6570\u4e3a1024\uff0c1\uff0c1\uff0c1024\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Linux\u91c7\u7528\u4e86\u901a\u7528\u7684\u56db\u7ea7\u5206\u9875\u673a\u5236\uff0c\u6240\u8c13\u901a\u7528\u5c31\u662f\u6307Linux\u4f7f\u7528\u8fd9\u79cd\u5206\u9875\u673a\u5236\u7ba1\u7406\u6240\u6709\u67b6\u6784\u7684\u5206\u9875\u6a21\u578b\uff0c\u5373\u4fbf\u67d0\u4e9b\u67b6 [&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":[281,284,283,282],"class_list":["post-3498","post","type-post","status-publish","format-standard","hentry","category-266","tag-281","tag-284","tag-283","tag-282"],"views":11514,"_links":{"self":[{"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/posts\/3498","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=3498"}],"version-history":[{"count":0,"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/posts\/3498\/revisions"}],"wp:attachment":[{"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/media?parent=3498"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/categories?post=3498"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/tags?post=3498"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}