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setup.S->start_kernel(void) -> setup_arch -> paging_init()
(1)
接下来是paging_init,调用下面的pagetable_init,初始化页表然后重新加
载cr3,flush tlb,然后使用kmap_init为kmap_automic使用的变量求值,.....
不算复杂,重要的是free_area_init,初始化了zone-buddy内存管理系统(设置
所有页面都是PG_reserved(free_all_bootmem,负责重置)).
503 void __init paging_init(void)
504 {
505 #ifdef CONFIG_X86_PAE
506 set_nx();
507 if (nx_enabled)
508 printk("NX (Execute Disable) protection: active\n");
509 #endif
510
511 pagetable_init();
512
513 load_cr3(swapper_pg_dir);
514
515 #ifdef CONFIG_X86_PAE
516 /*
517 * We will bail out later - printk doesn't work right now so
518 * the user would just see a hanging kernel.
519 */
520 if (cpu_has_pae)
521 set_in_cr4(X86_CR4_PAE);
522 #endif
523 __flush_tlb_all(); //load 了cr3...
524
525 kmap_init();
526 }
(2)/mm/init.c
swapper_pg_dir 静态分配的
pgd_t swapper_pg_dir[1024];
//删了config_pae的代码
内核在使用虚拟空间:
+------------------------------------------------------------------
| 8K空洞
+------------------------------------------------------------------
| FIXADDR_TOP(0xffffe000UL) (include/asm-i386/fixmap.h)
| fixed map(每项4k虚存,见FIXADDR_SIZE)
| { //fix map 内容 (enum fixed_addresses)
| FIX_APIC_BASE,
| FIX_IO_APIC_BASE_0,
| FIX_IO_APIC_BASE_END = FIX_IO_APIC_BASE_0 + MAX_IO_APICS-1
|
| FIX_CO_CPU, /* Cobalt timer */
| FIX_CO_APIC, /* Cobalt APIC Redirection Table */
| FIX_LI_PCIA, /* Lithium PCI Bridge A */
| FIX_LI_PCIB, /* Lithium PCI Bridge B */
+--------------
#ifdef CONFIG_HIGHMEM /*为fix KMAP预留每cpu 8k的虚存,读写各4k*/
| FIX_KMAP_BEGIN, /* 主要用于kmap_atomic*/
| FIX_KMAP_END = FIX_KMAP_BEGIN+(KM_TYPE_NR*NR_CPUS)-1,
#endif
+--------------
| __end_of_fixed_addresses
| }
| FIXADDR_START (FIXADDR_TOP - FIXADDR_SIZE)
+--------------------------------------------------------------------
| VMALLOC_END (FIXADDR_START) (include/asm-i386/pgtable.h)
| +------------------
| | xxxxx: kmap 和 vmalloc 相互重叠,2.6已经修正
| | kmap 使用的4M虚存 (asm/highmem.h,LAST_PKMAP)
| | PKMAP_BASE (0xfe000000UL) (距离4G 32M)
| +------------------
| vmalloc 映射区
| VMALLOC_START (((unsigned long) high_memory + 2*VMALLOC_OFFSET-1)
| & \~(VMALLOC_OFFSET-1)) /*down align 8M */
+--------------------------------------------------------------------
| 约 8M 空洞
+--------------------------------------------------------------------
| high_memory (见003___arch_i386_mm_ioremap.c 对此的分析) ..一定映射到内核虚拟空间???,不可以是fixaddr么???
| 内核已经映射了的物理页面 MAX 896M
|
|
| 3G
+--------------------------------------------------------------------
| resoved for app 0-3G
+--------------------------------------------------------------------
(3) pagetable_init
339 static void __init pagetable_init (void)
340 {
341 unsigned long vaddr;
342 pgd_t *pgd_base = swapper_pg_dir;
351 /* Enable PSE if available */
352 if (cpu_has_pse) {
353 set_in_cr4(X86_CR4_PSE);
354 }
355
356 /* Enable PGE if available */
357 if (cpu_has_pge) {
358 set_in_cr4(X86_CR4_PGE);
359 __PAGE_KERNEL |= _PAGE_GLOBAL;
360 __PAGE_KERNEL_EXEC |= _PAGE_GLOBAL;
361 }
362
363 kernel_physical_mapping_init(pgd_base);
364 remap_numa_kva();
365
366 /*
367 * Fixed mappings, only the page table structure has to be
368 * created - mappings will be set by set_fixmap():
369 */
370 vaddr = __fix_to_virt(__end_of_fixed_addresses - 1) & PMD_MASK;
371 page_table_range_init(vaddr, 0, pgd_base); //这里用0,应该是超过了4G,或者2^64,回饶,所以是0
372
373 permanent_kmaps_init(pgd_base);
385 }
141 /* This maps the physical memory to kernel virtual address space, a total
142 * of max_low_pfn pages, by creating page tables starting from address
143 * PAGE_OFFSET.
144 */
PAGE_OFFSET 0xc0000000
//初始化页目录,页表,,
//1页目录 = 1 * (4k/4) * 4k = 4M, 896M,所以要用掉页目录表中的 896/4 = 225项
//pse设置话是一页面是4MB了,
//这样
(4) kernel_physical_mapping_init
145 static void __init kernel_physical_mapping_init(pgd_t *pgd_base)
146 {
147 unsigned long pfn;
148 pgd_t *pgd;
149 pmd_t *pmd;
150 pte_t *pte;
151 int pgd_idx, pmd_idx, pte_ofs;
152
153 pgd_idx = pgd_index(PAGE_OFFSET); //内核虚拟地址开始处....
154 pgd = pgd_base + pgd_idx;
155 pfn = 0;
156
157 for (; pgd_idx = max_low_pfn)
160 continue;
161 for (pmd_idx = 0; pmd_idx
76 /*
77 * Create a page table and place a pointer to it in a middle page
78 * directory entry.
79 */
80 static pte_t * __init one_page_table_init(pmd_t *pmd)
81 {
82 if (pmd_none(*pmd)) { //开始时,pmd为none,分配pte_t表...然后建立映射.
83 pte_t *page_table = (pte_t *) alloc_bootmem_low_pages(PAGE_SIZE);
84 set_pmd(pmd, __pmd(__pa(page_table) | _PAGE_TABLE)); //设置页面目录.
85 if (page_table != pte_offset_kernel(pmd, 0))
86 BUG();
87
88 return page_table;
89 }
90
91 return pte_offset_kernel(pmd, 0);
92 }
93
370 #define pte_offset_kernel(dir, address) \
371 ((pte_t *) pmd_page_kernel(*(dir)) + pte_index(address))
375 #define pmd_page_kernel(pmd) \
376 ((unsigned long) __va(pmd_val(pmd) & PAGE_MASK))
(5) page_table_range_init ,,,没设置pte...因为这是用来映射高端内存的或者别的用途?.要用的时候再设置pte项..而不是永久映射.
105 static void __init page_table_range_init (unsigned long start, unsigned long end, pgd_t *pgd_base)
106 {
107 pgd_t *pgd;
108 pud_t *pud;
109 pmd_t *pmd;
110 int pgd_idx, pmd_idx;
111 unsigned long vaddr;
112
113 vaddr = start;
114 pgd_idx = pgd_index(vaddr);
115 pmd_idx = pmd_index(vaddr);
116 pgd = pgd_base + pgd_idx;
117
118 for ( ; (pgd_idx
20 /*
21 * The "pgd_xxx()" functions here are trivial for a folded two-level
22 * setup: the pud is never bad, and a pud always exists (as it's folded
23 * into the pgd entry)
24 */
25 static inline int pgd_none(pgd_t pgd) { return 0; }
120 one_md_table_init(pgd);
121 pud = pud_offset(pgd, vaddr);
122 pmd = pmd_offset(pud, vaddr);
123 for (; (pmd_idx
(6) permanent_kmaps_init 没设置pte...因为这是用来映射高端内存的.要用的时候再设置pte项
/* *为fix KMAP预留每cpu 8k的虚存,读写各4k*/
46 /*
47 * Ordering is:
48 *
49 * FIXADDR_TOP
50 * fixed_addresses
51 * FIXADDR_START
52 * temp fixed addresses
53 * FIXADDR_BOOT_START
54 * Persistent kmap area
55 * PKMAP_BASE
56 * VMALLOC_END
57 * Vmalloc area
58 * VMALLOC_START
59 * high_memory
60 */
61 #define PKMAP_BASE ( (FIXADDR_BOOT_START - PAGE_SIZE*(LAST_PKMAP + 1)) & PMD_MASK )
253 static void __init permanent_kmaps_init(pgd_t *pgd_base)
254 {
255 pgd_t *pgd;
256 pud_t *pud;
257 pmd_t *pmd;
258 pte_t *pte;
259 unsigned long vaddr;
260
261 vaddr = PKMAP_BASE;
262 page_table_range_init(vaddr, vaddr + PAGE_SIZE*LAST_PKMAP, pgd_base); //还是调用上一个函数.设置好,页目录项
263
264 pgd = swapper_pg_dir + pgd_index(vaddr);
265 pud = pud_offset(pgd, vaddr);
266 pmd = pmd_offset(pud, vaddr);
267 pte = pte_offset_kernel(pmd, vaddr); //返回页表指针.
268 pkmap_page_table = pte;
269 }
41 #ifdef CONFIG_X86_PAE
42 #define LAST_PKMAP 512
43 #else
44 #define LAST_PKMAP 1024
45 #endif
所以kmap可以分配1024*4k= 4M空间.
(7) atomic 的高端内存...
242 static void __init kmap_init(void)
243 {
244 unsigned long kmap_vstart;
245
246 /* cache the first kmap pte */
247 kmap_vstart = __fix_to_virt(FIX_KMAP_BEGIN);
248 kmap_pte = kmap_get_fixmap_pte(kmap_vstart);
249
250 kmap_prot = PAGE_KERNEL;
251 }
252
(8)vmalloc的区间没有建立映射..
应该vmalloc时建立映射.
本文来自ChinaUnix博客,如果查看原文请点:http://blog.chinaunix.net/u/17526/showart_1079649.html |
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