Linux内核高-低端内存设置代码跟踪（ARM构架）

和vmalloc_min）后，内核通过sanity_check_meminfo函数自动去通过vmalloc_min信息来初始化每个meminfo.bank[？]中的highmem成员。此过程中如果有必要，将可能会改变meminfo中的bank数组。处理函数位于mmu.c (arch\arm\mm)：

1. static phys_addr_t lowmem_limit __initdata = 0;
3. void __init sanity_check_meminfo(void)
4. {
5. int i, j, highmem = 0;
7. for (i = 0, j = 0; i < meminfo.nr_banks; i++) {
8. struct membank *bank = &meminfo.bank[j];
9. *bank = meminfo.bank[i];
11. #ifdef CONFIG_HIGHMEM
12. if (__va(bank->start) >= vmalloc_min ||
13. __va(bank->start) < (void *)PAGE_OFFSET)
14. highmem = 1;
16. bank->highmem = highmem;
18. /*
19. * Split those memory banks which are partially overlapping
20. * the vmalloc area greatly simplifying things later.
21. */
22. if (__va(bank->start) < vmalloc_min &&
23. bank->size > vmalloc_min - __va(bank->start)) {
24. if (meminfo.nr_banks >= NR_BANKS) {
25. printk(KERN_CRIT "NR_BANKS too low, "
26. "ignoring high memory\n");
27. } else {
28. memmove(bank + 1, bank,
29. (meminfo.nr_banks - i) * sizeof(*bank));
30. meminfo.nr_banks++;
31. i++;
32. bank[1].size -= vmalloc_min - __va(bank->start);
33. bank[1].start = __pa(vmalloc_min - 1) + 1;
34. bank[1].highmem = highmem = 1;
35. j++;
36. }
37. bank->size = vmalloc_min - __va(bank->start);
38. }
39. #else
40. bank->highmem = highmem;
42. /*
43. * Check whether this memory bank would entirely overlap
44. * the vmalloc area.
45. */
46. if (__va(bank->start) >= vmalloc_min ||
47. __va(bank->start) < (void *)PAGE_OFFSET) {
48. printk(KERN_NOTICE "Ignoring RAM at %.8llx-%.8llx "
49. "(vmalloc region overlap).\n",
50. (unsigned long long)bank->start,
51. (unsigned long long)bank->start + bank->size - 1);
52. continue;
53. }
55. /*
56. * Check whether this memory bank would partially overlap
57. * the vmalloc area.
58. */
59. if (__va(bank->start + bank->size) > vmalloc_min ||
60. __va(bank->start + bank->size) < __va(bank->start)) {
61. unsigned long newsize = vmalloc_min - __va(bank->start);
62. printk(KERN_NOTICE "Truncating RAM at %.8llx-%.8llx "
63. "to -%.8llx (vmalloc region overlap).\n",
64. (unsigned long long)bank->start,
65. (unsigned long long)bank->start + bank->size - 1,
66. (unsigned long long)bank->start + newsize - 1);
67. bank->size = newsize;
68. }
69. #endif
70. if (!bank->highmem && bank->start + bank->size > lowmem_limit)
71. lowmem_limit = bank->start + bank->size;
73. j++;
74. }
75. #ifdef CONFIG_HIGHMEM
76. if (highmem) {
77. const char *reason = NULL;
79. if (cache_is_vipt_aliasing()) {
80. /*
81. * Interactions between kmap and other mappings
82. * make highmem support with aliasing VIPT caches
83. * rather difficult.
84. */
85. reason = "with VIPT aliasing cache";
86. }
87. if (reason) {
88. printk(KERN_CRIT "HIGHMEM is not supported %s, ignoring high memory\n",
89. reason);
90. while (j > 0 && meminfo.bank[j - 1].highmem)
91. j--;
92. }
93. }
94. #endif
95. meminfo.nr_banks = j;
96. memblock_set_current_limit(lowmem_limit);
97. }

（3）最后必须做的就是排序了，完成了这个工作就可以完全被我们上面提到的find_limits函数使用了，而这个工作就放在了接下来的arm_memblock_init(&meminfo, mdesc);中的一开头：

1. static int __init meminfo_cmp(const void *_a, const void *_b)
2. {
3. const struct membank *a = _a, *b = _b;
4. long cmp = bank_pfn_start(a) - bank_pfn_start(b);
5. return cmp < 0 ? -1 : cmp > 0 ? 1 : 0;
6. }
8. void __init arm_memblock_init(struct meminfo *mi, struct machine_desc *mdesc)
9. {
10. int i;
12. sort(&meminfo.bank, meminfo.nr_banks, sizeof(meminfo.bank[0]), meminfo_cmp, NULL);
14. memblock_init();
15. for (i = 0; i < mi->nr_banks; i++)
16. memblock_add(mi->bank[i].start, mi->bank[i].size);
18. /* Register the kernel text, kernel data and initrd with memblock. */
19. #ifdef CONFIG_XIP_KERNEL
20. memblock_reserve(__pa(_sdata), _end - _sdata);
21. #else
22. memblock_reserve(__pa(_stext), _end - _stext);
23. #endif
24. #ifdef CONFIG_BLK_DEV_INITRD
25. if (phys_initrd_size &&
26. !memblock_is_region_memory(phys_initrd_start, phys_initrd_size)) {
27. pr_err("INITRD: 0xlx+0xlx is not a memory region - disabling initrd\n",
28. phys_initrd_start, phys_initrd_size);