1. struct mm_struct {
2. struct vm_area_struct * mmap;        /* 内存区域链表list of VMAs */
3. struct rb_root mm_rb;                /* VMA形成的红黑树*/
4. struct vm_area_struct * mmap_cache;    /* 最近使用的内存区域last find_vma result */
5. #ifdef CONFIG_MMU
6. unsigned long (*get_unmapped_area) (struct file *filp,
7. unsigned long addr, unsigned long len,
8. unsigned long pgoff, unsigned long flags);
9. void (*unmap_area) (struct mm_struct *mm, unsigned long addr);
10. #endif
11. unsigned long mmap_base;        /* base of mmap area */
12. unsigned long task_size;        /* size of task vm space */
13. unsigned long cached_hole_size;     /* if non-zero, the largest hole below free_area_cache */
14. unsigned long free_area_cache;        /* 地址空间第一个空洞first hole of size cached_hole_size or larger */
15. pgd_t * pgd; /*页全局目录*/
16. atomic_t mm_users;            /* 使用地址空间的用户数How many users with user space? */
17. atomic_t mm_count;            /* 主使用计数器How many references to "struct mm_struct" (users count as 1) */
18. int map_count;                /* number of VMAs */
19. struct rw_semaphore mmap_sem; /*内存区域的信号量*/
20. spinlock_t page_table_lock;        /* 页表锁Protects page tables and some counters */
21. 
22. struct list_head mmlist;        /*所有mm_struct形成的双向链表 List of maybe swapped mm's.    These are globally strung
23. * together off init_mm.mmlist, and are protected
24. * by mmlist_lock
25. */
26. 
27. 
28. unsigned long hiwater_rss;    /* High-watermark of RSS usage */
29. unsigned long hiwater_vm;    /* High-water virtual memory usage */
30. 
31. /*全部页面数目，上锁的页面数目*/
32. unsigned long total_vm, locked_vm, shared_vm, exec_vm;
33. unsigned long stack_vm, reserved_vm, def_flags, nr_ptes;
34. /*代码段的开始地址，结束地址；数据段的首地址和结束地址*/
35. unsigned long start_code, end_code, start_data, end_data;
36. /*堆的首地址，堆的尾地址*/
37. unsigned long start_brk, brk, start_stack;
38. /*命令行参数的首地址和结束地址，环境变量的首地址和结束地址*/
39. unsigned long arg_start, arg_end, env_start, env_end;
40. 
41. unsigned long saved_auxv[AT_VECTOR_SIZE]; /* for /proc/PID/auxv */
42. 
43. /*
44. * Special counters, in some configurations protected by the
45. * page_table_lock, in other configurations by being atomic.
46. */
47. struct mm_rss_stat rss_stat;
48. 
49. struct linux_binfmt *binfmt;
50. 
51. cpumask_t cpu_vm_mask;
52. 
53. /* Architecture-specific MM context */
54. mm_context_t context;
55. 
56. /* Swap token stuff */
57. /*
58. * Last value of global fault stamp as seen by this process.
59. * In other words, this value gives an indication of how long
60. * it has been since this task got the token.
61. * Look at mm/thrash.c
62. */
63. unsigned int faultstamp;
64. unsigned int token_priority;
65. unsigned int last_interval;
66. 
67. unsigned long flags; /* Must use atomic bitops to access the bits */
68. 
69. struct core_state *core_state; /* coredumping support */
70. #ifdef CONFIG_AIO
71. spinlock_t        ioctx_lock;
72. struct hlist_head    ioctx_list;
73. #endif
74. #ifdef CONFIG_MM_OWNER
75. /*
76. * "owner" points to a task that is regarded as the canonical
77. * user/owner of this mm. All of the following must be true in
78. * order for it to be changed:
79. *
80. * current == mm->owner
81. * current->mm != mm
82. * new_owner->mm == mm
83. * new_owner->alloc_lock is held
84. */
85. struct task_struct *owner;
86. #endif
87. 
88. #ifdef CONFIG_PROC_FS
89. /* store ref to file /proc/<pid>/exe symlink points to */
90. struct file *exe_file;
91. unsigned long num_exe_file_vmas;
92. #endif
93. #ifdef CONFIG_MMU_NOTIFIER
94. struct mmu_notifier_mm *mmu_notifier_mm;
95. #endif
96. };

1. if (clone_flags & CLONE_VM) {
2. //current 是父进程，而tsk在fork()指向期间是子进程
3. atomic_inc(¤t->mm->mm_users);
4. tsk->mm = current->mm;
5. }

1. /*
2. * This struct defines a memory VMM memory area. There is one of these
3. * per VM-area/task. A VM area is any part of the process virtual memory
4. * space that has a special rule for the page-fault handlers (ie a shared
5. * library, the executable area etc).
6. */
7. struct vm_area_struct {
8. struct mm_struct * vm_mm;    /* 相关的mm_struct结构体The address space we belong to. */
9. unsigned long vm_start;        /* 区间首地址Our start address within vm_mm. */
10. unsigned long vm_end;        /* 区间尾地址The first byte after our end address
11. within vm_mm. */
12. 
13. /* linked list of VM areas per task, sorted by address */
14. struct vm_area_struct *vm_next, *vm_prev; //VMA链表
15. 
16. pgprot_t vm_page_prot;        /* 访问控制权限Access permissions of this VMA. */
17. unsigned long vm_flags;        /* 标志:内存区域标志的信息和行为Flags, see mm.h. */
18. struct rb_node vm_rb; //树上该VMA的节点
19. 
20. /*
21. * For areas with an address space and backing store,
22. * linkage into the address_space->i_mmap prio tree, or
23. * linkage to the list of like vmas hanging off its node, or
24. * linkage of vma in the address_space->i_mmap_nonlinear list.
25. */
26. union {
27. struct {
28. struct list_head list;
29. void *parent;    /* aligns with prio_tree_node parent */
30. struct vm_area_struct *head;
31. } vm_set;
32. 
33. struct raw_prio_tree_node prio_tree_node;
34. } shared;
35. 
36. /*
37. * A file's MAP_PRIVATE vma can be in both i_mmap tree and anon_vma
38. * list, after a COW of one of the file pages.    A MAP_SHARED vma
39. * can only be in the i_mmap tree. An anonymous MAP_PRIVATE, stack
40. * or brk vma (with NULL file) can only be in an anon_vma list.
41. */
42. struct list_head anon_vma_chain; /* Serialized by mmap_sem &
43. * page_table_lock */
44. struct anon_vma *anon_vma;    /* Serialized by page_table_lock */
45. 
46. /* Function pointers to deal with this struct. */
47. const struct vm_operations_struct *vm_ops; //相关的操作链表
48. 
49. /* Information about our backing store: */
50. unsigned long vm_pgoff;        /*文件中偏移量 Offset (within vm_file) in PAGE_SIZE
51. units, *not* PAGE_CACHE_SIZE */
52. struct file * vm_file;        /* 被映射的文件File we map to (can be NULL). */
53. void * vm_private_data;        /* 私有数据was vm_pte (shared mem) */
54. unsigned long vm_truncate_count;/* truncate_count or restart_addr */
55. 
56. #ifndef CONFIG_MMU
57. struct vm_region *vm_region;    /* NOMMU mapping region */
58. #endif
59. #ifdef CONFIG_NUMA
60. struct mempolicy *vm_policy;    /* NUMA policy for the VMA */
61. #endif
62. };

1. struct vm_operations_struct {
2. //当指定的内存区域被加入到一个地址空间时，该函数被调用
3. void (*open)(struct vm_area_struct * area);
4. //当指定的内存区域从地址空间删除时，该函数调用
5. void (*close)(struct vm_area_struct * area);
6. //当没有出现在屋里内存中的页面被访问时，该函数被页面故障处理调用
7. int (*fault)(struct vm_area_struct *vma, struct vm_fault *vmf);
8. 
9. /* notification that a previously read-only page is about to become
10. * writable, if an error is returned it will cause a SIGBUS */
11. //当某个页面为只读页面时，该函数被页面故障处理调用
12. int (*page_mkwrite)(struct vm_area_struct *vma, struct vm_fault *vmf);
13. 
14. /* called by access_process_vm when get_user_pages() fails, typically
15. * for use by special VMAs that can switch between memory and hardware
16. */
17. //当get_user_pages()函数调用失败时，该函数被access_process_vm()函数调用
18. int (*access)(struct vm_area_struct *vma, unsigned long addr,
19. void *buf, int len, int write);
20. …
21. };

1. #include <stdio.h>
2. int main(void)
3. {
4. printf("hello,world!\r\n");
5. while (1);
6. return 0;
7. }

1. /* Look up the first VMA which satisfies addr < vm_end, NULL if none. */
2. struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
3. {
4. struct vm_area_struct *vma = NULL;
5. 
6. if (mm) {
7. /* Check the cache first. */
8. /* (Cache hit rate is typically around 35%.) */
9. vma = mm->mmap_cache;
10. if (!(vma && vma->vm_end > addr && vma->vm_start <= addr)) {
11. struct rb_node * rb_node;
12. 
13. rb_node = mm->mm_rb.rb_node;
14. vma = NULL;
15. 
16. while (rb_node) {
17. struct vm_area_struct * vma_tmp;
18. 
19. vma_tmp = rb_entry(rb_node,
20. struct vm_area_struct, vm_rb);
21. 
22. if (vma_tmp->vm_end > addr) {
23. vma = vma_tmp;
24. if (vma_tmp->vm_start <= addr)
25. break;
26. rb_node = rb_node->rb_left;
27. } else
28. rb_node = rb_node->rb_right;
29. }
30. if (vma)
31. mm->mmap_cache = vma;
32. }
33. }
34. return vma;
35. }

1. /* Look up the first VMA which intersects the interval start_addr..end_addr-1,
2. NULL if none. Assume start_addr < end_addr. */
3. static inline struct vm_area_struct * find_vma_intersection(struct mm_struct * mm, unsigned long start_addr, unsigned long end_addr)
4. {
5. struct vm_area_struct * vma = find_vma(mm,start_addr);
6. 
7. if (vma && end_addr <= vma->vm_start)
8. vma = NULL;
9. return vma;
10. }

1. asmlinkage long sys_munmap(unsigned long addr,size_t len)
2. {
3. int ret;
4. struct mm_struct *mm;
5. 
6. mm = current->mm;
7. down_write(&mm->mmap_sem);
8. ret = do_munmap(mm,addr,len);
9. up_write(&mm->mmap_sem);
10. 
11. return ret;
12. }