Linux記憶體管理之malloc實現
程序虛擬地址空間由一個一個VMA來表示,這裡先接收VMA相關操作.
1.1 查詢VMA函式find_vma()
struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
找到的vma結果需滿足條件:
/* 找到前一個VMA,基於find_vma實現*/
struct vm_area_struct *
find_vma_prev(struct mm_struct *mm, unsigned long addr,struct vm_area_struct **pprev)
/*找到一個與start和end重合的vma */
static inline struct vm_area_struct * find_vma_intersection(struct mm_struct * mm, unsigned long start_addr, unsigned long end_addr)
1.2 插入vma
int insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
1.3 合併VMA
struct vm_area_struct *vma_merge(struct mm_struct *mm,
struct vm_area_struct *prev, unsigned long addr,
unsigned long end, unsigned long vm_flags,
struct anon_vma *anon_vma, struct file *file,
pgoff_t pgoff, struct mempolicy *policy,
struct vm_userfaultfd_ctx vm_userfaultfd_ctx,
const char __user *anon_name)
2. malloc核心實現
核心通過brk系統呼叫實現malloc函式功能.
4.幾個重要函式
給使用者空間地址分配物理頁面,並進行對映。
long get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
unsigned long start, unsigned long nr_pages, int write,
int force, struct page **pages, struct vm_area_struct **vmas)
根據使用者空間虛擬地址,返回page結構
static inline struct page *follow_page(struct vm_area_struct *vma,
unsigned long address, unsigned int foll_flags)
根據PTE獲取page結構
struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
pte_t pte)