訪問 other process | 使用者 空間

 往任意USER PROCESS的記憶體讀寫

kernel/ptrace.c :
/*
 * Access another process' address space.
 * Source/target buffer must be kernel space,
 * Do not walk the page table directly, use get_user_pages
 */

int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
/
/
get_user_pages
/
/
copy_to_user_page
copy_from_user_page

mm/memory.c  ：
int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                unsigned long start, int len, int write, int force,
                struct page **pages, struct vm_area_struct **vmas)
根據start（即指定的開始地址）找到vma，並把地址和page關聯

例子 ：

static int proc_pid_environ(struct task_struct *task, char * buffer)
{
        int res = 0;
        struct mm_struct *mm = get_task_mm(task);
        if (mm) {
                unsigned int len = mm->env_end - mm->env_start;
                if (len > PAGE_SIZE)
                        len = PAGE_SIZE;
                res = access_process_vm(task, mm->env_start, buffer, len, 0);

//mm->env_start     是int  為env開始地址， 把指定process的env內容讀到buffer裡