copy_to_user在哪裏定義

Question

在Linux系統上，哪裏定義和實現了函數copy_to_user和copy_from_user？

Answer 1

它在asm/uaccess.h定義，例如，在/usr/src/linux-3.0.6-gentoo/include/asm-generic/uaccess.h：

static inline long copy_from_user(void *to, 
       const void __user * from, unsigned long n) 
{ 
     might_sleep(); 
     if (access_ok(VERIFY_READ, from, n)) 
       return __copy_from_user(to, from, n); 
     else 
       return n; 
} 

static inline long copy_to_user(void __user *to, 
       const void *from, unsigned long n) 
{ 
     might_sleep(); 
     if (access_ok(VERIFY_WRITE, to, n)) 
       return __copy_to_user(to, from, n); 
     else 
       return n; 
} 

---

而且__copy_to_user ：

#ifndef __copy_to_user 
static inline __must_check long __copy_to_user(void __user *to, 
       const void *from, unsigned long n) 
{ 
     if (__builtin_constant_p(n)) { 
       switch(n) { 
       case 1: 
         *(u8 __force *)to = *(u8 *)from; 
         return 0; 
       case 2: 
         *(u16 __force *)to = *(u16 *)from; 
         return 0; 
       case 4: 
         *(u32 __force *)to = *(u32 *)from; 
         return 0; 
#ifdef CONFIG_64BIT 
       case 8: 
         *(u64 __force *)to = *(u64 *)from; 
         return 0; 
#endif 
       default: 
         break; 
       } 
     } 

     memcpy((void __force *)to, from, n); 
     return 0; 
} 
#endif