user_access_begin 712 arch/x86/include/asm/uaccess.h static __must_check __always_inline bool user_access_begin(const void __user *ptr, size_t len) user_access_begin 719 arch/x86/include/asm/uaccess.h #define user_access_begin(a,b) user_access_begin(a,b) user_access_begin 368 include/linux/uaccess.h #define user_access_begin(ptr,len) access_ok(ptr, len)