On 2021/6/23 10:50, Al Viro wrote:
On Wed, Jun 23, 2021 at 10:39:31AM +0800, Chen Huang wrote:Then when kernel handles the alignment_fault, it will not panic. As the arm64 memory model spec said, when the address is not a multiple of the element size, the access is unaligned. Unaligned accesses are allowed to addresses marked as Normal, but not to Device regions. An unaligned access to a Device region will trigger an exception (alignment fault). do_alignment_fault do_bad_area __do_kernel_fault fixup_exception But that fixup cann't handle the unaligned copy, so the copy_page_from_iter_atomic returns 0 and traps in loop.Looks like you need to fix your raw_copy_from_user(), then... .
Exit loop when iov_iter_copy_from_user_atomic() returns 0. This should solve the problem, too, and it's easier. Thanks. Xiaoming Ni
