compat IOCTL

 

1. About compat IOCTL

64-bit kernel 상에서 동작하는 32-bit program은,            ioctl 호출 시, kernel이 ioctol을 .compat_ioctl로 divert   ex. const struct file_operations snd_pcm_f_ops[2] = { { … .unlocked_ioctl = snd_pcm_playback_ioctl, .compat_ioctl = snd_pcm_ioctl_compat, … }, …

 

 

2. Ex. Of compat IOCTL

snd_pcm_ioctl_compat (..., unsigned long arg) {                      void __user *argp = compat_ptr(arg);                      snd_pcm_playback_ioctl1(file, substream, cmd, argp);         }                snd_pcm_playback_ioctl1(..., void __user *arg) {                      struct snd_xferi xferi;                      struct snd_xferi __user *_xferi = arg;                        copy_from_user(&xferi, _xferi, sizeof(xferi))                                 result = snd_pcm_lib_write(substream, xferi.buf, xferi.frames);                      __put_user(result, &_xferi->result);         }

 

 

 

kernel config에서 아래 config를 enable 해 줘야 compat으로 동작함

CONFIG_COMPAT