Re: [alsa-devel] [RFC PATCH 7/7] sound: core: Avoid using timespec for struct snd_timer_tread

On 21 September 2017 at 21:09, Arnd Bergmann arnd@arndb.de wrote:

On Thu, Sep 21, 2017 at 8:18 AM, Baolin Wang baolin.wang@linaro.org wrote:

...

+static int snd_timer_user_tread(void __user *argp, struct snd_timer_user *tu,

•                           unsigned int cmd)
  

+{

•   int __user *p = argp;
  

•   int xarg, old_tread;
  

•   if (tu->timeri) /* too late */
  

•           return -EBUSY;
  

•   if (get_user(xarg, p))
  

•           return -EFAULT;
  

•   old_tread = tu->tread;
  

+#if __BITS_PER_LONG == 64

•   tu->tread = xarg ? 2 : 0;
  

+#ifdef IA32_EMULATION

•   tu->tread = xarg ? 3 : 0;
  

+#endif +#else

•   if (cmd == SNDRV_TIMER_IOCTL_TREAD64)
  

•           tu->tread = xarg ? 2 : 0;
  

•   else
  

•           tu->tread = xarg ? 1 : 0;
  

+#endif

The 64-bit case looks broken here:

• The tread flag is different for compat and native mode, so you must pass a flag to identify whether you are called from __snd_timer_user_ioctl or from snd_timer_user_ioctl_compat().

I have some confusion here. For 64-bit, we will set tu->tread = 2 no matter it is native mode or compat mode, only we will set tu->tread = 3 for x86_32 in compat mode, right? So I think we do not need to identify whether called from native mode or compat mode.

• On x86, you have to check whether calling user space process uses the i386 or the x32 ABI by checking in_x32_syscall()

Make sense.