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author | Baolin Wang <baolin.wang@linaro.org> | 2018-04-24 15:06:11 +0300 |
---|---|---|
committer | Arnd Bergmann <arnd@arndb.de> | 2019-12-12 00:06:15 +0300 |
commit | 3ddee7f88aaf2dee38f7016ac8fd48dd9fdb43e3 (patch) | |
tree | bd68506d27a4db945608bd80a7350dc5c3fa5716 /include/uapi/sound | |
parent | a4e7dd35b9dac21fa7b33e8788b51c7fbc7a49f1 (diff) | |
download | linux-3ddee7f88aaf2dee38f7016ac8fd48dd9fdb43e3.tar.xz |
ALSA: Avoid using timespec for struct snd_pcm_status
The struct snd_pcm_status will use 'timespec' type variables to record
timestamp, which is not year 2038 safe on 32bits system.
Userspace will use SNDRV_PCM_IOCTL_STATUS and SNDRV_PCM_IOCTL_STATUS_EXT
as commands to issue ioctl() to fill the 'snd_pcm_status' structure in
userspace. The command number is always defined through _IOR/_IOW/IORW,
so when userspace changes the definition of 'struct timespec' to use
64-bit types, the command number also changes.
Thus in the kernel, we now need to define two versions of each such ioctl
and corresponding ioctl commands to handle 32bit time_t and 64bit time_t
in native mode:
struct snd_pcm_status32 {
......
s32 trigger_tstamp_sec;
s32 trigger_tstamp_nsec;
......
s32 audio_tstamp_sec;
s32 audio_tstamp_nsec;
......
};
struct snd_pcm_status64 {
......
s32 trigger_tstamp_sec;
s32 trigger_tstamp_nsec;
......
s32 audio_tstamp_sec;
s32 audio_tstamp_nsec;
......
};
Moreover in compat file, we renamed or introduced new structures to handle
32bit/64bit time_t in compatible mode. The 'struct snd_pcm_status32' and
snd_pcm_status_user32() are used to handle 32bit time_t in compat mode.
'struct compat_snd_pcm_status64' and snd_pcm_status_user_compat64() are used
to handle 64bit time_t.
The implicit padding before timespec is made explicit to avoid incompatible
structure layout between 32-bit and 64-bit x86 due to the different
alignment requirements, and the snd_pcm_status structure is now hidden
from the kernel to avoid relying on the timespec definitio definitionn
Finally we can replace SNDRV_PCM_IOCTL_STATUS and SNDRV_PCM_IOCTL_STATUS_EXT
with new commands and introduce new functions to fill new 'struct snd_pcm_status64'
instead of using unsafe 'struct snd_pcm_status'. Then in future, the new
commands can be matched when userspace changes 'timespec' to 64bit type
to make a size change of 'struct snd_pcm_status'. When glibc changes time_t
to 64-bit, any recompiled program will issue ioctl commands that the kernel
does not understand without this patch.
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Diffstat (limited to 'include/uapi/sound')
-rw-r--r-- | include/uapi/sound/asound.h | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/include/uapi/sound/asound.h b/include/uapi/sound/asound.h index 40a23d8418fe..d2c88c098b20 100644 --- a/include/uapi/sound/asound.h +++ b/include/uapi/sound/asound.h @@ -456,8 +456,13 @@ enum { SNDRV_PCM_AUDIO_TSTAMP_TYPE_LAST = SNDRV_PCM_AUDIO_TSTAMP_TYPE_LINK_SYNCHRONIZED }; +#ifndef __KERNEL__ +/* explicit padding avoids incompatibility between i386 and x86-64 */ +typedef struct { unsigned char pad[sizeof(time_t) - sizeof(int)] __time_pad; + struct snd_pcm_status { snd_pcm_state_t state; /* stream state */ + __time_pad pad1; /* align to timespec */ struct timespec trigger_tstamp; /* time when stream was started/stopped/paused */ struct timespec tstamp; /* reference timestamp */ snd_pcm_uframes_t appl_ptr; /* appl ptr */ @@ -473,6 +478,7 @@ struct snd_pcm_status { __u32 audio_tstamp_accuracy; /* in ns units, only valid if indicated in audio_tstamp_data */ unsigned char reserved[52-2*sizeof(struct timespec)]; /* must be filled with zero */ }; +#endif struct snd_pcm_mmap_status { snd_pcm_state_t state; /* RO: state - SNDRV_PCM_STATE_XXXX */ |