[alsa-devel] [PATCH 1/2] ALSA: pcm: implement the anonymous dup (inode file descriptor)
Jaroslav Kysela
perex at perex.cz
Wed Jan 30 09:47:32 CET 2019
This patch implements new SNDRV_PCM_IOCTL_ANONYMOUS_DUP ioctl which
returns the new duplicated anonymous inode file descriptor
(anon_inode:snd-pcm) which can be passed to the restricted clients.
This patch is meant to be the alternative for the dma-buf interface. Both
implementation have some pros and cons:
anon_inode:dmabuf
- a bit standard export API for the DMA buffers
- fencing for the concurrent access [1]
- driver/kernel interface for the DMA buffer [1]
- multiple attach/detach scheme [1]
[1] the real usage for the sound PCM is unknown at the moment for this feature
anon_inode:snd-pcm
- simple (no problem with ref-counting, non-standard mmap implementation etc.)
- allow to use more sound interfaces for the file descriptor like status ioctls
- more fine grained security policies (another anon_inode name unshared with
other drivers)
Signed-off-by: Jaroslav Kysela <perex at perex.cz>
---
include/sound/pcm.h | 8 +++---
include/uapi/sound/asound.h | 3 +-
sound/core/oss/pcm_oss.c | 2 +-
sound/core/pcm.c | 13 ++++-----
sound/core/pcm_compat.c | 1 +
sound/core/pcm_native.c | 70 +++++++++++++++++++++++++++++++++++++++++----
6 files changed, 78 insertions(+), 19 deletions(-)
diff --git a/include/sound/pcm.h b/include/sound/pcm.h
index ca20f80f8976..b79ffaa0241d 100644
--- a/include/sound/pcm.h
+++ b/include/sound/pcm.h
@@ -579,11 +579,11 @@ static inline int snd_pcm_suspend_all(struct snd_pcm *pcm)
}
#endif
int snd_pcm_kernel_ioctl(struct snd_pcm_substream *substream, unsigned int cmd, void *arg);
-int snd_pcm_open_substream(struct snd_pcm *pcm, int stream, struct file *file,
- struct snd_pcm_substream **rsubstream);
+int snd_pcm_open_substream(struct snd_pcm *pcm, int stream, int subdevice,
+ struct file *file, struct snd_pcm_substream **rsubstream);
void snd_pcm_release_substream(struct snd_pcm_substream *substream);
-int snd_pcm_attach_substream(struct snd_pcm *pcm, int stream, struct file *file,
- struct snd_pcm_substream **rsubstream);
+int snd_pcm_attach_substream(struct snd_pcm *pcm, int stream, int subdevice,
+ struct file *file, struct snd_pcm_substream **rsubstream);
void snd_pcm_detach_substream(struct snd_pcm_substream *substream);
int snd_pcm_mmap_data(struct snd_pcm_substream *substream, struct file *file, struct vm_area_struct *area);
diff --git a/include/uapi/sound/asound.h b/include/uapi/sound/asound.h
index 404d4b9ffe76..ebc17d5a3490 100644
--- a/include/uapi/sound/asound.h
+++ b/include/uapi/sound/asound.h
@@ -153,7 +153,7 @@ struct snd_hwdep_dsp_image {
* *
*****************************************************************************/
-#define SNDRV_PCM_VERSION SNDRV_PROTOCOL_VERSION(2, 0, 14)
+#define SNDRV_PCM_VERSION SNDRV_PROTOCOL_VERSION(2, 0, 15)
typedef unsigned long snd_pcm_uframes_t;
typedef signed long snd_pcm_sframes_t;
@@ -576,6 +576,7 @@ enum {
#define SNDRV_PCM_IOCTL_TSTAMP _IOW('A', 0x02, int)
#define SNDRV_PCM_IOCTL_TTSTAMP _IOW('A', 0x03, int)
#define SNDRV_PCM_IOCTL_USER_PVERSION _IOW('A', 0x04, int)
+#define SNDRV_PCM_IOCTL_ANONYMOUS_DUP _IOWR('A', 0x05, int)
#define SNDRV_PCM_IOCTL_HW_REFINE _IOWR('A', 0x10, struct snd_pcm_hw_params)
#define SNDRV_PCM_IOCTL_HW_PARAMS _IOWR('A', 0x11, struct snd_pcm_hw_params)
#define SNDRV_PCM_IOCTL_HW_FREE _IO('A', 0x12)
diff --git a/sound/core/oss/pcm_oss.c b/sound/core/oss/pcm_oss.c
index d5b0d7ba83c4..2ed609b65c45 100644
--- a/sound/core/oss/pcm_oss.c
+++ b/sound/core/oss/pcm_oss.c
@@ -2420,7 +2420,7 @@ static int snd_pcm_oss_open_file(struct file *file,
if (! (f_mode & FMODE_READ))
continue;
}
- err = snd_pcm_open_substream(pcm, idx, file, &substream);
+ err = snd_pcm_open_substream(pcm, idx, -1, file, &substream);
if (err < 0) {
snd_pcm_oss_release_file(pcm_oss_file);
return err;
diff --git a/sound/core/pcm.c b/sound/core/pcm.c
index 4f45b3000347..af6f7fc3687b 100644
--- a/sound/core/pcm.c
+++ b/sound/core/pcm.c
@@ -918,15 +918,14 @@ static int snd_pcm_dev_free(struct snd_device *device)
return snd_pcm_free(pcm);
}
-int snd_pcm_attach_substream(struct snd_pcm *pcm, int stream,
- struct file *file,
+int snd_pcm_attach_substream(struct snd_pcm *pcm,
+ int stream, int subdevice, struct file *file,
struct snd_pcm_substream **rsubstream)
{
struct snd_pcm_str * pstr;
struct snd_pcm_substream *substream;
struct snd_pcm_runtime *runtime;
struct snd_card *card;
- int prefer_subdevice;
size_t size;
if (snd_BUG_ON(!pcm || !rsubstream))
@@ -940,7 +939,6 @@ int snd_pcm_attach_substream(struct snd_pcm *pcm, int stream,
return -ENODEV;
card = pcm->card;
- prefer_subdevice = snd_ctl_get_preferred_subdevice(card, SND_CTL_SUBDEV_PCM);
if (pcm->info_flags & SNDRV_PCM_INFO_HALF_DUPLEX) {
int opposite = !stream;
@@ -953,14 +951,14 @@ int snd_pcm_attach_substream(struct snd_pcm *pcm, int stream,
}
if (file->f_flags & O_APPEND) {
- if (prefer_subdevice < 0) {
+ if (subdevice < 0) {
if (pstr->substream_count > 1)
return -EINVAL; /* must be unique */
substream = pstr->substream;
} else {
for (substream = pstr->substream; substream;
substream = substream->next)
- if (substream->number == prefer_subdevice)
+ if (substream->number == subdevice)
break;
}
if (! substream)
@@ -974,8 +972,7 @@ int snd_pcm_attach_substream(struct snd_pcm *pcm, int stream,
for (substream = pstr->substream; substream; substream = substream->next) {
if (!SUBSTREAM_BUSY(substream) &&
- (prefer_subdevice == -1 ||
- substream->number == prefer_subdevice))
+ (subdevice == -1 || substream->number == subdevice))
break;
}
if (substream == NULL)
diff --git a/sound/core/pcm_compat.c b/sound/core/pcm_compat.c
index 946ab080ac00..22446cd574ee 100644
--- a/sound/core/pcm_compat.c
+++ b/sound/core/pcm_compat.c
@@ -675,6 +675,7 @@ static long snd_pcm_ioctl_compat(struct file *file, unsigned int cmd, unsigned l
case SNDRV_PCM_IOCTL_TSTAMP:
case SNDRV_PCM_IOCTL_TTSTAMP:
case SNDRV_PCM_IOCTL_USER_PVERSION:
+ case SNDRV_PCM_IOCTL_ANONYMOUS_DUP:
case SNDRV_PCM_IOCTL_HWSYNC:
case SNDRV_PCM_IOCTL_PREPARE:
case SNDRV_PCM_IOCTL_RESET:
diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
index 0bc4aa0ac9cf..8874a685f1e8 100644
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -37,6 +37,8 @@
#include <sound/minors.h>
#include <linux/uio.h>
#include <linux/delay.h>
+#include <linux/anon_inodes.h>
+#include <linux/syscalls.h>
#include "pcm_local.h"
@@ -2437,14 +2439,17 @@ void snd_pcm_release_substream(struct snd_pcm_substream *substream)
}
EXPORT_SYMBOL(snd_pcm_release_substream);
-int snd_pcm_open_substream(struct snd_pcm *pcm, int stream,
+int snd_pcm_open_substream(struct snd_pcm *pcm, int stream, int subdevice,
struct file *file,
struct snd_pcm_substream **rsubstream)
{
struct snd_pcm_substream *substream;
int err;
- err = snd_pcm_attach_substream(pcm, stream, file, &substream);
+ if (subdevice < 0 && pcm)
+ subdevice = snd_ctl_get_preferred_subdevice(pcm->card, SND_CTL_SUBDEV_PCM);
+
+ err = snd_pcm_attach_substream(pcm, stream, subdevice, file, &substream);
if (err < 0)
return err;
if (substream->ref_count > 1) {
@@ -2480,13 +2485,14 @@ EXPORT_SYMBOL(snd_pcm_open_substream);
static int snd_pcm_open_file(struct file *file,
struct snd_pcm *pcm,
- int stream)
+ int stream,
+ int subdevice)
{
struct snd_pcm_file *pcm_file;
struct snd_pcm_substream *substream;
int err;
- err = snd_pcm_open_substream(pcm, stream, file, &substream);
+ err = snd_pcm_open_substream(pcm, stream, subdevice, file, &substream);
if (err < 0)
return err;
@@ -2551,7 +2557,7 @@ static int snd_pcm_open(struct file *file, struct snd_pcm *pcm, int stream)
add_wait_queue(&pcm->open_wait, &wait);
mutex_lock(&pcm->open_mutex);
while (1) {
- err = snd_pcm_open_file(file, pcm, stream);
+ err = snd_pcm_open_file(file, pcm, stream, -1);
if (err >= 0)
break;
if (err == -EAGAIN) {
@@ -2595,6 +2601,9 @@ static int snd_pcm_release(struct inode *inode, struct file *file)
struct snd_pcm_file *pcm_file;
pcm_file = file->private_data;
+ /* a problem in the anonymous dup can hit the NULL pcm_file */
+ if (pcm_file == NULL)
+ return 0;
substream = pcm_file->substream;
if (snd_BUG_ON(!substream))
return -ENXIO;
@@ -2878,6 +2887,55 @@ static int snd_pcm_forward_ioctl(struct snd_pcm_substream *substream,
return result < 0 ? result : 0;
}
+static int snd_pcm_anonymous_dup(struct file *file,
+ struct snd_pcm_substream *substream,
+ int __user *arg)
+{
+ int fd;
+ int err;
+ int perm;
+ int flags;
+ struct file *nfile;
+ struct snd_pcm *pcm = substream->pcm;
+
+ if (get_user(perm, (int __user *)arg))
+ return -EFAULT;
+ if (perm < 0)
+ return -EPERM;
+ flags = file->f_flags & (O_ACCMODE | O_NONBLOCK);
+ flags |= O_APPEND | O_CLOEXEC;
+ fd = get_unused_fd_flags(flags);
+ if (fd < 0)
+ return fd;
+ nfile = anon_inode_getfile("snd-pcm", file->f_op, NULL, flags);
+ if (IS_ERR(nfile)) {
+ put_unused_fd(fd);
+ return PTR_ERR(nfile);
+ }
+ /* anon_inode_getfile() filters the O_APPEND flag out */
+ nfile->f_flags |= O_APPEND;
+ fd_install(fd, nfile);
+ if (!try_module_get(pcm->card->module)) {
+ err = -EFAULT;
+ goto __error1;
+ }
+ err = snd_card_file_add(substream->pcm->card, nfile);
+ if (err < 0)
+ goto __error2;
+ err = snd_pcm_open_file(nfile, substream->pcm,
+ substream->stream, substream->number);
+ if (err >= 0) {
+ put_user(fd, (int __user *)arg);
+ return 0;
+ }
+ snd_card_file_remove(substream->pcm->card, nfile);
+ __error2:
+ module_put(pcm->card->module);
+ __error1:
+ ksys_close(fd);
+ return err;
+}
+
static int snd_pcm_common_ioctl(struct file *file,
struct snd_pcm_substream *substream,
unsigned int cmd, void __user *arg)
@@ -2906,6 +2964,8 @@ static int snd_pcm_common_ioctl(struct file *file,
(unsigned int __user *)arg))
return -EFAULT;
return 0;
+ case SNDRV_PCM_IOCTL_ANONYMOUS_DUP:
+ return snd_pcm_anonymous_dup(file, substream, (int __user *)arg);
case SNDRV_PCM_IOCTL_HW_REFINE:
return snd_pcm_hw_refine_user(substream, arg);
case SNDRV_PCM_IOCTL_HW_PARAMS:
--
2.13.6
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