ALSA: compress_offload: Add 64-bit safe timestamp infrastructure

The copied_total field in struct snd_compr_tstamp is a 32-bit
value that can overflow on long-running high-bitrate streams,
leading to incorrect calculations for buffer availablility.

This patch adds a 64-bit safe timestamping mechanism.
A new UAPI struct, snd_compr_tstamp64, is added which uses 64-bit
types for byte counters. The relevant ops structures across the
ASoC and core compress code are updated to use this new struct.
ASoC drivers are updated to use u64 counters.

Internal timestamps being u64 now, a compatibility function is added
to convert the 64-bit timestamp back to the 32-bit format for legacy
ioctl callers.

Reviewed-by: Miller Liang <millerliang@google.com>
Tested-by: Joris Verhaegen <verhaegen@google.com>
Signed-off-by: Joris Verhaegen <verhaegen@google.com>
Reviewed-by: Srinivas Kandagatla <srinivas.kandagatla@oss.qualcomm.com>
Reviewed-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Acked-by: Mark Brown <broonie@kernel.org>
Acked-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://patch.msgid.link/20250905091301.2711705-2-verhaegen@google.com

1 files changed, 35 insertions, 17 deletions

diff --git a/sound/core/compress_offload.c b/sound/core/compress_offload.c
index a66f258cafaa..d3164aa07158 100644
--- a/sound/core/compress_offload.c
+++ b/sound/core/compress_offload.c
@@ -176,14 +176,25 @@ static int snd_compr_free(struct inode *inode, struct file *f)
 	return 0;
 }
 
+static void
+snd_compr_tstamp32_from_64(struct snd_compr_tstamp *tstamp32,
+			   const struct snd_compr_tstamp64 *tstamp64)
+{
+	tstamp32->byte_offset = tstamp64->byte_offset;
+	tstamp32->copied_total = (u32)tstamp64->copied_total;
+	tstamp32->pcm_frames = (u32)tstamp64->pcm_frames;
+	tstamp32->pcm_io_frames = (u32)tstamp64->pcm_io_frames;
+	tstamp32->sampling_rate = tstamp64->sampling_rate;
+}
+
 static int snd_compr_update_tstamp(struct snd_compr_stream *stream,
-		struct snd_compr_tstamp *tstamp)
+				   struct snd_compr_tstamp64 *tstamp)
 {
 	if (!stream->ops->pointer)
 		return -ENOTSUPP;
 	stream->ops->pointer(stream, tstamp);
-	pr_debug("dsp consumed till %d total %d bytes\n",
-		tstamp->byte_offset, tstamp->copied_total);
+	pr_debug("dsp consumed till %u total %llu bytes\n", tstamp->byte_offset,
+		 tstamp->copied_total);
 	if (stream->direction == SND_COMPRESS_PLAYBACK)
 		stream->runtime->total_bytes_transferred = tstamp->copied_total;
 	else
@@ -194,8 +205,11 @@ static int snd_compr_update_tstamp(struct snd_compr_stream *stream,
 static size_t snd_compr_calc_avail(struct snd_compr_stream *stream,
 		struct snd_compr_avail *avail)
 {
+	struct snd_compr_tstamp64 tstamp64 = { 0 };
+
 	memset(avail, 0, sizeof(*avail));
-	snd_compr_update_tstamp(stream, &avail->tstamp);
+	snd_compr_update_tstamp(stream, &tstamp64);
+	snd_compr_tstamp32_from_64(&avail->tstamp, &tstamp64);
 	/* Still need to return avail even if tstamp can't be filled in */
 
 	if (stream->runtime->total_bytes_available == 0 &&
@@ -204,9 +218,9 @@ static size_t snd_compr_calc_avail(struct snd_compr_stream *stream,
 		pr_debug("detected init and someone forgot to do a write\n");
 		return stream->runtime->buffer_size;
 	}
-	pr_debug("app wrote %lld, DSP consumed %lld\n",
-			stream->runtime->total_bytes_available,
-			stream->runtime->total_bytes_transferred);
+	pr_debug("app wrote %llu, DSP consumed %llu\n",
+		 stream->runtime->total_bytes_available,
+		 stream->runtime->total_bytes_transferred);
 	if (stream->runtime->total_bytes_available ==
 				stream->runtime->total_bytes_transferred) {
 		if (stream->direction == SND_COMPRESS_PLAYBACK) {
@@ -223,7 +237,7 @@ static size_t snd_compr_calc_avail(struct snd_compr_stream *stream,
 	if (stream->direction == SND_COMPRESS_PLAYBACK)
 		avail->avail = stream->runtime->buffer_size - avail->avail;
 
-	pr_debug("ret avail as %lld\n", avail->avail);
+	pr_debug("ret avail as %llu\n", avail->avail);
 	return avail->avail;
 }
 
@@ -274,8 +288,7 @@ static int snd_compr_write_data(struct snd_compr_stream *stream,
 		      (app_pointer * runtime->buffer_size);
 
 	dstn = runtime->buffer + app_pointer;
-	pr_debug("copying %ld at %lld\n",
-			(unsigned long)count, app_pointer);
+	pr_debug("copying %lu at %llu\n", (unsigned long)count, app_pointer);
 	if (count < runtime->buffer_size - app_pointer) {
 		if (copy_from_user(dstn, buf, count))
 			return -EFAULT;
@@ -318,7 +331,7 @@ static ssize_t snd_compr_write(struct file *f, const char __user *buf,
 	}
 
 	avail = snd_compr_get_avail(stream);
-	pr_debug("avail returned %ld\n", (unsigned long)avail);
+	pr_debug("avail returned %lu\n", (unsigned long)avail);
 	/* calculate how much we can write to buffer */
 	if (avail > count)
 		avail = count;
@@ -374,7 +387,7 @@ static ssize_t snd_compr_read(struct file *f, char __user *buf,
 	}
 
 	avail = snd_compr_get_avail(stream);
-	pr_debug("avail returned %ld\n", (unsigned long)avail);
+	pr_debug("avail returned %lu\n", (unsigned long)avail);
 	/* calculate how much we can read from buffer */
 	if (avail > count)
 		avail = count;
@@ -443,7 +456,7 @@ static __poll_t snd_compr_poll(struct file *f, poll_table *wait)
 #endif
 
 	avail = snd_compr_get_avail(stream);
-	pr_debug("avail is %ld\n", (unsigned long)avail);
+	pr_debug("avail is %lu\n", (unsigned long)avail);
 	/* check if we have at least one fragment to fill */
 	switch (runtime->state) {
 	case SNDRV_PCM_STATE_DRAINING:
@@ -726,13 +739,18 @@ snd_compr_set_metadata(struct snd_compr_stream *stream, unsigned long arg)
 static inline int
 snd_compr_tstamp(struct snd_compr_stream *stream, unsigned long arg)
 {
-	struct snd_compr_tstamp tstamp = {0};
+	struct snd_compr_tstamp64 tstamp64 = { 0 };
+	struct snd_compr_tstamp tstamp32 = { 0 };
 	int ret;
 
-	ret = snd_compr_update_tstamp(stream, &tstamp);
-	if (ret == 0)
+	ret = snd_compr_update_tstamp(stream, &tstamp64);
+	if (ret == 0) {
+		snd_compr_tstamp32_from_64(&tstamp32, &tstamp64);
 		ret = copy_to_user((struct snd_compr_tstamp __user *)arg,
-			&tstamp, sizeof(tstamp)) ? -EFAULT : 0;
+				   &tstamp32, sizeof(tstamp32)) ?
+			      -EFAULT :
+			      0;
+	}
 	return ret;
 }