x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

When using eBPF to probe CS CALL instructions within a function,
a crash can be triggered.

The eBPF tool probes offset 257 of the __hrtimer_run_queues()
function:

<__hrtimer_run_queues+249>:  nopl   0x0(%rax,%rax,1)
<__hrtimer_run_queues+254>:  mov    %r14,%rdi
<__hrtimer_run_queues+257>:  cs call <__x86_indirect_thunk_r12>
<__hrtimer_run_queues+263>:  mov    %eax,%r12d
<__hrtimer_run_queues+266>:  xchg   %ax,%ax
<__hrtimer_run_queues+268>:  mov    %r13,%rdi

Which triggers this crash:

  BUG: unable to handle page fault for address: 00000000000f41c9
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: 0002 [#1] SMP NOPTI
  CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P
  RIP: 0010:__hrtimer_run_queues+0x106/0x230

Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is
at the 6th byte of the above CS CALL instruction. Since the CS CALL
instruction occupies 6 bytes, the exception occurred in the middle of that
call instruction.

The root cause is that when using eBPF tools to probe in the middle of a
function, a kprobe with INT3 is used as the underlying implementation.

During single-step emulation of the original CALL instruction,
int3_emulate_call() assumes that the probed CALL instruction is 5 bytes
long. However, the actual CS-prefixed CALL instruction occupies 6 bytes,
so it constructs an incorrect exception return address. When the CPU
returns from the kprobe handler, the next instruction to be executed is at
the address of the last byte of that CS CALL instruction. Coincidentally,
starting from that address, the CPU fetches and decodes a completely
different instruction, which ultimately triggers a kernel crash.

Fix the issue by using the actual instruction length obtained from
the instruction decoder when constructing the exception return
address, rather than relying on the hardcoded CALL_INSN_SIZE macro.

[ mingo: Refined the changelog ]

Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step")
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

1 files changed, 733 insertions, 0 deletions

diff --git a/sound/firewire/isight.c b/sound/firewire/isight.c
new file mode 100644
index 000000000..f16e2e223
--- /dev/null
+++ b/sound/firewire/isight.c
@@ -0,0 +1,733 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Apple iSight audio driver
+ *
+ * Copyright (c) Clemens Ladisch <clemens@ladisch.de>
+ */
+
+#include <asm/byteorder.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/firewire.h>
+#include <linux/firewire-constants.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/string.h>
+#include <sound/control.h>
+#include <sound/core.h>
+#include <sound/initval.h>
+#include <sound/pcm.h>
+#include <sound/tlv.h>
+#include "lib.h"
+#include "iso-resources.h"
+#include "packets-buffer.h"
+
+#define OUI_APPLE		0x000a27
+#define MODEL_APPLE_ISIGHT	0x000008
+#define SW_ISIGHT_AUDIO		0x000010
+
+#define REG_AUDIO_ENABLE	0x000
+#define  AUDIO_ENABLE		0x80000000
+#define REG_DEF_AUDIO_GAIN	0x204
+#define REG_GAIN_RAW_START	0x210
+#define REG_GAIN_RAW_END	0x214
+#define REG_GAIN_DB_START	0x218
+#define REG_GAIN_DB_END		0x21c
+#define REG_SAMPLE_RATE_INQUIRY	0x280
+#define REG_ISO_TX_CONFIG	0x300
+#define  SPEED_SHIFT		16
+#define REG_SAMPLE_RATE		0x400
+#define  RATE_48000		0x80000000
+#define REG_GAIN		0x500
+#define REG_MUTE		0x504
+
+#define MAX_FRAMES_PER_PACKET	475
+
+#define QUEUE_LENGTH		20
+
+struct isight {
+	struct snd_card *card;
+	struct fw_unit *unit;
+	struct fw_device *device;
+	u64 audio_base;
+	struct snd_pcm_substream *pcm;
+	struct mutex mutex;
+	struct iso_packets_buffer buffer;
+	struct fw_iso_resources resources;
+	struct fw_iso_context *context;
+	bool pcm_active;
+	bool pcm_running;
+	bool first_packet;
+	int packet_index;
+	u32 total_samples;
+	unsigned int buffer_pointer;
+	unsigned int period_counter;
+	s32 gain_min, gain_max;
+	unsigned int gain_tlv[4];
+};
+
+struct audio_payload {
+	__be32 sample_count;
+	__be32 signature;
+	__be32 sample_total;
+	__be32 reserved;
+	__be16 samples[2 * MAX_FRAMES_PER_PACKET];
+};
+
+MODULE_DESCRIPTION("iSight audio driver");
+MODULE_AUTHOR("Clemens Ladisch <clemens@ladisch.de>");
+MODULE_LICENSE("GPL");
+
+static struct fw_iso_packet audio_packet = {
+	.payload_length = sizeof(struct audio_payload),
+	.interrupt = 1,
+	.header_length = 4,
+};
+
+static void isight_update_pointers(struct isight *isight, unsigned int count)
+{
+	struct snd_pcm_runtime *runtime = isight->pcm->runtime;
+	unsigned int ptr;
+
+	smp_wmb(); /* update buffer data before buffer pointer */
+
+	ptr = isight->buffer_pointer;
+	ptr += count;
+	if (ptr >= runtime->buffer_size)
+		ptr -= runtime->buffer_size;
+	WRITE_ONCE(isight->buffer_pointer, ptr);
+
+	isight->period_counter += count;
+	if (isight->period_counter >= runtime->period_size) {
+		isight->period_counter -= runtime->period_size;
+		snd_pcm_period_elapsed(isight->pcm);
+	}
+}
+
+static void isight_samples(struct isight *isight,
+			   const __be16 *samples, unsigned int count)
+{
+	struct snd_pcm_runtime *runtime;
+	unsigned int count1;
+
+	if (!READ_ONCE(isight->pcm_running))
+		return;
+
+	runtime = isight->pcm->runtime;
+	if (isight->buffer_pointer + count <= runtime->buffer_size) {
+		memcpy(runtime->dma_area + isight->buffer_pointer * 4,
+		       samples, count * 4);
+	} else {
+		count1 = runtime->buffer_size - isight->buffer_pointer;
+		memcpy(runtime->dma_area + isight->buffer_pointer * 4,
+		       samples, count1 * 4);
+		samples += count1 * 2;
+		memcpy(runtime->dma_area, samples, (count - count1) * 4);
+	}
+
+	isight_update_pointers(isight, count);
+}
+
+static void isight_pcm_abort(struct isight *isight)
+{
+	if (READ_ONCE(isight->pcm_active))
+		snd_pcm_stop_xrun(isight->pcm);
+}
+
+static void isight_dropped_samples(struct isight *isight, unsigned int total)
+{
+	struct snd_pcm_runtime *runtime;
+	u32 dropped;
+	unsigned int count1;
+
+	if (!READ_ONCE(isight->pcm_running))
+		return;
+
+	runtime = isight->pcm->runtime;
+	dropped = total - isight->total_samples;
+	if (dropped < runtime->buffer_size) {
+		if (isight->buffer_pointer + dropped <= runtime->buffer_size) {
+			memset(runtime->dma_area + isight->buffer_pointer * 4,
+			       0, dropped * 4);
+		} else {
+			count1 = runtime->buffer_size - isight->buffer_pointer;
+			memset(runtime->dma_area + isight->buffer_pointer * 4,
+			       0, count1 * 4);
+			memset(runtime->dma_area, 0, (dropped - count1) * 4);
+		}
+		isight_update_pointers(isight, dropped);
+	} else {
+		isight_pcm_abort(isight);
+	}
+}
+
+static void isight_packet(struct fw_iso_context *context, u32 cycle,
+			  size_t header_length, void *header, void *data)
+{
+	struct isight *isight = data;
+	const struct audio_payload *payload;
+	unsigned int index, length, count, total;
+	int err;
+
+	if (isight->packet_index < 0)
+		return;
+	index = isight->packet_index;
+	payload = isight->buffer.packets[index].buffer;
+	length = be32_to_cpup(header) >> 16;
+
+	if (likely(length >= 16 &&
+		   payload->signature == cpu_to_be32(0x73676874/*"sght"*/))) {
+		count = be32_to_cpu(payload->sample_count);
+		if (likely(count <= (length - 16) / 4 &&
+			   count <= MAX_FRAMES_PER_PACKET)) {
+			total = be32_to_cpu(payload->sample_total);
+			if (unlikely(total != isight->total_samples)) {
+				if (!isight->first_packet)
+					isight_dropped_samples(isight, total);
+				isight->first_packet = false;
+				isight->total_samples = total;
+			}
+
+			isight_samples(isight, payload->samples, count);
+			isight->total_samples += count;
+		}
+	}
+
+	err = fw_iso_context_queue(isight->context, &audio_packet,
+				   &isight->buffer.iso_buffer,
+				   isight->buffer.packets[index].offset);
+	if (err < 0) {
+		dev_err(&isight->unit->device, "queueing error: %d\n", err);
+		isight_pcm_abort(isight);
+		isight->packet_index = -1;
+		return;
+	}
+	fw_iso_context_queue_flush(isight->context);
+
+	if (++index >= QUEUE_LENGTH)
+		index = 0;
+	isight->packet_index = index;
+}
+
+static int isight_connect(struct isight *isight)
+{
+	int ch, err;
+	__be32 value;
+
+retry_after_bus_reset:
+	ch = fw_iso_resources_allocate(&isight->resources,
+				       sizeof(struct audio_payload),
+				       isight->device->max_speed);
+	if (ch < 0) {
+		err = ch;
+		goto error;
+	}
+
+	value = cpu_to_be32(ch | (isight->device->max_speed << SPEED_SHIFT));
+	err = snd_fw_transaction(isight->unit, TCODE_WRITE_QUADLET_REQUEST,
+				 isight->audio_base + REG_ISO_TX_CONFIG,
+				 &value, 4, FW_FIXED_GENERATION |
+				 isight->resources.generation);
+	if (err == -EAGAIN) {
+		fw_iso_resources_free(&isight->resources);
+		goto retry_after_bus_reset;
+	} else if (err < 0) {
+		goto err_resources;
+	}
+
+	return 0;
+
+err_resources:
+	fw_iso_resources_free(&isight->resources);
+error:
+	return err;
+}
+
+static int isight_open(struct snd_pcm_substream *substream)
+{
+	static const struct snd_pcm_hardware hardware = {
+		.info = SNDRV_PCM_INFO_MMAP |
+			SNDRV_PCM_INFO_MMAP_VALID |
+			SNDRV_PCM_INFO_BATCH |
+			SNDRV_PCM_INFO_INTERLEAVED |
+			SNDRV_PCM_INFO_BLOCK_TRANSFER,
+		.formats = SNDRV_PCM_FMTBIT_S16_BE,
+		.rates = SNDRV_PCM_RATE_48000,
+		.rate_min = 48000,
+		.rate_max = 48000,
+		.channels_min = 2,
+		.channels_max = 2,
+		.buffer_bytes_max = 4 * 1024 * 1024,
+		.period_bytes_min = MAX_FRAMES_PER_PACKET * 4,
+		.period_bytes_max = 1024 * 1024,
+		.periods_min = 2,
+		.periods_max = UINT_MAX,
+	};
+	struct isight *isight = substream->private_data;
+
+	substream->runtime->hw = hardware;
+
+	return iso_packets_buffer_init(&isight->buffer, isight->unit,
+				       QUEUE_LENGTH,
+				       sizeof(struct audio_payload),
+				       DMA_FROM_DEVICE);
+}
+
+static int isight_close(struct snd_pcm_substream *substream)
+{
+	struct isight *isight = substream->private_data;
+
+	iso_packets_buffer_destroy(&isight->buffer, isight->unit);
+
+	return 0;
+}
+
+static int isight_hw_params(struct snd_pcm_substream *substream,
+			    struct snd_pcm_hw_params *hw_params)
+{
+	struct isight *isight = substream->private_data;
+
+	WRITE_ONCE(isight->pcm_active, true);
+
+	return 0;
+}
+
+static int reg_read(struct isight *isight, int offset, __be32 *value)
+{
+	return snd_fw_transaction(isight->unit, TCODE_READ_QUADLET_REQUEST,
+				  isight->audio_base + offset, value, 4, 0);
+}
+
+static int reg_write(struct isight *isight, int offset, __be32 value)
+{
+	return snd_fw_transaction(isight->unit, TCODE_WRITE_QUADLET_REQUEST,
+				  isight->audio_base + offset, &value, 4, 0);
+}
+
+static void isight_stop_streaming(struct isight *isight)
+{
+	__be32 value;
+
+	if (!isight->context)
+		return;
+
+	fw_iso_context_stop(isight->context);
+	fw_iso_context_destroy(isight->context);
+	isight->context = NULL;
+	fw_iso_resources_free(&isight->resources);
+	value = 0;
+	snd_fw_transaction(isight->unit, TCODE_WRITE_QUADLET_REQUEST,
+			   isight->audio_base + REG_AUDIO_ENABLE,
+			   &value, 4, FW_QUIET);
+}
+
+static int isight_hw_free(struct snd_pcm_substream *substream)
+{
+	struct isight *isight = substream->private_data;
+
+	WRITE_ONCE(isight->pcm_active, false);
+
+	guard(mutex)(&isight->mutex);
+	isight_stop_streaming(isight);
+
+	return 0;
+}
+
+static int isight_start_streaming(struct isight *isight)
+{
+	unsigned int i;
+	int err;
+
+	if (isight->context) {
+		if (isight->packet_index < 0)
+			isight_stop_streaming(isight);
+		else
+			return 0;
+	}
+
+	err = reg_write(isight, REG_SAMPLE_RATE, cpu_to_be32(RATE_48000));
+	if (err < 0)
+		goto error;
+
+	err = isight_connect(isight);
+	if (err < 0)
+		goto error;
+
+	err = reg_write(isight, REG_AUDIO_ENABLE, cpu_to_be32(AUDIO_ENABLE));
+	if (err < 0)
+		goto err_resources;
+
+	isight->context = fw_iso_context_create(isight->device->card,
+						FW_ISO_CONTEXT_RECEIVE,
+						isight->resources.channel,
+						isight->device->max_speed,
+						4, isight_packet, isight);
+	if (IS_ERR(isight->context)) {
+		err = PTR_ERR(isight->context);
+		isight->context = NULL;
+		goto err_resources;
+	}
+
+	for (i = 0; i < QUEUE_LENGTH; ++i) {
+		err = fw_iso_context_queue(isight->context, &audio_packet,
+					   &isight->buffer.iso_buffer,
+					   isight->buffer.packets[i].offset);
+		if (err < 0)
+			goto err_context;
+	}
+
+	isight->first_packet = true;
+	isight->packet_index = 0;
+
+	err = fw_iso_context_start(isight->context, -1, 0,
+				   FW_ISO_CONTEXT_MATCH_ALL_TAGS/*?*/);
+	if (err < 0)
+		goto err_context;
+
+	return 0;
+
+err_context:
+	fw_iso_context_destroy(isight->context);
+	isight->context = NULL;
+err_resources:
+	fw_iso_resources_free(&isight->resources);
+	reg_write(isight, REG_AUDIO_ENABLE, 0);
+error:
+	return err;
+}
+
+static int isight_prepare(struct snd_pcm_substream *substream)
+{
+	struct isight *isight = substream->private_data;
+
+	isight->buffer_pointer = 0;
+	isight->period_counter = 0;
+
+	guard(mutex)(&isight->mutex);
+	return isight_start_streaming(isight);
+}
+
+static int isight_trigger(struct snd_pcm_substream *substream, int cmd)
+{
+	struct isight *isight = substream->private_data;
+
+	switch (cmd) {
+	case SNDRV_PCM_TRIGGER_START:
+		WRITE_ONCE(isight->pcm_running, true);
+		break;
+	case SNDRV_PCM_TRIGGER_STOP:
+		WRITE_ONCE(isight->pcm_running, false);
+		break;
+	default:
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static snd_pcm_uframes_t isight_pointer(struct snd_pcm_substream *substream)
+{
+	struct isight *isight = substream->private_data;
+
+	return READ_ONCE(isight->buffer_pointer);
+}
+
+static int isight_create_pcm(struct isight *isight)
+{
+	static const struct snd_pcm_ops ops = {
+		.open      = isight_open,
+		.close     = isight_close,
+		.hw_params = isight_hw_params,
+		.hw_free   = isight_hw_free,
+		.prepare   = isight_prepare,
+		.trigger   = isight_trigger,
+		.pointer   = isight_pointer,
+	};
+	struct snd_pcm *pcm;
+	int err;
+
+	err = snd_pcm_new(isight->card, "iSight", 0, 0, 1, &pcm);
+	if (err < 0)
+		return err;
+	pcm->private_data = isight;
+	pcm->nonatomic = true;
+	strscpy(pcm->name, "iSight");
+	isight->pcm = pcm->streams[SNDRV_PCM_STREAM_CAPTURE].substream;
+	isight->pcm->ops = &ops;
+	snd_pcm_set_managed_buffer_all(pcm, SNDRV_DMA_TYPE_VMALLOC, NULL, 0, 0);
+
+	return 0;
+}
+
+static int isight_gain_info(struct snd_kcontrol *ctl,
+			    struct snd_ctl_elem_info *info)
+{
+	struct isight *isight = ctl->private_data;
+
+	info->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
+	info->count = 1;
+	info->value.integer.min = isight->gain_min;
+	info->value.integer.max = isight->gain_max;
+
+	return 0;
+}
+
+static int isight_gain_get(struct snd_kcontrol *ctl,
+			   struct snd_ctl_elem_value *value)
+{
+	struct isight *isight = ctl->private_data;
+	__be32 gain;
+	int err;
+
+	err = reg_read(isight, REG_GAIN, &gain);
+	if (err < 0)
+		return err;
+
+	value->value.integer.value[0] = (s32)be32_to_cpu(gain);
+
+	return 0;
+}
+
+static int isight_gain_put(struct snd_kcontrol *ctl,
+			   struct snd_ctl_elem_value *value)
+{
+	struct isight *isight = ctl->private_data;
+
+	if (value->value.integer.value[0] < isight->gain_min ||
+	    value->value.integer.value[0] > isight->gain_max)
+		return -EINVAL;
+
+	return reg_write(isight, REG_GAIN,
+			 cpu_to_be32(value->value.integer.value[0]));
+}
+
+static int isight_mute_get(struct snd_kcontrol *ctl,
+			   struct snd_ctl_elem_value *value)
+{
+	struct isight *isight = ctl->private_data;
+	__be32 mute;
+	int err;
+
+	err = reg_read(isight, REG_MUTE, &mute);
+	if (err < 0)
+		return err;
+
+	value->value.integer.value[0] = !mute;
+
+	return 0;
+}
+
+static int isight_mute_put(struct snd_kcontrol *ctl,
+			   struct snd_ctl_elem_value *value)
+{
+	struct isight *isight = ctl->private_data;
+
+	return reg_write(isight, REG_MUTE,
+			 (__force __be32)!value->value.integer.value[0]);
+}
+
+static int isight_create_mixer(struct isight *isight)
+{
+	static const struct snd_kcontrol_new gain_control = {
+		.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+		.name = "Mic Capture Volume",
+		.access = SNDRV_CTL_ELEM_ACCESS_READWRITE |
+			  SNDRV_CTL_ELEM_ACCESS_TLV_READ,
+		.info = isight_gain_info,
+		.get = isight_gain_get,
+		.put = isight_gain_put,
+	};
+	static const struct snd_kcontrol_new mute_control = {
+		.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+		.name = "Mic Capture Switch",
+		.info = snd_ctl_boolean_mono_info,
+		.get = isight_mute_get,
+		.put = isight_mute_put,
+	};
+	__be32 value;
+	struct snd_kcontrol *ctl;
+	int err;
+
+	err = reg_read(isight, REG_GAIN_RAW_START, &value);
+	if (err < 0)
+		return err;
+	isight->gain_min = be32_to_cpu(value);
+
+	err = reg_read(isight, REG_GAIN_RAW_END, &value);
+	if (err < 0)
+		return err;
+	isight->gain_max = be32_to_cpu(value);
+
+	isight->gain_tlv[SNDRV_CTL_TLVO_TYPE] = SNDRV_CTL_TLVT_DB_MINMAX;
+	isight->gain_tlv[SNDRV_CTL_TLVO_LEN] = 2 * sizeof(unsigned int);
+
+	err = reg_read(isight, REG_GAIN_DB_START, &value);
+	if (err < 0)
+		return err;
+	isight->gain_tlv[SNDRV_CTL_TLVO_DB_MINMAX_MIN] =
+						(s32)be32_to_cpu(value) * 100;
+
+	err = reg_read(isight, REG_GAIN_DB_END, &value);
+	if (err < 0)
+		return err;
+	isight->gain_tlv[SNDRV_CTL_TLVO_DB_MINMAX_MAX] =
+						(s32)be32_to_cpu(value) * 100;
+
+	ctl = snd_ctl_new1(&gain_control, isight);
+	if (ctl)
+		ctl->tlv.p = isight->gain_tlv;
+	err = snd_ctl_add(isight->card, ctl);
+	if (err < 0)
+		return err;
+
+	err = snd_ctl_add(isight->card, snd_ctl_new1(&mute_control, isight));
+	if (err < 0)
+		return err;
+
+	return 0;
+}
+
+static void isight_card_free(struct snd_card *card)
+{
+	struct isight *isight = card->private_data;
+
+	fw_iso_resources_destroy(&isight->resources);
+}
+
+static u64 get_unit_base(struct fw_unit *unit)
+{
+	struct fw_csr_iterator i;
+	int key, value;
+
+	fw_csr_iterator_init(&i, unit->directory);
+	while (fw_csr_iterator_next(&i, &key, &value))
+		if (key == CSR_OFFSET)
+			return CSR_REGISTER_BASE + value * 4;
+	return 0;
+}
+
+static int isight_probe(struct fw_unit *unit,
+			const struct ieee1394_device_id *id)
+{
+	struct fw_device *fw_dev = fw_parent_device(unit);
+	struct snd_card *card;
+	struct isight *isight;
+	int err;
+
+	err = snd_card_new(&unit->device, -1, NULL, THIS_MODULE,
+			   sizeof(*isight), &card);
+	if (err < 0)
+		return err;
+
+	isight = card->private_data;
+	isight->card = card;
+	mutex_init(&isight->mutex);
+	isight->unit = fw_unit_get(unit);
+	isight->device = fw_dev;
+	isight->audio_base = get_unit_base(unit);
+	if (!isight->audio_base) {
+		dev_err(&unit->device, "audio unit base not found\n");
+		err = -ENXIO;
+		goto error;
+	}
+	fw_iso_resources_init(&isight->resources, unit);
+
+	card->private_free = isight_card_free;
+
+	strscpy(card->driver, "iSight");
+	strscpy(card->shortname, "Apple iSight");
+	snprintf(card->longname, sizeof(card->longname),
+		 "Apple iSight (GUID %08x%08x) at %s, S%d",
+		 fw_dev->config_rom[3], fw_dev->config_rom[4],
+		 dev_name(&unit->device), 100 << fw_dev->max_speed);
+	strscpy(card->mixername, "iSight");
+
+	err = isight_create_pcm(isight);
+	if (err < 0)
+		goto error;
+
+	err = isight_create_mixer(isight);
+	if (err < 0)
+		goto error;
+
+	err = snd_card_register(card);
+	if (err < 0)
+		goto error;
+
+	dev_set_drvdata(&unit->device, isight);
+
+	return 0;
+error:
+	snd_card_free(card);
+
+	mutex_destroy(&isight->mutex);
+	fw_unit_put(isight->unit);
+
+	return err;
+}
+
+static void isight_bus_reset(struct fw_unit *unit)
+{
+	struct isight *isight = dev_get_drvdata(&unit->device);
+
+	if (fw_iso_resources_update(&isight->resources) < 0) {
+		isight_pcm_abort(isight);
+
+		guard(mutex)(&isight->mutex);
+		isight_stop_streaming(isight);
+	}
+}
+
+static void isight_remove(struct fw_unit *unit)
+{
+	struct isight *isight = dev_get_drvdata(&unit->device);
+
+	isight_pcm_abort(isight);
+
+	snd_card_disconnect(isight->card);
+
+	scoped_guard(mutex, &isight->mutex) {
+		isight_stop_streaming(isight);
+	}
+
+	// Block till all of ALSA character devices are released.
+	snd_card_free(isight->card);
+
+	mutex_destroy(&isight->mutex);
+	fw_unit_put(isight->unit);
+}
+
+static const struct ieee1394_device_id isight_id_table[] = {
+	{
+		.match_flags  = IEEE1394_MATCH_SPECIFIER_ID |
+				IEEE1394_MATCH_VERSION,
+		.specifier_id = OUI_APPLE,
+		.version      = SW_ISIGHT_AUDIO,
+	},
+	{ }
+};
+MODULE_DEVICE_TABLE(ieee1394, isight_id_table);
+
+static struct fw_driver isight_driver = {
+	.driver   = {
+		.owner	= THIS_MODULE,
+		.name	= KBUILD_MODNAME,
+		.bus	= &fw_bus_type,
+	},
+	.probe    = isight_probe,
+	.update   = isight_bus_reset,
+	.remove   = isight_remove,
+	.id_table = isight_id_table,
+};
+
+static int __init alsa_isight_init(void)
+{
+	return driver_register(&isight_driver.driver);
+}
+
+static void __exit alsa_isight_exit(void)
+{
+	driver_unregister(&isight_driver.driver);
+}
+
+module_init(alsa_isight_init);
+module_exit(alsa_isight_exit);