kbuild: rust: keep Rust objects out of Clang LTO with inline helpersgrafted

Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit
`objtool` errors such as:

    vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a:
    can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd

The reason is that in such builds, the Clang invocation that compiles
the combined Rust plus helpers bitcode emits LLVM bitcode (again) --
the final code generation happens in the linker's LTO step, which the
`-mllvm` trap options passed to Clang do not reach.

This, in turn, means that unreachable traps are missing, and the
impossible paths do not merely fallthrough to the next symbol, but past
the end of their own section, since LTO builds place each function in
its own section.

Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always
emits machine code directly, with the traps in place.

Assisted-by: LLM
Cc: Gary Guo <gary@garyguo.net>
Cc: Boqun Feng <boqun@kernel.org>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Matthew Maurer <mmaurer@google.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust")
Acked-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 325 insertions, 0 deletions

diff --git a/sound/hda/controllers/acpi.c b/sound/hda/controllers/acpi.c
new file mode 100644
index 000000000..505cc97e0
--- /dev/null
+++ b/sound/hda/controllers/acpi.c
@@ -0,0 +1,325 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * ALSA driver for ACPI-based HDA Controllers.
+ */
+
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/acpi.h>
+
+#include <sound/hda_codec.h>
+
+#include "hda_controller.h"
+
+struct hda_acpi {
+	struct azx azx;
+	struct snd_card *card;
+	struct platform_device *pdev;
+	void __iomem *regs;
+	struct work_struct probe_work;
+	const struct hda_data *data;
+};
+
+/**
+ * struct hda_data - Optional device-specific data
+ * @short_name: Used for the ALSA card name; defaults to KBUILD_MODNAME
+ * @long_name:  Used for longer description; defaults to short_name
+ * @flags:      Passed to &azx->driver_caps
+ *
+ * A pointer to a record of this type may be stored in the
+ * &acpi_device_id->driver_data field of an ACPI match table entry in order to
+ * customize the naming and behavior of a particular device. All fields are
+ * optional and sensible defaults will be selected in their absence.
+ */
+struct hda_data {
+	const char *short_name;
+	const char *long_name;
+	unsigned long flags;
+};
+
+static int hda_acpi_dev_disconnect(struct snd_device *device)
+{
+	struct azx *chip = device->device_data;
+
+	chip->bus.shutdown = 1;
+	return 0;
+}
+
+static int hda_acpi_dev_free(struct snd_device *device)
+{
+	struct azx *azx = device->device_data;
+	struct hda_acpi *hda = container_of(azx, struct hda_acpi, azx);
+
+	cancel_work_sync(&hda->probe_work);
+	if (azx_bus(azx)->chip_init) {
+		azx_stop_all_streams(azx);
+		azx_stop_chip(azx);
+	}
+
+	azx_free_stream_pages(azx);
+	azx_free_streams(azx);
+	snd_hdac_bus_exit(azx_bus(azx));
+
+	return 0;
+}
+
+static int hda_acpi_init(struct hda_acpi *hda)
+{
+	struct hdac_bus *bus = azx_bus(&hda->azx);
+	struct snd_card *card = hda->azx.card;
+	struct device *dev = &hda->pdev->dev;
+	struct azx *azx = &hda->azx;
+	struct resource *res;
+	unsigned short gcap;
+	const char *sname, *lname;
+	int err, irq;
+
+	/* The base address for the HDA registers and the interrupt are wrapped
+	 * in an ACPI _CRS object which can be parsed by platform_get_irq() and
+	 * devm_platform_get_and_ioremap_resource()
+	 */
+
+	irq = platform_get_irq(hda->pdev, 0);
+	if (irq < 0)
+		return irq;
+
+	hda->regs = devm_platform_get_and_ioremap_resource(hda->pdev, 0, &res);
+	if (IS_ERR(hda->regs))
+		return PTR_ERR(hda->regs);
+
+	bus->remap_addr = hda->regs;
+	bus->addr = res->start;
+
+	err = devm_request_irq(dev, irq, azx_interrupt,
+			       IRQF_SHARED, KBUILD_MODNAME, azx);
+	if (err) {
+		dev_err(dev, "unable to request IRQ %d, disabling device\n",
+			irq);
+		return err;
+	}
+	bus->irq = irq;
+	bus->dma_stop_delay = 100;
+	card->sync_irq = bus->irq;
+
+	gcap = azx_readw(azx, GCAP);
+	dev_dbg(dev, "chipset global capabilities = 0x%x\n", gcap);
+
+	azx->align_buffer_size = 1;
+
+	azx->capture_streams = (gcap >> 8) & 0x0f;
+	azx->playback_streams = (gcap >> 12) & 0x0f;
+
+	azx->capture_index_offset = 0;
+	azx->playback_index_offset = azx->capture_streams;
+	azx->num_streams = azx->playback_streams + azx->capture_streams;
+
+	err = azx_init_streams(azx);
+	if (err < 0) {
+		dev_err(dev, "failed to initialize streams: %d\n", err);
+		return err;
+	}
+
+	err = azx_alloc_stream_pages(azx);
+	if (err < 0) {
+		dev_err(dev, "failed to allocate stream pages: %d\n", err);
+		return err;
+	}
+
+	azx_init_chip(azx, 1);
+
+	if (!bus->codec_mask) {
+		dev_err(dev, "no codecs found!\n");
+		return -ENODEV;
+	}
+
+	strscpy(card->driver, "hda-acpi");
+
+	sname = hda->data->short_name ? hda->data->short_name : KBUILD_MODNAME;
+
+	if (strlen(sname) > sizeof(card->shortname))
+		dev_info(dev, "truncating shortname for card %s\n", sname);
+	strscpy(card->shortname, sname);
+
+	lname = hda->data->long_name ? hda->data->long_name : sname;
+
+	snprintf(card->longname, sizeof(card->longname),
+		 "%s at 0x%lx irq %i", lname, bus->addr, bus->irq);
+
+	return 0;
+}
+
+static void hda_acpi_probe_work(struct work_struct *work)
+{
+	struct hda_acpi *hda = container_of(work, struct hda_acpi, probe_work);
+	struct azx *chip = &hda->azx;
+	int err;
+
+	err = hda_acpi_init(hda);
+	if (err < 0)
+		return;
+
+	err = azx_probe_codecs(chip, 8);
+	if (err < 0)
+		return;
+
+	err = azx_codec_configure(chip);
+	if (err < 0)
+		return;
+
+	err = snd_card_register(chip->card);
+	if (err < 0)
+		return;
+
+	chip->running = 1;
+}
+
+static int hda_acpi_create(struct hda_acpi *hda)
+{
+	static const struct snd_device_ops ops = {
+		.dev_disconnect = hda_acpi_dev_disconnect,
+		.dev_free = hda_acpi_dev_free,
+	};
+	static const struct hda_controller_ops null_ops;
+	struct azx *azx = &hda->azx;
+	int err;
+
+	mutex_init(&azx->open_mutex);
+	azx->card = hda->card;
+	INIT_LIST_HEAD(&azx->pcm_list);
+
+	azx->ops = &null_ops;
+	azx->driver_caps = hda->data->flags;
+	azx->driver_type = hda->data->flags & 0xff;
+	azx->codec_probe_mask = -1;
+
+	err = azx_bus_init(azx, NULL);
+	if (err < 0)
+		return err;
+
+	err = snd_device_new(hda->card, SNDRV_DEV_LOWLEVEL, &hda->azx, &ops);
+	if (err < 0) {
+		dev_err(&hda->pdev->dev, "Error creating device\n");
+		return err;
+	}
+
+	return 0;
+}
+
+static int hda_acpi_probe(struct platform_device *pdev)
+{
+	struct hda_acpi *hda;
+	int err;
+
+	hda = devm_kzalloc(&pdev->dev, sizeof(*hda), GFP_KERNEL);
+	if (!hda)
+		return -ENOMEM;
+
+	hda->pdev = pdev;
+	hda->data = acpi_device_get_match_data(&pdev->dev);
+
+	/* Fall back to defaults if the table didn't have a *struct hda_data */
+	if (!hda->data)
+		hda->data = devm_kzalloc(&pdev->dev, sizeof(*hda->data),
+					 GFP_KERNEL);
+	if (!hda->data)
+		return -ENOMEM;
+
+	err = snd_card_new(&pdev->dev, SNDRV_DEFAULT_IDX1, SNDRV_DEFAULT_STR1,
+			   THIS_MODULE, 0, &hda->card);
+	if (err < 0) {
+		dev_err(&pdev->dev, "Error creating card!\n");
+		return err;
+	}
+
+	INIT_WORK(&hda->probe_work, hda_acpi_probe_work);
+
+	err = hda_acpi_create(hda);
+	if (err < 0)
+		goto out_free;
+	hda->card->private_data = &hda->azx;
+
+	dev_set_drvdata(&pdev->dev, hda->card);
+
+	schedule_work(&hda->probe_work);
+
+	return 0;
+
+out_free:
+	snd_card_free(hda->card);
+	return err;
+}
+
+static void hda_acpi_remove(struct platform_device *pdev)
+{
+	snd_card_free(dev_get_drvdata(&pdev->dev));
+}
+
+static void hda_acpi_shutdown(struct platform_device *pdev)
+{
+	struct snd_card *card = dev_get_drvdata(&pdev->dev);
+	struct azx *chip;
+
+	if (!card)
+		return;
+	chip = card->private_data;
+	if (chip && chip->running)
+		azx_stop_chip(chip);
+}
+
+static int hda_acpi_suspend(struct device *dev)
+{
+	struct snd_card *card = dev_get_drvdata(dev);
+	int rc;
+
+	rc = pm_runtime_force_suspend(dev);
+	if (rc < 0)
+		return rc;
+	snd_power_change_state(card, SNDRV_CTL_POWER_D3hot);
+
+	return 0;
+}
+
+static int hda_acpi_resume(struct device *dev)
+{
+	struct snd_card *card = dev_get_drvdata(dev);
+	int rc;
+
+	rc = pm_runtime_force_resume(dev);
+	if (rc < 0)
+		return rc;
+	snd_power_change_state(card, SNDRV_CTL_POWER_D0);
+
+	return 0;
+}
+
+static const struct dev_pm_ops hda_acpi_pm = {
+	SYSTEM_SLEEP_PM_OPS(hda_acpi_suspend, hda_acpi_resume)
+};
+
+static const struct hda_data nvidia_hda_data = {
+	.short_name = "NVIDIA",
+	.long_name = "NVIDIA HDA Controller",
+	.flags = AZX_DCAPS_CORBRP_SELF_CLEAR,
+};
+
+static const struct acpi_device_id hda_acpi_match[] = {
+	{ .id = "NVDA2014", .driver_data = (uintptr_t) &nvidia_hda_data },
+	{ .id = "NVDA2015", .driver_data = (uintptr_t) &nvidia_hda_data },
+	{},
+};
+MODULE_DEVICE_TABLE(acpi, hda_acpi_match);
+
+static struct platform_driver hda_acpi_platform_driver = {
+	.driver = {
+		.name = KBUILD_MODNAME,
+		.pm = &hda_acpi_pm,
+		.acpi_match_table = hda_acpi_match,
+	},
+	.probe = hda_acpi_probe,
+	.remove = hda_acpi_remove,
+	.shutdown = hda_acpi_shutdown,
+};
+module_platform_driver(hda_acpi_platform_driver);
+
+MODULE_DESCRIPTION("Driver for ACPI-based HDA Controllers");
+MODULE_LICENSE("GPL");