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, 216 insertions, 0 deletions

diff --git a/sound/soc/codecs/dmic.c b/sound/soc/codecs/dmic.c
new file mode 100644
index 000000000..61e1bf1b3
--- /dev/null
+++ b/sound/soc/codecs/dmic.c
@@ -0,0 +1,216 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * dmic.c  --  SoC audio for Generic Digital MICs
+ *
+ * Author: Liam Girdwood <lrg@slimlogic.co.uk>
+ */
+
+#include <linux/delay.h>
+#include <linux/gpio.h>
+#include <linux/gpio/consumer.h>
+#include <linux/platform_device.h>
+#include <linux/regulator/consumer.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <sound/core.h>
+#include <sound/pcm.h>
+#include <sound/soc.h>
+#include <sound/soc-dapm.h>
+
+#define MAX_MODESWITCH_DELAY 70
+static int modeswitch_delay;
+module_param(modeswitch_delay, uint, 0644);
+
+static int wakeup_delay;
+module_param(wakeup_delay, uint, 0644);
+
+struct dmic {
+	struct gpio_desc *gpio_en;
+	struct regulator *vref;
+	int wakeup_delay;
+	/* Delay after DMIC mode switch */
+	int modeswitch_delay;
+};
+
+static int dmic_daiops_trigger(struct snd_pcm_substream *substream,
+			       int cmd, struct snd_soc_dai *dai)
+{
+	struct snd_soc_component *component = dai->component;
+	struct dmic *dmic = snd_soc_component_get_drvdata(component);
+
+	switch (cmd) {
+	case SNDRV_PCM_TRIGGER_STOP:
+		if (dmic->modeswitch_delay)
+			mdelay(dmic->modeswitch_delay);
+
+		break;
+	}
+
+	return 0;
+}
+
+static const struct snd_soc_dai_ops dmic_dai_ops = {
+	.trigger	= dmic_daiops_trigger,
+};
+
+static int dmic_aif_event(struct snd_soc_dapm_widget *w,
+			  struct snd_kcontrol *kcontrol, int event) {
+	struct snd_soc_component *component = snd_soc_dapm_to_component(w->dapm);
+	struct dmic *dmic = snd_soc_component_get_drvdata(component);
+	int ret = 0;
+
+	switch (event) {
+	case SND_SOC_DAPM_POST_PMU:
+		if (dmic->gpio_en)
+			gpiod_set_value_cansleep(dmic->gpio_en, 1);
+
+		if (dmic->vref) {
+			ret = regulator_enable(dmic->vref);
+			if (ret)
+				return ret;
+		}
+
+		if (dmic->wakeup_delay)
+			msleep(dmic->wakeup_delay);
+		break;
+	case SND_SOC_DAPM_POST_PMD:
+		if (dmic->gpio_en)
+			gpiod_set_value_cansleep(dmic->gpio_en, 0);
+
+		if (dmic->vref)
+			ret = regulator_disable(dmic->vref);
+
+		break;
+	}
+
+	return ret;
+}
+
+static struct snd_soc_dai_driver dmic_dai = {
+	.name = "dmic-hifi",
+	.capture = {
+		.stream_name = "Capture",
+		.channels_min = 1,
+		.channels_max = 8,
+		.rates = SNDRV_PCM_RATE_CONTINUOUS,
+		.formats = SNDRV_PCM_FMTBIT_S32_LE
+			| SNDRV_PCM_FMTBIT_S24_LE
+			| SNDRV_PCM_FMTBIT_S16_LE
+			| SNDRV_PCM_FMTBIT_DSD_U8
+			| SNDRV_PCM_FMTBIT_DSD_U16_LE
+			| SNDRV_PCM_FMTBIT_DSD_U32_LE
+			| SNDRV_PCM_FMTBIT_DSD_U16_BE
+			| SNDRV_PCM_FMTBIT_DSD_U32_BE,
+	},
+	.ops    = &dmic_dai_ops,
+};
+
+static int dmic_component_probe(struct snd_soc_component *component)
+{
+	struct dmic *dmic;
+
+	dmic = devm_kzalloc(component->dev, sizeof(*dmic), GFP_KERNEL);
+	if (!dmic)
+		return -ENOMEM;
+
+	dmic->vref = devm_regulator_get_optional(component->dev, "vref");
+	if (IS_ERR(dmic->vref)) {
+		if (PTR_ERR(dmic->vref) != -ENODEV)
+			return dev_err_probe(component->dev, PTR_ERR(dmic->vref),
+					     "Failed to get vref\n");
+		dmic->vref = NULL;
+	}
+
+	dmic->gpio_en = devm_gpiod_get_optional(component->dev,
+						"dmicen", GPIOD_OUT_LOW);
+	if (IS_ERR(dmic->gpio_en))
+		return PTR_ERR(dmic->gpio_en);
+
+	device_property_read_u32(component->dev, "wakeup-delay-ms",
+				 &dmic->wakeup_delay);
+	device_property_read_u32(component->dev, "modeswitch-delay-ms",
+				 &dmic->modeswitch_delay);
+	if (wakeup_delay)
+		dmic->wakeup_delay  = wakeup_delay;
+	if (modeswitch_delay)
+		dmic->modeswitch_delay  = modeswitch_delay;
+
+	if (dmic->modeswitch_delay > MAX_MODESWITCH_DELAY)
+		dmic->modeswitch_delay = MAX_MODESWITCH_DELAY;
+
+	snd_soc_component_set_drvdata(component, dmic);
+
+	return 0;
+}
+
+static const struct snd_soc_dapm_widget dmic_dapm_widgets[] = {
+	SND_SOC_DAPM_AIF_OUT_E("DMIC AIF", "Capture", 0,
+			       SND_SOC_NOPM, 0, 0, dmic_aif_event,
+			       SND_SOC_DAPM_POST_PMU | SND_SOC_DAPM_POST_PMD),
+	SND_SOC_DAPM_INPUT("DMic"),
+};
+
+static const struct snd_soc_dapm_route intercon[] = {
+	{"DMIC AIF", NULL, "DMic"},
+};
+
+static const struct snd_soc_component_driver soc_dmic = {
+	.probe			= dmic_component_probe,
+	.dapm_widgets		= dmic_dapm_widgets,
+	.num_dapm_widgets	= ARRAY_SIZE(dmic_dapm_widgets),
+	.dapm_routes		= intercon,
+	.num_dapm_routes	= ARRAY_SIZE(intercon),
+	.idle_bias_on		= 1,
+	.use_pmdown_time	= 1,
+	.endianness		= 1,
+};
+
+static int dmic_dev_probe(struct platform_device *pdev)
+{
+	int err;
+	u32 chans;
+	struct snd_soc_dai_driver *dai_drv = &dmic_dai;
+
+	if (pdev->dev.of_node) {
+		err = of_property_read_u32(pdev->dev.of_node, "num-channels", &chans);
+		if (err && (err != -EINVAL))
+			return err;
+
+		if (!err) {
+			if (chans < 1 || chans > 8)
+				return -EINVAL;
+
+			dai_drv = devm_kzalloc(&pdev->dev, sizeof(*dai_drv), GFP_KERNEL);
+			if (!dai_drv)
+				return -ENOMEM;
+
+			memcpy(dai_drv, &dmic_dai, sizeof(*dai_drv));
+			dai_drv->capture.channels_max = chans;
+		}
+	}
+
+	return devm_snd_soc_register_component(&pdev->dev,
+			&soc_dmic, dai_drv, 1);
+}
+
+MODULE_ALIAS("platform:dmic-codec");
+
+static const struct of_device_id dmic_dev_match[] = {
+	{.compatible = "dmic-codec"},
+	{}
+};
+MODULE_DEVICE_TABLE(of, dmic_dev_match);
+
+static struct platform_driver dmic_driver = {
+	.driver = {
+		.name = "dmic-codec",
+		.of_match_table = dmic_dev_match,
+	},
+	.probe = dmic_dev_probe,
+};
+
+module_platform_driver(dmic_driver);
+
+MODULE_DESCRIPTION("Generic DMIC driver");
+MODULE_AUTHOR("Liam Girdwood <lrg@slimlogic.co.uk>");
+MODULE_LICENSE("GPL");