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, 104 insertions, 0 deletions

diff --git a/sound/soc/sof/sof-of-dev.c b/sound/soc/sof/sof-of-dev.c
new file mode 100644
index 000000000..3ccfcfb14
--- /dev/null
+++ b/sound/soc/sof/sof-of-dev.c
@@ -0,0 +1,104 @@
+// SPDX-License-Identifier: (GPL-2.0-only OR BSD-3-Clause)
+//
+// Copyright 2019 NXP
+//
+// Author: Daniel Baluta <daniel.baluta@nxp.com>
+//
+
+#include <linux/firmware.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/pm_runtime.h>
+#include <sound/sof.h>
+
+#include "sof-of-dev.h"
+#include "ops.h"
+
+static char *fw_path;
+module_param(fw_path, charp, 0444);
+MODULE_PARM_DESC(fw_path, "deprecated - moved to snd-sof module.");
+
+static char *fw_filename;
+module_param(fw_filename, charp, 0444);
+MODULE_PARM_DESC(fw_filename, "deprecated - moved to snd-sof module.");
+
+static char *tplg_path;
+module_param(tplg_path, charp, 0444);
+MODULE_PARM_DESC(tplg_path, "deprecated - moved to snd-sof module.");
+
+static char *tplg_filename;
+module_param(tplg_filename, charp, 0444);
+MODULE_PARM_DESC(tplg_filename, "deprecated - moved to snd-sof module.");
+
+EXPORT_DEV_PM_OPS(sof_of_pm) = {
+	.prepare = snd_sof_prepare,
+	.complete = snd_sof_complete,
+	SYSTEM_SLEEP_PM_OPS(snd_sof_suspend, snd_sof_resume)
+	RUNTIME_PM_OPS(snd_sof_runtime_suspend, snd_sof_runtime_resume, NULL)
+};
+
+static void sof_of_probe_complete(struct device *dev)
+{
+	/* allow runtime_pm */
+	pm_runtime_set_autosuspend_delay(dev, SND_SOF_SUSPEND_DELAY_MS);
+	pm_runtime_use_autosuspend(dev);
+	pm_runtime_mark_last_busy(dev);
+	pm_runtime_set_active(dev);
+	pm_runtime_enable(dev);
+}
+
+int sof_of_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	const struct sof_dev_desc *desc;
+	struct snd_sof_pdata *sof_pdata;
+
+	dev_info(&pdev->dev, "DT DSP detected");
+
+	sof_pdata = devm_kzalloc(dev, sizeof(*sof_pdata), GFP_KERNEL);
+	if (!sof_pdata)
+		return -ENOMEM;
+
+	desc = device_get_match_data(dev);
+	if (!desc)
+		return -ENODEV;
+
+	if (!desc->ops) {
+		dev_err(dev, "error: no matching DT descriptor ops\n");
+		return -ENODEV;
+	}
+
+	sof_pdata->desc = desc;
+	sof_pdata->dev = &pdev->dev;
+
+	sof_pdata->ipc_file_profile_base.ipc_type = desc->ipc_default;
+	sof_pdata->ipc_file_profile_base.fw_path = fw_path;
+	sof_pdata->ipc_file_profile_base.tplg_path = tplg_path;
+	sof_pdata->ipc_file_profile_base.fw_name = fw_filename;
+	sof_pdata->ipc_file_profile_base.tplg_name = tplg_filename;
+
+	/* set callback to be called on successful device probe to enable runtime_pm */
+	sof_pdata->sof_probe_complete = sof_of_probe_complete;
+
+	/* call sof helper for DSP hardware probe */
+	return snd_sof_device_probe(dev, sof_pdata);
+}
+EXPORT_SYMBOL(sof_of_probe);
+
+void sof_of_remove(struct platform_device *pdev)
+{
+	pm_runtime_disable(&pdev->dev);
+
+	/* call sof helper for DSP hardware remove */
+	snd_sof_device_remove(&pdev->dev);
+}
+EXPORT_SYMBOL(sof_of_remove);
+
+void sof_of_shutdown(struct platform_device *pdev)
+{
+	snd_sof_device_shutdown(&pdev->dev);
+}
+EXPORT_SYMBOL(sof_of_shutdown);
+
+MODULE_LICENSE("Dual BSD/GPL");
+MODULE_DESCRIPTION("SOF support for OF/DT platforms");