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, 373 insertions, 0 deletions

diff --git a/include/sound/pcm_params.h b/include/sound/pcm_params.h
new file mode 100644
index 000000000..fbf35df6e
--- /dev/null
+++ b/include/sound/pcm_params.h
@@ -0,0 +1,373 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef __SOUND_PCM_PARAMS_H
+#define __SOUND_PCM_PARAMS_H
+
+/*
+ *  PCM params helpers
+ *  Copyright (c) by Abramo Bagnara <abramo@alsa-project.org>
+ */
+
+#include <sound/pcm.h>
+
+int snd_pcm_hw_param_first(struct snd_pcm_substream *pcm, 
+			   struct snd_pcm_hw_params *params,
+			   snd_pcm_hw_param_t var, int *dir);
+int snd_pcm_hw_param_last(struct snd_pcm_substream *pcm, 
+			  struct snd_pcm_hw_params *params,
+			  snd_pcm_hw_param_t var, int *dir);
+int snd_pcm_hw_param_value(const struct snd_pcm_hw_params *params,
+			   snd_pcm_hw_param_t var, int *dir);
+
+#define SNDRV_MASK_BITS	64	/* we use so far 64bits only */
+#define SNDRV_MASK_SIZE	(SNDRV_MASK_BITS / 32)
+#define MASK_OFS(i)	((i) >> 5)
+#define MASK_BIT(i)	(1U << ((i) & 31))
+
+static inline void snd_mask_none(struct snd_mask *mask)
+{
+	memset(mask, 0, sizeof(*mask));
+}
+
+static inline void snd_mask_any(struct snd_mask *mask)
+{
+	memset(mask, 0xff, SNDRV_MASK_SIZE * sizeof(u_int32_t));
+}
+
+static inline int snd_mask_empty(const struct snd_mask *mask)
+{
+	int i;
+	for (i = 0; i < SNDRV_MASK_SIZE; i++)
+		if (mask->bits[i])
+			return 0;
+	return 1;
+}
+
+static inline unsigned int snd_mask_min(const struct snd_mask *mask)
+{
+	int i;
+	for (i = 0; i < SNDRV_MASK_SIZE; i++) {
+		if (mask->bits[i])
+			return __ffs(mask->bits[i]) + (i << 5);
+	}
+	return 0;
+}
+
+static inline unsigned int snd_mask_max(const struct snd_mask *mask)
+{
+	int i;
+	for (i = SNDRV_MASK_SIZE - 1; i >= 0; i--) {
+		if (mask->bits[i])
+			return __fls(mask->bits[i]) + (i << 5);
+	}
+	return 0;
+}
+
+static inline void snd_mask_set(struct snd_mask *mask, unsigned int val)
+{
+	mask->bits[MASK_OFS(val)] |= MASK_BIT(val);
+}
+
+/* Most of drivers need only this one */
+static inline void snd_mask_set_format(struct snd_mask *mask,
+				       snd_pcm_format_t format)
+{
+	snd_mask_set(mask, (__force unsigned int)format);
+}
+
+static inline void snd_mask_reset(struct snd_mask *mask, unsigned int val)
+{
+	mask->bits[MASK_OFS(val)] &= ~MASK_BIT(val);
+}
+
+static inline void snd_mask_set_range(struct snd_mask *mask,
+				      unsigned int from, unsigned int to)
+{
+	unsigned int i;
+	for (i = from; i <= to; i++)
+		mask->bits[MASK_OFS(i)] |= MASK_BIT(i);
+}
+
+static inline void snd_mask_reset_range(struct snd_mask *mask,
+					unsigned int from, unsigned int to)
+{
+	unsigned int i;
+	for (i = from; i <= to; i++)
+		mask->bits[MASK_OFS(i)] &= ~MASK_BIT(i);
+}
+
+static inline void snd_mask_leave(struct snd_mask *mask, unsigned int val)
+{
+	unsigned int v;
+	v = mask->bits[MASK_OFS(val)] & MASK_BIT(val);
+	snd_mask_none(mask);
+	mask->bits[MASK_OFS(val)] = v;
+}
+
+static inline void snd_mask_intersect(struct snd_mask *mask,
+				      const struct snd_mask *v)
+{
+	int i;
+	for (i = 0; i < SNDRV_MASK_SIZE; i++)
+		mask->bits[i] &= v->bits[i];
+}
+
+static inline int snd_mask_eq(const struct snd_mask *mask,
+			      const struct snd_mask *v)
+{
+	return ! memcmp(mask, v, SNDRV_MASK_SIZE * sizeof(u_int32_t));
+}
+
+static inline void snd_mask_copy(struct snd_mask *mask,
+				 const struct snd_mask *v)
+{
+	*mask = *v;
+}
+
+static inline int snd_mask_test(const struct snd_mask *mask, unsigned int val)
+{
+	return mask->bits[MASK_OFS(val)] & MASK_BIT(val);
+}
+
+/* Most of drivers need only this one */
+static inline int snd_mask_test_format(const struct snd_mask *mask,
+				       snd_pcm_format_t format)
+{
+	return snd_mask_test(mask, (__force unsigned int)format);
+}
+
+static inline int snd_mask_single(const struct snd_mask *mask)
+{
+	int i, c = 0;
+	for (i = 0; i < SNDRV_MASK_SIZE; i++) {
+		if (! mask->bits[i])
+			continue;
+		if (mask->bits[i] & (mask->bits[i] - 1))
+			return 0;
+		if (c)
+			return 0;
+		c++;
+	}
+	return 1;
+}
+
+static inline int snd_mask_refine(struct snd_mask *mask,
+				  const struct snd_mask *v)
+{
+	struct snd_mask old;
+	snd_mask_copy(&old, mask);
+	snd_mask_intersect(mask, v);
+	if (snd_mask_empty(mask))
+		return -EINVAL;
+	return !snd_mask_eq(mask, &old);
+}
+
+static inline int snd_mask_refine_first(struct snd_mask *mask)
+{
+	if (snd_mask_single(mask))
+		return 0;
+	snd_mask_leave(mask, snd_mask_min(mask));
+	return 1;
+}
+
+static inline int snd_mask_refine_last(struct snd_mask *mask)
+{
+	if (snd_mask_single(mask))
+		return 0;
+	snd_mask_leave(mask, snd_mask_max(mask));
+	return 1;
+}
+
+static inline int snd_mask_refine_min(struct snd_mask *mask, unsigned int val)
+{
+	if (snd_mask_min(mask) >= val)
+		return 0;
+	snd_mask_reset_range(mask, 0, val - 1);
+	if (snd_mask_empty(mask))
+		return -EINVAL;
+	return 1;
+}
+
+static inline int snd_mask_refine_max(struct snd_mask *mask, unsigned int val)
+{
+	if (snd_mask_max(mask) <= val)
+		return 0;
+	snd_mask_reset_range(mask, val + 1, SNDRV_MASK_BITS);
+	if (snd_mask_empty(mask))
+		return -EINVAL;
+	return 1;
+}
+
+static inline int snd_mask_refine_set(struct snd_mask *mask, unsigned int val)
+{
+	int changed;
+	changed = !snd_mask_single(mask);
+	snd_mask_leave(mask, val);
+	if (snd_mask_empty(mask))
+		return -EINVAL;
+	return changed;
+}
+
+static inline int snd_mask_value(const struct snd_mask *mask)
+{
+	return snd_mask_min(mask);
+}
+
+static inline void snd_interval_any(struct snd_interval *i)
+{
+	i->min = 0;
+	i->openmin = 0;
+	i->max = UINT_MAX;
+	i->openmax = 0;
+	i->integer = 0;
+	i->empty = 0;
+}
+
+static inline void snd_interval_none(struct snd_interval *i)
+{
+	i->empty = 1;
+}
+
+static inline int snd_interval_checkempty(const struct snd_interval *i)
+{
+	return (i->min > i->max ||
+		(i->min == i->max && (i->openmin || i->openmax)));
+}
+
+static inline int snd_interval_empty(const struct snd_interval *i)
+{
+	return i->empty;
+}
+
+static inline int snd_interval_single(const struct snd_interval *i)
+{
+	return (i->min == i->max || 
+		(i->min + 1 == i->max && (i->openmin || i->openmax)));
+}
+
+static inline int snd_interval_value(const struct snd_interval *i)
+{
+	if (i->openmin && !i->openmax)
+		return i->max;
+	return i->min;
+}
+
+static inline int snd_interval_min(const struct snd_interval *i)
+{
+	return i->min;
+}
+
+static inline int snd_interval_max(const struct snd_interval *i)
+{
+	unsigned int v;
+	v = i->max;
+	if (i->openmax)
+		v--;
+	return v;
+}
+
+static inline int snd_interval_test(const struct snd_interval *i, unsigned int val)
+{
+	return !((i->min > val || (i->min == val && i->openmin) ||
+		  i->max < val || (i->max == val && i->openmax)));
+}
+
+static inline void snd_interval_copy(struct snd_interval *d, const struct snd_interval *s)
+{
+	*d = *s;
+}
+
+static inline int snd_interval_setinteger(struct snd_interval *i)
+{
+	if (i->integer)
+		return 0;
+	if (i->openmin && i->openmax && i->min == i->max)
+		return -EINVAL;
+	i->integer = 1;
+	return 1;
+}
+
+static inline int snd_interval_eq(const struct snd_interval *i1, const struct snd_interval *i2)
+{
+	if (i1->empty)
+		return i2->empty;
+	if (i2->empty)
+		return i1->empty;
+	return i1->min == i2->min && i1->openmin == i2->openmin &&
+		i1->max == i2->max && i1->openmax == i2->openmax;
+}
+
+/**
+ * params_access - get the access type from the hw params
+ * @p: hw params
+ */
+static inline snd_pcm_access_t params_access(const struct snd_pcm_hw_params *p)
+{
+	return (__force snd_pcm_access_t)snd_mask_min(hw_param_mask_c(p,
+		SNDRV_PCM_HW_PARAM_ACCESS));
+}
+
+/**
+ * params_format - get the sample format from the hw params
+ * @p: hw params
+ */
+static inline snd_pcm_format_t params_format(const struct snd_pcm_hw_params *p)
+{
+	return (__force snd_pcm_format_t)snd_mask_min(hw_param_mask_c(p,
+		SNDRV_PCM_HW_PARAM_FORMAT));
+}
+
+/**
+ * params_subformat - get the sample subformat from the hw params
+ * @p: hw params
+ */
+static inline snd_pcm_subformat_t
+params_subformat(const struct snd_pcm_hw_params *p)
+{
+	return (__force snd_pcm_subformat_t)snd_mask_min(hw_param_mask_c(p,
+		SNDRV_PCM_HW_PARAM_SUBFORMAT));
+}
+
+/**
+ * params_period_bytes - get the period size (in bytes) from the hw params
+ * @p: hw params
+ */
+static inline unsigned int
+params_period_bytes(const struct snd_pcm_hw_params *p)
+{
+	return hw_param_interval_c(p, SNDRV_PCM_HW_PARAM_PERIOD_BYTES)->min;
+}
+
+/**
+ * params_width - get the number of bits of the sample format from the hw params
+ * @p: hw params
+ *
+ * This function returns the number of bits per sample that the selected sample
+ * format of the hw params has.
+ */
+static inline int params_width(const struct snd_pcm_hw_params *p)
+{
+	return snd_pcm_format_width(params_format(p));
+}
+
+/*
+ * params_physical_width - get the storage size of the sample format from the hw params
+ * @p: hw params
+ *
+ * This functions returns the number of bits per sample that the selected sample
+ * format of the hw params takes up in memory. This will be equal or larger than
+ * params_width().
+ */
+static inline int params_physical_width(const struct snd_pcm_hw_params *p)
+{
+	return snd_pcm_format_physical_width(params_format(p));
+}
+
+int snd_pcm_hw_params_bits(const struct snd_pcm_hw_params *p);
+
+static inline void
+params_set_format(struct snd_pcm_hw_params *p, snd_pcm_format_t fmt)
+{
+	snd_mask_set_format(hw_param_mask(p, SNDRV_PCM_HW_PARAM_FORMAT), fmt);
+}
+
+#endif /* __SOUND_PCM_PARAMS_H */