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, 236 insertions, 0 deletions

diff --git a/drivers/firewire/packet-header-definitions.h b/drivers/firewire/packet-header-definitions.h
new file mode 100644
index 000000000..87a5a3184
--- /dev/null
+++ b/drivers/firewire/packet-header-definitions.h
@@ -0,0 +1,236 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+//
+// packet-header-definitions.h - The definitions of header fields for IEEE 1394 packet.
+//
+// Copyright (c) 2024 Takashi Sakamoto
+
+#ifndef _FIREWIRE_PACKET_HEADER_DEFINITIONS_H
+#define _FIREWIRE_PACKET_HEADER_DEFINITIONS_H
+
+#include <linux/types.h>
+
+#define ASYNC_HEADER_QUADLET_COUNT		4
+
+#define ASYNC_HEADER_Q0_DESTINATION_SHIFT	16
+#define ASYNC_HEADER_Q0_DESTINATION_MASK	0xffff0000
+#define ASYNC_HEADER_Q0_TLABEL_SHIFT		10
+#define ASYNC_HEADER_Q0_TLABEL_MASK		0x0000fc00
+#define ASYNC_HEADER_Q0_RETRY_SHIFT		8
+#define ASYNC_HEADER_Q0_RETRY_MASK		0x00000300
+#define ASYNC_HEADER_Q0_TCODE_SHIFT		4
+#define ASYNC_HEADER_Q0_TCODE_MASK		0x000000f0
+#define ASYNC_HEADER_Q0_PRIORITY_SHIFT		0
+#define ASYNC_HEADER_Q0_PRIORITY_MASK		0x0000000f
+#define ASYNC_HEADER_Q1_SOURCE_SHIFT		16
+#define ASYNC_HEADER_Q1_SOURCE_MASK		0xffff0000
+#define ASYNC_HEADER_Q1_RCODE_SHIFT		12
+#define ASYNC_HEADER_Q1_RCODE_MASK		0x0000f000
+#define ASYNC_HEADER_Q1_RCODE_SHIFT		12
+#define ASYNC_HEADER_Q1_RCODE_MASK		0x0000f000
+#define ASYNC_HEADER_Q1_OFFSET_HIGH_SHIFT	0
+#define ASYNC_HEADER_Q1_OFFSET_HIGH_MASK	0x0000ffff
+#define ASYNC_HEADER_Q3_DATA_LENGTH_SHIFT	16
+#define ASYNC_HEADER_Q3_DATA_LENGTH_MASK	0xffff0000
+#define ASYNC_HEADER_Q3_EXTENDED_TCODE_SHIFT	0
+#define ASYNC_HEADER_Q3_EXTENDED_TCODE_MASK	0x0000ffff
+
+static inline unsigned int async_header_get_destination(const u32 header[ASYNC_HEADER_QUADLET_COUNT])
+{
+	return (header[0] & ASYNC_HEADER_Q0_DESTINATION_MASK) >> ASYNC_HEADER_Q0_DESTINATION_SHIFT;
+}
+
+static inline unsigned int async_header_get_tlabel(const u32 header[ASYNC_HEADER_QUADLET_COUNT])
+{
+	return (header[0] & ASYNC_HEADER_Q0_TLABEL_MASK) >> ASYNC_HEADER_Q0_TLABEL_SHIFT;
+}
+
+static inline unsigned int async_header_get_retry(const u32 header[ASYNC_HEADER_QUADLET_COUNT])
+{
+	return (header[0] & ASYNC_HEADER_Q0_RETRY_MASK) >> ASYNC_HEADER_Q0_RETRY_SHIFT;
+}
+
+static inline unsigned int async_header_get_tcode(const u32 header[ASYNC_HEADER_QUADLET_COUNT])
+{
+	return (header[0] & ASYNC_HEADER_Q0_TCODE_MASK) >> ASYNC_HEADER_Q0_TCODE_SHIFT;
+}
+
+static inline unsigned int async_header_get_priority(const u32 header[ASYNC_HEADER_QUADLET_COUNT])
+{
+	return (header[0] & ASYNC_HEADER_Q0_PRIORITY_MASK) >> ASYNC_HEADER_Q0_PRIORITY_SHIFT;
+}
+
+static inline unsigned int async_header_get_source(const u32 header[ASYNC_HEADER_QUADLET_COUNT])
+{
+	return (header[1] & ASYNC_HEADER_Q1_SOURCE_MASK) >> ASYNC_HEADER_Q1_SOURCE_SHIFT;
+}
+
+static inline unsigned int async_header_get_rcode(const u32 header[ASYNC_HEADER_QUADLET_COUNT])
+{
+	return (header[1] & ASYNC_HEADER_Q1_RCODE_MASK) >> ASYNC_HEADER_Q1_RCODE_SHIFT;
+}
+
+static inline u64 async_header_get_offset(const u32 header[ASYNC_HEADER_QUADLET_COUNT])
+{
+	u32 hi = (header[1] & ASYNC_HEADER_Q1_OFFSET_HIGH_MASK) >> ASYNC_HEADER_Q1_OFFSET_HIGH_SHIFT;
+	return (((u64)hi) << 32) | ((u64)header[2]);
+}
+
+static inline u32 async_header_get_quadlet_data(const u32 header[ASYNC_HEADER_QUADLET_COUNT])
+{
+	return header[3];
+}
+
+static inline unsigned int async_header_get_data_length(const u32 header[ASYNC_HEADER_QUADLET_COUNT])
+{
+	return (header[3] & ASYNC_HEADER_Q3_DATA_LENGTH_MASK) >> ASYNC_HEADER_Q3_DATA_LENGTH_SHIFT;
+}
+
+static inline unsigned int async_header_get_extended_tcode(const u32 header[ASYNC_HEADER_QUADLET_COUNT])
+{
+	return (header[3] & ASYNC_HEADER_Q3_EXTENDED_TCODE_MASK) >> ASYNC_HEADER_Q3_EXTENDED_TCODE_SHIFT;
+}
+
+static inline void async_header_set_destination(u32 header[ASYNC_HEADER_QUADLET_COUNT],
+						unsigned int destination)
+{
+	header[0] &= ~ASYNC_HEADER_Q0_DESTINATION_MASK;
+	header[0] |= (((u32)destination) << ASYNC_HEADER_Q0_DESTINATION_SHIFT) & ASYNC_HEADER_Q0_DESTINATION_MASK;
+}
+
+static inline void async_header_set_tlabel(u32 header[ASYNC_HEADER_QUADLET_COUNT],
+					   unsigned int tlabel)
+{
+	header[0] &= ~ASYNC_HEADER_Q0_TLABEL_MASK;
+	header[0] |= (((u32)tlabel) << ASYNC_HEADER_Q0_TLABEL_SHIFT) & ASYNC_HEADER_Q0_TLABEL_MASK;
+}
+
+static inline void async_header_set_retry(u32 header[ASYNC_HEADER_QUADLET_COUNT],
+					  unsigned int retry)
+{
+	header[0] &= ~ASYNC_HEADER_Q0_RETRY_MASK;
+	header[0] |= (((u32)retry) << ASYNC_HEADER_Q0_RETRY_SHIFT) & ASYNC_HEADER_Q0_RETRY_MASK;
+}
+
+static inline void async_header_set_tcode(u32 header[ASYNC_HEADER_QUADLET_COUNT],
+					  unsigned int tcode)
+{
+	header[0] &= ~ASYNC_HEADER_Q0_TCODE_MASK;
+	header[0] |= (((u32)tcode) << ASYNC_HEADER_Q0_TCODE_SHIFT) & ASYNC_HEADER_Q0_TCODE_MASK;
+}
+
+static inline void async_header_set_priority(u32 header[ASYNC_HEADER_QUADLET_COUNT],
+					     unsigned int priority)
+{
+	header[0] &= ~ASYNC_HEADER_Q0_PRIORITY_MASK;
+	header[0] |= (((u32)priority) << ASYNC_HEADER_Q0_PRIORITY_SHIFT) & ASYNC_HEADER_Q0_PRIORITY_MASK;
+}
+
+
+static inline void async_header_set_source(u32 header[ASYNC_HEADER_QUADLET_COUNT],
+					   unsigned int source)
+{
+	header[1] &= ~ASYNC_HEADER_Q1_SOURCE_MASK;
+	header[1] |= (((u32)source) << ASYNC_HEADER_Q1_SOURCE_SHIFT) & ASYNC_HEADER_Q1_SOURCE_MASK;
+}
+
+static inline void async_header_set_rcode(u32 header[ASYNC_HEADER_QUADLET_COUNT],
+					  unsigned int rcode)
+{
+	header[1] &= ~ASYNC_HEADER_Q1_RCODE_MASK;
+	header[1] |= (((u32)rcode) << ASYNC_HEADER_Q1_RCODE_SHIFT) & ASYNC_HEADER_Q1_RCODE_MASK;
+}
+
+static inline void async_header_set_offset(u32 header[ASYNC_HEADER_QUADLET_COUNT], u64 offset)
+{
+	u32 hi = (u32)(offset >> 32);
+	header[1] &= ~ASYNC_HEADER_Q1_OFFSET_HIGH_MASK;
+	header[1] |= (hi << ASYNC_HEADER_Q1_OFFSET_HIGH_SHIFT) & ASYNC_HEADER_Q1_OFFSET_HIGH_MASK;
+	header[2] = (u32)(offset & 0x00000000ffffffff);
+}
+
+static inline void async_header_set_quadlet_data(u32 header[ASYNC_HEADER_QUADLET_COUNT], u32 quadlet_data)
+{
+	header[3] = quadlet_data;
+}
+
+static inline void async_header_set_data_length(u32 header[ASYNC_HEADER_QUADLET_COUNT],
+						unsigned int data_length)
+{
+	header[3] &= ~ASYNC_HEADER_Q3_DATA_LENGTH_MASK;
+	header[3] |= (((u32)data_length) << ASYNC_HEADER_Q3_DATA_LENGTH_SHIFT) & ASYNC_HEADER_Q3_DATA_LENGTH_MASK;
+}
+
+static inline void async_header_set_extended_tcode(u32 header[ASYNC_HEADER_QUADLET_COUNT],
+						   unsigned int extended_tcode)
+{
+	header[3] &= ~ASYNC_HEADER_Q3_EXTENDED_TCODE_MASK;
+	header[3] |= (((u32)extended_tcode) << ASYNC_HEADER_Q3_EXTENDED_TCODE_SHIFT) & ASYNC_HEADER_Q3_EXTENDED_TCODE_MASK;
+}
+
+#define ISOC_HEADER_DATA_LENGTH_SHIFT		16
+#define ISOC_HEADER_DATA_LENGTH_MASK		0xffff0000
+#define ISOC_HEADER_TAG_SHIFT			14
+#define ISOC_HEADER_TAG_MASK			0x0000c000
+#define ISOC_HEADER_CHANNEL_SHIFT		8
+#define ISOC_HEADER_CHANNEL_MASK		0x00003f00
+#define ISOC_HEADER_TCODE_SHIFT			4
+#define ISOC_HEADER_TCODE_MASK			0x000000f0
+#define ISOC_HEADER_SY_SHIFT			0
+#define ISOC_HEADER_SY_MASK			0x0000000f
+
+static inline unsigned int isoc_header_get_data_length(u32 header)
+{
+	return (header & ISOC_HEADER_DATA_LENGTH_MASK) >> ISOC_HEADER_DATA_LENGTH_SHIFT;
+}
+
+static inline unsigned int isoc_header_get_tag(u32 header)
+{
+	return (header & ISOC_HEADER_TAG_MASK) >> ISOC_HEADER_TAG_SHIFT;
+}
+
+static inline unsigned int isoc_header_get_channel(u32 header)
+{
+	return (header & ISOC_HEADER_CHANNEL_MASK) >> ISOC_HEADER_CHANNEL_SHIFT;
+}
+
+static inline unsigned int isoc_header_get_tcode(u32 header)
+{
+	return (header & ISOC_HEADER_TCODE_MASK) >> ISOC_HEADER_TCODE_SHIFT;
+}
+
+static inline unsigned int isoc_header_get_sy(u32 header)
+{
+	return (header & ISOC_HEADER_SY_MASK) >> ISOC_HEADER_SY_SHIFT;
+}
+
+static inline void isoc_header_set_data_length(u32 *header, unsigned int data_length)
+{
+	*header &= ~ISOC_HEADER_DATA_LENGTH_MASK;
+	*header |= (((u32)data_length) << ISOC_HEADER_DATA_LENGTH_SHIFT) & ISOC_HEADER_DATA_LENGTH_MASK;
+}
+
+static inline void isoc_header_set_tag(u32 *header, unsigned int tag)
+{
+	*header &= ~ISOC_HEADER_TAG_MASK;
+	*header |= (((u32)tag) << ISOC_HEADER_TAG_SHIFT) & ISOC_HEADER_TAG_MASK;
+}
+
+static inline void isoc_header_set_channel(u32 *header, unsigned int channel)
+{
+	*header &= ~ISOC_HEADER_CHANNEL_MASK;
+	*header |= (((u32)channel) << ISOC_HEADER_CHANNEL_SHIFT) & ISOC_HEADER_CHANNEL_MASK;
+}
+
+static inline void isoc_header_set_tcode(u32 *header, unsigned int tcode)
+{
+	*header &= ~ISOC_HEADER_TCODE_MASK;
+	*header |= (((u32)tcode) << ISOC_HEADER_TCODE_SHIFT) & ISOC_HEADER_TCODE_MASK;
+}
+
+static inline void isoc_header_set_sy(u32 *header, unsigned int sy)
+{
+	*header &= ~ISOC_HEADER_SY_MASK;
+	*header |= (((u32)sy) << ISOC_HEADER_SY_SHIFT) & ISOC_HEADER_SY_MASK;
+}
+
+#endif // _FIREWIRE_PACKET_HEADER_DEFINITIONS_H