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, 354 insertions, 0 deletions

diff --git a/include/media/dvb_demux.h b/include/media/dvb_demux.h
new file mode 100644
index 000000000..3b6aeca7a
--- /dev/null
+++ b/include/media/dvb_demux.h
@@ -0,0 +1,354 @@
+/*
+ * dvb_demux.h: DVB kernel demux API
+ *
+ * Copyright (C) 2000-2001 Marcus Metzler & Ralph Metzler
+ *                         for convergence integrated media GmbH
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public License
+ * as published by the Free Software Foundation; either version 2.1
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#ifndef _DVB_DEMUX_H_
+#define _DVB_DEMUX_H_
+
+#include <linux/time.h>
+#include <linux/timer.h>
+#include <linux/spinlock.h>
+#include <linux/mutex.h>
+
+#include <media/demux.h>
+
+/**
+ * enum dvb_dmx_filter_type - type of demux feed.
+ *
+ * @DMX_TYPE_TS:	feed is in TS mode.
+ * @DMX_TYPE_SEC:	feed is in Section mode.
+ */
+enum dvb_dmx_filter_type {
+	DMX_TYPE_TS,
+	DMX_TYPE_SEC,
+};
+
+/**
+ * enum dvb_dmx_state - state machine for a demux filter.
+ *
+ * @DMX_STATE_FREE:		indicates that the filter is freed.
+ * @DMX_STATE_ALLOCATED:	indicates that the filter was allocated
+ *				to be used.
+ * @DMX_STATE_READY:		indicates that the filter is ready
+ *				to be used.
+ * @DMX_STATE_GO:		indicates that the filter is running.
+ */
+enum dvb_dmx_state {
+	DMX_STATE_FREE,
+	DMX_STATE_ALLOCATED,
+	DMX_STATE_READY,
+	DMX_STATE_GO,
+};
+
+#define DVB_DEMUX_MASK_MAX 18
+
+#define MAX_PID 0x1fff
+
+#define SPEED_PKTS_INTERVAL 50000
+
+/**
+ * struct dvb_demux_filter - Describes a DVB demux section filter.
+ *
+ * @filter:		Section filter as defined by &struct dmx_section_filter.
+ * @maskandmode:	logical ``and`` bit mask.
+ * @maskandnotmode:	logical ``and not`` bit mask.
+ * @doneq:		flag that indicates when a filter is ready.
+ * @next:		pointer to the next section filter.
+ * @feed:		&struct dvb_demux_feed pointer.
+ * @index:		index of the used demux filter.
+ * @state:		state of the filter as described by &enum dvb_dmx_state.
+ * @type:		type of the filter as described
+ *			by &enum dvb_dmx_filter_type.
+ */
+
+struct dvb_demux_filter {
+	struct dmx_section_filter filter;
+	u8 maskandmode[DMX_MAX_FILTER_SIZE];
+	u8 maskandnotmode[DMX_MAX_FILTER_SIZE];
+	bool doneq;
+
+	struct dvb_demux_filter *next;
+	struct dvb_demux_feed *feed;
+	int index;
+	enum dvb_dmx_state state;
+	enum dvb_dmx_filter_type type;
+
+	/* private: used only by av7110 */
+	u16 hw_handle;
+};
+
+/**
+ * struct dvb_demux_feed - describes a DVB field
+ *
+ * @feed:	a union describing a digital TV feed.
+ *		Depending on the feed type, it can be either
+ *		@feed.ts or @feed.sec.
+ * @feed.ts:	a &struct dmx_ts_feed pointer.
+ *		For TS feed only.
+ * @feed.sec:	a &struct dmx_section_feed pointer.
+ *		For section feed only.
+ * @cb:		a union describing digital TV callbacks.
+ *		Depending on the feed type, it can be either
+ *		@cb.ts or @cb.sec.
+ * @cb.ts:	a dmx_ts_cb() calback function pointer.
+ *		For TS feed only.
+ * @cb.sec:	a dmx_section_cb() callback function pointer.
+ *		For section feed only.
+ * @demux:	pointer to &struct dvb_demux.
+ * @priv:	private data that can optionally be used by a DVB driver.
+ * @type:	type of the filter, as defined by &enum dvb_dmx_filter_type.
+ * @state:	state of the filter as defined by &enum dvb_dmx_state.
+ * @pid:	PID to be filtered.
+ * @timeout:	feed timeout.
+ * @filter:	pointer to &struct dvb_demux_filter.
+ * @buffer_flags: Buffer flags used to report discontinuity users via DVB
+ *		  memory mapped API, as defined by &enum dmx_buffer_flags.
+ * @ts_type:	type of TS, as defined by &enum ts_filter_type.
+ * @pes_type:	type of PES, as defined by &enum dmx_ts_pes.
+ * @cc:		MPEG-TS packet continuity counter
+ * @pusi_seen:	if true, indicates that a discontinuity was detected.
+ *		it is used to prevent feeding of garbage from previous section.
+ * @peslen:	length of the PES (Packet Elementary Stream).
+ * @list_head:	head for the list of digital TV demux feeds.
+ * @index:	a unique index for each feed. Can be used as hardware
+ *		pid filter index.
+ */
+struct dvb_demux_feed {
+	union {
+		struct dmx_ts_feed ts;
+		struct dmx_section_feed sec;
+	} feed;
+
+	union {
+		dmx_ts_cb ts;
+		dmx_section_cb sec;
+	} cb;
+
+	struct dvb_demux *demux;
+	void *priv;
+	enum dvb_dmx_filter_type type;
+	enum dvb_dmx_state state;
+	u16 pid;
+
+	ktime_t timeout;
+	struct dvb_demux_filter *filter;
+
+	u32 buffer_flags;
+
+	enum ts_filter_type ts_type;
+	enum dmx_ts_pes pes_type;
+
+	int cc;
+	bool pusi_seen;
+
+	u16 peslen;
+
+	struct list_head list_head;
+	unsigned int index;
+};
+
+/**
+ * struct dvb_demux - represents a digital TV demux
+ * @dmx:		embedded &struct dmx_demux with demux capabilities
+ *			and callbacks.
+ * @priv:		private data that can optionally be used by
+ *			a DVB driver.
+ * @filternum:		maximum amount of DVB filters.
+ * @feednum:		maximum amount of DVB feeds.
+ * @start_feed:		callback routine to be called in order to start
+ *			a DVB feed.
+ * @stop_feed:		callback routine to be called in order to stop
+ *			a DVB feed.
+ * @write_to_decoder:	callback routine to be called if the feed is TS and
+ *			it is routed to an A/V decoder, when a new TS packet
+ *			is received.
+ *			Used only on av7110-av.c.
+ * @check_crc32:	callback routine to check CRC. If not initialized,
+ *			dvb_demux will use an internal one.
+ * @memcopy:		callback routine to memcopy received data.
+ *			If not initialized, dvb_demux will default to memcpy().
+ * @users:		counter for the number of demux opened file descriptors.
+ *			Currently, it is limited to 10 users.
+ * @filter:		pointer to &struct dvb_demux_filter.
+ * @feed:		pointer to &struct dvb_demux_feed.
+ * @frontend_list:	&struct list_head with frontends used by the demux.
+ * @pesfilter:		array of &struct dvb_demux_feed with the PES types
+ *			that will be filtered.
+ * @pids:		list of filtered program IDs.
+ * @feed_list:		&struct list_head with feeds.
+ * @tsbuf:		temporary buffer used internally to store TS packets.
+ * @tsbufp:		temporary buffer index used internally.
+ * @mutex:		pointer to &struct mutex used to protect feed set
+ *			logic.
+ * @lock:		pointer to &spinlock_t, used to protect buffer handling.
+ * @cnt_storage:	buffer used for TS/TEI continuity check.
+ * @speed_last_time:	&ktime_t used for TS speed check.
+ * @speed_pkts_cnt:	packets count used for TS speed check.
+ */
+struct dvb_demux {
+	struct dmx_demux dmx;
+	void *priv;
+	int filternum;
+	int feednum;
+	int (*start_feed)(struct dvb_demux_feed *feed);
+	int (*stop_feed)(struct dvb_demux_feed *feed);
+	int (*write_to_decoder)(struct dvb_demux_feed *feed,
+				 const u8 *buf, size_t len);
+	u32 (*check_crc32)(struct dvb_demux_feed *feed,
+			    const u8 *buf, size_t len);
+	void (*memcopy)(struct dvb_demux_feed *feed, u8 *dst,
+			 const u8 *src, size_t len);
+
+	int users;
+#define MAX_DVB_DEMUX_USERS 10
+	struct dvb_demux_filter *filter;
+	struct dvb_demux_feed *feed;
+
+	struct list_head frontend_list;
+
+	struct dvb_demux_feed *pesfilter[DMX_PES_OTHER];
+	u16 pids[DMX_PES_OTHER];
+
+#define DMX_MAX_PID 0x2000
+	struct list_head feed_list;
+	u8 tsbuf[204];
+	int tsbufp;
+
+	struct mutex mutex;
+	spinlock_t lock;
+
+	uint8_t *cnt_storage; /* for TS continuity check */
+
+	ktime_t speed_last_time; /* for TS speed check */
+	uint32_t speed_pkts_cnt; /* for TS speed check */
+
+	/* private: used only on av7110 */
+	int playing;
+	int recording;
+};
+
+/**
+ * dvb_dmx_init - initialize a digital TV demux struct.
+ *
+ * @demux: &struct dvb_demux to be initialized.
+ *
+ * Before being able to register a digital TV demux struct, drivers
+ * should call this routine. On its typical usage, some fields should
+ * be initialized at the driver before calling it.
+ *
+ * A typical usecase is::
+ *
+ *	dvb->demux.dmx.capabilities =
+ *		DMX_TS_FILTERING | DMX_SECTION_FILTERING |
+ *		DMX_MEMORY_BASED_FILTERING;
+ *	dvb->demux.priv       = dvb;
+ *	dvb->demux.filternum  = 256;
+ *	dvb->demux.feednum    = 256;
+ *	dvb->demux.start_feed = driver_start_feed;
+ *	dvb->demux.stop_feed  = driver_stop_feed;
+ *	ret = dvb_dmx_init(&dvb->demux);
+ *	if (ret < 0)
+ *		return ret;
+ */
+int dvb_dmx_init(struct dvb_demux *demux);
+
+/**
+ * dvb_dmx_release - releases a digital TV demux internal buffers.
+ *
+ * @demux: &struct dvb_demux to be released.
+ *
+ * The DVB core internally allocates data at @demux. This routine
+ * releases those data. Please notice that the struct itelf is not
+ * released, as it can be embedded on other structs.
+ */
+void dvb_dmx_release(struct dvb_demux *demux);
+
+/**
+ * dvb_dmx_swfilter_packets - use dvb software filter for a buffer with
+ *	multiple MPEG-TS packets with 188 bytes each.
+ *
+ * @demux: pointer to &struct dvb_demux
+ * @buf: buffer with data to be filtered
+ * @count: number of MPEG-TS packets with size of 188.
+ *
+ * The routine will discard a DVB packet that don't start with 0x47.
+ *
+ * Use this routine if the DVB demux fills MPEG-TS buffers that are
+ * already aligned.
+ *
+ * NOTE: The @buf size should have size equal to ``count * 188``.
+ */
+void dvb_dmx_swfilter_packets(struct dvb_demux *demux, const u8 *buf,
+			      size_t count);
+
+/**
+ * dvb_dmx_swfilter -  use dvb software filter for a buffer with
+ *	multiple MPEG-TS packets with 188 bytes each.
+ *
+ * @demux: pointer to &struct dvb_demux
+ * @buf: buffer with data to be filtered
+ * @count: number of MPEG-TS packets with size of 188.
+ *
+ * If a DVB packet doesn't start with 0x47, it will seek for the first
+ * byte that starts with 0x47.
+ *
+ * Use this routine if the DVB demux fill buffers that may not start with
+ * a packet start mark (0x47).
+ *
+ * NOTE: The @buf size should have size equal to ``count * 188``.
+ */
+void dvb_dmx_swfilter(struct dvb_demux *demux, const u8 *buf, size_t count);
+
+/**
+ * dvb_dmx_swfilter_204 -  use dvb software filter for a buffer with
+ *	multiple MPEG-TS packets with 204 bytes each.
+ *
+ * @demux: pointer to &struct dvb_demux
+ * @buf: buffer with data to be filtered
+ * @count: number of MPEG-TS packets with size of 204.
+ *
+ * If a DVB packet doesn't start with 0x47, it will seek for the first
+ * byte that starts with 0x47.
+ *
+ * Use this routine if the DVB demux fill buffers that may not start with
+ * a packet start mark (0x47).
+ *
+ * NOTE: The @buf size should have size equal to ``count * 204``.
+ */
+void dvb_dmx_swfilter_204(struct dvb_demux *demux, const u8 *buf,
+			  size_t count);
+
+/**
+ * dvb_dmx_swfilter_raw -  make the raw data available to userspace without
+ *	filtering
+ *
+ * @demux: pointer to &struct dvb_demux
+ * @buf: buffer with data
+ * @count: number of packets to be passed. The actual size of each packet
+ *	depends on the &dvb_demux->feed->cb.ts logic.
+ *
+ * Use it if the driver needs to deliver the raw payload to userspace without
+ * passing through the kernel demux. That is meant to support some
+ * delivery systems that aren't based on MPEG-TS.
+ *
+ * This function relies on &dvb_demux->feed->cb.ts to actually handle the
+ * buffer.
+ */
+void dvb_dmx_swfilter_raw(struct dvb_demux *demux, const u8 *buf,
+			  size_t count);
+
+#endif /* _DVB_DEMUX_H_ */