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, 437 insertions, 0 deletions

diff --git a/tools/perf/util/event.h b/tools/perf/util/event.h
new file mode 100644
index 000000000..2ea83fdf8
--- /dev/null
+++ b/tools/perf/util/event.h
@@ -0,0 +1,437 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __PERF_RECORD_H
+#define __PERF_RECORD_H
+/*
+ * The linux/stddef.h isn't need here, but is needed for __always_inline used
+ * in files included from uapi/linux/perf_event.h such as
+ * /usr/include/linux/swab.h and /usr/include/linux/byteorder/little_endian.h,
+ * detected in at least musl libc, used in Alpine Linux. -acme
+ */
+#include <stdio.h>
+#include <linux/stddef.h>
+#include <perf/event.h>
+#include <linux/types.h>
+
+struct dso;
+struct machine;
+struct perf_event_attr;
+struct perf_sample;
+
+#ifdef __LP64__
+/*
+ * /usr/include/inttypes.h uses just 'lu' for PRIu64, but we end up defining
+ * __u64 as long long unsigned int, and then -Werror=format= kicks in and
+ * complains of the mismatched types, so use these two special extra PRI
+ * macros to overcome that.
+ */
+#define PRI_lu64 "l" PRIu64
+#define PRI_lx64 "l" PRIx64
+#define PRI_ld64 "l" PRId64
+#else
+#define PRI_lu64 PRIu64
+#define PRI_lx64 PRIx64
+#define PRI_ld64 PRId64
+#endif
+
+#define PERF_SAMPLE_MASK				\
+	(PERF_SAMPLE_IP | PERF_SAMPLE_TID |		\
+	 PERF_SAMPLE_TIME | PERF_SAMPLE_ADDR |		\
+	PERF_SAMPLE_ID | PERF_SAMPLE_STREAM_ID |	\
+	 PERF_SAMPLE_CPU | PERF_SAMPLE_PERIOD |		\
+	 PERF_SAMPLE_IDENTIFIER)
+
+/* perf sample has 16 bits size limit */
+#define PERF_SAMPLE_MAX_SIZE (1 << 16)
+
+struct ip_callchain {
+	u64 nr;
+	u64 ips[];
+};
+
+struct branch_stack;
+
+enum {
+	PERF_IP_FLAG_BRANCH		= 1ULL << 0,
+	PERF_IP_FLAG_CALL		= 1ULL << 1,
+	PERF_IP_FLAG_RETURN		= 1ULL << 2,
+	PERF_IP_FLAG_CONDITIONAL	= 1ULL << 3,
+	PERF_IP_FLAG_SYSCALLRET		= 1ULL << 4,
+	PERF_IP_FLAG_ASYNC		= 1ULL << 5,
+	PERF_IP_FLAG_INTERRUPT		= 1ULL << 6,
+	PERF_IP_FLAG_TX_ABORT		= 1ULL << 7,
+	PERF_IP_FLAG_TRACE_BEGIN	= 1ULL << 8,
+	PERF_IP_FLAG_TRACE_END		= 1ULL << 9,
+	PERF_IP_FLAG_IN_TX		= 1ULL << 10,
+	PERF_IP_FLAG_VMENTRY		= 1ULL << 11,
+	PERF_IP_FLAG_VMEXIT		= 1ULL << 12,
+	PERF_IP_FLAG_INTR_DISABLE	= 1ULL << 13,
+	PERF_IP_FLAG_INTR_TOGGLE	= 1ULL << 14,
+	PERF_IP_FLAG_BRANCH_MISS	= 1ULL << 15,
+	PERF_IP_FLAG_NOT_TAKEN		= 1ULL << 16,
+};
+
+#define PERF_IP_FLAG_CHARS "bcrosyiABExghDtmn"
+
+#define PERF_ADDITIONAL_STATE_MASK	\
+	(PERF_IP_FLAG_IN_TX |		\
+	 PERF_IP_FLAG_INTR_DISABLE |	\
+	 PERF_IP_FLAG_INTR_TOGGLE)
+
+#define PERF_BRANCH_MASK		(\
+	PERF_IP_FLAG_BRANCH		|\
+	PERF_IP_FLAG_CALL		|\
+	PERF_IP_FLAG_RETURN		|\
+	PERF_IP_FLAG_CONDITIONAL	|\
+	PERF_IP_FLAG_SYSCALLRET		|\
+	PERF_IP_FLAG_ASYNC		|\
+	PERF_IP_FLAG_INTERRUPT		|\
+	PERF_IP_FLAG_TX_ABORT		|\
+	PERF_IP_FLAG_TRACE_BEGIN	|\
+	PERF_IP_FLAG_TRACE_END		|\
+	PERF_IP_FLAG_VMENTRY		|\
+	PERF_IP_FLAG_VMEXIT)
+
+#define PERF_IP_FLAG_BRANCH_EVENT_MASK	\
+	(PERF_IP_FLAG_BRANCH_MISS |	\
+	 PERF_IP_FLAG_NOT_TAKEN)
+
+#define PERF_MEM_DATA_SRC_NONE \
+	(PERF_MEM_S(OP, NA) |\
+	 PERF_MEM_S(LVL, NA) |\
+	 PERF_MEM_S(SNOOP, NA) |\
+	 PERF_MEM_S(LOCK, NA) |\
+	 PERF_MEM_S(TLB, NA) |\
+	 PERF_MEM_S(LVLNUM, NA))
+
+/* Attribute type for custom synthesized events */
+#define PERF_TYPE_SYNTH		(INT_MAX + 1U)
+
+/* Attribute config for custom synthesized events */
+enum perf_synth_id {
+	PERF_SYNTH_INTEL_PTWRITE,
+	PERF_SYNTH_INTEL_MWAIT,
+	PERF_SYNTH_INTEL_PWRE,
+	PERF_SYNTH_INTEL_EXSTOP,
+	PERF_SYNTH_INTEL_PWRX,
+	PERF_SYNTH_INTEL_CBR,
+	PERF_SYNTH_INTEL_PSB,
+	PERF_SYNTH_INTEL_EVT,
+	PERF_SYNTH_INTEL_IFLAG_CHG,
+	PERF_SYNTH_POWERPC_VPA_DTL,
+};
+
+/*
+ * Raw data formats for synthesized events. Note that 4 bytes of padding are
+ * present to match the 'size' member of PERF_SAMPLE_RAW data which is always
+ * 8-byte aligned. That means we must dereference raw_data with an offset of 4.
+ * Refer perf_sample__synth_ptr() and perf_synth__raw_data().  It also means the
+ * structure sizes are 4 bytes bigger than the raw_size, refer
+ * perf_synth__raw_size().
+ */
+
+struct perf_synth_intel_ptwrite {
+	u32 padding;
+	union {
+		struct {
+			u32	ip		:  1,
+				reserved	: 31;
+		};
+		u32	flags;
+	};
+	u64	payload;
+};
+
+struct perf_synth_intel_mwait {
+	u32 padding;
+	u32 reserved;
+	union {
+		struct {
+			u64	hints		:  8,
+				reserved1	: 24,
+				extensions	:  2,
+				reserved2	: 30;
+		};
+		u64	payload;
+	};
+};
+
+struct perf_synth_intel_pwre {
+	u32 padding;
+	u32 reserved;
+	union {
+		struct {
+			u64	reserved1	:  7,
+				hw		:  1,
+				subcstate	:  4,
+				cstate		:  4,
+				reserved2	: 48;
+		};
+		u64	payload;
+	};
+};
+
+struct perf_synth_intel_exstop {
+	u32 padding;
+	union {
+		struct {
+			u32	ip		:  1,
+				reserved	: 31;
+		};
+		u32	flags;
+	};
+};
+
+struct perf_synth_intel_pwrx {
+	u32 padding;
+	u32 reserved;
+	union {
+		struct {
+			u64	deepest_cstate	:  4,
+				last_cstate	:  4,
+				wake_reason	:  4,
+				reserved1	: 52;
+		};
+		u64	payload;
+	};
+};
+
+struct perf_synth_intel_cbr {
+	u32 padding;
+	union {
+		struct {
+			u32	cbr		:  8,
+				reserved1	:  8,
+				max_nonturbo	:  8,
+				reserved2	:  8;
+		};
+		u32	flags;
+	};
+	u32 freq;
+	u32 reserved3;
+};
+
+struct perf_synth_intel_psb {
+	u32 padding;
+	u32 reserved;
+	u64 offset;
+};
+
+struct perf_synth_intel_evd {
+	union {
+		struct {
+			u8	evd_type;
+			u8	reserved[7];
+		};
+		u64	et;
+	};
+	u64	payload;
+};
+
+/* Intel PT Event Trace */
+struct perf_synth_intel_evt {
+	u32 padding;
+	union {
+		struct {
+			u32	type		:  5,
+				reserved	:  2,
+				ip		:  1,
+				vector		:  8,
+				evd_cnt		: 16;
+		};
+		u32	cfe;
+	};
+	struct perf_synth_intel_evd evd[0];
+};
+
+struct perf_synth_intel_iflag_chg {
+	u32 padding;
+	union {
+		struct {
+			u32	iflag		:  1,
+				via_branch	:  1;
+		};
+		u32	flags;
+	};
+	u64	branch_ip; /* If via_branch */
+};
+
+/*
+ * The powerpc VPA DTL entries are of below format
+ */
+struct powerpc_vpadtl_entry {
+	u8      dispatch_reason;
+	u8      preempt_reason;
+	u16     processor_id;
+	u32     enqueue_to_dispatch_time;
+	u32     ready_to_enqueue_time;
+	u32     waiting_to_ready_time;
+	u64     timebase;
+	u64     fault_addr;
+	u64     srr0;
+	u64     srr1;
+};
+
+extern const char *dispatch_reasons[11];
+extern const char *preempt_reasons[10];
+
+static inline void *perf_synth__raw_data(void *p)
+{
+	return p + 4;
+}
+
+#define perf_synth__raw_size(d) (sizeof(d) - 4)
+
+#define perf_sample__bad_synth_size(s, d) ((s)->raw_size < sizeof(d) - 4)
+
+enum {
+	PERF_STAT_ROUND_TYPE__INTERVAL	= 0,
+	PERF_STAT_ROUND_TYPE__FINAL	= 1,
+};
+
+void perf_event__print_totals(void);
+
+struct perf_cpu_map;
+struct perf_record_stat_config;
+struct perf_stat_config;
+struct perf_tool;
+
+void perf_event__read_stat_config(struct perf_stat_config *config,
+				  struct perf_record_stat_config *event);
+
+int perf_event__process_comm(const struct perf_tool *tool,
+			     union perf_event *event,
+			     struct perf_sample *sample,
+			     struct machine *machine);
+int perf_event__process_lost(const struct perf_tool *tool,
+			     union perf_event *event,
+			     struct perf_sample *sample,
+			     struct machine *machine);
+int perf_event__process_lost_samples(const struct perf_tool *tool,
+				     union perf_event *event,
+				     struct perf_sample *sample,
+				     struct machine *machine);
+int perf_event__process_aux(const struct perf_tool *tool,
+			    union perf_event *event,
+			    struct perf_sample *sample,
+			    struct machine *machine);
+int perf_event__process_itrace_start(const struct perf_tool *tool,
+				     union perf_event *event,
+				     struct perf_sample *sample,
+				     struct machine *machine);
+int perf_event__process_aux_output_hw_id(const struct perf_tool *tool,
+					 union perf_event *event,
+					 struct perf_sample *sample,
+					 struct machine *machine);
+int perf_event__process_switch(const struct perf_tool *tool,
+			       union perf_event *event,
+			       struct perf_sample *sample,
+			       struct machine *machine);
+int perf_event__process_namespaces(const struct perf_tool *tool,
+				   union perf_event *event,
+				   struct perf_sample *sample,
+				   struct machine *machine);
+int perf_event__process_cgroup(const struct perf_tool *tool,
+			       union perf_event *event,
+			       struct perf_sample *sample,
+			       struct machine *machine);
+int perf_event__process_mmap(const struct perf_tool *tool,
+			     union perf_event *event,
+			     struct perf_sample *sample,
+			     struct machine *machine);
+int perf_event__process_mmap2(const struct perf_tool *tool,
+			     union perf_event *event,
+			     struct perf_sample *sample,
+			     struct machine *machine);
+int perf_event__process_fork(const struct perf_tool *tool,
+			     union perf_event *event,
+			     struct perf_sample *sample,
+			     struct machine *machine);
+int perf_event__process_exit(const struct perf_tool *tool,
+			     union perf_event *event,
+			     struct perf_sample *sample,
+			     struct machine *machine);
+int perf_event__exit_del_thread(const struct perf_tool *tool,
+				union perf_event *event,
+				struct perf_sample *sample,
+				struct machine *machine);
+int perf_event__process_ksymbol(const struct perf_tool *tool,
+				union perf_event *event,
+				struct perf_sample *sample,
+				struct machine *machine);
+int perf_event__process_bpf(const struct perf_tool *tool,
+			    union perf_event *event,
+			    struct perf_sample *sample,
+			    struct machine *machine);
+int perf_event__process_text_poke(const struct perf_tool *tool,
+				  union perf_event *event,
+				  struct perf_sample *sample,
+				  struct machine *machine);
+int perf_event__process(const struct perf_tool *tool,
+			union perf_event *event,
+			struct perf_sample *sample,
+			struct machine *machine);
+
+bool is_bts_event(struct perf_event_attr *attr);
+bool sample_addr_correlates_sym(struct perf_event_attr *attr);
+
+const char *perf_event__name(unsigned int id);
+
+size_t perf_event__fprintf_comm(union perf_event *event, FILE *fp);
+size_t perf_event__fprintf_mmap(union perf_event *event, FILE *fp);
+size_t perf_event__fprintf_mmap2(union perf_event *event, FILE *fp);
+size_t perf_event__fprintf_task(union perf_event *event, FILE *fp);
+size_t perf_event__fprintf_aux(union perf_event *event, FILE *fp);
+size_t perf_event__fprintf_itrace_start(union perf_event *event, FILE *fp);
+size_t perf_event__fprintf_aux_output_hw_id(union perf_event *event, FILE *fp);
+size_t perf_event__fprintf_switch(union perf_event *event, FILE *fp);
+size_t perf_event__fprintf_thread_map(union perf_event *event, FILE *fp);
+size_t perf_event__fprintf_cpu_map(union perf_event *event, FILE *fp);
+size_t perf_event__fprintf_namespaces(union perf_event *event, FILE *fp);
+size_t perf_event__fprintf_cgroup(union perf_event *event, FILE *fp);
+size_t perf_event__fprintf_ksymbol(union perf_event *event, FILE *fp);
+size_t perf_event__fprintf_bpf(union perf_event *event, FILE *fp);
+size_t perf_event__fprintf_bpf_metadata(union perf_event *event, FILE *fp);
+size_t perf_event__fprintf_text_poke(union perf_event *event, struct machine *machine,FILE *fp);
+size_t perf_event__fprintf_schedstat_cpu(union perf_event *event, FILE *fp);
+size_t perf_event__fprintf_schedstat_domain(union perf_event *event, FILE *fp);
+size_t perf_event__fprintf(union perf_event *event, struct machine *machine, FILE *fp);
+
+int kallsyms__get_function_start(const char *kallsyms_filename,
+				 const char *symbol_name, u64 *addr);
+int kallsyms__get_symbol_start(const char *kallsyms_filename,
+			       const char *symbol_name, u64 *addr);
+
+void event_attr_init(struct perf_event_attr *attr);
+
+int perf_event_paranoid(void);
+bool perf_event_paranoid_check(int max_level);
+
+extern int sysctl_perf_event_max_stack;
+extern int sysctl_perf_event_max_contexts_per_stack;
+extern unsigned int proc_map_timeout;
+
+#define PAGE_SIZE_NAME_LEN	32
+char *get_page_size_name(u64 size, char *str);
+
+static inline bool perf_event_header__cpumode_is_guest(u8 cpumode)
+{
+	return cpumode == PERF_RECORD_MISC_GUEST_KERNEL ||
+	       cpumode == PERF_RECORD_MISC_GUEST_USER;
+}
+
+static inline bool perf_event_header__misc_is_guest(u16 misc)
+{
+	return perf_event_header__cpumode_is_guest(misc & PERF_RECORD_MISC_CPUMODE_MASK);
+}
+
+static inline bool perf_event_header__is_guest(const struct perf_event_header *header)
+{
+	return perf_event_header__misc_is_guest(header->misc);
+}
+
+static inline bool perf_event__is_guest(const union perf_event *event)
+{
+	return perf_event_header__is_guest(&event->header);
+}
+
+#endif /* __PERF_RECORD_H */