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, 162 insertions, 0 deletions

diff --git a/tools/perf/util/trace-event.h b/tools/perf/util/trace-event.h
new file mode 100644
index 000000000..720121c74
--- /dev/null
+++ b/tools/perf/util/trace-event.h
@@ -0,0 +1,162 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _PERF_UTIL_TRACE_EVENT_H
+#define _PERF_UTIL_TRACE_EVENT_H
+
+#include <stdbool.h>
+#include <stdio.h>
+#include <sys/types.h>
+#include <linux/types.h>
+
+struct evlist;
+struct machine;
+struct perf_sample;
+union perf_event;
+struct perf_tool;
+struct thread;
+struct tep_plugin_list;
+struct evsel;
+struct tep_format_field;
+
+struct trace_event {
+	struct tep_handle	*pevent;
+	struct tep_plugin_list	*plugin_list;
+};
+
+/* Computes a version number comparable with LIBTRACEEVENT_VERSION from Makefile.config. */
+#define MAKE_LIBTRACEEVENT_VERSION(a, b, c) ((a)*255*255+(b)*255+(c))
+
+typedef char *(tep_func_resolver_t)(void *priv,
+				    unsigned long long *addrp, char **modp);
+
+bool have_tracepoints(struct list_head *evlist);
+
+int trace_event__init(struct trace_event *t);
+void trace_event__cleanup(struct trace_event *t);
+int trace_event__register_resolver(struct machine *machine,
+				   tep_func_resolver_t *func);
+struct tep_event*
+trace_event__tp_format(const char *sys, const char *name);
+
+struct tep_event *trace_event__tp_format_id(int id);
+
+void event_format__fprintf(const struct tep_event *event,
+			   int cpu, void *data, int size, FILE *fp);
+
+int parse_ftrace_file(struct tep_handle *pevent, char *buf, unsigned long size);
+int parse_event_file(struct tep_handle *pevent,
+		     char *buf, unsigned long size, char *sys);
+
+unsigned long long
+raw_field_value(struct tep_event *event, const char *name, void *data);
+
+const char *parse_task_states(struct tep_format_field *state_field);
+
+void parse_proc_kallsyms(struct tep_handle *pevent, char *file, unsigned int size);
+void parse_ftrace_printk(struct tep_handle *pevent, char *file, unsigned int size);
+void parse_saved_cmdline(struct tep_handle *pevent, char *file, unsigned int size);
+
+ssize_t trace_report(int fd, struct trace_event *tevent, bool repipe);
+
+unsigned long long read_size(struct tep_event *event, void *ptr, int size);
+unsigned long long eval_flag(const char *flag);
+
+int read_tracing_data(int fd, struct list_head *pattrs);
+
+/*
+ * Return the tracepoint name in the format "subsystem:event_name",
+ * callers should free the returned string.
+ */
+char *tracepoint_id_to_name(u64 config);
+
+struct tracing_data {
+	/* size is only valid if temp is 'true' */
+	ssize_t size;
+	bool temp;
+	char temp_file[50];
+};
+
+struct tracing_data *tracing_data_get(struct list_head *pattrs,
+				      int fd, bool temp);
+int tracing_data_put(struct tracing_data *tdata);
+
+
+struct addr_location;
+
+struct perf_session;
+struct perf_stat_config;
+
+struct scripting_ops {
+	const char *name;
+	const char *dirname; /* For script path .../scripts/<dirname>/... */
+	int (*start_script)(const char *script, int argc, const char **argv,
+			    struct perf_session *session);
+	int (*flush_script) (void);
+	int (*stop_script) (void);
+	void (*process_event) (union perf_event *event,
+			       struct perf_sample *sample,
+			       struct addr_location *al,
+			       struct addr_location *addr_al);
+	void (*process_switch)(union perf_event *event,
+			       struct perf_sample *sample,
+			       struct machine *machine);
+	void (*process_auxtrace_error)(struct perf_session *session,
+				       union perf_event *event);
+	void (*process_stat)(struct perf_stat_config *config,
+			     struct evsel *evsel, u64 tstamp);
+	void (*process_stat_interval)(u64 tstamp);
+	void (*process_throttle)(union perf_event *event,
+				 struct perf_sample *sample,
+				 struct machine *machine);
+	int (*generate_script) (struct tep_handle *pevent, const char *outfile);
+};
+
+extern unsigned int scripting_max_stack;
+
+struct scripting_ops *script_spec__lookup(const char *spec);
+int script_spec__for_each(int (*cb)(struct scripting_ops *ops, const char *spec));
+
+void setup_perl_scripting(void);
+void setup_python_scripting(void);
+
+struct scripting_context {
+	struct tep_handle *pevent;
+	void *event_data;
+	union perf_event *event;
+	struct perf_sample *sample;
+	struct addr_location *al;
+	struct addr_location *addr_al;
+	struct perf_session *session;
+};
+
+void scripting_context__update(struct scripting_context *scripting_context,
+			       union perf_event *event,
+			       struct perf_sample *sample,
+			       struct addr_location *al,
+			       struct addr_location *addr_al);
+
+int common_pc(struct scripting_context *context);
+int common_flags(struct scripting_context *context);
+int common_lock_depth(struct scripting_context *context);
+
+#define SAMPLE_FLAGS_BUF_SIZE 64
+#define SAMPLE_FLAGS_STR_ALIGNED_SIZE	21
+
+int perf_sample__sprintf_flags(u32 flags, char *str, size_t sz);
+
+#if defined(LIBTRACEEVENT_VERSION) &&  LIBTRACEEVENT_VERSION >= MAKE_LIBTRACEEVENT_VERSION(1, 5, 0)
+#include <event-parse.h>
+
+static inline bool tep_field_is_relative(unsigned long flags)
+{
+	return (flags & TEP_FIELD_IS_RELATIVE) != 0;
+}
+#else
+#include <linux/compiler.h>
+
+static inline bool tep_field_is_relative(unsigned long flags __maybe_unused)
+{
+	return false;
+}
+#endif
+
+#endif /* _PERF_UTIL_TRACE_EVENT_H */