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, 647 insertions, 0 deletions

diff --git a/tools/perf/util/parse-events.y b/tools/perf/util/parse-events.y
new file mode 100644
index 000000000..c194de5ec
--- /dev/null
+++ b/tools/perf/util/parse-events.y
@@ -0,0 +1,647 @@
+%define api.pure full
+%parse-param {void *_parse_state}
+%parse-param {void *scanner}
+%lex-param {void* scanner}
+%locations
+
+%{
+
+#ifndef NDEBUG
+#define YYDEBUG 1
+#endif
+
+#include <errno.h>
+#include <linux/compiler.h>
+#include <linux/types.h>
+#include "pmu.h"
+#include "pmus.h"
+#include "evsel.h"
+#include "parse-events.h"
+#include "parse-events-bison.h"
+
+int parse_events_lex(YYSTYPE * yylval_param, YYLTYPE * yylloc_param , void *yyscanner);
+void parse_events_error(YYLTYPE *loc, void *parse_state, void *scanner, char const *msg);
+
+#define PE_ABORT(val) \
+do { \
+	if (val == -ENOMEM) \
+		YYNOMEM; \
+	YYABORT; \
+} while (0)
+
+static struct list_head* alloc_list(void)
+{
+	struct list_head *list;
+
+	list = malloc(sizeof(*list));
+	if (!list)
+		return NULL;
+
+	INIT_LIST_HEAD(list);
+	return list;
+}
+
+static void free_list_evsel(struct list_head* list_evsel)
+{
+	struct evsel *evsel, *tmp;
+
+	list_for_each_entry_safe(evsel, tmp, list_evsel, core.node) {
+		list_del_init(&evsel->core.node);
+		evsel__delete(evsel);
+	}
+	free(list_evsel);
+}
+
+%}
+
+%token PE_START_EVENTS PE_START_TERMS
+%token PE_VALUE PE_TERM
+%token PE_EVENT_NAME
+%token PE_RAW PE_NAME
+%token PE_MODIFIER_EVENT PE_MODIFIER_BP PE_BP_COLON PE_BP_SLASH
+%token PE_PREFIX_MEM
+%token PE_ERROR
+%token PE_DRV_CFG_TERM
+%type <num> PE_VALUE
+%type <mod> PE_MODIFIER_EVENT
+%type <term_type> PE_TERM
+%type <str> PE_RAW
+%type <str> PE_NAME
+%type <str> PE_MODIFIER_BP
+%type <str> PE_EVENT_NAME
+%type <str> PE_DRV_CFG_TERM
+%type <str> name_or_raw
+%destructor { free ($$); } <str>
+%type <term> event_term
+%destructor { parse_events_term__delete ($$); } <term>
+%type <list_terms> event_config
+%type <list_terms> opt_event_config
+%type <list_terms> opt_pmu_config
+%destructor { parse_events_terms__delete ($$); } <list_terms>
+%type <list_evsel> event_pmu
+%type <list_evsel> event_legacy_mem
+%type <list_evsel> event_legacy_tracepoint
+%type <list_evsel> event_legacy_numeric
+%type <list_evsel> event_legacy_raw
+%type <list_evsel> event_def
+%type <list_evsel> event_mod
+%type <list_evsel> event_name
+%type <list_evsel> event
+%type <list_evsel> events
+%type <list_evsel> group_def
+%type <list_evsel> group
+%type <list_evsel> groups
+%destructor { free_list_evsel ($$); } <list_evsel>
+%type <tracepoint_name> tracepoint_name
+%destructor { free ($$.sys); free ($$.event); } <tracepoint_name>
+
+%union
+{
+	char *str;
+	u64 num;
+	struct parse_events_modifier mod;
+	enum parse_events__term_type term_type;
+	struct list_head *list_evsel;
+	struct parse_events_terms *list_terms;
+	struct parse_events_term *term;
+	struct tracepoint_name {
+		char *sys;
+		char *event;
+	} tracepoint_name;
+}
+%%
+
+ /*
+  * Entry points. We are either parsing events or terminals. Just terminal
+  * parsing is used for parsing events in sysfs.
+  */
+start:
+PE_START_EVENTS start_events
+|
+PE_START_TERMS  start_terms
+
+start_events: groups
+{
+	/* Take the parsed events, groups.. and place into parse_state. */
+	struct list_head *groups  = $1;
+	struct parse_events_state *parse_state = _parse_state;
+
+	list_splice_tail(groups, &parse_state->list);
+	free(groups);
+}
+
+groups: /* A list of groups or events. */
+groups ',' group
+{
+	/* Merge group into the list of events/groups. */
+	struct list_head *groups  = $1;
+	struct list_head *group  = $3;
+
+	list_splice_tail(group, groups);
+	free(group);
+	$$ = groups;
+}
+|
+groups ',' event
+{
+	/* Merge event into the list of events/groups. */
+	struct list_head *groups  = $1;
+	struct list_head *event = $3;
+
+
+	list_splice_tail(event, groups);
+	free(event);
+	$$ = groups;
+}
+|
+group
+|
+event
+
+group:
+group_def ':' PE_MODIFIER_EVENT
+{
+	/* Apply the modifier to the events in the group_def. */
+	struct list_head *list = $1;
+	int err;
+
+	err = parse_events__modifier_group(_parse_state, &@3, list, $3);
+	if (err)
+		YYABORT;
+	$$ = list;
+}
+|
+group_def
+
+group_def:
+PE_NAME '{' events '}'
+{
+	struct list_head *list = $3;
+
+	/*
+	 * Set the first entry of list to be the leader. Set the group name on
+	 * the leader to $1 taking ownership.
+	 */
+	parse_events__set_leader($1, list);
+	$$ = list;
+}
+|
+'{' events '}'
+{
+	struct list_head *list = $2;
+
+	/* Set the first entry of list to be the leader clearing the group name. */
+	parse_events__set_leader(NULL, list);
+	$$ = list;
+}
+
+events:
+events ',' event
+{
+	struct list_head *events  = $1;
+	struct list_head *event = $3;
+
+	list_splice_tail(event, events);
+	free(event);
+	$$ = events;
+}
+|
+event
+
+event: event_mod
+
+event_mod:
+event_name PE_MODIFIER_EVENT
+{
+	struct list_head *list = $1;
+	int err;
+
+	/*
+	 * Apply modifier on all events added by single event definition
+	 * (there could be more events added for multiple tracepoint
+	 * definitions via '*?'.
+	 */
+	err = parse_events__modifier_event(_parse_state, &@2, list, $2);
+	if (err)
+		YYABORT;
+	$$ = list;
+}
+|
+event_name
+
+event_name:
+PE_EVENT_NAME event_def
+{
+	/*
+	 * When an event is parsed the text is rewound and the entire text of
+	 * the event is set to the str of PE_EVENT_NAME token matched here. If
+	 * no name was on an event via a term, set the name to the entire text
+	 * taking ownership of the allocation.
+	 */
+	int err = parse_events__set_default_name($2, $1);
+
+	if (err) {
+		free_list_evsel($2);
+		YYNOMEM;
+	}
+	$$ = $2;
+}
+|
+event_def
+
+event_def: event_pmu |
+	   event_legacy_mem sep_dc |
+	   event_legacy_tracepoint sep_dc |
+	   event_legacy_numeric sep_dc |
+	   event_legacy_raw sep_dc
+
+event_pmu:
+PE_NAME opt_pmu_config
+{
+	/* List of created evsels. */
+	struct list_head *list = NULL;
+	int err = parse_events_multi_pmu_add_or_add_pmu(_parse_state, $1, $2, &list, &@1);
+
+	parse_events_terms__delete($2);
+	free($1);
+	if (err)
+		PE_ABORT(err);
+	$$ = list;
+}
+|
+PE_NAME sep_dc
+{
+	struct list_head *list;
+	int err;
+
+	err = parse_events_multi_pmu_add(_parse_state, $1, /*const_parsed_terms*/NULL, &list, &@1);
+	if (err < 0) {
+		struct parse_events_state *parse_state = _parse_state;
+		struct parse_events_error *error = parse_state->error;
+		char *help;
+
+		if (asprintf(&help, "Unable to find event on a PMU of '%s'", $1) < 0)
+			help = NULL;
+		parse_events_error__handle(error, @1.first_column, strdup("Bad event name"), help);
+		free($1);
+		PE_ABORT(err);
+	}
+	free($1);
+	$$ = list;
+}
+
+event_legacy_mem:
+PE_PREFIX_MEM PE_VALUE PE_BP_SLASH PE_VALUE PE_BP_COLON PE_MODIFIER_BP opt_event_config
+{
+	struct list_head *list;
+	int err;
+
+	list = alloc_list();
+	if (!list)
+		YYNOMEM;
+
+	err = parse_events_add_breakpoint(_parse_state, list,
+					  $2, $6, $4, $7);
+	parse_events_terms__delete($7);
+	free($6);
+	if (err) {
+		free(list);
+		PE_ABORT(err);
+	}
+	$$ = list;
+}
+|
+PE_PREFIX_MEM PE_VALUE PE_BP_SLASH PE_VALUE opt_event_config
+{
+	struct list_head *list;
+	int err;
+
+	list = alloc_list();
+	if (!list)
+		YYNOMEM;
+
+	err = parse_events_add_breakpoint(_parse_state, list,
+					  $2, NULL, $4, $5);
+	parse_events_terms__delete($5);
+	if (err) {
+		free(list);
+		PE_ABORT(err);
+	}
+	$$ = list;
+}
+|
+PE_PREFIX_MEM PE_VALUE PE_BP_COLON PE_MODIFIER_BP opt_event_config
+{
+	struct list_head *list;
+	int err;
+
+	list = alloc_list();
+	if (!list)
+		YYNOMEM;
+
+	err = parse_events_add_breakpoint(_parse_state, list,
+					  $2, $4, 0, $5);
+	parse_events_terms__delete($5);
+	free($4);
+	if (err) {
+		free(list);
+		PE_ABORT(err);
+	}
+	$$ = list;
+}
+|
+PE_PREFIX_MEM PE_VALUE opt_event_config
+{
+	struct list_head *list;
+	int err;
+
+	list = alloc_list();
+	if (!list)
+		YYNOMEM;
+	err = parse_events_add_breakpoint(_parse_state, list,
+					  $2, NULL, 0, $3);
+	parse_events_terms__delete($3);
+	if (err) {
+		free(list);
+		PE_ABORT(err);
+	}
+	$$ = list;
+}
+
+event_legacy_tracepoint:
+tracepoint_name opt_event_config
+{
+	struct parse_events_state *parse_state = _parse_state;
+	struct parse_events_error *error = parse_state->error;
+	struct list_head *list;
+	int err;
+
+	list = alloc_list();
+	if (!list)
+		YYNOMEM;
+
+	err = parse_events_add_tracepoint(parse_state, list, $1.sys, $1.event,
+					error, $2, &@1);
+
+	parse_events_terms__delete($2);
+	free($1.sys);
+	free($1.event);
+	if (err) {
+		free(list);
+		PE_ABORT(err);
+	}
+	$$ = list;
+}
+
+tracepoint_name:
+PE_NAME ':' PE_NAME
+{
+	struct tracepoint_name tracepoint = {$1, $3};
+
+	$$ = tracepoint;
+}
+
+event_legacy_numeric:
+PE_VALUE ':' PE_VALUE opt_event_config
+{
+	struct list_head *list;
+	int err;
+
+	list = alloc_list();
+	if (!list)
+		YYNOMEM;
+	err = parse_events_add_numeric(_parse_state, list, (u32)$1, $3, $4,
+				       /*wildcard=*/false);
+	parse_events_terms__delete($4);
+	if (err) {
+		free(list);
+		PE_ABORT(err);
+	}
+	$$ = list;
+}
+
+event_legacy_raw:
+PE_RAW opt_event_config
+{
+	struct list_head *list;
+	int err;
+	u64 num;
+
+	list = alloc_list();
+	if (!list)
+		YYNOMEM;
+	errno = 0;
+	num = strtoull($1 + 1, NULL, 16);
+	/* Given the lexer will only give [a-fA-F0-9]+ a failure here should be impossible. */
+	if (errno)
+		YYABORT;
+	free($1);
+	err = parse_events_add_numeric(_parse_state, list, PERF_TYPE_RAW, num, $2,
+				       /*wildcard=*/false);
+	parse_events_terms__delete($2);
+	if (err) {
+		free(list);
+		PE_ABORT(err);
+	}
+	$$ = list;
+}
+
+opt_event_config:
+'/' event_config '/'
+{
+	$$ = $2;
+}
+|
+'/' '/'
+{
+	$$ = NULL;
+}
+|
+{
+	$$ = NULL;
+}
+
+opt_pmu_config:
+'/' event_config '/'
+{
+	$$ = $2;
+}
+|
+'/' '/'
+{
+	$$ = NULL;
+}
+
+start_terms: event_config
+{
+	struct parse_events_state *parse_state = _parse_state;
+	if (parse_state->terms) {
+		parse_events_terms__delete ($1);
+		YYABORT;
+	}
+	parse_state->terms = $1;
+}
+
+event_config:
+event_config ',' event_term
+{
+	struct parse_events_terms *head = $1;
+	struct parse_events_term *term = $3;
+
+	if (!head) {
+		parse_events_term__delete(term);
+		YYABORT;
+	}
+	list_add_tail(&term->list, &head->terms);
+	$$ = $1;
+}
+|
+event_term
+{
+	struct parse_events_terms *head = malloc(sizeof(*head));
+	struct parse_events_term *term = $1;
+
+	if (!head)
+		YYNOMEM;
+	parse_events_terms__init(head);
+	list_add_tail(&term->list, &head->terms);
+	$$ = head;
+}
+
+name_or_raw: PE_RAW | PE_NAME
+
+event_term:
+PE_RAW
+{
+	struct parse_events_term *term;
+	int err = parse_events_term__str(&term, PARSE_EVENTS__TERM_TYPE_RAW,
+					 strdup("raw"), $1, &@1, &@1);
+
+	if (err) {
+		free($1);
+		PE_ABORT(err);
+	}
+	$$ = term;
+}
+|
+name_or_raw '=' name_or_raw
+{
+	struct parse_events_term *term;
+	int err = parse_events_term__str(&term, PARSE_EVENTS__TERM_TYPE_USER, $1, $3, &@1, &@3);
+
+	if (err) {
+		free($1);
+		free($3);
+		PE_ABORT(err);
+	}
+	$$ = term;
+}
+|
+name_or_raw '=' PE_VALUE
+{
+	struct parse_events_term *term;
+	int err = parse_events_term__num(&term, PARSE_EVENTS__TERM_TYPE_USER,
+					 $1, $3, /*novalue=*/false, &@1, &@3);
+
+	if (err) {
+		free($1);
+		PE_ABORT(err);
+	}
+	$$ = term;
+}
+|
+PE_NAME
+{
+	struct parse_events_term *term;
+	int err = parse_events_term__num(&term, PARSE_EVENTS__TERM_TYPE_USER,
+					 $1, /*num=*/1, /*novalue=*/true, &@1, /*loc_val=*/NULL);
+
+	if (err) {
+		free($1);
+		PE_ABORT(err);
+	}
+	$$ = term;
+}
+|
+PE_TERM '=' name_or_raw
+{
+	struct parse_events_term *term;
+	int err = parse_events_term__str(&term, $1, /*config=*/NULL, $3, &@1, &@3);
+
+	if (err) {
+		free($3);
+		PE_ABORT(err);
+	}
+	$$ = term;
+}
+|
+PE_TERM '=' PE_TERM
+{
+	struct parse_events_term *term;
+	int err = parse_events_term__term(&term, $1, $3, &@1, &@3);
+
+	if (err)
+		PE_ABORT(err);
+
+	$$ = term;
+}
+|
+PE_TERM '=' PE_VALUE
+{
+	struct parse_events_term *term;
+	int err = parse_events_term__num(&term, $1,
+					 /*config=*/NULL, $3, /*novalue=*/false,
+					 &@1, &@3);
+
+	if (err)
+		PE_ABORT(err);
+
+	$$ = term;
+}
+|
+PE_TERM
+{
+	struct parse_events_term *term;
+	int err = parse_events_term__num(&term, $1,
+					 /*config=*/NULL, /*num=*/1, /*novalue=*/true,
+					 &@1, /*loc_val=*/NULL);
+
+	if (err)
+		PE_ABORT(err);
+
+	$$ = term;
+}
+|
+PE_DRV_CFG_TERM
+{
+	struct parse_events_term *term;
+	char *config = strdup($1);
+	int err;
+
+	if (!config)
+		YYNOMEM;
+	err = parse_events_term__str(&term, PARSE_EVENTS__TERM_TYPE_DRV_CFG, config, $1, &@1, NULL);
+	if (err) {
+		free($1);
+		free(config);
+		PE_ABORT(err);
+	}
+	$$ = term;
+}
+
+sep_dc: ':' |
+
+%%
+
+void parse_events_error(YYLTYPE *loc, void *_parse_state,
+			void *scanner __maybe_unused,
+			char const *msg __maybe_unused)
+{
+	struct parse_events_state *parse_state = _parse_state;
+
+	if (!parse_state->error || !list_empty(&parse_state->error->list))
+		return;
+
+	parse_events_error__handle(parse_state->error, loc->last_column,
+				   strdup("Unrecognized input"), NULL);
+}