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, 489 insertions, 0 deletions

diff --git a/tools/perf/util/expr.c b/tools/perf/util/expr.c
new file mode 100644
index 000000000..232998fef
--- /dev/null
+++ b/tools/perf/util/expr.c
@@ -0,0 +1,489 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <stdbool.h>
+#include <assert.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include "metricgroup.h"
+#include "debug.h"
+#include "evlist.h"
+#include "expr.h"
+#include "smt.h"
+#include "tool_pmu.h"
+#include <util/expr-bison.h>
+#include <util/expr-flex.h>
+#include "util/hashmap.h"
+#include "util/header.h"
+#include "util/pmu.h"
+#include <perf/cpumap.h>
+#include <linux/err.h>
+#include <linux/kernel.h>
+#include <linux/zalloc.h>
+#include <ctype.h>
+#include <math.h>
+
+struct expr_id_data {
+	union {
+		struct {
+			double val;
+			int source_count;
+			int aggr_nr;
+		} val;
+		struct {
+			double val;
+			const char *metric_name;
+			const char *metric_expr;
+		} ref;
+	};
+
+	enum {
+		/* Holding a double value. */
+		EXPR_ID_DATA__VALUE,
+		/* Reference to another metric. */
+		EXPR_ID_DATA__REF,
+		/* A reference but the value has been computed. */
+		EXPR_ID_DATA__REF_VALUE,
+	} kind;
+};
+
+static size_t key_hash(long key, void *ctx __maybe_unused)
+{
+	const char *str = (const char *)key;
+	size_t hash = 0;
+
+	while (*str != '\0') {
+		hash *= 31;
+		hash += *str;
+		str++;
+	}
+	return hash;
+}
+
+static bool key_equal(long key1, long key2, void *ctx __maybe_unused)
+{
+	return !strcmp((const char *)key1, (const char *)key2);
+}
+
+struct hashmap *ids__new(void)
+{
+	struct hashmap *hash;
+
+	hash = hashmap__new(key_hash, key_equal, NULL);
+	if (IS_ERR(hash))
+		return NULL;
+	return hash;
+}
+
+void ids__free(struct hashmap *ids)
+{
+	struct hashmap_entry *cur;
+	size_t bkt;
+
+	if (ids == NULL)
+		return;
+
+	hashmap__for_each_entry(ids, cur, bkt) {
+		zfree(&cur->pkey);
+		zfree(&cur->pvalue);
+	}
+
+	hashmap__free(ids);
+}
+
+int ids__insert(struct hashmap *ids, const char *id)
+{
+	struct expr_id_data *data_ptr = NULL, *old_data = NULL;
+	char *old_key = NULL;
+	int ret;
+
+	ret = hashmap__set(ids, id, data_ptr, &old_key, &old_data);
+	if (ret)
+		free(data_ptr);
+	free(old_key);
+	free(old_data);
+	return ret;
+}
+
+struct hashmap *ids__union(struct hashmap *ids1, struct hashmap *ids2)
+{
+	size_t bkt;
+	struct hashmap_entry *cur;
+	int ret;
+	struct expr_id_data *old_data = NULL;
+	char *old_key = NULL;
+
+	if (!ids1)
+		return ids2;
+
+	if (!ids2)
+		return ids1;
+
+	if (hashmap__size(ids1) <  hashmap__size(ids2)) {
+		struct hashmap *tmp = ids1;
+
+		ids1 = ids2;
+		ids2 = tmp;
+	}
+	hashmap__for_each_entry(ids2, cur, bkt) {
+		ret = hashmap__set(ids1, cur->key, cur->value, &old_key, &old_data);
+		free(old_key);
+		free(old_data);
+
+		if (ret) {
+			hashmap__free(ids1);
+			hashmap__free(ids2);
+			return NULL;
+		}
+	}
+	hashmap__free(ids2);
+	return ids1;
+}
+
+/* Caller must make sure id is allocated */
+int expr__add_id(struct expr_parse_ctx *ctx, const char *id)
+{
+	return ids__insert(ctx->ids, id);
+}
+
+/* Caller must make sure id is allocated */
+int expr__add_id_val(struct expr_parse_ctx *ctx, const char *id, double val)
+{
+	return expr__add_id_val_source_count(ctx, id, val, /*source_count=*/1);
+}
+
+/* Caller must make sure id is allocated */
+int expr__add_id_val_source_count_aggr_nr(struct expr_parse_ctx *ctx, const char *id,
+					  double val, int source_count, int aggr_nr)
+{
+	struct expr_id_data *data_ptr = NULL, *old_data = NULL;
+	char *old_key = NULL;
+	int ret;
+
+	data_ptr = malloc(sizeof(*data_ptr));
+	if (!data_ptr)
+		return -ENOMEM;
+	data_ptr->val.val = val;
+	data_ptr->val.source_count = source_count;
+	data_ptr->val.aggr_nr = aggr_nr;
+	data_ptr->kind = EXPR_ID_DATA__VALUE;
+
+	ret = hashmap__set(ctx->ids, id, data_ptr, &old_key, &old_data);
+	if (ret) {
+		free(data_ptr);
+	} else if (old_data) {
+		data_ptr->val.val += old_data->val.val;
+		data_ptr->val.source_count += old_data->val.source_count;
+		data_ptr->val.aggr_nr += old_data->val.aggr_nr;
+	}
+	free(old_key);
+	free(old_data);
+	return ret;
+}
+
+/* Caller must make sure id is allocated */
+int expr__add_id_val_source_count(struct expr_parse_ctx *ctx, const char *id,
+				  double val, int source_count)
+{
+	return expr__add_id_val_source_count_aggr_nr(ctx, id, val, source_count, 1);
+}
+
+int expr__add_ref(struct expr_parse_ctx *ctx, struct metric_ref *ref)
+{
+	struct expr_id_data *data_ptr = NULL, *old_data = NULL;
+	char *old_key = NULL;
+	char *name;
+	int ret;
+
+	data_ptr = zalloc(sizeof(*data_ptr));
+	if (!data_ptr)
+		return -ENOMEM;
+
+	name = strdup(ref->metric_name);
+	if (!name) {
+		free(data_ptr);
+		return -ENOMEM;
+	}
+
+	/*
+	 * Intentionally passing just const char pointers,
+	 * originally from 'struct pmu_event' object.
+	 * We don't need to change them, so there's no
+	 * need to create our own copy.
+	 */
+	data_ptr->ref.metric_name = ref->metric_name;
+	data_ptr->ref.metric_expr = ref->metric_expr;
+	data_ptr->kind = EXPR_ID_DATA__REF;
+
+	ret = hashmap__set(ctx->ids, name, data_ptr, &old_key, &old_data);
+	if (ret)
+		free(data_ptr);
+
+	pr_debug2("adding ref metric %s: %s\n",
+		  ref->metric_name, ref->metric_expr);
+
+	free(old_key);
+	free(old_data);
+	return ret;
+}
+
+int expr__get_id(struct expr_parse_ctx *ctx, const char *id,
+		 struct expr_id_data **data)
+{
+	if (!ctx || !id)
+		return -1;
+	return hashmap__find(ctx->ids, id, data) ? 0 : -1;
+}
+
+bool expr__subset_of_ids(struct expr_parse_ctx *haystack,
+			 struct expr_parse_ctx *needles)
+{
+	struct hashmap_entry *cur;
+	size_t bkt;
+	struct expr_id_data *data;
+
+	hashmap__for_each_entry(needles->ids, cur, bkt) {
+		if (expr__get_id(haystack, cur->pkey, &data))
+			return false;
+	}
+	return true;
+}
+
+
+int expr__resolve_id(struct expr_parse_ctx *ctx, const char *id,
+		     struct expr_id_data **datap)
+{
+	struct expr_id_data *data;
+
+	if (expr__get_id(ctx, id, datap) || !*datap) {
+		pr_debug("%s not found\n", id);
+		return -1;
+	}
+
+	data = *datap;
+
+	switch (data->kind) {
+	case EXPR_ID_DATA__VALUE:
+		pr_debug2("lookup(%s): val %f\n", id, data->val.val);
+		break;
+	case EXPR_ID_DATA__REF:
+		pr_debug2("lookup(%s): ref metric name %s\n", id,
+			data->ref.metric_name);
+		pr_debug("processing metric: %s ENTRY\n", id);
+		data->kind = EXPR_ID_DATA__REF_VALUE;
+		if (expr__parse(&data->ref.val, ctx, data->ref.metric_expr)) {
+			pr_debug("%s failed to count\n", id);
+			return -1;
+		}
+		pr_debug("processing metric: %s EXIT: %f\n", id, data->ref.val);
+		break;
+	case EXPR_ID_DATA__REF_VALUE:
+		pr_debug2("lookup(%s): ref val %f metric name %s\n", id,
+			data->ref.val, data->ref.metric_name);
+		break;
+	default:
+		assert(0);  /* Unreachable. */
+	}
+
+	return 0;
+}
+
+void expr__del_id(struct expr_parse_ctx *ctx, const char *id)
+{
+	struct expr_id_data *old_val = NULL;
+	char *old_key = NULL;
+
+	hashmap__delete(ctx->ids, id, &old_key, &old_val);
+	free(old_key);
+	free(old_val);
+}
+
+struct expr_parse_ctx *expr__ctx_new(void)
+{
+	struct expr_parse_ctx *ctx;
+
+	ctx = calloc(1, sizeof(struct expr_parse_ctx));
+	if (!ctx)
+		return NULL;
+
+	ctx->ids = hashmap__new(key_hash, key_equal, NULL);
+	if (IS_ERR(ctx->ids)) {
+		free(ctx);
+		return NULL;
+	}
+
+	return ctx;
+}
+
+void expr__ctx_clear(struct expr_parse_ctx *ctx)
+{
+	struct hashmap_entry *cur;
+	size_t bkt;
+
+	hashmap__for_each_entry(ctx->ids, cur, bkt) {
+		zfree(&cur->pkey);
+		zfree(&cur->pvalue);
+	}
+	hashmap__clear(ctx->ids);
+}
+
+void expr__ctx_free(struct expr_parse_ctx *ctx)
+{
+	struct hashmap_entry *cur;
+	size_t bkt;
+
+	if (!ctx)
+		return;
+
+	zfree(&ctx->sctx.user_requested_cpu_list);
+	hashmap__for_each_entry(ctx->ids, cur, bkt) {
+		zfree(&cur->pkey);
+		zfree(&cur->pvalue);
+	}
+	hashmap__free(ctx->ids);
+	free(ctx);
+}
+
+static int
+__expr__parse(double *val, struct expr_parse_ctx *ctx, const char *expr,
+	      bool compute_ids)
+{
+	YY_BUFFER_STATE buffer;
+	void *scanner;
+	int ret;
+
+	pr_debug2("parsing metric: %s\n", expr);
+
+	ret = expr_lex_init_extra(&ctx->sctx, &scanner);
+	if (ret)
+		return ret;
+
+	buffer = expr__scan_string(expr, scanner);
+
+#ifdef PARSER_DEBUG
+	expr_debug = 1;
+	expr_set_debug(1, scanner);
+#endif
+
+	ret = expr_parse(val, ctx, compute_ids, scanner);
+
+	expr__flush_buffer(buffer, scanner);
+	expr__delete_buffer(buffer, scanner);
+	expr_lex_destroy(scanner);
+	return ret;
+}
+
+int expr__parse(double *final_val, struct expr_parse_ctx *ctx,
+		const char *expr)
+{
+	return __expr__parse(final_val, ctx, expr, /*compute_ids=*/false) ? -1 : 0;
+}
+
+int expr__find_ids(const char *expr, const char *one,
+		   struct expr_parse_ctx *ctx)
+{
+	int ret = __expr__parse(NULL, ctx, expr, /*compute_ids=*/true);
+
+	if (one)
+		expr__del_id(ctx, one);
+
+	/* A positive value means syntax error, convert to -EINVAL */
+	return ret > 0 ? -EINVAL : ret;
+}
+
+double expr_id_data__value(const struct expr_id_data *data)
+{
+	if (data->kind == EXPR_ID_DATA__VALUE)
+		return data->val.val;
+	assert(data->kind == EXPR_ID_DATA__REF_VALUE);
+	return data->ref.val;
+}
+
+double expr_id_data__source_count(const struct expr_id_data *data)
+{
+	if (data->kind == EXPR_ID_DATA__VALUE)
+		return data->val.source_count;
+	return 1.0;
+}
+
+double expr_id_data__aggr_nr(const struct expr_id_data *data)
+{
+	if (data->kind == EXPR_ID_DATA__VALUE)
+		return data->val.aggr_nr;
+	return 1.0;
+}
+
+double expr__get_literal(const char *literal, const struct expr_scanner_ctx *ctx)
+{
+	double result = NAN;
+	enum tool_pmu_event ev = tool_pmu__str_to_event(literal + 1);
+
+	if (ev != TOOL_PMU__EVENT_NONE) {
+		u64 count;
+
+		if (tool_pmu__read_event(ev, /*evsel=*/NULL,
+					 ctx->system_wide, ctx->user_requested_cpu_list,
+					 &count))
+			result = count;
+		else
+			pr_err("Failure to read '%s'\n", literal);
+	} else {
+		pr_err("Unrecognized literal '%s'\n", literal);
+	}
+
+	pr_debug2("literal: %s = %f\n", literal, result);
+	return result;
+}
+
+/* Does the event 'id' parse? Determine via ctx->ids if possible. */
+double expr__has_event(const struct expr_parse_ctx *ctx, bool compute_ids, const char *id)
+{
+	struct evlist *tmp;
+	double ret;
+
+	if (hashmap__find(ctx->ids, id, /*value=*/NULL))
+		return 1.0;
+
+	if (!compute_ids)
+		return 0.0;
+
+	tmp = evlist__new();
+	if (!tmp)
+		return NAN;
+
+	if (strchr(id, '@')) {
+		char *tmp_id, *p;
+
+		tmp_id = strdup(id);
+		if (!tmp_id) {
+			ret = NAN;
+			goto out;
+		}
+		p = strchr(tmp_id, '@');
+		*p = '/';
+		p = strrchr(tmp_id, '@');
+		*p = '/';
+		ret = parse_event(tmp, tmp_id) ? 0 : 1;
+		free(tmp_id);
+	} else {
+		ret = parse_event(tmp, id) ? 0 : 1;
+	}
+out:
+	evlist__delete(tmp);
+	return ret;
+}
+
+double expr__strcmp_cpuid_str(const struct expr_parse_ctx *ctx __maybe_unused,
+		       bool compute_ids __maybe_unused, const char *test_id)
+{
+	double ret;
+	struct perf_cpu cpu = {-1};
+	char *cpuid = get_cpuid_allow_env_override(cpu);
+
+	if (!cpuid)
+		return NAN;
+
+	ret = !strcmp_cpuid_str(test_id, cpuid);
+
+	free(cpuid);
+	return ret;
+}