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, 298 insertions, 0 deletions

diff --git a/tools/perf/tests/expr.c b/tools/perf/tests/expr.c
new file mode 100644
index 000000000..726cf8d4d
--- /dev/null
+++ b/tools/perf/tests/expr.c
@@ -0,0 +1,298 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "util/cputopo.h"
+#include "util/debug.h"
+#include "util/expr.h"
+#include "util/hashmap.h"
+#include "util/header.h"
+#include "util/smt.h"
+#include "tests.h"
+#include <perf/cpumap.h>
+#include <math.h>
+#include <stdlib.h>
+#include <string.h>
+#include <string2.h>
+#include <linux/zalloc.h>
+
+static int test_ids_union(void)
+{
+	struct hashmap *ids1, *ids2;
+
+	/* Empty union. */
+	ids1 = ids__new();
+	TEST_ASSERT_VAL("ids__new", ids1);
+	ids2 = ids__new();
+	TEST_ASSERT_VAL("ids__new", ids2);
+
+	ids1 = ids__union(ids1, ids2);
+	TEST_ASSERT_EQUAL("union", (int)hashmap__size(ids1), 0);
+
+	/* Union {foo, bar} against {}. */
+	ids2 = ids__new();
+	TEST_ASSERT_VAL("ids__new", ids2);
+
+	TEST_ASSERT_EQUAL("ids__insert", ids__insert(ids1, strdup("foo")), 0);
+	TEST_ASSERT_EQUAL("ids__insert", ids__insert(ids1, strdup("bar")), 0);
+
+	ids1 = ids__union(ids1, ids2);
+	TEST_ASSERT_EQUAL("union", (int)hashmap__size(ids1), 2);
+
+	/* Union {foo, bar} against {foo}. */
+	ids2 = ids__new();
+	TEST_ASSERT_VAL("ids__new", ids2);
+	TEST_ASSERT_EQUAL("ids__insert", ids__insert(ids2, strdup("foo")), 0);
+
+	ids1 = ids__union(ids1, ids2);
+	TEST_ASSERT_EQUAL("union", (int)hashmap__size(ids1), 2);
+
+	/* Union {foo, bar} against {bar,baz}. */
+	ids2 = ids__new();
+	TEST_ASSERT_VAL("ids__new", ids2);
+	TEST_ASSERT_EQUAL("ids__insert", ids__insert(ids2, strdup("bar")), 0);
+	TEST_ASSERT_EQUAL("ids__insert", ids__insert(ids2, strdup("baz")), 0);
+
+	ids1 = ids__union(ids1, ids2);
+	TEST_ASSERT_EQUAL("union", (int)hashmap__size(ids1), 3);
+
+	ids__free(ids1);
+
+	return 0;
+}
+
+static int test(struct expr_parse_ctx *ctx, const char *e, double val2)
+{
+	double val;
+
+	if (expr__parse(&val, ctx, e))
+		TEST_ASSERT_VAL("parse test failed", 0);
+	TEST_ASSERT_VAL("unexpected value", val == val2);
+	return 0;
+}
+
+static int test__expr(struct test_suite *t __maybe_unused, int subtest __maybe_unused)
+{
+	struct expr_id_data *val_ptr;
+	const char *p;
+	double val, num_cpus_online, num_cpus, num_cores, num_dies, num_packages;
+	int ret;
+	struct expr_parse_ctx *ctx;
+	char strcmp_cpuid_buf[256];
+	struct perf_cpu cpu = {-1};
+	char *cpuid = get_cpuid_allow_env_override(cpu);
+	char *escaped_cpuid1, *escaped_cpuid2;
+
+	TEST_ASSERT_VAL("get_cpuid", cpuid);
+
+	TEST_ASSERT_EQUAL("ids_union", test_ids_union(), 0);
+
+	ctx = expr__ctx_new();
+	TEST_ASSERT_VAL("expr__ctx_new", ctx);
+	expr__add_id_val(ctx, strdup("FOO"), 1);
+	expr__add_id_val(ctx, strdup("BAR"), 2);
+
+	ret = test(ctx, "1+1", 2);
+	ret |= test(ctx, "FOO+BAR", 3);
+	ret |= test(ctx, "(BAR/2)%2", 1);
+	ret |= test(ctx, "1 - -4",  5);
+	ret |= test(ctx, "(FOO-1)*2 + (BAR/2)%2 - -4",  5);
+	ret |= test(ctx, "1-1 | 1", 1);
+	ret |= test(ctx, "1-1 & 1", 0);
+	ret |= test(ctx, "min(1,2) + 1", 2);
+	ret |= test(ctx, "max(1,2) + 1", 3);
+	ret |= test(ctx, "1+1 if 3*4 else 0", 2);
+	ret |= test(ctx, "100 if 1 else 200 if 1 else 300", 100);
+	ret |= test(ctx, "100 if 0 else 200 if 1 else 300", 200);
+	ret |= test(ctx, "100 if 1 else 200 if 0 else 300", 100);
+	ret |= test(ctx, "100 if 0 else 200 if 0 else 300", 300);
+	ret |= test(ctx, "1.1 + 2.1", 3.2);
+	ret |= test(ctx, ".1 + 2.", 2.1);
+	ret |= test(ctx, "d_ratio(1, 2)", 0.5);
+	ret |= test(ctx, "d_ratio(2.5, 0)", 0);
+	ret |= test(ctx, "1.1 < 2.2", 1);
+	ret |= test(ctx, "2.2 > 1.1", 1);
+	ret |= test(ctx, "1.1 < 1.1", 0);
+	ret |= test(ctx, "2.2 > 2.2", 0);
+	ret |= test(ctx, "2.2 < 1.1", 0);
+	ret |= test(ctx, "1.1 > 2.2", 0);
+	ret |= test(ctx, "1.1e10 < 1.1e100", 1);
+	ret |= test(ctx, "1.1e2 > 1.1e-2", 1);
+
+	if (ret) {
+		expr__ctx_free(ctx);
+		return ret;
+	}
+
+	p = "FOO/0";
+	ret = expr__parse(&val, ctx, p);
+	TEST_ASSERT_VAL("division by zero", ret == 0);
+	TEST_ASSERT_VAL("division by zero", isnan(val));
+
+	p = "BAR/";
+	ret = expr__parse(&val, ctx, p);
+	TEST_ASSERT_VAL("missing operand", ret == -1);
+
+	expr__ctx_clear(ctx);
+	TEST_ASSERT_VAL("find ids",
+			expr__find_ids("FOO + BAR + BAZ + BOZO", "FOO",
+					ctx) == 0);
+	TEST_ASSERT_VAL("find ids", hashmap__size(ctx->ids) == 3);
+	TEST_ASSERT_VAL("find ids", hashmap__find(ctx->ids, "BAR", &val_ptr));
+	TEST_ASSERT_VAL("find ids", hashmap__find(ctx->ids, "BAZ", &val_ptr));
+	TEST_ASSERT_VAL("find ids", hashmap__find(ctx->ids, "BOZO", &val_ptr));
+
+	expr__ctx_clear(ctx);
+	ctx->sctx.runtime = 3;
+	TEST_ASSERT_VAL("find ids",
+			expr__find_ids("EVENT1\\,param\\=?@ + EVENT2\\,param\\=?@",
+					NULL, ctx) == 0);
+	TEST_ASSERT_VAL("find ids", hashmap__size(ctx->ids) == 2);
+	TEST_ASSERT_VAL("find ids", hashmap__find(ctx->ids, "EVENT1,param=3@", &val_ptr));
+	TEST_ASSERT_VAL("find ids", hashmap__find(ctx->ids, "EVENT2,param=3@", &val_ptr));
+
+	expr__ctx_clear(ctx);
+	TEST_ASSERT_VAL("find ids",
+			expr__find_ids("dash\\-event1 - dash\\-event2",
+				       NULL, ctx) == 0);
+	TEST_ASSERT_VAL("find ids", hashmap__size(ctx->ids) == 2);
+	TEST_ASSERT_VAL("find ids", hashmap__find(ctx->ids, "dash-event1", &val_ptr));
+	TEST_ASSERT_VAL("find ids", hashmap__find(ctx->ids, "dash-event2", &val_ptr));
+
+	/* Only EVENT1 or EVENT2 need be measured depending on the value of smt_on. */
+	{
+		bool smton = smt_on();
+		bool corewide = core_wide(/*system_wide=*/false,
+					  /*user_requested_cpus=*/false);
+
+		expr__ctx_clear(ctx);
+		TEST_ASSERT_VAL("find ids",
+				expr__find_ids("EVENT1 if #smt_on else EVENT2",
+					NULL, ctx) == 0);
+		TEST_ASSERT_VAL("find ids", hashmap__size(ctx->ids) == 1);
+		TEST_ASSERT_VAL("find ids", hashmap__find(ctx->ids,
+							  smton ? "EVENT1" : "EVENT2",
+							  &val_ptr));
+
+		expr__ctx_clear(ctx);
+		TEST_ASSERT_VAL("find ids",
+				expr__find_ids("EVENT1 if #core_wide else EVENT2",
+					NULL, ctx) == 0);
+		TEST_ASSERT_VAL("find ids", hashmap__size(ctx->ids) == 1);
+		TEST_ASSERT_VAL("find ids", hashmap__find(ctx->ids,
+							  corewide ? "EVENT1" : "EVENT2",
+							  &val_ptr));
+
+	}
+	/* The expression is a constant 1.0 without needing to evaluate EVENT1. */
+	expr__ctx_clear(ctx);
+	TEST_ASSERT_VAL("find ids",
+			expr__find_ids("1.0 if EVENT1 > 100.0 else 1.0",
+			NULL, ctx) == 0);
+	TEST_ASSERT_VAL("find ids", hashmap__size(ctx->ids) == 0);
+
+	/* The expression is a constant 0.0 without needing to evaluate EVENT1. */
+	expr__ctx_clear(ctx);
+	TEST_ASSERT_VAL("find ids",
+			expr__find_ids("0 & EVENT1 > 0", NULL, ctx) == 0);
+	TEST_ASSERT_VAL("find ids", hashmap__size(ctx->ids) == 0);
+	expr__ctx_clear(ctx);
+	TEST_ASSERT_VAL("find ids",
+			expr__find_ids("EVENT1 > 0 & 0", NULL, ctx) == 0);
+	TEST_ASSERT_VAL("find ids", hashmap__size(ctx->ids) == 0);
+	expr__ctx_clear(ctx);
+	TEST_ASSERT_VAL("find ids",
+			expr__find_ids("1 & EVENT1 > 0", NULL, ctx) == 0);
+	TEST_ASSERT_VAL("find ids", hashmap__size(ctx->ids) == 1);
+	TEST_ASSERT_VAL("find ids", hashmap__find(ctx->ids, "EVENT1", &val_ptr));
+	expr__ctx_clear(ctx);
+	TEST_ASSERT_VAL("find ids",
+			expr__find_ids("EVENT1 > 0 & 1", NULL, ctx) == 0);
+	TEST_ASSERT_VAL("find ids", hashmap__size(ctx->ids) == 1);
+	TEST_ASSERT_VAL("find ids", hashmap__find(ctx->ids, "EVENT1", &val_ptr));
+
+	/* The expression is a constant 1.0 without needing to evaluate EVENT1. */
+	expr__ctx_clear(ctx);
+	TEST_ASSERT_VAL("find ids",
+			expr__find_ids("1 | EVENT1 > 0", NULL, ctx) == 0);
+	TEST_ASSERT_VAL("find ids", hashmap__size(ctx->ids) == 0);
+	expr__ctx_clear(ctx);
+	TEST_ASSERT_VAL("find ids",
+			expr__find_ids("EVENT1 > 0 | 1", NULL, ctx) == 0);
+	TEST_ASSERT_VAL("find ids", hashmap__size(ctx->ids) == 0);
+	expr__ctx_clear(ctx);
+	TEST_ASSERT_VAL("find ids",
+			expr__find_ids("0 | EVENT1 > 0", NULL, ctx) == 0);
+	TEST_ASSERT_VAL("find ids", hashmap__size(ctx->ids) == 1);
+	TEST_ASSERT_VAL("find ids", hashmap__find(ctx->ids, "EVENT1", &val_ptr));
+	expr__ctx_clear(ctx);
+	TEST_ASSERT_VAL("find ids",
+			expr__find_ids("EVENT1 > 0 | 0", NULL, ctx) == 0);
+	TEST_ASSERT_VAL("find ids", hashmap__size(ctx->ids) == 1);
+	TEST_ASSERT_VAL("find ids", hashmap__find(ctx->ids, "EVENT1", &val_ptr));
+
+	/* Test toplogy constants appear well ordered. */
+	expr__ctx_clear(ctx);
+	TEST_ASSERT_VAL("#num_cpus_online",
+			expr__parse(&num_cpus_online, ctx, "#num_cpus_online") == 0);
+	TEST_ASSERT_VAL("#num_cpus", expr__parse(&num_cpus, ctx, "#num_cpus") == 0);
+	TEST_ASSERT_VAL("#num_cpus >= #num_cpus_online", num_cpus >= num_cpus_online);
+	TEST_ASSERT_VAL("#num_cores", expr__parse(&num_cores, ctx, "#num_cores") == 0);
+	TEST_ASSERT_VAL("#num_cpus >= #num_cores", num_cpus >= num_cores);
+	TEST_ASSERT_VAL("#num_dies", expr__parse(&num_dies, ctx, "#num_dies") == 0);
+	TEST_ASSERT_VAL("#num_cores >= #num_dies", num_cores >= num_dies);
+	TEST_ASSERT_VAL("#num_packages", expr__parse(&num_packages, ctx, "#num_packages") == 0);
+
+	if (num_dies) // Some platforms do not have CPU die support, for example s390
+		TEST_ASSERT_VAL("#num_dies >= #num_packages", num_dies >= num_packages);
+
+
+	if (expr__parse(&val, ctx, "#system_tsc_freq") == 0) {
+		bool is_intel = strstr(cpuid, "Intel") != NULL;
+
+		if (is_intel)
+			TEST_ASSERT_VAL("#system_tsc_freq > 0", val > 0);
+		else
+			TEST_ASSERT_VAL("#system_tsc_freq == 0", fpclassify(val) == FP_ZERO);
+	} else {
+#if defined(__i386__) || defined(__x86_64__)
+		TEST_ASSERT_VAL("#system_tsc_freq unsupported", 0);
+#endif
+	}
+	/*
+	 * Source count returns the number of events aggregating in a leader
+	 * event including the leader. Check parsing yields an id.
+	 */
+	expr__ctx_clear(ctx);
+	TEST_ASSERT_VAL("source count",
+			expr__find_ids("source_count(EVENT1)",
+			NULL, ctx) == 0);
+	TEST_ASSERT_VAL("source count", hashmap__size(ctx->ids) == 1);
+	TEST_ASSERT_VAL("source count", hashmap__find(ctx->ids, "EVENT1", &val_ptr));
+
+
+	/* Test no cpuid match */
+	ret = test(ctx, "strcmp_cpuid_str(0x0)", 0);
+
+	/*
+	 * Test cpuid match with current cpuid. Special chars have to be
+	 * escaped.
+	 */
+	escaped_cpuid1 = strreplace_chars('-', cpuid, "\\-");
+	free(cpuid);
+	escaped_cpuid2 = strreplace_chars(',', escaped_cpuid1, "\\,");
+	free(escaped_cpuid1);
+	escaped_cpuid1 = strreplace_chars('=', escaped_cpuid2, "\\=");
+	free(escaped_cpuid2);
+	scnprintf(strcmp_cpuid_buf, sizeof(strcmp_cpuid_buf),
+		  "strcmp_cpuid_str(%s)", escaped_cpuid1);
+	free(escaped_cpuid1);
+	ret |= test(ctx, strcmp_cpuid_buf, 1);
+
+	/* has_event returns 1 when an event exists. */
+	expr__add_id_val(ctx, strdup("cycles"), 2);
+	ret |= test(ctx, "has_event(cycles)", 1);
+
+	expr__ctx_free(ctx);
+
+	return ret;
+}
+
+DEFINE_SUITE("Simple expression parser", expr);