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, 461 insertions, 0 deletions

diff --git a/tools/perf/tests/sample-parsing.c b/tools/perf/tests/sample-parsing.c
new file mode 100644
index 000000000..55f0b73ca
--- /dev/null
+++ b/tools/perf/tests/sample-parsing.c
@@ -0,0 +1,461 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <stdbool.h>
+#include <inttypes.h>
+#include <stdlib.h>
+#include <string.h>
+#include <linux/bitops.h>
+#include <linux/kernel.h>
+#include <linux/types.h>
+
+#include "map_symbol.h"
+#include "branch.h"
+#include "event.h"
+#include "evsel.h"
+#include "debug.h"
+#include "util/synthetic-events.h"
+#include "util/util.h"
+
+#include "tests.h"
+
+#define COMP(m) do {					\
+	if (s1->m != s2->m) {				\
+		pr_debug("Samples differ at '"#m"'\n");	\
+		return false;				\
+	}						\
+} while (0)
+
+#define MCOMP(m) do {					\
+	if (memcmp(&s1->m, &s2->m, sizeof(s1->m))) {	\
+		pr_debug("Samples differ at '"#m"'\n");	\
+		return false;				\
+	}						\
+} while (0)
+
+/*
+ * Hardcode the expected values for branch_entry flags.
+ * These are based on the input value (213) specified
+ * in branch_stack variable.
+ */
+#define BS_EXPECTED_BE	0xa000d00000000000
+#define BS_EXPECTED_LE	0x1aa00000000
+#define FLAG(s)	s->branch_stack->entries[i].flags
+
+static bool samples_same(struct perf_sample *s1,
+			 struct perf_sample *s2,
+			 u64 type, u64 read_format, bool needs_swap)
+{
+	size_t i;
+
+	if (type & PERF_SAMPLE_IDENTIFIER)
+		COMP(id);
+
+	if (type & PERF_SAMPLE_IP)
+		COMP(ip);
+
+	if (type & PERF_SAMPLE_TID) {
+		COMP(pid);
+		COMP(tid);
+	}
+
+	if (type & PERF_SAMPLE_TIME)
+		COMP(time);
+
+	if (type & PERF_SAMPLE_ADDR)
+		COMP(addr);
+
+	if (type & PERF_SAMPLE_ID)
+		COMP(id);
+
+	if (type & PERF_SAMPLE_STREAM_ID)
+		COMP(stream_id);
+
+	if (type & PERF_SAMPLE_CPU)
+		COMP(cpu);
+
+	if (type & PERF_SAMPLE_PERIOD)
+		COMP(period);
+
+	if (type & PERF_SAMPLE_READ) {
+		if (read_format & PERF_FORMAT_GROUP)
+			COMP(read.group.nr);
+		else
+			COMP(read.one.value);
+		if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
+			COMP(read.time_enabled);
+		if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
+			COMP(read.time_running);
+		/* PERF_FORMAT_ID is forced for PERF_SAMPLE_READ */
+		if (read_format & PERF_FORMAT_GROUP) {
+			for (i = 0; i < s1->read.group.nr; i++) {
+				/* FIXME: check values without LOST */
+				if (read_format & PERF_FORMAT_LOST)
+					MCOMP(read.group.values[i]);
+			}
+		} else {
+			COMP(read.one.id);
+			if (read_format & PERF_FORMAT_LOST)
+				COMP(read.one.lost);
+		}
+	}
+
+	if (type & PERF_SAMPLE_CALLCHAIN) {
+		COMP(callchain->nr);
+		for (i = 0; i < s1->callchain->nr; i++)
+			COMP(callchain->ips[i]);
+	}
+
+	if (type & PERF_SAMPLE_RAW) {
+		COMP(raw_size);
+		if (memcmp(s1->raw_data, s2->raw_data, s1->raw_size)) {
+			pr_debug("Samples differ at 'raw_data'\n");
+			return false;
+		}
+	}
+
+	if (type & PERF_SAMPLE_BRANCH_STACK) {
+		COMP(branch_stack->nr);
+		COMP(branch_stack->hw_idx);
+		for (i = 0; i < s1->branch_stack->nr; i++) {
+			if (needs_swap)
+				return ((host_is_bigendian()) ?
+					(FLAG(s2).value == BS_EXPECTED_BE) :
+					(FLAG(s2).value == BS_EXPECTED_LE));
+			else
+				MCOMP(branch_stack->entries[i]);
+		}
+	}
+
+	if (type & PERF_SAMPLE_REGS_USER) {
+		struct regs_dump *s1_regs = perf_sample__user_regs(s1);
+		struct regs_dump *s2_regs = perf_sample__user_regs(s2);
+		size_t sz = hweight_long(s1_regs->mask) * sizeof(u64);
+
+		COMP(user_regs->mask);
+		COMP(user_regs->abi);
+		if (s1_regs->abi &&
+		    (!s1_regs->regs || !s2_regs->regs ||
+		     memcmp(s1_regs->regs, s2_regs->regs, sz))) {
+			pr_debug("Samples differ at 'user_regs'\n");
+			return false;
+		}
+	}
+
+	if (type & PERF_SAMPLE_STACK_USER) {
+		COMP(user_stack.size);
+		if (memcmp(s1->user_stack.data, s2->user_stack.data,
+			   s1->user_stack.size)) {
+			pr_debug("Samples differ at 'user_stack'\n");
+			return false;
+		}
+	}
+
+	if (type & PERF_SAMPLE_WEIGHT)
+		COMP(weight);
+
+	if (type & PERF_SAMPLE_WEIGHT_STRUCT) {
+		COMP(weight);
+		COMP(ins_lat);
+		COMP(weight3);
+	}
+
+	if (type & PERF_SAMPLE_DATA_SRC)
+		COMP(data_src);
+
+	if (type & PERF_SAMPLE_TRANSACTION)
+		COMP(transaction);
+
+	if (type & PERF_SAMPLE_REGS_INTR) {
+		struct regs_dump *s1_regs = perf_sample__intr_regs(s1);
+		struct regs_dump *s2_regs = perf_sample__intr_regs(s2);
+		size_t sz = hweight_long(s1_regs->mask) * sizeof(u64);
+
+		COMP(intr_regs->mask);
+		COMP(intr_regs->abi);
+		if (s1_regs->abi &&
+		    (!s1_regs->regs || !s2_regs->regs ||
+		     memcmp(s1_regs->regs, s2_regs->regs, sz))) {
+			pr_debug("Samples differ at 'intr_regs'\n");
+			return false;
+		}
+	}
+
+	if (type & PERF_SAMPLE_PHYS_ADDR)
+		COMP(phys_addr);
+
+	if (type & PERF_SAMPLE_CGROUP)
+		COMP(cgroup);
+
+	if (type & PERF_SAMPLE_DATA_PAGE_SIZE)
+		COMP(data_page_size);
+
+	if (type & PERF_SAMPLE_CODE_PAGE_SIZE)
+		COMP(code_page_size);
+
+	if (type & PERF_SAMPLE_AUX) {
+		COMP(aux_sample.size);
+		if (memcmp(s1->aux_sample.data, s2->aux_sample.data,
+			   s1->aux_sample.size)) {
+			pr_debug("Samples differ at 'aux_sample'\n");
+			return false;
+		}
+	}
+
+	return true;
+}
+
+static int do_test(u64 sample_type, u64 sample_regs, u64 read_format)
+{
+	struct evsel evsel = {
+		.needs_swap = false,
+		.core = {
+			. attr = {
+				.sample_type = sample_type,
+				.read_format = read_format,
+			},
+		},
+	};
+	union perf_event *event;
+	union {
+		struct ip_callchain callchain;
+		u64 data[64];
+	} callchain = {
+		/* 3 ips */
+		.data = {3, 201, 202, 203},
+	};
+	union {
+		struct branch_stack branch_stack;
+		u64 data[64];
+	} branch_stack = {
+		/* 1 branch_entry */
+		.data = {1, -1ULL, 211, 212, 213},
+	};
+	u64 regs[64];
+	const u32 raw_data[] = {0x12345678, 0x0a0b0c0d, 0x11020304, 0x05060708, 0 };
+	const u64 data[] = {0x2211443366558877ULL, 0, 0xaabbccddeeff4321ULL};
+	const u64 aux_data[] = {0xa55a, 0, 0xeeddee, 0x0282028202820282};
+	struct regs_dump user_regs = {
+		.abi	= PERF_SAMPLE_REGS_ABI_64,
+		.mask	= sample_regs,
+		.regs	= regs,
+	};
+	struct regs_dump intr_regs = {
+		.abi	= PERF_SAMPLE_REGS_ABI_64,
+		.mask	= sample_regs,
+		.regs	= regs,
+	};
+	struct perf_sample sample = {
+		.ip		= 101,
+		.pid		= 102,
+		.tid		= 103,
+		.time		= 104,
+		.addr		= 105,
+		.id		= 106,
+		.stream_id	= 107,
+		.period		= 108,
+		.weight		= 109,
+		.cpu		= 110,
+		.raw_size	= sizeof(raw_data),
+		.data_src	= 111,
+		.transaction	= 112,
+		.raw_data	= (void *)raw_data,
+		.callchain	= &callchain.callchain,
+		.no_hw_idx      = false,
+		.branch_stack	= &branch_stack.branch_stack,
+		.user_regs	= &user_regs,
+		.user_stack	= {
+			.size	= sizeof(data),
+			.data	= (void *)data,
+		},
+		.read		= {
+			.time_enabled = 0x030a59d664fca7deULL,
+			.time_running = 0x011b6ae553eb98edULL,
+		},
+		.intr_regs	= &intr_regs,
+		.phys_addr	= 113,
+		.cgroup		= 114,
+		.data_page_size = 115,
+		.code_page_size = 116,
+		.ins_lat	= 117,
+		.weight3	= 118,
+		.aux_sample	= {
+			.size	= sizeof(aux_data),
+			.data	= (void *)aux_data,
+		},
+	};
+	struct sample_read_value values[] = {{1, 5, 0}, {9, 3, 0}, {2, 7, 0}, {6, 4, 1},};
+	struct perf_sample sample_out, sample_out_endian;
+	size_t i, sz, bufsz;
+	int err, ret = -1;
+
+	perf_sample__init(&sample_out, /*all=*/false);
+	perf_sample__init(&sample_out_endian, /*all=*/false);
+	if (sample_type & PERF_SAMPLE_REGS_USER)
+		evsel.core.attr.sample_regs_user = sample_regs;
+
+	if (sample_type & PERF_SAMPLE_REGS_INTR)
+		evsel.core.attr.sample_regs_intr = sample_regs;
+
+	if (sample_type & PERF_SAMPLE_BRANCH_STACK)
+		evsel.core.attr.branch_sample_type |= PERF_SAMPLE_BRANCH_HW_INDEX;
+
+	for (i = 0; i < sizeof(regs); i++)
+		*(i + (u8 *)regs) = i & 0xfe;
+
+	if (read_format & PERF_FORMAT_GROUP) {
+		sample.read.group.nr     = 4;
+		sample.read.group.values = values;
+	} else {
+		sample.read.one.value = 0x08789faeb786aa87ULL;
+		sample.read.one.id    = 99;
+		sample.read.one.lost  = 1;
+	}
+
+	sz = perf_event__sample_event_size(&sample, sample_type, read_format,
+					   evsel.core.attr.branch_sample_type);
+	bufsz = sz + 4096; /* Add a bit for overrun checking */
+	event = malloc(bufsz);
+	if (!event) {
+		pr_debug("malloc failed\n");
+		return -1;
+	}
+
+	memset(event, 0xff, bufsz);
+	event->header.type = PERF_RECORD_SAMPLE;
+	event->header.misc = 0;
+	event->header.size = sz;
+
+	err = perf_event__synthesize_sample(event, sample_type, read_format,
+					    evsel.core.attr.branch_sample_type, &sample);
+	if (err) {
+		pr_debug("%s failed for sample_type %#"PRIx64", error %d\n",
+			 "perf_event__synthesize_sample", sample_type, err);
+		goto out_free;
+	}
+
+	/* The data does not contain 0xff so we use that to check the size */
+	for (i = bufsz; i > 0; i--) {
+		if (*(i - 1 + (u8 *)event) != 0xff)
+			break;
+	}
+	if (i != sz) {
+		pr_debug("Event size mismatch: actual %zu vs expected %zu\n",
+			 i, sz);
+		goto out_free;
+	}
+
+	evsel.sample_size = __evsel__sample_size(sample_type);
+
+	err = evsel__parse_sample(&evsel, event, &sample_out);
+	if (err) {
+		pr_debug("%s failed for sample_type %#"PRIx64", error %d\n",
+			 "evsel__parse_sample", sample_type, err);
+		goto out_free;
+	}
+
+	if (!samples_same(&sample, &sample_out, sample_type, read_format, evsel.needs_swap)) {
+		pr_debug("parsing failed for sample_type %#"PRIx64"\n",
+			 sample_type);
+		goto out_free;
+	}
+
+	if (sample_type == PERF_SAMPLE_BRANCH_STACK) {
+		evsel.needs_swap = true;
+		evsel.sample_size = __evsel__sample_size(sample_type);
+		err = evsel__parse_sample(&evsel, event, &sample_out_endian);
+		if (err) {
+			pr_debug("%s failed for sample_type %#"PRIx64", error %d\n",
+				 "evsel__parse_sample", sample_type, err);
+			goto out_free;
+		}
+
+		if (!samples_same(&sample, &sample_out_endian, sample_type, read_format, evsel.needs_swap)) {
+			pr_debug("parsing failed for sample_type %#"PRIx64"\n",
+				 sample_type);
+			goto out_free;
+		}
+	}
+
+	ret = 0;
+out_free:
+	free(event);
+	perf_sample__exit(&sample_out_endian);
+	perf_sample__exit(&sample_out);
+	if (ret && read_format)
+		pr_debug("read_format %#"PRIx64"\n", read_format);
+	return ret;
+}
+
+/**
+ * test__sample_parsing - test sample parsing.
+ *
+ * This function implements a test that synthesizes a sample event, parses it
+ * and then checks that the parsed sample matches the original sample.  The test
+ * checks sample format bits separately and together.  If the test passes %0 is
+ * returned, otherwise %-1 is returned.
+ */
+static int test__sample_parsing(struct test_suite *test __maybe_unused, int subtest __maybe_unused)
+{
+	const u64 rf[] = {4, 5, 6, 7, 12, 13, 14, 15, 20, 21, 22, 28, 29, 30, 31};
+	u64 sample_type;
+	u64 sample_regs;
+	size_t i;
+	int err;
+
+	/*
+	 * Fail the test if it has not been updated when new sample format bits
+	 * were added.  Please actually update the test rather than just change
+	 * the condition below.
+	 */
+	if (PERF_SAMPLE_MAX > PERF_SAMPLE_WEIGHT_STRUCT << 1) {
+		pr_debug("sample format has changed, some new PERF_SAMPLE_ bit was introduced - test needs updating\n");
+		return -1;
+	}
+
+	/* Test each sample format bit separately */
+	for (sample_type = 1; sample_type != PERF_SAMPLE_MAX;
+	     sample_type <<= 1) {
+		/* Test read_format variations */
+		if (sample_type == PERF_SAMPLE_READ) {
+			for (i = 0; i < ARRAY_SIZE(rf); i++) {
+				err = do_test(sample_type, 0, rf[i]);
+				if (err)
+					return err;
+			}
+			continue;
+		}
+		sample_regs = 0;
+
+		if (sample_type == PERF_SAMPLE_REGS_USER)
+			sample_regs = 0x3fff;
+
+		if (sample_type == PERF_SAMPLE_REGS_INTR)
+			sample_regs = 0xff0fff;
+
+		err = do_test(sample_type, sample_regs, 0);
+		if (err)
+			return err;
+	}
+
+	/*
+	 * Test all sample format bits together
+	 * Note: PERF_SAMPLE_WEIGHT and PERF_SAMPLE_WEIGHT_STRUCT cannot
+	 *       be set simultaneously.
+	 */
+	sample_type = (PERF_SAMPLE_MAX - 1) & ~PERF_SAMPLE_WEIGHT;
+	sample_regs = 0x3fff; /* shared yb intr and user regs */
+	for (i = 0; i < ARRAY_SIZE(rf); i++) {
+		err = do_test(sample_type, sample_regs, rf[i]);
+		if (err)
+			return err;
+	}
+	sample_type = (PERF_SAMPLE_MAX - 1) & ~PERF_SAMPLE_WEIGHT_STRUCT;
+	for (i = 0; i < ARRAY_SIZE(rf); i++) {
+		err = do_test(sample_type, sample_regs, rf[i]);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
+DEFINE_SUITE("Sample parsing", sample_parsing);