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, 289 insertions, 0 deletions

diff --git a/tools/perf/util/values.c b/tools/perf/util/values.c
new file mode 100644
index 000000000..6eaddfcf8
--- /dev/null
+++ b/tools/perf/util/values.c
@@ -0,0 +1,289 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <inttypes.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <linux/zalloc.h>
+
+#include "values.h"
+#include "debug.h"
+#include "evsel.h"
+
+int perf_read_values_init(struct perf_read_values *values)
+{
+	values->threads_max = 16;
+	values->pid = calloc(values->threads_max, sizeof(*values->pid));
+	values->tid = calloc(values->threads_max, sizeof(*values->tid));
+	values->value = calloc(values->threads_max, sizeof(*values->value));
+	if (!values->pid || !values->tid || !values->value) {
+		pr_debug("failed to allocate read_values threads arrays");
+		goto out_free_pid;
+	}
+	values->threads = 0;
+
+	values->counters_max = 16;
+	values->counters = malloc(values->counters_max * sizeof(*values->counters));
+	if (!values->counters) {
+		pr_debug("failed to allocate read_values counters array");
+		goto out_free_counter;
+	}
+	values->num_counters = 0;
+
+	return 0;
+
+out_free_counter:
+	zfree(&values->counters);
+out_free_pid:
+	zfree(&values->pid);
+	zfree(&values->tid);
+	zfree(&values->value);
+	return -ENOMEM;
+}
+
+void perf_read_values_destroy(struct perf_read_values *values)
+{
+	int i;
+
+	if (!values->threads_max || !values->counters_max)
+		return;
+
+	for (i = 0; i < values->threads; i++)
+		zfree(&values->value[i]);
+	zfree(&values->value);
+	zfree(&values->pid);
+	zfree(&values->tid);
+	zfree(&values->counters);
+}
+
+static int perf_read_values__enlarge_threads(struct perf_read_values *values)
+{
+	int nthreads_max = values->threads_max * 2;
+	void *npid = realloc(values->pid, nthreads_max * sizeof(*values->pid)),
+	     *ntid = realloc(values->tid, nthreads_max * sizeof(*values->tid)),
+	     *nvalue = realloc(values->value, nthreads_max * sizeof(*values->value));
+
+	if (!npid || !ntid || !nvalue)
+		goto out_err;
+
+	values->threads_max = nthreads_max;
+	values->pid = npid;
+	values->tid = ntid;
+	values->value = nvalue;
+	return 0;
+out_err:
+	free(npid);
+	free(ntid);
+	free(nvalue);
+	pr_debug("failed to enlarge read_values threads arrays");
+	return -ENOMEM;
+}
+
+static int perf_read_values__findnew_thread(struct perf_read_values *values,
+					    u32 pid, u32 tid)
+{
+	int i;
+
+	for (i = 0; i < values->threads; i++)
+		if (values->pid[i] == pid && values->tid[i] == tid)
+			return i;
+
+	if (values->threads == values->threads_max) {
+		i = perf_read_values__enlarge_threads(values);
+		if (i < 0)
+			return i;
+	}
+
+	i = values->threads;
+
+	values->value[i] = calloc(values->counters_max, sizeof(**values->value));
+	if (!values->value[i]) {
+		pr_debug("failed to allocate read_values counters array");
+		return -ENOMEM;
+	}
+	values->pid[i] = pid;
+	values->tid[i] = tid;
+	values->threads = i + 1;
+
+	return i;
+}
+
+static int perf_read_values__enlarge_counters(struct perf_read_values *values)
+{
+	int counters_max = values->counters_max * 2;
+	struct evsel **new_counters = realloc(values->counters,
+					     counters_max * sizeof(*values->counters));
+
+	if (!new_counters) {
+		pr_debug("failed to enlarge read_values counters array");
+		goto out_enomem;
+	}
+
+	for (int i = 0; i < values->threads; i++) {
+		u64 *value = realloc(values->value[i], counters_max * sizeof(**values->value));
+
+		if (!value) {
+			pr_debug("failed to enlarge read_values ->values array");
+			goto out_free_counters;
+		}
+
+		for (int j = values->counters_max; j < counters_max; j++)
+			value[j] = 0;
+
+		values->value[i] = value;
+	}
+
+	values->counters_max = counters_max;
+	values->counters = new_counters;
+
+	return 0;
+out_free_counters:
+	free(new_counters);
+out_enomem:
+	return -ENOMEM;
+}
+
+static int perf_read_values__findnew_counter(struct perf_read_values *values,
+					     struct evsel *evsel)
+{
+	int i;
+
+	for (i = 0; i < values->num_counters; i++)
+		if (values->counters[i] == evsel)
+			return i;
+
+	if (values->num_counters == values->counters_max) {
+		int err = perf_read_values__enlarge_counters(values);
+
+		if (err)
+			return err;
+	}
+
+	i = values->num_counters++;
+	values->counters[i] = evsel;
+
+	return i;
+}
+
+int perf_read_values_add_value(struct perf_read_values *values,
+				u32 pid, u32 tid,
+				struct evsel *evsel, u64 value)
+{
+	int tindex, cindex;
+
+	tindex = perf_read_values__findnew_thread(values, pid, tid);
+	if (tindex < 0)
+		return tindex;
+	cindex = perf_read_values__findnew_counter(values, evsel);
+	if (cindex < 0)
+		return cindex;
+
+	values->value[tindex][cindex] += value;
+	return 0;
+}
+
+static void perf_read_values__display_pretty(FILE *fp,
+					     struct perf_read_values *values)
+{
+	int i, j;
+	int pidwidth, tidwidth;
+	int *counterwidth;
+
+	counterwidth = malloc(values->num_counters * sizeof(*counterwidth));
+	if (!counterwidth) {
+		fprintf(fp, "INTERNAL ERROR: Failed to allocate counterwidth array\n");
+		return;
+	}
+	tidwidth = 3;
+	pidwidth = 3;
+	for (j = 0; j < values->num_counters; j++)
+		counterwidth[j] = strlen(evsel__name(values->counters[j]));
+	for (i = 0; i < values->threads; i++) {
+		int width;
+
+		width = snprintf(NULL, 0, "%d", values->pid[i]);
+		if (width > pidwidth)
+			pidwidth = width;
+		width = snprintf(NULL, 0, "%d", values->tid[i]);
+		if (width > tidwidth)
+			tidwidth = width;
+		for (j = 0; j < values->num_counters; j++) {
+			width = snprintf(NULL, 0, "%" PRIu64, values->value[i][j]);
+			if (width > counterwidth[j])
+				counterwidth[j] = width;
+		}
+	}
+
+	fprintf(fp, "# %*s  %*s", pidwidth, "PID", tidwidth, "TID");
+	for (j = 0; j < values->num_counters; j++)
+		fprintf(fp, "  %*s", counterwidth[j], evsel__name(values->counters[j]));
+	fprintf(fp, "\n");
+
+	for (i = 0; i < values->threads; i++) {
+		fprintf(fp, "  %*d  %*d", pidwidth, values->pid[i],
+			tidwidth, values->tid[i]);
+		for (j = 0; j < values->num_counters; j++)
+			fprintf(fp, "  %*" PRIu64,
+				counterwidth[j], values->value[i][j]);
+		fprintf(fp, "\n");
+	}
+	free(counterwidth);
+}
+
+static void perf_read_values__display_raw(FILE *fp,
+					  struct perf_read_values *values)
+{
+	int width, pidwidth, tidwidth, namewidth, rawwidth, countwidth;
+	int i, j;
+
+	tidwidth = 3; /* TID */
+	pidwidth = 3; /* PID */
+	namewidth = 4; /* "Name" */
+	rawwidth = 3; /* "Raw" */
+	countwidth = 5; /* "Count" */
+
+	for (i = 0; i < values->threads; i++) {
+		width = snprintf(NULL, 0, "%d", values->pid[i]);
+		if (width > pidwidth)
+			pidwidth = width;
+		width = snprintf(NULL, 0, "%d", values->tid[i]);
+		if (width > tidwidth)
+			tidwidth = width;
+	}
+	for (j = 0; j < values->num_counters; j++) {
+		width = strlen(evsel__name(values->counters[j]));
+		if (width > namewidth)
+			namewidth = width;
+		width = snprintf(NULL, 0, "%x", values->counters[j]->core.idx);
+		if (width > rawwidth)
+			rawwidth = width;
+	}
+	for (i = 0; i < values->threads; i++) {
+		for (j = 0; j < values->num_counters; j++) {
+			width = snprintf(NULL, 0, "%" PRIu64, values->value[i][j]);
+			if (width > countwidth)
+				countwidth = width;
+		}
+	}
+
+	fprintf(fp, "# %*s  %*s  %*s  %*s  %*s\n",
+		pidwidth, "PID", tidwidth, "TID",
+		namewidth, "Name", rawwidth, "Raw",
+		countwidth, "Count");
+	for (i = 0; i < values->threads; i++)
+		for (j = 0; j < values->num_counters; j++)
+			fprintf(fp, "  %*d  %*d  %*s  %*x  %*" PRIu64,
+				pidwidth, values->pid[i],
+				tidwidth, values->tid[i],
+				namewidth, evsel__name(values->counters[j]),
+				rawwidth, values->counters[j]->core.idx,
+				countwidth, values->value[i][j]);
+}
+
+void perf_read_values_display(FILE *fp, struct perf_read_values *values, int raw)
+{
+	if (raw)
+		perf_read_values__display_raw(fp, values);
+	else
+		perf_read_values__display_pretty(fp, values);
+}