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, 118 insertions, 0 deletions

diff --git a/tools/perf/builtin-data.c b/tools/perf/builtin-data.c
new file mode 100644
index 000000000..1dd73ed6b
--- /dev/null
+++ b/tools/perf/builtin-data.c
@@ -0,0 +1,118 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/compiler.h>
+#include <stdio.h>
+#include <string.h>
+#include "builtin.h"
+#include "debug.h"
+#include <subcmd/parse-options.h>
+#include "data-convert.h"
+#include "util/util.h"
+
+typedef int (*data_cmd_fn_t)(int argc, const char **argv);
+
+struct data_cmd {
+	const char	*name;
+	const char	*summary;
+	data_cmd_fn_t	fn;
+};
+
+static struct data_cmd data_cmds[];
+
+#define for_each_cmd(cmd) \
+	for (cmd = data_cmds; cmd && cmd->name; cmd++)
+
+static const char * const data_subcommands[] = { "convert", NULL };
+
+static const char *data_usage[] = {
+	"perf data convert [<options>]",
+	NULL
+};
+
+static const char *to_json;
+static const char *to_ctf;
+static struct perf_data_convert_opts opts = {
+	.force = false,
+	.all = false,
+	.time_str = NULL,
+};
+
+static const struct option data_options[] = {
+		OPT_INCR('v', "verbose", &verbose, "be more verbose"),
+		OPT_STRING('i', "input", &input_name, "file", "input file name"),
+		OPT_STRING(0, "to-json", &to_json, NULL, "Convert to JSON format"),
+		OPT_STRING(0, "to-ctf", &to_ctf, NULL, "Convert to CTF format"),
+		OPT_BOOLEAN(0, "tod", &opts.tod, "Convert time to wall clock time"),
+		OPT_BOOLEAN('f', "force", &opts.force, "don't complain, do it"),
+		OPT_BOOLEAN(0, "all", &opts.all, "Convert all events"),
+		OPT_STRING(0, "time", &opts.time_str, "str",
+			   "Time span of interest (start,stop)"),
+		OPT_END()
+	};
+
+static int cmd_data_convert(int argc, const char **argv)
+{
+
+	argc = parse_options(argc, argv, data_options,
+			     data_usage, 0);
+	if (argc) {
+		usage_with_options(data_usage, data_options);
+		return -1;
+	}
+
+	if (to_json && to_ctf) {
+		pr_err("You cannot specify both --to-ctf and --to-json.\n");
+		return -1;
+	}
+	if (!to_json && !to_ctf) {
+		pr_err("You must specify one of --to-ctf or --to-json.\n");
+		return -1;
+	}
+
+	if (to_json)
+		return bt_convert__perf2json(input_name, to_json, &opts);
+
+	if (to_ctf) {
+#if defined(HAVE_BABELTRACE2_CTF_WRITER_SUPPORT) && defined(HAVE_LIBTRACEEVENT)
+		return bt_convert__perf2ctf(input_name, to_ctf, &opts);
+#else
+		pr_err("The babeltrace2 ctf support is not compiled in. Ensure you have both\n"
+			"libbabeltrace2-dev[el] and libtraceevent-dev[el] installed or set\n"
+			"PKG_CONFIG_PATH to find a local installation of those libraries.\n");
+		return -1;
+#endif
+	}
+
+	return 0;
+}
+
+static struct data_cmd data_cmds[] = {
+	{ "convert", "converts data file between formats", cmd_data_convert },
+	{ .name = NULL, },
+};
+
+int cmd_data(int argc, const char **argv)
+{
+	struct data_cmd *cmd;
+	const char *cmdstr;
+
+	argc = parse_options_subcommand(argc, argv, data_options, data_subcommands, data_usage,
+			     PARSE_OPT_STOP_AT_NON_OPTION);
+
+	if (!argc) {
+		usage_with_options(data_usage, data_options);
+		return -1;
+	}
+
+	cmdstr = argv[0];
+
+	for_each_cmd(cmd) {
+		if (strcmp(cmd->name, cmdstr))
+			continue;
+
+		return cmd->fn(argc, argv);
+	}
+
+	pr_err("Unknown command: %s\n", cmdstr);
+	usage_with_options(data_usage, data_options);
+	return -1;
+}