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, 553 insertions, 0 deletions

diff --git a/tools/perf/builtin-mem.c b/tools/perf/builtin-mem.c
new file mode 100644
index 000000000..6101a26b3
--- /dev/null
+++ b/tools/perf/builtin-mem.c
@@ -0,0 +1,553 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <errno.h>
+#include <inttypes.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include "builtin.h"
+#include "perf.h"
+
+#include <subcmd/parse-options.h>
+#include "util/auxtrace.h"
+#include "util/trace-event.h"
+#include "util/tool.h"
+#include "util/session.h"
+#include "util/data.h"
+#include "util/map_symbol.h"
+#include "util/mem-events.h"
+#include "util/debug.h"
+#include "util/dso.h"
+#include "util/map.h"
+#include "util/symbol.h"
+#include "util/pmus.h"
+#include "util/sample.h"
+#include "util/sort.h"
+#include "util/string2.h"
+#include "util/util.h"
+#include <linux/err.h>
+
+#define MEM_OPERATION_LOAD	0x1
+#define MEM_OPERATION_STORE	0x2
+
+struct perf_mem {
+	struct perf_tool	tool;
+	const char		*input_name;
+	const char		*sort_key;
+	bool			hide_unresolved;
+	bool			dump_raw;
+	bool			force;
+	bool			phys_addr;
+	bool			data_page_size;
+	bool			all_kernel;
+	bool			all_user;
+	bool			data_type;
+	int			operation;
+	const char		*cpu_list;
+	DECLARE_BITMAP(cpu_bitmap, MAX_NR_CPUS);
+};
+
+static int parse_record_events(const struct option *opt,
+			       const char *str, int unset __maybe_unused)
+{
+	struct perf_mem *mem = (struct perf_mem *)opt->value;
+	struct perf_pmu *pmu;
+
+	pmu = perf_mem_events_find_pmu();
+	if (!pmu) {
+		pr_err("failed: there is no PMU that supports perf mem\n");
+		exit(-1);
+	}
+
+	if (!strcmp(str, "list")) {
+		perf_pmu__mem_events_list(pmu);
+		exit(0);
+	}
+	if (perf_pmu__mem_events_parse(pmu, str))
+		exit(-1);
+
+	mem->operation = 0;
+	return 0;
+}
+
+static int __cmd_record(int argc, const char **argv, struct perf_mem *mem,
+			const struct option *options)
+{
+	int rec_argc, i = 0, j;
+	int start, end;
+	const char **rec_argv;
+	char *event_name_storage = NULL;
+	int ret;
+	struct perf_mem_event *e;
+	struct perf_pmu *pmu;
+	const char * const record_usage[] = {
+		"perf mem record [<options>] [<command>]",
+		"perf mem record [<options>] -- <command> [<options>]",
+		NULL
+	};
+
+	pmu = perf_mem_events_find_pmu();
+	if (!pmu) {
+		pr_err("failed: no PMU supports the memory events\n");
+		return -1;
+	}
+
+	if (perf_pmu__mem_events_init()) {
+		pr_err("failed: memory events not supported\n");
+		return -1;
+	}
+
+	argc = parse_options(argc, argv, options, record_usage,
+			     PARSE_OPT_KEEP_UNKNOWN);
+
+	/* Max number of arguments multiplied by number of PMUs that can support them. */
+	rec_argc = argc + 9 * (perf_pmu__mem_events_num_mem_pmus(pmu) + 1);
+
+	if (mem->cpu_list)
+		rec_argc += 2;
+
+	rec_argv = calloc(rec_argc + 1, sizeof(char *));
+	if (!rec_argv)
+		return -1;
+
+	rec_argv[i++] = "record";
+
+	e = perf_pmu__mem_events_ptr(pmu, PERF_MEM_EVENTS__LOAD_STORE);
+
+	/*
+	 * The load and store operations are required, use the event
+	 * PERF_MEM_EVENTS__LOAD_STORE if it is supported.
+	 */
+	if (e->tag &&
+	    (mem->operation & MEM_OPERATION_LOAD) &&
+	    (mem->operation & MEM_OPERATION_STORE)) {
+		perf_mem_record[PERF_MEM_EVENTS__LOAD_STORE] = true;
+		rec_argv[i++] = "-W";
+	} else {
+		if (mem->operation & MEM_OPERATION_LOAD)
+			perf_mem_record[PERF_MEM_EVENTS__LOAD] = true;
+
+		if (mem->operation & MEM_OPERATION_STORE)
+			perf_mem_record[PERF_MEM_EVENTS__STORE] = true;
+	}
+
+	if (perf_mem_record[PERF_MEM_EVENTS__LOAD])
+		rec_argv[i++] = "-W";
+
+	rec_argv[i++] = "-d";
+
+	if (mem->phys_addr)
+		rec_argv[i++] = "--phys-data";
+
+	if (mem->data_page_size)
+		rec_argv[i++] = "--data-page-size";
+
+	start = i;
+	ret = perf_mem_events__record_args(rec_argv, &i, &event_name_storage);
+	if (ret)
+		goto out;
+	end = i;
+
+	if (mem->all_user)
+		rec_argv[i++] = "--all-user";
+
+	if (mem->all_kernel)
+		rec_argv[i++] = "--all-kernel";
+
+	if (mem->cpu_list) {
+		rec_argv[i++] = "-C";
+		rec_argv[i++] = mem->cpu_list;
+	}
+
+	for (j = 0; j < argc; j++, i++)
+		rec_argv[i] = argv[j];
+
+	if (verbose > 0) {
+		pr_debug("calling: record ");
+
+		for (j = start; j < end; j++)
+			pr_debug("%s ", rec_argv[j]);
+
+		pr_debug("\n");
+	}
+
+	ret = cmd_record(i, rec_argv);
+out:
+	free(event_name_storage);
+	free(rec_argv);
+	return ret;
+}
+
+static int
+dump_raw_samples(const struct perf_tool *tool,
+		 union perf_event *event,
+		 struct perf_sample *sample,
+		 struct machine *machine)
+{
+	struct perf_mem *mem = container_of(tool, struct perf_mem, tool);
+	struct addr_location al;
+	const char *fmt, *field_sep;
+	char str[PAGE_SIZE_NAME_LEN];
+	struct dso *dso = NULL;
+
+	addr_location__init(&al);
+	if (machine__resolve(machine, &al, sample) < 0) {
+		fprintf(stderr, "problem processing %d event, skipping it.\n",
+				event->header.type);
+		addr_location__exit(&al);
+		return -1;
+	}
+
+	if (al.filtered || (mem->hide_unresolved && al.sym == NULL))
+		goto out_put;
+
+	if (al.map != NULL) {
+		dso = map__dso(al.map);
+		if (dso)
+			dso__set_hit(dso);
+	}
+
+	field_sep = symbol_conf.field_sep;
+	if (field_sep) {
+		fmt = "%d%s%d%s0x%"PRIx64"%s0x%"PRIx64"%s";
+	} else {
+		fmt = "%5d%s%5d%s0x%016"PRIx64"%s0x016%"PRIx64"%s";
+		symbol_conf.field_sep = " ";
+	}
+	printf(fmt,
+		sample->pid,
+		symbol_conf.field_sep,
+		sample->tid,
+		symbol_conf.field_sep,
+		sample->ip,
+		symbol_conf.field_sep,
+		sample->addr,
+		symbol_conf.field_sep);
+
+	if (mem->phys_addr) {
+		printf("0x%016"PRIx64"%s",
+			sample->phys_addr,
+			symbol_conf.field_sep);
+	}
+
+	if (mem->data_page_size) {
+		printf("%s%s",
+			get_page_size_name(sample->data_page_size, str),
+			symbol_conf.field_sep);
+	}
+
+	if (field_sep)
+		fmt = "%"PRIu64"%s0x%"PRIx64"%s%s:%s\n";
+	else
+		fmt = "%5"PRIu64"%s0x%06"PRIx64"%s%s:%s\n";
+
+	printf(fmt,
+		sample->weight,
+		symbol_conf.field_sep,
+		sample->data_src,
+		symbol_conf.field_sep,
+		dso ? dso__long_name(dso) : "???",
+		al.sym ? al.sym->name : "???");
+out_put:
+	addr_location__exit(&al);
+	return 0;
+}
+
+static int process_sample_event(const struct perf_tool *tool,
+				union perf_event *event,
+				struct perf_sample *sample,
+				struct machine *machine)
+{
+	return dump_raw_samples(tool, event, sample, machine);
+}
+
+static int report_raw_events(struct perf_mem *mem)
+{
+	struct itrace_synth_opts itrace_synth_opts = {
+		.set = true,
+		.mem = true,	/* Only enable memory event */
+		.default_no_sample = true,
+	};
+
+	struct perf_data data = {
+		.path  = input_name,
+		.mode  = PERF_DATA_MODE_READ,
+		.force = mem->force,
+	};
+	int ret;
+	struct perf_session *session;
+
+	perf_tool__init(&mem->tool, /*ordered_events=*/true);
+	mem->tool.sample		= process_sample_event;
+	mem->tool.mmap		= perf_event__process_mmap;
+	mem->tool.mmap2		= perf_event__process_mmap2;
+	mem->tool.comm		= perf_event__process_comm;
+	mem->tool.lost		= perf_event__process_lost;
+	mem->tool.fork		= perf_event__process_fork;
+	mem->tool.attr		= perf_event__process_attr;
+	mem->tool.build_id	= perf_event__process_build_id;
+	mem->tool.namespaces	= perf_event__process_namespaces;
+	mem->tool.auxtrace_info  = perf_event__process_auxtrace_info;
+	mem->tool.auxtrace       = perf_event__process_auxtrace;
+	mem->tool.auxtrace_error = perf_event__process_auxtrace_error;
+
+	session = perf_session__new(&data, &mem->tool);
+
+	if (IS_ERR(session))
+		return PTR_ERR(session);
+
+	session->itrace_synth_opts = &itrace_synth_opts;
+
+	if (mem->cpu_list) {
+		ret = perf_session__cpu_bitmap(session, mem->cpu_list,
+					       mem->cpu_bitmap);
+		if (ret < 0)
+			goto out_delete;
+	}
+
+	ret = symbol__init(perf_session__env(session));
+	if (ret < 0)
+		goto out_delete;
+
+	printf("# PID, TID, IP, ADDR, ");
+
+	if (mem->phys_addr)
+		printf("PHYS ADDR, ");
+
+	if (mem->data_page_size)
+		printf("DATA PAGE SIZE, ");
+
+	printf("LOCAL WEIGHT, DSRC, SYMBOL\n");
+
+	ret = perf_session__process_events(session);
+
+out_delete:
+	perf_session__delete(session);
+	return ret;
+}
+
+static char *get_sort_order(struct perf_mem *mem)
+{
+	bool has_extra_options = (mem->phys_addr | mem->data_page_size) ? true : false;
+	char sort[128];
+
+	if (mem->sort_key)
+		scnprintf(sort, sizeof(sort), "--sort=%s", mem->sort_key);
+	else if (mem->data_type)
+		strcpy(sort, "--sort=mem,snoop,tlb,type");
+	/*
+	 * there is no weight (cost) associated with stores, so don't print
+	 * the column
+	 */
+	else if (!(mem->operation & MEM_OPERATION_LOAD)) {
+		strcpy(sort, "--sort=mem,sym,dso,symbol_daddr,"
+			     "dso_daddr,tlb,locked");
+	} else if (has_extra_options) {
+		strcpy(sort, "--sort=local_weight,mem,sym,dso,symbol_daddr,"
+			     "dso_daddr,snoop,tlb,locked,blocked");
+	} else
+		return NULL;
+
+	if (mem->phys_addr)
+		strcat(sort, ",phys_daddr");
+
+	if (mem->data_page_size)
+		strcat(sort, ",data_page_size");
+
+	/* make sure it has 'type' sort key even -s option is used */
+	if (mem->data_type && !strstr(sort, "type"))
+		strcat(sort, ",type");
+
+	return strdup(sort);
+}
+
+static int __cmd_report(int argc, const char **argv, struct perf_mem *mem,
+			const struct option *options)
+{
+	const char **rep_argv;
+	int ret, i = 0, j, rep_argc;
+	char *new_sort_order;
+	const char * const report_usage[] = {
+		"perf mem report [<options>]",
+		NULL
+	};
+
+	argc = parse_options(argc, argv, options, report_usage,
+			     PARSE_OPT_KEEP_UNKNOWN);
+
+	if (mem->dump_raw)
+		return report_raw_events(mem);
+
+	rep_argc = argc + 3;
+	rep_argv = calloc(rep_argc + 1, sizeof(char *));
+	if (!rep_argv)
+		return -1;
+
+	rep_argv[i++] = "report";
+	rep_argv[i++] = "--mem-mode";
+	rep_argv[i++] = "-n"; /* display number of samples */
+
+	new_sort_order = get_sort_order(mem);
+	if (new_sort_order)
+		rep_argv[i++] = new_sort_order;
+
+	for (j = 0; j < argc; j++, i++)
+		rep_argv[i] = argv[j];
+
+	ret = cmd_report(i, rep_argv);
+	free(new_sort_order);
+	free(rep_argv);
+	return ret;
+}
+
+struct mem_mode {
+	const char *name;
+	int mode;
+};
+
+#define MEM_OPT(n, m) \
+	{ .name = n, .mode = (m) }
+
+#define MEM_END { .name = NULL }
+
+static const struct mem_mode mem_modes[]={
+	MEM_OPT("load", MEM_OPERATION_LOAD),
+	MEM_OPT("store", MEM_OPERATION_STORE),
+	MEM_END
+};
+
+static int
+parse_mem_ops(const struct option *opt, const char *str, int unset)
+{
+	int *mode = (int *)opt->value;
+	const struct mem_mode *m;
+	char *s, *os = NULL, *p;
+	int ret = -1;
+
+	if (unset)
+		return 0;
+
+	/* str may be NULL in case no arg is passed to -t */
+	if (str) {
+		/* because str is read-only */
+		s = os = strdup(str);
+		if (!s)
+			return -1;
+
+		/* reset mode */
+		*mode = 0;
+
+		for (;;) {
+			p = strchr(s, ',');
+			if (p)
+				*p = '\0';
+
+			for (m = mem_modes; m->name; m++) {
+				if (!strcasecmp(s, m->name))
+					break;
+			}
+			if (!m->name) {
+				fprintf(stderr, "unknown sampling op %s,"
+					    " check man page\n", s);
+				goto error;
+			}
+
+			*mode |= m->mode;
+
+			if (!p)
+				break;
+
+			s = p + 1;
+		}
+	}
+	ret = 0;
+
+	if (*mode == 0)
+		*mode = MEM_OPERATION_LOAD;
+error:
+	free(os);
+	return ret;
+}
+
+int cmd_mem(int argc, const char **argv)
+{
+	struct stat st;
+	struct perf_mem mem = {
+		.input_name		 = "perf.data",
+		/*
+		 * default to both load an store sampling
+		 */
+		.operation		 = MEM_OPERATION_LOAD | MEM_OPERATION_STORE,
+	};
+	char *sort_order_help = sort_help("sort by key(s):", SORT_MODE__MEMORY);
+	const struct option mem_options[] = {
+	OPT_CALLBACK('t', "type", &mem.operation,
+		   "type", "memory operations(load,store) Default load,store",
+		    parse_mem_ops),
+	OPT_STRING('C', "cpu", &mem.cpu_list, "cpu",
+		   "list of cpus to profile"),
+	OPT_BOOLEAN('f', "force", &mem.force, "don't complain, do it"),
+	OPT_INCR('v', "verbose", &verbose,
+		 "be more verbose (show counter open errors, etc)"),
+	OPT_BOOLEAN('p', "phys-data", &mem.phys_addr, "Record/Report sample physical addresses"),
+	OPT_BOOLEAN(0, "data-page-size", &mem.data_page_size, "Record/Report sample data address page size"),
+	OPT_END()
+	};
+	const struct option record_options[] = {
+	OPT_CALLBACK('e', "event", &mem, "event",
+		     "event selector. use 'perf mem record -e list' to list available events",
+		     parse_record_events),
+	OPT_UINTEGER(0, "ldlat", &perf_mem_events__loads_ldlat, "mem-loads latency"),
+	OPT_BOOLEAN('U', "all-user", &mem.all_user, "collect only user level data"),
+	OPT_BOOLEAN('K', "all-kernel", &mem.all_kernel, "collect only kernel level data"),
+	OPT_PARENT(mem_options)
+	};
+	const struct option report_options[] = {
+	OPT_BOOLEAN('D', "dump-raw-samples", &mem.dump_raw,
+		    "dump raw samples in ASCII"),
+	OPT_BOOLEAN('U', "hide-unresolved", &mem.hide_unresolved,
+		    "Only display entries resolved to a symbol"),
+	OPT_STRING('i', "input", &input_name, "file",
+		   "input file name"),
+	OPT_STRING_NOEMPTY('x', "field-separator", &symbol_conf.field_sep,
+		   "separator",
+		   "separator for columns, no spaces will be added"
+		   " between columns '.' is reserved."),
+	OPT_STRING('s', "sort", &mem.sort_key, "key[,key2...]",
+		   sort_order_help),
+	OPT_BOOLEAN('T', "type-profile", &mem.data_type,
+		    "Show data-type profile result"),
+	OPT_PARENT(mem_options)
+	};
+	const char *const mem_subcommands[] = { "record", "report", NULL };
+	const char *mem_usage[] = {
+		NULL,
+		NULL
+	};
+	int ret;
+
+	argc = parse_options_subcommand(argc, argv, mem_options, mem_subcommands,
+					mem_usage, PARSE_OPT_STOP_AT_NON_OPTION);
+
+	if (!argc || !(strncmp(argv[0], "rec", 3) || mem.operation))
+		usage_with_options(mem_usage, mem_options);
+
+	if (!mem.input_name || !strlen(mem.input_name)) {
+		if (!fstat(STDIN_FILENO, &st) && S_ISFIFO(st.st_mode))
+			mem.input_name = "-";
+		else
+			mem.input_name = "perf.data";
+	}
+
+	if (strlen(argv[0]) > 2 && strstarts("record", argv[0]))
+		ret = __cmd_record(argc, argv, &mem, record_options);
+	else if (strlen(argv[0]) > 2 && strstarts("report", argv[0]))
+		ret = __cmd_report(argc, argv, &mem, report_options);
+	else
+		usage_with_options(mem_usage, mem_options);
+
+	/* free usage string allocated by parse_options_subcommand */
+	free((void *)mem_usage[0]);
+	free(sort_order_help);
+
+	return ret;
+}