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, 506 insertions, 0 deletions

diff --git a/tools/perf/util/cputopo.c b/tools/perf/util/cputopo.c
new file mode 100644
index 000000000..e0091804f
--- /dev/null
+++ b/tools/perf/util/cputopo.c
@@ -0,0 +1,506 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <sys/param.h>
+#include <sys/utsname.h>
+#include <inttypes.h>
+#include <stdlib.h>
+#include <string.h>
+#include <api/fs/fs.h>
+#include <linux/zalloc.h>
+#include <perf/cpumap.h>
+
+#include "cputopo.h"
+#include "cpumap.h"
+#include "debug.h"
+#include "env.h"
+#include "pmu.h"
+#include "pmus.h"
+
+#define PACKAGE_CPUS_FMT \
+	"%s/devices/system/cpu/cpu%d/topology/package_cpus_list"
+#define PACKAGE_CPUS_FMT_OLD \
+	"%s/devices/system/cpu/cpu%d/topology/core_siblings_list"
+#define DIE_CPUS_FMT \
+	"%s/devices/system/cpu/cpu%d/topology/die_cpus_list"
+#define CORE_CPUS_FMT \
+	"%s/devices/system/cpu/cpu%d/topology/core_cpus_list"
+#define CORE_CPUS_FMT_OLD \
+	"%s/devices/system/cpu/cpu%d/topology/thread_siblings_list"
+#define NODE_ONLINE_FMT \
+	"%s/devices/system/node/online"
+#define NODE_MEMINFO_FMT \
+	"%s/devices/system/node/node%d/meminfo"
+#define NODE_CPULIST_FMT \
+	"%s/devices/system/node/node%d/cpulist"
+
+static int build_cpu_topology(struct cpu_topology *tp, int cpu)
+{
+	FILE *fp;
+	char filename[MAXPATHLEN];
+	char *buf = NULL, *p;
+	size_t len = 0;
+	ssize_t sret;
+	u32 i = 0;
+	int ret = -1;
+
+	scnprintf(filename, MAXPATHLEN, PACKAGE_CPUS_FMT,
+		  sysfs__mountpoint(), cpu);
+	if (access(filename, F_OK) == -1) {
+		scnprintf(filename, MAXPATHLEN, PACKAGE_CPUS_FMT_OLD,
+			sysfs__mountpoint(), cpu);
+	}
+	fp = fopen(filename, "r");
+	if (!fp)
+		goto try_dies;
+
+	sret = getline(&buf, &len, fp);
+	fclose(fp);
+	if (sret <= 0)
+		goto try_dies;
+
+	p = strchr(buf, '\n');
+	if (p)
+		*p = '\0';
+
+	for (i = 0; i < tp->package_cpus_lists; i++) {
+		if (!strcmp(buf, tp->package_cpus_list[i]))
+			break;
+	}
+	if (i == tp->package_cpus_lists) {
+		tp->package_cpus_list[i] = buf;
+		tp->package_cpus_lists++;
+		buf = NULL;
+		len = 0;
+	}
+	ret = 0;
+
+try_dies:
+	if (!tp->die_cpus_list)
+		goto try_threads;
+
+	scnprintf(filename, MAXPATHLEN, DIE_CPUS_FMT,
+		  sysfs__mountpoint(), cpu);
+	fp = fopen(filename, "r");
+	if (!fp)
+		goto try_threads;
+
+	sret = getline(&buf, &len, fp);
+	fclose(fp);
+	if (sret <= 0)
+		goto try_threads;
+
+	p = strchr(buf, '\n');
+	if (p)
+		*p = '\0';
+
+	for (i = 0; i < tp->die_cpus_lists; i++) {
+		if (!strcmp(buf, tp->die_cpus_list[i]))
+			break;
+	}
+	if (i == tp->die_cpus_lists) {
+		tp->die_cpus_list[i] = buf;
+		tp->die_cpus_lists++;
+		buf = NULL;
+		len = 0;
+	}
+	ret = 0;
+
+try_threads:
+	scnprintf(filename, MAXPATHLEN, CORE_CPUS_FMT,
+		  sysfs__mountpoint(), cpu);
+	if (access(filename, F_OK) == -1) {
+		scnprintf(filename, MAXPATHLEN, CORE_CPUS_FMT_OLD,
+			  sysfs__mountpoint(), cpu);
+	}
+	fp = fopen(filename, "r");
+	if (!fp)
+		goto done;
+
+	if (getline(&buf, &len, fp) <= 0)
+		goto done;
+
+	p = strchr(buf, '\n');
+	if (p)
+		*p = '\0';
+
+	for (i = 0; i < tp->core_cpus_lists; i++) {
+		if (!strcmp(buf, tp->core_cpus_list[i]))
+			break;
+	}
+	if (i == tp->core_cpus_lists) {
+		tp->core_cpus_list[i] = buf;
+		tp->core_cpus_lists++;
+		buf = NULL;
+	}
+	ret = 0;
+done:
+	if (fp)
+		fclose(fp);
+	free(buf);
+	return ret;
+}
+
+void cpu_topology__delete(struct cpu_topology *tp)
+{
+	u32 i;
+
+	if (!tp)
+		return;
+
+	for (i = 0 ; i < tp->package_cpus_lists; i++)
+		zfree(&tp->package_cpus_list[i]);
+
+	for (i = 0 ; i < tp->die_cpus_lists; i++)
+		zfree(&tp->die_cpus_list[i]);
+
+	for (i = 0 ; i < tp->core_cpus_lists; i++)
+		zfree(&tp->core_cpus_list[i]);
+
+	free(tp);
+}
+
+bool cpu_topology__smt_on(const struct cpu_topology *topology)
+{
+	for (u32 i = 0; i < topology->core_cpus_lists; i++) {
+		const char *cpu_list = topology->core_cpus_list[i];
+
+		/*
+		 * If there is a need to separate siblings in a core then SMT is
+		 * enabled.
+		 */
+		if (strchr(cpu_list, ',') || strchr(cpu_list, '-'))
+			return true;
+	}
+	return false;
+}
+
+bool cpu_topology__core_wide(const struct cpu_topology *topology,
+			     const char *user_requested_cpu_list)
+{
+	struct perf_cpu_map *user_requested_cpus;
+
+	/*
+	 * If user_requested_cpu_list is empty then all CPUs are recorded and so
+	 * core_wide is true.
+	 */
+	if (!user_requested_cpu_list)
+		return true;
+
+	user_requested_cpus = perf_cpu_map__new(user_requested_cpu_list);
+	/* Check that every user requested CPU is the complete set of SMT threads on a core. */
+	for (u32 i = 0; i < topology->core_cpus_lists; i++) {
+		const char *core_cpu_list = topology->core_cpus_list[i];
+		struct perf_cpu_map *core_cpus = perf_cpu_map__new(core_cpu_list);
+		struct perf_cpu cpu;
+		unsigned int idx;
+		bool has_first, first = true;
+
+		perf_cpu_map__for_each_cpu(cpu, idx, core_cpus) {
+			if (first) {
+				has_first = perf_cpu_map__has(user_requested_cpus, cpu);
+				first = false;
+			} else {
+				/*
+				 * If the first core CPU is user requested then
+				 * all subsequent CPUs in the core must be user
+				 * requested too. If the first CPU isn't user
+				 * requested then none of the others must be
+				 * too.
+				 */
+				if (perf_cpu_map__has(user_requested_cpus, cpu) != has_first) {
+					perf_cpu_map__put(core_cpus);
+					perf_cpu_map__put(user_requested_cpus);
+					return false;
+				}
+			}
+		}
+		perf_cpu_map__put(core_cpus);
+	}
+	perf_cpu_map__put(user_requested_cpus);
+	return true;
+}
+
+static bool has_die_topology(void)
+{
+	char filename[MAXPATHLEN];
+	struct utsname uts;
+
+	if (uname(&uts) < 0)
+		return false;
+
+	if (strncmp(uts.machine, "x86_64", 6) &&
+	    strncmp(uts.machine, "s390x", 5))
+		return false;
+
+	scnprintf(filename, MAXPATHLEN, DIE_CPUS_FMT,
+		  sysfs__mountpoint(), 0);
+	if (access(filename, F_OK) == -1)
+		return false;
+
+	return true;
+}
+
+const struct cpu_topology *online_topology(void)
+{
+	static const struct cpu_topology *topology;
+
+	if (!topology) {
+		topology = cpu_topology__new();
+		if (!topology) {
+			pr_err("Error creating CPU topology");
+			abort();
+		}
+	}
+	return topology;
+}
+
+struct cpu_topology *cpu_topology__new(void)
+{
+	struct cpu_topology *tp = NULL;
+	void *addr;
+	u32 nr, i, nr_addr;
+	size_t sz;
+	long ncpus;
+	int ret = -1;
+	struct perf_cpu_map *map;
+	bool has_die = has_die_topology();
+
+	ncpus = cpu__max_present_cpu().cpu;
+
+	/* build online CPU map */
+	map = perf_cpu_map__new_online_cpus();
+	if (map == NULL) {
+		pr_debug("failed to get system cpumap\n");
+		return NULL;
+	}
+
+	nr = (u32)(ncpus & UINT_MAX);
+
+	sz = nr * sizeof(char *);
+	if (has_die)
+		nr_addr = 3;
+	else
+		nr_addr = 2;
+	addr = calloc(1, sizeof(*tp) + nr_addr * sz);
+	if (!addr)
+		goto out_free;
+
+	tp = addr;
+	addr += sizeof(*tp);
+	tp->package_cpus_list = addr;
+	addr += sz;
+	if (has_die) {
+		tp->die_cpus_list = addr;
+		addr += sz;
+	}
+	tp->core_cpus_list = addr;
+
+	for (i = 0; i < nr; i++) {
+		if (!perf_cpu_map__has(map, (struct perf_cpu){ .cpu = i }))
+			continue;
+
+		ret = build_cpu_topology(tp, i);
+		if (ret < 0)
+			break;
+	}
+
+out_free:
+	perf_cpu_map__put(map);
+	if (ret) {
+		cpu_topology__delete(tp);
+		tp = NULL;
+	}
+	return tp;
+}
+
+static int load_numa_node(struct numa_topology_node *node, int nr)
+{
+	char str[MAXPATHLEN];
+	char field[32];
+	char *buf = NULL, *p;
+	size_t len = 0;
+	int ret = -1;
+	FILE *fp;
+	u64 mem;
+
+	node->node = (u32) nr;
+
+	scnprintf(str, MAXPATHLEN, NODE_MEMINFO_FMT,
+		  sysfs__mountpoint(), nr);
+	fp = fopen(str, "r");
+	if (!fp)
+		return -1;
+
+	while (getline(&buf, &len, fp) > 0) {
+		/* skip over invalid lines */
+		if (!strchr(buf, ':'))
+			continue;
+		if (sscanf(buf, "%*s %*d %31s %"PRIu64, field, &mem) != 2)
+			goto err;
+		if (!strcmp(field, "MemTotal:"))
+			node->mem_total = mem;
+		if (!strcmp(field, "MemFree:"))
+			node->mem_free = mem;
+		if (node->mem_total && node->mem_free)
+			break;
+	}
+
+	fclose(fp);
+	fp = NULL;
+
+	scnprintf(str, MAXPATHLEN, NODE_CPULIST_FMT,
+		  sysfs__mountpoint(), nr);
+
+	fp = fopen(str, "r");
+	if (!fp)
+		return -1;
+
+	if (getline(&buf, &len, fp) <= 0)
+		goto err;
+
+	p = strchr(buf, '\n');
+	if (p)
+		*p = '\0';
+
+	node->cpus = buf;
+	fclose(fp);
+	return 0;
+
+err:
+	free(buf);
+	if (fp)
+		fclose(fp);
+	return ret;
+}
+
+struct numa_topology *numa_topology__new(void)
+{
+	struct perf_cpu_map *node_map = NULL;
+	struct numa_topology *tp = NULL;
+	char path[MAXPATHLEN];
+	char *buf = NULL;
+	size_t len = 0;
+	u32 nr, i;
+	FILE *fp;
+	char *c;
+
+	scnprintf(path, MAXPATHLEN, NODE_ONLINE_FMT,
+		  sysfs__mountpoint());
+
+	fp = fopen(path, "r");
+	if (!fp)
+		return NULL;
+
+	if (getline(&buf, &len, fp) <= 0)
+		goto out;
+
+	c = strchr(buf, '\n');
+	if (c)
+		*c = '\0';
+
+	node_map = perf_cpu_map__new(buf);
+	if (!node_map)
+		goto out;
+
+	nr = (u32) perf_cpu_map__nr(node_map);
+
+	tp = zalloc(sizeof(*tp) + sizeof(tp->nodes[0])*nr);
+	if (!tp)
+		goto out;
+
+	tp->nr = nr;
+
+	for (i = 0; i < nr; i++) {
+		if (load_numa_node(&tp->nodes[i], perf_cpu_map__cpu(node_map, i).cpu)) {
+			numa_topology__delete(tp);
+			tp = NULL;
+			break;
+		}
+	}
+
+out:
+	free(buf);
+	fclose(fp);
+	perf_cpu_map__put(node_map);
+	return tp;
+}
+
+void numa_topology__delete(struct numa_topology *tp)
+{
+	u32 i;
+
+	for (i = 0; i < tp->nr; i++)
+		zfree(&tp->nodes[i].cpus);
+
+	free(tp);
+}
+
+static int load_hybrid_node(struct hybrid_topology_node *node,
+			    struct perf_pmu *pmu)
+{
+	char *buf = NULL, *p;
+	FILE *fp;
+	size_t len = 0;
+
+	node->pmu_name = strdup(pmu->name);
+	if (!node->pmu_name)
+		return -1;
+
+	fp = perf_pmu__open_file(pmu, "cpus");
+	if (!fp)
+		goto err;
+
+	if (getline(&buf, &len, fp) <= 0) {
+		fclose(fp);
+		goto err;
+	}
+
+	p = strchr(buf, '\n');
+	if (p)
+		*p = '\0';
+
+	fclose(fp);
+	node->cpus = buf;
+	return 0;
+
+err:
+	zfree(&node->pmu_name);
+	free(buf);
+	return -1;
+}
+
+struct hybrid_topology *hybrid_topology__new(void)
+{
+	struct perf_pmu *pmu = NULL;
+	struct hybrid_topology *tp = NULL;
+	int nr = perf_pmus__num_core_pmus(), i = 0;
+
+	if (nr <= 1)
+		return NULL;
+
+	tp = zalloc(sizeof(*tp) + sizeof(tp->nodes[0]) * nr);
+	if (!tp)
+		return NULL;
+
+	tp->nr = nr;
+	while ((pmu = perf_pmus__scan_core(pmu)) != NULL) {
+		if (load_hybrid_node(&tp->nodes[i], pmu)) {
+			hybrid_topology__delete(tp);
+			return NULL;
+		}
+		i++;
+	}
+
+	return tp;
+}
+
+void hybrid_topology__delete(struct hybrid_topology *tp)
+{
+	u32 i;
+
+	for (i = 0; i < tp->nr; i++) {
+		zfree(&tp->nodes[i].pmu_name);
+		zfree(&tp->nodes[i].cpus);
+	}
+
+	free(tp);
+}