From 5febf432df1cfa5b25d99b54c32103fafbdd0eb9 Mon Sep 17 00:00:00 2001 From: Miguel Ojeda Date: Sun, 16 Aug 2026 15:32:33 +0200 Subject: kbuild: rust: keep Rust objects out of Clang LTO with inline helpers 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 Cc: Boqun Feng Cc: Alice Ryhl Cc: Matthew Maurer Cc: Josh Poimboeuf Cc: Peter Zijlstra Cc: stable@vger.kernel.org Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust") Acked-by: Gary Guo Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org Signed-off-by: Miguel Ojeda --- tools/perf/tests/sdt.c | 124 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 124 insertions(+) create mode 100644 tools/perf/tests/sdt.c (limited to 'tools/perf/tests/sdt.c') diff --git a/tools/perf/tests/sdt.c b/tools/perf/tests/sdt.c new file mode 100644 index 000000000..93baee2ea --- /dev/null +++ b/tools/perf/tests/sdt.c @@ -0,0 +1,124 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include +#include +#include +#include +#include "tests.h" +#include "debug.h" +#include "probe-file.h" +#include "build-id.h" +#include "util.h" + +/* To test SDT event, we need libelf support to scan elf binary */ +#if defined(HAVE_SDT_EVENT) && defined(HAVE_LIBELF_SUPPORT) + +#include + +static int target_function(void) +{ + DTRACE_PROBE(perf, test_target); + return TEST_OK; +} + +/* Copied from builtin-buildid-cache.c */ +static int build_id_cache__add_file(const char *filename) +{ + char sbuild_id[SBUILD_ID_SIZE]; + struct build_id bid = { .size = 0, }; + int err; + + err = filename__read_build_id(filename, &bid); + if (err < 0) { + pr_debug("Failed to read build id of %s\n", filename); + return err; + } + + build_id__snprintf(&bid, sbuild_id, sizeof(sbuild_id)); + err = build_id_cache__add_s(sbuild_id, filename, NULL, false, false); + if (err < 0) + pr_debug("Failed to add build id cache of %s\n", filename); + return err; +} + +static char *get_self_path(void) +{ + char *buf = calloc(PATH_MAX, sizeof(char)); + + if (buf && readlink("/proc/self/exe", buf, PATH_MAX - 1) < 0) { + pr_debug("Failed to get correct path of perf\n"); + free(buf); + return NULL; + } + return buf; +} + +static int search_cached_probe(const char *target, + const char *group, const char *event) +{ + struct probe_cache *cache = probe_cache__new(target, NULL); + int ret = 0; + + if (!cache) { + pr_debug("Failed to open probe cache of %s\n", target); + return -EINVAL; + } + + if (!probe_cache__find_by_name(cache, group, event)) { + pr_debug("Failed to find %s:%s in the cache\n", group, event); + ret = -ENOENT; + } + probe_cache__delete(cache); + + return ret; +} + +static int test__sdt_event(struct test_suite *test __maybe_unused, int subtests __maybe_unused) +{ + int ret = TEST_FAIL; + char __tempdir[] = "./test-buildid-XXXXXX"; + char *tempdir = NULL, *myself = get_self_path(); + + if (myself == NULL || mkdtemp(__tempdir) == NULL) { + pr_debug("Failed to make a tempdir for build-id cache\n"); + goto error; + } + /* Note that buildid_dir must be an absolute path */ + tempdir = realpath(__tempdir, NULL); + if (tempdir == NULL) + goto error_rmdir; + + /* At first, scan itself */ + set_buildid_dir(tempdir); + if (build_id_cache__add_file(myself) < 0) + goto error_rmdir; + + /* Open a cache and make sure the SDT is stored */ + if (search_cached_probe(myself, "sdt_perf", "test_target") < 0) + goto error_rmdir; + + /* TBD: probing on the SDT event and collect logs */ + + /* Call the target and get an event */ + ret = target_function(); + +error_rmdir: + /* Cleanup temporary buildid dir */ + rm_rf(__tempdir); +error: + free(tempdir); + free(myself); + return ret; +} +#else +static int test__sdt_event(struct test_suite *test __maybe_unused, int subtests __maybe_unused) +{ + pr_debug("Skip SDT event test because SDT support is not compiled\n"); + return TEST_SKIP; +} +#endif + +DEFINE_SUITE("Probe SDT events", sdt_event); -- cgit v1.3.1