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/thread-maps-share.c | 100 +++++++++++++++++++++++++++++++++++ 1 file changed, 100 insertions(+) create mode 100644 tools/perf/tests/thread-maps-share.c (limited to 'tools/perf/tests/thread-maps-share.c') diff --git a/tools/perf/tests/thread-maps-share.c b/tools/perf/tests/thread-maps-share.c new file mode 100644 index 000000000..0431bff31 --- /dev/null +++ b/tools/perf/tests/thread-maps-share.c @@ -0,0 +1,100 @@ +// SPDX-License-Identifier: GPL-2.0 +#include "tests.h" +#include "machine.h" +#include "thread.h" +#include "debug.h" + +static int test__thread_maps_share(struct test_suite *test __maybe_unused, int subtest __maybe_unused) +{ + struct machines machines; + struct machine *machine; + + /* thread group */ + struct thread *leader; + struct thread *t1, *t2, *t3; + struct maps *maps; + + /* other process */ + struct thread *other, *other_leader; + struct maps *other_maps; + + /* + * This test create 2 processes abstractions (struct thread) + * with several threads and checks they properly share and + * maintain maps info (struct maps). + * + * thread group (pid: 0, tids: 0, 1, 2, 3) + * other group (pid: 4, tids: 4, 5) + */ + + TEST_ASSERT_VAL("failed to init machines", machines__init(&machines) == 0); + machine = &machines.host; + + /* create process with 4 threads */ + leader = machine__findnew_thread(machine, 0, 0); + t1 = machine__findnew_thread(machine, 0, 1); + t2 = machine__findnew_thread(machine, 0, 2); + t3 = machine__findnew_thread(machine, 0, 3); + + /* and create 1 separated process, without thread leader */ + other = machine__findnew_thread(machine, 4, 5); + + TEST_ASSERT_VAL("failed to create threads", + leader && t1 && t2 && t3 && other); + + maps = thread__maps(leader); + TEST_ASSERT_EQUAL("wrong refcnt", refcount_read(maps__refcnt(maps)), 4); + + /* test the maps pointer is shared */ + TEST_ASSERT_VAL("maps don't match", maps__equal(maps, thread__maps(t1))); + TEST_ASSERT_VAL("maps don't match", maps__equal(maps, thread__maps(t2))); + TEST_ASSERT_VAL("maps don't match", maps__equal(maps, thread__maps(t3))); + + /* + * Verify the other leader was created by previous call. + * It should have shared maps with no change in + * refcnt. + */ + other_leader = machine__find_thread(machine, 4, 4); + TEST_ASSERT_VAL("failed to find other leader", other_leader); + + /* + * Ok, now that all the rbtree related operations were done, + * lets remove all of them from there so that we can do the + * refcounting tests. + */ + machine__remove_thread(machine, leader); + machine__remove_thread(machine, t1); + machine__remove_thread(machine, t2); + machine__remove_thread(machine, t3); + machine__remove_thread(machine, other); + machine__remove_thread(machine, other_leader); + + other_maps = thread__maps(other); + TEST_ASSERT_EQUAL("wrong refcnt", refcount_read(maps__refcnt(other_maps)), 2); + + TEST_ASSERT_VAL("maps don't match", maps__equal(other_maps, thread__maps(other_leader))); + + /* release thread group */ + thread__put(t3); + TEST_ASSERT_EQUAL("wrong refcnt", refcount_read(maps__refcnt(maps)), 3); + + thread__put(t2); + TEST_ASSERT_EQUAL("wrong refcnt", refcount_read(maps__refcnt(maps)), 2); + + thread__put(t1); + TEST_ASSERT_EQUAL("wrong refcnt", refcount_read(maps__refcnt(maps)), 1); + + thread__put(leader); + + /* release other group */ + thread__put(other_leader); + TEST_ASSERT_EQUAL("wrong refcnt", refcount_read(maps__refcnt(other_maps)), 1); + + thread__put(other); + + machines__exit(&machines); + return 0; +} + +DEFINE_SUITE("Share thread maps", thread_maps_share); -- cgit v1.3.1