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/testing/selftests/kcmp/.gitignore | 3 + tools/testing/selftests/kcmp/Makefile | 9 ++ tools/testing/selftests/kcmp/kcmp_test.c | 168 +++++++++++++++++++++++++++++++ 3 files changed, 180 insertions(+) create mode 100644 tools/testing/selftests/kcmp/.gitignore create mode 100644 tools/testing/selftests/kcmp/Makefile create mode 100644 tools/testing/selftests/kcmp/kcmp_test.c (limited to 'tools/testing/selftests/kcmp') diff --git a/tools/testing/selftests/kcmp/.gitignore b/tools/testing/selftests/kcmp/.gitignore new file mode 100644 index 000000000..38ccdfe80 --- /dev/null +++ b/tools/testing/selftests/kcmp/.gitignore @@ -0,0 +1,3 @@ +# SPDX-License-Identifier: GPL-2.0-only +kcmp_test +kcmp-test-file diff --git a/tools/testing/selftests/kcmp/Makefile b/tools/testing/selftests/kcmp/Makefile new file mode 100644 index 000000000..59a1e5379 --- /dev/null +++ b/tools/testing/selftests/kcmp/Makefile @@ -0,0 +1,9 @@ +# SPDX-License-Identifier: GPL-2.0-only +CFLAGS += $(KHDR_INCLUDES) + +TEST_GEN_PROGS := kcmp_test + +EXTRA_CLEAN := $(OUTPUT)/kcmp-test-file + +include ../lib.mk + diff --git a/tools/testing/selftests/kcmp/kcmp_test.c b/tools/testing/selftests/kcmp/kcmp_test.c new file mode 100644 index 000000000..79aa438b7 --- /dev/null +++ b/tools/testing/selftests/kcmp/kcmp_test.c @@ -0,0 +1,168 @@ +// SPDX-License-Identifier: GPL-2.0 +#define _GNU_SOURCE + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include +#include +#include +#include +#include + +#include "kselftest.h" + +static long sys_kcmp(int pid1, int pid2, int type, unsigned long fd1, unsigned long fd2) +{ + return syscall(__NR_kcmp, pid1, pid2, type, fd1, fd2); +} + +static const unsigned int duped_num = 64; + +int main(int argc, char **argv) +{ + const char kpath[] = "kcmp-test-file"; + struct kcmp_epoll_slot epoll_slot; + struct epoll_event ev; + int pid1, pid2; + int pipefd[2]; + int fd1, fd2; + int epollfd; + int status; + int fddup; + + fd1 = open(kpath, O_RDWR | O_CREAT | O_TRUNC, 0644); + pid1 = getpid(); + + if (fd1 < 0) { + perror("Can't create file"); + ksft_exit_fail(); + } + + if (pipe(pipefd)) { + perror("Can't create pipe"); + ksft_exit_fail(); + } + + epollfd = epoll_create1(0); + if (epollfd < 0) { + perror("epoll_create1 failed"); + ksft_exit_fail(); + } + + memset(&ev, 0xff, sizeof(ev)); + ev.events = EPOLLIN | EPOLLOUT; + + if (epoll_ctl(epollfd, EPOLL_CTL_ADD, pipefd[0], &ev)) { + perror("epoll_ctl failed"); + ksft_exit_fail(); + } + + fddup = dup2(pipefd[1], duped_num); + if (fddup < 0) { + perror("dup2 failed"); + ksft_exit_fail(); + } + + if (epoll_ctl(epollfd, EPOLL_CTL_ADD, fddup, &ev)) { + perror("epoll_ctl failed"); + ksft_exit_fail(); + } + close(fddup); + + pid2 = fork(); + if (pid2 < 0) { + perror("fork failed"); + ksft_exit_fail(); + } + + if (!pid2) { + int pid2 = getpid(); + int ret; + + ksft_print_header(); + ksft_set_plan(3); + + fd2 = open(kpath, O_RDWR); + if (fd2 < 0) { + perror("Can't open file"); + ksft_exit_fail(); + } + + /* An example of output and arguments */ + printf("pid1: %6d pid2: %6d FD: %2ld FILES: %2ld VM: %2ld " + "FS: %2ld SIGHAND: %2ld IO: %2ld SYSVSEM: %2ld " + "INV: %2ld\n", + pid1, pid2, + sys_kcmp(pid1, pid2, KCMP_FILE, fd1, fd2), + sys_kcmp(pid1, pid2, KCMP_FILES, 0, 0), + sys_kcmp(pid1, pid2, KCMP_VM, 0, 0), + sys_kcmp(pid1, pid2, KCMP_FS, 0, 0), + sys_kcmp(pid1, pid2, KCMP_SIGHAND, 0, 0), + sys_kcmp(pid1, pid2, KCMP_IO, 0, 0), + sys_kcmp(pid1, pid2, KCMP_SYSVSEM, 0, 0), + + /* This one should fail */ + sys_kcmp(pid1, pid2, KCMP_TYPES + 1, 0, 0)); + + /* This one should return same fd */ + ret = sys_kcmp(pid1, pid2, KCMP_FILE, fd1, fd1); + if (ret) { + printf("FAIL: 0 expected but %d returned (%s)\n", + ret, strerror(errno)); + ksft_inc_fail_cnt(); + ret = -1; + } else { + printf("PASS: 0 returned as expected\n"); + ksft_inc_pass_cnt(); + } + + /* Compare with self */ + ret = sys_kcmp(pid1, pid1, KCMP_VM, 0, 0); + if (ret) { + printf("FAIL: 0 expected but %d returned (%s)\n", + ret, strerror(errno)); + ksft_inc_fail_cnt(); + ret = -1; + } else { + printf("PASS: 0 returned as expected\n"); + ksft_inc_pass_cnt(); + } + + /* Compare epoll target */ + epoll_slot = (struct kcmp_epoll_slot) { + .efd = epollfd, + .tfd = duped_num, + .toff = 0, + }; + ret = sys_kcmp(pid1, pid1, KCMP_EPOLL_TFD, pipefd[1], + (unsigned long)(void *)&epoll_slot); + if (ret) { + printf("FAIL: 0 expected but %d returned (%s)\n", + ret, strerror(errno)); + ksft_inc_fail_cnt(); + ret = -1; + } else { + printf("PASS: 0 returned as expected\n"); + ksft_inc_pass_cnt(); + } + + + if (ret) + ksft_exit_fail(); + else + ksft_exit_pass(); + } + + waitpid(pid2, &status, P_ALL); + + return 0; +} -- cgit v1.3.1