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 --- samples/watch_queue/.gitignore | 2 + samples/watch_queue/Makefile | 4 + samples/watch_queue/watch_test.c | 192 +++++++++++++++++++++++++++++++++++++++ 3 files changed, 198 insertions(+) create mode 100644 samples/watch_queue/.gitignore create mode 100644 samples/watch_queue/Makefile create mode 100644 samples/watch_queue/watch_test.c (limited to 'samples/watch_queue') diff --git a/samples/watch_queue/.gitignore b/samples/watch_queue/.gitignore new file mode 100644 index 000000000..823b351d3 --- /dev/null +++ b/samples/watch_queue/.gitignore @@ -0,0 +1,2 @@ +# SPDX-License-Identifier: GPL-2.0-only +/watch_test diff --git a/samples/watch_queue/Makefile b/samples/watch_queue/Makefile new file mode 100644 index 000000000..c0db3a6bc --- /dev/null +++ b/samples/watch_queue/Makefile @@ -0,0 +1,4 @@ +# SPDX-License-Identifier: GPL-2.0-only +userprogs-always-y += watch_test + +userccflags += -I usr/include diff --git a/samples/watch_queue/watch_test.c b/samples/watch_queue/watch_test.c new file mode 100644 index 000000000..24cf7d7a1 --- /dev/null +++ b/samples/watch_queue/watch_test.c @@ -0,0 +1,192 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Use watch_queue API to watch for notifications. + * + * Copyright (C) 2020 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + */ + +#define _GNU_SOURCE +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +// Work around glibc header silliness +#undef AT_RENAME_NOREPLACE +#undef AT_RENAME_EXCHANGE +#undef AT_RENAME_WHITEOUT + +#include +#include +#include + +#ifndef KEYCTL_WATCH_KEY +#define KEYCTL_WATCH_KEY -1 +#endif +#ifndef __NR_keyctl +#define __NR_keyctl -1 +#endif + +#define BUF_SIZE 256 + +static long keyctl_watch_key(int key, int watch_fd, int watch_id) +{ + return syscall(__NR_keyctl, KEYCTL_WATCH_KEY, key, watch_fd, watch_id); +} + +static const char *key_subtypes[256] = { + [NOTIFY_KEY_INSTANTIATED] = "instantiated", + [NOTIFY_KEY_UPDATED] = "updated", + [NOTIFY_KEY_LINKED] = "linked", + [NOTIFY_KEY_UNLINKED] = "unlinked", + [NOTIFY_KEY_CLEARED] = "cleared", + [NOTIFY_KEY_REVOKED] = "revoked", + [NOTIFY_KEY_INVALIDATED] = "invalidated", + [NOTIFY_KEY_SETATTR] = "setattr", +}; + +static void saw_key_change(struct watch_notification *n, size_t len) +{ + struct key_notification *k = (struct key_notification *)n; + + if (len != sizeof(struct key_notification)) { + fprintf(stderr, "Incorrect key message length\n"); + return; + } + + printf("KEY %08x change=%u[%s] aux=%u\n", + k->key_id, n->subtype, key_subtypes[n->subtype], k->aux); +} + +/* + * Consume and display events. + */ +static void consumer(int fd) +{ + unsigned char buffer[433], *p, *end; + union { + struct watch_notification n; + unsigned char buf1[128]; + } n; + ssize_t buf_len; + + for (;;) { + buf_len = read(fd, buffer, sizeof(buffer)); + if (buf_len == -1) { + perror("read"); + exit(1); + } + + if (buf_len == 0) { + printf("-- END --\n"); + return; + } + + if (buf_len > sizeof(buffer)) { + fprintf(stderr, "Read buffer overrun: %zd\n", buf_len); + return; + } + + printf("read() = %zd\n", buf_len); + + p = buffer; + end = buffer + buf_len; + while (p < end) { + size_t largest, len; + + largest = end - p; + if (largest > 128) + largest = 128; + if (largest < sizeof(struct watch_notification)) { + fprintf(stderr, "Short message header: %zu\n", largest); + return; + } + memcpy(&n, p, largest); + + printf("NOTIFY[%03zx]: ty=%06x sy=%02x i=%08x\n", + p - buffer, n.n.type, n.n.subtype, n.n.info); + + len = n.n.info & WATCH_INFO_LENGTH; + if (len < sizeof(n.n) || len > largest) { + fprintf(stderr, "Bad message length: %zu/%zu\n", len, largest); + exit(1); + } + + switch (n.n.type) { + case WATCH_TYPE_META: + switch (n.n.subtype) { + case WATCH_META_REMOVAL_NOTIFICATION: + printf("REMOVAL of watchpoint %08x\n", + (n.n.info & WATCH_INFO_ID) >> + WATCH_INFO_ID__SHIFT); + break; + case WATCH_META_LOSS_NOTIFICATION: + printf("-- LOSS --\n"); + break; + default: + printf("other meta record\n"); + break; + } + break; + case WATCH_TYPE_KEY_NOTIFY: + saw_key_change(&n.n, len); + break; + default: + printf("other type\n"); + break; + } + + p += len; + } + } +} + +static struct watch_notification_filter filter = { + .nr_filters = 1, + .filters = { + [0] = { + .type = WATCH_TYPE_KEY_NOTIFY, + .subtype_filter[0] = UINT_MAX, + }, + }, +}; + +int main(int argc, char **argv) +{ + int pipefd[2], fd; + + if (pipe2(pipefd, O_NOTIFICATION_PIPE) == -1) { + perror("pipe2"); + exit(1); + } + fd = pipefd[0]; + + if (ioctl(fd, IOC_WATCH_QUEUE_SET_SIZE, BUF_SIZE) == -1) { + perror("watch_queue(size)"); + exit(1); + } + + if (ioctl(fd, IOC_WATCH_QUEUE_SET_FILTER, &filter) == -1) { + perror("watch_queue(filter)"); + exit(1); + } + + if (keyctl_watch_key(KEY_SPEC_SESSION_KEYRING, fd, 0x01) == -1) { + perror("keyctl"); + exit(1); + } + + if (keyctl_watch_key(KEY_SPEC_USER_KEYRING, fd, 0x02) == -1) { + perror("keyctl"); + exit(1); + } + + consumer(fd); + exit(0); +} -- cgit v1.3.1