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/bench/futex.h | 151 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 151 insertions(+) create mode 100644 tools/perf/bench/futex.h (limited to 'tools/perf/bench/futex.h') diff --git a/tools/perf/bench/futex.h b/tools/perf/bench/futex.h new file mode 100644 index 000000000..fcb72d682 --- /dev/null +++ b/tools/perf/bench/futex.h @@ -0,0 +1,151 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Glibc independent futex library for testing kernel functionality. + * Shamelessly stolen from Darren Hart + * http://git.kernel.org/cgit/linux/kernel/git/dvhart/futextest.git/ + */ + +#ifndef _FUTEX_H +#define _FUTEX_H + +#include +#include +#include +#include +#include + +struct bench_futex_parameters { + bool silent; + bool fshared; + bool mlockall; + bool multi; /* lock-pi */ + bool pi; /* requeue-pi */ + bool broadcast; /* requeue */ + unsigned int runtime; /* seconds*/ + unsigned int nthreads; + unsigned int nfutexes; + unsigned int nwakes; + unsigned int nrequeue; + int nbuckets; +}; + +/** + * futex_syscall() - SYS_futex syscall wrapper + * @uaddr: address of first futex + * @op: futex op code + * @val: typically expected value of uaddr, but varies by op + * @timeout: typically an absolute struct timespec (except where noted + * otherwise). Overloaded by some ops + * @uaddr2: address of second futex for some ops + * @val3: varies by op + * @opflags: flags to be bitwise OR'd with op, such as FUTEX_PRIVATE_FLAG + * + * futex_syscall() is used by all the following futex op wrappers. It can also be + * used for misuse and abuse testing. Generally, the specific op wrappers + * should be used instead. + * + * These argument descriptions are the defaults for all + * like-named arguments in the following wrappers except where noted below. + */ +static inline int +futex_syscall(volatile u_int32_t *uaddr, int op, u_int32_t val, struct timespec *timeout, + volatile u_int32_t *uaddr2, int val3, int opflags) +{ + return syscall(SYS_futex, uaddr, op | opflags, val, timeout, uaddr2, val3); +} + +static inline int +futex_syscall_nr_requeue(volatile u_int32_t *uaddr, int op, u_int32_t val, int nr_requeue, + volatile u_int32_t *uaddr2, int val3, int opflags) +{ + return syscall(SYS_futex, uaddr, op | opflags, val, nr_requeue, uaddr2, val3); +} + +/** + * futex_wait() - block on uaddr with optional timeout + * @timeout: relative timeout + */ +static inline int +futex_wait(u_int32_t *uaddr, u_int32_t val, struct timespec *timeout, int opflags) +{ + return futex_syscall(uaddr, FUTEX_WAIT, val, timeout, NULL, 0, opflags); +} + +/** + * futex_wake() - wake one or more tasks blocked on uaddr + * @nr_wake: wake up to this many tasks + */ +static inline int +futex_wake(u_int32_t *uaddr, int nr_wake, int opflags) +{ + return futex_syscall(uaddr, FUTEX_WAKE, nr_wake, NULL, NULL, 0, opflags); +} + +/** + * futex_lock_pi() - block on uaddr as a PI mutex + */ +static inline int +futex_lock_pi(u_int32_t *uaddr, struct timespec *timeout, int opflags) +{ + return futex_syscall(uaddr, FUTEX_LOCK_PI, 0, timeout, NULL, 0, opflags); +} + +/** + * futex_unlock_pi() - release uaddr as a PI mutex, waking the top waiter + */ +static inline int +futex_unlock_pi(u_int32_t *uaddr, int opflags) +{ + return futex_syscall(uaddr, FUTEX_UNLOCK_PI, 0, NULL, NULL, 0, opflags); +} + +/** +* futex_cmp_requeue() - requeue tasks from uaddr to uaddr2 +* @nr_wake: wake up to this many tasks +* @nr_requeue: requeue up to this many tasks +*/ +static inline int +futex_cmp_requeue(u_int32_t *uaddr, u_int32_t val, u_int32_t *uaddr2, int nr_wake, + int nr_requeue, int opflags) +{ + return futex_syscall_nr_requeue(uaddr, FUTEX_CMP_REQUEUE, nr_wake, nr_requeue, uaddr2, + val, opflags); +} + +/** + * futex_wait_requeue_pi() - block on uaddr and prepare to requeue to uaddr2 + * @uaddr: non-PI futex source + * @uaddr2: PI futex target + * + * This is the first half of the requeue_pi mechanism. It shall always be + * paired with futex_cmp_requeue_pi(). + */ +static inline int +futex_wait_requeue_pi(u_int32_t *uaddr, u_int32_t val, u_int32_t *uaddr2, + struct timespec *timeout, int opflags) +{ + return futex_syscall(uaddr, FUTEX_WAIT_REQUEUE_PI, val, timeout, uaddr2, 0, + opflags); +} + +/** + * futex_cmp_requeue_pi() - requeue tasks from uaddr to uaddr2 + * @uaddr: non-PI futex source + * @uaddr2: PI futex target + * @nr_requeue: requeue up to this many tasks + * + * This is the second half of the requeue_pi mechanism. It shall always be + * paired with futex_wait_requeue_pi(). The first waker is always awoken. + */ +static inline int +futex_cmp_requeue_pi(u_int32_t *uaddr, u_int32_t val, u_int32_t *uaddr2, + int nr_requeue, int opflags) +{ + return futex_syscall_nr_requeue(uaddr, FUTEX_CMP_REQUEUE_PI, 1, nr_requeue, uaddr2, + val, opflags); +} + +void futex_set_nbuckets_param(struct bench_futex_parameters *params); +void futex_print_nbuckets(struct bench_futex_parameters *params); + +#endif /* _FUTEX_H */ -- cgit v1.3.1