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 --- drivers/pps/clients/pps-ktimer.c | 87 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 87 insertions(+) create mode 100644 drivers/pps/clients/pps-ktimer.c (limited to 'drivers/pps/clients/pps-ktimer.c') diff --git a/drivers/pps/clients/pps-ktimer.c b/drivers/pps/clients/pps-ktimer.c new file mode 100644 index 000000000..121bd29d8 --- /dev/null +++ b/drivers/pps/clients/pps-ktimer.c @@ -0,0 +1,87 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * pps-ktimer.c -- kernel timer test client + * + * Copyright (C) 2005-2006 Rodolfo Giometti + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include +#include +#include +#include +#include +#include + +/* + * Global variables + */ + +static struct pps_device *pps; +static struct timer_list ktimer; + +/* + * The kernel timer + */ + +static void pps_ktimer_event(struct timer_list *unused) +{ + struct pps_event_time ts; + + /* First of all we get the time stamp... */ + pps_get_ts(&ts); + + pps_event(pps, &ts, PPS_CAPTUREASSERT, NULL); + + mod_timer(&ktimer, jiffies + HZ); +} + +/* + * The PPS info struct + */ + +static struct pps_source_info pps_ktimer_info = { + .name = "ktimer", + .path = "", + .mode = PPS_CAPTUREASSERT | PPS_OFFSETASSERT | + PPS_ECHOASSERT | + PPS_CANWAIT | PPS_TSFMT_TSPEC, + .owner = THIS_MODULE, +}; + +/* + * Module staff + */ + +static void __exit pps_ktimer_exit(void) +{ + dev_dbg(&pps->dev, "ktimer PPS source unregistered\n"); + + timer_delete_sync(&ktimer); + pps_unregister_source(pps); +} + +static int __init pps_ktimer_init(void) +{ + pps = pps_register_source(&pps_ktimer_info, + PPS_CAPTUREASSERT | PPS_OFFSETASSERT); + if (IS_ERR(pps)) { + pr_err("cannot register PPS source\n"); + return PTR_ERR(pps); + } + + timer_setup(&ktimer, pps_ktimer_event, 0); + mod_timer(&ktimer, jiffies + HZ); + + dev_dbg(&pps->dev, "ktimer PPS source registered\n"); + + return 0; +} + +module_init(pps_ktimer_init); +module_exit(pps_ktimer_exit); + +MODULE_AUTHOR("Rodolfo Giometti "); +MODULE_DESCRIPTION("dummy PPS source by using a kernel timer (just for debug)"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1