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 --- lib/ratelimit.c | 105 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 105 insertions(+) create mode 100644 lib/ratelimit.c (limited to 'lib/ratelimit.c') diff --git a/lib/ratelimit.c b/lib/ratelimit.c new file mode 100644 index 000000000..e2d65d3b1 --- /dev/null +++ b/lib/ratelimit.c @@ -0,0 +1,105 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * ratelimit.c - Do something with rate limit. + * + * Isolated from kernel/printk.c by Dave Young + * + * 2008-05-01 rewrite the function and use a ratelimit_state data struct as + * parameter. Now every user can use their own standalone ratelimit_state. + */ + +#include +#include +#include + +/* + * __ratelimit - rate limiting + * @rs: ratelimit_state data + * @func: name of calling function + * + * This enforces a rate limit: not more than @rs->burst callbacks + * in every @rs->interval + * + * RETURNS: + * 0 means callbacks will be suppressed. + * 1 means go ahead and do it. + */ +int ___ratelimit(struct ratelimit_state *rs, const char *func) +{ + /* Paired with WRITE_ONCE() in .proc_handler(). + * Changing two values separately could be inconsistent + * and some message could be lost. (See: net_ratelimit_state). + */ + int interval = READ_ONCE(rs->interval); + int burst = READ_ONCE(rs->burst); + unsigned long flags; + int ret = 0; + + /* + * Zero interval says never limit, otherwise, non-positive burst + * says always limit. + */ + if (interval <= 0 || burst <= 0) { + WARN_ONCE(interval < 0 || burst < 0, "Negative interval (%d) or burst (%d): Uninitialized ratelimit_state structure?\n", interval, burst); + ret = interval == 0 || burst > 0; + if (!(READ_ONCE(rs->flags) & RATELIMIT_INITIALIZED) || (!interval && !burst) || + !raw_spin_trylock_irqsave(&rs->lock, flags)) + goto nolock_ret; + + /* Force re-initialization once re-enabled. */ + rs->flags &= ~RATELIMIT_INITIALIZED; + goto unlock_ret; + } + + /* + * If we contend on this state's lock then just check if + * the current burst is used or not. It might cause + * false positive when we are past the interval and + * the current lock owner is just about to reset it. + */ + if (!raw_spin_trylock_irqsave(&rs->lock, flags)) { + if (READ_ONCE(rs->flags) & RATELIMIT_INITIALIZED && + atomic_read(&rs->rs_n_left) > 0 && atomic_dec_return(&rs->rs_n_left) >= 0) + ret = 1; + goto nolock_ret; + } + + if (!(rs->flags & RATELIMIT_INITIALIZED)) { + rs->begin = jiffies; + rs->flags |= RATELIMIT_INITIALIZED; + atomic_set(&rs->rs_n_left, rs->burst); + } + + if (time_is_before_jiffies(rs->begin + interval)) { + int m; + + /* + * Reset rs_n_left ASAP to reduce false positives + * in parallel calls, see above. + */ + atomic_set(&rs->rs_n_left, rs->burst); + rs->begin = jiffies; + + if (!(rs->flags & RATELIMIT_MSG_ON_RELEASE)) { + m = ratelimit_state_reset_miss(rs); + if (m) { + printk_deferred(KERN_WARNING + "%s: %d callbacks suppressed\n", func, m); + } + } + } + + /* Note that the burst might be taken by a parallel call. */ + if (atomic_read(&rs->rs_n_left) > 0 && atomic_dec_return(&rs->rs_n_left) >= 0) + ret = 1; + +unlock_ret: + raw_spin_unlock_irqrestore(&rs->lock, flags); + +nolock_ret: + if (!ret) + ratelimit_state_inc_miss(rs); + + return ret; +} +EXPORT_SYMBOL(___ratelimit); -- cgit v1.3.1