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Fri, 28 Mar 2025 07:23:53 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ThreadId: Tc75a1b42c9faed5d Date: Fri, 28 Mar 2025 12:23:33 +0100 From: "Arnd Bergmann" To: "Peter Zijlstra" Cc: =?UTF-8?Q?Sergio_Gonz=C3=A1lez_Collado?= , "Brendan Higgins" , "David Gow" , "Miguel Ojeda" , "Alex Gaynor" , linux-kselftest@vger.kernel.org, kunit-dev@googlegroups.com, "Dave Hansen" , "H. Peter Anvin" , "Josh Poimboeuf" , "Boqun Feng" , "Gary Guo" , =?UTF-8?Q?Bj=C3=B6rn_Roy_Baron?= , "Benno Lossin" , "Andreas Hindborg" , "Alice Ryhl" , "David Rheinsberg" , rust-for-linux@vger.kernel.org, "Shuah Khan" , ricardo.marliere@suse.com, "Thomas Gleixner" , "Ingo Molnar" , "Borislav Petkov" , "Martin Rodriguez Reboredo" , linux-kernel@vger.kernel.org Message-Id: <06639d9d-13b7-4d9a-a734-a430e91c1c27@app.fastmail.com> In-Reply-To: <20250327135847.GE31358@noisy.programming.kicks-ass.net> References: <66f3f697-530a-4d22-979a-1472c8e8de3a@app.fastmail.com> <20250327135847.GE31358@noisy.programming.kicks-ass.net> Subject: Re: Symbol too long for allsyms warnings on KSYM_NAME_LEN Content-Type: text/plain Content-Transfer-Encoding: 7bit On Thu, Mar 27, 2025, at 14:58, Peter Zijlstra wrote: > On Thu, Mar 27, 2025 at 09:38:46AM +0100, Arnd Bergmann wrote: >> My randconfig builds sometimes (around one in every 700 configs) run >> into this warning on x86: >> >> Symbol __pfx_snnnng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nnng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nnnng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nnng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nnnnng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nnng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nnnng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nnng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nng1h2i3j4k5l6m7ng1h2i3j4k5l6m7n too long for kallsyms (517 >= 512). >> Please increase KSYM_NAME_LEN both in kernel and kallsyms.c >> >> The check that gets triggered was added in commit c104c16073b >> ("Kunit to check the longest symbol length"), see >> https://lore.kernel.org/all/20241117195923.222145-1-sergio.collado@gmail.com/ >> >> and the overlong identifier seems to be the result of objtool adding >> the six-byte "__pfx_" string to a symbol in elf_create_prefix_symbol() >> when CONFIG_FUNCTION_PADDING_CFI is set. >> >> I think the suggestion to "Please increase KSYM_NAME_LEN both in >> kernel and kallsyms.c" is misleading here and should probably be >> changed. I don't know if this something that objtool should work >> around, or something that needs to be adapted in the test. > > Probably test needs to be fixed; objtool can't really do anything here, > it just take the existing symname and prefixes it. I found a workaround that avoids the problem for me now, see https://lore.kernel.org/linux-kbuild/20250328112156.2614513-1-arnd@kernel.org/ Arnd