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Fri, 11 Apr 2025 03:48:15 -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: Td3151a787cba798d Date: Fri, 11 Apr 2025 09:47:51 +0200 From: "Arnd Bergmann" To: "Peter Zijlstra" , "Josh Poimboeuf" Cc: "Arnd Bergmann" , "Masahiro Yamada" , "Rae Moar" , "Shuah Khan" , =?UTF-8?Q?Sergio_Gonz=C3=A1lez_Collado?= , "David Gow" , "Nathan Chancellor" , "Nicolas Schier" , "Mostafa Saleh" , linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org Message-Id: <0073e739-e3aa-4743-ad2d-29d7c969f454@app.fastmail.com> In-Reply-To: <20250411065054.GM9833@noisy.programming.kicks-ass.net> References: <20250328112156.2614513-1-arnd@kernel.org> <20250411065054.GM9833@noisy.programming.kicks-ass.net> Subject: Re: [PATCH] scripts/mksysmap: skip objtool __pfx_ symbols Content-Type: text/plain Content-Transfer-Encoding: 7bit On Fri, Apr 11, 2025, at 08:50, Peter Zijlstra wrote: > On Tue, Apr 08, 2025 at 06:58:49PM -0700, Josh Poimboeuf wrote: >> On Fri, Mar 28, 2025 at 11:48:19AM +0100, Arnd Bergmann wrote: >> >> For example, FineIBT writes code in the __pfx area which can trigger an >> #UD. And we'd want a sane backtrace for that. > > On top of that, clang kcfi builds do a similar thing, they will generate > __cfi_ prefixed symbols. > > And yes, those symbols exist for a reason, there is code there under > various circumstances and backtraces look really weird without these > symbols on -- notably the code in the prefix will be attributed to > whatever symbol comes before, most confusing. > > So yeah, don't remove these symbols, and fix the kunit test. kallsyms already removes some CFI symbol names based on regular expressions: # CFI type identifiers / __kcfi_typeid_/d / __kvm_nvhe___kcfi_typeid_/d / __pi___kcfi_typeid_/d Do you think it should not remove some of them? I ran into another problem with generated symbols that I don't understand yet, and added this line to avoid the build failures: / _GLOBAL__sub_/d This one is 534 characters long: _GLOBAL__sub_I_65535_1_snnnng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nnng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nnnng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nnng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nnnnng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nnng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nnnng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nnng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nng1h2i3j4k5l6m7ng1h2i3j4k5l6m7n Arnd