From mboxrd@z Thu Jan 1 00:00:00 1970 From: Coiby Xu Date: Fri, 25 Feb 2022 11:46:41 +0800 Subject: Compile error ppc64le: Cannot find symbol for section 11: .text.unlikely. In-Reply-To: References: <20211124134743.GB11728@MiWiFi-R3L-srv> <20211201021926.3xfabf5zbzidvrwa@Rk> Message-ID: <20220225034641.zvg3jfxu3vhazdms@Rk> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: kexec@lists.infradead.org On Fri, Dec 03, 2021 at 04:54:19PM +0100, Veronika Kabatova wrote: >On Wed, Dec 1, 2021 at 3:20 AM Coiby Xu wrote: >> >> On Wed, Nov 24, 2021 at 09:47:43PM +0800, Baoquan He wrote: >> >On 11/24/21 at 01:47pm, Veronika Kabatova wrote: >> >> Hi, >> >> >> >> for a while we've been seen the following error when compiling >> >> the mainline kernel with gcc 11.2 and binutils 2.37: >> >> >> >> 00:02:32 Cannot find symbol for section 11: .text.unlikely. >> >> 00:02:32 kernel/kexec_file.o: failed >> >> 00:02:32 make[3]: *** [scripts/Makefile.build:287: kernel/kexec_file.o] Error 1 >> >> 00:02:32 make[3]: *** Deleting file 'kernel/kexec_file.o' >> >> 00:02:32 make[2]: *** [Makefile:1846: kernel] Error 2 >> >> 00:02:32 make[2]: *** Waiting for unfinished jobs.... >> >> >> >> The error only happens with ppc64le. I've tested this with cross >> >> compilation, but the only reference to the error I found suggests >> >> the same happens with the native compiles as well: >> >> >> >> https://github.com/groeck/linux-build-test/commit/142cbefbc0d37962c9a6c7f28ee415ecd5fd1e98 >> >> >> >> In case it matters, the config used is the Fedora config with >> >> kselftest options enabled, which you can grab from >> >> >> >> https://gitlab.com/redhat/red-hat-ci-tools/kernel/cki-internal-pipelines/cki-trusted-contributors/-/jobs/1760752896/artifacts/raw/artifacts/kernel-mainline.kernel.org-ppc64le-e4e737bb5c170df6135a127739a9e6148ee3da82.config >> >> >> >> >> >> I've reached out to the Fedora compiler folks and Nick Clifton >> >> suggested this is a problem with the kernel: >> >> >> >> This message comes from the recordmcount tool, which is part of the kernel >> >> sources: >> >> >> >> linux/scripts/recordmcount.[ch] >> >> >> >> It appears to be triggered when a compiler update causes code to be >> >> rearranged. The problem has been reported before in various forums, >> >> but in particular I found this reference: >> >> >> >> https://lore.kernel.org/lkml/20201204165742.3815221-2-arnd at kernel.org/ >> >> >> >> The point of which to me at least is that this is a kernel issue rather than >> >> a compiler issue. Ie there must be some weak symbols in kexec_file.o file >> >> which need to be moved elsewhere. >> > >> >It could be arch_kexec_kernel_verify_sig() in kernel/kexec_file.c which >> >is __weak, but not implemented in any ARCH. If true, this has been >> >pointed out by Eric in one patch thread from Coiby. >> > >> >[PATCH v3 1/3] kexec: clean up arch_kexec_kernel_verify_sig >> >http://lkml.kernel.org/r/20211018083137.338757-2-coxu at redhat.com >> > >> >Maybe Coiby can fetch above config file and run the test to check. >> >> "[PATCH v3 1/3] kexec: clean up arch_kexec_kernel_verify_sig" alone >> would fix the error. If I turn arch_kexec_apply_relocations{_add,} into Sorry I meant "alone won't fix the error". >> static function, the error would be gone. As attached is the patch would >> make this error disappear. >> > >Thank you! I can confirm the attached patch fixes the problem. > > >Veronika > >> However, s390 and x86 have its own implementation of >> arch_kexec_apply_relocations_add. This makes it looks like to be gcc's >> issue. Based on the above point and further investigation, I think the root cause is find_secsym_ndx in linux/scripts/recordmcount.h, /* * Find a symbol in the given section, to be used as the base for relocating * the table of offsets of calls to mcount. A local or global symbol suffices, * but avoid a Weak symbol because it may be overridden; the change in value * would invalidate the relocations of the offsets of the calls to mcount. * Often the found symbol will be the unnamed local symbol generated by * GNU 'as' for the start of each section. For example: * Num: Value Size Type Bind Vis Ndx Name * 2: 00000000 0 SECTION LOCAL DEFAULT 1 */ static int find_secsym_ndx(unsigned const txtndx, char const *const txtname, uint_t *const recvalp, unsigned int *sym_index, Elf_Shdr const *const symhdr, Elf32_Word const *symtab, Elf32_Word const *symtab_shndx, Elf_Ehdr const *const ehdr) { ... if (txtndx == get_symindex(symp, symtab, symtab_shndx) /* avoid STB_WEAK */ fprintf(stderr, "Cannot find symbol for section %u: %s.\n", txtndx, txtname); This function prints the above warning after failing to find arch_kexec_kernel_verify_sig or arch_kexec_apply_relocations{_add,} in section 11: .text.unlikely. because it ignores the weak symbol and ppc64le doesn't its arch implementations of these functions. I'll see if I can fix it in linux/scripts/recordmcount.h. >> >> >> > >> >Thanks >> >Baoquan >> > >> >> -- >> Best regards, >> Coiby > -- Best regards, Coiby