From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ste-pvt-msa2.bahnhof.se ([213.80.101.71]:5962 "EHLO ste-pvt-msa2.bahnhof.se" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387881AbfC0SNA (ORCPT ); Wed, 27 Mar 2019 14:13:00 -0400 Date: Wed, 27 Mar 2019 19:12:50 +0100 From: Fredrik Noring Subject: [PATCH v2] kbuild: modversions: Fix relative CRC byte order interpretation Message-ID: <20190327181250.GA2563@sx9> References: <20190323184618.GA4916@sx9> <20190324063019.GA2555@sx9> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Sender: linux-kbuild-owner@vger.kernel.org List-ID: To: Masahiro Yamada Cc: Michal Marek , Linux Kbuild mailing list , Ard Biesheuvel , "Maciej W. Rozycki" Fix commit 56067812d5b0 ("kbuild: modversions: add infrastructure for emitting relative CRCs") where CRCs are interpreted in host byte order rather than proper kernel byte order. The bug is conditional on CONFIG_MODULE_REL_CRCS. For example, when loading a BE module into a BE kernel compiled with a LE system, the error "disagrees about version of symbol module_layout" is produced. A message such as "Found checksum D7FA6856 vs module 5668FAD7" will be given with debug enabled, which indicates an obvious endian problem within __kcrctab within the kernel image. The general solution is to use the macro TO_NATIVE, as is done in similar cases throughout modpost.c. With this correction it has been verified that a BE kernel compiled with a LE system accepts BE modules. This change has also been verified with a LE kernel compiled with a LE system, in which case TO_NATIVE returns its value unmodified since the byte orders match. This is by far the common case. Fixes: 56067812d5b0 ("kbuild: modversions: add infrastructure for emitting relative CRCs") Signed-off-by: Fredrik Noring Cc: stable@vger.kernel.org --- Thank you for your review, Masahiro, Changes in v2: - Fix subject spelling mistake. - Note that the bug is conditional on CONFIG_MODULE_REL_CRCS. - Clarify kernel image and __kcrctab compilation details. - Mention verification of matching LE byte order common case. Fredrik --- diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c index 0b0d1080b1c5..f277e116e0eb 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -639,7 +639,7 @@ static void handle_modversions(struct module *mod, struct elf_info *info, info->sechdrs[sym->st_shndx].sh_offset - (info->hdr->e_type != ET_REL ? info->sechdrs[sym->st_shndx].sh_addr : 0); - crc = *crcp; + crc = TO_NATIVE(*crcp); } sym_update_crc(symname + strlen("__crc_"), mod, crc, export);