From patchwork Thu May 5 14:43:14 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dave Martin X-Patchwork-Id: 1361 Return-Path: Delivered-To: unknown Received: from imap.gmail.com (74.125.159.109) by localhost6.localdomain6 with IMAP4-SSL; 08 Jun 2011 14:51:22 -0000 Delivered-To: patches@linaro.org Received: by 10.224.184.145 with SMTP id ck17cs100541qab; Thu, 5 May 2011 07:43:36 -0700 (PDT) Received: by 10.216.235.95 with SMTP id t73mr2548733weq.10.1304606616069; Thu, 05 May 2011 07:43:36 -0700 (PDT) Received: from mail-wy0-f178.google.com (mail-wy0-f178.google.com [74.125.82.178]) by mx.google.com with ESMTPS id f34si6153334wen.145.2011.05.05.07.43.35 (version=TLSv1/SSLv3 cipher=OTHER); Thu, 05 May 2011 07:43:36 -0700 (PDT) Received-SPF: neutral (google.com: 74.125.82.178 is neither permitted nor denied by best guess record for domain of dave.martin@linaro.org) client-ip=74.125.82.178; Authentication-Results: mx.google.com; spf=neutral (google.com: 74.125.82.178 is neither permitted nor denied by best guess record for domain of dave.martin@linaro.org) smtp.mail=dave.martin@linaro.org Received: by mail-wy0-f178.google.com with SMTP id 33so2052742wyb.37 for ; Thu, 05 May 2011 07:43:35 -0700 (PDT) Received: by 10.227.7.18 with SMTP id b18mr197380wbb.103.1304606615271; Thu, 05 May 2011 07:43:35 -0700 (PDT) Received: from e200948.peterhouse.linaro.org (fw-lnat.cambridge.arm.com [217.140.96.63]) by mx.google.com with ESMTPS id w25sm1395171wbd.56.2011.05.05.07.43.33 (version=SSLv3 cipher=OTHER); Thu, 05 May 2011 07:43:34 -0700 (PDT) From: Dave Martin To: linux-arm-kernel@lists.infradead.org Cc: patches@linaro.org, Catalin Marinas , Nicolas Pitre Subject: [PATCH] ARM: Thumb-2: Relax relocation requirements for non-function symbols Date: Thu, 5 May 2011 15:43:14 +0100 Message-Id: <1304606594-17211-1-git-send-email-dave.martin@linaro.org> X-Mailer: git-send-email 1.7.4.1 The "Thumb bit" of a symbol is only really meaningful for function symbols (STT_FUNC). However, sometimes a branch is relocated against a non-function symbol; for example, PC-relative branches to anonymous assembler local symbols are typically fixed up against the start-of-section symbol, which is not a function symbol. Some inline assembler generates references of this type, such as fixup code generated by macros in . The existing relocation code for R_ARM_THM_CALL/R_ARM_THM_JUMP24 interprets this case as an error, because the target symbol appears to be an ARM symbol; but this is really not the case, since the target symbol is just a base in these cases. The addend defines the precise offset to the target location, but since the addend is encoded in a non-interworking Thumb branch instruction, there is no explicit Thumb bit in the addend. Because these instructions never interwork, the implied Thumb bit in the addend is 1, and the destination is Thumb by definition. This patch removes the extraneous Thumb bit check for non-function symbols, enabling modules containing the affected relocation types to be loaded. No modification to the actual relocation code is required, since this code does not take bit[0] of the location->destination offset into account in any case. Function symbols are always checked for interworking conflicts, as before. Signed-off-by: Dave Martin --- arch/arm/kernel/module.c | 13 +++++++++++-- 1 files changed, 11 insertions(+), 2 deletions(-) diff --git a/arch/arm/kernel/module.c b/arch/arm/kernel/module.c index fee7c36..016d6a0 100644 --- a/arch/arm/kernel/module.c +++ b/arch/arm/kernel/module.c @@ -193,8 +193,17 @@ apply_relocate(Elf32_Shdr *sechdrs, const char *strtab, unsigned int symindex, offset -= 0x02000000; offset += sym->st_value - loc; - /* only Thumb addresses allowed (no interworking) */ - if (!(offset & 1) || + /* + * For function symbols, only Thumb addresses are + * allowed (no interworking). + * + * For non-function symbols, the destination + * has no specific ARM/Thumb disposition, so + * the branch is resolved under the assumption + * that interworking is not required. + */ + if ((ELF32_ST_TYPE(sym->st_info) == STT_FUNC && + !(offset & 1)) || offset <= (s32)0xff000000 || offset >= (s32)0x01000000) { pr_err("%s: section %u reloc %u sym '%s': relocation %u out of range (%#lx -> %#x)\n",