From patchwork Wed Sep 20 16:29:04 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sergey Senozhatsky X-Patchwork-Id: 9961845 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id E82826056A for ; Wed, 20 Sep 2017 16:31:37 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D9A9229198 for ; Wed, 20 Sep 2017 16:31:37 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id CE9332919B; Wed, 20 Sep 2017 16:31:37 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.3 required=2.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED, DKIM_SIGNED, FREEMAIL_FROM, RCVD_IN_DNSWL_HI, RCVD_IN_SORBS_SPAM, T_DKIM_INVALID autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 10B5129198 for ; Wed, 20 Sep 2017 16:31:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751716AbdITQ3k (ORCPT ); Wed, 20 Sep 2017 12:29:40 -0400 Received: from mail-pf0-f195.google.com ([209.85.192.195]:34992 "EHLO mail-pf0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751000AbdITQ3h (ORCPT ); Wed, 20 Sep 2017 12:29:37 -0400 Received: by mail-pf0-f195.google.com with SMTP id i23so1384798pfi.2; Wed, 20 Sep 2017 09:29:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=y7ek0k6yNfVDcFDcWSjt90y7isFoahrknAhAcPVdQLE=; b=odRRVgYd1jq1sdQF0VOWPjdANOEOyKuA1HOfhF89TuiDihNbu0NGGHlgo3jL+vMQBP sLvUFxigHH/abAhu7zDp3w/X5FA2DHMRAPhvL5KFzjli7wA3Hg7tyQD/Qec0OSWK7GGn 5FbnWtqSybPrDqsGiJSFiM1dcDvUqgJ/46nHsqvwfoO5btbf3oTILmBefIvuFHWCvsVe SLn0y96cuThxbH7VK7mJU8HDnh6hdJiGXx95aqnu223nR05xjuj92k0eE9/uTQT5DJTX y7QVxoIMT9ML+Ns9i+rlCv1tPkGhlct7kCvT8F0pmXy8+W1Jq184kqdt+OReXjQbPAoT YjUQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=y7ek0k6yNfVDcFDcWSjt90y7isFoahrknAhAcPVdQLE=; b=EkSO+l3afN38un0dmLetlreszDuDtA0YspgCO/G65mrrcq5KbsxGYHrQI8PLEeedfv 8pXunQVlok0BoAzaggPLX0SAHQNrattE4pnzKBTMBohrjovWI4yNFMU2Vdvq++B58DHv XlML5lGEMDCMzPIrjvbVoYYIbqbpYwFfwF+T8Bh1YA04r/THNBOko6NWtKJyQtvLL/1R HlBuCG3ONdkp/852Yq1svbYhGoG8NbJGA4OuGzuC6UXhw6VdcFHxZfiVj4taR2TUvugU ZgF/23pRKyIrRg6gNG0/KUChKWu3fW0z1sr3EwzgKP3UEeRBmug+OZeqodekuMnKT+Vy f5vg== X-Gm-Message-State: AHPjjUi4dp8zOnae96wDs57a5Lj3RSN5jGywA/lTT2BNcGPdXQK7RAMW zc4Q4bHjVzY/uEEk0pFDMQA= X-Google-Smtp-Source: AOwi7QBfKTgMwxwUkZ2Szsm1K2G9KlbvlIlVSiGj+W/I1VmkvOf8kyTrkqI/YjPo2Uf1fAuOJXUb3A== X-Received: by 10.99.136.73 with SMTP id l70mr2766706pgd.185.1505924976402; Wed, 20 Sep 2017 09:29:36 -0700 (PDT) Received: from localhost.localdomain ([121.137.63.184]) by smtp.gmail.com with ESMTPSA id c185sm8890567pfb.57.2017.09.20.09.29.31 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 20 Sep 2017 09:29:35 -0700 (PDT) From: Sergey Senozhatsky To: Tony Luck , Fenghua Yu , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , James Bottomley , Helge Deller Cc: Petr Mladek , Steven Rostedt , Andrew Morton , Jessica Yu , Alexei Starovoitov , linux-ia64@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Sergey Senozhatsky Subject: [RFC][PATCH v2 2/7] sections: split dereference_function_descriptor() Date: Thu, 21 Sep 2017 01:29:04 +0900 Message-Id: <20170920162910.32053-3-sergey.senozhatsky@gmail.com> X-Mailer: git-send-email 2.14.1 In-Reply-To: <20170920162910.32053-1-sergey.senozhatsky@gmail.com> References: <20170920162910.32053-1-sergey.senozhatsky@gmail.com> Sender: linux-parisc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-parisc@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP There are two format specifiers to print out a pointer in symbolic format: '%pS/%ps' and '%pF/%pf'. On most architectures, the two mean exactly the same thing, but some architectures (ia64, ppc64, parisc64) use an indirect pointer for C function pointers, where the function pointer points to a function descriptor (which in turn contains the actual pointer to the code). The '%pF/%pf, when used appropriately, automatically does the appropriate function descriptor dereference on such architectures. The "when used appropriately" part is tricky. Basically this is a subtle ABI detail, specific to some platforms, that made it to the API level and people can be unaware of it and miss the whole "we need to dereference the function" business out. [1] proves that point (note that it fixes only '%pF' and '%pS', there might be '%pf' and '%ps' cases as well). It appears that we can handle everything within the affected arches and make '%pS/%ps' smart enough to retire '%pF/%pf'. Function descriptors live in .opd elf section and all affected arches (ia64, ppc64, parisc64) handle it properly for kernel and modules. So we, technically, can decide if the dereference is needed by simply looking at the pointer: if it belongs to .opd section then we need to dereference it. The kernel and modules have their own .opd sections, obviously, that's why we need to split dereference_function_descriptor() and use separate kernel and module dereference arch callbacks. This patch does the first step, it a) adds dereference_kernel_function_descriptor() function. b) adds a weak alias to dereference_module_function_descriptor() function. So, for the time being, we will have: 1) dereference_function_descriptor() A generic function, that simply dereferences the pointer. There is bunch of places that call it: kgdbts, init/main.c, extable, etc. 2) dereference_kernel_function_descriptor() A function to call on kernel symbols that does kernel .opd section address range test. 3) dereference_module_function_descriptor() A function to call on modules' symbols that does modules' .opd section address range test. [1] https://marc.info/?l=linux-kernel&m=150472969730573 Signed-off-by: Sergey Senozhatsky --- include/asm-generic/sections.h | 8 ++++++-- include/linux/moduleloader.h | 4 ++++ kernel/module.c | 6 ++++++ 3 files changed, 16 insertions(+), 2 deletions(-) diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h index e5da44eddd2f..387f22c41e0d 100644 --- a/include/asm-generic/sections.h +++ b/include/asm-generic/sections.h @@ -29,6 +29,7 @@ * __ctors_start, __ctors_end * __irqentry_text_start, __irqentry_text_end * __softirqentry_text_start, __softirqentry_text_end + * __start_opd, __end_opd */ extern char _text[], _stext[], _etext[]; extern char _data[], _sdata[], _edata[]; @@ -47,12 +48,15 @@ extern char __softirqentry_text_start[], __softirqentry_text_end[]; /* Start and end of .ctors section - used for constructor calls. */ extern char __ctors_start[], __ctors_end[]; +/* Start and end of .opd section - used for function descriptors. */ +extern char __start_opd[], __end_opd[]; + extern __visible const void __nosave_begin, __nosave_end; -/* function descriptor handling (if any). Override - * in asm/sections.h */ +/* Function descriptor handling (if any). Override in asm/sections.h */ #ifndef dereference_function_descriptor #define dereference_function_descriptor(p) (p) +#define dereference_kernel_function_descriptor(p) (p) #endif /* random extra sections (if any). Override diff --git a/include/linux/moduleloader.h b/include/linux/moduleloader.h index 4d0cb9bba93e..172904e9cded 100644 --- a/include/linux/moduleloader.h +++ b/include/linux/moduleloader.h @@ -85,6 +85,10 @@ void module_arch_cleanup(struct module *mod); /* Any cleanup before freeing mod->module_init */ void module_arch_freeing_init(struct module *mod); +/* Dereference module function descriptor */ +unsigned long dereference_module_function_descriptor(struct module *mod, + unsigned long addr); + #ifdef CONFIG_KASAN #include #define MODULE_ALIGN (PAGE_SIZE << KASAN_SHADOW_SCALE_SHIFT) diff --git a/kernel/module.c b/kernel/module.c index ea77ab13bead..b792e814150a 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -2121,6 +2121,12 @@ void __weak module_arch_freeing_init(struct module *mod) { } +unsigned long __weak dereference_module_function_descriptor(struct module *mod, + unsigned long addr) +{ + return addr; +} + /* Free a module, remove from lists, etc. */ static void free_module(struct module *mod) {