From patchwork Sat Sep 30 02:53:14 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sergey Senozhatsky X-Patchwork-Id: 9979071 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 62F0D6037F for ; Sat, 30 Sep 2017 02:55:30 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 582EE297C2 for ; Sat, 30 Sep 2017 02:55:30 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 4CEAC297CD; Sat, 30 Sep 2017 02:55:30 +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 A761C297C2 for ; Sat, 30 Sep 2017 02:55:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752676AbdI3CyH (ORCPT ); Fri, 29 Sep 2017 22:54:07 -0400 Received: from mail-pg0-f68.google.com ([74.125.83.68]:37332 "EHLO mail-pg0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752649AbdI3CyE (ORCPT ); Fri, 29 Sep 2017 22:54:04 -0400 Received: by mail-pg0-f68.google.com with SMTP id 125so879617pgj.4; Fri, 29 Sep 2017 19:54:04 -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=JHyTVZD676N/hZj4/970r0yL5skqRwoSnGbluCR0ZjQ=; b=Kf4LTCft1UDFnfBQESmSHPRq0HWrhJanDnAlpVuvhlHPpANg/0BWDBCOB65/lJEVWP QscmlWiNZ5QEQdf+SG7NsnHnAf+YtbnDpTWGYZulqdVxvAev/flcTB7j43BVEidgXUXp K49MHFqoZ4NLGlL7wMg31XzEfOLm8HS/kHopMtEVy82UBT5detE/41qzyVG678grgoha loQRdZ3mK5Ur6tpZ5hiWZXM1+zh4dLO57ixqegvrtHz0FSJHpwCGuplTJmJQF30YvW/j 3+HwpNEP/JHwUvbrC0Q/zQ8xDLnZ3g0j2vYHFpAwady/jpwYktZWLmMftNBhGygixGEU h+wg== 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=JHyTVZD676N/hZj4/970r0yL5skqRwoSnGbluCR0ZjQ=; b=n6dnwLF6Oq5TMzQREfzBPV0HIA472hqzlwjDaltNKVE/mp5d2bqeK97L50WX0LKi2p H3ZPcDVM6Uq3PVgtalBSQGy3qZA0pO9zHQgc78w8+jp8G5kUNpyDsB0v6RVaetW24bfO 4B+JswpdcUfji3pUan4YljYQMr3cCLHzuYauSLDT+h+2EYBnqiHKsJM51wlJWwnWRqRD DJJSyWKzF+xvhpAk9Hwb2Yy9M1pJo0nxsgnyLnWlpikXPE65aLMTZ1ErrCE01UH6hPLu 9kSLH/PBrnbSs5yGZoTE3l28vgopTQxFJcwp2Nj1uCwK4+j9mP/FvTA0C+pUtGdg+NP9 A7Pg== X-Gm-Message-State: AHPjjUhAyM8JKUHpZaWpfRcKeeQEauDmQR4akOCljmVncZwmC9S9jiMK WJ3vUb2u1JRc2e35wg+WpBs= X-Google-Smtp-Source: AOwi7QA3iNOEWVvUk+7DzaNVsQoSw5V2y7a0GlglhFHy8XP+YPHD2+qIqBnhk7MOwcypFWqLtY12gw== X-Received: by 10.84.178.164 with SMTP id z33mr8781175plb.53.1506740044299; Fri, 29 Sep 2017 19:54:04 -0700 (PDT) Received: from localhost.localdomain ([175.223.27.84]) by smtp.gmail.com with ESMTPSA id b1sm8680714pgn.94.2017.09.29.19.53.57 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 29 Sep 2017 19:54:03 -0700 (PDT) From: Sergey Senozhatsky To: Petr Mladek , Steven Rostedt Cc: Tony Luck , Fenghua Yu , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , James Bottomley , Helge Deller , 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: [PATCHv3 2/7] sections: split dereference_function_descriptor() Date: Sat, 30 Sep 2017 11:53:14 +0900 Message-Id: <20170930025319.987-3-sergey.senozhatsky@gmail.com> X-Mailer: git-send-email 2.14.2 In-Reply-To: <20170930025319.987-1-sergey.senozhatsky@gmail.com> References: <20170930025319.987-1-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 Tested-by: Helge Deller # parisc64 Tested-by: Santosh Sivaraj # powerpc64 Acked-by: Michael Ellerman # powerpc64 Tested-by: Tony Luck # ia64 --- 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) {