From patchwork Sat Sep 16 03:53:43 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sergey Senozhatsky X-Patchwork-Id: 814459 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [103.22.144.68]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3xvJWF0BYsz9t16 for ; Sat, 16 Sep 2017 14:02:17 +1000 (AEST) Authentication-Results: ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.b="GWUxHrCD"; dkim-atps=neutral Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 3xvJWD68TnzDqYQ for ; Sat, 16 Sep 2017 14:02:16 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.b="GWUxHrCD"; dkim-atps=neutral X-Original-To: linuxppc-dev@lists.ozlabs.org Delivered-To: linuxppc-dev@lists.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=gmail.com (client-ip=2607:f8b0:400e:c00::244; helo=mail-pf0-x244.google.com; envelope-from=sergey.senozhatsky@gmail.com; receiver=) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.b="GWUxHrCD"; dkim-atps=neutral Received: from mail-pf0-x244.google.com (mail-pf0-x244.google.com [IPv6:2607:f8b0:400e:c00::244]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3xvJRD2p7bzDrnj for ; Sat, 16 Sep 2017 13:58:48 +1000 (AEST) Received: by mail-pf0-x244.google.com with SMTP id g65so2071095pfe.1 for ; Fri, 15 Sep 2017 20:58:48 -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=m4NVOdEEbgW+yLsF7VlHqvGOWnvuNQRtnSx21e1b6Bk=; b=GWUxHrCDC9NQnugVSPE13EEAzjg3FO7MWI5lHZ8uYb4UJA08gWv91oqYlETEOoxcDb IxTIwIJygr5NNjw29iyt1sAPwjAgvR4HBDOWpn3M7x1AlILrt49Q5jhauEq8gSfNXSIy VXeDW5mt+/ITH21oFYBA2j8lqil9Byv+c7pyhO9FjeLlu82+Kx8IYcqjT4X8yf2IMVr7 BECWFVC0lSzfaQKkHyNGtaw3CAZXpMst4uRe4ObrtWBIGg9w2ueCoK5AbxLiRYMxhvXV ow/RSmQFDJlGlnJhSDjZgZbhfgWrC4mBiy2RW2Sh0crw91zOJlwKbNG7+ox0PSlO0iV+ La+g== 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=m4NVOdEEbgW+yLsF7VlHqvGOWnvuNQRtnSx21e1b6Bk=; b=tfDbRkkhu6eLYWvY+kXBrB+X/t76Cnz/efaKbksu6U1AvjGCwvW524V9y+JBDPaZST x8T76hw9+fDLCGk+zQEo/3mXAO9AOChKyOJ2aZ6DfiADm3QY5slXIgJz3Kx7h3oUSw2A xtZwmKzoWEF0crve57IefSIDmSFPuGq7iaTuDondKbw39lyAdZX0DidTJCchbZWPzEQ9 yf5OcAkb3/7iN0ObjohzBst2FT9KOxlfzajIdNSx/dDXF+vyVTki9mmnkjlLMJoSlA30 NgHsNxcrGNGSZlTxcmBInZoJRr7AO8YfxbdAHXujnQ2NDItpN7xpvnibrJPrPPbp9iWf EcGg== X-Gm-Message-State: AHPjjUioW509ntDmH56kLV68fAqHuvbIuGbDffRm3JjBPfjAsFZQQzjn UiBq9CothUBDaA== X-Google-Smtp-Source: ADKCNb6mwPuyg3VsLqB8A+HCfUVPghXXhZz4raiSj1edh5EUJMxQaWQmff7m8wqvMfgSiRh91pjbmQ== X-Received: by 10.84.238.141 with SMTP id v13mr30891509plk.349.1505534326300; Fri, 15 Sep 2017 20:58:46 -0700 (PDT) Received: from localhost.localdomain ([121.137.63.184]) by smtp.gmail.com with ESMTPSA id 76sm4448230pfp.158.2017.09.15.20.58.41 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 15 Sep 2017 20:58:45 -0700 (PDT) From: Sergey Senozhatsky To: Tony Luck , Fenghua Yu , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , "James E . J . Bottomley" , Helge Deller Subject: [PATCH 1/5] sections: split dereference_function_descriptor() Date: Sat, 16 Sep 2017 12:53:43 +0900 Message-Id: <20170916035347.19705-2-sergey.senozhatsky@gmail.com> X-Mailer: git-send-email 2.14.1 In-Reply-To: <20170916035347.19705-1-sergey.senozhatsky@gmail.com> References: <20170916035347.19705-1-sergey.senozhatsky@gmail.com> X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.24 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Petr Mladek , linux-ia64@vger.kernel.org, linux-parisc@vger.kernel.org, Alexei Starovoitov , Steven Rostedt , linux-kernel@vger.kernel.org, Sergey Senozhatsky , Jessica Yu , Andrew Morton , linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" 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 | 4 ++-- include/linux/moduleloader.h | 4 ++++ kernel/module.c | 6 ++++++ 3 files changed, 12 insertions(+), 2 deletions(-) diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h index e5da44eddd2f..21d2165e531a 100644 --- a/include/asm-generic/sections.h +++ b/include/asm-generic/sections.h @@ -49,10 +49,10 @@ extern char __ctors_start[], __ctors_end[]; 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 de66ec825992..87cdb46863cd 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) {