From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 92BDAC3A59E for ; Sat, 24 Aug 2019 13:12:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 629002082F for ; Sat, 24 Aug 2019 13:12:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1566652375; bh=x3hDFUBUcUQdJiD58SM9PS9rubeeOJb0jehA2muo4mI=; h=From:To:Cc:Subject:Date:List-ID:From; b=hxU0KBaRIFjmPuwlBEbQo5EBJY6MrLi90hZ0imSX19f88RqSYjSCMJ+saEeBmh07W B5aIavfAn83o51DmuFF/qOCGaU7x4yN0dke7IilzdkRcx+8cdHk/eV4sIZmmuh8riH PgzEX8CTUCAXGbtLx6XTgi5xJAV6C6OjRhBDHEw0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727756AbfHXNMy (ORCPT ); Sat, 24 Aug 2019 09:12:54 -0400 Received: from foss.arm.com ([217.140.110.172]:44298 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727546AbfHXNMy (ORCPT ); Sat, 24 Aug 2019 09:12:54 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 6994D28; Sat, 24 Aug 2019 06:12:53 -0700 (PDT) Received: from why.lan (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 505413F246; Sat, 24 Aug 2019 06:12:52 -0700 (PDT) From: Marc Zyngier To: linux-kernel@vger.kernel.org Cc: Masami Hiramatsu , Arnaldo Carvalho de Melo , Peter Zijlstra , Will Deacon , Catalin Marinas Subject: [PATCH] kallsyms: Don't let kallsyms_lookup_size_offset() fail on retrieving the first symbol Date: Sat, 24 Aug 2019 14:12:31 +0100 Message-Id: <20190824131231.26399-1-maz@kernel.org> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org An arm64 kernel configured with CONFIG_KPROBES=y CONFIG_KALLSYMS=y # CONFIG_KALLSYMS_ALL is not set CONFIG_KALLSYMS_BASE_RELATIVE=y reports the following kprobe failure: [ 0.032677] kprobes: failed to populate blacklist: -22 [ 0.033376] Please take care of using kprobes. It appears that kprobe fails to retrieve the symbol at address 0xffff000010081000, despite this symbol being in System.map: ffff000010081000 T __exception_text_start This symbol is part of the first group of aliases in the kallsyms_offsets array (symbol names generated using ugly hacks in scripts/kallsyms.c): kallsyms_offsets: .long 0x1000 // do_undefinstr .long 0x1000 // efi_header_end .long 0x1000 // _stext .long 0x1000 // __exception_text_start .long 0x12b0 // do_cp15instr Looking at the implementation of get_symbol_pos(), it returns the lowest index for aliasing symbols. In this case, it return 0. But kallsyms_lookup_size_offset() considers 0 as a failure, which is obviously wrong (there is definitely a valid symbol living there). In turn, the kprobe blacklisting stops abruptly, hence the original error. A CONFIG_KALLSYMS_ALL kernel wouldn't fail as there is always some random symbols at the beginning of this array, which are never looked up via kallsyms_lookup_size_offset. Fix it by considering that get_symbol_pos() is always successful (which is consistent with the other uses of this function). Fixes: ffc5089196446 ("[PATCH] Create kallsyms_lookup_size_offset()") Cc: Masami Hiramatsu Cc: Arnaldo Carvalho de Melo Cc: Peter Zijlstra Cc: Will Deacon Cc: Catalin Marinas Signed-off-by: Marc Zyngier --- kernel/kallsyms.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index 95a260f9214b..136ce049c4ad 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -263,8 +263,10 @@ int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize, { char namebuf[KSYM_NAME_LEN]; - if (is_ksym_addr(addr)) - return !!get_symbol_pos(addr, symbolsize, offset); + if (is_ksym_addr(addr)) { + get_symbol_pos(addr, symbolsize, offset); + return 1; + } return !!module_address_lookup(addr, symbolsize, offset, NULL, namebuf) || !!__bpf_address_lookup(addr, symbolsize, offset, namebuf); } -- 2.20.1