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=-16.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 BF52FC433B4 for ; Wed, 14 Apr 2021 18:46:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 97A0661164 for ; Wed, 14 Apr 2021 18:46:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353026AbhDNSqx (ORCPT ); Wed, 14 Apr 2021 14:46:53 -0400 Received: from mail.kernel.org ([198.145.29.99]:49072 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1353021AbhDNSqt (ORCPT ); Wed, 14 Apr 2021 14:46:49 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 0846F61153; Wed, 14 Apr 2021 18:46:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1618425987; bh=tIW9/GtTYEr3rMqQ5PvPIFl8/iExEIaumsIoas5zmX4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PoNrqlzwz9Ra54wscIVxKxX0ProvI6EOrNWeIHFtqBB7kSGF6XofnEdnVMH3NalVp qsfxzvXGCJxTrSGUv09oa3LSgMYdyLPirYHv0QvNUTUVEyqHOFR08hJFysyJsfzHLe 26wKZXYKxSCYpgb8XWpEXvkLsDN0yjzXDDtWAKawMFWJXgPfP98s6q8AzzgzKBIsJ1 yTaGR05/kNtLBlYhGPCjqNmEZLlQS/CtXZtC637dBSQBrDiS8WkGA3kb1EDNwLHXCL StXFViddTaTOuO+a7Uw4zJkcycMiGSj3LuEpA/fj8TPj0YgVqBtUrjuM2siBrG36pP xpiZTp8U9LH5w== From: ojeda@kernel.org To: Linus Torvalds , Greg Kroah-Hartman Cc: rust-for-linux@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Miguel Ojeda , Alex Gaynor , Geoffrey Thomas , Finn Behrens , Adam Bratschi-Kaye , Wedson Almeida Filho Subject: [PATCH 01/13] kallsyms: Support "big" kernel symbols (2-byte lengths) Date: Wed, 14 Apr 2021 20:45:52 +0200 Message-Id: <20210414184604.23473-2-ojeda@kernel.org> In-Reply-To: <20210414184604.23473-1-ojeda@kernel.org> References: <20210414184604.23473-1-ojeda@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: rust-for-linux@vger.kernel.org From: Miguel Ojeda Rust symbols can become quite long due to namespacing introduced by modules, types, traits, generics, etc. Increasing to 255 is not enough in some cases, and therefore we need to introduce 2-byte lengths to the symbol table. We call these "big" symbols. In order to avoid increasing all lengths to 2 bytes (since most of them only require 1 byte, including many Rust ones), we use length zero to mark "big" symbols in the table. Co-developed-by: Alex Gaynor Signed-off-by: Alex Gaynor Co-developed-by: Geoffrey Thomas Signed-off-by: Geoffrey Thomas Co-developed-by: Finn Behrens Signed-off-by: Finn Behrens Co-developed-by: Adam Bratschi-Kaye Signed-off-by: Adam Bratschi-Kaye Co-developed-by: Wedson Almeida Filho Signed-off-by: Wedson Almeida Filho Signed-off-by: Miguel Ojeda --- kernel/kallsyms.c | 7 +++++++ scripts/kallsyms.c | 31 ++++++++++++++++++++++++++++--- 2 files changed, 35 insertions(+), 3 deletions(-) diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index 8043a90aa50e..faba546e9a58 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -73,6 +73,13 @@ static unsigned int kallsyms_expand_symbol(unsigned int off, */ off += len + 1; + /* If zero, it is a "big" symbol, so a two byte length follows. */ + if (len == 0) { + len = (data[0] << 8) | data[1]; + data += 2; + off += len + 2; + } + /* * For every byte on the compressed symbol data, copy the table * entry for that byte. diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c index 54ad86d13784..bcdabee13aab 100644 --- a/scripts/kallsyms.c +++ b/scripts/kallsyms.c @@ -470,12 +470,37 @@ static void write_src(void) if ((i & 0xFF) == 0) markers[i >> 8] = off; - printf("\t.byte 0x%02x", table[i]->len); + /* + * There cannot be any symbol of length zero -- we use that + * to mark a "big" symbol (and it doesn't make sense anyway). + */ + if (table[i]->len == 0) { + fprintf(stderr, "kallsyms failure: " + "unexpected zero symbol length\n"); + exit(EXIT_FAILURE); + } + + /* Only lengths that fit in up to two bytes are supported. */ + if (table[i]->len > 0xFFFF) { + fprintf(stderr, "kallsyms failure: " + "unexpected huge symbol length\n"); + exit(EXIT_FAILURE); + } + + if (table[i]->len <= 0xFF) { + /* Most symbols use a single byte for the length. */ + printf("\t.byte 0x%02x", table[i]->len); + off += table[i]->len + 1; + } else { + /* "Big" symbols use a zero and then two bytes. */ + printf("\t.byte 0x00, 0x%02x, 0x%02x", + (table[i]->len >> 8) & 0xFF, + table[i]->len & 0xFF); + off += table[i]->len + 3; + } for (k = 0; k < table[i]->len; k++) printf(", 0x%02x", table[i]->sym[k]); printf("\n"); - - off += table[i]->len + 1; } printf("\n"); -- 2.17.1