Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CB519C433F5 for ; Mon, 6 Dec 2021 14:05:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245189AbhLFOI6 (ORCPT ); Mon, 6 Dec 2021 09:08:58 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39024 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244907AbhLFOIx (ORCPT ); Mon, 6 Dec 2021 09:08:53 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A89C9C061746; Mon, 6 Dec 2021 06:05:24 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 40612612D0; Mon, 6 Dec 2021 14:05:24 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 40A06C341C1; Mon, 6 Dec 2021 14:05:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1638799523; bh=ZEns0mDd6iujCYYyTApsz8EIv4VNFohCpWe5NnsZlmE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=OVBkZy5O09WWWQCQ4OhHA4blEsJ+2BTTMK2uB5Rh339tAqEf7frcn/I+0dx1JAX2U cK55DUFCuGNPrQa0m7+BuUqXxP4sKz8jTFMpd6O+qiQqicphQ6HEX2bkEDvr/mlumY I3V4JdRaweekes0cFfJ1IGhHPSKnQUL1z699BcUhuKjo60Kdm6EVgxAjpJRi6Y7NIh SUkjBIDD1G9T2lBQcQOO2pYQm7N7ZCEeQpxHosBEu1A8d2VGnnqYkM/0t/4TpZIyLk reFXDLvz+7qFRdfVRqWuWyRqQrMSNoCdKpVlUhoYvH5SOQDLIUzIc0G1pfwe4GtaTa orRskyV86+BRg== From: Miguel Ojeda 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 , Wedson Almeida Filho , Gary Guo , Boqun Feng Subject: [PATCH 01/19] kallsyms: support "big" kernel symbols Date: Mon, 6 Dec 2021 15:02:55 +0100 Message-Id: <20211206140313.5653-2-ojeda@kernel.org> In-Reply-To: <20211206140313.5653-1-ojeda@kernel.org> References: <20211206140313.5653-1-ojeda@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 longer lengths to the symbol table. In order to avoid increasing all lengths to 2 bytes (since most of them are small, including many Rust ones), we use ULEB128 to keep smaller symbols in 1 byte, with the rest in 2 bytes. Co-developed-by: Alex Gaynor Signed-off-by: Alex Gaynor Co-developed-by: Wedson Almeida Filho Signed-off-by: Wedson Almeida Filho Co-developed-by: Gary Guo Signed-off-by: Gary Guo Co-developed-by: Boqun Feng Signed-off-by: Boqun Feng Signed-off-by: Miguel Ojeda --- kernel/kallsyms.c | 26 ++++++++++++++++++++++---- scripts/kallsyms.c | 29 ++++++++++++++++++++++++++--- 2 files changed, 48 insertions(+), 7 deletions(-) diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index 3011bc33a5ba..80702273494a 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -69,12 +69,20 @@ static unsigned int kallsyms_expand_symbol(unsigned int off, data = &kallsyms_names[off]; len = *data; data++; + off++; + + /* If MSB is 1, it is a "big" symbol, so needs an additional byte. */ + if ((len & 0x80) != 0) { + len = (len & 0x7F) | (*data << 7); + data++; + off++; + } /* * Update the offset to return the offset for the next symbol on * the compressed stream. */ - off += len + 1; + off += len; /* * For every byte on the compressed symbol data, copy the table @@ -127,7 +135,7 @@ static char kallsyms_get_symbol_type(unsigned int off) static unsigned int get_symbol_offset(unsigned long pos) { const u8 *name; - int i; + int i, len; /* * Use the closest marker we have. We have markers every 256 positions, @@ -141,8 +149,18 @@ static unsigned int get_symbol_offset(unsigned long pos) * so we just need to add the len to the current pointer for every * symbol we wish to skip. */ - for (i = 0; i < (pos & 0xFF); i++) - name = name + (*name) + 1; + for (i = 0; i < (pos & 0xFF); i++) { + len = *name; + + /* + * If MSB is 1, it is a "big" symbol, so we need to look into + * the next byte (and skip it, too). + */ + if ((len & 0x80) != 0) + len = ((len & 0x7F) | (name[1] << 7)) + 1; + + name = name + len + 1; + } return name - kallsyms_names; } diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c index 54ad86d13784..79b11bb7f07d 100644 --- a/scripts/kallsyms.c +++ b/scripts/kallsyms.c @@ -470,12 +470,35 @@ 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. */ + 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-byte ULEB128 are supported. */ + if (table[i]->len > 0x3FFF) { + fprintf(stderr, "kallsyms failure: " + "unexpected huge symbol length\n"); + exit(EXIT_FAILURE); + } + + /* Encode length with ULEB128. */ + if (table[i]->len <= 0x7F) { + /* 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 two bytes. */ + printf("\t.byte 0x%02x, 0x%02x", + (table[i]->len & 0x7F) | 0x80, + (table[i]->len >> 7) & 0x7F); + off += table[i]->len + 2; + } for (k = 0; k < table[i]->len; k++) printf(", 0x%02x", table[i]->sym[k]); printf("\n"); - - off += table[i]->len + 1; } printf("\n"); -- 2.34.0