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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id AD5F1C433F5 for ; Mon, 23 May 2022 02:03:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1349128AbiEWCDD (ORCPT ); Sun, 22 May 2022 22:03:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40134 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344697AbiEWCDB (ORCPT ); Sun, 22 May 2022 22:03:01 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C278235AB2; Sun, 22 May 2022 19:03:00 -0700 (PDT) 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 ams.source.kernel.org (Postfix) with ESMTPS id 63BCCB80E91; Mon, 23 May 2022 02:02:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8C726C385AA; Mon, 23 May 2022 02:02:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1653271378; bh=sYOx1bIFVnt09xMcRd5kuHst5ENxAGoCbpg7Au5i8+w=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=FcrGw4oNIy9f7mA2VyI83xmcNwMayEr97PbrLDmj+25/8+UfA+dMpKxRN0MB8gaxz hJcrZ7dnv6ZV9FnplVhhQ+FOlKkrafhSL0smE4g/OT/CbKZiW1pzJUt89SG6MMj3Zg qPRdAkm7iNkrCBX3x/ng+a4L7PxDtprdofeV1MWsjk6kgrlkEMOQcMcIdHsTbGiIA5 53dMSFjLzjpmS8r63DimSDp/PxN3DqQKDWC4WtoX7IMy3LpDHjXL2i+WvpLIyu3wSr aTd4S/TFpLveJxBB9bXcNM1bXp2+lttiWxMOt+cjJkg4ci/0Fm5Eu1QaVCWRVXo18F KI8jovmV5kwjg== From: Miguel Ojeda To: Linus Torvalds , Greg Kroah-Hartman Cc: rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, Jarkko Sakkinen , Miguel Ojeda , Kees Cook , Alex Gaynor , Wedson Almeida Filho , Gary Guo , Boqun Feng , Matthew Wilcox Subject: [PATCH v7 02/25] kallsyms: support "big" kernel symbols Date: Mon, 23 May 2022 04:01:15 +0200 Message-Id: <20220523020209.11810-3-ojeda@kernel.org> In-Reply-To: <20220523020209.11810-1-ojeda@kernel.org> References: <20220523020209.11810-1-ojeda@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: rust-for-linux@vger.kernel.org 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. Reviewed-by: Kees Cook 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 Co-developed-by: Matthew Wilcox Signed-off-by: Matthew Wilcox Signed-off-by: Miguel Ojeda --- This is a prerequisite patch, independently submitted at: https://lore.kernel.org/lkml/20220506203443.24721-3-ojeda@kernel.org/ 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 79f2eb617a62..e8d2262ef2d2 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 82d6508bdf29..7e99799aa7b9 100644 --- a/scripts/kallsyms.c +++ b/scripts/kallsyms.c @@ -480,12 +480,35 @@ 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"); -- 2.36.1