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 621A0C433EF for ; Wed, 19 Jan 2022 23:43:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344598AbiASXnL (ORCPT ); Wed, 19 Jan 2022 18:43:11 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]:25359 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344567AbiASXnK (ORCPT ); Wed, 19 Jan 2022 18:43:10 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1642635789; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=qcTt5kGemYKdl5NHHgbm78aYoqfuFslMpyzSj05wWe4=; b=FxTJKuvkRqMMCq4tBtr4nB7cv33KE69JiNC/3mQG+r8Sve3ZWmWmC7JsnRa4Fu6BRkMRKw 2O3dZmNN/G4NJG9CqP8XuLdvaIADmozABMh82XxrZ7Hg2Pr17D1aqSTEQpT47j7Gp7Ws28 pzQ54CgmCni1RZQfxXrV4lk/e9N2Bmk= Received: from mail-ot1-f69.google.com (mail-ot1-f69.google.com [209.85.210.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-577-jqDkL5xdMFWmWPBkuVOpSg-1; Wed, 19 Jan 2022 18:43:08 -0500 X-MC-Unique: jqDkL5xdMFWmWPBkuVOpSg-1 Received: by mail-ot1-f69.google.com with SMTP id f12-20020a9d5e8c000000b005907d2f83d0so2498736otl.10 for ; Wed, 19 Jan 2022 15:43:07 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=qcTt5kGemYKdl5NHHgbm78aYoqfuFslMpyzSj05wWe4=; b=byOhpKWmZbYn9b8tjwUB2RE2SGDWBhxo9HBbLt906+bhcvGwEvs2+j8m+Eyw6qEvOn qdo0Y9o5R56jkF5PQwUNHTZZatbSN9+ZmfX22DHQnDNaJvJaN2Y2JeYM0oNXliXoPKd6 LCRMZ5f+x00+0AJPhTfRciZCw1SKdun2nqbqIS9XNYWbN/YLZN3j7Nq4UmaZcDRqLpKl Hx18qMCpm7ee+kNi2QwpbAR6YcMOmO3Oe5T/N0fNFdhKaCAHPBoQbODi8F5jF8BdHkSg jgy1v2Al/LN1/MwLD4BcpI1h/bD6goyMq/Mb+WifX6iZ9dGVOMjlNdQcEyWe14d9yANz d3Kg== X-Gm-Message-State: AOAM530du7EtsWv2yr1g2XQU5Ae92MKDiwyHA4gmhaCDUWhSKFGIpR3w NAD0cAxP1i5BMF+rQ17lPB+dS7SzVIbb5fZUlpBKbrpPHLnC34BlJL3hkQ5ajdBWY+Fq52Y/oFu jXUtRb0kt6gJezs6S7+B4FnB6 X-Received: by 2002:aca:1311:: with SMTP id e17mr5376386oii.30.1642635786081; Wed, 19 Jan 2022 15:43:06 -0800 (PST) X-Google-Smtp-Source: ABdhPJxLmMK+K8rmtAuPb4cNun1UAw0cAC14LlR7gXQBNWbYuApI3UJPyN+FbQwm2fa2ymShPD6kkw== X-Received: by 2002:aca:1311:: with SMTP id e17mr5376374oii.30.1642635785796; Wed, 19 Jan 2022 15:43:05 -0800 (PST) Received: from treble ([2600:1700:6e32:6c00::c]) by smtp.gmail.com with ESMTPSA id n22sm530091ooq.27.2022.01.19.15.43.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 19 Jan 2022 15:43:05 -0800 (PST) Date: Wed, 19 Jan 2022 15:43:03 -0800 From: Josh Poimboeuf To: Kaiwan N Billimoria Cc: Linux Kernel Mailing List , Chi-Thanh Hoang Subject: Re: Issue using faddr2line on kernel modules Message-ID: <20220119234303.tmebbcrg2vpnri4s@treble> References: <20220117194836.vj2rxr3wocrtdx7k@treble> <20220117202751.bmwvfsnqxokob6d2@treble> <20220118175239.lqxi2ycgeusk5pxl@treble> <20220119212126.aydgx62abbngumwy@treble> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20220119212126.aydgx62abbngumwy@treble> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 19, 2022 at 01:21:29PM -0800, Josh Poimboeuf wrote: > > $ nm -n ./oops_tryv2.ko |grep -C5 do_the_work > > 0000000000000000 r __func__.24215 > > 0000000000000000 r __param_bug_in_workq > > 0000000000000000 D __this_module > > 0000000000000000 r _note_7 > > 0000000000000000 T cleanup_module > > 0000000000000000 t do_the_work > > 0000000000000000 t do_the_work.cold > > 0000000000000000 b gctx > > 0000000000000000 T init_module > > 0000000000000000 t try_oops_exit > > 0000000000000000 t try_oops_init > > 0000000000000008 b t1 > > $ > > > > BTW, here's the code: > > https://github.com/PacktPublishing/Linux-Kernel-Debugging/tree/main/ch7/oops_tryv2 > > Ok, it looks like the symbols aren't sorted like the code expects. I > need to do a more robust fix. Ok, please try this instead. This takes a much more robust approach to the function size calculation, using readelf to confine the symbol search to the section matching the original symbol. This actually has multiple fixes and cleanups, so it'll eventually be split up into a patch set. ---- diff --git a/scripts/faddr2line b/scripts/faddr2line index 6c6439f69a72..1acb68927977 100755 --- a/scripts/faddr2line +++ b/scripts/faddr2line @@ -97,10 +97,11 @@ __faddr2line() { local dir_prefix=$3 local print_warnings=$4 + local first=1 local func=${func_addr%+*} local offset=${func_addr#*+} offset=${offset%/*} - local size= + local user_size= [[ $func_addr =~ "/" ]] && size=${func_addr#*/} if [[ -z $func ]] || [[ -z $offset ]] || [[ $func = $func_addr ]]; then @@ -110,73 +111,87 @@ __faddr2line() { fi # Go through each of the object's symbols which match the func name. - # In rare cases there might be duplicates. - file_end=$(${SIZE} -Ax $objfile | awk '$1 == ".text" {print $2}') + # In rare cases there might be duplicates, in which case we print both. while read symbol; do local fields=($symbol) - local sym_base=0x${fields[0]} - local sym_type=${fields[1]} - local sym_end=${fields[3]} - - # calculate the size - local sym_size=$(($sym_end - $sym_base)) - if [[ -z $sym_size ]] || [[ $sym_size -le 0 ]]; then - warn "bad symbol size: base: $sym_base end: $sym_end" + local sym_addr=0x${fields[1]} + local sym_size=${fields[2]} + local sym_sec=${fields[6]} + + # Get the section size: + local sec_size=$(${READELF} --section-headers --wide $objfile | + sed 's/\[ /\[/' | + awk -v sec=$sym_sec '$1 == "[" sec "]" { print "0x" $6; exit }') + + if [[ -z $sec_size ]]; then + warn "bad section size: section: $sym_sec" DONE=1 return fi - sym_size=0x$(printf %x $sym_size) - # calculate the address - local addr=$(($sym_base + $offset)) - if [[ -z $addr ]] || [[ $addr = 0 ]]; then - warn "bad address: $sym_base + $offset" + # Calculate the symbol size: + # + # We can't use the ELF size, because kallsyms also includes the + # padding bytes in its size calculation. For kallsyms, the + # size calculation is the distance between the symbol and the + # next symbol in a sorted list. + local size=$(${READELF} --symbols --wide $objfile | + awk -v sec=$sym_sec '$7 == sec' | + sort --key=2 | + awk --bignum -v sym_addr=${sym_addr#0x} -v sym_size=${sym_size} -v sym_name=${func} -v sec_size=${sec_size} \ + '$2 == sym_addr && $3 == sym_size && $8 == sym_name { found = 1; next } \ + found == 1 { size = strtonum("0x" $2) - strtonum("0x" sym_addr); if (size < sym_size) next; found = 2; print size; exit } \ + END { if (found == 1) print strtonum(sec_size) }') + + if [[ -z $size ]]; then + warn "bad symbol size: addr: $sym_addr" DONE=1 return fi - addr=0x$(printf %x $addr) - # weed out non-function symbols - if [[ $sym_type != t ]] && [[ $sym_type != T ]]; then - [[ $print_warnings = 1 ]] && - echo "skipping $func address at $addr due to non-function symbol of type '$sym_type'" - continue + # Calculate the specified address: + local addr=$(($sym_addr + $offset)) + if [[ -z $addr ]] || [[ $addr = 0 ]]; then + warn "bad address: $sym_addr + $offset" + DONE=1 + return fi + addr=0x$(printf %x $addr) - # if the user provided a size, make sure it matches the symbol's size - if [[ -n $size ]] && [[ $size -ne $sym_size ]]; then + # If the user provided a size, make sure it matches the symbol's size: + if [[ -n $user_size ]] && [[ $user_size -ne $size ]]; then [[ $print_warnings = 1 ]] && - echo "skipping $func address at $addr due to size mismatch ($size != $sym_size)" + echo "skipping $func address at $addr due to size mismatch ($user_size != $size)" continue; fi - # make sure the provided offset is within the symbol's range - if [[ $offset -gt $sym_size ]]; then + # Make sure the provided offset is within the symbol's range: + if [[ $offset -gt $size ]]; then [[ $print_warnings = 1 ]] && - echo "skipping $func address at $addr due to size mismatch ($offset > $sym_size)" + echo "skipping $func address at $addr due to size mismatch ($offset > $size)" continue fi - # separate multiple entries with a blank line - [[ $FIRST = 0 ]] && echo - FIRST=0 + # In case of duplicates, separate multiple entries with a blank line: + [[ $first = 0 ]] && echo + first=0 - # pass real address to addr2line - echo "$func+$offset/$sym_size:" - local file_lines=$(${ADDR2LINE} -fpie $objfile $addr | sed "s; $dir_prefix\(\./\)*; ;") - [[ -z $file_lines ]] && return + # Pass full address to addr2line: + echo "$func+$offset/$size:" + local output=$(${ADDR2LINE} -fpie $objfile $addr | sed "s; $dir_prefix\(\./\)*; ;") + [[ -z $output ]] && continue if [[ $LIST = 0 ]]; then - echo "$file_lines" | while read -r line + echo "$output" | while read -r line do echo $line done DONE=1; - return + continue fi - # show each line with context - echo "$file_lines" | while read -r line + # If --list was specified, show each line with context: + echo "$output" | while read -r line do echo echo $line @@ -189,7 +204,7 @@ __faddr2line() { DONE=1 - done < <(${NM} -n $objfile | awk -v fn=$func -v end=$file_end '$3 == fn { found=1; line=$0; start=$1; next } found == 1 { found=0; print line, "0x"$1 } END {if (found == 1) print line, end; }') + done < <(${READELF} --symbols --wide $objfile | awk -v fn=$func '$4 == "FUNC" && $8 == fn') } [[ $# -lt 2 ]] && usage