From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9930047011F; Fri, 7 Aug 2026 10:30:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786098620; cv=none; b=f0bANfoSSj5T2H5e8hzneebk9t84gWqv4QI3YJSm+fqVHLDXP7YjkO3JfFcOYBy+JhErr2aueuym3kdf7BOGyKojoMTfeBpftdA8UyI1nQgS+MYYMq5EXqilS6+n1K8cDg2OYJkRv8qqClnu6ND/JbTKfNqX1cDHeqX9AlO8tCs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786098620; c=relaxed/simple; bh=65SnBkKgpNg1bsafp7VGHMOEGAmrM4yY6cpRnA+3vFY=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=o+EIlXAPR7250ThZaecDC7PdGCkUeECXSu367sUPRn7aeQXharvvFi+0MuVyeDAWJg+1sgit49wow6NFSF7QqUZhvCiuXd8UMUQXxf4Krb8B5HiKOu6NjFXNz5PjBi/0FsqGWUefU5japzhIxwoo3Igf8WiAmuX25iBTpjiYElI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=aQzWs8wq; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="aQzWs8wq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 13B101F000E9; Fri, 7 Aug 2026 10:30:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786098617; bh=D57BfGvE5e2Os2mPHIcMDuZXtKECmeWmZYmGAmiUz34=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=aQzWs8wq+XMWmhGbeVqv6S5c9jg2C3sGoqij4SztGeBGWz9Q4im84gyQM7Lkmb5GD 3UyKlt7FvvMChAPHXSl3/JtjH5+DJkjWLiZ++v/spwYCbDEes+xKx9gGKEyq2wRhBP EI5BVsDnKquuviYY7w2a/E43QYvshGvcf8sN+5z3O/GhFYiff4bTA6bURAKc0+r/qX kq4iLLu65YO2IY/qWYb16kiw05rOWpgSAG6qoiHDCkm7g3LjtdMgKxQE5z4ONbloXb qohYlk6+A70B2iXjagZYZWitFwBr7VBIKXSDjLShxfyhuyI7BriFxaiONrNGQdZghU NU45pJZqyySfA== Date: Fri, 7 Aug 2026 19:30:13 +0900 From: Masami Hiramatsu (Google) To: "Rui Qi" Cc: "Steven Rostedt" , "Mathieu Desnoyers" , "Shuah Khan" , "Heiko Carstens" , , , Subject: Re: [PATCH v2 2/2] selftests/ftrace: Convert ELF entry point to file offset in uprobe test Message-Id: <20260807193013.7fe47144c1f41facb60b310f@kernel.org> In-Reply-To: <20260807081512.2974757-3-qirui.001@bytedance.com> References: <20260806083101.2651025-1-qirui.001@bytedance.com> <20260807081512.2974757-1-qirui.001@bytedance.com> <20260807081512.2974757-3-qirui.001@bytedance.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 7 Aug 2026 16:15:12 +0800 "Rui Qi" wrote: > The add_remove_uprobe test uses readelf -h to obtain the ELF entry > point (e_entry) and passes it directly as the offset to uprobe_events. > However, uprobe_events expects a file offset, not a virtual address. > > For PIE binaries, the virtual address happens to equal the file offset > because the first LOAD segment has p_vaddr == p_offset, so the test > works by coincidence. But for non-PIE executables, e_entry is an > absolute virtual address that can far exceed the file size. When the > probe is enabled, uprobe_register() checks offset > i_size_read(inode) > and rejects it with -EINVAL. Good catch! > > Fix this by converting the virtual address to a file offset using the > ELF program headers: scan readelf -lW output for the LOAD segment > containing the entry point, then compute file_offset = e_entry - > p_vaddr + p_offset. For PIE binaries the result is unchanged; for > non-PIE binaries the offset is correctly translated. > > The conversion uses only POSIX shell primitives, with no dependency on > gawk or perl. > > Fixes: dc4b165855f2 ("selftests/ftrace: Use readelf to find entry point in uprobe test") > Signed-off-by: Rui Qi OK, let me take it. Thank you! > --- > .../test.d/dynevent/add_remove_uprobe.tc | 27 +++++++++++++++++-- > 1 file changed, 25 insertions(+), 2 deletions(-) > > diff --git a/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_uprobe.tc b/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_uprobe.tc > index f2048c244526..19430bd5864c 100644 > --- a/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_uprobe.tc > +++ b/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_uprobe.tc > @@ -12,9 +12,32 @@ echo 0 > events/enable > echo > dynamic_events > > REALBIN=`readlink -f /bin/sh` > -ENTRYPOINT=`readelf -h ${REALBIN} | grep Entry | sed -e 's/[^0]*//'` > > -echo "p:myevent ${REALBIN}:${ENTRYPOINT}" >> uprobe_events > +# Get the entry point virtual address from ELF header > +ENTRY=`readelf -hW ${REALBIN} | grep "Entry point" | awk '{print $NF}'` > + > +# Convert virtual address to file offset: find the LOAD segment containing > +# the entry point, then compute file_offset = e_entry - p_vaddr + p_offset. > +# For PIE binaries this is a no-op (vaddr == file offset), but for non-PIE > +# executables the virtual address is much larger than the file size and > +# must be converted, otherwise uprobe_register() rejects it with -EINVAL. > +ENTRY_DEC=$(printf '%d' "$ENTRY") > +OFFSET=$ENTRY > +while IFS= read -r line; do > + set -- $line > + [ "$1" = "LOAD" ] || continue > + VA_DEC=$(printf '%d' "$3") > + OFF_DEC=$(printf '%d' "$2") > + FSZ_DEC=$(printf '%d' "$5") > + if [ "$ENTRY_DEC" -ge "$VA_DEC" ] && [ "$ENTRY_DEC" -lt "$((VA_DEC + FSZ_DEC))" ]; then > + OFFSET=$(printf '0x%x' "$((ENTRY_DEC - VA_DEC + OFF_DEC))") > + break > + fi > +done << EOF > +$(readelf -lW ${REALBIN} | grep LOAD) > +EOF > + > +echo "p:myevent ${REALBIN}:${OFFSET}" >> uprobe_events > > grep -q myevent uprobe_events > test -d events/uprobes/myevent > -- > 2.20.1 -- Masami Hiramatsu (Google)