linux-kernel - Re: [PATCH v2 59/62] livepatch/klp-build: Introduce klp-build script for generating livepatch modules

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Message-ID: <8c79b86e-fc30-4f48-bdd2-91ef6f612bb5@redhat.com>
Date: Wed, 11 Jun 2025 14:44:35 -0400
From: Joe Lawrence <joe.lawrence@...hat.com>
To: Josh Poimboeuf <jpoimboe@...nel.org>, x86@...nel.org
Cc: linux-kernel@...r.kernel.org, Petr Mladek <pmladek@...e.com>,
 Miroslav Benes <mbenes@...e.cz>, live-patching@...r.kernel.org,
 Song Liu <song@...nel.org>, laokz <laokz@...mail.com>,
 Jiri Kosina <jikos@...nel.org>, Marcos Paulo de Souza <mpdesouza@...e.com>,
 Weinan Liu <wnliu@...gle.com>, Fazla Mehrab <a.mehrab@...edance.com>,
 Chen Zhongjin <chenzhongjin@...wei.com>, Puranjay Mohan <puranjay@...nel.org>
Subject: Re: [PATCH v2 59/62] livepatch/klp-build: Introduce klp-build script
 for generating livepatch modules

On 5/9/25 4:17 PM, Josh Poimboeuf wrote:
> Add a klp-build script which automates the generation of a livepatch
> module from a source .patch file by performing the following steps:
> 
>   - Builds an original kernel with -function-sections and
>     -fdata-sections, plus objtool function checksumming.
> 
>   - Applies the .patch file and rebuilds the kernel using the same
>     options.
> 
>   - Runs 'objtool klp diff' to detect changed functions and generate
>     intermediate binary diff objects.
> 
>   - Builds a kernel module which links the diff objects with some
>     livepatch module init code (scripts/livepatch/init.c).
> 
>   - Finalizes the livepatch module (aka work around linker wreckage)
>     using 'objtool klp post-link'.
> 
> Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
> ---
>  scripts/livepatch/klp-build | 697 ++++++++++++++++++++++++++++++++++++
> ...
> +get_patch_files() {
> +	local patch="$1"
> +
> +	grep0 -E '^(--- |\+\+\+ )' "$patch"			\
> +		| gawk '{print $2}'				\

If we split the rest of this line on the tab character and print the
first part of $2:

  gawk '{ split($2, a, "\t"); print a[1] }'

then it can additionally handle patches generated by `diff -Nupr` with a
timepstamp ("--- <filepath>\t<timestamp>").

> +# Refresh the patch hunk headers, specifically the line numbers and counts.
> +refresh_patch() {
> +	local patch="$1"
> +	local tmpdir="$PATCH_TMP_DIR"
> +	local files=()
> +
> +	rm -rf "$tmpdir"
> +	mkdir -p "$tmpdir/a"
> +	mkdir -p "$tmpdir/b"
> +
> +	# Find all source files affected by the patch
> +	grep0 -E '^(--- |\+\+\+ )[^ /]+' "$patch"	|
> +		sed -E 's/(--- |\+\+\+ )[^ /]+\///'	|
> +		sort | uniq | mapfile -t files
> +

Should just call `get_patch_files() here?

-- 
Joe