[kvm-unit-tests PATCH] avoid encoding mtime in standalone scripts

[kvm-unit-tests PATCH] avoid encoding mtime in standalone scripts

[Greg Thelen]

Reproducible builds aid in caching builds and tests. Ideally rebuilding
the same source produces identical outputs.

The standalone kvm test scripts contain base64 encoded gzip compressed
test binaries. Compression and encoding is done with
"gzip -c FILE | base64" which stores FILE's name and mtime in the
compressed output.

Binaries are expanded with
  base64 -d << 'BIN_EOF' | zcat > OUTPUT
This expansion pipeline ignores the gzip stored name and mtime.

Use "gzip -n" to avoid saving mtime in the output. This makes the
standalone test scripts reproducible. Their contents are the same
regardless of when they are built.

Signed-off-by: Greg Thelen <gthelen@google.com>
---
 scripts/mkstandalone.sh | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/scripts/mkstandalone.sh b/scripts/mkstandalone.sh
index 86c7e5498246..1e6d308b43f7 100755
--- a/scripts/mkstandalone.sh
+++ b/scripts/mkstandalone.sh
@@ -16,7 +16,8 @@ temp_file ()
 	echo "cleanup=\"\$$var \$cleanup\""
 	echo "base64 -d << 'BIN_EOF' | zcat > \$$var || exit 2"
 
-	gzip -c "$file" | base64
+	# For reproductible builds avoid saving $file mtime with -n
+	gzip -nc "$file" | base64
 
 	echo "BIN_EOF"
 	echo "chmod +x \$$var"
-- 
2.39.0.rc0.267.gcb52ba06e7-goog

Re: [kvm-unit-tests PATCH] avoid encoding mtime in standalone scripts

[Andrew Jones]

On Mon, Dec 05, 2022 at 08:28:40AM -0800, Greg Thelen wrote:
> Reproducible builds aid in caching builds and tests. Ideally rebuilding
> the same source produces identical outputs.
> 
> The standalone kvm test scripts contain base64 encoded gzip compressed
> test binaries. Compression and encoding is done with
> "gzip -c FILE | base64" which stores FILE's name and mtime in the
> compressed output.
> 
> Binaries are expanded with
>   base64 -d << 'BIN_EOF' | zcat > OUTPUT
> This expansion pipeline ignores the gzip stored name and mtime.
> 
> Use "gzip -n" to avoid saving mtime in the output. This makes the
> standalone test scripts reproducible. Their contents are the same
> regardless of when they are built.
> 
> Signed-off-by: Greg Thelen <gthelen@google.com>
> ---
>  scripts/mkstandalone.sh | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/scripts/mkstandalone.sh b/scripts/mkstandalone.sh
> index 86c7e5498246..1e6d308b43f7 100755
> --- a/scripts/mkstandalone.sh
> +++ b/scripts/mkstandalone.sh
> @@ -16,7 +16,8 @@ temp_file ()
>  	echo "cleanup=\"\$$var \$cleanup\""
>  	echo "base64 -d << 'BIN_EOF' | zcat > \$$var || exit 2"
>  
> -	gzip -c "$file" | base64
> +	# For reproductible builds avoid saving $file mtime with -n
> +	gzip -nc "$file" | base64
>  
>  	echo "BIN_EOF"
>  	echo "chmod +x \$$var"
> -- 
> 2.39.0.rc0.267.gcb52ba06e7-goog
>

Reviewed-by: Andrew Jones <andrew.jones@linux.dev>