pkg/build: make linux builds more deterministic

Kbuild inserts build timestamp into every build.
This makes vmlinux change always even if no present.
Make the build more deterministic.
We plan to use it for detecting no-op changes during bisection.

Update #1271

1 files changed, 10 insertions, 0 deletions

diff --git a/pkg/build/linux.go b/pkg/build/linux.go
index 735118a1a..b9301d3d9 100644
--- a/pkg/build/linux.go
+++ b/pkg/build/linux.go
@@ -128,6 +128,16 @@ func runMake(kernelDir string, args ...string) error {
 		return err
 	}
 	cmd.Dir = kernelDir
+	cmd.Env = append([]string{}, os.Environ()...)
+	// This makes the build [more] deterministic:
+	// 2 builds from the same sources should result in the same vmlinux binary.
+	// We plan to use it for detecting no-op changes during bisection.
+	cmd.Env = append(cmd.Env,
+		"KBUILD_BUILD_VERSION=0",
+		"KBUILD_BUILD_TIMESTAMP=now",
+		"KBUILD_BUILD_USER=syzkaller",
+		"KBUILD_BUILD_HOST=syzkaller",
+	)
 	_, err := osutil.Run(time.Hour, cmd)
 	return err
 }