pkg/aflow/flow/patching: add bug fix patching workflow

1 files changed, 57 insertions, 0 deletions

diff --git a/pkg/aflow/flow/patching/base_commit.go b/pkg/aflow/flow/patching/base_commit.go
new file mode 100644
index 000000000..f49aba3d6
--- /dev/null
+++ b/pkg/aflow/flow/patching/base_commit.go
@@ -0,0 +1,57 @@
+// Copyright 2025 syzkaller project authors. All rights reserved.
+// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
+
+package patching
+
+import (
+	"github.com/google/syzkaller/pkg/aflow"
+	"github.com/google/syzkaller/pkg/aflow/action/kernel"
+	"github.com/google/syzkaller/pkg/vcs"
+)
+
+var baseCommitPicker = aflow.NewFuncAction("base-commit-picker", pickBaseCommit)
+
+type baseCommitArgs struct {
+	// Can be used to override the selected base commit (for manual testing).
+	FixedBaseCommit string
+}
+
+type baseCommitResult struct {
+	KernelRepo   string
+	KernelCommit string
+}
+
+func pickBaseCommit(ctx *aflow.Context, args baseCommitArgs) (baseCommitResult, error) {
+	// Currently we use the latest RC of the mainline tree as the base.
+	// This is a reasonable choice overall in lots of cases, and it enables good caching
+	// of all artifacts (we need to rebuild them only approx every week).
+	// Potentially we can use subsystem trees for few important, well-maintained subsystems
+	// (mm, net, etc). However, it will work poorly for all subsystems. First, there is no
+	// machine-usable mapping of subsystems to repo/branch; second, lots of them are poorly
+	// maintained (can be much older than latest RC); third, it will make artifact caching
+	// much worse.
+	// In the future we ought to support automated rebasing of patches to requested trees/commits.
+	// We need it anyway, but it will also alleviate imperfect base commit picking.
+	const (
+		baseRepo   = "git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git"
+		baseBranch = "master"
+	)
+
+	res := baseCommitResult{
+		KernelRepo:   baseRepo,
+		KernelCommit: args.FixedBaseCommit,
+	}
+	if args.FixedBaseCommit != "" {
+		return res, nil
+	}
+
+	err := kernel.UseLinuxRepo(ctx, func(_ string, repo vcs.Repo) error {
+		head, err := repo.Poll(baseRepo, baseBranch)
+		if err != nil {
+			return err
+		}
+		res.KernelCommit, err = repo.ReleaseTag(head.Hash)
+		return err
+	})
+	return res, err
+}