pkg/subsystem: add the basic caller-facing interface

Users of the pkg/subsystem are only interested in
1) Fetching the list of subsystems for a given OS.
2) Matching a crash against the extracted set of subsystems.

1 files changed, 48 insertions, 0 deletions

diff --git a/pkg/subsystem/raw_extractor.go b/pkg/subsystem/raw_extractor.go
new file mode 100644
index 000000000..4a86b1f6b
--- /dev/null
+++ b/pkg/subsystem/raw_extractor.go
@@ -0,0 +1,48 @@
+// Copyright 2023 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 subsystem
+
+import (
+	"github.com/google/syzkaller/pkg/subsystem/entity"
+	"github.com/google/syzkaller/pkg/subsystem/match"
+	"github.com/google/syzkaller/prog"
+)
+
+// rawExtractor performs low-level subsystem matching (directly by a path or a syscall).
+type rawExtractor struct {
+	matcher *match.PathMatcher
+	perCall map[string][]*entity.Subsystem
+}
+
+func makeRawExtractor(list []*entity.Subsystem) *rawExtractor {
+	ret := &rawExtractor{
+		matcher: match.MakePathMatcher(list),
+		perCall: make(map[string][]*entity.Subsystem),
+	}
+	for _, subsystem := range list {
+		for _, call := range subsystem.Syscalls {
+			ret.perCall[call] = append(ret.perCall[call], subsystem)
+		}
+	}
+	return ret
+}
+
+func (e *rawExtractor) FromPath(path string) []*entity.Subsystem {
+	return e.matcher.Match(path)
+}
+
+func (e *rawExtractor) FromProg(progBytes []byte) []*entity.Subsystem {
+	calls := make(map[*entity.Subsystem]struct{})
+	progCalls, _, _ := prog.CallSet(progBytes)
+	for call := range progCalls {
+		for _, subsystem := range e.perCall[call] {
+			calls[subsystem] = struct{}{}
+		}
+	}
+	list := []*entity.Subsystem{}
+	for key := range calls {
+		list = append(list, key)
+	}
+	return list
+}