pkg/ast, pkg/compiler: support per-file metadata

We have a bunch of hacks in syz-extract, syz-sysgen and syz-check
with respect to description files unsupported on some arches,
or that must not be part of make extract.

Add 2 meta attribtues to files:

meta noextract
Tells `make extract` to not extract constants for this file.
Though, `syz-extract` can still be invoked manually on this file.

meta arches["arch1", "arch2"]
Restricts this file only to the given set of architectures.
`make extract` and ``make generate` will not use it on other architectures.

Later we can potentially use meta attributes to specify git tree/commit
that must be used for extraction. Maybe something else.

Fixes #2754

1 files changed, 88 insertions, 0 deletions

diff --git a/pkg/compiler/meta.go b/pkg/compiler/meta.go
new file mode 100644
index 000000000..f0221d0b9
--- /dev/null
+++ b/pkg/compiler/meta.go
@@ -0,0 +1,88 @@
+// Copyright 2022 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 compiler
+
+import (
+	"path/filepath"
+
+	"github.com/google/syzkaller/pkg/ast"
+	"github.com/google/syzkaller/sys/targets"
+)
+
+type Meta struct {
+	NoExtract bool
+	Arches    map[string]bool
+}
+
+func (meta *Meta) SupportsArch(arch string) bool {
+	return len(meta.Arches) == 0 || meta.Arches[arch]
+}
+
+func FileList(desc *ast.Description, OS string, eh ast.ErrorHandler) map[string]Meta {
+	// Use any target for this OS.
+	for _, target := range targets.List[OS] {
+		return createCompiler(desc, target, eh).fileList()
+	}
+	return nil
+}
+
+func (comp *compiler) fileList() map[string]Meta {
+	files := make(map[string]Meta)
+	for _, n := range comp.desc.Nodes {
+		pos, _, _ := n.Info()
+		file := filepath.Base(pos.File)
+		if file == ast.BuiltinFile {
+			continue
+		}
+		meta := files[file]
+		switch n := n.(type) {
+		case *ast.Meta:
+			errors0 := comp.errors
+			comp.checkTypeImpl(checkCtx{}, n.Value, metaTypes[n.Value.Ident], 0)
+			if errors0 != comp.errors {
+				break
+			}
+			switch n.Value.Ident {
+			case metaNoExtract.Names[0]:
+				meta.NoExtract = true
+			case metaArches.Names[0]:
+				meta.Arches = make(map[string]bool)
+				for _, arg := range n.Value.Args {
+					meta.Arches[arg.String] = true
+				}
+			}
+		}
+		files[file] = meta
+	}
+	if comp.errors != 0 {
+		return nil
+	}
+	return files
+}
+
+var metaTypes = map[string]*typeDesc{
+	metaNoExtract.Names[0]: metaNoExtract,
+	metaArches.Names[0]:    metaArches,
+}
+
+var metaNoExtract = &typeDesc{
+	Names:     []string{"noextract"},
+	CantBeOpt: true,
+}
+
+var metaArches = &typeDesc{
+	Names:     []string{"arches"},
+	CantBeOpt: true,
+	OptArgs:   8,
+	Args:      []namedArg{metaArch, metaArch, metaArch, metaArch, metaArch, metaArch, metaArch, metaArch},
+}
+
+var metaArch = namedArg{Name: "arch", Type: &typeArg{
+	Kind: kindString,
+	Check: func(comp *compiler, t *ast.Type) {
+		if targets.List[comp.target.OS][t.String] == nil {
+			comp.error(t.Pos, "unknown arch %v", t.String)
+		}
+	},
+}}