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

7 files changed, 45 insertions, 2 deletions

diff --git a/pkg/ast/ast.go b/pkg/ast/ast.go
index 66dfc11bd..f0403a07b 100644
--- a/pkg/ast/ast.go
+++ b/pkg/ast/ast.go
@@ -46,6 +46,15 @@ func (n *Comment) Info() (Pos, string, string) {
 	return n.Pos, tok2str[tokComment], ""
 }
 
+type Meta struct {
+	Pos   Pos
+	Value *Type
+}
+
+func (n *Meta) Info() (Pos, string, string) {
+	return n.Pos, "meta", n.Value.Ident
+}
+
 type Include struct {
 	Pos  Pos
 	File *String
diff --git a/pkg/ast/clone.go b/pkg/ast/clone.go
index 23e4f421c..0c9c831f0 100644
--- a/pkg/ast/clone.go
+++ b/pkg/ast/clone.go
@@ -24,6 +24,13 @@ func (n *Comment) Clone() Node {
 	}
 }
 
+func (n *Meta) Clone() Node {
+	return &Meta{
+		Pos:   n.Pos,
+		Value: n.Value.Clone().(*Type),
+	}
+}
+
 func (n *Include) Clone() Node {
 	return &Include{
 		Pos:  n.Pos,
diff --git a/pkg/ast/format.go b/pkg/ast/format.go
index 51538eaf1..f4a01d37b 100644
--- a/pkg/ast/format.go
+++ b/pkg/ast/format.go
@@ -74,6 +74,12 @@ func (n *Comment) serialize(w io.Writer) {
 	fmt.Fprintf(w, "#%v\n", strings.TrimRight(n.Text, " \t"))
 }
 
+func (n *Meta) serialize(w io.Writer) {
+	fmt.Fprintf(w, "meta ")
+	n.Value.serialize(w)
+	fmt.Fprintf(w, "\n")
+}
+
 func (n *Include) serialize(w io.Writer) {
 	fmt.Fprintf(w, "include <%v>\n", n.File.Value)
 }
diff --git a/pkg/ast/parser.go b/pkg/ast/parser.go
index 20898169e..b2709e2ed 100644
--- a/pkg/ast/parser.go
+++ b/pkg/ast/parser.go
@@ -128,7 +128,10 @@ func (p *parser) parseTop() Node {
 		return p.parseResource()
 	case tokIdent:
 		name := p.parseIdent()
-		if name.Name == "type" {
+		switch name.Name {
+		case "meta":
+			return p.parseMeta()
+		case "type":
 			return p.parseTypeDef()
 		}
 		switch p.tok {
@@ -190,6 +193,13 @@ func (p *parser) parseComment() *Comment {
 	return c
 }
 
+func (p *parser) parseMeta() *Meta {
+	return &Meta{
+		Pos:   p.pos,
+		Value: p.parseType(),
+	}
+}
+
 func (p *parser) parseDefine() *Define {
 	pos0 := p.pos
 	p.consume(tokDefine)
diff --git a/pkg/ast/testdata/all.txt b/pkg/ast/testdata/all.txt
index c9398a830..7b5fa7c37 100644
--- a/pkg/ast/testdata/all.txt
+++ b/pkg/ast/testdata/all.txt
@@ -1,4 +1,7 @@
 # Copyright 2017 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.
 
+meta noextract
+meta arches["foo", "bar", "386"]
+
 incdir <some/path>
diff --git a/pkg/ast/testdata/errors.txt b/pkg/ast/testdata/errors.txt
index 463158756..2b022c149 100644
--- a/pkg/ast/testdata/errors.txt
+++ b/pkg/ast/testdata/errors.txt
@@ -5,6 +5,10 @@
 foo		### unexpected '\n', expecting '(', '{', '[', '='
 %		### illegal character U+0025 '%'
 
+meta		### unexpected '\n', expecting int, identifier, string
+meta: foo	### unexpected ':', expecting int, identifier, string
+meta foo, bar	### unexpected ',', expecting '\n'
+
 int_flags0 = 0, 0x1, 0xab
 int_flags1 = 123ab0x			### bad integer "123ab0x"
 int_flags1 == 0, 1			### unexpected '=', expecting int, identifier, string
@@ -93,4 +97,4 @@ s5 {
 	f0 int8 (	### unexpected '\n', expecting int, identifier, string
 
 s6 {
-	f0 int8 ()	### unexpected ')', expecting int, identifier, string
\ No newline at end of file
+	f0 int8 ()	### unexpected ')', expecting int, identifier, string
diff --git a/pkg/ast/walk.go b/pkg/ast/walk.go
index 84a3c67c3..b187769f3 100644
--- a/pkg/ast/walk.go
+++ b/pkg/ast/walk.go
@@ -35,6 +35,10 @@ func (n *Ident) walk(cb func(Node))   {}
 func (n *String) walk(cb func(Node))  {}
 func (n *Int) walk(cb func(Node))     {}
 
+func (n *Meta) walk(cb func(Node)) {
+	cb(n.Value)
+}
+
 func (n *Include) walk(cb func(Node)) {
 	cb(n.File)
 }