fix(parser): reject malformed TEXT frames and parse signed frame sizes

parser/parser.go

@@ -210,17 +210,39 @@ func (p *state) parseText(line []token.Token) {
 		rest = rest[1:]
 	}
 
-	// Frame: $number ; optional args: -number.  Whatever remains after the
-	// header is the body and is parsed by the caller.
+	// Frame: $[-]number ; optional args: -number.  The Go runtime writes
+	// zero frames with an explicit sign ("$-0-24"), so the number may carry
+	// one.  Whatever remains after the header is the body and is parsed by
+	// the caller.
 	if len(rest) > 0 && rest[0].Kind == token.Dollar {
-		text.Frame = parseOperand(rest[:2]) // "$" "number"
-		if len(rest) >= 4 && rest[2].Kind == token.Minus && rest[3].Kind == token.Number {
-			text.Args = &ast.Operand{
-				Kind: ast.OpImmediate,
-				Imm:  ast.Immediate{Val: parseInt(rest[3].Text), HasVal: true},
-				Raw:  "-" + rest[3].Text,
-				Pos:  rest[2].Pos,
+		n := 1
+		neg := false
+		if n < len(rest) && (rest[n].Kind == token.Minus || rest[n].Kind == token.Plus) {
+			neg = rest[n].Kind == token.Minus
+			n++
+		}
+		if n < len(rest) && rest[n].Kind == token.Number {
+			val := parseInt(rest[n].Text)
+			if neg {
+				val = -val
 			}
+			text.Frame = &ast.Operand{
+				Kind: ast.OpImmediate,
+				Imm:  ast.Immediate{Val: val, HasVal: true},
+				Raw:  joinRaw(rest[:n+1]),
+				Pos:  rest[0].Pos,
+			}
+			// The argument area: a minus sign followed by a number.
+			if n+2 < len(rest) && rest[n+1].Kind == token.Minus && rest[n+2].Kind == token.Number {
+				text.Args = &ast.Operand{
+					Kind: ast.OpImmediate,
+					Imm:  ast.Immediate{Val: parseInt(rest[n+2].Text), HasVal: true},
+					Raw:  "-" + rest[n+2].Text,
+					Pos:  rest[n+1].Pos,
+				}
+			}
+		} else {
+			p.errorf(rest[0].Pos, "TEXT frame size must be a number after $")
 		}
 	}
 
@@ -234,8 +256,10 @@ func (p *state) parseGlobl(line []token.Token) *ast.Globl {
 	sym, n := parseSymbolPrefix(rest)
 	g.Name = sym
 	rest = skipComma(rest[n:])
+	// Flags are identifiers (RODATA, DUPOK) or legacy numeric constants
+	// (2, 8, 9, 10) from runtime/textflag.h.
 	for len(rest) > 0 && rest[0].Kind != token.Dollar {
-		if rest[0].Kind == token.Ident {
+		if rest[0].Kind == token.Ident || rest[0].Kind == token.Number {
 			g.Flags = append(g.Flags, rest[0].Text)
 		}
 		rest = rest[1:]