cmd/asm: improve DATA size operand validation

Prior to this change, DATA instructions accepted
the values 1, 2, 4, and 8 as sizes.
The acceptable sizes were further restricted
to 4 and 8 for float constants.

This was both too restrictive and not restrictive enough:
string constants may reasonably have any length,
and address constants should really only accept pointer-length sizes.

Fixes #30269

Change-Id: I06e44ecdf5909eca7b19553861aec1fa39655c2b
Reviewed-on: https://go-review.googlesource.com/c/163747
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

src/cmd/asm/internal/asm/asm.go

@@ -7,6 +7,7 @@ package asm
 import (
 	"bytes"
 	"fmt"
+	"strconv"
 	"text/scanner"
 
 	"cmd/asm/internal/arch"
@@ -200,7 +201,11 @@ func (p *Parser) asmData(operands [][]lex.Token) {
 		p.errorf("expect /size for DATA argument")
 		return
 	}
-	scale := p.parseScale(op[n-1].String())
+	szop := op[n-1].String()
+	sz, err := strconv.Atoi(szop)
+	if err != nil {
+		p.errorf("bad size for DATA argument: %q", szop)
+	}
 	op = op[:n-2]
 	nameAddr := p.address(op)
 	if !p.validSymbol("DATA", &nameAddr, true) {
@@ -223,24 +228,33 @@ func (p *Parser) asmData(operands [][]lex.Token) {
 		p.errorf("overlapping DATA entry for %s", name)
 		return
 	}
-	p.dataAddr[name] = nameAddr.Offset + int64(scale)
+	p.dataAddr[name] = nameAddr.Offset + int64(sz)
 
 	switch valueAddr.Type {
 	case obj.TYPE_CONST:
-		nameAddr.Sym.WriteInt(p.ctxt, nameAddr.Offset, int(scale), valueAddr.Offset)
+		switch sz {
+		case 1, 2, 4, 8:
+			nameAddr.Sym.WriteInt(p.ctxt, nameAddr.Offset, int(sz), valueAddr.Offset)
+		default:
+			p.errorf("bad int size for DATA argument: %d", sz)
+		}
 	case obj.TYPE_FCONST:
-		switch scale {
+		switch sz {
 		case 4:
 			nameAddr.Sym.WriteFloat32(p.ctxt, nameAddr.Offset, float32(valueAddr.Val.(float64)))
 		case 8:
 			nameAddr.Sym.WriteFloat64(p.ctxt, nameAddr.Offset, valueAddr.Val.(float64))
 		default:
-			panic("bad float scale")
+			p.errorf("bad float size for DATA argument: %d", sz)
 		}
 	case obj.TYPE_SCONST:
-		nameAddr.Sym.WriteString(p.ctxt, nameAddr.Offset, int(scale), valueAddr.Val.(string))
+		nameAddr.Sym.WriteString(p.ctxt, nameAddr.Offset, int(sz), valueAddr.Val.(string))
 	case obj.TYPE_ADDR:
-		nameAddr.Sym.WriteAddr(p.ctxt, nameAddr.Offset, int(scale), valueAddr.Sym, valueAddr.Offset)
+		if sz == p.arch.PtrSize {
+			nameAddr.Sym.WriteAddr(p.ctxt, nameAddr.Offset, int(sz), valueAddr.Sym, valueAddr.Offset)
+		} else {
+			p.errorf("bad addr size for DATA argument: %d", sz)
+		}
 	}
 }
 

src/cmd/asm/internal/asm/pseudo_test.go

@@ -43,6 +43,13 @@ func TestErroneous(t *testing.T) {
 		{"DATA", "0", "expect two operands for DATA"},
 		{"DATA", "(0), 1", "expect /size for DATA argument"},
 		{"DATA", "@B(SB)/4,0", "expected '(', found B"}, // Issue 23580.
+		{"DATA", "·A(SB)/4,0", "DATA value must be an immediate constant or address"},
+		{"DATA", "·B(SB)/4,$0", ""},
+		{"DATA", "·C(SB)/5,$0", "bad int size for DATA argument: 5"},
+		{"DATA", "·D(SB)/5,$0.0", "bad float size for DATA argument: 5"},
+		{"DATA", "·E(SB)/4,$·A(SB)", "bad addr size for DATA argument: 4"},
+		{"DATA", "·F(SB)/8,$·A(SB)", ""},
+		{"DATA", "·G(SB)/5,$\"abcde\"", ""},
 		{"GLOBL", "", "expect two or three operands for GLOBL"},
 		{"GLOBL", "0,1", "GLOBL symbol \"<erroneous symbol>\" must be a symbol(SB)"},
 		{"GLOBL", "@B(SB), 0", "expected '(', found B"}, // Issue 23580.