From c7918378631992d874c99736272ed342d5d77b2c Mon Sep 17 00:00:00 2001
From: Dmitry Vyukov <dvyukov@google.com>
Date: Sat, 8 Dec 2018 19:03:09 +0100
Subject: executor: fix handling of big-endian bitfields

Currently we apply big-endian-ness and bitfield-ness in the wrong order in copyin.
This leads to totally bogus result. Fix this.
---
 pkg/compiler/check.go            |  3 ++-
 pkg/compiler/testdata/errors.txt |  1 +
 pkg/compiler/types.go            | 18 ++++++++++++++----
 3 files changed, 17 insertions(+), 5 deletions(-)

(limited to 'pkg/compiler')

diff --git a/pkg/compiler/check.go b/pkg/compiler/check.go
index 6ec2fa9e2..cc0535449 100644
--- a/pkg/compiler/check.go
+++ b/pkg/compiler/check.go
@@ -751,7 +751,8 @@ func (comp *compiler) checkTypeBasic(t *ast.Type, desc *typeDesc, flags checkFla
 		comp.error(t.Pos, "%v can't be type alias target", t.Ident)
 		return
 	}
-	if flags&checkIsResourceBase != 0 && !desc.ResourceBase {
+	if flags&checkIsResourceBase != 0 &&
+		(desc.CanBeResourceBase == nil || !desc.CanBeResourceBase(comp, t)) {
 		comp.error(t.Pos, "%v can't be resource base (int types can)", t.Ident)
 		return
 	}
diff --git a/pkg/compiler/testdata/errors.txt b/pkg/compiler/testdata/errors.txt
index fed520e6e..55ec40901 100644
--- a/pkg/compiler/testdata/errors.txt
+++ b/pkg/compiler/testdata/errors.txt
@@ -65,6 +65,7 @@ resource r2[r0]: 2
 resource r3[int32:1]		###  unexpected ':', only struct fields can be bitfields
 resource r4[int32[opt]]		### resource base can't be marked as opt
 resource r5[non_existent]	### unknown type non_existent
+resource r6[int64be]		### int64be can't be resource base (int types can)
 resource r9["foo"]		### unexpected string "foo", expect type
 
 foo$7(a r0, a1 r2[opt])
diff --git a/pkg/compiler/types.go b/pkg/compiler/types.go
index 98edc9d74..30ff8884a 100644
--- a/pkg/compiler/types.go
+++ b/pkg/compiler/types.go
@@ -18,11 +18,12 @@ type typeDesc struct {
 	CantBeOpt    bool       // can't be marked as opt?
 	NeedBase     bool       // needs base type when used as field?
 	AllowColon   bool       // allow colon (int8:2) on fields?
-	ResourceBase bool       // can be resource base type?
 	OptArgs      int        // number of optional arguments in Args array
 	Args         []namedArg // type arguments
 	// CanBeArgRet returns if this type can be syscall argument/return (false if nil).
 	CanBeArgRet func(comp *compiler, t *ast.Type) (bool, bool)
+	// CanBeResourceBase returns if this type can be a resource base type (false if nil.
+	CanBeResourceBase func(comp *compiler, t *ast.Type) bool
 	// Check does custom verification of the type (optional, consts are not patched yet).
 	Check func(comp *compiler, t *ast.Type, args []*ast.Type, base prog.IntTypeCommon)
 	// CheckConsts does custom verification of the type (optional, consts are patched).
@@ -67,9 +68,16 @@ var typeInt = &typeDesc{
 	CanBeArgRet:  canBeArg,
 	CanBeTypedef: true,
 	AllowColon:   true,
-	ResourceBase: true,
 	OptArgs:      1,
 	Args:         []namedArg{{Name: "range", Type: typeArgIntRange}},
+	CanBeResourceBase: func(comp *compiler, t *ast.Type) bool {
+		// Big-endian resources can always be converted to non-big-endian,
+		// since we will always revert bytes during copyout and during copyin,
+		// so the result is the same as not reverting at all.
+		// Big-endian resources are also not implemented and don't have tests.
+		_, be := comp.parseIntType(t.Ident)
+		return !be
+	},
 	Check: func(comp *compiler, t *ast.Type, args []*ast.Type, base prog.IntTypeCommon) {
 		typeArgBase.Type.Check(comp, t)
 	},
@@ -653,8 +661,10 @@ var typeArgType = &typeArg{}
 
 var typeResource = &typeDesc{
 	// No Names, but getTypeDesc knows how to match it.
-	CanBeArgRet:  canBeArgRet,
-	ResourceBase: true,
+	CanBeArgRet: canBeArgRet,
+	CanBeResourceBase: func(comp *compiler, t *ast.Type) bool {
+		return true
+	},
 	// Gen is assigned below to avoid initialization loop.
 }
 
-- 
cgit mrf-deployment