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Diffstat (limited to 'tools/go_marshal/analysis/analysis_unsafe.go')
| -rw-r--r-- | tools/go_marshal/analysis/analysis_unsafe.go | 175 |
1 files changed, 0 insertions, 175 deletions
diff --git a/tools/go_marshal/analysis/analysis_unsafe.go b/tools/go_marshal/analysis/analysis_unsafe.go deleted file mode 100644 index 9a9a4f298..000000000 --- a/tools/go_marshal/analysis/analysis_unsafe.go +++ /dev/null @@ -1,175 +0,0 @@ -// Copyright 2019 The gVisor Authors. -// -// Licensed under the Apache License, Version 2.0 (the "License"); -// you may not use this file except in compliance with the License. -// You may obtain a copy of the License at -// -// http://www.apache.org/licenses/LICENSE-2.0 -// -// Unless required by applicable law or agreed to in writing, software -// distributed under the License is distributed on an "AS IS" BASIS, -// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -// See the License for the specific language governing permissions and -// limitations under the License. - -// Package analysis implements common functionality used by generated -// go_marshal tests. -package analysis - -// All functions in this package are unsafe and are not intended for general -// consumption. They contain sharp edge cases and the caller is responsible for -// ensuring none of them are hit. Callers must be carefully to pass in only sane -// arguments. Failure to do so may cause panics at best and arbitrary memory -// corruption at worst. -// -// Never use outside of tests. - -import ( - "fmt" - "math/rand" - "reflect" - "testing" - "unsafe" -) - -// RandomizeValue assigns random value(s) to an abitrary type. This is intended -// for used with ABI structs from go_marshal, meaning the typical restrictions -// apply (fixed-size types, no pointers, maps, channels, etc), and should only -// be used on zeroed values to avoid overwriting pointers to active go objects. -// -// Internally, we populate the type with random data by doing an unsafe cast to -// access the underlying memory of the type and filling it as if it were a byte -// slice. This almost gets us what we want, but padding fields named "_" are -// normally not accessible, so we walk the type and recursively zero all "_" -// fields. -// -// Precondition: x must be a pointer. x must not contain any valid -// pointers to active go objects (pointer fields aren't allowed in ABI -// structs anyways), or we'd be violating the go runtime contract and -// the GC may malfunction. -func RandomizeValue(x interface{}) { - v := reflect.Indirect(reflect.ValueOf(x)) - if !v.CanSet() { - panic("RandomizeType() called with an unaddressable value. You probably need to pass a pointer to the argument") - } - - // Cast the underlying memory for the type into a byte slice. - var b []byte - hdr := (*reflect.SliceHeader)(unsafe.Pointer(&b)) - // Note: v.UnsafeAddr panics if x is passed by value. x should be a pointer. - hdr.Data = v.UnsafeAddr() - hdr.Len = int(v.Type().Size()) - hdr.Cap = hdr.Len - - // Fill the byte slice with random data, which in effect fills the type with - // random values. - n, err := rand.Read(b) - if err != nil || n != len(b) { - panic("unreachable") - } - - // Normally, padding fields are not accessible, so zero them out. - reflectZeroPaddingFields(v.Type(), b, false) -} - -// reflectZeroPaddingFields assigns zero values to padding fields for the value -// of type r, represented by the memory in data. Padding fields are defined as -// fields with the name "_". If zero is true, the immediate value itself is -// zeroed. In addition, the type is recursively scanned for padding fields in -// inner types. -// -// This is used for zeroing padding fields after calling RandomizeValue. -func reflectZeroPaddingFields(r reflect.Type, data []byte, zero bool) { - if zero { - for i, _ := range data { - data[i] = 0 - } - } - switch r.Kind() { - case reflect.Int8, reflect.Uint8, reflect.Int16, reflect.Uint16, reflect.Int32, reflect.Uint32, reflect.Int64, reflect.Uint64: - // These types are explicitly allowed in an ABI type, but we don't need - // to recurse further as they're scalar types. - case reflect.Struct: - for i, numFields := 0, r.NumField(); i < numFields; i++ { - f := r.Field(i) - off := f.Offset - len := f.Type.Size() - window := data[off : off+len] - reflectZeroPaddingFields(f.Type, window, f.Name == "_") - } - case reflect.Array: - eLen := int(r.Elem().Size()) - if int(r.Size()) != eLen*r.Len() { - panic("Array has unexpected size?") - } - for i, n := 0, r.Len(); i < n; i++ { - reflectZeroPaddingFields(r.Elem(), data[i*eLen:(i+1)*eLen], false) - } - default: - panic(fmt.Sprintf("Type %v not allowed in ABI struct", r.Kind())) - - } -} - -// AlignmentCheck ensures the definition of the type represented by typ doesn't -// cause the go compiler to emit implicit padding between elements of the type -// (i.e. fields in a struct). -// -// AlignmentCheck doesn't explicitly recurse for embedded structs because any -// struct present in an ABI struct must also be Marshallable, and therefore -// they're aligned by definition (or their alignment check would have failed). -func AlignmentCheck(t *testing.T, typ reflect.Type) (ok bool, delta uint64) { - switch typ.Kind() { - case reflect.Int8, reflect.Uint8, reflect.Int16, reflect.Uint16, reflect.Int32, reflect.Uint32, reflect.Int64, reflect.Uint64: - // Primitive types are always considered well aligned. Primitive types - // that are fields in structs are checked independently, this branch - // exists to handle recursive calls to alignmentCheck. - case reflect.Struct: - xOff := 0 - nextXOff := 0 - skipNext := false - for i, numFields := 0, typ.NumField(); i < numFields; i++ { - xOff = nextXOff - f := typ.Field(i) - fmt.Printf("Checking alignment of %s.%s @ %d [+%d]...\n", typ.Name(), f.Name, f.Offset, f.Type.Size()) - nextXOff = int(f.Offset + f.Type.Size()) - - if f.Name == "_" { - // Padding fields need not be aligned. - fmt.Printf("Padding field of type %v\n", f.Type) - continue - } - - if tag, ok := f.Tag.Lookup("marshal"); ok && tag == "unaligned" { - skipNext = true - continue - } - - if skipNext { - skipNext = false - fmt.Printf("Skipping alignment check for field %s.%s explicitly marked as unaligned.\n", typ.Name(), f.Name) - continue - } - - if xOff != int(f.Offset) { - implicitPad := int(f.Offset) - xOff - t.Fatalf("Suspect offset for field %s.%s, detected an implicit %d byte padding from offset %d to %d; either add %d bytes of explicit padding before this field or tag it as `marshal:\"unaligned\"`.", typ.Name(), f.Name, implicitPad, xOff, f.Offset, implicitPad) - } - } - - // Ensure structs end on a byte explicitly defined by the type. - if typ.NumField() > 0 && nextXOff != int(typ.Size()) { - implicitPad := int(typ.Size()) - nextXOff - f := typ.Field(typ.NumField() - 1) // Final field - t.Fatalf("Suspect offset for field %s.%s at the end of %s, detected an implicit %d byte padding from offset %d to %d at the end of the struct; either add %d bytes of explict padding at end of the struct or tag the final field %s as `marshal:\"unaligned\"`.", - typ.Name(), f.Name, typ.Name(), implicitPad, nextXOff, typ.Size(), implicitPad, f.Name) - } - case reflect.Array: - // Independent arrays are also always considered well aligned. We only - // need to worry about their alignment when they're embedded in structs, - // which we handle above. - default: - t.Fatalf("Unsupported type in ABI struct while checking for field alignment for type: %v", typ.Kind()) - } - return true, uint64(typ.Size()) -} |