diff options
author | Jamie Liu <jamieliu@google.com> | 2021-09-01 14:04:50 -0700 |
---|---|---|
committer | gVisor bot <gvisor-bot@google.com> | 2021-09-01 14:07:57 -0700 |
commit | b4de26d6b1bbb0e75187690da6d3fe120f53656b (patch) | |
tree | f34266f08c7ea44369231969b48aacc733910399 | |
parent | 702fe7d60da4d38344f00200187fe1f0766bef8d (diff) |
Don't use reflection in fpu.alignedBytes.
reflect.ValueOf takes an interface{}, so when passed a slice the compiler emits
a call to runtime.convTslice to heap-allocate a copy of the slice header.
PiperOrigin-RevId: 394310052
-rw-r--r-- | pkg/sentry/arch/fpu/BUILD | 1 | ||||
-rw-r--r-- | pkg/sentry/arch/fpu/fpu.go | 13 | ||||
-rw-r--r-- | pkg/sentry/arch/fpu/fpu_unsafe.go | 31 |
3 files changed, 32 insertions, 13 deletions
diff --git a/pkg/sentry/arch/fpu/BUILD b/pkg/sentry/arch/fpu/BUILD index 6cdd21b1b..1f371e513 100644 --- a/pkg/sentry/arch/fpu/BUILD +++ b/pkg/sentry/arch/fpu/BUILD @@ -9,6 +9,7 @@ go_library( "fpu_amd64.go", "fpu_amd64.s", "fpu_arm64.go", + "fpu_unsafe.go", ], visibility = ["//:sandbox"], deps = [ diff --git a/pkg/sentry/arch/fpu/fpu.go b/pkg/sentry/arch/fpu/fpu.go index 867d309a3..62bde19d3 100644 --- a/pkg/sentry/arch/fpu/fpu.go +++ b/pkg/sentry/arch/fpu/fpu.go @@ -17,7 +17,6 @@ package fpu import ( "fmt" - "reflect" ) // State represents floating point state. @@ -40,15 +39,3 @@ type ErrLoadingState struct { func (e ErrLoadingState) Error() string { return fmt.Sprintf("floating point state contains unsupported features; supported: %#x saved: %#x", e.supportedFeatures, e.savedFeatures) } - -// alignedBytes returns a slice of size bytes, aligned in memory to the given -// alignment. This is used because we require certain structures to be aligned -// in a specific way (for example, the X86 floating point data). -func alignedBytes(size, alignment uint) []byte { - data := make([]byte, size+alignment-1) - offset := uint(reflect.ValueOf(data).Index(0).Addr().Pointer() % uintptr(alignment)) - if offset == 0 { - return data[:size:size] - } - return data[alignment-offset:][:size:size] -} diff --git a/pkg/sentry/arch/fpu/fpu_unsafe.go b/pkg/sentry/arch/fpu/fpu_unsafe.go new file mode 100644 index 000000000..c91dc99be --- /dev/null +++ b/pkg/sentry/arch/fpu/fpu_unsafe.go @@ -0,0 +1,31 @@ +// Copyright 2021 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 fpu + +import ( + "unsafe" +) + +// alignedBytes returns a slice of size bytes, aligned in memory to the given +// alignment. This is used because we require certain structures to be aligned +// in a specific way (for example, the X86 floating point data). +func alignedBytes(size, alignment uint) []byte { + data := make([]byte, size+alignment-1) + offset := uint(uintptr(unsafe.Pointer(&data[0])) % uintptr(alignment)) + if offset == 0 { + return data[:size:size] + } + return data[alignment-offset:][:size:size] +} |