gvisor.dev/gvisor@v0.0.0-20240520182842-f9d4d51c7e0f/pkg/sentry/arch/fpu/fpu_amd64_unsafe.go (about)

     1  // Copyright 2023 The gVisor Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  //go:build amd64 || i386
    16  // +build amd64 i386
    17  
    18  package fpu
    19  
    20  import (
    21  	"unsafe"
    22  )
    23  
    24  // PrepForHostSigframe prepare the SW reserved portion of the fxsave memory
    25  // layout and adds FP_XSTATE_MAGIC2. It has to be called if the state is
    26  // restored by rt_sigreturn.
    27  //
    28  // Look at save_xstate_epilog in the kernel sources for more details.
    29  //
    30  //go:nosplit
    31  func (s State) PrepForHostSigframe() {
    32  	fpsw := (*FPSoftwareFrame)(unsafe.Pointer(&s[FP_SW_FRAME_OFFSET]))
    33  	fpsw.Magic1 = FP_XSTATE_MAGIC1
    34  	fpsw.ExtendedSize = uint32(hostFPSize) + FP_XSTATE_MAGIC2_SIZE
    35  	fpsw.Xfeatures = XFEATURE_MASK_FPSSE | hostXCR0Mask
    36  	fpsw.XstateSize = uint32(hostFPSize)
    37  
    38  	if !hostUseXsave {
    39  		return
    40  	}
    41  
    42  	*(*uint32)(unsafe.Pointer(&s[hostFPSize])) = FP_XSTATE_MAGIC2
    43  }