diff options
| -rw-r--r-- | pkg/ring0/kernel_amd64.go | 11 | ||||
| -rw-r--r-- | pkg/ring0/lib_amd64.go | 6 | ||||
| -rw-r--r-- | pkg/ring0/lib_amd64.s | 12 | ||||
| -rw-r--r-- | pkg/sentry/arch/fpu/fpu_amd64.go | 5 | ||||
| -rw-r--r-- | pkg/sentry/platform/kvm/BUILD | 1 | ||||
| -rw-r--r-- | pkg/sentry/platform/kvm/kvm_amd64_test.go | 30 | ||||
| -rw-r--r-- | pkg/sentry/platform/kvm/kvm_amd64_test.s | 21 |
7 files changed, 86 insertions, 0 deletions
diff --git a/pkg/ring0/kernel_amd64.go b/pkg/ring0/kernel_amd64.go index 92d2330cb..6e17fb796 100644 --- a/pkg/ring0/kernel_amd64.go +++ b/pkg/ring0/kernel_amd64.go @@ -250,6 +250,7 @@ func (c *CPU) SwitchToUser(switchOpts SwitchOpts) (vector Vector) { } SaveFloatingPoint(switchOpts.FloatingPointState.BytePointer()) // escapes: no. Copy out floating point. WriteFS(uintptr(c.registers.Fs_base)) // escapes: no. Restore kernel FS. + ldmxcsr(&kernelMXCSR) // escapes: no. Restore kernel MXCSR. return } @@ -321,3 +322,13 @@ func SetCPUIDFaulting(on bool) bool { func ReadCR2() uintptr { return readCR2() } + +// kernelMXCSR is the value of the mxcsr register in the Sentry. +// +// The MXCSR control configuration is initialized once and never changed. Look +// at src/cmd/compile/abi-internal.md in the golang sources for more details. +var kernelMXCSR uint32 + +func init() { + stmxcsr(&kernelMXCSR) +} diff --git a/pkg/ring0/lib_amd64.go b/pkg/ring0/lib_amd64.go index 0ec5c3bc5..3e6bb9663 100644 --- a/pkg/ring0/lib_amd64.go +++ b/pkg/ring0/lib_amd64.go @@ -61,6 +61,12 @@ func wrgsbase(addr uintptr) // wrgsmsr writes to the GS_BASE MSR. func wrgsmsr(addr uintptr) +// stmxcsr reads the MXCSR control and status register. +func stmxcsr(addr *uint32) + +// ldmxcsr writes to the MXCSR control and status register. +func ldmxcsr(addr *uint32) + // readCR2 reads the current CR2 value. func readCR2() uintptr diff --git a/pkg/ring0/lib_amd64.s b/pkg/ring0/lib_amd64.s index 2fe83568a..70a43e79e 100644 --- a/pkg/ring0/lib_amd64.s +++ b/pkg/ring0/lib_amd64.s @@ -198,3 +198,15 @@ TEXT ·rdmsr(SB),NOSPLIT,$0-16 MOVL AX, ret+8(FP) MOVL DX, ret+12(FP) RET + +// stmxcsr reads the MXCSR control and status register. +TEXT ·stmxcsr(SB),NOSPLIT,$0-8 + MOVQ addr+0(FP), SI + STMXCSR (SI) + RET + +// ldmxcsr writes to the MXCSR control and status register. +TEXT ·ldmxcsr(SB),NOSPLIT,$0-8 + MOVQ addr+0(FP), SI + LDMXCSR (SI) + RET diff --git a/pkg/sentry/arch/fpu/fpu_amd64.go b/pkg/sentry/arch/fpu/fpu_amd64.go index 1e9625bee..f0ba26736 100644 --- a/pkg/sentry/arch/fpu/fpu_amd64.go +++ b/pkg/sentry/arch/fpu/fpu_amd64.go @@ -219,6 +219,11 @@ func (s *State) PtraceSetXstateRegs(src io.Reader, maxlen int, featureSet *cpuid return copy(*s, f), nil } +// SetMXCSR sets the MXCSR control/status register in the state. +func (s *State) SetMXCSR(mxcsr uint32) { + hostarch.ByteOrder.PutUint32((*s)[mxcsrOffset:], mxcsr) +} + // BytePointer returns a pointer to the first byte of the state. // //go:nosplit diff --git a/pkg/sentry/platform/kvm/BUILD b/pkg/sentry/platform/kvm/BUILD index f04898dc1..47b294312 100644 --- a/pkg/sentry/platform/kvm/BUILD +++ b/pkg/sentry/platform/kvm/BUILD @@ -66,6 +66,7 @@ go_test( srcs = [ "kvm_amd64_test.go", "kvm_arm64_test.go", + "kvm_amd64_test.s", "kvm_test.go", "virtual_map_test.go", ], diff --git a/pkg/sentry/platform/kvm/kvm_amd64_test.go b/pkg/sentry/platform/kvm/kvm_amd64_test.go index e44e995a0..382953cf7 100644 --- a/pkg/sentry/platform/kvm/kvm_amd64_test.go +++ b/pkg/sentry/platform/kvm/kvm_amd64_test.go @@ -49,3 +49,33 @@ func TestSegments(t *testing.T) { return false }) } + +// stmxcsr reads the MXCSR control and status register. +func stmxcsr(addr *uint32) + +func TestMXCSR(t *testing.T) { + applicationTest(t, true, testutil.SyscallLoop, func(c *vCPU, regs *arch.Registers, pt *pagetables.PageTables) bool { + var si arch.SignalInfo + switchOpts := ring0.SwitchOpts{ + Registers: regs, + FloatingPointState: &dummyFPState, + PageTables: pt, + FullRestore: true, + } + mxcsrBefore := uint32(0) + mxcsrAfter := uint32(0) + stmxcsr(&mxcsrBefore) + switchOpts.FloatingPointState.SetMXCSR(mxcsrBefore ^ 0x8) + if _, err := c.SwitchToUser( + switchOpts, &si); err == platform.ErrContextInterrupt { + return true // Retry. + } else if err != nil { + t.Errorf("application syscall failed: %v", err) + } + stmxcsr(&mxcsrAfter) + if mxcsrAfter != mxcsrBefore { + t.Errorf("mxcsr = %x (expected %x)", mxcsrBefore, mxcsrAfter) + } + return false + }) +} diff --git a/pkg/sentry/platform/kvm/kvm_amd64_test.s b/pkg/sentry/platform/kvm/kvm_amd64_test.s new file mode 100644 index 000000000..8e9079867 --- /dev/null +++ b/pkg/sentry/platform/kvm/kvm_amd64_test.s @@ -0,0 +1,21 @@ +// 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. + +#include "textflag.h" + +// stmxcsr reads the MXCSR control and status register. +TEXT ·stmxcsr(SB),NOSPLIT,$0-8 + MOVQ addr+0(FP), SI + STMXCSR (SI) + RET |