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// Copyright 2020 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.
// +build arm64
package arch
import (
"golang.org/x/sys/unix"
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/hostarch"
"gvisor.dev/gvisor/pkg/log"
"gvisor.dev/gvisor/pkg/sentry/arch/fpu"
)
// SignalContext64 is equivalent to struct sigcontext, the type passed as the
// second argument to signal handlers set by signal(2).
//
// +marshal
type SignalContext64 struct {
FaultAddr uint64
Regs [31]uint64
Sp uint64
Pc uint64
Pstate uint64
_pad [8]byte // __attribute__((__aligned__(16)))
Fpsimd64 FpsimdContext // size = 528
}
// +marshal
type aarch64Ctx struct {
Magic uint32
Size uint32
}
// FpsimdContext is equivalent to struct fpsimd_context on arm64
// (arch/arm64/include/uapi/asm/sigcontext.h).
//
// +marshal
type FpsimdContext struct {
Head aarch64Ctx
Fpsr uint32
Fpcr uint32
Vregs [64]uint64 // actually [32]uint128
}
// UContext64 is equivalent to ucontext on arm64(arch/arm64/include/uapi/asm/ucontext.h).
//
// +marshal
type UContext64 struct {
Flags uint64
Link uint64
Stack linux.SignalStack
Sigset linux.SignalSet
// glibc uses a 1024-bit sigset_t
_pad [120]byte // (1024 - 64) / 8 = 120
// sigcontext must be aligned to 16-byte
_pad2 [8]byte
// last for future expansion
MContext SignalContext64
}
// SignalSetup implements Context.SignalSetup.
func (c *context64) SignalSetup(st *Stack, act *linux.SigAction, info *linux.SignalInfo, alt *linux.SignalStack, sigset linux.SignalSet) error {
sp := st.Bottom
// Construct the UContext64 now since we need its size.
uc := &UContext64{
Flags: 0,
Stack: *alt,
MContext: SignalContext64{
Regs: c.Regs.Regs,
Sp: c.Regs.Sp,
Pc: c.Regs.Pc,
Pstate: c.Regs.Pstate,
},
Sigset: sigset,
}
if linux.Signal(info.Signo) == linux.SIGSEGV || linux.Signal(info.Signo) == linux.SIGBUS {
uc.MContext.FaultAddr = info.Addr()
}
ucSize := uc.SizeBytes()
// frameSize = ucSize + sizeof(siginfo).
// sizeof(siginfo) == 128.
// R30 stores the restorer address.
frameSize := ucSize + 128
frameBottom := (sp - hostarch.Addr(frameSize)) & ^hostarch.Addr(15)
sp = frameBottom + hostarch.Addr(frameSize)
st.Bottom = sp
// Prior to proceeding, figure out if the frame will exhaust the range
// for the signal stack. This is not allowed, and should immediately
// force signal delivery (reverting to the default handler).
if act.Flags&linux.SA_ONSTACK != 0 && alt.IsEnabled() && !alt.Contains(frameBottom) {
return unix.EFAULT
}
// Adjust the code.
info.FixSignalCodeForUser()
// Set up the stack frame.
if _, err := info.CopyOut(st, StackBottomMagic); err != nil {
return err
}
infoAddr := st.Bottom
if _, err := uc.CopyOut(st, StackBottomMagic); err != nil {
return err
}
ucAddr := st.Bottom
// Set up registers.
c.Regs.Sp = uint64(st.Bottom)
c.Regs.Pc = act.Handler
c.Regs.Regs[0] = uint64(info.Signo)
c.Regs.Regs[1] = uint64(infoAddr)
c.Regs.Regs[2] = uint64(ucAddr)
c.Regs.Regs[30] = act.Restorer
// Save the thread's floating point state.
c.sigFPState = append(c.sigFPState, c.fpState)
// Signal handler gets a clean floating point state.
c.fpState = fpu.NewState()
return nil
}
// SignalRestore implements Context.SignalRestore.
func (c *context64) SignalRestore(st *Stack, rt bool) (linux.SignalSet, linux.SignalStack, error) {
// Copy out the stack frame.
var uc UContext64
if _, err := uc.CopyIn(st, StackBottomMagic); err != nil {
return 0, linux.SignalStack{}, err
}
var info linux.SignalInfo
if _, err := info.CopyIn(st, StackBottomMagic); err != nil {
return 0, linux.SignalStack{}, err
}
// Restore registers.
c.Regs.Regs = uc.MContext.Regs
c.Regs.Pc = uc.MContext.Pc
c.Regs.Sp = uc.MContext.Sp
c.Regs.Pstate = uc.MContext.Pstate
// Restore floating point state.
l := len(c.sigFPState)
if l > 0 {
c.fpState = c.sigFPState[l-1]
// NOTE(cl/133042258): State save requires that any slice
// elements from '[len:cap]' to be zero value.
c.sigFPState[l-1] = nil
c.sigFPState = c.sigFPState[0 : l-1]
} else {
// This might happen if sigreturn(2) calls are unbalanced with
// respect to signal handler entries. This is not expected so
// don't bother to do anything fancy with the floating point
// state.
log.Warningf("sigreturn unable to restore application fpstate")
}
return uc.Sigset, uc.Stack, nil
}
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