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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.
package arch
import (
"encoding/binary"
"syscall"
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/sentry/usermem"
)
// SignalContext64 is equivalent to struct sigcontext, the type passed as the
// second argument to signal handlers set by signal(2).
type SignalContext64 struct {
FaultAddr uint64
Regs [31]uint64
Sp uint64
Pc uint64
Pstate uint64
_pad [8]byte // __attribute__((__aligned__(16)))
Reserved [4096]uint8
}
// UContext64 is equivalent to ucontext on arm64(arch/arm64/include/uapi/asm/ucontext.h).
type UContext64 struct {
Flags uint64
Link *UContext64
Stack SignalStack
Sigset linux.SignalSet
// glibc uses a 1024-bit sigset_t
_pad [(1024 - 64) / 8]byte
// sigcontext must be aligned to 16-byte
_pad2 [8]byte
// last for future expansion
MContext SignalContext64
}
// NewSignalAct implements Context.NewSignalAct.
func (c *context64) NewSignalAct() NativeSignalAct {
return &SignalAct{}
}
// NewSignalStack implements Context.NewSignalStack.
func (c *context64) NewSignalStack() NativeSignalStack {
return &SignalStack{}
}
// SignalSetup implements Context.SignalSetup.
func (c *context64) SignalSetup(st *Stack, act *SignalAct, info *SignalInfo, alt *SignalStack, sigset linux.SignalSet) error {
sp := st.Bottom
if !(alt.IsEnabled() && sp == alt.Top()) {
sp -= 128
}
// 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,
}
ucSize := binary.Size(uc)
if ucSize < 0 {
panic("can't get size of UContext64")
}
// st.Arch.Width() is for the restorer address. sizeof(siginfo) == 128.
frameSize := int(st.Arch.Width()) + ucSize + 128
frameBottom := (sp-usermem.Addr(frameSize)) & ^usermem.Addr(15) - 8
sp = frameBottom + usermem.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.IsOnStack() && alt.IsEnabled() && !alt.Contains(frameBottom) {
return syscall.EFAULT
}
// Adjust the code.
info.FixSignalCodeForUser()
// Set up the stack frame.
infoAddr, err := st.Push(info)
if err != nil {
return err
}
ucAddr, err := st.Push(uc)
if err != nil {
return err
}
// 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)
return nil
}
// SignalRestore implements Context.SignalRestore.
// Only used on intel.
func (c *context64) SignalRestore(st *Stack, rt bool) (linux.SignalSet, SignalStack, error) {
return 0, SignalStack{}, nil
}
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