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// Copyright 2019 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"
// VCPU_CPU is the location of the CPU in the vCPU struct.
//
// This is guaranteed to be zero.
#define VCPU_CPU 0x0
// CPU_SELF is the self reference in ring0's percpu.
//
// This is guaranteed to be zero.
#define CPU_SELF 0x0
// Context offsets.
//
// Only limited use of the context is done in the assembly stub below, most is
// done in the Go handlers.
#define SIGINFO_SIGNO 0x0
#define SIGINFO_CODE 0x8
#define CONTEXT_PC 0x1B8
#define CONTEXT_R0 0xB8
#define SYS_MMAP 222
// getTLS returns the value of TPIDR_EL0 register.
TEXT ·getTLS(SB),NOSPLIT,$0-8
MRS TPIDR_EL0, R1
MOVD R1, ret+0(FP)
RET
// setTLS writes the TPIDR_EL0 value.
TEXT ·setTLS(SB),NOSPLIT,$0-8
MOVD addr+0(FP), R1
MSR R1, TPIDR_EL0
RET
// See bluepill.go.
TEXT ·bluepill(SB),NOSPLIT,$0
begin:
MOVD vcpu+0(FP), R8
MOVD $VCPU_CPU(R8), R9
ORR $0xffff000000000000, R9, R9
// Trigger sigill.
// In ring0.Start(), the value of R8 will be stored into tpidr_el1.
// When the context was loaded into vcpu successfully,
// we will check if the value of R10 and R9 are the same.
WORD $0xd538d08a // MRS TPIDR_EL1, R10
check_vcpu:
CMP R10, R9
BEQ right_vCPU
wrong_vcpu:
CALL ·redpill(SB)
B begin
right_vCPU:
RET
// sighandler: see bluepill.go for documentation.
//
// The arguments are the following:
//
// R0 - The signal number.
// R1 - Pointer to siginfo_t structure.
// R2 - Pointer to ucontext structure.
//
TEXT ·sighandler(SB),NOSPLIT,$0
// si_signo should be sigill.
MOVD SIGINFO_SIGNO(R1), R7
CMPW $4, R7
BNE fallback
MOVD CONTEXT_PC(R2), R7
CMPW $0, R7
BEQ fallback
MOVD R2, 8(RSP)
BL ·bluepillHandler(SB) // Call the handler.
RET
fallback:
// Jump to the previous signal handler.
MOVD ·savedHandler(SB), R7
B (R7)
// func addrOfSighandler() uintptr
TEXT ·addrOfSighandler(SB), $0-8
MOVD $·sighandler(SB), R0
MOVD R0, ret+0(FP)
RET
// The arguments are the following:
//
// R0 - The signal number.
// R1 - Pointer to siginfo_t structure.
// R2 - Pointer to ucontext structure.
//
TEXT ·sigsysHandler(SB),NOSPLIT,$0
// si_code should be SYS_SECCOMP.
MOVD SIGINFO_CODE(R1), R7
CMPW $1, R7
BNE fallback
CMPW $SYS_MMAP, R8
BNE fallback
MOVD R2, 8(RSP)
BL ·seccompMmapHandler(SB) // Call the handler.
RET
fallback:
// Jump to the previous signal handler.
MOVD ·savedHandler(SB), R7
B (R7)
// func addrOfSighandler() uintptr
TEXT ·addrOfSigsysHandler(SB), $0-8
MOVD $·sigsysHandler(SB), R0
MOVD R0, ret+0(FP)
RET
// dieTrampoline: see bluepill.go, bluepill_arm64_unsafe.go for documentation.
TEXT ·dieTrampoline(SB),NOSPLIT,$0
// R0: Fake the old PC as caller
// R1: First argument (vCPU)
MOVD.P R1, 8(RSP) // R1: First argument (vCPU)
MOVD.P R0, 8(RSP) // R0: Fake the old PC as caller
B ·dieHandler(SB)
// func addrOfDieTrampoline() uintptr
TEXT ·addrOfDieTrampoline(SB), $0-8
MOVD $·dieTrampoline(SB), R0
MOVD R0, ret+0(FP)
RET
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