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// Copyright 2018 Google LLC
//
// 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 "funcdata.h"
#include "textflag.h"
// NB: Offsets are programatically generated (see BUILD).
//
// This file is concatenated with the definitions.
// Saves a register set.
//
// This is a macro because it may need to executed in contents where a stack is
// not available for calls.
//
// The following registers are not saved: AX, SP, IP, FLAGS, all segments.
#define REGISTERS_SAVE(reg, offset) \
MOVQ R15, offset+PTRACE_R15(reg); \
MOVQ R14, offset+PTRACE_R14(reg); \
MOVQ R13, offset+PTRACE_R13(reg); \
MOVQ R12, offset+PTRACE_R12(reg); \
MOVQ BP, offset+PTRACE_RBP(reg); \
MOVQ BX, offset+PTRACE_RBX(reg); \
MOVQ CX, offset+PTRACE_RCX(reg); \
MOVQ DX, offset+PTRACE_RDX(reg); \
MOVQ R11, offset+PTRACE_R11(reg); \
MOVQ R10, offset+PTRACE_R10(reg); \
MOVQ R9, offset+PTRACE_R9(reg); \
MOVQ R8, offset+PTRACE_R8(reg); \
MOVQ SI, offset+PTRACE_RSI(reg); \
MOVQ DI, offset+PTRACE_RDI(reg);
// Loads a register set.
//
// This is a macro because it may need to executed in contents where a stack is
// not available for calls.
//
// The following registers are not loaded: AX, SP, IP, FLAGS, all segments.
#define REGISTERS_LOAD(reg, offset) \
MOVQ offset+PTRACE_R15(reg), R15; \
MOVQ offset+PTRACE_R14(reg), R14; \
MOVQ offset+PTRACE_R13(reg), R13; \
MOVQ offset+PTRACE_R12(reg), R12; \
MOVQ offset+PTRACE_RBP(reg), BP; \
MOVQ offset+PTRACE_RBX(reg), BX; \
MOVQ offset+PTRACE_RCX(reg), CX; \
MOVQ offset+PTRACE_RDX(reg), DX; \
MOVQ offset+PTRACE_R11(reg), R11; \
MOVQ offset+PTRACE_R10(reg), R10; \
MOVQ offset+PTRACE_R9(reg), R9; \
MOVQ offset+PTRACE_R8(reg), R8; \
MOVQ offset+PTRACE_RSI(reg), SI; \
MOVQ offset+PTRACE_RDI(reg), DI;
// SWAP_GS swaps the kernel GS (CPU).
#define SWAP_GS() \
BYTE $0x0F; BYTE $0x01; BYTE $0xf8;
// IRET returns from an interrupt frame.
#define IRET() \
BYTE $0x48; BYTE $0xcf;
// SYSRET64 executes the sysret instruction.
#define SYSRET64() \
BYTE $0x48; BYTE $0x0f; BYTE $0x07;
// LOAD_KERNEL_ADDRESS loads a kernel address.
#define LOAD_KERNEL_ADDRESS(from, to) \
MOVQ from, to; \
ORQ ·KernelStartAddress(SB), to;
// LOAD_KERNEL_STACK loads the kernel stack.
#define LOAD_KERNEL_STACK(from) \
LOAD_KERNEL_ADDRESS(CPU_SELF(from), SP); \
LEAQ CPU_STACK_TOP(SP), SP;
// See kernel.go.
TEXT ·Halt(SB),NOSPLIT,$0
HLT
RET
// See entry_amd64.go.
TEXT ·swapgs(SB),NOSPLIT,$0
SWAP_GS()
RET
// See entry_amd64.go.
TEXT ·sysret(SB),NOSPLIT,$0-24
// Save original state.
LOAD_KERNEL_ADDRESS(cpu+0(FP), BX)
LOAD_KERNEL_ADDRESS(regs+8(FP), AX)
MOVQ SP, CPU_REGISTERS+PTRACE_RSP(BX)
MOVQ BP, CPU_REGISTERS+PTRACE_RBP(BX)
MOVQ AX, CPU_REGISTERS+PTRACE_RAX(BX)
// Restore user register state.
REGISTERS_LOAD(AX, 0)
MOVQ PTRACE_RIP(AX), CX // Needed for SYSRET.
MOVQ PTRACE_FLAGS(AX), R11 // Needed for SYSRET.
MOVQ PTRACE_RSP(AX), SP // Restore the stack directly.
MOVQ PTRACE_RAX(AX), AX // Restore AX (scratch).
SYSRET64()
// See entry_amd64.go.
TEXT ·iret(SB),NOSPLIT,$0-24
// Save original state.
LOAD_KERNEL_ADDRESS(cpu+0(FP), BX)
LOAD_KERNEL_ADDRESS(regs+8(FP), AX)
MOVQ SP, CPU_REGISTERS+PTRACE_RSP(BX)
MOVQ BP, CPU_REGISTERS+PTRACE_RBP(BX)
MOVQ AX, CPU_REGISTERS+PTRACE_RAX(BX)
// Build an IRET frame & restore state.
LOAD_KERNEL_STACK(BX)
MOVQ PTRACE_SS(AX), BX; PUSHQ BX
MOVQ PTRACE_RSP(AX), CX; PUSHQ CX
MOVQ PTRACE_FLAGS(AX), DX; PUSHQ DX
MOVQ PTRACE_CS(AX), DI; PUSHQ DI
MOVQ PTRACE_RIP(AX), SI; PUSHQ SI
REGISTERS_LOAD(AX, 0) // Restore most registers.
MOVQ PTRACE_RAX(AX), AX // Restore AX (scratch).
IRET()
// See entry_amd64.go.
TEXT ·resume(SB),NOSPLIT,$0
// See iret, above.
MOVQ CPU_REGISTERS+PTRACE_SS(GS), BX; PUSHQ BX
MOVQ CPU_REGISTERS+PTRACE_RSP(GS), CX; PUSHQ CX
MOVQ CPU_REGISTERS+PTRACE_FLAGS(GS), DX; PUSHQ DX
MOVQ CPU_REGISTERS+PTRACE_CS(GS), DI; PUSHQ DI
MOVQ CPU_REGISTERS+PTRACE_RIP(GS), SI; PUSHQ SI
REGISTERS_LOAD(GS, CPU_REGISTERS)
MOVQ CPU_REGISTERS+PTRACE_RAX(GS), AX
IRET()
// See entry_amd64.go.
TEXT ·Start(SB),NOSPLIT,$0
LOAD_KERNEL_STACK(AX) // Set the stack.
PUSHQ $0x0 // Previous frame pointer.
MOVQ SP, BP // Set frame pointer.
PUSHQ AX // First argument (CPU).
CALL ·start(SB) // Call Go hook.
JMP ·resume(SB) // Restore to registers.
// See entry_amd64.go.
TEXT ·sysenter(SB),NOSPLIT,$0
// Interrupts are always disabled while we're executing in kernel mode
// and always enabled while executing in user mode. Therefore, we can
// reliably look at the flags in R11 to determine where this syscall
// was from.
TESTL $_RFLAGS_IF, R11
JZ kernel
user:
SWAP_GS()
XCHGQ CPU_REGISTERS+PTRACE_RSP(GS), SP // Swap stacks.
XCHGQ CPU_REGISTERS+PTRACE_RAX(GS), AX // Swap for AX (regs).
REGISTERS_SAVE(AX, 0) // Save all except IP, FLAGS, SP, AX.
MOVQ CPU_REGISTERS+PTRACE_RAX(GS), BX // Load saved AX value.
MOVQ BX, PTRACE_RAX(AX) // Save everything else.
MOVQ BX, PTRACE_ORIGRAX(AX)
MOVQ CX, PTRACE_RIP(AX)
MOVQ R11, PTRACE_FLAGS(AX)
MOVQ CPU_REGISTERS+PTRACE_RSP(GS), BX; MOVQ BX, PTRACE_RSP(AX)
MOVQ $0, CPU_ERROR_CODE(GS) // Clear error code.
MOVQ $1, CPU_ERROR_TYPE(GS) // Set error type to user.
// Return to the kernel, where the frame is:
//
// vector (sp+24)
// regs (sp+16)
// cpu (sp+8)
// vcpu.Switch (sp+0)
//
MOVQ CPU_REGISTERS+PTRACE_RBP(GS), BP // Original base pointer.
MOVQ $Syscall, 24(SP) // Output vector.
RET
kernel:
// We can't restore the original stack, but we can access the registers
// in the CPU state directly. No need for temporary juggling.
MOVQ AX, CPU_REGISTERS+PTRACE_ORIGRAX(GS)
MOVQ AX, CPU_REGISTERS+PTRACE_RAX(GS)
REGISTERS_SAVE(GS, CPU_REGISTERS)
MOVQ CX, CPU_REGISTERS+PTRACE_RIP(GS)
MOVQ R11, CPU_REGISTERS+PTRACE_FLAGS(GS)
MOVQ SP, CPU_REGISTERS+PTRACE_RSP(GS)
MOVQ $0, CPU_ERROR_CODE(GS) // Clear error code.
MOVQ $0, CPU_ERROR_TYPE(GS) // Set error type to kernel.
// Call the syscall trampoline.
LOAD_KERNEL_STACK(GS)
MOVQ CPU_SELF(GS), AX // Load vCPU.
PUSHQ AX // First argument (vCPU).
CALL ·kernelSyscall(SB) // Call the trampoline.
POPQ AX // Pop vCPU.
JMP ·resume(SB)
// exception is a generic exception handler.
//
// There are two cases handled:
//
// 1) An exception in kernel mode: this results in saving the state at the time
// of the exception and calling the defined hook.
//
// 2) An exception in guest mode: the original kernel frame is restored, and
// the vector & error codes are pushed as return values.
//
// See below for the stubs that call exception.
TEXT ·exception(SB),NOSPLIT,$0
// Determine whether the exception occurred in kernel mode or user
// mode, based on the flags. We expect the following stack:
//
// SS (sp+48)
// SP (sp+40)
// FLAGS (sp+32)
// CS (sp+24)
// IP (sp+16)
// ERROR_CODE (sp+8)
// VECTOR (sp+0)
//
TESTL $_RFLAGS_IF, 32(SP)
JZ kernel
user:
SWAP_GS()
ADDQ $-8, SP // Adjust for flags.
MOVQ $_KERNEL_FLAGS, 0(SP); BYTE $0x9d; // Reset flags (POPFQ).
XCHGQ CPU_REGISTERS+PTRACE_RAX(GS), AX // Swap for user regs.
REGISTERS_SAVE(AX, 0) // Save all except IP, FLAGS, SP, AX.
MOVQ CPU_REGISTERS+PTRACE_RAX(GS), BX // Restore original AX.
MOVQ BX, PTRACE_RAX(AX) // Save it.
MOVQ BX, PTRACE_ORIGRAX(AX)
MOVQ 16(SP), BX; MOVQ BX, PTRACE_RIP(AX)
MOVQ 24(SP), CX; MOVQ CX, PTRACE_CS(AX)
MOVQ 32(SP), DX; MOVQ DX, PTRACE_FLAGS(AX)
MOVQ 40(SP), DI; MOVQ DI, PTRACE_RSP(AX)
MOVQ 48(SP), SI; MOVQ SI, PTRACE_SS(AX)
// Copy out and return.
MOVQ 0(SP), BX // Load vector.
MOVQ 8(SP), CX // Load error code.
MOVQ CPU_REGISTERS+PTRACE_RSP(GS), SP // Original stack (kernel version).
MOVQ CPU_REGISTERS+PTRACE_RBP(GS), BP // Original base pointer.
MOVQ CX, CPU_ERROR_CODE(GS) // Set error code.
MOVQ $1, CPU_ERROR_TYPE(GS) // Set error type to user.
MOVQ BX, 24(SP) // Output vector.
RET
kernel:
// As per above, we can save directly.
MOVQ AX, CPU_REGISTERS+PTRACE_RAX(GS)
MOVQ AX, CPU_REGISTERS+PTRACE_ORIGRAX(GS)
REGISTERS_SAVE(GS, CPU_REGISTERS)
MOVQ 16(SP), AX; MOVQ AX, CPU_REGISTERS+PTRACE_RIP(GS)
MOVQ 32(SP), BX; MOVQ BX, CPU_REGISTERS+PTRACE_FLAGS(GS)
MOVQ 40(SP), CX; MOVQ CX, CPU_REGISTERS+PTRACE_RSP(GS)
// Set the error code and adjust the stack.
MOVQ 8(SP), AX // Load the error code.
MOVQ AX, CPU_ERROR_CODE(GS) // Copy out to the CPU.
MOVQ $0, CPU_ERROR_TYPE(GS) // Set error type to kernel.
MOVQ 0(SP), BX // BX contains the vector.
ADDQ $48, SP // Drop the exception frame.
// Call the exception trampoline.
LOAD_KERNEL_STACK(GS)
MOVQ CPU_SELF(GS), AX // Load vCPU.
PUSHQ BX // Second argument (vector).
PUSHQ AX // First argument (vCPU).
CALL ·kernelException(SB) // Call the trampoline.
POPQ BX // Pop vector.
POPQ AX // Pop vCPU.
JMP ·resume(SB)
#define EXCEPTION_WITH_ERROR(value, symbol) \
TEXT symbol,NOSPLIT,$0; \
PUSHQ $value; \
JMP ·exception(SB);
#define EXCEPTION_WITHOUT_ERROR(value, symbol) \
TEXT symbol,NOSPLIT,$0; \
PUSHQ $0x0; \
PUSHQ $value; \
JMP ·exception(SB);
EXCEPTION_WITHOUT_ERROR(DivideByZero, ·divideByZero(SB))
EXCEPTION_WITHOUT_ERROR(Debug, ·debug(SB))
EXCEPTION_WITHOUT_ERROR(NMI, ·nmi(SB))
EXCEPTION_WITHOUT_ERROR(Breakpoint, ·breakpoint(SB))
EXCEPTION_WITHOUT_ERROR(Overflow, ·overflow(SB))
EXCEPTION_WITHOUT_ERROR(BoundRangeExceeded, ·boundRangeExceeded(SB))
EXCEPTION_WITHOUT_ERROR(InvalidOpcode, ·invalidOpcode(SB))
EXCEPTION_WITHOUT_ERROR(DeviceNotAvailable, ·deviceNotAvailable(SB))
EXCEPTION_WITH_ERROR(DoubleFault, ·doubleFault(SB))
EXCEPTION_WITHOUT_ERROR(CoprocessorSegmentOverrun, ·coprocessorSegmentOverrun(SB))
EXCEPTION_WITH_ERROR(InvalidTSS, ·invalidTSS(SB))
EXCEPTION_WITH_ERROR(SegmentNotPresent, ·segmentNotPresent(SB))
EXCEPTION_WITH_ERROR(StackSegmentFault, ·stackSegmentFault(SB))
EXCEPTION_WITH_ERROR(GeneralProtectionFault, ·generalProtectionFault(SB))
EXCEPTION_WITH_ERROR(PageFault, ·pageFault(SB))
EXCEPTION_WITHOUT_ERROR(X87FloatingPointException, ·x87FloatingPointException(SB))
EXCEPTION_WITH_ERROR(AlignmentCheck, ·alignmentCheck(SB))
EXCEPTION_WITHOUT_ERROR(MachineCheck, ·machineCheck(SB))
EXCEPTION_WITHOUT_ERROR(SIMDFloatingPointException, ·simdFloatingPointException(SB))
EXCEPTION_WITHOUT_ERROR(VirtualizationException, ·virtualizationException(SB))
EXCEPTION_WITH_ERROR(SecurityException, ·securityException(SB))
EXCEPTION_WITHOUT_ERROR(SyscallInt80, ·syscallInt80(SB))
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