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Diffstat (limited to 'pkg/safecopy/sighandler_arm64.s')
| -rw-r--r-- | pkg/safecopy/sighandler_arm64.s | 143 |
1 files changed, 143 insertions, 0 deletions
diff --git a/pkg/safecopy/sighandler_arm64.s b/pkg/safecopy/sighandler_arm64.s new file mode 100644 index 000000000..53e4ac2c1 --- /dev/null +++ b/pkg/safecopy/sighandler_arm64.s @@ -0,0 +1,143 @@ +// Copyright 2018 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" + +// The signals handled by sigHandler. +#define SIGBUS 7 +#define SIGSEGV 11 + +// Offsets to the registers in context->uc_mcontext.gregs[]. +#define REG_R0 0xB8 +#define REG_R1 0xC0 +#define REG_PC 0x1B8 + +// Offset to the si_addr field of siginfo. +#define SI_CODE 0x08 +#define SI_ADDR 0x10 + +// signalHandler is the signal handler for SIGSEGV and SIGBUS signals. It must +// not be set up as a handler to any other signals. +// +// If the instruction causing the signal is within a safecopy-protected +// function, the signal is handled such that execution resumes in the +// appropriate fault handling stub with R0 containing the faulting address and +// R1 containing the signal number. Otherwise control is transferred to the +// previously configured signal handler (savedSigSegvHandler or +// savedSigBusHandler). +// +// This function cannot be written in go because it runs whenever a signal is +// received by the thread (preempting whatever was running), which includes when +// garbage collector has stopped or isn't expecting any interactions (like +// barriers). +// +// The arguments are the following: +// R0 - The signal number. +// R1 - Pointer to siginfo_t structure. +// R2 - Pointer to ucontext structure. +TEXT ·signalHandler(SB),NOSPLIT,$0 + // Check if the signal is from the kernel, si_code > 0 means a kernel signal. + MOVD SI_CODE(R1), R7 + CMPW $0x0, R7 + BLE original_handler + + // Check if PC is within the area we care about. + MOVD REG_PC(R2), R7 + MOVD ·memcpyBegin(SB), R8 + CMP R8, R7 + BLO not_memcpy + MOVD ·memcpyEnd(SB), R8 + CMP R8, R7 + BHS not_memcpy + + // Modify the context such that execution will resume in the fault handler. + MOVD $handleMemcpyFault(SB), R7 + B handle_fault + +not_memcpy: + MOVD ·memclrBegin(SB), R8 + CMP R8, R7 + BLO not_memclr + MOVD ·memclrEnd(SB), R8 + CMP R8, R7 + BHS not_memclr + + MOVD $handleMemclrFault(SB), R7 + B handle_fault + +not_memclr: + MOVD ·swapUint32Begin(SB), R8 + CMP R8, R7 + BLO not_swapuint32 + MOVD ·swapUint32End(SB), R8 + CMP R8, R7 + BHS not_swapuint32 + + MOVD $handleSwapUint32Fault(SB), R7 + B handle_fault + +not_swapuint32: + MOVD ·swapUint64Begin(SB), R8 + CMP R8, R7 + BLO not_swapuint64 + MOVD ·swapUint64End(SB), R8 + CMP R8, R7 + BHS not_swapuint64 + + MOVD $handleSwapUint64Fault(SB), R7 + B handle_fault + +not_swapuint64: + MOVD ·compareAndSwapUint32Begin(SB), R8 + CMP R8, R7 + BLO not_casuint32 + MOVD ·compareAndSwapUint32End(SB), R8 + CMP R8, R7 + BHS not_casuint32 + + MOVD $handleCompareAndSwapUint32Fault(SB), R7 + B handle_fault + +not_casuint32: + MOVD ·loadUint32Begin(SB), R8 + CMP R8, R7 + BLO not_loaduint32 + MOVD ·loadUint32End(SB), R8 + CMP R8, R7 + BHS not_loaduint32 + + MOVD $handleLoadUint32Fault(SB), R7 + B handle_fault + +not_loaduint32: +original_handler: + // Jump to the previous signal handler, which is likely the golang one. + MOVD ·savedSigBusHandler(SB), R7 + MOVD ·savedSigSegVHandler(SB), R8 + CMPW $SIGSEGV, R0 + CSEL EQ, R8, R7, R7 + B (R7) + +handle_fault: + // Entered with the address of the fault handler in R7; store it in PC. + MOVD R7, REG_PC(R2) + + // Store the faulting address in R0. + MOVD SI_ADDR(R1), R7 + MOVD R7, REG_R0(R2) + + // Store the signal number in R1. + MOVW R0, REG_R1(R2) + + RET |