144 lines
3.7 KiB
ArmAsm
144 lines
3.7 KiB
ArmAsm
// Copyright 2018 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include "textflag.h"
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// The signals handled by sigHandler.
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#define SIGBUS 7
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#define SIGSEGV 11
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// Offsets to the registers in context->uc_mcontext.gregs[].
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#define REG_R0 0xB8
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#define REG_R1 0xC0
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#define REG_PC 0x1B8
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// Offset to the si_addr field of siginfo.
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#define SI_CODE 0x08
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#define SI_ADDR 0x10
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// signalHandler is the signal handler for SIGSEGV and SIGBUS signals. It must
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// not be set up as a handler to any other signals.
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//
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// If the instruction causing the signal is within a safecopy-protected
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// function, the signal is handled such that execution resumes in the
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// appropriate fault handling stub with R0 containing the faulting address and
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// R1 containing the signal number. Otherwise control is transferred to the
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// previously configured signal handler (savedSigSegvHandler or
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// savedSigBusHandler).
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//
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// This function cannot be written in go because it runs whenever a signal is
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// received by the thread (preempting whatever was running), which includes when
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// garbage collector has stopped or isn't expecting any interactions (like
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// barriers).
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//
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// The arguments are the following:
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// R0 - The signal number.
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// R1 - Pointer to siginfo_t structure.
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// R2 - Pointer to ucontext structure.
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TEXT ·signalHandler(SB),NOSPLIT,$0
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// Check if the signal is from the kernel, si_code > 0 means a kernel signal.
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MOVD SI_CODE(R1), R7
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CMPW $0x0, R7
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BLE original_handler
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// Check if PC is within the area we care about.
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MOVD REG_PC(R2), R7
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MOVD ·memcpyBegin(SB), R8
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CMP R8, R7
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BLO not_memcpy
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MOVD ·memcpyEnd(SB), R8
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CMP R8, R7
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BHS not_memcpy
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// Modify the context such that execution will resume in the fault handler.
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MOVD $handleMemcpyFault(SB), R7
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B handle_fault
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not_memcpy:
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MOVD ·memclrBegin(SB), R8
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CMP R8, R7
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BLO not_memclr
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MOVD ·memclrEnd(SB), R8
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CMP R8, R7
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BHS not_memclr
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MOVD $handleMemclrFault(SB), R7
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B handle_fault
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not_memclr:
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MOVD ·swapUint32Begin(SB), R8
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CMP R8, R7
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BLO not_swapuint32
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MOVD ·swapUint32End(SB), R8
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CMP R8, R7
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BHS not_swapuint32
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MOVD $handleSwapUint32Fault(SB), R7
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B handle_fault
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not_swapuint32:
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MOVD ·swapUint64Begin(SB), R8
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CMP R8, R7
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BLO not_swapuint64
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MOVD ·swapUint64End(SB), R8
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CMP R8, R7
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BHS not_swapuint64
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MOVD $handleSwapUint64Fault(SB), R7
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B handle_fault
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not_swapuint64:
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MOVD ·compareAndSwapUint32Begin(SB), R8
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CMP R8, R7
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BLO not_casuint32
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MOVD ·compareAndSwapUint32End(SB), R8
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CMP R8, R7
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BHS not_casuint32
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MOVD $handleCompareAndSwapUint32Fault(SB), R7
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B handle_fault
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not_casuint32:
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MOVD ·loadUint32Begin(SB), R8
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CMP R8, R7
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BLO not_loaduint32
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MOVD ·loadUint32End(SB), R8
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CMP R8, R7
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BHS not_loaduint32
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MOVD $handleLoadUint32Fault(SB), R7
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B handle_fault
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not_loaduint32:
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original_handler:
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// Jump to the previous signal handler, which is likely the golang one.
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MOVD ·savedSigBusHandler(SB), R7
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MOVD ·savedSigSegVHandler(SB), R8
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CMPW $SIGSEGV, R0
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CSEL EQ, R8, R7, R7
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B (R7)
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handle_fault:
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// Entered with the address of the fault handler in R7; store it in PC.
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MOVD R7, REG_PC(R2)
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// Store the faulting address in R0.
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MOVD SI_ADDR(R1), R7
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MOVD R7, REG_R0(R2)
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// Store the signal number in R1.
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MOVW R0, REG_R1(R2)
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RET
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