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Diffstat (limited to 'pkg/safecopy/sighandler_amd64.s')
| -rw-r--r-- | pkg/safecopy/sighandler_amd64.s | 133 |
1 files changed, 133 insertions, 0 deletions
diff --git a/pkg/safecopy/sighandler_amd64.s b/pkg/safecopy/sighandler_amd64.s new file mode 100644 index 000000000..475ae48e9 --- /dev/null +++ b/pkg/safecopy/sighandler_amd64.s @@ -0,0 +1,133 @@ +// 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_RDI 0x68 +#define REG_RAX 0x90 +#define REG_IP 0xa8 + +// 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 AX containing the faulting address and +// DI 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: +// DI - The signal number. +// SI - Pointer to siginfo_t structure. +// DX - Pointer to ucontext structure. +TEXT ·signalHandler(SB),NOSPLIT,$0 + // Check if the signal is from the kernel. + MOVQ $0x0, CX + CMPL CX, SI_CODE(SI) + JGE original_handler + + // Check if RIP is within the area we care about. + MOVQ REG_IP(DX), CX + CMPQ CX, ·memcpyBegin(SB) + JB not_memcpy + CMPQ CX, ·memcpyEnd(SB) + JAE not_memcpy + + // Modify the context such that execution will resume in the fault + // handler. + LEAQ handleMemcpyFault(SB), CX + JMP handle_fault + +not_memcpy: + CMPQ CX, ·memclrBegin(SB) + JB not_memclr + CMPQ CX, ·memclrEnd(SB) + JAE not_memclr + + LEAQ handleMemclrFault(SB), CX + JMP handle_fault + +not_memclr: + CMPQ CX, ·swapUint32Begin(SB) + JB not_swapuint32 + CMPQ CX, ·swapUint32End(SB) + JAE not_swapuint32 + + LEAQ handleSwapUint32Fault(SB), CX + JMP handle_fault + +not_swapuint32: + CMPQ CX, ·swapUint64Begin(SB) + JB not_swapuint64 + CMPQ CX, ·swapUint64End(SB) + JAE not_swapuint64 + + LEAQ handleSwapUint64Fault(SB), CX + JMP handle_fault + +not_swapuint64: + CMPQ CX, ·compareAndSwapUint32Begin(SB) + JB not_casuint32 + CMPQ CX, ·compareAndSwapUint32End(SB) + JAE not_casuint32 + + LEAQ handleCompareAndSwapUint32Fault(SB), CX + JMP handle_fault + +not_casuint32: + CMPQ CX, ·loadUint32Begin(SB) + JB not_loaduint32 + CMPQ CX, ·loadUint32End(SB) + JAE not_loaduint32 + + LEAQ handleLoadUint32Fault(SB), CX + JMP handle_fault + +not_loaduint32: +original_handler: + // Jump to the previous signal handler, which is likely the golang one. + XORQ CX, CX + MOVQ ·savedSigBusHandler(SB), AX + CMPL DI, $SIGSEGV + CMOVQEQ ·savedSigSegVHandler(SB), AX + JMP AX + +handle_fault: + // Entered with the address of the fault handler in RCX; store it in + // RIP. + MOVQ CX, REG_IP(DX) + + // Store the faulting address in RAX. + MOVQ SI_ADDR(SI), CX + MOVQ CX, REG_RAX(DX) + + // Store the signal number in EDI. + MOVL DI, REG_RDI(DX) + + RET |