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authorkevin.xu <cming.xu@gmail.com>2020-04-27 21:51:31 +0800
committerGitHub <noreply@github.com>2020-04-27 21:51:31 +0800
commite896ca54db67524afc20b644d43c72185e72dc0e (patch)
tree2a16f3a62a5cafd098f1f028c621f1b655589d69 /pkg/safecopy/sighandler_arm64.s
parent1f19624fa127d7d59cabe29593cc80b7fe6c81f8 (diff)
parent3c67754663f424f2ebbc0ff2a4c80e30618d5355 (diff)
Merge pull request #1 from google/master
catch up
Diffstat (limited to 'pkg/safecopy/sighandler_arm64.s')
-rw-r--r--pkg/safecopy/sighandler_arm64.s143
1 files changed, 143 insertions, 0 deletions
diff --git a/pkg/safecopy/sighandler_arm64.s b/pkg/safecopy/sighandler_arm64.s
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index 000000000..53e4ac2c1
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+++ b/pkg/safecopy/sighandler_arm64.s
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+// 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