From 0e2f1b7abd219f39d67cc2cecd00c441a13eeb29 Mon Sep 17 00:00:00 2001
From: Adin Scannell <ascannell@google.com>
Date: Mon, 27 Jan 2020 15:17:58 -0800
Subject: Update package locations.

Because the abi will depend on the core types for marshalling (usermem,
context, safemem, safecopy), these need to be flattened from the sentry
directory. These packages contain no sentry-specific details.

PiperOrigin-RevId: 291811289
---
 pkg/safecopy/sighandler_arm64.s | 143 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 143 insertions(+)
 create mode 100644 pkg/safecopy/sighandler_arm64.s

(limited to 'pkg/safecopy/sighandler_arm64.s')

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
-- 
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