From ab54d4f496dc59721066e295e162b3be903795d5 Mon Sep 17 00:00:00 2001
From: Bin Lu <bin.lu@arm.com>
Date: Thu, 2 Apr 2020 01:04:58 -0400
Subject: remove nogo exemption for machine_arm64_unsafe.go

Minimize the use of unsafe.

Signed-off-by: Bin Lu <bin.lu@arm.com>
---
 pkg/sentry/platform/kvm/kvm_arm64.go            |  4 +-
 pkg/sentry/platform/kvm/machine_arm64_unsafe.go | 63 -------------------------
 2 files changed, 3 insertions(+), 64 deletions(-)

(limited to 'pkg/sentry/platform/kvm')

diff --git a/pkg/sentry/platform/kvm/kvm_arm64.go b/pkg/sentry/platform/kvm/kvm_arm64.go
index 79045651e..716198712 100644
--- a/pkg/sentry/platform/kvm/kvm_arm64.go
+++ b/pkg/sentry/platform/kvm/kvm_arm64.go
@@ -18,6 +18,8 @@ package kvm
 
 import (
 	"syscall"
+
+	"gvisor.dev/gvisor/pkg/sentry/platform/ring0"
 )
 
 type kvmOneReg struct {
@@ -46,6 +48,6 @@ type userRegs struct {
 func updateGlobalOnce(fd int) error {
 	physicalInit()
 	err := updateSystemValues(int(fd))
-	updateVectorTable()
+	ring0.Init()
 	return err
 }
diff --git a/pkg/sentry/platform/kvm/machine_arm64_unsafe.go b/pkg/sentry/platform/kvm/machine_arm64_unsafe.go
index b531f2f85..3b35858ae 100644
--- a/pkg/sentry/platform/kvm/machine_arm64_unsafe.go
+++ b/pkg/sentry/platform/kvm/machine_arm64_unsafe.go
@@ -48,69 +48,6 @@ func (m *machine) initArchState() error {
 	return nil
 }
 
-func getPageWithReflect(p uintptr) []byte {
-	return (*(*[0xFFFFFF]byte)(unsafe.Pointer(p & ^uintptr(syscall.Getpagesize()-1))))[:syscall.Getpagesize()]
-}
-
-// Work around: move ring0.Vectors() into a specific address with 11-bits alignment.
-//
-// According to the design documentation of Arm64,
-// the start address of exception vector table should be 11-bits aligned.
-// Please see the code in linux kernel as reference: arch/arm64/kernel/entry.S
-// But, we can't align a function's start address to a specific address by using golang.
-// We have raised this question in golang community:
-// https://groups.google.com/forum/m/#!topic/golang-dev/RPj90l5x86I
-// This function will be removed when golang supports this feature.
-//
-// There are 2 jobs were implemented in this function:
-// 1, move the start address of exception vector table into the specific address.
-// 2, modify the offset of each instruction.
-func updateVectorTable() {
-	fromLocation := reflect.ValueOf(ring0.Vectors).Pointer()
-	offset := fromLocation & (1<<11 - 1)
-	if offset != 0 {
-		offset = 1<<11 - offset
-	}
-
-	toLocation := fromLocation + offset
-	page := getPageWithReflect(toLocation)
-	if err := syscall.Mprotect(page, syscall.PROT_READ|syscall.PROT_WRITE|syscall.PROT_EXEC); err != nil {
-		panic(err)
-	}
-
-	page = getPageWithReflect(toLocation + 4096)
-	if err := syscall.Mprotect(page, syscall.PROT_READ|syscall.PROT_WRITE|syscall.PROT_EXEC); err != nil {
-		panic(err)
-	}
-
-	// Move exception-vector-table into the specific address.
-	var entry *uint32
-	var entryFrom *uint32
-	for i := 1; i <= 0x800; i++ {
-		entry = (*uint32)(unsafe.Pointer(toLocation + 0x800 - uintptr(i)))
-		entryFrom = (*uint32)(unsafe.Pointer(fromLocation + 0x800 - uintptr(i)))
-		*entry = *entryFrom
-	}
-
-	// The offset from the address of each unconditionally branch is changed.
-	// We should modify the offset of each instruction.
-	nums := []uint32{0x0, 0x80, 0x100, 0x180, 0x200, 0x280, 0x300, 0x380, 0x400, 0x480, 0x500, 0x580, 0x600, 0x680, 0x700, 0x780}
-	for _, num := range nums {
-		entry = (*uint32)(unsafe.Pointer(toLocation + uintptr(num)))
-		*entry = *entry - (uint32)(offset/4)
-	}
-
-	page = getPageWithReflect(toLocation)
-	if err := syscall.Mprotect(page, syscall.PROT_READ|syscall.PROT_EXEC); err != nil {
-		panic(err)
-	}
-
-	page = getPageWithReflect(toLocation + 4096)
-	if err := syscall.Mprotect(page, syscall.PROT_READ|syscall.PROT_EXEC); err != nil {
-		panic(err)
-	}
-}
-
 // initArchState initializes architecture-specific state.
 func (c *vCPU) initArchState() error {
 	var (
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