- A
secret
byte you want to read is stored at inaccessible memory locationpriv_mem
. - The sender triggers an access exception by attempting to read
priv_mem
. - Due to CPU optimization (out-of-order execution), the load of
secret
frompriv_mem
and the use of its value in (4) and (5) below may execute before the exception is triggered. - Calculate an
offset
into a known arrayprobe
by multiplyingsecret
by the width of a cache line (or whatever block size the CPU typically fetches, like a 4096-byte page). This guarantees each of those 256 possible offsets will cache separately. - Load
probe[offset]
, which causes the CPU to cache exactly one chunk of of our array, populating one cache line. - The exception finally triggers, clearing the modified registers...but cached data is not excised.
- Iterate over all 256 offsets into
probe
to find out which one loads fast. You've determined the value ofsecret
.
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// | |
// ContentView.swift | |
// | |
// Created by Chris Eidhof on 20.04.20. | |
// Copyright © 2020 objc.io. All rights reserved. | |
// | |
import SwiftUI | |
import UIKit |
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// How to: | |
// 1. Open the Firebase Analytics Dashboard | |
// 2. Scroll to bottom, where you see the "Users by Device model" widget | |
// 3. Click "View device models" in that widget (this opens the "Tech details" Firebase Analytics page) | |
// 4. Above the table shown in the new page, click on the “Device model” drop down menu and select “OS with Version” | |
// 5. Make sure to select “OS with version” and not “OS Version” | |
// 6. On the top right corner of the page, click on the “Share this report” icon (next to the date) | |
// 7. Click “Download file” on the new side bar, then “Download CSV" | |
// 8. Open the file and select the iOS/Android breakdown raw data | |
// 9. Replace the sample data in this script with your data |
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// Advanced SwiftUI Transitions | |
// https://swiftui-lab.com | |
// https://swiftui-lab.com/advanced-transitions | |
import SwiftUI | |
struct GeometryEffectTransitionsDemo: View { | |
@State private var show = false | |
var body: some View { |
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//------------------------------------------------------------------------ | |
// The SwiftUI Lab: Advanced SwiftUI Animations | |
// https://swiftui-lab.com/swiftui-animations-part1 (Animating Paths) | |
// https://swiftui-lab.com/swiftui-animations-part2 (GeometryEffect) | |
// https://swiftui-lab.com/swiftui-animations-part3 (AnimatableModifier) | |
//------------------------------------------------------------------------ | |
import SwiftUI | |
struct ContentView: View { | |
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// | |
// ContentView.swift | |
// Layout | |
// | |
// Created by Matt Gallagher on 7/6/19. | |
// Copyright © 2019 Matt Gallagher. All rights reserved. | |
// | |
import SwiftUI |
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extension UIView { | |
@objc func exerciseAmbiguityInLayoutRepeatedly() { | |
if self.hasAmbiguousLayout { | |
Timer.scheduledTimer(timeInterval: 0.5, | |
target: self, | |
selector: #selector(UIView.exerciseAmbiguityInLayout), | |
userInfo: nil, | |
repeats: true) | |
} | |
} |
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import Darwin | |
@dynamicMemberLookup | |
struct Environment { | |
subscript(dynamicMember name: String) -> String? { | |
get { | |
guard let value = getenv(name) else { return nil } | |
return String(validatingUTF8: value) | |
} |
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import Cocoa | |
public struct UIEdgeInsets { | |
public var top: CGFloat // specify amount to inset (positive) for each of the edges. values can be negative to 'outset' | |
public var left: CGFloat | |
public var bottom: CGFloat | |