Throughout this evolutionary process, the Mach APIs used in OS X diverged in many ways from the original CMU Mach 3 APIs. Never assume that a pointer will always be the same size as an int or long. These are described in Standard C Naming Conventions and C++ Naming Conventions, respectively. This section refines those conventions in ways that should make them more useful to you as a programmer. page. Later, this and code from OSF’s commercial development efforts were incorporated into Darwin’s kernel. To use these, you may have to declare dependencies on any of the following: com.apple.kernel—You should generally avoid this. One of the most common problems faced when programming in the kernel is use of “standard” functions—things like printf or bcopy. Don’t sleep while holding resources (locks, for example). Set a daily schedule for putting your Mac to sleep or turning it off and on. Because standard C has an even greater chance of namespace collision than C++, it is essential that you follow these guidelines when writing C code for use in the kernel. The goal of this document is to describe the various major components of OS X at a conceptual level, then provide more detailed programming information for developers working in each major area. The next part describes Mach and the bootstrap task, including information about IPC, bootstrap contexts, ports and port rights, and so on. If you decide to use AltiVec in the kernel, your code can determine whether the CPU supports AltiVec using the sysctlbyname call to get the hw.optional.altivec property. The best and most reliable workaround, however, is to disconnect all devices, then re-connect them one by one (over a series of days if necessary) and check for persistence of kernel panics. I keep getting the message: The kernel appears to have died. Overview. Do name global variables in a way that protects you from collision. For more information about APIs available to I/O Kit KEXTs, see Kernel Framework Reference. disabling the cooling fan and running the CPU full tilt. The third part describes the I/O Kit and BSD. The goal of this document is very broad, providing a firm grounding in the fundamentals of OS X kernel programming for developers from many backgrounds. Apple's Unsolicited Idea Submission Policy. How to Fix Recurring Kernel Panic with “com.apple.driver.AppleMobileFileIntegrity” Whenever you encounter any kernel panic, you need to figure out first whether it is caused by a hardware or software problem. Dynamically allocated variables are preferred (using malloc or equivalent) over local variables for objects more than a few bytes in size. If you must deploy your KEXT on earlier versions of OS X, you must either provide a non-AltiVec version of your code or perform the AltiVec instructions in user space. Kernel programming style is very much a matter of personal preference, and it is not practical to programmatically enforce the guidelines in this chapter. The idea that a team rewrote a service in Rust means Apple is "all-in" in Rust is ridiculous. This includes the chapters Mach Overview, Memory and Virtual Memory, Mach Scheduling and Thread Interfaces, and Bootstrap Contexts. Fix Type: Software. This includes the chapters Kernel Extension Overview and Building and Debugging Kernels. For this reason, the bibliography contains high-level references that should help familiarize you with some of the basic concepts that you need to understand fully the material in this document. Additional terms from Apple or Apple’s trade-in partners may apply. The move is a shift for Apple, who had encrypted the kernel in past versions of iOS, leaving developers and researchers out of the … To check if any hardware issue is behind these occurrences, follow the steps here: 1. While using the lower-level functionality is not expressly forbidden, it is generally discouraged (though printf is always fine). Always use sizeof if you need this information. If you need to share these across files within your KEXT, you can achieve a similar effect by declaring them __private_extern__. Each part begins with an overview chapter or chapters, followed by chapters that address particular areas of interest. The I/O Kit is described at only a high level, since it is primarily of interest to driver developers. It also provides background for system programmers and developers of device drivers, file systems, and network extensions. This is not a document on drivers. Every large company I've worked at has had many, many internal services using all sorts of different languages/frameworks. Be sure to read the first document in the series, Mac Technology Overview, if you are not familiar with OS X. Apple-certified screen repairs are performed by trusted experts who use genuine Apple parts. An an ex-Apple engineer I can assure almost every programming language you can think of is probably used by one team or another. In particular, never do this: unless you have already verified that argptr cannot possibly be NULL. Important: If you are writing an I/O Kit KEXT, most of these functions are not what you are looking for. com.apple.kernel.iokit—The I/O Kit (v10.4 and later). With OS X and iOS Kernel Programming, you’ll: Discover classical kernel architecture topics such as … Be sure to deallocate memory when its reference count reaches zero, but not before. Please read Apple's Unsolicited Idea Submission Policy This part contains the chapters Keep Out, Kernel Architecture Overview, The Early Boot Process, Security Considerations, Performance Considerations, and Kernel Programming Style. com.apple.kernel.mach—Mach-specific APIs (v10.4 and later). It was not possible to detect this support from within the kernel until a later 10.3 software update. As noted, kernel extension programming errors can cause all sorts of problems, from crashing the system to local privilege escalation and data leakage. Basic I/O Kit C++ naming conventions are defined in the document IOKit Device Driver Design Guidelines. A good example is the use of mutexes rather than spinlocks. Similarly, names like. OS X and iOS Kernel Programming combines essential operating system and kernel architecture knowledge with a highly practical approach that will help you write effective kernel-level code. These guidelines should provide a good starting point. You can also find CMU Mach white papers by searching for Mach on the CMU computer science department’s website (http://www.cs.cmu.edu), along with various source code samples. If a kernel panic does occur: Proceed the next section to check the internal RAM and third-party hardware. It covers device drivers at a high level only. before you send us your feedback. If you run into problems, you should join the appropriate Darwin discussion list and ask questions. No commitment. This includes the chapters I/O Kit Overview, BSD Overview, File Systems Overview, and Network Architecture. Many commonly used standard C library functions are implemented in the kernel. Keeps the computer from going to sleep when the display sleeps. The key question people should keep in mind when they do kernel programming is "where am I". It is also not possible to cover every detail of certain parts of the kernel. The fifth part explains how to build and debug the kernel and kernel extensions. Disconnect all peripheral devices. Your input helps improve our developer documentation. Because C does not have the benefit of classes, it is much easier to run into a naming conflict between two functions. Normal headers (those in /usr/include) cannot be used in the kernel. Functions should have as few arguments as possible. com.apple.kpi.unsupported—Unsupported legacy functionality (v10.4 and later). To troubleshoot out-of-control kernel_task specifically, here are some useful commands: Profile entire system, focusing on the kernel process (PID: 0), run: sudo spindump 0 -reveal For specific process (like launchd), use sample, e.g. For example, Apple uses NS, CF, IO, and other prefixes to indicate that functions belong to specific frameworks. Programming in the kernel is subject to a number of restrictions that do not exist in application programming. Table 7-1 lists some commonly used C functions, variables, and types, and gives the location of their prototypes. Also, since unused memory (and particularly wired memory) can cause performance degradation, you should be careful to deallocate memory when it is no longer in use, and you should never allocate large regions of wired memory. But the weird thing is, if I import matplotlib.pyplot and plot some random graph first, the above code plots just fine. If you have several applications in your macOS, uninstall them and see if that stops kernel panic. before you send us your feedback. Follow the reverse DNS name with the name of your project. These are only suggested guidelines. OS X is based on the Mach 3.0 microkernel, designed by Carnegie Mellon University, and later adapted to the Power Macintosh by Apple and the Open Software Foundation Research Institute (now part of Silicomp). It is not forbidden, but is strongly discouraged. However, even limiting yourself to documented interfaces does not protect you from a handful of pitfalls. This ensures that you will not collide with classes created by other companies or with future classes added to the operating system by Apple. You can find the lists at http://www.lists.apple.com/. Terms of Use | Privacy Policy | Updated: 2013-08-08. Learn about Apple Diagnostics reference codes. This part contains the chapters Keep Out, Kernel Architecture Overview, The Early Boot Process, Security Considerations, Performance Considerations, and Kernel Programming Style. Never assume that the size of an instance of a type will never change. These are some examples of unacceptable names: In short, picking any name that you would normally pick for a function is generally a bad idea, because every other developer writing code is likely to pick the same name for their function. Start up automatically after a power failure. Never begin a function name with an underscore (_). Pass pointers to structures, not the broken out elements. In general, any non–I/O Kit header that you can safely include in the kernel is located in xnu/bsd/sys or xnu/osfmk/mach, although there are a few specialized headers in other places like libkern and libsa. For more thorough coverage of performance and stability, you should also read the chapters Security Considerations and Performance Considerations. If the issue is caused by software on your Mac, one of these steps might help: Install all available software updates. In addition, it goes into detail about topics of interest to kernel programmers as a whole. If you fall into one of these categories, you may find this document helpful. Your input helps improve our developer documentation. You should also structure your locks in such a way to minimize contention and to minimize hold times on the most highly contended locks. I never wanted to program for Windows. This includes issues such as security, SMP safety, style, performance, and the OS X kernel architecture as a whole. $9.99/month after free trial. Apple released the developer preview of iOS 10 more than a week ago, and security experts have found that the kernel code of the system is unencrypted. This document, Kernel Programming, is part of the Apple Reference Library. Unused applications affect your Mac's speed and might initiate a kernel panic too. These additional guidelines are intended to minimize the chance of accidentally breaking your own software and to improve readability of code by developers. If the standard C function you are trying to use is not in one of these files, chances are the function is not supported for use within the kernel, and you need to implement your code in another way. If you plan to do extensive work inside the OS X kernel, you may find it convenient to have a complete Mach API reference, since this document only documents the most common and useful portions of the Mach API. To submit a product bug or enhancement request, please visit the Functions not obeying these rules can cause a kernel panic, or in extreme cases, do not even compile. Apple Developer Connection: OS X (http://developer.apple.com/devcenter/mac/). In order to use them, however, you need to include the appropriate prototypes, which may be different from the user space prototypes for those functions, and which generally have different names when included from kernel code. In general, you should avoid doing using floating-point math or AltiVec instructions in the kernel unless doing so will result in a significant speedup. Prevent computer from sleeping automatically when the display is off. While most terms are defined when they first appear, the definitions are all in the glossary for convenience. The naming conventions for C++ have been defined for some time in the document IOKit Device Driver Design Guidelines. However, these symbols are only available in v10.4 and later. page. Please try submitting your feedback later. In addition to these issues, programming in the kernel has the potential for compatibility problems. You can obtain other documents from the Apple Developer Documentation website at http://developer.apple.com/documentation. Kernel Panic, though sounding scary, is simply an occurrence when your Mac keeps restarting for For other areas, such as network kernel extensions or file system KEXTs, you must use the KPI versions if you want your extension to load in OS X v10.4 and later. Bug Reporter Where possible, you should specify a dependency on the KPI version of these symbols. If you program only to the interfaces discussed in this document or other Apple documents, you will avoid the majority of these. sudo sample launchd or by PID. Offers SDKs, release notes, product notes and news, and other resources and information related to OS X. AppleCare Tech Info Library (http://www.apple.com/support/). Tip 11 Uninstall applications on your Mac. If a term seems familiar, it probably means what you think it does. My day job is in banking/finance. This also applies to large local arrays. The first and most important is the stack size. Also includes legacy documentation. This single question has two distinct aspects: where am I in the memory, and where am I … The biggest potential problem that you face is namespace collision, which occurs when your function, variable, or class name is the same as someone else’s. Thus, for things like audio drivers, the above does not apply. Since this makes one kernel extension or the other fail to load correctly (in a non-deterministic fashion), Apple has established function naming conventions for C and C++ code within the kernel. Each function name should use Java-style reverse DNS naming. Despite concerns Apple would not allow the app, it was cleared on the App Store in just two days, Esser said. For this reason, the following conventions are suggested: Declare all functions and (global) variables static where possible to prevent them from being seen in the global namespace. If you are writing device drivers, you should primarily read the document IOKit Fundamentals, but you may still find this document helpful as background reading. Kernel panics in OS X occur primarily because your Mac has faulty or incompatible hardware, or because you are using incompatible or poorly written kernel extension drivers. Buffer cache functions (bread, bwrite, and brelse). For the I/O Kit and libkern, this should make little difference. It is important to stress the care needed when writing code that resides in the kernel, however, as noted in Keep Out. Page Faults as found in your Kernel Panic if not caused by software is most likely a hardware memory issue. In addition, applications such as Adobe Creative Suite have full installers rather than the more widely used drag and … The kernel has a limited amount of space allocated for thread stacks, which can cause problems if you aren’t aware of the limitation. The fourth part describes kernel services, including boundary crossings, synchronization, queues, clocks, timers, shutdown hooks, and boot option handling. You can write most software entirely in user space. It defines the base class for I/O Kit device drivers (IOService), several helper classes, and the families that support many types of devices. For example: Use prefixes in function and method names to make it easier to see relationships between them. As described in Keep Out, programming in the kernel is fraught with hazards that can cause instability, crashes, or security holes. Do not attempt to use them. I have to admit this - I gave up programming when it appeared Apple was going to go away. To avoid namespace collisions, you should prefix the names of classes and families with project names or other reasonably unique prefix codes. Apple worked hard to try and convince Netflix to keep using in-app purchases for the iOS version of its app, according to emails shared during the Epic Games v. Apple lawsuit. The Kernel Panic appears related to an Adobe product so you should make sure they are all up to date. Understanding Apple’s operating systems will allow you to write efficient device drivers, such as those covered in the book, using I/O Kit. ; If your Mac suspects that a particular app caused the restart, it might ask whether you would like to move the app to the Trash. Under no circumstances should you use common names for your functions without prefixing them with the name of your project in some form. For example, do not use allocation routines from the I/O Kit and deallocation routines from BSD. Use reference counts to avoid freeing memory that is still in use elsewhere. The first part is a kernel programming overview, which discusses programming guidelines that apply to all aspects of kernel programming. This might be as simple as prefixing a function with the name of the enclosing or related class, or it might be some other scheme that makes sense for your project. Use macro expansion to save typing, for example PROJECT_eat could expand to com_apple_driver_schlassen_pickle_eat. Your company or organization should adopt its own set of guidelines within the constraints of the basic conventions described in the previous section. Use hierarchical names if you anticipate multiple projects with similar names coming from different parts of your company or organization. This document is, to a degree, a reference document. Likewise, do not use IOMallocContiguous with IOFreePageable. For example, if you are working on a video capture driver, and one of its classes is called capture, you will probably encounter a name collision eventually. The introductory sections should be easily read, and we recommend that you do so in order to gain a general understanding of each topic. These guidelines were created based on frequent problems reported by developers writing code in the kernel. Occasional conflicts are a fact of life. Never dereference pointers without verifying that they are not NULL. and a restart and a red "Dead kernel" tag on the toolbar. Use the Java-style reverse DNS naming convention, substituting underscores for periods. Please try submitting your feedback later. For example, if you work at Apple and were working on project Schlassen, you would start each function name (in drivers) with com_apple_driver_schlassen_. This includes the chapters Boundary Crossings, Synchronization Primitives, and Miscellaneous Kernel Services. While this is not forbidden, it is strongly discouraged to avoid deadlock. Apple maintains several websites where developers can go for general and technical information on OS X. Apple Developer Connection: Developer Documentation (http://developer.apple.com/documentation). You may find older versions of the Mach source code interesting, both to satisfy historical curiosity and to avoid remaking mistakes made in earlier implementations. It does, however, cover some areas of interest to driver writers, such as crossing the user-kernel boundary. Finally, AltiVec data stream instructions (dst, dstt, dstst, dss, and dssall) are not supported in the kernel, even for processors that support them in user space. For more information, see The sysctlbyname System Call. It will restart automatically. However, no conventions have been given for standard C code. However, by following these few simple rules, you should be able to avoid the majority of common namespace pitfalls. Never assume that your code will be run only on big endian processors. The BSD subsystem is covered in more detail, including descriptions of BSD networking and file systems. For a complete list of symbols in any of these dependencies, run nm on the binaries in /System/Library/Extensions/System.kext/PlugIns. You’ll learn fundamental concepts such as memory management and thread synchronization, as well as the I/O Kit framework. If it’s unfamiliar, check the glossary. In addition to issues of stack size, you should also avoid doing anything that would generate unnecessary load such as polling a device or address. This may be unavoidable in some applications, but should be avoided whenever possible and disposed of at the earliest possible opportunity. For example, com_apple_foo. Schedule. Kernel programming should be avoided if Fortunately, kernel programming is usually unnecessary. Terms of Use | Privacy Policy | Updated: 2013-08-08. Resolving Kernel Panics. Don’t use arguments to avoid using global or class variables. com.apple.kernel.libkern—General-purpose functions (v10.4 and later). Try running the Apple Diagnostics. In any case, all readers may want to skim through the glossary, in case there are subtle differences between OS X usage and that of other operating systems. The Kernel Framework provides the APIs and support for kernel-resident device drivers and other kernel extensions. I'm using OpenCL on an nvidia GPU and I keep getting CL_INVALID_KERNEL_ARGS when I try to execute a kernel. Instead, you should name the class something like com_mycompany_driver_myproduct_capture. Bug Reporter Up-to-date versions of the Mach 3 APIs that OS X provides are described in the Mach API reference in the kernel sources. com.apple.kpi.bsd—BSD portions of the kernel (v10.4 and later). To repeat the test, click “Run the test again” or press Command-R. To restart your Mac, click Restart or press R. For example, if project Schlassen is an I/O Kit family, function names should all begin with com_apple_iokit_schlassen_. This document has a wide and diverse audience—specifically, the set of potential system software developers for OS X, including the following sorts of developers: developers of software that modifies file system data on-the-fly, system programmers familiar with BSD, Linux, and similar operating systems, developers who want to learn about kernel programming. The purpose of this document is to provide fundamental high-level information about the OS X core operating-system architecture. I was and remain a complete Apple fanboy (though I do have 2 windows machines in addition to 3 macs). If you anticipate that the last part of a function name may be the same as the last part of another function name (for example, PROJECT1_eat and PROJECT2_eat), you should change the names to avoid confusion (for example, PROJECT1_eatpickle and PROJECT2_eatburger). To submit a product bug or enhancement request, please visit the Likewise, the first part of each chapter, and in many cases, of sections within chapters, will be tailored to providing a general understanding of individual topics. 4. The "You need to restart your computer" alert indicates a kernel panic.This FAQ, based on the "Kernel Panics" chapter of our book Troubleshooting Mac® OS X, provides a set of procedures which should resolve most kernel panics.. Additional information, including how to use and interpret panic logs for troubleshooting, can be found in the "Kernel … I learned C programming in 1994 on a Mac Quadra. Test code in sections and try to think up likely edge cases for calculations. It does not protect you from other projects created within your company, however, and for this reason, some additional guidelines are suggested. Due to the complex nature of kernel programming and limitations on the length of this document, however, it is not always possible to provide introductory material for developers who do not have at least some background in their area of interest. Copyright © 2002, 2013 Apple Inc. All Rights Reserved. Sometimes a software problem is actually caused by another app that’s incompatible. No one can force you to use good style in your programming, but if you do not, you do so at your own peril. This was known as osfmk, and was part of MkLinux (http://www.mklinux.org). The document ends with a glossary of terms used throughout the preceding chapters as well as a bibliography which provides numerous pointers to other reference materials. This section includes some basic tips on performance and stability. Avoid conflicting with any names already in the kernel, and do not use prefixes similar to those of existing kernel functions that you may be working with. Kernel Programming Style As described in Keep Out, programming in the kernel is fraught with hazards that can cause instability, crashes, or security holes. To maximize readability, you should use macros to rename classes and families at compile time. MkLinux maintains an active CVS repository with their recent versions of Mach kernel source code. Note: In cases where altivec or floating point has already been used in user space in the calling thread, there is no additional penalty for using them in the kernel. Second, AltiVec was not supported in the kernel prior to OS X v10.3. If the Apple Diagnostics don't find a problem, then try running Memtest86. http://developer.apple.com/devcenter/mac/, Apple's Unsolicited Idea Submission Policy. With Apple announcing that Kernel Extensions will be deprecated at Worldwide Developers Conference (WWDC) 2019, we can expect a lot of changes coming to macOS. While most Mac applications are just an app in the Applications folder, they can still place additional files elsewhere. Copyright © 2002, 2013 Apple Inc. All Rights Reserved. The symbols in these header files are divided among multiple symbol sets, depending on the technology area where they were designed to be used. Please read Apple's Unsolicited Idea Submission Policy To access and use all the features of Apple Card, you must add Apple Card to Wallet on an iPhone or iPad with iOS 12.4 or later or iPadOS. A bug in the kernel could cause random crashes, data corruption, or even render the operating system inoperable…Kernel programming is a black art that should be avoided if at all possible. First, the kernel takes a speed penalty whenever floating-point math or AltiVec instructions are used in a system call context (or other similar mechanisms where a user thread executes in a kernel context), as floating-point and AltiVec registers are only maintained when they are in use. Apple Diagnostics shows a progress bar while it's checking your Mac: When testing is complete, Apple Diagnostics shows the results, including one or more reference codes. Be careful to allocate and free memory with matching calls. For families, you should instead use iokit. Remove Unused Apps. In addition to compatibility problems, kernel extensions that misbehave can also dramatically decrease the system’s overall performance or cause crashes. There are a number of issues that you should consider when deciding whether to use floating point math or AltiVec vector math in the kernel. The kernel is expecting a fixed length of those packets but doesn’t check to prevent writing past the end of the buffer. To gather memory consumption by kernel task, use (sorted by dirty by default): In other words, the following code works fine. com.apple.kernel.mach—Mach-specific APIs. Contains technical articles, tutorials, FAQs, technical notes, and other information. It is divided into several parts. Large stack variables (function local) are dangerous. These tips cover only style issues, not general performance or stability issues. Allocating large contiguous blocks of memory at boot time is almost never acceptable, because it cannot be released. This means the following: Recursion must be bounded (to no more than a few levels). Older versions can be obtained through various Internet sites. The next part describes Mach and the bootstrap task, including information about IPC, bootstrap contexts, ports and port rights, and so on. Plan automatically renews after trial until cancelled. The kernel control (kern_control) API, which uses the SYSPROTO_CONTROL protocol, allows applications to configure and control a KEXT.The kernel event (kern_event) API, which uses the SYSPROTO_EVENT protocol, allows applications and other KEXTs to be notified when certain kernel events occur.It should be used when multiple clients need to know about … Note: A combination of peripherals may be the cause of a kernel panic. The kernel sources can be found in the xnu project on http://kernel.macosforge.org/. However, you should not plan to read this document cover to cover, but rather, take note of topics of interest so that you can refer back to them when the need arises. Do not use them. Start up your Mac after a power interruption. Some of these issues are described in Performance and Stability Tips.