Patch (computing)

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(Redirected from
Firmware update
)

A patch is a set of changes to a

better source needed] Patches are often written to improve the functionality, usability, or performance
of a program. The majority of patches are provided by software vendors for operating system and application updates.

Patches may be installed either under programmed control or by a human programmer using an editing tool or a debugger. They may be applied to program files on a storage device, or in computer memory. Patches may be permanent (until patched again) or temporary. Similarly, patches may be prepared by hand, or created by an automatic difference-finding tool that compares two similar files and determines what changes are needed to transform one into another.

Most patches must be applied to exactly the version of the file they are intended to modify, although if the change is small and similar in a number of versions, this requirement may not apply. Many automated patching tools can support patches for multiple versions of files by detecting the version of the existing file and applying an appropriate patch. As more and more versions are released, the cumulative size of such patches may become larger than the updated file, at which point the number of supported previous versions may be reduced, or a complete copy of the updated file may be provided instead.

Patching makes possible the modification of compiled and machine language object programs when the source code is unavailable. This demands a thorough understanding of the inner workings of the object code by the person creating the patch, which is difficult without close study of the source code. Someone unfamiliar with the program being patched may install a patch using a patch utility created by another person. Even when the source code is available, patching makes possible the installation of small changes to the object program without the need to recompile or reassemble. For minor changes to software, it is often easier and more economical to distribute patches to users rather than redistributing a newly recompiled or reassembled program.

Although meant to fix problems, poorly designed patches can sometimes introduce new problems (see software regressions). In some special cases updates may knowingly break the functionality or disable a device, for instance, by removing components for which the update provider is no longer licensed.

Patch management is a part of lifecycle management, and is the process of using a strategy and plan of what patches should be applied to which systems at a specified time.

Types

Binary patches

Patches for

executable files instead of source code
. When executed these files load a program into memory which manages the installation of the patch code into the target program(s) on disk.

Patches for other software are typically distributed as data files containing the patch code. These are read by a patch

utility program which performs the installation. This utility modifies the target program's executable file—the program's machine code—typically by overwriting its bytes with bytes representing the new patch code. If the new code will fit in the space (number of bytes) occupied by the old code, it may be put in place by overwriting directly over the old code. This is called an inline patch. If the new code is bigger than the old code, the patch utility will append load record(s) containing the new code to the object file of the target program being patched. When the patched program is run, execution is directed to the new code with branch instructions (jumps or calls) patched over the place in the old code where the new code is needed. On early 8-bit microcomputers, for example the Radio Shack TRS-80
, the operating system includes a PATCH/CMD utility which accepts patch data from a text file and applies the fixes to the target program's executable binary file(s).

The patch code must have place(s) in memory to be executed at runtime. Inline patches are no difficulty, but when additional memory space is needed the programmer must improvise. Naturally if the patch programmer is the one who first created the code to be patched, this is easier. Savvy programmers plan in advance for this need by reserving memory for later expansion, left unused when producing their final iteration. Other programmers not involved with the original implementation, seeking to incorporate changes at a later time, must find or make space for any additional bytes needed. The most fortunate possible circumstance for this is when the routine to be patched is a distinct module. In this case the patch programmer need merely adjust the pointers or length indicators that signal to other system components the space occupied by the module; he is then free to populate this memory space with his expanded patch code. If the routine to be patched does not exist as a distinct memory module, the programmer must find ways to shrink the routine to make enough room for the expanded patch code. Typical tactics include shortening code by finding more efficient sequences of instructions (or by redesigning with more efficient algorithms), compacting message strings and other data areas, externalizing program functions to mass storage (such as disk overlays), or removal of program features deemed less important than the changes to be installed with the patch.

Small in-memory machine code patches can be manually applied with the system debug utility, such as CP/M's DDT or MS-DOS's DEBUG debuggers. Programmers working in interpreted BASIC often used the POKE command to alter the functionality of a system service routine or the interpreter itself.

Source code patches

Patches can also circulate in the form of source code modifications. In this case, the patches usually consist of textual differences between two source code files, called "

open-source software projects
. In these cases, developers expect users to compile the new or changed files themselves.

Large patches

Because the word "patch" carries the connotation of a small fix, large fixes may use different nomenclature. Bulky patches or patches that significantly change a program may circulate as "

Microsoft Windows NT and its successors (including Windows 2000, Windows XP, Windows Vista and Windows 7) use the "service pack" terminology.[3] Historically, IBM used the terms "FixPaks" and "Corrective Service Diskette" to refer to these updates.[4]

History

A program tape for the 1944 Harvard Mark I, one of the first digital computers. Note physical patches used to correct punched holes by covering them.

Historically, software suppliers distributed patches on

Windows ME
, PC operating systems gained the ability to get automatic software updates via the Internet.

Computer programs can often coordinate patches to update a target program. Automation simplifies the end-user's task – they need only to execute an update program, whereupon that program makes sure that updating the target takes place completely and correctly. Service packs for

Microsoft Windows NT
and its successors and for many commercial software products adopt such automated strategies.

Some programs can update themselves via the Internet with very little or no intervention on the part of users. The maintenance of server software and of operating systems often takes place in this manner. In situations where system administrators control a number of computers, this sort of automation helps to maintain consistency. The application of security patches commonly occurs in this manner.

With the advent of larger storage media and higher Internet bandwidth, it became common to replace entire files (or even all of a program's files) rather than modifying existing files, especially for smaller programs.

Application

The size of patches may vary from a few

computer games
. Compared with the initial installation of software, patches usually do not take long to apply.

In the case of

Package management systems
can offer various degrees of patch automation.

Usage of completely automatic updates has become far more widespread in the consumer market, due largely[

beta test
.

Applying patches to firmware poses special challenges, as it often involves the provisioning of totally new firmware images, rather than applying only the differences from the previous version. The patch usually consists of a firmware image in form of binary data, together with a supplier-provided special program that replaces the previous version with the new version; a motherboard BIOS update is an example of a common firmware patch. Any unexpected error or interruption during the update, such as a power outage, may render the motherboard unusable. It is possible for motherboard manufacturers to put safeguards in place to prevent serious damage; for example, the update procedure could make and keep a backup of the firmware to use in case it determines that the primary copy is corrupt (usually through the use of a checksum, such as a CRC).

Video games

MMORPGs
, which are typically very complex with large amounts of content, almost always rely heavily on patches following the initial release, where patches sometimes add new content and abilities available to players. Because the balance and fairness for all players of an MMORPG can be severely corrupted within a short amount of time by an exploit, servers of an MMORPG are sometimes taken down with short notice in order to apply a critical patch with a fix.

Companies sometimes release games knowing that they have bugs. Computer Gaming World's Scorpia in 1994 denounced "companies—too numerous to mention—who release shoddy product knowing they can get by with patches and upgrades, and who make 'pay-testers of their customers".[6]

In software development

Patches sometimes become mandatory to fix problems with

libraries or with portions of source code
for programs in frequent use or in maintenance. This commonly occurs on very large-scale software projects, but rarely in small-scale development.

In open-source projects, the authors commonly receive patches or many people publish patches that fix particular problems or add certain functionality, like support for local languages outside the project's locale. In an example from the early development of the Linux kernel (noted for publishing its complete source code), Linus Torvalds, the original author, received hundreds of thousands of patches from many programmers to apply against his original version.

The Apache HTTP Server originally evolved as a number of patches that Brian Behlendorf collated to improve NCSA HTTPd, hence a name that implies that it is a collection of patches ("a patchy server"). The FAQ on the project's official site states that the name 'Apache' was chosen from respect for the Native American Indian tribe of Apache. However, the 'a patchy server' explanation was initially given on the project's website.[7]

Variants

Hotfix

A hotfix or Quick Fix Engineering update (QFE update) is a single, cumulative package that includes information (often in the form of one or more files) that is used to address a problem in a software product (i.e., a software bug). Typically, hotfixes are made to address a specific customer situation. Microsoft once used this term but has stopped in favor of new terminology: General Distribution Release (GDR) and Limited Distribution Release (LDR). Blizzard Entertainment, however, defines a hotfix as "a change made to the game deemed critical enough that it cannot be held off until a regular content patch".

Point release

A point release is a

features
. Often, there are too many bugs to be fixed in a single major or minor release, creating a need for a point release.

Program temporary fix

Program temporary fix or Product temporary fix (PTF), depending on date, is the standard IBM terminology for a single bug fix, or group of fixes, distributed in a form ready to install for customers. A PTF was sometimes referred to as a “ZAP”.[8] Customers sometime explain the acronym in a tongue-in-cheek manner as permanent temporary fix or more practically probably this fixes, because they have the option to make the PTF a permanent part of the operating system if the patch fixes the problem.

Security patches

A security patch is a change applied to an asset to correct the weakness described by a vulnerability. This corrective action will prevent successful exploitation and remove or mitigate a threat's capability to exploit a specific vulnerability in an asset. Patch management is a part of vulnerability management – the cyclical practice of identifying, classifying, remediating, and mitigating vulnerabilities.

Security patches are the primary method of fixing security vulnerabilities in software. Currently Microsoft releases its security patches once a month, and other operating systems and software projects have security teams dedicated to releasing the most reliable software patches as soon after a vulnerability announcement as possible. Security patches are closely tied to

responsible disclosure
.

These security patches are critical to ensure that business process does not get affected. In 2017, companies were struck by a ransomware called WannaCry which encrypts files in certain versions of Microsoft Windows and demands a ransom via BitCoin. In response to this, Microsoft released a patch which stops the ransomware from running.

Service pack

A service pack or SP or a feature pack (FP) comprises a collection of updates, fixes, or enhancements to a software program delivered in the form of a single installable package. Companies often release a service pack when the number of individual patches to a given program reaches a certain (arbitrary) limit, or the software release has shown to be stabilized with a limited number of remaining issues based on users' feedback and bug tracking such as Bugzilla. In large software applications such as office suites, operating systems, database software, or network management, it is not uncommon to have a service pack issued within the first year or two of a product's release. Installing a service pack is easier and less error-prone than installing many individual patches, even more so when updating multiple computers over a network, where service packs are common.

Unofficial patches

An unofficial patch is a patch for a program written by a third party instead of the original

game community of a video game which became unsupported.[11][12]

Monkey patches

Monkey patching means extending or modifying a program locally (affecting only the running instance of the program).

Hot patching

Hot patching, also known as live patching or dynamic software updating, is the application of patches without shutting down and restarting the system or the program concerned. This addresses problems related to unavailability of service provided by the system or the program.[13] Method can be used to update Linux kernel without stopping the system.[14][15] A patch that can be applied in this way is called a hot patch or a live patch. This is becoming a common practice in the mobile app space.

method swizzling to deliver hot patches to the iOS ecosystem.[17] Another method for hot-patching iOS apps is JSPatch.[18]

Cloud providers often use hot patching to avoid downtime for customers when updating underlying infrastructure.[19]

Slipstreaming

In computing, slipstreaming is the act of integrating patches (including service packs) into the installation files of their original app, so that the result allows a direct installation of the updated app.[20][21]

The nature of slipstreaming means that it involves an initial outlay of time and work, but can save a lot of time (and, by extension, money) in the long term. This is especially significant for administrators that are tasked with managing a large number of computers, where typical practice for installing an operating system on each computer would be to use the original media and then update each computer after the installation was complete. This would take a lot more time than starting with a more up-to-date (slipstreamed) source, and needing to download and install the few updates not included in the slipstreamed source.

However, not all patches can be applied in this fashion and one disadvantage is that if it is discovered that a certain patch is responsible for later problems, said patch cannot be removed without using an original, non-slipstreamed installation source.

Software update systems

A Sparkle software update prompt on macOS

Software update systems allow for updates to be managed by users and software developers. In the

deterministic, distributed builds are likely the only way to defend against malware that attacks the software development and build processes to infect millions of machines in a single, officially signed, instantaneous update.[24] Update managers also allow for security updates to be applied quickly and widely. Update managers of Linux such as Synaptic allow users to update all software installed on their machine. Applications like Synaptic use cryptographic checksums to verify source/local files before they are applied to ensure fidelity against malware.[25][26]

See also

References

  1. ^ a b "Microsoft issues biggest software patch on record". Reuters. 2009-10-14. Archived from the original on 16 October 2009. Retrieved 14 October 2009.
  2. ^ "What is a Bug Fix? – Definition from Techopedia". techopedia.com. Archived from the original on 2018-07-03. Retrieved 2015-07-29.
  3. ^ "Service Pack and Update Center". windows.microsoft.com. Archived from the original on 2015-06-01. Retrieved 2015-06-01.
  4. ^ "Glossary of terms". www.tavi.co.uk. Archived from the original on 2016-12-01. Retrieved 2016-11-23.
  5. . Retrieved 2015-01-08. Uninstall High Definition Audio driver patch KB835221 & KB888111 [...]
  6. ^ Scorpia (April 1994). "So You Want To Be A Hero?". Scorpion's View. Computer Gaming World. pp. 54–58.
  7. ^ "Apache HTTP Server Project". 15 June 1997. Archived from the original on 15 June 1997.{{cite web}}: CS1 maint: bot: original URL status unknown (link)
  8. ^ "SPZAP (a.k.a. Superzap): Dynamically update programs or data". IBM Knowledge Center. Archived from the original on 2020-05-24. Retrieved 2020-02-23.
  9. ^ Barwise, Mike (2007-10-16). "Unofficial patch for Windows URI problem". The H Security. Archived from the original on 2021-04-29. Retrieved 2012-01-29.
  10. ^ "Another unofficial IE patch offered to counter critical flaw". Computer Weekly. 2006-03-30. Archived from the original on 2021-05-02. Retrieved 2013-07-09. Another unofficial patch has been released to counter a critical flaw in Microsoft's Internet Explorer browser.
  11. ^ Wen, Howard (2004-06-10). "Keeping the Myths Alive". linuxdevcenter.com. Archived from the original on 2013-04-06. Retrieved 2012-12-22. [...]fans of the Myth trilogy have taken this idea a step further: they have official access to the source code for the Myth games. Organized under the name MythDevelopers, this all-volunteer group of programmers, artists, and other talented people devote their time to improving and supporting further development of the Myth game series.
  12. ^ Bell, John (2009-10-01). "Opening the Source of Art". Technology Innovation Management Review. Archived from the original on 2014-03-30. Retrieved 2012-12-30. [...]that no further patches to the title would be forthcoming. The community was predictably upset. Instead of giving up on the game, users decided that if Activision wasn't going to fix the bugs, they would. They wanted to save the game by getting Activision to open the source so it could be kept alive beyond the point where Activision lost interest. With some help from members of the development team that were active on fan forums, they were eventually able to convince Activision to release Call to Power II's source code in October of 2003.
  13. ^ "Oracle Magazine". Oracle.com. Archived from the original on 2008-05-14. Retrieved 2013-01-04.
  14. ^ "Live patching the Linux kernel". Archived from the original on 2020-10-28. Retrieved 2020-10-25.
  15. ^ "Linux Kernel Live Patching: What It is and Who Needs It". 6 March 2020. Archived from the original on 28 October 2020. Retrieved 25 October 2020.
  16. ^ "Hot or Not? The Benefits and Risks of iOS Remote Hot Patching « Threat Research Blog". FireEye. Archived from the original on 2016-10-26. Retrieved 2016-10-26.
  17. ^ Perez, Sarah (22 September 2015). "Rollout.io Puts Mobile Developers Back In Control Of Their Apps". TechCrunch. Archived from the original on 2016-11-27. Retrieved 2016-10-26.
  18. ^ "bang590/JSPatch". GitHub. Archived from the original on 2017-01-04. Retrieved 2016-10-26.
  19. ^ "Hot Patching SQL Server Engine in Azure SQL Database". Techcommunity Microsoft. 2019-09-11. Archived from the original on 2019-09-13. Retrieved 2019-09-15.
  20. PC Magazine. Ziff Davis. Archived
    from the original on 9 January 2018. Retrieved 7 September 2017.
  21. ^ Thurrott, Paul (7 May 2008). "Slipstreaming Windows XP with Service Pack 3 (SP3)". Supersite for Windows. Penton. Archived from the original on 11 December 2016. Retrieved 3 December 2016.
  22. ^ Thomson, Iain. "Virus (cough, cough, Petya) goes postal at FedEx, shares halted". The Register. Archived from the original on 1 July 2017. Retrieved 29 June 2017.
  23. ^ "New Petya Distribution Vectors Bubbling to Surface". Threatpost. 28 June 2017. Archived from the original on 28 June 2017. Retrieved 29 June 2017.
  24. ^ "Deterministic Builds Part One: Cyberwar and Global Compromise | The Tor Blog". blog.torproject.org. Archived from the original on 23 June 2017. Retrieved 11 July 2017.
  25. . Retrieved 11 July 2017.
  26. ^ Magazines, S. P. H. (2007). HWM. SPH Magazines. Retrieved 11 July 2017.

External links