1*43a90889SApple OSS Distributions# XNU Version Number # 2*43a90889SApple OSS Distributions 3*43a90889SApple OSS DistributionsIncorporating the version number into xnu's build. 4*43a90889SApple OSS Distributions 5*43a90889SApple OSS Distributions## Overview 6*43a90889SApple OSS Distributions 7*43a90889SApple OSS DistributionsThe first line of the generated file `$(OBJROOT)/xnuVersion` contains the 8*43a90889SApple OSS Distributionsversion number for the kernel being built. All other instances of the kernel 9*43a90889SApple OSS Distributionsversion in xnu are derived from that file. 10*43a90889SApple OSS Distributions 11*43a90889SApple OSS Distributions## Generating the XNU version number ## 12*43a90889SApple OSS Distributions 13*43a90889SApple OSS DistributionsThe buildsystem (`makedefs/MakeInc.kernel`) generates the `xnuVersion` file by 14*43a90889SApple OSS Distributionsderiving the xnu version from the SDK or KDK that xnu is being built against. 15*43a90889SApple OSS DistributionsThe xnu version number is read from the `CFBundleVersion` property of 16*43a90889SApple OSS Distributionsthe `System/Library/Extensions/System.kext/Info.plist` file in the SDK or KDK. 17*43a90889SApple OSS Distributions 18*43a90889SApple OSS Distributions### Customizing the XNU version number ### 19*43a90889SApple OSS Distributions 20*43a90889SApple OSS DistributionsThe derivation above can be bypassed and the xnu version customized by setting 21*43a90889SApple OSS Distributionsthe `RC_DARWIN_KERNEL_VERSION` variable in the environment or overriding it on 22*43a90889SApple OSS Distributionsthe `make` command line. 23*43a90889SApple OSS Distributions 24*43a90889SApple OSS Distributions 25*43a90889SApple OSS Distributions## Format of the XNU version number ## 26*43a90889SApple OSS Distributions 27*43a90889SApple OSS DistributionsThe format of the version number must conform to the version resource format 28*43a90889SApple OSS Distributionsas described in [TN1132] 29*43a90889SApple OSS Distributions(https://web.archive.org/web/20090330032438/http://developer.apple.com/technotes/tn/tn1132.html). 30*43a90889SApple OSS Distributions 31*43a90889SApple OSS DistributionsIn particular, the string is formatted as: `J[.N[.R[S[L]]]]`, where: 32*43a90889SApple OSS Distributions 33*43a90889SApple OSS Distributions* `J` represents the kernel major version number (integer) 34*43a90889SApple OSS Distributions* `N` represents the kernel minor version number (integer) 35*43a90889SApple OSS Distributions* `R` represents the kernel revision number (integer) 36*43a90889SApple OSS Distributions* `S` represents the kernel build stage (one of `d`, `a`, `b`, or `r`) 37*43a90889SApple OSS Distributions* `L` represents the kernel pre-release level (integer) 38*43a90889SApple OSS Distributions 39*43a90889SApple OSS Distributions## Using the XNU version number ## 40*43a90889SApple OSS Distributions 41*43a90889SApple OSS DistributionsThe correct way to make use of the kernel version within kernel code or a 42*43a90889SApple OSS Distributionskext is to include `<libkern/version.h>`. This header contains defines that 43*43a90889SApple OSS Distributionscan be used for build-time version logic and prototypes for variables that can 44*43a90889SApple OSS Distributionsbe used for run-time version logic. 45*43a90889SApple OSS Distributions 46