1*5e3eaea3SApple OSS Distributions# XNU Version Number # 2*5e3eaea3SApple OSS Distributions 3*5e3eaea3SApple OSS DistributionsThe first line of the generated file `$(OBJROOT)/xnuVersion` contains the 4*5e3eaea3SApple OSS Distributionsversion number for the kernel being built. All other instances of the kernel 5*5e3eaea3SApple OSS Distributionsversion in xnu are derived from that file. 6*5e3eaea3SApple OSS Distributions 7*5e3eaea3SApple OSS Distributions## Generating the XNU version number ## 8*5e3eaea3SApple OSS Distributions 9*5e3eaea3SApple OSS DistributionsThe buildsystem (`makedefs/MakeInc.kernel`) generates the `xnuVersion` file by 10*5e3eaea3SApple OSS Distributionsderiving the xnu version from the SDK or KDK that xnu is being built against. 11*5e3eaea3SApple OSS DistributionsThe xnu version number is read from the `CFBundleVersion` property of 12*5e3eaea3SApple OSS Distributionsthe `System/Library/Extensions/System.kext/Info.plist` file in the SDK or KDK. 13*5e3eaea3SApple OSS Distributions 14*5e3eaea3SApple OSS Distributions### Customizing the XNU version number ### 15*5e3eaea3SApple OSS Distributions 16*5e3eaea3SApple OSS DistributionsThe derivation above can be bypassed and the xnu version customized by setting 17*5e3eaea3SApple OSS Distributionsthe `RC_DARWIN_KERNEL_VERSION` variable in the environment or overriding it on 18*5e3eaea3SApple OSS Distributionsthe `make` command line. 19*5e3eaea3SApple OSS Distributions 20*5e3eaea3SApple OSS Distributions 21*5e3eaea3SApple OSS Distributions## Format of the XNU version number ## 22*5e3eaea3SApple OSS Distributions 23*5e3eaea3SApple OSS DistributionsThe format of the version number must conform to the version resource format 24*5e3eaea3SApple OSS Distributionsas described in [TN1132] 25*5e3eaea3SApple OSS Distributions(https://web.archive.org/web/20090330032438/http://developer.apple.com/technotes/tn/tn1132.html). 26*5e3eaea3SApple OSS Distributions 27*5e3eaea3SApple OSS DistributionsIn particular, the string is formatted as: `J[.N[.R[S[L]]]]`, where: 28*5e3eaea3SApple OSS Distributions 29*5e3eaea3SApple OSS Distributions* `J` represents the kernel major version number (integer) 30*5e3eaea3SApple OSS Distributions* `N` represents the kernel minor version number (integer) 31*5e3eaea3SApple OSS Distributions* `R` represents the kernel revision number (integer) 32*5e3eaea3SApple OSS Distributions* `S` represents the kernel build stage (one of `d`, `a`, `b`, or `r`) 33*5e3eaea3SApple OSS Distributions* `L` represents the kernel pre-release level (integer) 34*5e3eaea3SApple OSS Distributions 35*5e3eaea3SApple OSS Distributions## Using the XNU version number ## 36*5e3eaea3SApple OSS Distributions 37*5e3eaea3SApple OSS DistributionsThe correct way to make use of the kernel version within kernel code or a 38*5e3eaea3SApple OSS Distributionskext is to include `<libkern/version.h>`. This header contains defines that 39*5e3eaea3SApple OSS Distributionscan be used for build-time version logic and prototypes for variables that can 40*5e3eaea3SApple OSS Distributionsbe used for run-time version logic. 41*5e3eaea3SApple OSS Distributions 42