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In36568732e4, we expanded toolchain.cmake to also define the value for CMAKE_SYSTEM_VERSION, as the cmake documentation states that it must be manually defined when doing cross-compilation [0]: When the CMAKE_SYSTEM_NAME variable is set explicitly to enable cross compiling then the value of CMAKE_SYSTEM_VERSION must also be set explicitly to specify the target system version. However, the fix in36568732e4uses the version of the kernel headers, assuming that would be the oldest kernel we could run on. Yet, this is not the case, because glibc (for example) has fallbacks to support running on kernels older than the headers it was built against. The cmake official wiki [1] additionally states: * CMAKE_SYSTEM_VERSION : optional, version of your target system, not used very much. Folllowed a little bit below, by: * CMAKE_TOOLCHAIN_FILE : absolute or relative path to a cmake script which sets up all the toolchain related variables mentioned above For instance for crosscompiling from Linux to Embedded Linux on PowerPC this file could look like this: # this one is important SET(CMAKE_SYSTEM_NAME Linux) #this one not so much SET(CMAKE_SYSTEM_VERSION 1) [...] Furthermore, using the kernel headers version can be a bit misleading (as it really looks like is is the correct version to use when it is not), while it is obvious that 1 is not really the output of `uname -r` and thus is definitely not misleading. Finally, random searches [2] about CMAKE_SYSTEM_VERSION, mostly only turns up issues related with Windows, Mac-OS, and to a lesser extent, Android (where it is forcibly set to 1), with issues realted to running under just Linux (as opposed to Adnroid) mostly non-existent. Consequently, we revert to using the value that is suggested in the cmake WiKi, i.e. 1, and which is basically what we also used as a workaround in the azure-iot-sdk-c paclkage up untild300b1d3b1. A case were we will need to have a real kernel version, is if we one day have a cmake-based pacakge that builds and installs a kernel module [3], because it will need the _running_ kernel version to install it in /lib/modules/VERSION/, but in that case it will anyway most probably not be the headers version. [0] https://cmake.org/cmake/help/v3.8/variable/CMAKE_SYSTEM_VERSION.html [1] https://gitlab.kitware.com/cmake/community/wikis/doc/cmake/CrossCompiling [2] https://duckduckgo.com/?q=CMAKE_SYSTEM_VERSION [3] https://stackoverflow.com/questions/38205745/cmake-system-version-not-updated-for-new-kernel Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr> Cc: Arnout Vandecappelle <arnout@mind.be> Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com> Cc: Samuel Martin <s.martin49@gmail.com> Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be> Signed-off-by: Peter Korsgaard <peter@korsgaard.com> (cherry picked from commitfc8a5f56b9) Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Buildroot is a simple, efficient and easy-to-use tool to generate embedded Linux systems through cross-compilation. The documentation can be found in docs/manual. You can generate a text document with 'make manual-text' and read output/docs/manual/manual.text. Online documentation can be found at http://buildroot.org/docs.html To build and use the buildroot stuff, do the following: 1) run 'make menuconfig' 2) select the target architecture and the packages you wish to compile 3) run 'make' 4) wait while it compiles 5) find the kernel, bootloader, root filesystem, etc. in output/images You do not need to be root to build or run buildroot. Have fun! Buildroot comes with a basic configuration for a number of boards. Run 'make list-defconfigs' to view the list of provided configurations. Please feed suggestions, bug reports, insults, and bribes back to the buildroot mailing list: buildroot@buildroot.org You can also find us on #buildroot on Freenode IRC. If you would like to contribute patches, please read https://buildroot.org/manual.html#submitting-patches