Change Details

While cross-compiling Linux kernel tools with Clang on ArchLinux, it was revealed the sysroot and triplet are not properly detected and instead of fixing the root cause in Clang, kernel developers started doing workarounds [1] upon workarounds [2] in the kernel build to be able to pass a working sysroot and triplet during Clang invocation. To give a concrete example, ArchLinux installs its cross-compliation sysroot in /usr/aarch64-linux-gnu for triplet aarch64-linux-gnu. This causes two problems which this commit fixes: 1. The triplet results in an Unknown OS & Unknown distro. To fix this error, we call Triplet::normalize() which does the following transform aarch64-linux-gnu -> aarch64-unknown-linux-gnu, then the OS & Distro are properly detected. 2. The sysroot under /usr/<triplet> itself is not properly detected in Linux::computeSysRoot() so we add a relative path to the ArchLinux installed GCC toolchain. Fixing these two bugs allows to significantly clean up the kernel build as well as fix the cross-compilation detection on ArchLinux. [1] https://github.com/torvalds/linux/commit/cebdb7374577ac6e14afb11311af8c2c44a259fa [2] https://github.com/torvalds/linux/commit/7fd9fd46a459272e641be78c1cc36baab1921fa1

While cross-compiling Linux kernel tools with Clang on ArchLinux, it was revealed the sysroot is not properly detected and instead of fixing the root cause in Clang, kernel developers started doing workarounds [1] upon workarounds [2] in the kernel build to be able to pass a working sysroot during Clang invocation. To give a concrete example, ArchLinux installs its cross-compliation sysroot in /usr/aarch64-linux-gnu for triplet aarch64-linux-gnu. The sysroot under is not properly detected in Linux::computeSysRoot() so we add a relative path to the ArchLinux installed GCC toolchain. Fixing this bug allows to significantly clean up the kernel build as well as to fix the cross-compilation detection on ArchLinux. [1] https://github.com/torvalds/linux/commit/cebdb7374577ac6e14afb11311af8c2c44a259fa [2] https://github.com/torvalds/linux/commit/7fd9fd46a459272e641be78c1cc36baab1921fa1

While cross-compiling Linux kernel tools with Clang on ArchLinux, it was revealed the sysroot and triplet areis not properly detected andnd instead of fixing instead of fixing the root cause in Clang, kernel developers started doing workarounds [1] doing workarounds [1] upon workarounds [2] in the kernel build to be able to pass a working able to pass a working sysroot and triplet during Clang invocation. To give a concrete example, ArchLinux installs its cross-compliation sysroot in /usr/aarch64-linux-gnu for triplet aarch64-linux-gnu. This causes two problems which this commit fixes: 1. The triplet results in an Unknown OS & Unknown distro. To fix this error, we call Triplet::normalize() which does the following transform aarch64-linux-gnu -> aarch64-unknown-linux-gnu, then the OS & Distro are properly detected. 2. The sysroot under /usr/<triplet> itself is not properly detected in Linux::computeSysRoot() so we add a relative path to the ArchLinuxe sysroot under is not properly detected in Linux::computeSysRoot() so we add a relative path to the ArchLinux installed GCC toolchain. Fixing these twois bugs allows to significantly clean up the kernel build as well build as well asas to fix the cross-compilation detection on ArchLinux. [1] https://github.com/torvalds/linux/commit/cebdb7374577ac6e14afb11311af8c2c44a259fa [2] https://github.com/torvalds/linux/commit/7fd9fd46a459272e641be78c1cc36baab1921fa1