static_call(), is the idea of static_branch() applied to indirect function calls. Remove a data load (indirection) by modifying the text.
The inline implementation still relies on objtool to generate the .static_call_sites section, mostly because this is a natural place for x86_64 and works for both GCC and LLVM. Other architectures can pick other means if/when they implement the inline patching. The out-of-line (aka. trampoline) variant doesn't require this. Patches go on top of tip/objtool/core. Patches can also be found here: git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git x86/static_call Changes since the last time: - Fixed the inline variant; the previous version relied on the section of symbols to detect the static call sites, but undefined symbols do not have a section, so it basically ended up not patching many sites. IOW inline mostly behaved in the out-of-line variant. - Fixed an issue with modules - Clarified static_cond_call() has 'void' return. - Clarified DEFINE_STATIC_COND_CALL() (ab)use. - Tracing no longer adds an indirect call for !HAVE_STATIC_CALL
