Messages in this thread | | | Date | Fri, 01 May 2020 22:28:49 +0200 | From | Peter Zijlstra <> | Subject | [PATCH v4 00/18] Add static_call() |
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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
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