linux-kernel - [PATCH v4 00/18] Add static

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Message-Id: <20200501202849.647891881@infradead.org>
Date:   Fri, 01 May 2020 22:28:49 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     x86@...nel.org
Cc:     peterz@...radead.org, linux-kernel@...r.kernel.org,
        rostedt@...dmis.org, mhiramat@...nel.org, bristot@...hat.com,
        jbaron@...mai.com, torvalds@...ux-foundation.org,
        tglx@...utronix.de, mingo@...nel.org, namit@...are.com,
        hpa@...or.com, luto@...nel.org, ard.biesheuvel@...aro.org,
        jpoimboe@...hat.com, pbonzini@...hat.com,
        mathieu.desnoyers@...icios.com
Subject: [PATCH v4 00/18] Add static_call()

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