linux-hardening - Re: [RFC PATCH 14/21] treewide: static_call: Pass call arguments to the macro

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Message-ID: <CABCJKud8vC6RwQLs2YXnZMZaXGNYBEq+sNmOsgGjjAw4MfuZuw@mail.gmail.com>
Date:   Fri, 29 Apr 2022 17:49:21 -0700
From:   Sami Tolvanen <samitolvanen@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>, X86 ML <x86@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Joao Moreira <joao@...rdrivepizza.com>,
        Sedat Dilek <sedat.dilek@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-hardening@...r.kernel.org,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        llvm@...ts.linux.dev
Subject: Re: [RFC PATCH 14/21] treewide: static_call: Pass call arguments to
 the macro

On Fri, Apr 29, 2022 at 4:21 PM Peter Zijlstra <peterz@...radead.org> wrote:
> Can you explain why this is needed? I don't think there are any indirect
> calls to get confused about. That is, if you have STATIC_CALL_INLINE
> then the compiler should be emitting direct calls to the trampoline.

Clang emits an indirect call for ({ &f; })(), which is optimized into
a direct call when possible. Come to think of it, the recent
InstCombine change to the compiler patch should solve this issue. Let
me double check, I'd be more than happy to drop these two patches.

Sami