linux-kernel - [PATCH 0/2] bpf: Yet another approach to fix the BPF dispatcher thing

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Message-ID: <20221103120012.717020618@infradead.org>
Date:   Thu, 03 Nov 2022 13:00:12 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     olsajiri@...il.com, ast@...nel.org, daniel@...earbox.net
Cc:     linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        bpf@...r.kernel.org, peterz@...radead.org, bjorn@...nel.org,
        toke@...hat.com, David.Laight@...lab.com, rostedt@...dmis.org
Subject: [PATCH 0/2] bpf: Yet another approach to fix the BPF dispatcher thing

Hi!

Even thought the __attribute__((patchable_function_entry())) solution to the
BPF dispatcher woes works, it turns out to not be supported by the whole range
of ageing compilers we support. Specifically this attribute seems to be GCC-8
and later.

This is another approach -- using static_call() to rewrite the dispatcher
function. I've compile tested this on:

  x86_64  (inline static-call support)
  i386    (out-of-line static-call support)
  aargh64 (no static-call support)

A previous version was tested and found working by Bjorn.

It is split in two patches; first reverting the current approach and then
introducing the new for ease of review.