Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2090231



commit 7a53f408
Author: Peter Zijlstra <peterz@infradead.org>
Date:   Wed, 23 Mar 2022 23:35:01 +0100

    objtool: Fix SLS validation for kcov tail-call replacement

    Since not all compilers have a function attribute to disable KCOV
    instrumentation, objtool can rewrite KCOV instrumentation in noinstr
    functions as per commit:

      f56dae88 ("objtool: Handle __sanitize_cov*() tail calls")

    However, this has subtle interaction with the SLS validation from
    commit:

      1cc1e4c8 ("objtool: Add straight-line-speculation validation")

    In that when a tail-call instrucion is replaced with a RET an
    additional INT3 instruction is also written, but is not represented in
    the decoded instruction stream.

    This then leads to false positive missing INT3 objtool warnings in
    noinstr code.

    Instead of adding additional struct instruction objects, mark the RET
    instruction with retpoline_safe to suppress the warning (since we know
    there really is an INT3).

    Fixes: 1cc1e4c8 ("objtool: Add straight-line-speculation validation")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Link: https://lkml.kernel.org/r/20220323230712.GA8939@worktop.programming.kicks-ass.net



Signed-off-by: Waiman Long <longman@redhat.com>