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Date:   Mon, 11 May 2020 21:51:08 -0400
From:   Steven Rostedt <>
To:     Thomas Gleixner <>
Cc:     LKML <>,,
        "Paul E. McKenney" <>,
        Andy Lutomirski <>,
        Alexandre Chartre <>,
        Frederic Weisbecker <>,
        Paolo Bonzini <>,
        Sean Christopherson <>,
        Masami Hiramatsu <>,
        Petr Mladek <>,
        Joel Fernandes <>,
        Boris Ostrovsky <>,
        Juergen Gross <>,
        Brian Gerst <>,
        Mathieu Desnoyers <>,
        Josh Poimboeuf <>,
        Will Deacon <>
Subject: Re: [patch V4 part 2 10/18] x86/entry/64: Check IF in
 __preempt_enable_notrace() thunk

On Tue, 05 May 2020 15:41:22 +0200
Thomas Gleixner <> wrote:

> The preempt_enable_notrace() ASM thunk is called from tracing, entry code
> RCU and other places which are already in or going to be in the noinstr
> section which protects sensitve code from being instrumented.
> Calls out of these sections happen with interrupts disabled, which is
> handled in C code, but the push regs, call, pop regs sequence can be
> completely avoided in this case.
> This is also a preparatory step for annotating the call from the thunk to
> preempt_enable_notrace() safe from a noinstr section.

BTW, after applying this patch, I get the following error:

/work/git/linux-test.git/arch/x86/entry/thunk_64.S: Assembler messages:
/work/git/linux-test.git/arch/x86/entry/thunk_64.S:67: Error: invalid operands (*UND* and *UND* sections) for `+'
/work/git/linux-test.git/arch/x86/entry/thunk_64.S:67: Error: invalid operands (*UND* and *ABS* sections) for `/'
make[3]: *** [/work/git/linux-test.git/scripts/ arch/x86/entry/thunk_64.o] Error 1
make[3]: *** Waiting for unfinished jobs....

Config attached.

-- Steve

Download attachment "config.gz" of type "application/gzip" (34653 bytes)

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