linux-kernel - Re: [patch V4 part 2 10/18] x86/entry/64: Check IF in __preempt_enable

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <87blmt604z.fsf@nanos.tec.linutronix.de>
Date:   Tue, 12 May 2020 10:14:04 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Petr Mladek <pmladek@...e.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Brian Gerst <brgerst@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Will Deacon <will@...nel.org>
Subject: Re: [patch V4 part 2 10/18] x86/entry/64: Check IF in __preempt_enable_notrace() thunk

Steven Rostedt <rostedt@...dmis.org> writes:
> On Tue, 05 May 2020 15:41:22 +0200
> Thomas Gleixner <tglx@...utronix.de> 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/Makefile.build:349: arch/x86/entry/thunk_64.o] Error 1
> make[3]: *** Waiting for unfinished jobs....

Yes I know, but I'm going to drop that patch completely.