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  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]
Date:   Mon, 11 Jan 2021 17:13:16 -0800
From:   Nick Desaulniers <>
To:     Borislav Petkov <>
Cc:     Fāng-ruì Sòng <>,
        Andy Lutomirski <>,
        Thomas Gleixner <>,
        Ingo Molnar <>, Arnd Bergmann <>,
        Josh Poimboeuf <>, X86 ML <>,
        "H. Peter Anvin" <>,
        Nathan Chancellor <>,
        LKML <>,
        clang-built-linux <>
Subject: Re: [PATCH v3] x86/entry: emit a symbol for register restoring thunk

On Mon, Jan 11, 2021 at 5:00 PM Borislav Petkov <> wrote:
> On Mon, Jan 11, 2021 at 04:41:52PM -0800, Fāng-ruì Sòng wrote:
> > To be fair: we cannot use
> Who's "we"?
> > .L-prefixed local because of the objtool limitation.
> What objtool limitation? I thought clang's assembler removes .text which
> objtool uses. It worked fine with GNU as so far.

I don't think we need to completely stop using .L prefixes in the
kernel, just this one location since tracking the control flow seems a
little tricky for objtool. Maybe Josh can clarify more if needed?

> > The LLVM integrated assembler behavior is a good one
> Please explain what "good one" means in that particular context.
> > and binutils global maintainers have agreed so H.J. went ahead and
> > implemented it for GNU as x86.
> But they don't break old behavior, do they? Or are they removing .text
> unconditionally now too?

Unconditionally. See
where that flag was rejected and the optimization was adopted as the
optimization was obvious to GNU binutils developers. So I suspect this
will become a problem for GNU binutils users as well after the latest
release that contains

> > --generate-unused-section-symbols=[yes|no] as an assembler option has
> > been rejected.
> Meaning what exactly? There's no way for clang's integrated assembler to
> even get a cmdline option to not strip .text?

I can clean that up in v5; The section symbols were not generated then
stripped; they were simply never generated.
~Nick Desaulniers

Powered by blists - more mailing lists