From: "H.J. Lu" <hjl.tools@gmail.com>
To: Kees Cook <keescook@chromium.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Thomas Lendacky <Thomas.Lendacky@amd.com>,
Sami Tolvanen <samitolvanen@google.com>,
Heiko Carstens <heiko.carstens@de.ibm.com>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H . Peter Anvin" <hpa@zytor.com>,
"the arch/x86 maintainers" <x86@kernel.org>,
Yu-cheng Yu <yu-cheng.yu@intel.com>
Subject: Re: [PATCH] x86: Don't discard .exit.text and .exit.data at link-time
Date: Thu, 30 Jan 2020 12:06:06 -0800 [thread overview]
Message-ID: <CAMe9rOp1SJvsjSMtDFi4HWKPpu2eePCDiedTPAndUEL5-HSU1w@mail.gmail.com> (raw)
In-Reply-To: <202001301152.DF108B6CC@keescook>
On Thu, Jan 30, 2020 at 11:58 AM Kees Cook <keescook@chromium.org> wrote:
>
> On Thu, Jan 30, 2020 at 11:45:15AM -0800, H.J. Lu wrote:
> > On Thu, Jan 30, 2020 at 11:40 AM Kees Cook <keescook@chromium.org> wrote:
> > >
> > > On Thu, Jan 30, 2020 at 10:00:48AM -0800, H.J. Lu wrote:
> > > > Since .exit.text and .exit.data sections are discarded at runtime, we
> > > > should undefine EXIT_TEXT and EXIT_DATA to exclude .exit.text and
> > > > .exit.data sections from default discarded sections.
> > >
> > > This is just a correctness fix, yes? The EXIT_TEXT and EXIT_DATA were
> > > already included before the /DISCARD/ section here, so there's no
> > > behavioral change with this patch, correct?
> >
> > That is correct. I was confused by EXIT_TEXT and EXIT_DATA in generic
> > DISCARDS. My patch just makes it more explicit.
>
> Okay, so to that end and because this isn't arch-specific, I'd like to
> see this be a behavioral flag, and then the generic DISCARDS macro can
> be adjusted. This lets all architectures implement this without having
> to scatter undef/define lines in each arch.
>
> Something like this:
>
> diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> index e00f41aa8ec4..f242d3b4814d 100644
> --- a/include/asm-generic/vmlinux.lds.h
> +++ b/include/asm-generic/vmlinux.lds.h
> @@ -894,11 +894,17 @@
> * section definitions so that such archs put those in earlier section
> * definitions.
> */
> -#define DISCARDS \
> - /DISCARD/ : { \
> +#ifdef RUNTIME_DISCARD_EXIT
> +#define EXIT_DISCARDS
> +#else
> +#define EXIT_DISCARDS \
> EXIT_TEXT \
> EXIT_DATA \
> - EXIT_CALL \
> + EXIT_CALL
> +#endif
> +#define DISCARDS \
> + /DISCARD/ : { \
> + EXIT_DISCARDS \
> *(.discard) \
> *(.discard.*) \
> *(.modinfo) \
>
> Then x86 and all other architectures that do this can just use
> #define RUNTIME_DISCARD_EXIT
> at the top (like EMITS_PT_NOTE, etc).
>
It should work.
Thanks.
--
H.J.
next prev parent reply other threads:[~2020-01-30 20:06 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-30 18:00 [PATCH] x86: Don't discard .exit.text and .exit.data at link-time H.J. Lu
2020-01-30 19:40 ` Kees Cook
2020-01-30 19:45 ` H.J. Lu
2020-01-30 19:58 ` Kees Cook
2020-01-30 20:06 ` H.J. Lu [this message]
2020-01-30 20:47 ` [PATCH] Add RUNTIME_DISCARD_EXIT to generic DISCARDS H.J. Lu
2020-01-30 22:04 ` Kees Cook
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