From: Kees Cook <keescook@chromium.org>
To: Marco Elver <elver@google.com>
Cc: kernel test robot <lkp@intel.com>,
kbuild-all@lists.01.org,
clang-built-linux <clang-built-linux@googlegroups.com>,
LKML <linux-kernel@vger.kernel.org>,
Dmitry Vyukov <dvyukov@google.com>,
kasan-dev <kasan-dev@googlegroups.com>
Subject: Re: [PATCH v3 4/9] x86/build: Warn on orphan section placement
Date: Mon, 29 Jun 2020 08:26:34 -0700 [thread overview]
Message-ID: <202006290819.955CF6743@keescook> (raw)
In-Reply-To: <CANpmjNMtFbc_jQU6iNfNx-4wwQF4DY3uaOB1dCPZ3dMqXx6smg@mail.gmail.com>
On Mon, Jun 29, 2020 at 04:54:13PM +0200, Marco Elver wrote:
> On Sat, 27 Jun 2020 at 17:44, Kees Cook <keescook@chromium.org> wrote:
> >
> > On Thu, Jun 25, 2020 at 02:36:27AM +0800, kernel test robot wrote:
> > > I love your patch! Perhaps something to improve:
> > > [...]
> > > config: x86_64-randconfig-a012-20200624 (attached as .config)
> >
> > CONFIG_KCSAN=y
> >
> > > compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project 1d4c87335d5236ea1f35937e1014980ba961ae34)
> > > [...]
> > > All warnings (new ones prefixed by >>):
> > >
> > > ld.lld: warning: drivers/built-in.a(mfd/mt6397-irq.o):(.init_array.0) is being placed in '.init_array.0'
> >
> > As far as I can tell, this is a Clang bug. But I don't know the
> > internals here, so I've opened:
> > https://bugs.llvm.org/show_bug.cgi?id=46478
> >
> > and created a work-around patch for the kernel:
>
> Thanks, minor comments below.
>
> With KCSAN this is:
>
> Tested-by: Marco Elver <elver@google.com>
Thanks!
>
>
> > commit 915f2c343e59a14f00c68f4d7afcfdc621de0674
> > Author: Kees Cook <keescook@chromium.org>
> > Date: Sat Jun 27 08:07:54 2020 -0700
> >
> > vmlinux.lds.h: Avoid KCSAN's unwanted sections
>
> Since you found that it's also KASAN, this probably wants updating.
Yeah, I found that while testing the v4 series and updated the patch
there.
> > KCSAN (-fsanitize=thread) produces unwanted[1] .eh_frame and .init_array.*
> > sections. Add them to DISCARDS, except with CONFIG_CONSTRUCTORS, which
> > wants to keep .init_array.* sections.
> >
> > [1] https://bugs.llvm.org/show_bug.cgi?id=46478
> >
> > Signed-off-by: Kees Cook <keescook@chromium.org>
> >
> > diff --git a/arch/x86/Makefile b/arch/x86/Makefile
> > index f8a5b2333729..41c8c73de6c4 100644
> > --- a/arch/x86/Makefile
> > +++ b/arch/x86/Makefile
> > @@ -195,7 +195,9 @@ endif
> > # Workaround for a gcc prelease that unfortunately was shipped in a suse release
> > KBUILD_CFLAGS += -Wno-sign-compare
> > #
> > -KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
> > +KBUILD_AFLAGS += -fno-asynchronous-unwind-tables -fno-unwind-tables
> > +KBUILD_CFLAGS += -fno-asynchronous-unwind-tables -fno-unwind-tables
> > +KBUILD_LDFLAGS += $(call ld-option,--no-ld-generated-unwind-info)
>
> Why are they needed? They are not mentioned in the commit message.
This was a mis-applied chunk (I also noticed this in the v4).
> > +/*
> > + * Clang's -fsanitize=thread produces unwanted sections (.eh_frame
> > + * and .init_array.*), but CONFIG_CONSTRUCTORS wants to keep any
> > + * .init_array.* sections.
> > + * https://bugs.llvm.org/show_bug.cgi?id=46478
> > + */
> > +#if defined(CONFIG_KCSAN) && !defined(CONFIG_CONSTRUCTORS)
>
> CONFIG_KASAN as well?
>
> > +#define KCSAN_DISCARDS \
> > + *(.init_array) *(.init_array.*) \
> > + *(.eh_frame)
> > +#elif defined(CONFIG_KCSAN) && defined(CONFIG_CONSTRUCTORS)
> > +#define KCSAN_DISCARDS \
> > + *(.eh_frame)
> > +#else
> > +#define KCSAN_DISCARDS
> > +#endif
> > +
> > #define DISCARDS \
> > /DISCARD/ : { \
> > EXIT_DISCARDS \
> > EXIT_CALL \
> > + KCSAN_DISCARDS \
>
> Maybe just 'SANITIZER_DISCARDS'?
Sure! I will rename it.
>
> > *(.discard) \
> > *(.discard.*) \
> > *(.modinfo) \
> >
> > --
> > Kees Cook
--
Kees Cook
next prev parent reply other threads:[~2020-06-29 19:04 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-24 1:49 [PATCH v3 0/9] Warn on orphan section placement Kees Cook
2020-06-24 1:49 ` [PATCH v3 1/9] vmlinux.lds.h: Add .gnu.version* to DISCARDS Kees Cook
2020-06-24 1:49 ` [PATCH v3 2/9] vmlinux.lds.h: Add .symtab, .strtab, and .shstrtab to STABS_DEBUG Kees Cook
2020-06-24 15:39 ` Arvind Sankar
2020-06-24 16:16 ` Fangrui Song
2020-06-24 17:11 ` Arvind Sankar
2020-06-24 17:26 ` Fangrui Song
2020-06-24 17:35 ` Arvind Sankar
2020-06-24 1:49 ` [PATCH v3 3/9] efi/libstub: Remove .note.gnu.property Kees Cook
2020-06-24 3:31 ` Fangrui Song
2020-06-24 4:44 ` Kees Cook
2020-06-24 10:43 ` Will Deacon
2020-06-24 10:46 ` Ard Biesheuvel
2020-06-24 11:26 ` Will Deacon
2020-06-24 13:48 ` Dave Martin
2020-06-24 15:26 ` Will Deacon
2020-06-24 16:26 ` Dave Martin
2020-06-24 15:21 ` Kees Cook
2020-06-24 15:31 ` Ard Biesheuvel
2020-06-24 15:45 ` Kees Cook
2020-06-24 15:48 ` Ard Biesheuvel
2020-06-24 16:29 ` Dave Martin
2020-06-24 16:40 ` Ard Biesheuvel
2020-06-24 17:16 ` Dave Martin
2020-06-24 18:23 ` Ard Biesheuvel
2020-06-24 18:57 ` Ard Biesheuvel
2020-06-24 1:49 ` [PATCH v3 4/9] x86/build: Warn on orphan section placement Kees Cook
[not found] ` <202006250240.J1VuMKoC%lkp@intel.com>
2020-06-27 15:44 ` Kees Cook
2020-06-29 14:54 ` Marco Elver
2020-06-29 15:26 ` Kees Cook [this message]
2020-06-24 1:49 ` [PATCH v3 5/9] x86/boot: " Kees Cook
2020-06-24 1:49 ` [PATCH v3 6/9] arm/build: " Kees Cook
2020-06-24 1:49 ` [PATCH v3 7/9] arm/boot: " Kees Cook
2020-06-24 1:49 ` [PATCH v3 8/9] arm64/build: Use common DISCARDS in linker script Kees Cook
2020-06-24 1:49 ` [PATCH v3 9/9] arm64/build: Warn on orphan section placement Kees Cook
2020-06-24 7:57 ` Will Deacon
2020-06-24 15:36 ` Kees Cook
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=202006290819.955CF6743@keescook \
--to=keescook@chromium.org \
--cc=clang-built-linux@googlegroups.com \
--cc=dvyukov@google.com \
--cc=elver@google.com \
--cc=kasan-dev@googlegroups.com \
--cc=kbuild-all@lists.01.org \
--cc=linux-kernel@vger.kernel.org \
--cc=lkp@intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).