From: Kees Cook <keescook@chromium.org>
To: Laura Abbott <labbott@redhat.com>
Cc: "kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>,
Arnd Bergmann <arnd@arndb.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
"David S. Miller" <davem@davemloft.net>,
Mauro Carvalho Chehab <mchehab@osg.samsung.com>,
Jiri Slaby <jslaby@suse.cz>, Guenter Roeck <linux@roeck-us.net>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 3/5] lkdtm: add function for testing .rodata section
Date: Wed, 8 Jun 2016 14:26:56 -0700 [thread overview]
Message-ID: <CAGXu5jJTx3gzzXSNK5x+ui0x7kGhvrV8vhKVoc33T2W3h4T5XQ@mail.gmail.com> (raw)
In-Reply-To: <CAGXu5jKRW1T6uR1ax7Oah_-nHCayALJ-DWj=MMoXwvdZvAfV-w@mail.gmail.com>
On Wed, Jun 8, 2016 at 8:46 AM, Kees Cook <keescook@chromium.org> wrote:
> On Tue, Jun 7, 2016 at 6:02 PM, Laura Abbott <labbott@redhat.com> wrote:
>> On 06/07/2016 02:57 PM, Kees Cook wrote:
>>>
>>> This adds a function that lives in the .rodata section. The section
>>> flags are corrected using objcopy since there is no way with gcc to
>>> declare section flags in an architecture-agnostic way.
>>>
>>
>> Permit me to be the bearer of bad architecture news once again. With
>> arm64 cross compiler (both Fedora 6.1.1 and Linaro 5.1)
>>
>> CC drivers/misc/lkdtm_rodata.o
>> OBJCOPY drivers/misc/lkdtm_rodata_objcopy.o
>> LD drivers/misc/lkdtm.o
>> drivers/misc/lkdtm_rodata_objcopy.o: file not recognized: File format not
>> recognized
>> scripts/Makefile.build:423: recipe for target 'drivers/misc/lkdtm.o' failed
>> make[2]: *** [drivers/misc/lkdtm.o] Error 1
>> scripts/Makefile.build:440: recipe for target 'drivers/misc' failed
>> make[1]: *** [drivers/misc] Error 2
>> Makefile:985: recipe for target 'drivers' failed
>> make: *** [drivers] Error 2
>>
>>
>> As far as I can tell this is because arm64 defines OBJCOPYFLAGS and they get
>> propagated to objcopy
>>
>> aarch64-linux-gnu-objcopy -O binary -R .note -R .note.gnu.build-id -R
>> .comment
>> -S --set-section-flags .text=alloc,readonly
>> --rename-section .text=.rodata drivers/misc/lkdtm_rodata.o
>> drivers/misc/lkdtm_rodata_objcopy.o
>>
>> vs x86
>>
>> objcopy --set-section-flags .text=alloc,readonly --rename-section
>> .text=.rodata
>> drivers/misc/lkdtm_rodata.o drivers/misc/lkdtm_rodata_objcopy.o
>>
>>
>> specifically it's the -O binary that seems to break things, the same failure
>> happens on x86 as well with the the same commands. It works if I clear out
>> the OBJCOPYFLAGS variable first but I don't think that's the correct way to
>> fix this.
>>
>> Thanks,
>> Laura
>>
>>
>>> Signed-off-by: Kees Cook <keescook@chromium.org>
>>> ---
>>> drivers/misc/Makefile | 7 +++++++
>>> drivers/misc/lkdtm.h | 6 ++++++
>>> drivers/misc/lkdtm_core.c | 24 +++++++++++++++++-------
>>> drivers/misc/lkdtm_rodata.c | 10 ++++++++++
>>> 4 files changed, 40 insertions(+), 7 deletions(-)
>>> create mode 100644 drivers/misc/lkdtm.h
>>> create mode 100644 drivers/misc/lkdtm_rodata.c
>>>
>>> diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
>>> index c3cb6ad8cc37..b2d3d68dfa22 100644
>>> --- a/drivers/misc/Makefile
>>> +++ b/drivers/misc/Makefile
>>> @@ -59,3 +59,10 @@ obj-$(CONFIG_CXL_BASE) += cxl/
>>> obj-$(CONFIG_PANEL) += panel.o
>>>
>>> lkdtm-$(CONFIG_LKDTM) += lkdtm_core.o
>>> +lkdtm-$(CONFIG_LKDTM) += lkdtm_rodata_objcopy.o
>>> +
If I add:
OBJCOPYFLAGS :=
here, it seems to fix things...
>>> +OBJCOPYFLAGS_lkdtm_rodata_objcopy.o := \
>>> + --set-section-flags .text=alloc,readonly \
>>> + --rename-section .text=.rodata
>>> +$(obj)/lkdtm_rodata_objcopy.o: $(obj)/lkdtm_rodata.o
>>> + $(call if_changed,objcopy)
>
> Uhhhh... How is arm64 injecting those extra flags? OBJCOPYFLAGS is
> being set with := here?
>
> In related news I need to figure out how to get my cross-compiler
> builds more well scripted...
>
> -Kees
>
> --
> Kees Cook
> Chrome OS & Brillo Security
--
Kees Cook
Chrome OS & Brillo Security
next prev parent reply other threads:[~2016-06-08 21:27 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-07 21:57 [PATCH 0/5] lkdtm: add usercopy and rodata, fix atomic Kees Cook
2016-06-07 21:57 ` [PATCH 1/5] lkdtm: split build into multiple source files Kees Cook
2016-06-07 21:57 ` [PATCH 2/5] lkdtm: clean up after rename Kees Cook
2016-06-07 21:57 ` [PATCH 3/5] lkdtm: add function for testing .rodata section Kees Cook
2016-06-08 1:02 ` Laura Abbott
2016-06-08 15:46 ` Kees Cook
2016-06-08 16:15 ` Laura Abbott
2016-06-08 21:26 ` Kees Cook [this message]
2016-06-10 1:14 ` Laura Abbott
[not found] ` <87h9b4oebf.fsf@concordia.ellerman.id.au>
2016-08-01 19:45 ` Linker segfault on powerpc when CONFIG_LKDTM=y (was Re: [kernel-hardening] [PATCH 3/5] lkdtm: add function for testing .rodata section) Kees Cook
2016-08-02 3:12 ` [kernel-hardening] " Michael Ellerman
2016-08-02 19:12 ` Kees Cook
2016-08-03 4:46 ` Michael Ellerman
2016-06-07 21:57 ` [PATCH 4/5] lkdtm: add usercopy tests Kees Cook
2016-06-07 23:36 ` kbuild test robot
2016-06-08 0:07 ` kbuild test robot
2016-06-07 21:57 ` [PATCH 5/5] lkdtm: split atomic test into over and underflow Kees Cook
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