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Date: Thu, 4 Jun 2020 17:20:48 +0300
From: Alexander Popov <alex.popov@...ux.com>
To: Jann Horn <jannh@...gle.com>, Will Deacon <will@...nel.org>
Cc: Kees Cook <keescook@...omium.org>, Emese Revfy <re.emese@...il.com>,
Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
Masahiro Yamada <masahiroy@...nel.org>,
Michal Marek <michal.lkml@...kovi.net>,
Andrew Morton <akpm@...ux-foundation.org>,
Masahiro Yamada <yamada.masahiro@...ionext.com>,
Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
Luis Chamberlain <mcgrof@...nel.org>, Jessica Yu <jeyu@...nel.org>,
Sven Schnelle <svens@...ckframe.org>, Iurii Zaikin <yzaikin@...gle.com>,
Catalin Marinas <catalin.marinas@....com>,
Vincenzo Frascino <vincenzo.frascino@....com>,
Thomas Gleixner <tglx@...utronix.de>, Peter Collingbourne <pcc@...gle.com>,
Naohiro Aota <naohiro.aota@....com>, Alexander Monakov <amonakov@...ras.ru>,
Mathias Krause <minipli@...glemail.com>, PaX Team <pageexec@...email.hu>,
Brad Spengler <spender@...ecurity.net>, Laura Abbott <labbott@...hat.com>,
Florian Weimer <fweimer@...hat.com>,
Kernel Hardening <kernel-hardening@...ts.openwall.com>,
linux-kbuild@...r.kernel.org, the arch/x86 maintainers <x86@...nel.org>,
Linux ARM <linux-arm-kernel@...ts.infradead.org>,
kernel list <linux-kernel@...r.kernel.org>, gcc@....gnu.org,
notify@...nel.org
Subject: Re: [PATCH 5/5] gcc-plugins/stackleak: Don't instrument
vgettimeofday.c in arm64 VDSO
On 04.06.2020 17:14, Jann Horn wrote:
> On Thu, Jun 4, 2020 at 3:58 PM Will Deacon <will@...nel.org> wrote:
>> On Thu, Jun 04, 2020 at 04:49:57PM +0300, Alexander Popov wrote:
>>> Don't try instrumenting functions in arch/arm64/kernel/vdso/vgettimeofday.c.
>>> Otherwise that can cause issues if the cleanup pass of stackleak gcc plugin
>>> is disabled.
>>>
>>> Signed-off-by: Alexander Popov <alex.popov@...ux.com>
>>> ---
>>> arch/arm64/kernel/vdso/Makefile | 3 ++-
>>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile
>>> index 3862cad2410c..9b84cafbd2da 100644
>>> --- a/arch/arm64/kernel/vdso/Makefile
>>> +++ b/arch/arm64/kernel/vdso/Makefile
>>> @@ -32,7 +32,8 @@ UBSAN_SANITIZE := n
>>> OBJECT_FILES_NON_STANDARD := y
>>> KCOV_INSTRUMENT := n
>>>
>>> -CFLAGS_vgettimeofday.o = -O2 -mcmodel=tiny -fasynchronous-unwind-tables
>>> +CFLAGS_vgettimeofday.o = -O2 -mcmodel=tiny -fasynchronous-unwind-tables \
>>> + $(DISABLE_STACKLEAK_PLUGIN)
>>
>> I can pick this one up via arm64, thanks. Are there any other plugins we
>> should be wary of?
I can't tell exactly. I'm sure Kees has the whole picture.
>> It looks like x86 filters out $(GCC_PLUGINS_CFLAGS)
>> when building the vDSO.
Yes, that's why building x86 vDSO doesn't need $(DISABLE_STACKLEAK_PLUGIN).
> Maybe at some point we should replace exclusions based on
> GCC_PLUGINS_CFLAGS and KASAN_SANITIZE and UBSAN_SANITIZE and
> OBJECT_FILES_NON_STANDARD and so on with something more generic...
> something that says "this file will not be built into the normal
> kernel, it contains code that runs in realmode / userspace / some
> similarly weird context, and none of our instrumentation
> infrastructure is available there"...
Good idea. I would also add 'notrace' to that list.
Best regards,
Alexander
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