From: Greg Kroah-Hartman <gregkh@linuxfoundation•org>
To: Alexandre Chartre <alexandre.chartre@oracle•com>
Cc: Sasha Levin <sashal@kernel•org>,
linux-arch@vger•kernel.org,
Nicolas Boichat <drinkcat@chromium•org>,
Arnd Bergmann <arnd@arndb•de>,
linux-kbuild@vger•kernel.org,
Peter Zijlstra <peterz@infradead•org>,
Christopher Li <sparse@chrisli•org>,
linux-kernel@vger•kernel.org, stable@vger•kernel.org,
Masahiro Yamada <yamada.masahiro@socionext•com>,
linux-sparse@vger•kernel.org,
Michal Marek <michal.lkml@markovi•net>,
Paul Mackerras <paulus@samba•org>,
Nicholas Piggin <npiggin@gmail•com>,
Thomas Gleixner <tglx@linutronix•de>,
linuxppc-dev@lists•ozlabs.org,
"Naveen N. Rao" <naveen.n.rao@linux•vnet.ibm.com>,
Daniel Axtens <dja@axtens•net>
Subject: Re: [for-stable-4.19 PATCH 1/2] vmlinux.lds.h: Create section for protection against instrumentation
Date: Fri, 19 Mar 2021 12:55:50 +0100 [thread overview]
Message-ID: <YFSRRux3FHJVgWXt@kroah.com> (raw)
In-Reply-To: <b5d3d0ed-953e-083d-15f6-4a1e3ed95428@oracle.com>
On Fri, Mar 19, 2021 at 12:20:22PM +0100, Alexandre Chartre wrote:
>
> On 3/19/21 11:39 AM, Greg Kroah-Hartman wrote:
> > On Fri, Mar 19, 2021 at 07:54:15AM +0800, Nicolas Boichat wrote:
> > > From: Thomas Gleixner <tglx@linutronix•de>
> > >
> > > commit 6553896666433e7efec589838b400a2a652b3ffa upstream.
> > >
> > > Some code pathes, especially the low level entry code, must be protected
> > > against instrumentation for various reasons:
> > >
> > > - Low level entry code can be a fragile beast, especially on x86.
> > >
> > > - With NO_HZ_FULL RCU state needs to be established before using it.
> > >
> > > Having a dedicated section for such code allows to validate with tooling
> > > that no unsafe functions are invoked.
> > >
> > > Add the .noinstr.text section and the noinstr attribute to mark
> > > functions. noinstr implies notrace. Kprobes will gain a section check
> > > later.
> > >
> > > Provide also a set of markers: instrumentation_begin()/end()
> > >
> > > These are used to mark code inside a noinstr function which calls
> > > into regular instrumentable text section as safe.
> > >
> > > The instrumentation markers are only active when CONFIG_DEBUG_ENTRY is
> > > enabled as the end marker emits a NOP to prevent the compiler from merging
> > > the annotation points. This means the objtool verification requires a
> > > kernel compiled with this option.
> > >
> > > Signed-off-by: Thomas Gleixner <tglx@linutronix•de>
> > > Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle•com>
> > > Acked-by: Peter Zijlstra <peterz@infradead•org>
> > > Link: https://lkml.kernel.org/r/20200505134100.075416272@linutronix.de
> > >
> > > [Nicolas: context conflicts in:
> > > arch/powerpc/kernel/vmlinux.lds.S
> > > include/asm-generic/vmlinux.lds.h
> > > include/linux/compiler.h
> > > include/linux/compiler_types.h]
> > > Signed-off-by: Nicolas Boichat <drinkcat@chromium•org>
> >
> > Did you build this on x86?
> >
> > I get the following build error:
> >
> > ld:./arch/x86/kernel/vmlinux.lds:20: syntax error
> >
> > And that line looks like:
> >
> > . = ALIGN(8); *(.text.hot .text.hot.*) *(.text .text.fixup) *(.text.unlikely .text.unlikely.*) *(.text.unknown .text.unknown.*) . = ALIGN(8); __noinstr_text_start = .; *(.__attribute__((noinline)) __attribute__((no_instrument_function)) __attribute((__section__(".noinstr.text"))).text) __noinstr_text_end = .; *(.text..refcount) *(.ref.text) *(.meminit.text*) *(.memexit.text*)
> >
>
> In the NOINSTR_TEXT macro, noinstr is expanded with the value of the noinstr
> macro from linux/compiler_types.h while it shouldn't.
>
> The problem is possibly that the noinstr macro is defined for assembly. Make
> sure that the macro is not defined for assembly e.g.:
>
> #ifndef __ASSEMBLY__
>
> /* Section for code which can't be instrumented at all */
> #define noinstr \
> noinline notrace __attribute((__section__(".noinstr.text")))
>
> #endif
This implies that the backport is incorrect, so I'll wait for an updated
version...
thanks,
greg k-h
next prev parent reply other threads:[~2021-03-19 11:56 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-18 23:54 [for-stable-4.19 PATCH 0/2] Backport patches to fix KASAN+LKDTM with recent clang on ARM64 Nicolas Boichat
2021-03-18 23:54 ` [for-stable-4.19 PATCH 1/2] vmlinux.lds.h: Create section for protection against instrumentation Nicolas Boichat
2021-03-19 10:39 ` Greg Kroah-Hartman
2021-03-19 11:20 ` Alexandre Chartre
2021-03-19 11:55 ` Greg Kroah-Hartman [this message]
2021-03-19 22:48 ` Nicolas Boichat
2021-03-19 10:30 ` [for-stable-4.19 PATCH 0/2] Backport patches to fix KASAN+LKDTM with recent clang on ARM64 Greg Kroah-Hartman
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