Re: [kbuild-all] Re: [PATCH v2 6/9] KVM: arm64: Detect and handle hypervisor stack overflows

Kalesh Singh
2022-02-25T03:12:13Z

On Thu, Feb 24, 2022 at 6:12 PM Chen, Rong A <rong.a.chen@intel.com> wrote:
>
>
>
> On 2/24/2022 6:39 PM, Marc Zyngier wrote:
> > On 2022-02-23 12:56, Ard Biesheuvel wrote:
> >> On Wed, 23 Feb 2022 at 13:54, Marc Zyngier <maz@kernel.org> wrote:
> >>>
> >>> On 2022-02-23 12:34, Philip Li wrote:
> >>> > On Wed, Feb 23, 2022 at 09:16:59AM +0000, Marc Zyngier wrote:
> >>> >> On Wed, 23 Feb 2022 09:05:18 +0000,
> >>> >> kernel test robot <lkp@intel.com> wrote:
> >>> >> >
> >>> >> > Hi Kalesh,
> >>> >> >
> >>> >> > Thank you for the patch! Perhaps something to improve:
> >>> >> >
> >>> >> > [auto build test WARNING on
> >>> cfb92440ee71adcc2105b0890bb01ac3cddb8507]
> >>> >> >
> >>> >> > url:
> >>> https://github.com/0day-ci/linux/commits/Kalesh-Singh/KVM-arm64-Hypervisor-stack-enhancements/20220223-010522
> >>>
> >>> >> > base: cfb92440ee71adcc2105b0890bb01ac3cddb8507
> >>> >> > config: arm64-randconfig-r011-20220221
> >>> (https://download.01.org/0day-ci/archive/20220223/202202231727.L621fVgD-lkp@intel.com/config)
> >>>
> >>> >> > compiler: clang version 15.0.0
> >>> (https://github.com/llvm/llvm-project
> >>> d271fc04d5b97b12e6b797c6067d3c96a8d7470e)
> >>> >> > reproduce (this is a W=1 build):
> >>> >> > wget
> >>> https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross
> >>> -O ~/bin/make.cross
> >>> >> > chmod +x ~/bin/make.cross
> >>> >> > # install arm64 cross compiling tool for clang build
> >>> >> > # apt-get install binutils-aarch64-linux-gnu
> >>> >> > #
> >>> https://github.com/0day-ci/linux/commit/7fe99fd40f7c4b2973218045ca5b9c9160524db1
> >>>
> >>> >> > git remote add linux-review
> >>> https://github.com/0day-ci/linux
> >>> >> > git fetch --no-tags linux-review
> >>> Kalesh-Singh/KVM-arm64-Hypervisor-stack-enhancements/20220223-010522
> >>> >> > git checkout 7fe99fd40f7c4b2973218045ca5b9c9160524db1
> >>> >> > # save the config file to linux build tree
> >>> >> > mkdir build_dir
> >>> >> > COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang
> >>> make.cross W=1 O=build_dir ARCH=arm64 SHELL=/bin/bash arch/arm64/
> >>> >> >
> >>> >> > If you fix the issue, kindly add following tag as appropriate
> >>> >> > Reported-by: kernel test robot <lkp@intel.com>
> >>> >> >
> >>> >> > All warnings (new ones prefixed by >>):
> >>> >> >
> >>> >> > include/linux/stddef.h:8:14: note: expanded from macro 'NULL'
> >>> >> > #define NULL ((void *)0)
> >>> >> > ^~~~~~~~~~~
> >>> >> > arch/arm64/kvm/hyp/nvhe/switch.c:200:27: warning: initializer
> >>> overrides prior initialization of this subobject
> >>> [-Winitializer-overrides]
> >>> >> > [ESR_ELx_EC_FP_ASIMD] = kvm_hyp_handle_fpsimd,
> >>> >> > ^~~~~~~~~~~~~~~~~~~~~
> >>> >> > arch/arm64/kvm/hyp/nvhe/switch.c:196:28: note: previous
> >>> initialization is here
> >>> >> > [0 ... ESR_ELx_EC_MAX] = NULL,
> >>> >> > ^~~~
> >>> >> > include/linux/stddef.h:8:14: note: expanded from macro 'NULL'
> >>> >> > #define NULL ((void *)0)
> >>> >> > ^~~~~~~~~~~
> >>> >>
> >>> >> Kalesh, please ignore this nonsense. There may be things to improve,
> >>> >> but this is *NOT* one of them.
> >>> >>
> >>> >> These reports are pretty useless, and just lead people to ignore real
> >>> >> bug reports.
> >>> >
> >>> > Hi Kalesh, sorry there're some irrelevant issues mixed in the report,
> >>> > kindly ignore them. And the valuable ones are the new ones that
> >>> > prefixed by >>, as the below one in original report.
> >>> >
> >>> >>> arch/arm64/kvm/hyp/nvhe/switch.c:372:17: warning: no previous
> >>> >>> prototype for function 'hyp_panic_bad_stack' [-Wmissing-prototypes]
> >>> > void __noreturn hyp_panic_bad_stack(void)
> >>> > ^
> >>>
> >>> This is only called from assembly code, so a prototype wouldn't bring
> >>> much.
> >>>
> >>
> >> Should probably be marked as 'asmlinkage' then. I've suggested many
> >> times already that this bogus diagnostic should either be disabled, or
> >> disregard 'asmlinkage' symbols.
> >
> > Yes, asmlinkage is definitely missing.
> >
> > But it is pretty obvious that the robot people aren't interested in
> > fixing this particular issue, given how long we have been suggesting
> > this...
> >
> > M.
>
> Hi Marc, Ard,
>
> We have ignored the warning related to asmlinkage according to the below
> advice:
>
> https://lore.kernel.org/lkml/CAMj1kXHrRYagSVniSetHdG15rkQS+fm4zVOtN=Zda3W0QaEoJA@mail.gmail.com/
>
> do you want the bot ignore such warning if asmlinkage not specified?

Hi Rong,

I have added asmlinkage to the functions without a prototype in later
versions of the patch.

Perhaps the report should be updated to say "functions only called
from assembly code should be annotated with the asmlinkage attribute"
if the error is a missing prototype

Thanks,
Kalesh
>
> Best Regards,
> Rong Chen
>
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