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

["Chen, Rong A" <rong.a.chen@intel.com>]

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?

Best Regards,
Rong Chen