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

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Date:   Wed, 23 Feb 2022 12:54:14 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Philip Li <philip.li@...el.com>
Cc:     Kalesh Singh <kaleshsingh@...gle.com>,
        kernel test robot <lkp@...el.com>, llvm@...ts.linux.dev,
        kbuild-all@...ts.01.org, will@...nel.org, qperret@...gle.com,
        tabba@...gle.com, surenb@...gle.com, kernel-team@...roid.com,
        Catalin Marinas <catalin.marinas@....com>,
        James Morse <james.morse@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Pasha Tatashin <pasha.tatashin@...een.com>,
        Joey Gouly <joey.gouly@....com>,
        Peter Collingbourne <pcc@...gle.com>,
        Andrew Scull <ascull@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Zenghui Yu <yuzenghui@...wei.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kvmarm@...ts.cs.columbia.edu
Subject: Re: [kbuild-all] Re: [PATCH v2 6/9] KVM: arm64: Detect and handle
 hypervisor stack overflows

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@...el.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@...el.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.

         M.
-- 
Jazz is not dead. It just smells funny...