Re: [linux-stable-rc:linux-4.14.y 8552/9999] arch/arm64/kernel/cpu_errata.c:91:23: error: '__bp_harden_hyp_vecs_start' undeclared; did you mean

[Catalin Marinas <catalin.marinas@arm.com>]

[-- Attachment #1: Type: text/plain, Size: 4246 bytes --]

On Thu, Mar 04, 2021 at 06:09:57PM +0000, Catalin Marinas wrote:
> On Tue, Mar 02, 2021 at 06:57:05AM +0800, kernel test robot wrote:
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git linux-4.14.y
> > head:   e1f7d50ae3a3ec342e87a9b1ce6787bfb8b3c08b
> > commit: 3e91f3eacc91d9d6116ed56ea339f858958ba3ee [8552/9999] arm64: Always enable spectre-v2 vulnerability detection
> > config: arm64-randconfig-c003-20210301 (attached as .config)
> > compiler: aarch64-linux-gcc (GCC) 7.5.0
> > 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
> >         # https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git/commit/?id=3e91f3eacc91d9d6116ed56ea339f858958ba3ee
> >         git remote add linux-stable-rc https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git
> >         git fetch --no-tags linux-stable-rc linux-4.14.y
> >         git checkout 3e91f3eacc91d9d6116ed56ea339f858958ba3ee
> >         # save the attached .config to linux build tree
> >         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-7.5.0 make.cross ARCH=arm64 
> > 
> > If you fix the issue, kindly add following tag as appropriate
> > Reported-by: kernel test robot <lkp@intel.com>
> > 
> > All errors (new ones prefixed by >>):
> > 
> >    In file included from arch/arm64/include/asm/thread_info.h:30:0,
> >                     from include/linux/thread_info.h:38,
> >                     from include/asm-generic/preempt.h:5,
> >                     from ./arch/arm64/include/generated/asm/preempt.h:1,
> >                     from include/linux/preempt.h:81,
> >                     from include/linux/radix-tree.h:28,
> >                     from include/linux/idr.h:15,
> >                     from include/linux/kernfs.h:14,
> >                     from include/linux/sysfs.h:16,
> >                     from include/linux/kobject.h:21,
> >                     from include/linux/device.h:17,
> >                     from include/linux/node.h:18,
> >                     from include/linux/cpu.h:17,
> >                     from arch/arm64/include/asm/cpu.h:19,
> >                     from arch/arm64/kernel/cpu_errata.c:22:
> >    arch/arm64/kernel/cpu_errata.c: In function '__copy_hyp_vect_bpi':
> > >> arch/arm64/kernel/cpu_errata.c:91:23: error: '__bp_harden_hyp_vecs_start' undeclared (first use in this function); did you mean 'hyp_vecs_start'?
> >      void *dst = lm_alias(__bp_harden_hyp_vecs_start + slot * SZ_2K);
> 
> It looks like commit 8c1e3d2bb44c ("arm64: Always enable spectre-v2
> vulnerability detection") was backported from 5.2 to 4.14 but the
> context for the __bp_harden_hyp_vecs_start declaration/definition is
> missing.
> 
> In 4.17, commit 4340ba80bd3a ("arm64: KVM: Move BP hardening vectors
> into .hyp.text section") moved the __bp_harden_hyp_vecs_start to a
> different section and compiled bpi.S if CONFIG_KVM_INDIRECT_VECTORS.
> In the same kernel, commit e8b22d0f4500 ("arm64: Move the content of
> bpi.S to hyp-entry.S") added #ifdef CONFIG_KVM_INDIRECT_VECTORS around
> the faulty code above. However, the 8c1e3d2bb44c backport did not take
> any of these into account and left the code above bracketed only by
> CONFIG_KVM.
> 
> I think it's better if we dropped this commit altogether from 4.14.y.
> Jeremy, any reason why this should be in stable?

It looks like it can't be easily reverted, more stuff on top depends on
it. Maybe a quick fix would do (hopefully the problem is only in 4.14):

diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index 7d15f4cb6393..e565ec5e072f 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -82,7 +82,7 @@ cpu_enable_trap_ctr_access(const struct arm64_cpu_capabilities *__unused)
 
 DEFINE_PER_CPU_READ_MOSTLY(struct bp_hardening_data, bp_hardening_data);
 
-#ifdef CONFIG_KVM
+#if defined(CONFIG_KVM) && defined(CONFIG_HARDEN_BRANCH_PREDICTOR)
 extern char __smccc_workaround_1_smc_start[];
 extern char __smccc_workaround_1_smc_end[];

-- 
Catalin