Date: Tue, 12 Jan 2016 14:23:27 +0100 From: Ard Biesheuvel <ard.biesheuvel@...aro.org> To: Mark Rutland <mark.rutland@....com> Cc: "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, kernel-hardening@...ts.openwall.com, Will Deacon <will.deacon@....com>, Catalin Marinas <catalin.marinas@....com>, Leif Lindholm <leif.lindholm@...aro.org>, Kees Cook <keescook@...omium.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Stuart Yoder <stuart.yoder@...escale.com>, Sharma Bhupesh <bhupesh.sharma@...escale.com>, Arnd Bergmann <arnd@...db.de>, Marc Zyngier <marc.zyngier@....com>, Christoffer Dall <christoffer.dall@...aro.org> Subject: Re: [PATCH v3 05/21] arm64: kvm: deal with kernel symbols outside of linear mapping On 12 January 2016 at 13:36, Mark Rutland <mark.rutland@....com> wrote: > On Mon, Jan 11, 2016 at 02:18:58PM +0100, Ard Biesheuvel wrote: >> KVM on arm64 uses a fixed offset between the linear mapping at EL1 and >> the HYP mapping at EL2. Before we can move the kernel virtual mapping >> out of the linear mapping, we have to make sure that references to kernel >> symbols that are accessed via the HYP mapping are translated to their >> linear equivalent. >> >> To prevent inadvertent direct references from sneaking in later, change >> the type of all extern declarations to HYP kernel symbols to the opaque >> 'struct kvm_ksym', which does not decay to a pointer type like char arrays >> and function references. This is not bullet proof, but at least forces the >> user to take the address explicitly rather than referencing it directly. >> >> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org> > > Cool feature! > >> diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h >> index 5e377101f919..e3865845d3e1 100644 >> --- a/arch/arm64/include/asm/kvm_asm.h >> +++ b/arch/arm64/include/asm/kvm_asm.h >> @@ -105,24 +105,29 @@ >> #ifndef __ASSEMBLY__ >> struct kvm; >> struct kvm_vcpu; >> +struct kvm_ksym; > > So that one doesn't have to trawl git logs, it might be worth a comment > as to the purpose of struct kvm_ksym (and thus why we never need to > actually define it). > Yes, I can add something > Either way: > > Reviewed-by: Mark Rutland <mark.rutland@....com> > Thanks
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