linux-kernel - Re: [PATCH v2 2/3] KVM: x86: introduce definitions to support static calls for kvm_x86

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <2e2cd2d9-e010-b435-3aba-35bac1b4cc14@akamai.com>
Date:   Fri, 15 Jan 2021 10:03:53 -0500
From:   Jason Baron <jbaron@...mai.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     seanjc@...gle.com, kvm@...r.kernel.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Andrea Arcangeli <aarcange@...hat.com>
Subject: Re: [PATCH v2 2/3] KVM: x86: introduce definitions to support static
 calls for kvm_x86_ops



On 1/15/21 8:50 AM, Paolo Bonzini wrote:
> On 15/01/21 10:26, Peter Zijlstra wrote:
>>> +#define KVM_X86_OP(func)                         \
>>> +    DEFINE_STATIC_CALL_NULL(kvm_x86_##func,                 \
>>> +                *(((struct kvm_x86_ops *)0)->func));
>>> +#define KVM_X86_OP_NULL KVM_X86_OP
>>> +#include <asm/kvm-x86-ops.h>
>>> +EXPORT_STATIC_CALL_GPL(kvm_x86_get_cs_db_l_bits);
>>> +EXPORT_STATIC_CALL_GPL(kvm_x86_cache_reg);
>>> +EXPORT_STATIC_CALL_GPL(kvm_x86_tlb_flush_current);
>> Would something like:
>>
>>   
>> https://urldefense.com/v3/__https://lkml.kernel.org/r/20201110103909.GD2594@hirez.programming.kicks-ass.net__;!!GjvTz_vk!GbAPurpdyP1TaDRZN0NvvBkOLJhmRHzNtv0ZVIwZqNrJpMYze75mJzpUNJMRAg$
>>
>> Be useful? That way modules can call the static_call() but not change
>> it.
>>
> 
> Maybe not in these cases, but in general there may be cases where we later want to change the static_call (for example replacing jump labels with
> static_calls).
> 
> Paolo
> 

I tried this out but got:

ERROR: modpost: "__SCK__kvm_x86_cache_reg" [arch/x86/kvm/kvm-amd.ko] undefined!
ERROR: modpost: "__SCK__kvm_x86_tlb_flush_current" [arch/x86/kvm/kvm-intel.ko] undefined!
ERROR: modpost: "__SCK__kvm_x86_get_cs_db_l_bits" [arch/x86/kvm/kvm-intel.ko] undefined!
ERROR: modpost: "__SCK__kvm_x86_cache_reg" [arch/x86/kvm/kvm-intel.ko] undefined!

I'm a bit confused because we have:

#define __static_call(name)                                             \
({                                                                      \
        __ADDRESSABLE(STATIC_CALL_KEY(name));                           \
        &STATIC_CALL_TRAMP(name);                                       \
})

And so it looks to me like we need to still reference the key from the module code.

Thanks,

-Jason