Messages in this thread | | | Date | Tue, 01 Dec 2020 15:37:26 +0000 | From | Marc Zyngier <> | Subject | Re: [PATCH 0/3] arm64:msr: Add MSR driver |
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On 2020-12-01 14:25, wangrongwei wrote: >> 2020年12月1日 下午4:12,Marc Zyngier <maz@kernel.org> 写道: >> >> On 2020-12-01 03:09, wangrongwei wrote: >>> Hi >>> We have validate this driver in vm and physical machine, and works >>> fine. >> >> But what does "work fine" mean? None of these system registers are >> supposed >> to be accessible from userspace, so please explain *what* you are >> trying to >> do with this, other that introducing security holes and general system >> instability? > I think I know what you mean. Do you want me to describe how we > achieved it? > In x86, the different registers can be accessed directly using the > rdmsr and wrmsr instructions, but in ARM, since these two instructions > are missing, so we modify the code segment during runtime, similar to > the principle of static_key.
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These are implementation details, none of which answer my question:
What makes you think this is a good idea? I cannot see any legitimate reason for userspace to ever access privileged system registers, and the fact that x86 has such feature isn't a good justification.
M. -- Jazz is not dead. It just smells funny...
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