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Subject: Re: [PATCH 1/2 v2] kprobe: Do not use uaccess functions to access
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From: Jann Horn <jannh@google.com>
Date: Sat, 23 Feb 2019 00:11:58 +0100

> I think what Linus is saying is: There are some scenarios (like a
> system with the old 4G/4G X86 patch) where *the same* address can
> refer to two different pieces of memory, depending on whether you
> interpret it as a kernel pointer or a user pointer.

Exactly.

On sparc64 the kernel is mapped exactly at the same virtual addresses
as userspace processes usually are mapped, even 32-bit ones.  The
difference is the MMU context only.