Re: [PATCH 1/2 v2] kprobe: Do not use uaccess functions to access kernel memory that can fault

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.