Re: clean up and streamline probe_kernel_* and friends v4

On Thu, 21 May 2020 17:22:38 +0200 Christoph Hellwig [off-list ref] wrote:

this series start cleaning up the safe kernel and user memory probing
helpers in mm/maccess.c, and then allows architectures to implement
the kernel probing without overriding the address space limit and
temporarily allowing access to user memory.  It then switches x86
over to this new mechanism by reusing the unsafe_* uaccess logic.

This version also switches to the saner copy_{from,to}_kernel_nofault
naming suggested by Linus.

I kept the x86 helpers as-is without calling unsage_{get,put}_user as
that avoids a number of hard to trace casts, and it will still work
with the asm-goto based version easily.

hm.  Applying linux-next to this series generates a lot of rejects against
powerpc:

-rw-rw-r-- 1 akpm akpm  493 May 25 15:06 arch/powerpc/kernel/kgdb.c.rej
-rw-rw-r-- 1 akpm akpm 6461 May 25 15:06 arch/powerpc/kernel/trace/ftrace.c.rej
-rw-rw-r-- 1 akpm akpm  447 May 25 15:06 arch/powerpc/mm/fault.c.rej
-rw-rw-r-- 1 akpm akpm  623 May 25 15:06 arch/powerpc/perf/core-book3s.c.rej
-rw-rw-r-- 1 akpm akpm 1408 May 25 15:06 arch/riscv/kernel/patch.c.rej

the arch/powerpc/kernel/trace/ftrace.c ones aren't very trivial.

It's -rc7.  Perhaps we should park all this until 5.8-rc1?