[PATCH -next 0/2] riscv: ptrace: implement PTRACE_{PEEK,POKE}USR

[Palmer Dabbelt]

On Mon, 22 Aug 2022 01:19:03 PDT (-0700), schwab at suse.de wrote:
> On Aug 22 2022, Yipeng Zou wrote:
>
>> The PTRACE_{PEEK,POKE}USR going to get/set tracee's user register.
>> This patch sets add PTRACE_{PEEK,POKE}USR and compat implement to
>> riscv.
>>
>> I notice this issuse when transplanting some app form x86 to riscv
>> recently.
>> I don't know why these two function are not implemented now, and I
>> found few talk about that.
>>
>> The {PEEK,POKE}USR are both defined in include\uapi\linux\ptrace.h,
>> So I was thinking maybe these two function shouled be implemented.
>
> There are PTRACE_[GS]ETREGSET.  I think PTRACE_{PEEK,POKE}USR are
> legacy-only.

That's my understanding as well.  Anything ported to RISC-V would need 
to understand the new register formats, so there's not much benefit to 
supporting these old flavors of register twiddling -- maybe some 
refactoring needs to be done in userspace to take advantage of accessing 
multiple registers at the same time, but that should probably be done 
anyway as all ports support the new interfaces these days.

There's been a few rounds of these having been posted, maybe that means 
the documentation should be improved?  I sent 
<https://lore.kernel.org/r/20221006012432.19008-1-palmer@rivosinc.com/>, 
that'll also help sort out whether we're supposed to have these.