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Date: Sat, 13 Oct 2018 22:27:56 +1000
From: Nicholas Piggin <npiggin@gmail.com>
To: Michael Ellerman <mpe@ellerman.id.au>
Subject: Re: [PATCH 1/3] powerpc: Split user/kernel definitions of struct
 pt_regs
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On Sat, 13 Oct 2018 21:56:44 +1100
Michael Ellerman <mpe@ellerman.id.au> wrote:

> We use a shared definition for struct pt_regs in uapi/asm/ptrace.h.
> That means the layout of the structure is ABI, ie. we can't change it.
> 
> That would be fine if it was only used to describe the user-visible
> register state of a process, but it's also the struct we use in the
> kernel to describe the registers saved in an interrupt frame.
> 
> We'd like more flexibility in the content (and possibly layout) of the
> kernel version of the struct, but currently that's not possible.
> 
> So split the definition into a user-visible definition which remains
> unchanged, and a kernel internal one.
> 
> At the moment they're still identical, and we check that at build
> time. That's because we have code (in ptrace etc.) that assumes that
> they are the same. We will fix that code in future patches, and then
> we can break the strict symmetry between the two structs.
> 
> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Yeah this looks much better than my int_frame thing, thanks.

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

Thanks,
Nick