linux-kernel - Re: [PATCH v2 06/12] mm/execmem: introduce execmem_data

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Date:   Fri, 16 Jun 2023 16:55:53 +0000
From:   "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
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Subject: Re: [PATCH v2 06/12] mm/execmem: introduce execmem_data_alloc()

On Fri, 2023-06-16 at 11:50 +0300, Mike Rapoport wrote:
> From: "Mike Rapoport (IBM)" <rppt@...nel.org>
> 
> Data related to code allocations, such as module data section, need
> to
> comply with architecture constraints for its placement and its
> allocation right now was done using execmem_text_alloc().
> 
> Create a dedicated API for allocating data related to code
> allocations
> and allow architectures to define address ranges for data
> allocations.

Right now the cross-arch way to specify kernel memory permissions is
encoded in the function names of all the set_memory_foo()'s. You can't
just have unified prot names because some arch's have NX and some have
X bits, etc. CPA wouldn't know if it needs to set or unset a bit if you
pass in a PROT.

But then you end up with a new function for *each* combination (i.e.
set_memory_rox()). I wish CPA has flags like mmap() does, and I wonder
if it makes sense here instead of execmem_data_alloc().

Maybe that is an overhaul for another day though...