linux-kernel - Re: [PATCH v4 05/15] mm: introduce execmem_alloc() and execmem

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Message-ID: <Zhg9DXzagPbpNGH1@bombadil.infradead.org>
Date: Thu, 11 Apr 2024 12:42:05 -0700
From: Luis Chamberlain <mcgrof@...nel.org>
To: Mike Rapoport <rppt@...nel.org>
Cc: linux-kernel@...r.kernel.org, Alexandre Ghiti <alexghiti@...osinc.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Björn Töpel <bjorn@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	"David S. Miller" <davem@...emloft.net>,
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	Donald Dutile <ddutile@...hat.com>,
	Eric Chanudet <echanude@...hat.com>,
	Heiko Carstens <hca@...ux.ibm.com>, Helge Deller <deller@....de>,
	Huacai Chen <chenhuacai@...nel.org>,
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	Michael Ellerman <mpe@...erman.id.au>,
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	Puranjay Mohan <puranjay12@...il.com>,
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Subject: Re: [PATCH v4 05/15] mm: introduce execmem_alloc() and execmem_free()

On Thu, Apr 11, 2024 at 07:00:41PM +0300, Mike Rapoport wrote:
> From: "Mike Rapoport (IBM)" <rppt@...nel.org>
> 
> module_alloc() is used everywhere as a mean to allocate memory for code.
> 
> Beside being semantically wrong, this unnecessarily ties all subsystems
> that need to allocate code, such as ftrace, kprobes and BPF to modules and
> puts the burden of code allocation to the modules code.
> 
> Several architectures override module_alloc() because of various
> constraints where the executable memory can be located and this causes
> additional obstacles for improvements of code allocation.
> 
> Start splitting code allocation from modules by introducing execmem_alloc()
> and execmem_free() APIs.
> 
> Initially, execmem_alloc() is a wrapper for module_alloc() and
> execmem_free() is a replacement of module_memfree() to allow updating all
> call sites to use the new APIs.
> 
> Since architectures define different restrictions on placement,
> permissions, alignment and other parameters for memory that can be used by
> different subsystems that allocate executable memory, execmem_alloc() takes
> a type argument, that will be used to identify the calling subsystem and to
> allow architectures define parameters for ranges suitable for that
> subsystem.

It would be good to describe this is a non-fuctional change.

> Signed-off-by: Mike Rapoport (IBM) <rppt@...nel.org>
> ---

> diff --git a/mm/execmem.c b/mm/execmem.c
> new file mode 100644
> index 000000000000..ed2ea41a2543
> --- /dev/null
> +++ b/mm/execmem.c
> @@ -0,0 +1,26 @@
> +// SPDX-License-Identifier: GPL-2.0

And this just needs to copy over the copyright notices from the main.c file.

  Luis