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

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Date: Sun, 14 Apr 2024 09:53:59 +0300
From: Mike Rapoport <rppt@...nel.org>
To: Luis Chamberlain <mcgrof@...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>,
	Dinh Nguyen <dinguyen@...nel.org>,
	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>,
	Kent Overstreet <kent.overstreet@...ux.dev>,
	Mark Rutland <mark.rutland@....com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Nadav Amit <nadav.amit@...il.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Puranjay Mohan <puranjay12@...il.com>,
	Rick Edgecombe <rick.p.edgecombe@...el.com>,
	Russell King <linux@...linux.org.uk>, Song Liu <song@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
	Thomas Gleixner <tglx@...utronix.de>, Will Deacon <will@...nel.org>,
	bpf@...r.kernel.org, linux-arch@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-mips@...r.kernel.org,
	linux-mm@...ck.org, linux-modules@...r.kernel.org,
	linux-parisc@...r.kernel.org, linux-riscv@...ts.infradead.org,
	linux-s390@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, loongarch@...ts.linux.dev,
	netdev@...r.kernel.org, sparclinux@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH v4 05/15] mm: introduce execmem_alloc() and execmem_free()

On Thu, Apr 11, 2024 at 12:42:05PM -0700, Luis Chamberlain wrote:
> 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.

Ok.
 
> > 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.

Will do.
 
>   Luis

-- 
Sincerely yours,
Mike.