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Date: Sun, 18 Jun 2023 11:00:27 +0300
From: Mike Rapoport <rppt@kernel.org>
To: Andy Lutomirski <luto@kernel.org>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Christophe Leroy <christophe.leroy@csgroup.eu>,
	"David S. Miller" <davem@davemloft.net>,
	Dinh Nguyen <dinguyen@kernel.org>,
	Heiko Carstens <hca@linux.ibm.com>, Helge Deller <deller@gmx.de>,
	Huacai Chen <chenhuacai@kernel.org>,
	Kent Overstreet <kent.overstreet@linux.dev>,
	Luis Chamberlain <mcgrof@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Nadav Amit <nadav.amit@gmail.com>,
	"Naveen N. Rao" <naveen.n.rao@linux.ibm.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Puranjay Mohan <puranjay12@gmail.com>,
	Rick P Edgecombe <rick.p.edgecombe@intel.com>,
	"Russell King (Oracle)" <linux@armlinux.org.uk>,
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	the arch/x86 maintainers <x86@kernel.org>
Subject: Re: [PATCH v2 02/12] mm: introduce execmem_text_alloc() and
 jit_text_alloc()
Message-ID: <20230618080027.GA52412@kernel.org>
References: <20230616085038.4121892-1-rppt@kernel.org>
 <20230616085038.4121892-3-rppt@kernel.org>
 <f9a7eebe-d36e-4587-b99d-35d4edefdd14@app.fastmail.com>
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In-Reply-To: <f9a7eebe-d36e-4587-b99d-35d4edefdd14@app.fastmail.com>

On Sat, Jun 17, 2023 at 01:38:29PM -0700, Andy Lutomirski wrote:
> On Fri, Jun 16, 2023, at 1:50 AM, Mike Rapoport wrote:
> > From: "Mike Rapoport (IBM)" <rppt@kernel.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_text_alloc(), execmem_free(), jit_text_alloc(), jit_free() APIs.
> >
> > Initially, execmem_text_alloc() and jit_text_alloc() are wrappers for
> > module_alloc() and execmem_free() and jit_free() are replacements of
> > module_memfree() to allow updating all call sites to use the new APIs.
> >
> > The intention semantics for new allocation APIs:
> >
> > * execmem_text_alloc() should be used to allocate memory that must reside
> >   close to the kernel image, like loadable kernel modules and generated
> >   code that is restricted by relative addressing.
> >
> > * jit_text_alloc() should be used to allocate memory for generated code
> >   when there are no restrictions for the code placement. For
> >   architectures that require that any code is within certain distance
> >   from the kernel image, jit_text_alloc() will be essentially aliased to
> >   execmem_text_alloc().
> >
> 
> Is there anything in this series to help users do the appropriate
> synchronization when the actually populate the allocated memory with
> code?  See here, for example:

This series only factors out the executable allocations from modules and
puts them in a central place.
Anything else would go on top after this lands.
 
> https://lore.kernel.org/linux-fsdevel/cb6533c6-cea0-4f04-95cf-b8240c6ab405@app.fastmail.com/T/#u

-- 
Sincerely yours,
Mike.