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

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Date: Mon, 15 Apr 2024 09:52:41 +0200
From: Peter Zijlstra <peterz@...radead.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>,
	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>,
	Luis Chamberlain <mcgrof@...nel.org>,
	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,
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	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 07:00:41PM +0300, Mike Rapoport wrote:
> +/**
> + * enum execmem_type - types of executable memory ranges
> + *
> + * There are several subsystems that allocate executable memory.
> + * Architectures define different restrictions on placement,
> + * permissions, alignment and other parameters for memory that can be used
> + * by these subsystems.
> + * Types in this enum identify subsystems that allocate executable memory
> + * and let architectures define parameters for ranges suitable for
> + * allocations by each subsystem.
> + *
> + * @EXECMEM_DEFAULT: default parameters that would be used for types that
> + * are not explcitly defined.
> + * @EXECMEM_MODULE_TEXT: parameters for module text sections
> + * @EXECMEM_KPROBES: parameters for kprobes
> + * @EXECMEM_FTRACE: parameters for ftrace
> + * @EXECMEM_BPF: parameters for BPF
> + * @EXECMEM_TYPE_MAX:
> + */
> +enum execmem_type {
> +	EXECMEM_DEFAULT,
> +	EXECMEM_MODULE_TEXT = EXECMEM_DEFAULT,
> +	EXECMEM_KPROBES,
> +	EXECMEM_FTRACE,
> +	EXECMEM_BPF,
> +	EXECMEM_TYPE_MAX,
> +};

Can we please get a break-down of how all these types are actually
different from one another?

I'm thinking some platforms have a tiny immediate space (arm64 comes to
mind) and has less strict placement constraints for some of them?