Subject: Re: [PATCH v4 05/15] mm: introduce execmem_alloc() and execmem_free()

From: Peter Zijlstra <[email-masked]>
Date: Mon, 15 Apr 2024 09:52:41 +0200

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?