netdev - Re: [PATCH v4 06/15] mm/execmem, arch: convert simple overrides of module

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Message-ID: <20240415080321.GG40213@noisy.programming.kicks-ass.net>
Date: Mon, 15 Apr 2024 10:03:21 +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,
	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 06/15] mm/execmem, arch: convert simple overrides of
 module_alloc to execmem

On Thu, Apr 11, 2024 at 07:00:42PM +0300, Mike Rapoport wrote:
> +static struct execmem_info execmem_info __ro_after_init = {
> +	.ranges = {
> +		[EXECMEM_DEFAULT] = {
> +			.start = MODULES_VADDR,
> +			.end = MODULES_END,
> +			.alignment = 1,
> +		},
> +	},
> +};
> +
> +struct execmem_info __init *execmem_arch_setup(void)
>  {
> +	execmem_info.ranges[EXECMEM_DEFAULT].pgprot = PAGE_KERNEL;
> +
> +	return &execmem_info;
>  }

> +static struct execmem_info execmem_info __ro_after_init = {
> +	.ranges = {
> +		[EXECMEM_DEFAULT] = {
> +			.start = MODULES_VADDR,
> +			.end = MODULES_END,
> +			.pgprot = PAGE_KERNEL_EXEC,
> +			.alignment = 1,
> +		},
> +	},
> +};
> +
> +struct execmem_info __init *execmem_arch_setup(void)
>  {
> +	return &execmem_info;
>  }

> +static struct execmem_info execmem_info __ro_after_init = {
> +	.ranges = {
> +		[EXECMEM_DEFAULT] = {
> +			.pgprot = PAGE_KERNEL_RWX,
> +			.alignment = 1,
> +		},
> +	},
> +};
> +
> +struct execmem_info __init *execmem_arch_setup(void)
>  {
> +	execmem_info.ranges[EXECMEM_DEFAULT].start = VMALLOC_START;
> +	execmem_info.ranges[EXECMEM_DEFAULT].end = VMALLOC_END;
> +
> +	return &execmem_info;
>  }

> +static struct execmem_info execmem_info __ro_after_init = {
> +	.ranges = {
> +		[EXECMEM_DEFAULT] = {
> +			.pgprot = PAGE_KERNEL,
> +			.alignment = 1,
> +		},
> +	},
> +};
> +
> +struct execmem_info __init *execmem_arch_setup(void)
>  {
> +	execmem_info.ranges[EXECMEM_DEFAULT].start = MODULES_VADDR;
> +	execmem_info.ranges[EXECMEM_DEFAULT].end = MODULES_END;
> +
> +	return &execmem_info;
>  }

> +static struct execmem_info execmem_info __ro_after_init = {
> +	.ranges = {
> +		[EXECMEM_DEFAULT] = {
>  #ifdef CONFIG_SPARC64
> +			.start = MODULES_VADDR,
> +			.end = MODULES_END,
>  #else
> +			.start = VMALLOC_START,
> +			.end = VMALLOC_END,
> +#endif
> +			.alignment = 1,
> +		},
> +	},
> +};
> +
> +struct execmem_info __init *execmem_arch_setup(void)
>  {
> +	execmem_info.ranges[EXECMEM_DEFAULT].pgprot = PAGE_KERNEL;
>  
> +	return &execmem_info;
>  }

I'm amazed by the weird and inconsistent breakup of initializations.

What exactly is wrong with something like:

static struct execmem_info execmem_info __ro_after_init;

struct execmem_info __init *execmem_arch_setup(void)
{
	execmem_info = (struct execmem_info){
		.ranges = {
			[EXECMEM_DEFAULT] = {
				.start	= MODULES_VADDR,
				.end	= MODULES_END,
				.pgprot	= PAGE_KERNEL,
				.alignment = 1,
			},
		},
	};
	return &execmem_info;
}