linux-kernel - Re: [PATCH 28/31] kasan: add kasan.vmalloc command line flag

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Date:   Fri, 3 Dec 2021 13:09:14 +0100
From:   Marco Elver <elver@...gle.com>
To:     andrey.konovalov@...ux.dev
Cc:     Alexander Potapenko <glider@...gle.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Peter Collingbourne <pcc@...gle.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        kasan-dev@...glegroups.com,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org,
        Evgenii Stepanov <eugenis@...gle.com>,
        linux-kernel@...r.kernel.org,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: Re: [PATCH 28/31] kasan: add kasan.vmalloc command line flag

On Tue, Nov 30, 2021 at 11:08PM +0100, andrey.konovalov@...ux.dev wrote:
[...]
>  enum kasan_arg_stacktrace {
>  	KASAN_ARG_STACKTRACE_DEFAULT,
>  	KASAN_ARG_STACKTRACE_OFF,
> @@ -40,6 +46,7 @@ enum kasan_arg_stacktrace {
>  
>  static enum kasan_arg kasan_arg __ro_after_init;
>  static enum kasan_arg_mode kasan_arg_mode __ro_after_init;
> +static enum kasan_arg_vmalloc kasan_arg_vmalloc __ro_after_init;
>  static enum kasan_arg_stacktrace kasan_arg_stacktrace __ro_after_init;

It just occurred to me that all of these (except kasan_arg_mode) are
only used by __init functions, so they could actually be marked
__initdata instead of __ro_after_init to free up some bytes after init.

Not sure if you think it's worth it, I leave it to you.

[...] 
> +	switch (kasan_arg_vmalloc) {
> +	case KASAN_ARG_VMALLOC_DEFAULT:
> +		/* Default to enabling vmalloc tagging. */
> +		static_branch_enable(&kasan_flag_vmalloc);
> +		break;
> +	case KASAN_ARG_VMALLOC_OFF:
> +		/* Do nothing, kasan_flag_vmalloc keeps its default value. */
> +		break;
> +	case KASAN_ARG_VMALLOC_ON:
> +		static_branch_enable(&kasan_flag_vmalloc);
> +		break;
> +	}

The KASAN_ARG_STACKTRACE_DEFAULT and KASAN_ARG_VMALLOC_ON cases can be
combined.