linux-kernel - Re: [PATCH v3 3/6] modules: Introduce data

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Date:   Wed, 2 Feb 2022 15:48:56 -0800
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Christophe Leroy <christophe.leroy@...roup.eu>
Cc:     Jessica Yu <jeyu@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "kgdb-bugreport@...ts.sourceforge.net" 
        <kgdb-bugreport@...ts.sourceforge.net>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>
Subject: Re: [PATCH v3 3/6] modules: Introduce data_layout

On Sat, Jan 29, 2022 at 05:02:07PM +0000, Christophe Leroy wrote:
> diff --git a/kernel/module.c b/kernel/module.c
> index 163e32e39064..11f51e17fb9f 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -81,6 +81,8 @@
>  /* If this is set, the section belongs in the init part of the module */
>  #define INIT_OFFSET_MASK (1UL << (BITS_PER_LONG-1))
>  
> +#define	data_layout core_layout
> +
>  /*
>   * Mutex protects:
>   * 1) List of modules (also safely readable with preempt_disable),
> @@ -2451,7 +2454,10 @@ static void layout_sections(struct module *mod, struct load_info *info)
>  			    || s->sh_entsize != ~0UL
>  			    || module_init_layout_section(sname))
>  				continue;
> -			s->sh_entsize = get_offset(mod, &mod->core_layout.size, s, i);
> +			if (m)
> +				s->sh_entsize = get_offset(mod, &mod->data_layout.size, s, i);
> +			else
> +				s->sh_entsize = get_offset(mod, &mod->core_layout.size, s, i);
>  			pr_debug("\t%s\n", sname);

Huh why is this branching here, given you just used mod->data_layout in
all other areas?

> @@ -3468,6 +3474,8 @@ static int move_module(struct module *mod, struct load_info *info)
>  		if (shdr->sh_entsize & INIT_OFFSET_MASK)
>  			dest = mod->init_layout.base
>  				+ (shdr->sh_entsize & ~INIT_OFFSET_MASK);
> +		else if (!(shdr->sh_flags & SHF_EXECINSTR))
> +			dest = mod->data_layout.base + shdr->sh_entsize;
>  		else
>  			dest = mod->core_layout.base + shdr->sh_entsize;
>  

Likewise here.

  Luis