linux-kernel - Re: [PATCH] parisc: fix module loading failure of large kernel modules (take 4)

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Date:	Thu, 01 Jan 2009 13:02:43 +0100
From:	Helge Deller <deller@....de>
To:	Rusty Russell <rusty@...tcorp.com.au>
CC:	linux-parisc <linux-parisc@...r.kernel.org>,
	Linux Kernel Development <linux-kernel@...r.kernel.org>,
	Kyle McMartin <kyle@...artin.ca>,
	Randolph Chung <randolph@...sq.org>,
	Linus <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Sam Ravnborg <sam@...nborg.org>,
	John David Anglin <dave@...uly1.hia.nrc.ca>
Subject: Re: [PATCH] parisc: fix module loading failure of large kernel modules
 (take 4)

Rusty Russell wrote:
> On Thursday 01 January 2009 00:43:56 Helge Deller wrote:
>> Rusty Russell wrote:
>>> Not quite what I had in mind... let me show you:
>>> ...
>>> Otherwise I'd have called it "arch_module_extra_size()".
>> This would mean that I can increase the section size in the arch-specific function
>> by returning a bigger value than sh_size.
>> This would give me space at the end of the section, but not at the beginning 
>> (which is what I need), as sh_entsize (the offset into memory) will stay the 
>> same as before.
> 
> Ah, OK.  I assumed that extra room at the end was sufficient.
> 
> So I've taken your previous patch and renamed the function to
> arch_mod_section_prepend().  

Thanks a lot !!!!
Patch below is ok and I'll adjust the parisc-specific patch
acordingly.

> If we decide not to kill those bad gcc versions,
> I'll stick it in some other random file (lib/weak.c?  Blech...)

Andrew has pulled in the patch from Adrian in his -mm tree, so we should
be safe now.

> BTW, this is very late for this merge window.  I would have liked to see
> this a month ago :(

Yes, sorry, I didn't had a patch available earlier.
I hope it's still in-time though, esp. as this will fix one of our longest
outstanding bugs on parisc and is quite important for us.

Thanks,
Helge


> Subject: module: fix module loading failure of large kernel modules for parisc
> Date: Wed, 31 Dec 2008 12:31:18 +0100
> From: Helge Deller <deller@....de>
> 
> When creating the final layout of a kernel module in memory, allow the
> module loader to reserve some additional memory in front of a given section.
> This is currently only needed for the parisc port which needs to put the
> stub entries there to fulfill the 17/22bit PCREL relocations with large
> kernel modules like xfs.
> 
> Signed-off-by: Helge Deller <deller@....de>
> Signed-off-by: Rusty Russell <rusty@...tcorp.com.au> (renamed fn)
> 
> diff --git a/include/linux/moduleloader.h b/include/linux/moduleloader.h
> --- a/include/linux/moduleloader.h
> +++ b/include/linux/moduleloader.h
> @@ -12,6 +12,9 @@ int module_frob_arch_sections(Elf_Ehdr *
>  			      Elf_Shdr *sechdrs,
>  			      char *secstrings,
>  			      struct module *mod);
> +
> +/* Additional bytes needed by arch in front of individual sections */
> +unsigned int arch_mod_section_prepend(struct module *mod, unsigned int section);
>  
>  /* Allocator used for allocating struct module, core sections and init
>     sections.  Returns NULL on failure. */
> diff --git a/kernel/module.c b/kernel/module.c
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -1588,11 +1588,21 @@ static int simplify_symbols(Elf_Shdr *se
>  	return ret;
>  }
>  
> +/* Additional bytes needed by arch in front of individual sections */
> +unsigned int __weak arch_mod_section_prepend(struct module *mod,
> +					     unsigned int section)
> +{
> +	/* default implementation just returns zero */
> +	return 0;
> +}
> +
>  /* Update size with this section: return offset. */
> -static long get_offset(unsigned int *size, Elf_Shdr *sechdr)
> +static long get_offset(struct module *mod, unsigned int *size,
> +		       Elf_Shdr *sechdr, unsigned int section)
>  {
>  	long ret;
>  
> +	*size += arch_mod_section_prepend(mod, section);
>  	ret = ALIGN(*size, sechdr->sh_addralign ?: 1);
>  	*size = ret + sechdr->sh_size;
>  	return ret;
> @@ -1632,7 +1642,7 @@ static void layout_sections(struct modul
>  			    || strncmp(secstrings + s->sh_name,
>  				       ".init", 5) == 0)
>  				continue;
> -			s->sh_entsize = get_offset(&mod->core_size, s);
> +			s->sh_entsize = get_offset(mod, &mod->core_size, s, i);
>  			DEBUGP("\t%s\n", secstrings + s->sh_name);
>  		}
>  		if (m == 0)
> @@ -1650,7 +1660,7 @@ static void layout_sections(struct modul
>  			    || strncmp(secstrings + s->sh_name,
>  				       ".init", 5) != 0)
>  				continue;
> -			s->sh_entsize = (get_offset(&mod->init_size, s)
> +			s->sh_entsize = (get_offset(mod, &mod->init_size, s, i)
>  					 | INIT_OFFSET_MASK);
>  			DEBUGP("\t%s\n", secstrings + s->sh_name);
>  		}
> 

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