linux-kernel - Re: [PATCH v3 4/6] modules: Add CONFIG_ARCH_WANTS_MODULES_DATA_IN

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Date:   Thu, 3 Feb 2022 07:05:13 +0000
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Luis Chamberlain <mcgrof@...nel.org>,
        Aaron Tomlin <atomlin@...hat.com>
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>,
        Jason Wessel <jason.wessel@...driver.com>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Douglas Anderson <dianders@...omium.org>
Subject: Re: [PATCH v3 4/6] modules: Add
 CONFIG_ARCH_WANTS_MODULES_DATA_IN_VMALLOC



Le 03/02/2022 à 01:01, Luis Chamberlain a écrit :
> On Sat, Jan 29, 2022 at 05:02:09PM +0000, Christophe Leroy wrote:
>> diff --git a/kernel/module.c b/kernel/module.c
>> index 11f51e17fb9f..f3758115ebaa 100644
>> --- a/kernel/module.c
>> +++ b/kernel/module.c
>> @@ -81,7 +81,9 @@
>>   /* If this is set, the section belongs in the init part of the module */
>>   #define INIT_OFFSET_MASK (1UL << (BITS_PER_LONG-1))
>>   
>> +#ifndef CONFIG_ARCH_WANTS_MODULES_DATA_IN_VMALLOC
>>   #define	data_layout core_layout
>> +#endif
>>   
>>   /*
>>    * Mutex protects:
>> @@ -111,6 +113,12 @@ static struct mod_tree_root {
>>   #define module_addr_min mod_tree.addr_min
>>   #define module_addr_max mod_tree.addr_max
>>   
>> +#ifdef CONFIG_ARCH_WANTS_MODULES_DATA_IN_VMALLOC
>> +static struct mod_tree_root mod_data_tree __cacheline_aligned = {
>> +	.addr_min = -1UL,
>> +};
>> +#endif
>> +
>>   #ifdef CONFIG_MODULES_TREE_LOOKUP
>>   
>>   /*
>> @@ -186,6 +194,11 @@ static void mod_tree_insert(struct module *mod)
>>   	__mod_tree_insert(&mod->core_layout.mtn, &mod_tree);
>>   	if (mod->init_layout.size)
>>   		__mod_tree_insert(&mod->init_layout.mtn, &mod_tree);
>> +
>> +#ifdef CONFIG_ARCH_WANTS_MODULES_DATA_IN_VMALLOC
>> +	mod->data_layout.mtn.mod = mod;
>> +	__mod_tree_insert(&mod->data_layout.mtn, &mod_data_tree);
>> +#endif
> 
> 
> kernel/ directory has quite a few files, module.c is the second to
> largest file, and it has tons of stuff. Aaron is doing work to
> split things out to make code easier to read and so that its easier
> to review changes. See:
> 
> https://lkml.kernel.org/r/20220130213214.1042497-1-atomlin@redhat.com
> 
> I think this is a good patch example which could benefit from that work.
> So I'd much prefer to see that work go in first than this, so to see if
> we can make the below changes more compartamentalized.
> 
> Curious, how much testing has been put into this series?


I tested the change up to (including) patch 4 to verify it doesn't 
introduce regression when not using 
CONFIG_ARCH_WANTS_MODULES_DATA_IN_VMALLOC,

Then I tested with patch 5. I first tried with the 'hello world' test 
module. After that I loaded several important modules and checked I 
didn't get any regression, both with and without STRICT_MODULES_RWX and 
I checked the consistency in /proc/vmallocinfo
  /proc/modules /sys/class/modules/*

I also tested with a hacked module_alloc() to force branch trampolines.

Christophe