linux-kernel - Re: [PATCH 0/7] Allocate module text and data separately

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Message-ID: <68e18364-b904-4ac2-2bf3-504a0b147ecf@csgroup.eu>
Date:   Wed, 26 Jan 2022 05:54:55 +0000
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Luis Chamberlain <mcgrof@...nel.org>
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 0/7] Allocate module text and data separately



Le 25/01/2022 à 21:52, Luis Chamberlain a écrit :
> On Mon, Jan 24, 2022 at 09:22:11AM +0000, Christophe Leroy wrote:
>> This series allow architectures to request having modules data in
>> vmalloc area instead of module area.
>>
>> This is required on powerpc book3s/32 in order to set data non
>> executable, because it is not possible to set executability on page
>> basis, this is done per 256 Mbytes segments. The module area has exec
>> right, vmalloc area has noexec.
>>
>> This can also be useful on other powerpc/32 in order to maximize the
>> chance of code being close enough to kernel core to avoid branch
>> trampolines.
> 
> Am I understanding that this entire effort is for 32-bit powerpc?
> If so, why such an interest in 32-bit these days?
> 

32 bit powerpc processors are still manufactured and are widely used in 
embedded products like internet boxes, small routers, etc ...
One of the reason is that there power consumption hence their heat 
dissipation is way lower than 64 bits variants.

I found the effort quite small compared to the benefit it provides.

Christophe