linux-kernel - Re: [PATCH 2/4] arm64/process: Make loading of 32bit processes depend on aarch32

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Message-ID: <ZTEjSD4_4xsJWkEi@apocalypse>
Date:   Thu, 19 Oct 2023 14:38:32 +0200
From:   Andrea della Porta <aporta@...e.de>
To:     Mark Rutland <mark.rutland@....com>
Cc:     Andrea della Porta <andrea.porta@...e.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        nik.borisov@...e.com
Subject: Re: [PATCH 2/4] arm64/process: Make loading of 32bit processes
 depend on aarch32_enabled()

On 13:52 Wed 18 Oct     , Mark Rutland wrote:
> On Wed, Oct 18, 2023 at 01:13:20PM +0200, Andrea della Porta wrote:
> > Major aspect of Aarch32 emulation is the ability to load 32bit
> > processes.
> > That's currently decided (among others) by compat_elf_check_arch().
> > 
> > Make the macro use aarch32_enabled() to decide if Aarch32 compat is
> > enabled before loading a 32bit process.
> > 
> > Signed-off-by: Andrea della Porta <andrea.porta@...e.com>
> 
> Why can't you make system_supports_32bit_el0() take the option into account
> instead?
>

I may be wrong here, but it seems to me that system_supports_32bit_el0()
answers teh question "can this system supports compat execution?" rather than
"do I want this system to run any compat execution?". That's the point of
aarch32_enabled(), to state whether we want teh system to run A32 code or not,
regardless of the system supporting it (of course, if the system does not
support A32 in EL0, this is a no-no, but that's another story).

Andrea