linux-kernel - Re: [PATCH 0/3] arm64: system call table generation for asm-generic

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Date:   Sat, 19 Jan 2019 23:56:52 +0000
From:   Will Deacon <will.deacon@....com>
To:     Firoz Khan <firoz.khan@...aro.org>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Stefan Agner <stefan@...er.ch>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Russell King <rmk+kernel@...linux.org.uk>,
        linux-arm-kernel@...ts.infradead.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Philippe Ombredanne <pombredanne@...b.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        y2038@...ts.linaro.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, arnd@...db.de, deepa.kernel@...il.com,
        marcin.juszkiewicz@...aro.org
Subject: Re: [PATCH 0/3] arm64: system call table generation for asm-generic

On Thu, Jan 03, 2019 at 09:10:22PM +0530, Firoz Khan wrote:
> This will be an automated scripts to provide easy support
> for add/modify/delete the system call entry by add in 
> respective *.tbl file.
> 
> System call table generation support for asm-generic is
> provide for arm64 architecture which will use the common
> scripts resides in scripts directory and use syscall.tbl
> syscall_arm32.tbl files as inputs. This implementation 
> will replace asm-generic/unistd.h.
> 
> This patch depends on:
>  https://lore.kernel.org/lkml/1546439331-18646-1-git-send-email-firoz.khan@linaro.org/
>  https://lore.kernel.org/lkml/1546520681-24453-1-git-send-email-firoz.khan@linaro.org/

I'm having a hard time understanding what the benefit of this series is,
given that we only support EABI compat tasks. When adding a new compat
system call, you can't just blindly hook it up without checking whether it
needs a wrapper to deal with any type conversion etc, so really we're just
replacing one table with another as far as I can tell. What am I missing?

I also really don't think we should be generating the 32-bit UAPI headers
from the 64-bit compat system call support (if that's what you're trying to
do -- make headers_check fails with your patches applied). arch/arm/ is the
canonical place for the 32-bit UAPI, and we're just implementing that.

Will