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

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Date:   Tue, 22 Jan 2019 09:47:36 +0530
From:   Firoz Khan <firoz.khan@...aro.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Will Deacon <will.deacon@....com>,
        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 <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 Mailman List <y2038@...ts.linaro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Deepa Dinamani <deepa.kernel@...il.com>,
        Marcin Juszkiewicz <marcin.juszkiewicz@...aro.org>
Subject: Re: [PATCH 0/3] arm64: system call table generation for asm-generic

Hi Arnd, Will,

thanks for the email.

I'm want to abandon this patch series. Will post new patch series for
system call
table generation support for asm-generic and some other stuff together by end of
this week or early next week.

Thanks
Firoz

On Mon, 21 Jan 2019 at 21:24, Arnd Bergmann <arnd@...db.de> wrote:
>
> n Sun, Jan 20, 2019 at 12:57 AM Will Deacon <will.deacon@....com> wrote:
> >
> > 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?
>
> The point that is missing in the description above is that all unistd.h
> and syscall.S files are now being generated from a .tbl file, across
> all architectures. This was already done on arm32, x86 and s390
> before 4.20, but is now done on all architectures that don't use
> the uapi/asm-generic/unistd.h header, and the arm32 compat version for
> arm64.
>
> The newly added file has the same format as all other tables, and
> will be easier to synchronize with the arm32 version, which has
> almost the same contents (arm32 has oabi support, arm64 has
> compat support).
>
> > 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.
>
> I think you just misread what Firoz was trying to say here: The
> arm64 uapi/asm/unistd.h file is now being generated from the
> generic syscall.tbl file, while the compat asm/unistd32.h file is not
> part of the UAPI. In both cases though, the data from the old files
> is being replaced with data in the more compact and (hopefully)
> more readable format.
>
>
>     Arnd