linux-kernel - Re: [PATCH 1/3] microblaze: Replace NR

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Date:   Wed, 3 Oct 2018 10:39:40 +0530
From:   Firoz Khan <firoz.khan@...aro.org>
To:     Michal Simek <michal.simek@...inx.com>
Cc:     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>,
        Arnd Bergmann <arnd@...db.de>,
        Deepa Dinamani <deepa.kernel@...il.com>,
        Marcin Juszkiewicz <marcin.juszkiewicz@...aro.org>
Subject: Re: [PATCH 1/3] microblaze: Replace NR_syscalls macro from asm/unistd.h

Hi Michal,

On Tue, 2 Oct 2018 at 12:37, Michal Simek <michal.simek@...inx.com> wrote:
>
> On 18.9.2018 08:37, Firoz Khan wrote:
> > On 9 August 2018 at 12:18, Michal Simek <michal.simek@...inx.com> wrote:
> >> On 9.8.2018 07:27, Firoz Khan wrote:
> >>> __NR_syscalls macro holds the number of system call exist in this
> >>> architecture. This macro is currently the part of asm/unistd.h file.
> >>> We have change the value of __NR_syscalls, if we add or delete a
> >>> system call.
> >>>
> >>> One of the patch in this patch series has a script which will
> >>> generate a uapi header based on syscall.tbl file. The syscall.tbl
> >>> file contains the number of system call information. So we have
> >>> two option to update __NR_syscalls value.
> >>>
> >>> 1. Update __NR_syscalls in asm/unistd.h manually by counting the
> >>>    no.of system calls. No need to update __NR_syscalls untill
> >>>    we either add a new system call or delete an existing system
> >>>    call.
> >>>
> >>> 2. We can keep this feature it above mentioned script, that'll
> >>>    count the number of syscalls and keep it in a generated file.
> >>>    In this case we don't need to explicitly update __NR_syscalls
> >>>    in asm/unistd.h file.
> >>>
> >>> The 2nd option will be the recommended one. For that, I moved the
> >>> NR_syscalls macro from asm/unistd.h to uapi/asm/unistd.h. The macro
> >>> name also changed form NR_syscalls to __NR_syscalls for making the
> >>> name convention same across all architecture. While __NR_syscalls
> >>> isn't strictly part of the uapi, having it as part of the generated
> >>> header to simplifies the implementation.
> >>
> >> This macro was in unistd.h in past but it was moved out because it was
> >> causing problem with strace.
> >>
> >> commit 40c2702a02b755e0183b702778331b351f3be20c
> >> Author:     Michal Simek <michal.simek@...inx.com>
> >> AuthorDate: Mon Jul 8 09:50:24 2013 +0200
> >> Commit:     Michal Simek <michal.simek@...inx.com>
> >> CommitDate: Wed Jul 10 07:32:09 2013 +0200
> >>
> >>     microblaze: Move __NR_syscalls from uapi
> >>
> >>
> >> That's why I don't think this is the right thing to do.
> >> I have grepped strace and glibc and none is using this macro that's why
> >> I think it shouldn't be exported via uapi.
> >
> >
> > Thanks for you reply :)
> > Sorry for the delayed response :(
> >
> > I would like to keep __NR_syscalls macro to uapi header in order to simplify
> > the system call table generation script. Otherwise the __NR_syscalls
> > macro need to update manually. That become a problem.
> >
> > Please check the below implementation in uapi file make sense?
> > It is an easy workaround to leave __NR_syscalls macro in uapi/asm/unistd.h
> > and enclose it in #ifdef __KERNEL__
> >
> > ...
> > ...
> > #define __NR_pkey_free  397
> > #define __NR_statx      398
> >
> > #ifdef __KERNEL__
> > #define __NR_syscalls   399
> > #endif
> > ...
> > ...
>
> This should be fine.

Thanks for the confirmation!

- Firoz
>
> M