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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Fri, 13 Dec 2019 07:42:43 +0100
Message-ID: <CAK8P3a2Nz10L2pQPE3L5-d0wKGD6BBKCT5HMc4Nyo-56ORSheg@mail.gmail.com>
Subject: Re: [PATCH] MIPS: Add get_thread_area syscall
To:     Guoyun Sun <sunguoyun@loongson.cn>
Cc:     Ralf Baechle <ralf@linux-mips.org>,
        Paul Burton <paulburton@kernel.org>,
        James Hogan <jhogan@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Christian Brauner <christian.brauner@ubuntu.com>,
        Heiko Carstens <heiko.carstens@de.ibm.com>,
        David Howells <dhowells@redhat.com>,
        Firoz Khan <firoz.khan@linaro.org>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        "open list:BROADCOM NVRAM DRIVER" <linux-mips@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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On Fri, Dec 13, 2019 at 7:15 AM Guoyun Sun <sunguoyun@loongson.cn> wrote:
>
> CRIU(https://criu.org/) tools will dump TLS(Thread Local Storage) by
> get_thread_area during checkpoint and restore TLS by set_thread_area during
> restore. without syscall get_thread_area, criu restore will fail on MIPS
> platform.because a variable with GCC __thread is invalid.
>
> The following function will be called when criu restore

> diff --git a/arch/mips/kernel/syscalls/syscall_n32.tbl b/arch/mips/kernel/syscalls/syscall_n32.tbl
> index e7c5ab3..7da83d0 100644
> --- a/arch/mips/kernel/syscalls/syscall_n32.tbl
> +++ b/arch/mips/kernel/syscalls/syscall_n32.tbl
> @@ -374,3 +374,4 @@
>  433    n32     fspick                          sys_fspick
>  434    n32     pidfd_open                      sys_pidfd_open
>  435    n32     clone3                          __sys_clone3
> +436    n32     get_thread_area                 sys_get_thread_area

Please use a number in the arch-specific range below 393. The numbers
at the bottom are meant for syscalls that are common for all
architectures.

        Arnd