linux-kernel - Re: [PATCH v9 8/9] arch, mm: wire up memfd

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Message-ID: <X7QFMhQlyBMI1wXE@trantor>
Date:   Tue, 17 Nov 2020 17:15:30 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     Mike Rapoport <rppt@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        Christopher Lameter <cl@...ux.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        David Hildenbrand <david@...hat.com>,
        Elena Reshetova <elena.reshetova@...el.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        James Bottomley <jejb@...ux.ibm.com>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        Matthew Wilcox <willy@...radead.org>,
        Mark Rutland <mark.rutland@....com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Roman Gushchin <guro@...com>, Shuah Khan <shuah@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tycho Andersen <tycho@...ho.ws>, Will Deacon <will@...nel.org>,
        linux-api@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-nvdimm@...ts.01.org, linux-riscv@...ts.infradead.org,
        x86@...nel.org, Palmer Dabbelt <palmerdabbelt@...gle.com>
Subject: Re: [PATCH v9 8/9] arch, mm: wire up memfd_secret system call were
 relevant

On Tue, Nov 17, 2020 at 06:29:31PM +0200, Mike Rapoport wrote:
> From: Mike Rapoport <rppt@...ux.ibm.com>
> 
> Wire up memfd_secret system call on architectures that define
> ARCH_HAS_SET_DIRECT_MAP, namely arm64, risc-v and x86.
> 
> Signed-off-by: Mike Rapoport <rppt@...ux.ibm.com>
> Acked-by: Palmer Dabbelt <palmerdabbelt@...gle.com>
> Acked-by: Arnd Bergmann <arnd@...db.de>
> ---
>  arch/arm64/include/asm/unistd.h        | 2 +-
>  arch/arm64/include/asm/unistd32.h      | 2 ++
>  arch/arm64/include/uapi/asm/unistd.h   | 1 +
>  arch/riscv/include/asm/unistd.h        | 1 +
>  arch/x86/entry/syscalls/syscall_32.tbl | 1 +
>  arch/x86/entry/syscalls/syscall_64.tbl | 1 +
>  include/linux/syscalls.h               | 1 +
>  include/uapi/asm-generic/unistd.h      | 6 +++++-
>  scripts/checksyscalls.sh               | 4 ++++
>  9 files changed, 17 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/unistd.h b/arch/arm64/include/asm/unistd.h
> index 86a9d7b3eabe..949788f5ba40 100644
> --- a/arch/arm64/include/asm/unistd.h
> +++ b/arch/arm64/include/asm/unistd.h
> @@ -38,7 +38,7 @@
>  #define __ARM_NR_compat_set_tls		(__ARM_NR_COMPAT_BASE + 5)
>  #define __ARM_NR_COMPAT_END		(__ARM_NR_COMPAT_BASE + 0x800)
>  
> -#define __NR_compat_syscalls		442
> +#define __NR_compat_syscalls		443
>  #endif
>  
>  #define __ARCH_WANT_SYS_CLONE
> diff --git a/arch/arm64/include/asm/unistd32.h b/arch/arm64/include/asm/unistd32.h
> index 6c1dcca067e0..5279481ec95b 100644
> --- a/arch/arm64/include/asm/unistd32.h
> +++ b/arch/arm64/include/asm/unistd32.h
> @@ -891,6 +891,8 @@ __SYSCALL(__NR_faccessat2, sys_faccessat2)
>  __SYSCALL(__NR_process_madvise, sys_process_madvise)
>  #define __NR_watch_mount 441
>  __SYSCALL(__NR_watch_mount, sys_watch_mount)
> +/* 442 is memfd_secret, it is not implemented for 32-bit */
> +__SYSCALL(442, sys_ni_syscall)

It now behaves correctly for compat but I don't think we need to
increment __NR_compat_syscalls. The compat syscall handler already calls
sys_ni_syscall() if out of range.

So the only arm64 change needed is defining __ARCH_WANT_MEMFD_SECRET
(well, we don't have a use for it yet ;)).

-- 
Catalin