linux-kernel - Re: [PATCH 07/15] ARM: add kexec_file

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Date:   Thu, 10 Jan 2019 16:39:08 +0000
From:   Will Deacon <will.deacon@....com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     y2038@...ts.linaro.org, linux-api@...r.kernel.org,
        linux-kernel@...r.kernel.org, ink@...assic.park.msu.ru,
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Subject: Re: [PATCH 07/15] ARM: add kexec_file_load system call number

On Thu, Jan 10, 2019 at 05:24:27PM +0100, Arnd Bergmann wrote:
> A couple of architectures including arm64 already implement the
> kexec_file_load system call, on many others we have assigned a system
> call number for it, but not implemented it yet.
> 
> Adding the number in arch/arm/ lets us use the system call on arm64
> systems in compat mode, and also reduces the number of differences
> between architectures. If we want to implement kexec_file_load on ARM
> in the future, the number assignment means that kexec tools can already
> be built with the now current set of kernel headers.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  arch/arm/tools/syscall.tbl        | 1 +
>  arch/arm64/include/asm/unistd.h   | 2 +-
>  arch/arm64/include/asm/unistd32.h | 2 ++
>  3 files changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl
> index 86de9eb34296..20ed7e026723 100644
> --- a/arch/arm/tools/syscall.tbl
> +++ b/arch/arm/tools/syscall.tbl
> @@ -415,3 +415,4 @@
>  398	common	rseq			sys_rseq
>  399	common	io_pgetevents		sys_io_pgetevents
>  400	common	migrate_pages		sys_migrate_pages
> +401	common	kexec_file_load		sys_kexec_file_load
> diff --git a/arch/arm64/include/asm/unistd.h b/arch/arm64/include/asm/unistd.h
> index 261216c3336e..2c30e6f145ff 100644
> --- a/arch/arm64/include/asm/unistd.h
> +++ b/arch/arm64/include/asm/unistd.h
> @@ -44,7 +44,7 @@
>  #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		401
> +#define __NR_compat_syscalls		402
>  #endif
>  
>  #define __ARCH_WANT_SYS_CLONE
> diff --git a/arch/arm64/include/asm/unistd32.h b/arch/arm64/include/asm/unistd32.h
> index 355fe2bc035b..19f3f58b6146 100644
> --- a/arch/arm64/include/asm/unistd32.h
> +++ b/arch/arm64/include/asm/unistd32.h
> @@ -823,6 +823,8 @@ __SYSCALL(__NR_rseq, sys_rseq)
>  __SYSCALL(__NR_io_pgetevents, compat_sys_io_pgetevents)
>  #define __NR_migrate_pages 400
>  __SYSCALL(__NR_migrate_pages, sys_migrate_pages)
> +#define __NR_kexec_file_load 401
> +__SYSCALL(__NR_kexec_file_load, sys_kexec_file_load)

Hmm, I wonder if we need a compat wrapper for this, or are we assuming
that the early entry code has already zero-extended the long and pointer
arguments?

Will