Re: [PATCH 07/15] ARM: add kexec_file_load system call number

From: Will Deacon <will.deacon@arm.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: y2038@lists.linaro.org, linux-api@vger.kernel.org,
	linux-kernel@vger.kernel.org, ink@jurassic.park.msu.ru,
	mattst88@gmail.com, linux@armlinux.org.uk,
	catalin.marinas@arm.com, tony.luck@intel.com,
	fenghua.yu@intel.com, geert@linux-m68k.org, monstr@monstr.eu,
	paul.burton@mips.com, deller@gmx.de, mpe@ellerman.id.au,
	schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com,
	dalias@libc.org, davem@davemloft.net, luto@kernel.org,
	tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
	x86@kernel.org, jcmvbkbc@gmail.com, firoz.khan@linaro.org,
	ebiederm@xmission.com, deepa.kernel@gmail.com,
	linux@dominikbrodowski.net, akpm@linux-foundation.org,
	dave@stgolabs.net, linux-alpha@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org,
	linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org,
	linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	linux-s390@vger.kernel.org, linux-sh@vger.kernel.org,
	sparclinux@vger.kernel.org
Subject: Re: [PATCH 07/15] ARM: add kexec_file_load system call number
Date: Thu, 10 Jan 2019 16:39:08 +0000	[thread overview]
Message-ID: <20190110163908.GC31683@fuggles.cambridge.arm.com> (raw)
In-Reply-To: <20190110162435.309262-8-arnd@arndb.de>

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@arndb.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