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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Thu, 10 Jan 2019 18:14:50 +0100
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Subject: Re: [PATCH 07/15] ARM: add kexec_file_load system call number
To:     Will Deacon <will.deacon@arm.com>
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On Thu, Jan 10, 2019 at 5:39 PM Will Deacon <will.deacon@arm.com> wrote:
>
> > 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?

Yes, that is generally the assumption for compat syscalls.

s390 needs some extra magic to do a 31-to-64 extension on pointer
arguments, and I think sometimes we need a special wrapper to
do sign-extension of 32-bit arguments into 64-bit, but the arguments
here should not need that.

     Arnd