linux-kernel - Re: [PATCH 13/18] kernel: add kcompat_sys

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Message-ID: <20180514171427.qyietn3fhilwokb2@lakrids.cambridge.arm.com>
Date:   Mon, 14 May 2018 18:14:28 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, catalin.marinas@....com,
        dave.martin@....com, james.morse@....com,
        linux@...inikbrodowski.net, linux-fsdevel@...r.kernel.org,
        marc.zyngier@....com, viro@...iv.linux.org.uk, will.deacon@....com
Subject: Re: [PATCH 13/18] kernel: add kcompat_sys_{f,}statfs64()

On Mon, May 14, 2018 at 10:46:35AM +0100, Mark Rutland wrote:
> Using this helper allows us to avoid the in-kernel calls to the
> compat_sys_{f,}statfs64() sycalls, as are necessary for parameter
> mangling in arm64's compat handling.
> 
> Following the example of ksys_* functions, kcompat_sys_* functions are
> intended to be a drop-in replacement for their compat_sys_*
> counterparts, with the same calling convention.
> 
> This is necessary to enable conversion of arm64's syscall handling to
> use pt_regs wrappers.

> diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
> index 6723ea51ec99..e0bf3e4bb897 100644
> --- a/include/linux/syscalls.h
> +++ b/include/linux/syscalls.h
> @@ -59,6 +59,7 @@ struct tms;
>  struct utimbuf;
>  struct mq_attr;
>  struct compat_stat;
> +struct compat_statfs64;
>  struct compat_timeval;
>  struct robust_list_head;
>  struct getcpu_cache;
> @@ -1150,6 +1151,13 @@ unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
>  ssize_t ksys_readahead(int fd, loff_t offset, size_t count);
>  unsigned int ksys_personality(unsigned int personality);
>  
> +#ifdef CONFIG_COMPAT
> +int kcompat_sys_statfs64(const char __user * pathname, compat_size_t sz,
> +		     struct compat_statfs64 __user * buf);
> +int kcompat_sys_fstatfs64(unsigned int fd, compat_size_t sz,
> +			  struct compat_statfs64 __user * buf);
> +#endif

I've moved these to <linux/compat.h>, so that they live with the rest of
the compat syscall stuff. That should avoid build failures the kbuild
test robot picked up where compat_size_t wasn't dfined.

Thanks,
Mark.