linux-kernel - Re: [PATCH 05/11] powerpc: Rework syscall_get

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Date:	Mon, 27 Jul 2015 11:50:33 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Michael Ellerman <mpe@...erman.id.au>
Cc:	"linuxppc-dev@...abs.org" <linuxppc-dev@...abs.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andy Lutomirski <luto@...capital.net>,
	Will Drewry <wad@...omium.org>, strosake@...ux.vnet.ibm.com,
	bogdan.purcareata@...escale.com
Subject: Re: [PATCH 05/11] powerpc: Rework syscall_get_arguments() so there is
 only one loop

On Thu, Jul 23, 2015 at 3:21 AM, Michael Ellerman <mpe@...erman.id.au> wrote:
> Currently syscall_get_arguments() has two loops, one for compat and one
> for regular tasks. In prepartion for the next patch, which changes which
> registers we use, switch it to only have one loop, so we only have one
> place to update.
>
> Signed-off-by: Michael Ellerman <mpe@...erman.id.au>

Reviewed-by: Kees Cook <keescook@...omium.org>

-Kees

> ---
>  arch/powerpc/include/asm/syscall.h | 19 ++++++++-----------
>  1 file changed, 8 insertions(+), 11 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/syscall.h b/arch/powerpc/include/asm/syscall.h
> index cabe90133e69..403e2303fe18 100644
> --- a/arch/powerpc/include/asm/syscall.h
> +++ b/arch/powerpc/include/asm/syscall.h
> @@ -64,19 +64,16 @@ static inline void syscall_get_arguments(struct task_struct *task,
>                                          unsigned int i, unsigned int n,
>                                          unsigned long *args)
>  {
> +       unsigned long mask = -1UL;
> +
>         BUG_ON(i + n > 6);
> -#ifdef CONFIG_PPC64
> -       if (test_tsk_thread_flag(task, TIF_32BIT)) {
> -               /*
> -                * Zero-extend 32-bit argument values.  The high bits are
> -                * garbage ignored by the actual syscall dispatch.
> -                */
> -               while (n-- > 0)
> -                       args[n] = (u32) regs->gpr[3 + i + n];
> -               return;
> -       }
> +
> +#ifdef CONFIG_COMPAT
> +       if (test_tsk_thread_flag(task, TIF_32BIT))
> +               mask = 0xffffffff;
>  #endif
> -       memcpy(args, &regs->gpr[3 + i], n * sizeof(args[0]));
> +       while (n--)
> +               args[n] = regs->gpr[3 + i + n] & mask;
>  }
>
>  static inline void syscall_set_arguments(struct task_struct *task,
> --
> 2.1.0
>



-- 
Kees Cook
Chrome OS Security
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