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To: Anshuman Khandual <khandual@linux.vnet.ibm.com>, linuxppc-dev@ozlabs.org
From: Michael Ellerman <mpe@ellerman.id.au>
Cc: mikey@neuling.org
Subject: Re: [V2] powerpc/signal: Add helper function to fetch quad word
 aligned pointer
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Date: Tue, 21 Jul 2015 11:37:53 +1000 (AEST)
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On Mon, 2015-20-07 at 02:58:43 UTC, Anshuman Khandual wrote:
> This patch adds one helper function 'sigcontext_vmx_regs' which computes
> quad word aligned pointer for 'vmx_reserve' array element in sigcontext
> structure making the code more readable.
> 
> diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
> index c7c24d2..bb9c939 100644
> --- a/arch/powerpc/kernel/signal_64.c
> +++ b/arch/powerpc/kernel/signal_64.c
> @@ -74,6 +74,16 @@ static const char fmt64[] = KERN_INFO \
>  	"%s[%d]: bad frame in %s: %016lx nip %016lx lr %016lx\n";
>  
>  /*
> + * This computes quad word aligned pointer for 'vmx_reserve' array element
> + * which is used primarily in assigning to the preceding pointer 'v_regs'
> + * in sigcontext structure.

How about:

  * This computes a quad word aligned pointer inside the vmx_reserve array
  * element. For historical reasons sigcontext might not be quad word aligned,
  * but the location we write the VMX regs to must be. See the comment in
  * sigcontext for more detail.


> + */
> +static elf_vrreg_t __user *sigcontext_vmx_regs(struct sigcontext __user *sc)
> +{
> +	return (elf_vrreg_t __user *) (((unsigned long)sc->vmx_reserve + 15) & ~0xful);
> +}

This doesn't build for ppc64e_defconfig:

  arch/powerpc/kernel/signal_64.c:82:28: error: 'sigcontext_vmx_regs' defined but not used [-Werror=unused-function]
   static elf_vrreg_t __user *sigcontext_vmx_regs(struct sigcontext __user *sc)
                            ^

For now I'll just #ifdef it.

Please do a test build of ppc64e_defconfig in future.

cheers