Subject: Re: [UDATED PATCH] Cell OProfile: Incorrect local array size in activate spu profiling function

From: Michael Ellerman <[email-masked]>
Date: Wed, 29 Oct 2008 11:51:54 +1100

On Tue, 2008-10-28 at 08:17 -0700, Carl Love wrote:
> Updated the patch to address comments by Michael Ellerman.  
> Specifically, changed upper limit in for loop to 
> ARRAY_SIZE() macro and added a check to make sure the 
> number of events specified by the user, which is used as
> the max for indexing various arrays, is no bigger then the
> declared size of the arrays.
> 
> The size of the pm_signal_local array should be equal to the
> number of SPUs being configured in the array.  Currently, the
> array is of size 4 (NR_PHYS_CTRS) but being indexed by a for 
> loop from 0 to 7 (NUM_SPUS_PER_NODE).  
> 
> Signed-off-by: Carl Love <[email-masked]>
> 
> 
> Index: Cell_kernel_10_24_2008/arch/powerpc/oprofile/op_model_cell.c
> ===================================================================
> --- Cell_kernel_10_24_2008.orig/arch/powerpc/oprofile/op_model_cell.c
> +++ Cell_kernel_10_24_2008/arch/powerpc/oprofile/op_model_cell.c
> @@ -582,6 +582,13 @@ static int cell_reg_setup(struct op_coun
>  
>  	num_counters = num_ctrs;
>  
> +	if (unlikely(num_ctrs > NR_PHYS_CTRS)) {
> +		printk(KERN_ERR
> +		       "%s: Oprofile, number of specified events " \
> +		       "exceeds number of physical counters\n",
> +		       __func__);
> +		return -EIO;
> +	}

I wouldn't bother with the unlikely, but whatever, looks good.

>  	pm_regs.group_control = 0;
>  	pm_regs.debug_bus_control = 0;
>  
> @@ -830,13 +837,13 @@ static int calculate_lfsr(int n)
>  static int pm_rtas_activate_spu_profiling(u32 node)
>  {
>  	int ret, i;
> -	struct pm_signal pm_signal_local[NR_PHYS_CTRS];
> +	struct pm_signal pm_signal_local[NUM_SPUS_PER_NODE];
>  
>  	/*
>  	 * Set up the rtas call to configure the debug bus to
>  	 * route the SPU PCs.  Setup the pm_signal for each SPU
>  	 */
> -	for (i = 0; i < NUM_SPUS_PER_NODE; i++) {
> +	for (i = 0; i < ARRAY_SIZE(pm_signal_local); i++) {
>  		pm_signal_local[i].cpu = node;
>  		pm_signal_local[i].signal_group = 41;
>  		/* spu i on word (i/2) */

Looks good, but ..

You should patch the call to rtas_ibm_cbe_perftools() as well, like:

        ret = rtas_ibm_cbe_perftools(SUBFUNC_ACTIVATE,
                                     PASSTHRU_ENABLE, pm_signal_local,
				     sizeof(pm_signal_local));

cheers

-- 
Michael Ellerman
OzLabs, IBM Australia Development Lab

wwweb: http://michael.ellerman.id.au
phone: +61 2 6212 1183 (tie line 70 21183)

We do not inherit the earth from our ancestors,
we borrow it from our children. - S.M.A.R.T Person