Re: [v2] powerpc/powernv: Expose OPAL firmware symbol map

[Michael Ellerman <mpe@ellerman.id.au>]

On Fri, 2014-05-12 at 04:26:17 UTC, Benjamin Herrenschmidt wrote:
> Newer versions of OPAL will provide this, so let's expose it to user
> space so tools like perf can use it to properly decode samples in
> firmware space.
> 
> diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c
> index 06d9076..98f50e8 100644
> --- a/arch/powerpc/platforms/powernv/opal.c
> +++ b/arch/powerpc/platforms/powernv/opal.c
> @@ -61,6 +61,8 @@ static DEFINE_SPINLOCK(opal_notifier_lock);
>  static uint64_t last_notified_mask = 0x0ul;
>  static atomic_t opal_notifier_hold = ATOMIC_INIT(0);
>  static uint32_t opal_heartbeat;
> +static void *opal_symmap;
> +static uint64_t opal_symmap_size;

We shouldn't need these.

The bin_attribute has a size (you set it), you just need to use it in
symbol_map_read(). 

And the attribute also has a private pointer, which you can use for
opal_symmap.

> @@ -608,6 +610,40 @@ static int opal_sysfs_init(void)
>  	return 0;
>  }
>  
> +static ssize_t symbol_map_read(struct file *fp, struct kobject *kobj,
> +			       struct bin_attribute *bin_attr,
> +			       char *buf, loff_t off, size_t count)
> +{
> +	return memory_read_from_buffer(buf, count, &off,
> +				       opal_symmap, opal_symmap_size);

So this would be:

	return memory_read_from_buffer(buf, count, &off,
				       bin_attr->private, bin_attr->size);

> +}
> +
> +static BIN_ATTR_RO(symbol_map, 0);
> +
> +static void opal_export_symmap(void)
> +{
> +	const __be64 *syms;
> +	unsigned int size;
> +	struct device_node *fw;
> +	int rc;
> +
> +	fw = of_find_node_by_path("/ibm,opal/firmware");
> +	if (!fw)
> +		return;
> +	syms = of_get_property(fw, "symbol-map", &size);
> +	if (!syms || size != 2 * sizeof(__be64))
> +		return;
> +
> +	opal_symmap = __va(be64_to_cpu(syms[0]));
> +	opal_symmap_size = be64_to_cpu(syms[1]);

I was going to tell you to use of_property_read_u64_index(), but it doesn't
exist - we can add it one day and clean this up then.

> +	/* Setup attributes */
> +	bin_attr_symbol_map.size = opal_symmap_size;
> +	rc = sysfs_create_bin_file(opal_kobj, &bin_attr_symbol_map);
> +	if (rc)
> +		pr_warn("Error %d creating OPAL symbols file\n", rc);

Can you prefix it please, so:
	pr_warn("opal: Error .."

Or add to the very top of the file:

#define pr_fmt(fmt)    "opal: " fmt

cheers