[Skiboot] [PATCH] core/flash: Allow OPAL flash calls for size equal to flash

[Samuel Mendoza-Jonas]

On Fri, 2017-06-23 at 14:59 +1000, Cyril Bur wrote:
> A bounds checking mistake prevents opal_flash_{read,write,erase} calls
> from having a length equal to the size of the flash. This bug has been
> present since the beginning (e7d1f60e core/flash: Add flash API) of
> these calls.
> 
> Until before d6a5b53f libflash/blocklevel: Add blocklevel_smart_erase()
> 6/4/2017 none of our tools would have performed a single command for the
> full size of the flash. It would still have been possible to persuade
> `dd` to do this by using a block size equal to the size of the flash
> or other mtd related tools.
> 
> Any pflash built with blocklevel_smart_erase() will perform one call to
> Linux and then Skiboot for the size of flash.
> 
> Signed-off-by: Cyril Bur <cyril.bur at au1.ibm.com>

Acked-by: Samuel Mendoza-Jonas <sam at mendozajonas.com>

> ---
> Slight caveat - when pflash does perform a 64MB erase we spend *a lot*
> of time in Skiboot and Linux gets a little bit angry and theres some
> RCU stalling all over the place. It does work, so all it well. I am
> working on an async bandaid over the problem.
> 
>  core/flash.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/core/flash.c b/core/flash.c
> index 793401c9..3150df6f 100644
> --- a/core/flash.c
> +++ b/core/flash.c
> @@ -16,6 +16,7 @@
>  
>  #include <skiboot.h>
>  #include <cpu.h>
> +#include <inttypes.h>
>  #include <lock.h>
>  #include <opal.h>
>  #include <opal-msg.h>
> @@ -342,8 +343,10 @@ static int64_t opal_flash_op(enum flash_op op, uint64_t id, uint64_t offset,
>  		goto err;
>  	}
>  
> -	if (size >= flash->size || offset >= flash->size
> +	if (size > flash->size || offset >= flash->size
>  			|| offset + size > flash->size) {
> +		prlog(PR_DEBUG, "Requested flash op %d beyond flash size %" PRIu64 "\n",
> +				op, flash->size);
>  		rc = OPAL_PARAMETER;
>  		goto err;
>  	}