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

Cyril Bur cyril.bur at au1.ibm.com
Fri Jun 23 14:59:15 AEST 2017

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>
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);
 		goto err;

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