[PATCH skiboot/pflash] libflash/libffs: Detect first byte flash corruption

[Cyril Bur]

This patch is not for upstream but currently this unknown corruption is
making life difficult.

Perhaps it can be useful at least temporarily.

Feel free to remove the option to continue and leave just the
information message.

Signed-off-by: Cyril Bur <cyril.bur at au1.ibm.com>
---
 libflash/libffs.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/libflash/libffs.c b/libflash/libffs.c
index 7ae9050e..dce6237e 100644
--- a/libflash/libffs.c
+++ b/libflash/libffs.c
@@ -260,6 +260,35 @@ int ffs_init(uint32_t offset, uint32_t max_size, struct blocklevel_device *bl,
 
 	/* Convert and check flash header */
 	rc = ffs_check_convert_header(&f->hdr, &raw_hdr);
+	/*
+	 * A bug on witherspoon of currently unknown origin causes
+	 * corruption of the first byte of flash. This is by no means
+	 * a fix and should never go upstream but may prove helpful.
+	 */
+	if (rc == FFS_ERR_BAD_MAGIC) {
+		/*
+		 * We can set the first byte to what we know it should be
+		 * and try to check and convert header again. If it
+		 * succeeds there is a very high chance this is the
+		 * problem.
+		 */
+		*(char *)&raw_hdr = 'P';
+		rc = ffs_check_convert_header(&f->hdr, &raw_hdr);
+		if (rc) {
+			/*
+			 * Turn it back into BAD_MAGIC, the flash obviously
+			 * has bigger problems.
+			 */
+			rc = FFS_ERR_BAD_MAGIC;
+		} else {
+			FL_ERR("FFS: Detected corruption of the first byte of flash.\n");
+			FL_ERR("     Recommend hard power cycling the entire machine\n");
+			FL_ERR("     Continuing is dangerous!\n");
+			FL_ERR("     Continuing in 10 seconds\n");
+			sleep(10);
+			rc = 0;
+		}
+	}
 	if (rc) {
 		FL_INF("FFS: Flash header not found. Code: %d\n", rc);
 		goto out;
-- 
2.13.2