[PATCH V11 6/8] cxl/port: Introduce cxl_cdat_valid()

[ira . weiny]

From: Ira Weiny <ira.weiny@xxxxxxxxx>

The CDAT data is protected by a checksum and should be the proper
length.

Introduce cxl_cdat_valid() to validate the data.  While at it check and
store the sequence number.

Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx>

---
Changes from V8
	Move code to cxl/core/pci.c

Changes from V6
	Change name to cxl_cdat_valid() as this validates all the CDAT
		data not just the header
	Add error and debug prints

Changes from V5
	New patch, split out
	Update cdat_hdr_valid()
		Remove revision and cs field parsing
			There is no point in these
		Add seq check and debug print.
---
 drivers/cxl/cdat.h     |  2 ++
 drivers/cxl/core/pci.c | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/drivers/cxl/cdat.h b/drivers/cxl/cdat.h
index c6a48ab326bf..39eb561081f2 100644
--- a/drivers/cxl/cdat.h
+++ b/drivers/cxl/cdat.h
@@ -91,10 +91,12 @@
  *
  * @table: cache of CDAT table
  * @length: length of cached CDAT table
+ * @seq: Last read Sequence number of the CDAT table
  */
 struct cxl_cdat {
 	void *table;
 	size_t length;
+	u32 seq;
 };
 
 #endif /* !__CXL_CDAT_H__ */
diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
index 84dc82f7dff0..cb70287e2984 100644
--- a/drivers/cxl/core/pci.c
+++ b/drivers/cxl/core/pci.c
@@ -531,6 +531,40 @@ static int cxl_cdat_get_length(struct device *dev,
 	return rc;
 }
 
+static bool cxl_cdat_valid(struct device *dev, struct cxl_cdat *cdat)
+{
+	u32 *table = cdat->table;
+	u8 *data8 = cdat->table;
+	u32 length, seq;
+	u8 check;
+	int i;
+
+	length = FIELD_GET(CDAT_HEADER_DW0_LENGTH, table[0]);
+	if ((length < CDAT_HEADER_LENGTH_BYTES) || (length > cdat->length)) {
+		dev_err(dev, "CDAT Invalid length %u (%zu-%zu)\n", length,
+			CDAT_HEADER_LENGTH_BYTES, cdat->length);
+		return false;
+	}
+
+	for (check = 0, i = 0; i < length; i++)
+		check += data8[i];
+
+	dev_dbg(dev, "CDAT length %u CS %u\n", length, check);
+	if (check != 0) {
+		dev_err(dev, "CDAT Invalid checksum %u\n", check);
+		return false;
+	}
+
+	seq = FIELD_GET(CDAT_HEADER_DW3_SEQUENCE, table[3]);
+	/* Store the sequence for now. */
+	if (cdat->seq != seq) {
+		dev_info(dev, "CDAT seq change %x -> %x\n", cdat->seq, seq);
+		cdat->seq = seq;
+	}
+
+	return true;
+}
+
 static int cxl_cdat_read_table(struct device *dev,
 			       struct pci_doe_mb *cdat_mb,
 			       struct cxl_cdat *cdat)
@@ -578,6 +612,8 @@ static int cxl_cdat_read_table(struct device *dev,
 
 	} while (entry_handle != CXL_DOE_TABLE_ACCESS_LAST_ENTRY);
 
+	if (!rc && !cxl_cdat_valid(dev, cdat))
+		return -EIO;
 	return rc;
 }
 
-- 
2.35.1