[PATCH V6 08/10] cxl/cdat: Introduce cdat_hdr_valid()

ira.weiny
2022-02-01T07:20:24Z

From: Ira Weiny <ira.weiny@intel.com>

The CDAT data is protected by a checksum which should be checked when
the CDAT is read to ensure it is valid. In addition the lengths
specified should be checked.

Introduce cdat_hdr_valid() to check the checksum. While at it check and
store the sequence number.

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

---
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/pci.c | 32 ++++++++++++++++++++++++++++++++
2 files changed, 34 insertions(+)

diff --git a/drivers/cxl/cdat.h b/drivers/cxl/cdat.h
index 4722b6bbbaf0..a7725d26f2d2 100644
--- a/drivers/cxl/cdat.h
+++ b/drivers/cxl/cdat.h
@@ -88,10 +88,12 @@
*
* @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/pci.c b/drivers/cxl/pci.c
index 28b973a9e29e..c362c75feed2 100644
--- a/drivers/cxl/pci.c
+++ b/drivers/cxl/pci.c
@@ -586,6 +586,35 @@ static int cxl_setup_doe_devices(struct cxl_dev_state *cxlds)
return 0;
}

+static bool cxl_cdat_hdr_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)
+ return false;
+
+ if (length > cdat->length)
+ 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;
+ }
+
+ for (check = 0, i = 0; i < length; i++)
+ check += data8[i];
+
+ return check == 0;
+}
+
#define CDAT_DOE_REQ(entry_handle) \
(FIELD_PREP(CXL_DOE_TABLE_ACCESS_REQ_CODE, \
CXL_DOE_TABLE_ACCESS_REQ_CODE_READ) | \
@@ -658,6 +687,9 @@ static int cxl_cdat_read_table(struct cxl_dev_state *cxlds,

} while (entry_handle != 0xFFFF);

+ if (!cxl_cdat_hdr_valid(cxlds->dev, cdat))
+ return -EIO;
+
return 0;
}

--
2.31.1