[PATCH v2 02/21] cxl: Add checksum verification to CDAT from CXL

[Dave Jiang <dave.jiang@intel.com>]

A CDAT table is available from a CXL device. The table is read by the
driver and cached in software. With the CXL subsystem needing to parse the
CDAT table, the checksum should be verified. Add checksum verification
after the CDAT table is read from device.

Signed-off-by: Dave Jiang <dave.jiang@intel.com>

---
v2:
- Drop ACPI checksum export and just use local verification. (Dan)
---
 drivers/cxl/core/pci.c |   16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
index 25b7e8125d5d..e0d5e6525c0d 100644
--- a/drivers/cxl/core/pci.c
+++ b/drivers/cxl/core/pci.c
@@ -528,6 +528,16 @@ static int cxl_cdat_read_table(struct device *dev,
 	return 0;
 }
 
+static unsigned char cdat_checksum(void *buf, size_t size)
+{
+	unsigned char sum, *data = buf;
+	size_t i;
+
+	for (sum = 0, i = 0; i < size; i++)
+		sum += data[i];
+	return 0 - sum;
+}
+
 /**
  * read_cdat_data - Read the CDAT data on this port
  * @port: Port to read data from
@@ -573,6 +583,12 @@ void read_cdat_data(struct cxl_port *port)
 	}
 
 	port->cdat.table = cdat_table + sizeof(__le32);
+	if (cdat_checksum(port->cdat.table, cdat_length)) {
+		/* Don't leave table data allocated on error */
+		devm_kfree(dev, cdat_table);
+		dev_err(dev, "CDAT data checksum error\n");
+	}
+
 	port->cdat.length = cdat_length;
 }
 EXPORT_SYMBOL_NS_GPL(read_cdat_data, CXL);