[PATCH 3/4] fpga mgr: zynq: Add support for encrypted bitstreams

Moritz Fischer
2016-11-07T00:13:25Z

Add new flag FPGA_MGR_DECRYPT_BISTREAM as well as a matching
capability FPGA_MGR_CAP_DECRYPT to allow for on-the-fly
decryption of an encrypted bitstream.

If the system is not booted in secure mode AES & HMAC units
are disabled by the boot ROM, therefore the capability
is not available.

Signed-off-by: Moritz Fischer <moritz.fischer@ettus.com>
Cc: Alan Tull <atull@opensource.altera.com>
Cc: Michal Simek <michal.simek@xilinx.com>
Cc: S?ren Brinkmann <soren.brinkmann@xilinx.com>
Cc: linux-kernel at vger.kernel.org
Cc: linux-arm-kernel at lists.infradead.org
---
drivers/fpga/fpga-mgr.c | 7 +++++++
drivers/fpga/zynq-fpga.c | 21 +++++++++++++++++++--
include/linux/fpga/fpga-mgr.h | 2 ++
3 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/drivers/fpga/fpga-mgr.c b/drivers/fpga/fpga-mgr.c
index 98230b7..e4d08e1 100644
--- a/drivers/fpga/fpga-mgr.c
+++ b/drivers/fpga/fpga-mgr.c
@@ -61,6 +61,12 @@ int fpga_mgr_buf_load(struct fpga_manager *mgr, u32 flags, const char *buf,
return -ENOTSUPP;
}

+ if (flags & FPGA_MGR_DECRYPT_BITSTREAM &&
+ !fpga_mgr_has_cap(FPGA_MGR_CAP_DECRYPT, mgr->caps)) {
+ dev_err(dev, "Bitstream decryption not supported\n");
+ return -ENOTSUPP;
+ }
+
/*
* Call the low level driver's write_init function. This will do the
* device-specific things to get the FPGA into the state where it is
@@ -170,6 +176,7 @@ static const char * const state_str[] = {
static const char * const cap_str[] = {
[FPGA_MGR_CAP_FULL_RECONF] = "Full reconfiguration",
[FPGA_MGR_CAP_PARTIAL_RECONF] = "Partial reconfiguration",
+ [FPGA_MGR_CAP_DECRYPT] = "Decrypt bitstream on the fly",
};

static ssize_t name_show(struct device *dev,
diff --git a/drivers/fpga/zynq-fpga.c b/drivers/fpga/zynq-fpga.c
index 1d37ff0..0aa4705 100644
--- a/drivers/fpga/zynq-fpga.c
+++ b/drivers/fpga/zynq-fpga.c
@@ -71,6 +71,10 @@
#define CTRL_PCAP_PR_MASK BIT(27)
/* Enable PCAP */
#define CTRL_PCAP_MODE_MASK BIT(26)
+/* Needed to reduce clock rate for secure config */
+#define CTRL_PCAP_RATE_EN_MASK BIT(25)
+/* System booted in secure mode */
+#define CTRL_SEC_EN_MASK BIT(7)

/* Miscellaneous Control Register bit definitions */
/* Internal PCAP loopback */
@@ -252,12 +256,20 @@ static int zynq_fpga_ops_write_init(struct fpga_manager *mgr, u32 flags,

/* set configuration register with following options:
* - enable PCAP interface
- * - set throughput for maximum speed
+ * - set throughput for maximum speed (if we're not decrypting)
* - set CPU in user mode
*/
ctrl = zynq_fpga_read(priv, CTRL_OFFSET);
- zynq_fpga_write(priv, CTRL_OFFSET,
+ if (flags & FPGA_MGR_DECRYPT_BITSTREAM) {
+ zynq_fpga_write(priv, CTRL_OFFSET,
+ (CTRL_PCAP_PR_MASK | CTRL_PCAP_MODE_MASK |
+ CTRL_PCAP_RATE_EN_MASK | ctrl));
+
+ } else {
+ ctrl &= ~CTRL_PCAP_RATE_EN_MASK;
+ zynq_fpga_write(priv, CTRL_OFFSET,
(CTRL_PCAP_PR_MASK | CTRL_PCAP_MODE_MASK | ctrl));
+ }

/* check that we have room in the command queue */
status = zynq_fpga_read(priv, STATUS_OFFSET);
@@ -412,6 +424,7 @@ static int zynq_fpga_probe(struct platform_device *pdev)
struct resource *res;
fpga_mgr_cap_mask_t caps;
int err;
+ u32 tmp;

priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
if (!priv)
@@ -466,6 +479,10 @@ static int zynq_fpga_probe(struct platform_device *pdev)
fpga_mgr_cap_set(FPGA_MGR_CAP_FULL_RECONF, caps);
fpga_mgr_cap_set(FPGA_MGR_CAP_PARTIAL_RECONF, caps);

+ /* only works if we booted in secure mode */
+ tmp = zynq_fpga_read(priv, CTRL_OFFSET);
+ if (tmp & CTRL_SEC_EN_MASK)
+ fpga_mgr_cap_set(FPGA_MGR_CAP_DECRYPT, caps);

err = fpga_mgr_register(dev, "Xilinx Zynq FPGA Manager",
&zynq_fpga_ops, caps, priv);
diff --git a/include/linux/fpga/fpga-mgr.h b/include/linux/fpga/fpga-mgr.h
index 9bb96a5..aabe258 100644
--- a/include/linux/fpga/fpga-mgr.h
+++ b/include/linux/fpga/fpga-mgr.h
@@ -68,10 +68,12 @@ enum fpga_mgr_states {
*/
#define FPGA_MGR_PARTIAL_RECONFIG BIT(0)
#define FPGA_MGR_FULL_RECONFIG BIT(1)
+#define FPGA_MGR_DECRYPT_BITSTREAM BIT(2)

enum fpga_mgr_capability {
FPGA_MGR_CAP_PARTIAL_RECONF,
FPGA_MGR_CAP_FULL_RECONF,
+ FPGA_MGR_CAP_DECRYPT,

/* last capability type for creation of the capabilities mask */
FPGA_MGR_CAP_END,
--
2.10.0