sfc: Ensure MCDI buffers, but not lengths, are dword aligned

We currently require that MCDI request and response lengths are
multiples of 4 bytes, because we will copy dwords in and out of shared
memory and we want to be sure we won't read or write out of bounds.
But all we really need to know is that there is sufficient padding for
that.  Also, we should ensure that buffers are dword-aligned, as on
some architectures misaligned access will result in data corruption or
a crash.

Change the buffer type to array-of-efx_dword_t and remove the
requirement that the lengths are multiples of 4.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

1 files changed, 23 insertions, 13 deletions

diff --git a/drivers/net/ethernet/sfc/mcdi.h b/drivers/net/ethernet/sfc/mcdi.h
index f8ab64f0efb1..28657a186761 100644
--- a/drivers/net/ethernet/sfc/mcdi.h
+++ b/drivers/net/ethernet/sfc/mcdi.h
@@ -67,16 +67,18 @@ struct efx_mcdi_mon {
 
 extern void efx_mcdi_init(struct efx_nic *efx);
 
-extern int efx_mcdi_rpc(struct efx_nic *efx, unsigned cmd, const u8 *inbuf,
-			size_t inlen, u8 *outbuf, size_t outlen,
+extern int efx_mcdi_rpc(struct efx_nic *efx, unsigned cmd,
+			const efx_dword_t *inbuf, size_t inlen,
+			efx_dword_t *outbuf, size_t outlen,
 			size_t *outlen_actual);
 
 extern void efx_mcdi_rpc_start(struct efx_nic *efx, unsigned cmd,
-			       const u8 *inbuf, size_t inlen);
+			       const efx_dword_t *inbuf, size_t inlen);
 extern int efx_mcdi_rpc_finish(struct efx_nic *efx, unsigned cmd, size_t inlen,
-			       u8 *outbuf, size_t outlen,
+			       efx_dword_t *outbuf, size_t outlen,
 			       size_t *outlen_actual);
 
+
 extern int efx_mcdi_poll_reboot(struct efx_nic *efx);
 extern void efx_mcdi_mode_poll(struct efx_nic *efx);
 extern void efx_mcdi_mode_event(struct efx_nic *efx);
@@ -85,14 +87,21 @@ extern void efx_mcdi_process_event(struct efx_channel *channel,
 				   efx_qword_t *event);
 extern void efx_mcdi_sensor_event(struct efx_nic *efx, efx_qword_t *ev);
 
+/* We expect that 16- and 32-bit fields in MCDI requests and responses
+ * are appropriately aligned.  Also, on Siena we must copy to the MC
+ * shared memory strictly 32 bits at a time, so add any necessary
+ * padding.
+ */
 #define MCDI_DECLARE_BUF(_name, _len)					\
-	u8 _name[ALIGN(_len, 4)]
+	efx_dword_t _name[DIV_ROUND_UP(_len, 4)]
 #define _MCDI_PTR(_buf, _offset)					\
 	((u8 *)(_buf) + (_offset))
 #define MCDI_PTR(_buf, _field)						\
 	_MCDI_PTR(_buf, MC_CMD_ ## _field ## _OFST)
+#define _MCDI_CHECK_ALIGN(_ofst, _align)				\
+	((_ofst) + BUILD_BUG_ON_ZERO((_ofst) & (_align - 1)))
 #define _MCDI_DWORD(_buf, _field)					\
-	((efx_dword_t *)MCDI_PTR(_buf, _field))
+	((_buf) + (_MCDI_CHECK_ALIGN(MC_CMD_ ## _field ## _OFST, 4) >> 2))
 
 #define MCDI_SET_DWORD(_buf, _field, _value)				\
 	EFX_POPULATE_DWORD_1(*_MCDI_DWORD(_buf, _field), EFX_DWORD_0, _value)
@@ -109,22 +118,23 @@ extern void efx_mcdi_sensor_event(struct efx_nic *efx, efx_qword_t *ev);
 		(MC_CMD_ ## _type ## _ ## _field ## _LBN & 0x1f) +	\
 		MC_CMD_ ## _type ## _ ## _field ## _WIDTH - 1)
 
-#define _MCDI_ARRAY_PTR(_buf, _field, _index)				\
-	(MCDI_PTR(_buf, _field) +					\
-	 (_index) * MC_CMD_ ## _field ## _LEN)
+#define _MCDI_ARRAY_PTR(_buf, _field, _index, _align)			\
+	(_MCDI_PTR(_buf, _MCDI_CHECK_ALIGN(MC_CMD_ ## _field ## _OFST, _align))\
+	 + (_index) * _MCDI_CHECK_ALIGN(MC_CMD_ ## _field ## _LEN, _align))
 #define MCDI_DECLARE_STRUCT_PTR(_name)					\
-	u8 *_name
-#define MCDI_ARRAY_STRUCT_PTR _MCDI_ARRAY_PTR
+	efx_dword_t *_name
+#define MCDI_ARRAY_STRUCT_PTR(_buf, _field, _index)			\
+	((efx_dword_t *)_MCDI_ARRAY_PTR(_buf, _field, _index, 4))
 #define MCDI_VAR_ARRAY_LEN(_len, _field)				\
 	min_t(size_t, MC_CMD_ ## _field ## _MAXNUM,			\
 	      ((_len) - MC_CMD_ ## _field ## _OFST) / MC_CMD_ ## _field ## _LEN)
 #define MCDI_ARRAY_WORD(_buf, _field, _index)				\
 	(BUILD_BUG_ON_ZERO(MC_CMD_ ## _field ## _LEN != 2) +		\
 	 le16_to_cpu(*(__force const __le16 *)				\
-		     _MCDI_ARRAY_PTR(_buf, _field, _index)))
+		     _MCDI_ARRAY_PTR(_buf, _field, _index, 2)))
 #define _MCDI_ARRAY_DWORD(_buf, _field, _index)				\
 	(BUILD_BUG_ON_ZERO(MC_CMD_ ## _field ## _LEN != 4) +		\
-	 (efx_dword_t *)_MCDI_ARRAY_PTR(_buf, _field, _index))
+	 (efx_dword_t *)_MCDI_ARRAY_PTR(_buf, _field, _index, 4))
 #define MCDI_SET_ARRAY_DWORD(_buf, _field, _index, _value)		\
 	EFX_SET_DWORD_FIELD(*_MCDI_ARRAY_DWORD(_buf, _field, _index),	\
 			    EFX_DWORD_0, _value)