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, 18 insertions, 13 deletions

diff --git a/drivers/net/ethernet/sfc/mcdi.c b/drivers/net/ethernet/sfc/mcdi.c
index d6d1ff19c918..3f55b16265fc 100644
--- a/drivers/net/ethernet/sfc/mcdi.c
+++ b/drivers/net/ethernet/sfc/mcdi.c
@@ -67,7 +67,7 @@ void efx_mcdi_init(struct efx_nic *efx)
 }
 
 static void efx_mcdi_copyin(struct efx_nic *efx, unsigned cmd,
-			    const u8 *inbuf, size_t inlen)
+			    const efx_dword_t *inbuf, size_t inlen)
 {
 	struct efx_mcdi_iface *mcdi = efx_mcdi(efx);
 	unsigned pdu = FR_CZ_MC_TREG_SMEM + MCDI_PDU(efx);
@@ -75,9 +75,10 @@ static void efx_mcdi_copyin(struct efx_nic *efx, unsigned cmd,
 	unsigned int i;
 	efx_dword_t hdr;
 	u32 xflags, seqno;
+	unsigned int inlen_dw = DIV_ROUND_UP(inlen, 4);
 
 	BUG_ON(atomic_read(&mcdi->state) == MCDI_STATE_QUIESCENT);
-	BUG_ON(inlen & 3 || inlen >= MC_SMEM_PDU_LEN);
+	BUG_ON(inlen > MCDI_CTL_SDU_LEN_MAX_V1);
 
 	seqno = mcdi->seqno & SEQ_MASK;
 	xflags = 0;
@@ -94,8 +95,8 @@ static void efx_mcdi_copyin(struct efx_nic *efx, unsigned cmd,
 
 	efx_writed(efx, &hdr, pdu);
 
-	for (i = 0; i < inlen; i += 4)
-		_efx_writed(efx, *((__le32 *)(inbuf + i)), pdu + 4 + i);
+	for (i = 0; i < inlen_dw; i++)
+		efx_writed(efx, &inbuf[i], pdu + 4 + 4 * i);
 
 	/* Ensure the payload is written out before the header */
 	wmb();
@@ -104,17 +105,19 @@ static void efx_mcdi_copyin(struct efx_nic *efx, unsigned cmd,
 	_efx_writed(efx, (__force __le32) 0x45789abc, doorbell);
 }
 
-static void efx_mcdi_copyout(struct efx_nic *efx, u8 *outbuf, size_t outlen)
+static void
+efx_mcdi_copyout(struct efx_nic *efx, efx_dword_t *outbuf, size_t outlen)
 {
 	struct efx_mcdi_iface *mcdi = efx_mcdi(efx);
 	unsigned int pdu = FR_CZ_MC_TREG_SMEM + MCDI_PDU(efx);
+	unsigned int outlen_dw = DIV_ROUND_UP(outlen, 4);
 	int i;
 
 	BUG_ON(atomic_read(&mcdi->state) == MCDI_STATE_QUIESCENT);
-	BUG_ON(outlen & 3 || outlen >= MC_SMEM_PDU_LEN);
+	BUG_ON(outlen > MCDI_CTL_SDU_LEN_MAX_V1);
 
-	for (i = 0; i < outlen; i += 4)
-		*((__le32 *)(outbuf + i)) = _efx_readd(efx, pdu + 4 + i);
+	for (i = 0; i < outlen_dw; i++)
+		efx_readd(efx, &outbuf[i], pdu + 4 + 4 * i);
 }
 
 static int efx_mcdi_poll(struct efx_nic *efx)
@@ -328,7 +331,8 @@ static void efx_mcdi_ev_cpl(struct efx_nic *efx, unsigned int seqno,
 }
 
 int efx_mcdi_rpc(struct efx_nic *efx, unsigned cmd,
-		 const u8 *inbuf, size_t inlen, u8 *outbuf, size_t outlen,
+		 const efx_dword_t *inbuf, size_t inlen,
+		 efx_dword_t *outbuf, size_t outlen,
 		 size_t *outlen_actual)
 {
 	efx_mcdi_rpc_start(efx, cmd, inbuf, inlen);
@@ -336,8 +340,8 @@ int efx_mcdi_rpc(struct efx_nic *efx, unsigned cmd,
 				   outbuf, outlen, outlen_actual);
 }
 
-void efx_mcdi_rpc_start(struct efx_nic *efx, unsigned cmd, const u8 *inbuf,
-			size_t inlen)
+void efx_mcdi_rpc_start(struct efx_nic *efx, unsigned cmd,
+			const efx_dword_t *inbuf, size_t inlen)
 {
 	struct efx_mcdi_iface *mcdi = efx_mcdi(efx);
 
@@ -354,7 +358,8 @@ void efx_mcdi_rpc_start(struct efx_nic *efx, unsigned cmd, const u8 *inbuf,
 }
 
 int efx_mcdi_rpc_finish(struct efx_nic *efx, unsigned cmd, size_t inlen,
-			u8 *outbuf, size_t outlen, size_t *outlen_actual)
+			efx_dword_t *outbuf, size_t outlen,
+			size_t *outlen_actual)
 {
 	struct efx_mcdi_iface *mcdi = efx_mcdi(efx);
 	int rc;
@@ -393,7 +398,7 @@ int efx_mcdi_rpc_finish(struct efx_nic *efx, unsigned cmd, size_t inlen,
 
 		if (rc == 0) {
 			efx_mcdi_copyout(efx, outbuf,
-					 min(outlen, mcdi->resplen + 3) & ~0x3);
+					 min(outlen, mcdi->resplen));
 			if (outlen_actual != NULL)
 				*outlen_actual = resplen;
 		} else if (cmd == MC_CMD_REBOOT && rc == -EIO)