Commit 437c78f9 authored by Alex Elder's avatar Alex Elder Committed by David S. Miller
Browse files

net: ipa: avoid 64-bit modulus 



It is possible for a 32 bit x86 build to use a 64 bit DMA address.

There are two remaining spots where the IPA driver does a modulo
operation to check alignment of a DMA address, and under certain
conditions this can lead to a build error on i386 (at least).

The alignment checks we're doing are for power-of-2 values, and this
means the lower 32 bits of the DMA address can be used.  This ensures
both operands to the modulo operator are 32 bits wide.

Reported-by: default avatarRandy Dunlap <rdunlap@infradead.org>
Signed-off-by: default avatarAlex Elder <elder@linaro.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent ed97143e

drivers/net/ipa/gsi.c

+7 −4
Original line number Diff line number Diff line
@@ -1436,15 +1436,18 @@ static void gsi_evt_ring_rx_update(struct gsi_evt_ring *evt_ring, u32 index) 
/* Initialize a ring, including allocating DMA memory for its entries */

static int gsi_ring_alloc(struct gsi *gsi, struct gsi_ring *ring, u32 count)

{

	size_t size = count * GSI_RING_ELEMENT_SIZE;

	u32 size = count * GSI_RING_ELEMENT_SIZE;

	struct device *dev = gsi->dev;

	dma_addr_t addr;



	/* Hardware requires a 2^n ring size, with alignment equal to size */

	/* Hardware requires a 2^n ring size, with alignment equal to size.

	 * The size is a power of 2, so we can check alignment using just

	 * the bottom 32 bits for a DMA address of any size.

	 */

	ring->virt = dma_alloc_coherent(dev, size, &addr, GFP_KERNEL);

	if (ring->virt && addr % size) {

	if (ring->virt && lower_32_bits(addr) % size) {

		dma_free_coherent(dev, size, ring->virt, addr);

		dev_err(dev, "unable to alloc 0x%zx-aligned ring buffer\n",

		dev_err(dev, "unable to alloc 0x%x-aligned ring buffer\n",

			size);

		return -EINVAL;	/* Not a good error value, but distinct */

	} else if (!ring->virt) {

drivers/net/ipa/ipa_table.c

+6 −3
Original line number Diff line number Diff line
@@ -658,10 +658,13 @@ int ipa_table_init(struct ipa *ipa) 
		return -ENOMEM;



	/* We put the "zero rule" at the base of our table area.  The IPA

	 * hardware requires rules to be aligned on a 128-byte boundary.

	 * Make sure the allocation satisfies this constraint.

	 * hardware requires route and filter table rules to be aligned

	 * on a 128-byte boundary.  As long as the alignment constraint

	 * is a power of 2, we can check alignment using just the bottom

	 * 32 bits for a DMA address of any size.

	 */

	if (addr % IPA_TABLE_ALIGN) {

	BUILD_BUG_ON(!is_power_of_2(IPA_TABLE_ALIGN));

	if (lower_32_bits(addr) % IPA_TABLE_ALIGN) {

		dev_err(dev, "table address %pad not %u-byte aligned\n",

			&addr, IPA_TABLE_ALIGN);

		dma_free_coherent(dev, size, virt, addr);