From 437c78f976f5b39fc4b2a1c65903a229f55912dd Mon Sep 17 00:00:00 2001 From: Alex Elder Date: Mon, 22 Mar 2021 20:05:05 -0500 Subject: [PATCH] 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: Randy Dunlap Signed-off-by: Alex Elder Acked-by: Randy Dunlap # build-tested Signed-off-by: David S. Miller --- drivers/net/ipa/gsi.c | 11 +++++++---- drivers/net/ipa/ipa_table.c | 9 ++++++--- 2 files changed, 13 insertions(+), 7 deletions(-) diff --git a/drivers/net/ipa/gsi.c b/drivers/net/ipa/gsi.c index 7f3e338..b635582 100644 --- a/drivers/net/ipa/gsi.c +++ b/drivers/net/ipa/gsi.c @@ -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) { diff --git a/drivers/net/ipa/ipa_table.c b/drivers/net/ipa/ipa_table.c index 988f2c2..4236a50 100644 --- a/drivers/net/ipa/ipa_table.c +++ b/drivers/net/ipa/ipa_table.c @@ -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); -- 2.7.4