[PATCH 2/4] dma-mapping: Add bounced DMA pool

[Claire Chang]

Add the initialization function to create bounce buffer pools from
matching reserved-memory nodes in the device tree.

The bounce buffer pools provide a basic level of protection against
the DMA overwriting buffer contents at unexpected times. However, to
protect against general data leakage and system memory corruption, the
system needs to provide a way to restrict the DMA to a predefined memory
region.

Signed-off-by: Claire Chang <tientzu@xxxxxxxxxxxx>
---
 kernel/dma/bounced.c | 89 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 89 insertions(+)

diff --git a/kernel/dma/bounced.c b/kernel/dma/bounced.c
index fcaabb5eccf2..0bfd6cf90aee 100644
--- a/kernel/dma/bounced.c
+++ b/kernel/dma/bounced.c
@@ -12,6 +12,9 @@
 #include <linux/dma-noncoherent.h>
 #include <linux/io.h>
 #include <linux/genalloc.h>
+#include <linux/of.h>
+#include <linux/of_fdt.h>
+#include <linux/of_reserved_mem.h>
 #include <linux/slab.h>
 
 struct dma_bounced_mem {
@@ -213,3 +216,89 @@ const struct dma_map_ops dma_bounced_ops = {
 	.max_mapping_size	= dma_bounced_max_mapping_size,
 	.get_merge_boundary	= NULL,
 };
+
+static int dma_bounced_device_init(struct reserved_mem *rmem,
+				   struct device *dev)
+{
+	struct dma_bounced_mem *mem;
+	int ret;
+
+	mem = kzalloc(sizeof(*mem), GFP_KERNEL);
+	if (!mem)
+		return -ENOMEM;
+
+	mem->virt_base =
+		devm_memremap(dev, rmem->base, rmem->size, MEMREMAP_WB);
+	if (!mem->virt_base) {
+		ret = -EINVAL;
+		goto error;
+	}
+
+	mem->size = rmem->size;
+	mem->device_base = phys_to_dma(dev, rmem->base);
+	mem->device_end = mem->device_base + rmem->size;
+
+	mem->orig_addr = kcalloc(mem->size >> PAGE_SHIFT,
+				 sizeof(*mem->orig_addr), GFP_KERNEL);
+	if (!mem->orig_addr) {
+		ret = -ENOMEM;
+		goto error;
+	}
+
+	mem->pool = devm_gen_pool_create(dev, PAGE_SHIFT, NUMA_NO_NODE,
+					 "bounced DMA");
+	if (!mem->pool) {
+		ret = -ENOMEM;
+		goto error;
+	}
+
+	ret = gen_pool_add_virt(mem->pool, (unsigned long)mem->virt_base,
+				rmem->base, rmem->size, NUMA_NO_NODE);
+	if (ret)
+		goto error;
+
+	dev->dma_bounced_mem = mem;
+	set_dma_ops(dev, &dma_bounced_ops);
+
+	return 0;
+
+error:
+	kfree(mem);
+
+	return ret;
+}
+
+static void dma_bounced_device_release(struct reserved_mem *rmem,
+				       struct device *dev)
+{
+	struct dma_bounced_mem *mem = dev->dma_bounced_mem;
+
+	set_dma_ops(dev, NULL);
+	dev->dma_bounced_mem = NULL;
+
+	kfree(mem->orig_addr);
+	kfree(mem);
+}
+
+static const struct reserved_mem_ops rmem_dma_bounced_ops = {
+	.device_init	= dma_bounced_device_init,
+	.device_release	= dma_bounced_device_release,
+};
+
+static int __init dma_bounced_setup(struct reserved_mem *rmem)
+{
+	unsigned long node = rmem->fdt_node;
+
+	if (of_get_flat_dt_prop(node, "reusable", NULL) ||
+	    of_get_flat_dt_prop(node, "linux,cma-default", NULL) ||
+	    of_get_flat_dt_prop(node, "linux,dma-default", NULL) ||
+	    of_get_flat_dt_prop(node, "no-map", NULL))
+		return -EINVAL;
+
+	rmem->ops = &rmem_dma_bounced_ops;
+	pr_info("Reserved memory: created DMA bounced memory pool at %pa, size %ld MiB\n",
+		&rmem->base, (unsigned long)rmem->size / SZ_1M);
+	return 0;
+}
+
+RESERVEDMEM_OF_DECLARE(dma, "bounced-dma-pool", dma_bounced_setup);
-- 
2.27.0.383.g050319c2ae-goog