[PATCH v4 2/7] dma-buf: heaps: Initialize a restricted heap

[Yong Wu]

Initialize a restricted heap. Currently just add a null heap, Prepare for
the later patches.

Signed-off-by: Yong Wu <yong.wu@xxxxxxxxxxxx>
---
 drivers/dma-buf/heaps/Kconfig           |  9 ++++
 drivers/dma-buf/heaps/Makefile          |  3 +-
 drivers/dma-buf/heaps/restricted_heap.c | 67 +++++++++++++++++++++++++
 drivers/dma-buf/heaps/restricted_heap.h | 22 ++++++++
 4 files changed, 100 insertions(+), 1 deletion(-)
 create mode 100644 drivers/dma-buf/heaps/restricted_heap.c
 create mode 100644 drivers/dma-buf/heaps/restricted_heap.h

diff --git a/drivers/dma-buf/heaps/Kconfig b/drivers/dma-buf/heaps/Kconfig
index a5eef06c4226..e54506f480ea 100644
--- a/drivers/dma-buf/heaps/Kconfig
+++ b/drivers/dma-buf/heaps/Kconfig
@@ -12,3 +12,12 @@ config DMABUF_HEAPS_CMA
 	  Choose this option to enable dma-buf CMA heap. This heap is backed
 	  by the Contiguous Memory Allocator (CMA). If your system has these
 	  regions, you should say Y here.
+
+config DMABUF_HEAPS_RESTRICTED
+	bool "DMA-BUF Restricted Heap"
+	depends on DMABUF_HEAPS
+	help
+	  Choose this option to enable dma-buf restricted heap. The purpose of this
+	  heap is to manage buffers that are inaccessible to the kernel and user space.
+	  There may be several ways to restrict it, for example it may be encrypted or
+	  protected by a TEE or hypervisor. If in doubt, say N.
diff --git a/drivers/dma-buf/heaps/Makefile b/drivers/dma-buf/heaps/Makefile
index 974467791032..a2437c1817e2 100644
--- a/drivers/dma-buf/heaps/Makefile
+++ b/drivers/dma-buf/heaps/Makefile
@@ -1,3 +1,4 @@
 # SPDX-License-Identifier: GPL-2.0
-obj-$(CONFIG_DMABUF_HEAPS_SYSTEM)	+= system_heap.o
 obj-$(CONFIG_DMABUF_HEAPS_CMA)		+= cma_heap.o
+obj-$(CONFIG_DMABUF_HEAPS_RESTRICTED)	+= restricted_heap.o
+obj-$(CONFIG_DMABUF_HEAPS_SYSTEM)	+= system_heap.o
diff --git a/drivers/dma-buf/heaps/restricted_heap.c b/drivers/dma-buf/heaps/restricted_heap.c
new file mode 100644
index 000000000000..fd7c82abd42e
--- /dev/null
+++ b/drivers/dma-buf/heaps/restricted_heap.c
@@ -0,0 +1,67 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * DMABUF restricted heap exporter
+ *
+ * Copyright (C) 2024 MediaTek Inc.
+ */
+
+#include <linux/dma-buf.h>
+#include <linux/dma-heap.h>
+#include <linux/err.h>
+#include <linux/slab.h>
+
+#include "restricted_heap.h"
+
+static struct dma_buf *
+restricted_heap_allocate(struct dma_heap *heap, unsigned long size,
+			 unsigned long fd_flags, unsigned long heap_flags)
+{
+	struct restricted_buffer *restricted_buf;
+	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
+	struct dma_buf *dmabuf;
+	int ret;
+
+	restricted_buf = kzalloc(sizeof(*restricted_buf), GFP_KERNEL);
+	if (!restricted_buf)
+		return ERR_PTR(-ENOMEM);
+
+	restricted_buf->size = ALIGN(size, PAGE_SIZE);
+	restricted_buf->heap = heap;
+
+	exp_info.exp_name = dma_heap_get_name(heap);
+	exp_info.size = restricted_buf->size;
+	exp_info.flags = fd_flags;
+	exp_info.priv = restricted_buf;
+
+	dmabuf = dma_buf_export(&exp_info);
+	if (IS_ERR(dmabuf)) {
+		ret = PTR_ERR(dmabuf);
+		goto err_free_buf;
+	}
+
+	return dmabuf;
+
+err_free_buf:
+	kfree(restricted_buf);
+	return ERR_PTR(ret);
+}
+
+static const struct dma_heap_ops restricted_heap_ops = {
+	.allocate = restricted_heap_allocate,
+};
+
+int restricted_heap_add(struct restricted_heap *rstrd_heap)
+{
+	struct dma_heap_export_info exp_info;
+	struct dma_heap *heap;
+
+	exp_info.name = rstrd_heap->name;
+	exp_info.ops = &restricted_heap_ops;
+	exp_info.priv = (void *)rstrd_heap;
+
+	heap = dma_heap_add(&exp_info);
+	if (IS_ERR(heap))
+		return PTR_ERR(heap);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(restricted_heap_add);
diff --git a/drivers/dma-buf/heaps/restricted_heap.h b/drivers/dma-buf/heaps/restricted_heap.h
new file mode 100644
index 000000000000..443028f6ba3b
--- /dev/null
+++ b/drivers/dma-buf/heaps/restricted_heap.h
@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Restricted heap Header.
+ *
+ * Copyright (C) 2024 MediaTek, Inc.
+ */
+
+#ifndef _DMABUF_RESTRICTED_HEAP_H_
+#define _DMABUF_RESTRICTED_HEAP_H_
+
+struct restricted_buffer {
+	struct dma_heap		*heap;
+	size_t			size;
+};
+
+struct restricted_heap {
+	const char		*name;
+};
+
+int restricted_heap_add(struct restricted_heap *rstrd_heap);
+
+#endif
-- 
2.25.1