add new system file

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2024-02-20 102a0743326a03cd1a1202ceda21e175b7d3575c

 kernel/drivers/dma-buf/dma-heap.c
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@@ -11,6 +11,7 @@
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 #include <linux/device.h>
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 #include <linux/dma-buf.h>
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 #include <linux/err.h>
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+#include <linux/xarray.h>
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 #include <linux/list.h>
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 #include <linux/slab.h>
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 #include <linux/nospec.h>
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@@ -49,9 +50,7 @@
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 static DEFINE_MUTEX(heap_list_lock);
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 static dev_t dma_heap_devt;
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 static struct class *dma_heap_class;
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-
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-static DEFINE_MUTEX(heap_devnode_lock);
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-static DECLARE_BITMAP(heap_devnode_nums, NUM_HEAP_MINORS);
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+static DEFINE_XARRAY_ALLOC(dma_heap_minors);
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 struct dma_heap *dma_heap_find(const char *name)
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 {
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@@ -124,14 +123,11 @@
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 {
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 	struct dma_heap *heap;
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-	mutex_lock(&heap_devnode_lock);
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-	heap = container_of(inode->i_cdev, struct dma_heap, heap_cdev);
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+	heap = xa_load(&dma_heap_minors, iminor(inode));
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 	if (!heap) {
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 		pr_err("dma_heap: minor %d unknown.\n", iminor(inode));
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-		mutex_unlock(&heap_devnode_lock);
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 		return -ENODEV;
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 	}
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-	mutex_unlock(&heap_devnode_lock);
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 	/* instance data as context */
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 	file->private_data = heap;
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@@ -273,9 +269,7 @@
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 	device_destroy(dma_heap_class, heap->heap_devt);
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 	cdev_del(&heap->heap_cdev);
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-	mutex_lock(&heap_devnode_lock);
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-	clear_bit(minor, heap_devnode_nums);
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-	mutex_unlock(&heap_devnode_lock);
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+	xa_erase(&dma_heap_minors, minor);
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 	kfree(heap);
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 }
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@@ -320,7 +314,7 @@
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 struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
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 {
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-	struct dma_heap *heap, *err_ret;
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+	struct dma_heap *heap, *h, *err_ret;
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 	unsigned int minor;
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 	int ret;
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@@ -334,15 +328,6 @@
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 		return ERR_PTR(-EINVAL);
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 	}
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-	/* check the name is unique */
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-	heap = dma_heap_find(exp_info->name);
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-	if (heap) {
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-		pr_err("dma_heap: Already registered heap named %s\n",
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-		       exp_info->name);
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-		dma_heap_put(heap);
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-		return ERR_PTR(-EINVAL);
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-	}
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-
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 	heap = kzalloc(sizeof(*heap), GFP_KERNEL);
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 	if (!heap)
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 		return ERR_PTR(-ENOMEM);
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@@ -352,18 +337,14 @@
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 	heap->ops = exp_info->ops;
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 	heap->priv = exp_info->priv;
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-	/* Part 1: Find a free minor number */
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-
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-	mutex_lock(&heap_devnode_lock);
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-	minor = find_next_zero_bit(heap_devnode_nums, NUM_HEAP_MINORS, 0);
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-	if (minor == NUM_HEAP_MINORS) {
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-		mutex_unlock(&heap_devnode_lock);
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+	/* Find unused minor number */
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+	ret = xa_alloc(&dma_heap_minors, &minor, heap,
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+		       XA_LIMIT(0, NUM_HEAP_MINORS - 1), GFP_KERNEL);
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+	if (ret < 0) {
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 		pr_err("dma_heap: Unable to get minor number for heap\n");
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-		err_ret = ERR_PTR(-ENFILE);
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+		err_ret = ERR_PTR(ret);
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 		goto err0;
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 	}
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-	set_bit(minor, heap_devnode_nums);
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-	mutex_unlock(&heap_devnode_lock);
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 	/* Create device */
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 	heap->heap_devt = MKDEV(MAJOR(dma_heap_devt), minor);
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@@ -390,19 +371,31 @@
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 	/* Make sure it doesn't disappear on us */
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 	heap->heap_dev = get_device(heap->heap_dev);
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-	/* Add heap to the list */
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 	mutex_lock(&heap_list_lock);
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+	/* check the name is unique */
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+	list_for_each_entry(h, &heap_list, list) {
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+		if (!strcmp(h->name, exp_info->name)) {
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+			mutex_unlock(&heap_list_lock);
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+			pr_err("dma_heap: Already registered heap named %s\n",
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+			       exp_info->name);
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+			err_ret = ERR_PTR(-EINVAL);
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+			put_device(heap->heap_dev);
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+			goto err3;
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+		}
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+	}
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+
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+	/* Add heap to the list */
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 	list_add(&heap->list, &heap_list);
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 	mutex_unlock(&heap_list_lock);
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 	return heap;
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+err3:
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+	device_destroy(dma_heap_class, heap->heap_devt);
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 err2:
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 	cdev_del(&heap->heap_cdev);
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 err1:
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-	mutex_lock(&heap_devnode_lock);
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-	clear_bit(minor, heap_devnode_nums);
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-	mutex_unlock(&heap_devnode_lock);
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+	xa_erase(&dma_heap_minors, minor);
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 err0:
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 	kfree(heap);
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 	return err_ret;