[PATCH 1/2] drm: Implement vm_operations_struct.access

[Felix Kuehling <Felix.Kuehling-5C7GfCeVMHo@public.gmane.org>]

Allows gdb to access contents of user mode mapped BOs. VRAM access
requires the driver to implement a new callback in ttm_bo_driver.

Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
---
 drivers/gpu/drm/ttm/ttm_bo_vm.c | 66 ++++++++++++++++++++++++++++++++++++++++-
 include/drm/ttm/ttm_bo_driver.h | 12 ++++++++
 2 files changed, 77 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
index 9f53df9..0ef2eb9 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
@@ -294,10 +294,74 @@ static void ttm_bo_vm_close(struct vm_area_struct *vma)
 	vma->vm_private_data = NULL;
 }
 
+static int ttm_bo_vm_access_kmap(struct ttm_buffer_object *bo,
+				 unsigned long offset,
+				 void *buf, int len, int write)
+{
+	unsigned long first_page = offset >> PAGE_SHIFT;
+	unsigned long last_page = (offset + len - 1) >> PAGE_SHIFT;
+	unsigned long num_pages = last_page - first_page + 1;
+	struct ttm_bo_kmap_obj map;
+	void *ptr;
+	bool is_iomem;
+	int ret;
+
+	ret = ttm_bo_kmap(bo, first_page, num_pages, &map);
+	if (ret)
+		return ret;
+
+	offset -= first_page << PAGE_SHIFT;
+	ptr = (uint8_t *)ttm_kmap_obj_virtual(&map, &is_iomem) + offset;
+	WARN_ON(is_iomem);
+	if (write)
+		memcpy(ptr, buf, len);
+	else
+		memcpy(buf, ptr, len);
+	ttm_bo_kunmap(&map);
+
+	return len;
+}
+
+static int ttm_bo_vm_access(struct vm_area_struct *vma, unsigned long addr,
+			    void *buf, int len, int write)
+{
+	unsigned long offset = (addr) - vma->vm_start;
+	struct ttm_buffer_object *bo = vma->vm_private_data;
+	int ret;
+
+	if (len < 1 || (offset + len) >> PAGE_SHIFT > bo->num_pages)
+		return -EIO;
+
+	ret = ttm_bo_reserve(bo, true, false, NULL);
+	if (ret)
+		return ret;
+
+	switch(bo->mem.mem_type) {
+	case TTM_PL_SYSTEM:
+	case TTM_PL_TT:
+		ret = ttm_bo_vm_access_kmap(bo, offset, buf, len, write);
+		break;
+	case TTM_PL_VRAM:
+		if (bo->bdev->driver->access_vram)
+			ret = bo->bdev->driver->access_vram(
+				bo, offset, buf, len, write);
+		else
+			ret = -EIO;
+		break;
+	default:
+		ret = -EIO;
+	}
+
+	ttm_bo_unreserve(bo);
+
+	return ret;
+}
+
 static const struct vm_operations_struct ttm_bo_vm_ops = {
 	.fault = ttm_bo_vm_fault,
 	.open = ttm_bo_vm_open,
-	.close = ttm_bo_vm_close
+	.close = ttm_bo_vm_close,
+	.access = ttm_bo_vm_access
 };
 
 static struct ttm_buffer_object *ttm_bo_vm_lookup(struct ttm_bo_device *bdev,
diff --git a/include/drm/ttm/ttm_bo_driver.h b/include/drm/ttm/ttm_bo_driver.h
index 6bbd34d..6ce5094 100644
--- a/include/drm/ttm/ttm_bo_driver.h
+++ b/include/drm/ttm/ttm_bo_driver.h
@@ -471,6 +471,18 @@ struct ttm_bo_driver {
 	 */
 	unsigned long (*io_mem_pfn)(struct ttm_buffer_object *bo,
 				    unsigned long page_offset);
+
+	/**
+	 * Read/write VRAM buffers for ptrace access
+	 *
+	 * @bo: the BO to access
+	 * @offset: the offset from the start of the BO
+	 * @buf: pointer to source/destination buffer
+	 * @len: number of bytes to copy
+	 * @write: whether to read (0) from or write (non-0) to BO
+	 */
+	int (*access_vram)(struct ttm_buffer_object *bo, unsigned long offset,
+			   void *buf, int len, int write);
 };
 
 /**
-- 
1.9.1

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