panfrost: Remove vertex buffer offset from its size

The offset is added to the base address, so we need to subtract it from
the size to maintain the same end address and thus prevent a buffer
overflow:

   end_address = start_address + size

   start_address' = start_address + offset
   size' = size - offset

   end_address' = start_address' + size'
                = (start_address + offset) + (size - offset)
                = (start_address + size) + (offset - offset)
                = start_address + size
                = end_address

   QED.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>

1 files changed, 5 insertions, 2 deletions

diff --git a/src/gallium/drivers/panfrost/pan_instancing.c b/src/gallium/drivers/panfrost/pan_instancing.c
index 30023725b2e2..e5a1e7cfae30 100644
--- a/src/gallium/drivers/panfrost/pan_instancing.c
+++ b/src/gallium/drivers/panfrost/pan_instancing.c
@@ -292,7 +292,7 @@ panfrost_emit_vertex_data(struct panfrost_job *batch)
                  * will be adjusted back when we fixup the src_offset in
                  * mali_attr_meta */
 
-                mali_ptr raw_addr = panfrost_vertex_buffer_address(ctx, vbi);
+                mali_ptr raw_addr = rsrc->bo->gpu + buf->buffer_offset;
                 mali_ptr addr = raw_addr & ~63;
                 unsigned chopped_addr = raw_addr - addr;
 
@@ -302,7 +302,10 @@ panfrost_emit_vertex_data(struct panfrost_job *batch)
                 /* Set common fields */
                 attrs[k].elements = addr;
                 attrs[k].stride = buf->stride;
-                attrs[k].size = rsrc->base.width0;
+
+                /* Since we advanced the base pointer, we shrink the buffer
+                 * size */
+                attrs[k].size = rsrc->base.width0 - buf->buffer_offset;
 
                 /* We need to add the extra size we masked off (for
                  * correctness) so the data doesn't get clamped away */