fdo-mirrors/mesa
1
0
Fork 0
mirror of https://gitlab.freedesktop.org/mesa/mesa.git synced 2025-12-25 08:40:11 +01:00
Code Issues Projects Releases Packages Wiki Activity Actions 1

v3dv: fix misalignment in descriptor layout structure

Browse source 
Current memory layout for v3dv_descriptior_set_layout structure is the
following:

```
                                                                  /* offset           size */
type = struct v3dv_descriptor_set_layout {
    struct vk_object_base base;                                   /*   0                64 */
    VkDescriptorSetLayoutCreateFlags flags;                       /*  64                 4 */
    uint32_t binding_count;                                       /*  68                 4 */
    uint32_t bo_size;                                             /*  72                 4 */
    uint16_t shader_stages;                                       /*  76                 2 */
                                                                  /*         PAD 2         */
    uint32_t descriptor_count;                                    /*  80                 4 */
    uint16_t dynamic_offset_count;                                /*  84                 2 */
                                                                  /*         PAD 2         */
    uint32_t ref_cnt;                                             /*  88                 4 */
    struct v3dv_descriptor_set_binding_layout binding[0];         /*  92                32 */
}                               [...]         binding[1];         /* 124                32 */
```

Besides wasting 4 bytes in padding, the main problem is that `binding`
fields are not aligned to 8 bytes (64-bits), which is undefined behaviour
in C.

Just moving `descriptor_count` field below we get the new layout:

```
                                                                  /* offset           size */
type = struct v3dv_descriptor_set_layout {
    struct vk_object_base base;                                   /*   0                64 */
    VkDescriptorSetLayoutCreateFlags flags;                       /*  64                 4 */
    uint32_t binding_count;                                       /*  68                 4 */
    uint32_t bo_size;                                             /*  72                 4 */
    uint16_t shader_stages;                                       /*  76                 2 */
    uint16_t dynamic_offset_count;                                /*  78                 2 */
    uint32_t descriptor_count;                                    /*  80                 4 */
    uint32_t ref_cnt;                                             /*  84                 4 */
    struct v3dv_descriptor_set_binding_layout binding[0];         /*  88                32 */
}                               [...]         binding[1];         /* 120                32 */
```

Which removes the padding requirement, and more important, make the
`binding` pointers to be correctly aligned.

This has been detected by the Undefined Behaviour Sanitizer (UBSan).

Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Signed-off-by: Juan A. Suarez Romero <jasuarez@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/29911>
This commit is contained in:
Juan A. Suarez Romero 2024-06-26 10:23:03 +02:00 • committed by Marge Bot
parent 9696fd378a
commit fc286867fb
1 changed files with 3 additions and 3 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

6
src/broadcom/vulkan/v3dv_private.h
View file

@ -2063,12 +2063,12 @@ struct v3dv_descriptor_set_layout {
/* Shader stages affected by this descriptor set */
uint16_t shader_stages;
/* Number of descriptors in this descriptor set */
uint32_t descriptor_count;
/* Number of dynamic offsets used by this descriptor set */
uint16_t dynamic_offset_count;
/* Number of descriptors in this descriptor set */
uint32_t descriptor_count;
/* Descriptor set layouts can be destroyed even if they are still being
* used.
*/