Re: [Mesa-dev] [Mesa-stable] [PATCH] radv: Use build ID if available for cache UUID.

[Emil Velikov]

On 16 September 2018 at 01:58, Bas Nieuwenhuizen
<b...@basnieuwenhuizen.nl> wrote:
> To get an useful UUID for systems that have a non-useful mtime
> for the binaries.
>
> I started using using SHA1 to ensure we get reasonable mixing
> in the various possibilities and the various build id lengths.
>
> CC: <mesa-sta...@lists.freedesktop.org>
> ---
>  src/amd/vulkan/radv_device.c | 43 +++++++++++++++++++++++++++++-------
>  1 file changed, 35 insertions(+), 8 deletions(-)
>
> diff --git a/src/amd/vulkan/radv_device.c b/src/amd/vulkan/radv_device.c
> index 8989ec3553f..a2a73089f27 100644
> --- a/src/amd/vulkan/radv_device.c
> +++ b/src/amd/vulkan/radv_device.c
> @@ -45,22 +45,49 @@
>  #include "sid.h"
>  #include "gfx9d.h"
>  #include "addrlib/gfx9/chip/gfx9_enum.h"
> +#include "util/build_id.h"
>  #include "util/debug.h"
> +#include "util/mesa-sha1.h"
> +
> +static bool
> +radv_get_build_id(void *ptr, struct mesa_sha1 *ctx)
> +{
> +       uint32_t timestamp;
> +
> +#ifdef HAVE_DL_ITERATE_PHDR
> +       const struct build_id_note *note = NULL;
> +       if ((note = build_id_find_nhdr_for_addr(ptr))) {
> +               _mesa_sha1_update(ctx, build_id_data(note), 
> build_id_length(note));
> +       } else
> +#endif
> +       if (disk_cache_get_function_timestamp(ptr, &timestamp)) {
> +               if (!timestamp) {
> +                       fprintf(stderr, "radv: The provided filesystem 
> timestamp for the cache is bogus!\n");
> +               }
> +
> +               _mesa_sha1_update(ctx, &timestamp, sizeof(timestamp));
> +       } else
> +               return false;
> +       return true;
> +}
>
>  static int
>  radv_device_get_cache_uuid(enum radeon_family family, void *uuid)
>  {
> -       uint32_t mesa_timestamp, llvm_timestamp;
> -       uint16_t f = family;
> +       struct mesa_sha1 ctx;
> +       unsigned char sha1[20];
> +       unsigned ptr_size = sizeof(void*);
>         memset(uuid, 0, VK_UUID_SIZE);
> -       if (!disk_cache_get_function_timestamp(radv_device_get_cache_uuid, 
> &mesa_timestamp) ||
> -           
> !disk_cache_get_function_timestamp(LLVMInitializeAMDGPUTargetInfo, 
> &llvm_timestamp))
> +
> +       if (!radv_get_build_id(radv_device_get_cache_uuid, &ctx) ||
> +           !radv_get_build_id(LLVMInitializeAMDGPUTargetInfo, &ctx))
>                 return -1;
>
> -       memcpy(uuid, &mesa_timestamp, 4);
> -       memcpy((char*)uuid + 4, &llvm_timestamp, 4);
> -       memcpy((char*)uuid + 8, &f, 2);
> -       snprintf((char*)uuid + 10, VK_UUID_SIZE - 10, "radv%zd", sizeof(void 
> *));
> +       _mesa_sha1_update(&ctx, &family, sizeof(family));
> +       _mesa_sha1_update(&ctx, &ptr_size, sizeof(ptr_size));
> +       _mesa_sha1_final(&ctx, sha1);
> +
A slightly more important thing I did not notice:
The _mesa_sha1_init() call is missing, so we're working on an
uninitialized stack variable.

Even then, skimming at radv wrt anv:
- driver_uuid is never set, rather fortunately since
ac_compute_driver_uuid() returns a fixed "AMD-MESA-DRV"
ANV does sha1_update(build_id) + sha1_update(chipset_id)

- device_uuid produces a "unique ID" of the bus location, not the device
Ideally you'd want bus location + chipset_id + driver specific options.
ANV only lacks the bus location, since the device is fixed ;-)

Aside: disk_cache_format_hex_id is a copy of _mesa_sha1_format()

HTH
Emil
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