[Mesa-stable] [PATCH] st/dri: implement the __DRI_DRIVER_VTABLE extension

[Eric Anholt]

Emil Velikov <emil.l.velikov at gmail.com> writes:

> Hi Eric,
>
> On 24 August 2018 at 14:11, Emil Velikov <emil.l.velikov at gmail.com> wrote:
>> From: Emil Velikov <emil.velikov at collabora.com>
>>
>> As the comment above globalDriverAPI (in dri_util.c) says, if the loader
>> is unaware of createNewScreen2 there is a race condition.
>>
>> In which globalDriverAPI, will be set in the driver driDriverGetExtensions*
>> function and used in createNewScreen(). If we call another drivers'
>> driDriverGetExtensions, the createNewScreen will use the latter's API
>> instead of the former.
>>
>> To make it more convoluting, the driver _must_ also expose
>> __DRI_DRIVER_VTABLE, as that one exposes the correct API.
>>
>> The race also occurs, for loaders which use the pre megadrivers
>> driDriverGetExtensions entrypoint.
>>
>> Cc: mesa-stable at lists.freedesktop.org
>> Signed-off-by: Emil Velikov <emil.velikov at collabora.com>
>> ---
>>  src/gallium/state_trackers/dri/dri2.c       | 21 +++++++++++++++++++++
>>  src/gallium/state_trackers/dri/dri_screen.h |  1 +
>>  src/gallium/state_trackers/dri/drisw.c      |  6 ++++++
>>  src/gallium/targets/dri/target.c            |  2 +-
>>  4 files changed, 29 insertions(+), 1 deletion(-)
>>
>> diff --git a/src/gallium/state_trackers/dri/dri2.c b/src/gallium/state_trackers/dri/dri2.c
>> index 3cbca4e5dc3..b21e6815796 100644
>> --- a/src/gallium/state_trackers/dri/dri2.c
>> +++ b/src/gallium/state_trackers/dri/dri2.c
>> @@ -2318,11 +2318,32 @@ const struct __DriverAPIRec dri_kms_driver_api = {
>>     .ReleaseBuffer  = dri2_release_buffer,
>>  };
>>
>> +static const struct __DRIDriverVtableExtensionRec gallium_drm_vtable = {
>> +   .base = { __DRI_DRIVER_VTABLE, 1 },
>> +   .vtable = &galliumdrm_driver_api,
>> +};
>> +
>> +static const struct __DRIDriverVtableExtensionRec dri_kms_vtable = {
>> +   .base = { __DRI_DRIVER_VTABLE, 1 },
>> +   .vtable = &dri_kms_driver_api,
>> +};
>> +
>>  /* This is the table of extensions that the loader will dlsym() for. */
>>  const __DRIextension *galliumdrm_driver_extensions[] = {
>>      &driCoreExtension.base,
>>      &driImageDriverExtension.base,
>>      &driDRI2Extension.base,
>> +    &gallium_drm_vtable.base,
>> +    &gallium_config_options.base,
>> +    NULL
>> +};
>> +
>> +/* This is the table of extensions that the loader will dlsym() for. */
>> +const __DRIextension *dri_kms_driver_extensions[] = {
>> +    &driCoreExtension.base,
>> +    &driImageDriverExtension.base,
>> +    &driDRI2Extension.base,
>> +    &dri_kms_vtable.base,
>>      &gallium_config_options.base,
>>      NULL
>>  };
>> diff --git a/src/gallium/state_trackers/dri/dri_screen.h b/src/gallium/state_trackers/dri/dri_screen.h
>> index 8d2d9c02892..fde3b4088a7 100644
>> --- a/src/gallium/state_trackers/dri/dri_screen.h
>> +++ b/src/gallium/state_trackers/dri/dri_screen.h
>> @@ -147,6 +147,7 @@ void
>>  dri_destroy_screen(__DRIscreen * sPriv);
>>
>>  extern const struct __DriverAPIRec dri_kms_driver_api;
>> +extern const __DRIextension *dri_kms_driver_extensions[];
>>
>>  extern const struct __DriverAPIRec galliumdrm_driver_api;
>>  extern const __DRIextension *galliumdrm_driver_extensions[];
>> diff --git a/src/gallium/state_trackers/dri/drisw.c b/src/gallium/state_trackers/dri/drisw.c
>> index 1fba71bdd97..76a06b36664 100644
>> --- a/src/gallium/state_trackers/dri/drisw.c
>> +++ b/src/gallium/state_trackers/dri/drisw.c
>> @@ -513,11 +513,17 @@ const struct __DriverAPIRec galliumsw_driver_api = {
>>     .CopySubBuffer = drisw_copy_sub_buffer,
>>  };
>>
>> +static const struct __DRIDriverVtableExtensionRec galliumsw_vtable = {
>> +   .base = { __DRI_DRIVER_VTABLE, 1 },
>> +   .vtable = &galliumsw_driver_api,
>> +};
>> +
>>  /* This is the table of extensions that the loader will dlsym() for. */
>>  const __DRIextension *galliumsw_driver_extensions[] = {
>>      &driCoreExtension.base,
>>      &driSWRastExtension.base,
>>      &driCopySubBufferExtension.base,
>> +    &galliumsw_vtable.base,
>>      &gallium_config_options.base,
>>      NULL
>>  };
>> diff --git a/src/gallium/targets/dri/target.c b/src/gallium/targets/dri/target.c
>> index 835d125f21e..e943cae6a16 100644
>> --- a/src/gallium/targets/dri/target.c
>> +++ b/src/gallium/targets/dri/target.c
>> @@ -28,7 +28,7 @@ const __DRIextension **__driDriverGetExtensions_kms_swrast(void);
>>  PUBLIC const __DRIextension **__driDriverGetExtensions_kms_swrast(void)
>>  {
>>     globalDriverAPI = &dri_kms_driver_api;
>> -   return galliumdrm_driver_extensions;
>> +   return dri_kms_driver_extensions;
>>  }
>>
> Can you please skim through the above?
>
> Seems like I forgot to implement this while making the gallium mega-drivers.
> I did not notice any issues in practise, but with EGLDevice this will
> become more likely to hit.

With having a new baby, I'm getting maybe an hour a day for software
stuff.  I won't have time to review this.
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