[Piglit] [PATCH 13/14] dispatch: Use dlsym to lookup core symbols for EGL
Ilia Mirkin
imirkin at alum.mit.edu
Wed Apr 29 08:24:47 PDT 2015
FWIW I get the same problem... Something weird with glGetQueryObjectui64v?
On Wed, Apr 29, 2015 at 8:56 AM, Marek Olšák <maraeo at gmail.com> wrote:
> Correction: Only 2 pipeline statistics tests were broken, so all seems
> to be good (except those 2 tests).
>
> Marek
>
> On Tue, Apr 28, 2015 at 3:18 PM, Marek Olšák <maraeo at gmail.com> wrote:
>> Hi Chad,
>>
>> The patch breaks GetProcAddress for libGL, because libGL doesn't
>> export a lot of GL functions and glXGetProcAddress is the only way to
>> get them. Any idea for a fix?
>>
>> Marek
>>
>> On Fri, Apr 24, 2015 at 9:36 PM, Chad Versace <chad.versace at intel.com> wrote:
>>> On Mon 13 Apr 2015, Marek Olšák wrote:
>>>> From: Daniel Kurtz <djkurtz at chromium.org>
>>>>
>>>> eglGetProcAddress() only supports extension functions.
>>>> Therefore, we must use dlsym() directly on the GL client library to look
>>>> up core functions.
>>>>
>>>> The implementation here is a much simplified version of the one in
>>>> libepoxy. Most of the simplification is because piglit dispatch already
>>>> knows exactly for which GL API it is looking up a symbol.
>>>>
>>>> Signed-off-by: Daniel Kurtz <djkurtz at chromium.org>
>>>> ---
>>>> tests/util/piglit-dispatch-init.c | 57 +++++++++++++++++++++++++++++++++++++--
>>>> 1 file changed, 55 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/tests/util/piglit-dispatch-init.c b/tests/util/piglit-dispatch-init.c
>>>> index cc8b684..b0e1649 100644
>>>> --- a/tests/util/piglit-dispatch-init.c
>>>> +++ b/tests/util/piglit-dispatch-init.c
>>>> @@ -33,6 +33,8 @@
>>>>
>>>> #else /* Linux */
>>>>
>>>> +#include <dlfcn.h>
>>>> +
>>>> #if defined(PIGLIT_HAS_GLX)
>>>> # include "glxew.h"
>>>> #elif defined(PIGLIT_HAS_EGL)
>>>> @@ -154,6 +156,42 @@ get_core_proc_address(const char *function_name, int gl_10x_version)
>>>>
>>>> #else /* Linux */
>>>>
>>>> +#if defined(PIGLIT_HAS_EGL)
>>>> +#define GLX_LIB "libGL.so.1"
>>>> +#define GLES1_LIB "libGLESv1_CM.so.1"
>>>> +#define GLES2_LIB "libGLESv2.so.2"
>>>> +
>>>> +/** dlopen() return value for libGL.so.1 */
>>>> +static void *glx_handle;
>>>> +
>>>> +/** dlopen() return value for libGLESv1_CM.so.1 */
>>>> +static void *gles1_handle;
>>>> +
>>>> +/** dlopen() return value for libGLESv2.so.2 */
>>>> +static void *gles2_handle;
>>>> +
>>>> +static void *
>>>> +do_dlsym(void **handle, const char *lib_name, const char *function_name)
>>>> +{
>>>> + void *result;
>>>> +
>>>> + if (!*handle)
>>>> + *handle = dlopen(lib_name, RTLD_LAZY | RTLD_LOCAL);
>>>> +
>>>> + if (!*handle) {
>>>> + fprintf(stderr, "Could not open %s: %s\n", lib_name, dlerror());
>>>> + return NULL;
>>>> + }
>>>> +
>>>> + result = dlsym(*handle, function_name);
>>>> + if (!result)
>>>> + fprintf(stderr, "%s() not found in %s: %s\n", function_name, lib_name,
>>>> + dlerror());
>>>> +
>>>> + return result;
>>>> +}
>>>> +#endif
>>>> +
>>>> /**
>>>> * This function is used to retrieve the address of all GL functions
>>>> * on Linux.
>>>
>>> Everyting up to here looks good.
>>>
>>>> @@ -174,16 +212,31 @@ get_ext_proc_address(const char *function_name)
>>>> /**
>>>> * This function is used to retrieve the address of core GL functions
>>>> * on Linux.
>>>> + *
>>>> + * Since eglGetProcAddress() only supports extension functions, we must use
>>>> + * dlsym() directly on the GL client library to lookup core functions.
>>>
>>> This comment isn't true. Sometimes eglGetProcAddress does supports core
>>> functions. It should instead say:
>>>
>>> """
>>> eglGetProcAddress supports querying core functions only if EGL >= 1.5
>>> or if EGL_KHR_get_all_proc_addresses or
>>> EGL_KHR_client_get_all_proc_addresses is supported. Rather than worry
>>> about such details, when using EGL we consistently use dlsym() on the
>>> client library to lookup core functions.
>>> """
>>>
>>> This works for libGLESv1_CM.so and libGLESv2.so. But libGL.so wasn't designed
>>> with EGL in mind. The antiquated OpenGL ABI for Linux [1] states:
>>>
>>> 3.4. [The OpenGL library] must export all OpenGL 1.2, [...] GLX 1.3, and
>>> ARB_multitexture entry points statically. [...] Applications should not
>>> expect to link statically against any entry points not specified here.
>>>
>>> The specification of eglGetProcAddress and the official ABI specification for
>>> libGL are mutually incompatible. I think it's best to comply with
>>> eglGetProcAddress's restrictions rather than complying with a 15 year old
>>> standard that no one follows anymore. In other words, I think this patch takes
>>> the right approach.
>>>
>>>> */
>>>> static piglit_dispatch_function_ptr
>>>> get_core_proc_address(const char *function_name, int gl_10x_version)
>>>> {
>>>> - /* We don't need to worry about the GL version, since on Apple
>>>> +#if defined(PIGLIT_HAS_EGL)
>>>> + switch (gl_10x_version) {
>>>> + case 11:
>>>> + return do_dlsym(&gles1_handle, GLES1_LIB, function_name);
>>>> + case 20:
>>>> + return do_dlsym(&gles2_handle, GLES2_LIB, function_name);
>>>> + case 10:
>>>> + default:
>>>> + /* GL does not have its own library, so use GLX */
>>>> + return do_dlsym(&glx_handle, GLX_LIB, function_name);
>>>> + }
>>>> +#else
>>>> + /* We don't need to worry about the GL version, since when using GLX
>>>> * we retrieve all proc addresses in the same way.
>>>> */
>>>> (void) gl_10x_version;
>>>> -
>>>> return get_ext_proc_address(function_name);
>>>> +#endif
>>>> }
>>>
>>> I was initially certain this patch would break piglit-dispatch for certain core
>>> GL functions. But I was wrong. This patch's approach looks good to me. (Its
>>> correctness relies on piglit-dispatch's subtle interpretation of the
>>> gl_10x_version parameter, a subtlety that's easy to forget).
>>>
>>> The default case may cause problems on some GL implementations, because of the
>>> specification conflicts I explained above. According to Linux's official OpenGL
>>> ABI, one cannot dlsym(libGL.so.1) for core functions that appeared in GL
>>> versions after 1.2. But, I think the risk is minor. If we later discover that
>>> the default case does break piglit-dispatch on some GL implementation, then we
>>> can easily fix it by changing it to use get_ext_proc_address() instead of dlsym().
>>>
>>> Reviewed-by: Chad Versace <chad.versace at intel.com>
>>>
>>> Thanks for upstreaming all of Daniel's fixes.
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