Mesa hooking

test.c

/*
  
  MESA=<path to git clone of git://anongit.freedesktop.org/mesa/mesa>
	gcc
	-I$MESA/include/
	-I$MESA/src/
	-I$MESA/src/mesa
	-I$MESA/src/mapi
	-I$MESA/src/gallium/include
	-lglapi
	-lOSMesa
	-g -o test test.c

*/

#include <stdio.h>

#include "GL/gl.h"
#include "GL/osmesa.h"

#define HAVE_PTHREAD
#define HAVE_TIMESPEC_GET
#define GLX_USE_TLS
#include "mesa/main/mtypes.h"
#include "mapi/glapi/glapi.h"
#include "gallium/include/state_tracker/st_api.h"
#include "gallium/include/pipe/p_context.h"
#include "gallium/include/pipe/p_state.h"

static void (*original_draw_vbo)(struct pipe_context *pipe, const struct pipe_draw_info *info);

void override_draw_vbo(struct pipe_context *pipe, const struct pipe_draw_info *info) {

	printf("struct pipe_draw_info *info = {\n");
	printf("  ...\n");
	printf("  .has_user_indices = %d,\n", info->has_user_indices);
	printf("  ...\n");
	printf("  .start = %d,\n", info->start);
	printf("  .count = %d,\n", info->count);
	printf("  ...\n");
	printf("};\n");
	printf("\n");

	original_draw_vbo(pipe, info);
}


int main(int argc, char const *argv[]) {

	void *buffer = malloc(64*64*4);
	OSMesaContext osmesa_context = OSMesaCreateContext(OSMESA_RGBA, 0);
	OSMesaMakeCurrent(osmesa_context, buffer, 0x1401 /*GL_UNSIGNED_BYTE*/, 64, 64);

	char const *renderer;
	struct gl_context *glapi_context = _glapi_get_context();

	// glGetString loaded through libGL will return NULL regardless
	// renderer = glGetString(0x1F01); // GL_RENDERER
	// printf("glGetString(GL_RENDERER) = %s\n", renderer);

#define GL(X) ((typeof(&gl##X))OSMesaGetProcAddress("gl" #X))

	renderer = GL(GetString)(0x1F01);
	printf("OSMesaGetProcAddress(\"glGetString\")(GL_RENDERER) = %s\n", renderer);

	// renderer = glapi_context->Driver.GetString(glapi_context, 0x1F01);
	// printf("ctx->Driver->GetString(drv, GL_RENDERER) = %s\n", renderer);

	// you can't get the st through glapi_context->st sadly, but there's another way

	struct st_context_iface *st = (struct st_context_iface *)*(void**)osmesa_context;
	struct pipe_context *pipe = st->pipe;

	original_draw_vbo = pipe->draw_vbo;
	pipe->draw_vbo = &override_draw_vbo;


	GL(Begin)(GL_TRIANGLES);
	GL(Vertex3f)(0.0f, 0.0f, 0.0f);
	GL(Vertex3f)(0.0f, 1.0f, 0.0f);
	GL(Vertex3f)(1.0f, 0.0f, 0.0f);
	GL(End)();
	GL(Finish)();

	return 0;
}