OpenGL Inject

This project demonstrates how to inject OpenGL rendering into existing applications using LD_PRELOAD. It allows you to modify the rendering pipeline of OpenGL applications without changing their source code.

You can modify the fragment shader by editing the fragment.shader file.

Build and run

To compile and run the project, use the provided script:

$ cd OpenGL_inject
$ ./compile_and_run.sh

Required tools/libraries/packages:

• g++
• x11 development libraries
• OpenGL development libraries
• Xrandr development libraries
• Xi development libraries
• ld (linker)
• mesa utils / glxgears

The list might be incomplete.

For now glxgears is the only tested application.

Benchmarks

Without LD_PRELOAD

__GL_SYNC_TO_VBLANK=0 vblank_mode=0 glxgears
158580 frames in 5.0 seconds = 31715.842 FPS
159663 frames in 5.0 seconds = 31932.600 FPS
159910 frames in 5.0 seconds = 31981.918 FPS
154489 frames in 5.0 seconds = 30897.789 FPS

With LD_PRELOAD

First version (no shader)

./compile_and_run.sh  # with gcc -fPIC -lglfw -lGL -lX11 -lpthread -lXrandr -lXi -ldl --shared -o ogl_inject.so lib.c
Try to load glAttachShader...
"glAttachShader" loaded: 0x7fd45a8f83c0
Try to load glCreateProgram...
"glCreateProgram" loaded: 0x7fd45a8fb580
Try to load glCompileShader...
"glCompileShader" loaded: 0x7fd45a8fa840
Try to load glCreateShader...
"glCreateShader" loaded: 0x7fd45a8fb660
Try to load glGetProgramiv...
"glGetProgramiv" loaded: 0x7fd45a901040
Try to load glGetProgramInfoLog...
"glGetProgramInfoLog" loaded: 0x7fd45a900d20
Try to load glGetShaderiv...
"glGetShaderiv" loaded: 0x7fd45a901540
Try to load glGetShaderInfoLog...
"glGetShaderInfoLog" loaded: 0x7fd45a9014c0
Try to load glLinkProgram...
"glLinkProgram" loaded: 0x7fd45a903de0
Try to load glShaderSource...
"glShaderSource" loaded: 0x7fd45a90af20
Try to load glUseProgram...
"glUseProgram" loaded: 0x7fd45a90e5a0
144668 frames in 5.0 seconds = 28933.479 FPS
146462 frames in 5.0 seconds = 29292.250 FPS
147036 frames in 5.0 seconds = 29407.119 FPS
146011 frames in 5.0 seconds = 29201.236 FPS

With shaders and -02

./compile_and_run.sh
Load glAttachShader: 0x7fc86ba503c0
Load glCreateProgram: 0x7fc86ba53580
Load glCompileShader: 0x7fc86ba52840
Load glCreateShader: 0x7fc86ba53660
Load glGetProgramiv: 0x7fc86ba59040
Load glGetProgramInfoLog: 0x7fc86ba58d20
Load glGetShaderiv: 0x7fc86ba59540
Load glGetShaderInfoLog: 0x7fc86ba594c0
Load glGetUniformLocation: 0x7fc86ba59ea0
Load glLinkProgram: 0x7fc86ba5bde0
Load glShaderSource: 0x7fc86ba62f20
Load glUniform1i: 0x7fc86ba65560
Load glUseProgram: 0x7fc86ba665a0
Load original glXSwapBuffers: 0x7fc86ba4ecb0
Fragment shader created: 1
Fragment shader compiled successfully.
Creating texture with size 300x300
103841 frames in 5.0 seconds = 20768.158 FPS
105598 frames in 5.0 seconds = 21119.492 FPS
105854 frames in 5.0 seconds = 21170.758 FPS
105747 frames in 5.0 seconds = 21149.234 FPS

With LD_PRELOAD and -O2 optimization

./compile_and_run.sh
Load glAttachShader: 0x7fd59db483c0
Load glCreateProgram: 0x7fd59db4b580
Load glCompileShader: 0x7fd59db4a840
Load glCreateShader: 0x7fd59db4b660
Load glGetProgramiv: 0x7fd59db51040
Load glGetProgramInfoLog: 0x7fd59db50d20
Load glGetShaderiv: 0x7fd59db51540
Load glGetShaderInfoLog: 0x7fd59db514c0
Load glLinkProgram: 0x7fd59db53de0
Load glShaderSource: 0x7fd59db5af20
Load glUseProgram: 0x7fd59db5e5a0
145307 frames in 5.0 seconds = 29061.289 FPS
146380 frames in 5.0 seconds = 29275.883 FPS
134868 frames in 5.0 seconds = 26973.420 FPS
143137 frames in 5.0 seconds = 28625.543 FPS
Terminated

License

This project is licensed under the MIT License. See the LICENSE file for details.