x86 Linux assembler
The last few days I’ve been looking at x86 Linux assembler programming. I think it’s important to know how the code which you write in higher-level languages gets translated to low-level instructions and in what way things like libc or the kernel are involved. With some knowledge of assembler you can not only directly optimize some slower operations by implementing them in low-level assembly and by utilizing specific processor features, but in general you will also learn in which ways you can optimize your software by just writing the high-level code a little bit different – by anticipating how your code will translate into low-level assembler instructions.
That was my motivation for trying to do a few things with the Netwide Assembler (NASM). The result is a simple demo which utilizes libc, GLUT and OpenGL to display a rotating pyramid and cube.
compiled ogl.asm application running in Ubuntu 8.04
The resulting code can be viewed here:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 | ; OpenGL example in x86 Linux assembler / NASM using Glut ; Author: Wesley Stessens (wesley@ubuntu.com) ; ; OpenGL calls to create pyramid and cube are from Jeff Molofee's OpenGL tutorial ; See: http://nehe.gamedev.net/data/lessons/lesson.asp?lesson=05 ; ; Features: ; - Calling C functions by cdecl conventions ; - Using GLUT and OpenGL calls to perform 3D graphics ; - Low-level framerate control ; ; Sample compile instructions: ; nasm -felf ogl.asm && ld -lglut -s -I/lib/ld-linux.so.2 -o ogl ogl.o ; ; This code is released as sample code in the public domain. Use it for whatever you want. ; Feel free to let me know if you found this code useful in any way. ; Glut extern glutInit, glutInitDisplayMode, glutInitWindowSize, glutInitWindowPosition extern glutCreateWindow, glutMainLoop extern glutDisplayFunc, glutIdleFunc, glutReshapeFunc, glutKeyboardFunc extern glutSwapBuffers ; Glu extern gluPerspective ; OpenGL extern glClearColor, glClearDepth, glDepthFunc, glEnable, glShadeModel extern glClear, glLoadIdentity, glMatrixMode, glViewport extern glTranslatef, glRotatef, glBegin, glEnd, glVertex3f, glColor3f ; Needed for framerate control extern usleep ; Macros %macro _3call 4 push dword %4 push dword %3 push dword %2 call %1 add esp, 12 %endmacro %macro _4call 5 push dword %5 push dword %4 push dword %3 push dword %2 call %1 add esp, 16 %endmacro section .data title: db 'OpenGL in x86 Linux assembler / NASM using Glut', 0 ; Data for FP math with 4 bytes n7: dd -7.0 n6: dd -6.0 n1p5: dd -1.5 n1: dd -1.0 p0p4: dd 0.4 p0p5: dd 0.5 p1: dd 1.0 p1p5: dd 1.5 p3: dd 3.0 rottrm: dd 4.5 rotsqm: dd -3.0 ; Data for FP math with 8 bytes q0p1: dq 0.1 q1: dq 1.0 q45: dq 45.0 q100: dq 100.0 ; Data for framerate control mspf: dd 20000 ; ms per frame section .bss ; Vars for rotation rottr: resd 1 rotsq: resd 1 ; Var for aspect ratio aspr: resq 1 ; Vars for framerate control time: resd 2 usecs: resd 1 oldslp: resd 1 section .text global _start fpsmanager: push eax push ebx push ecx push edx mov eax, 78 ; sys_gettimeofday mov ebx, time mov ecx, 0 int 80h mov eax, [time + 4] sub eax, [usecs] mov ebx, [mspf] sub ebx, eax test eax, eax js keep_sleep test ebx, ebx js keep_sleep push ebx call usleep add esp, 4 mov dword [oldslp], ebx jmp done_sleep keep_sleep: push dword [oldslp] call usleep add esp, 4 done_sleep: mov eax, [time + 4] mov dword [usecs], eax pop edx pop ecx pop ebx pop eax ret display: ; Prepare for drawing push dword 4100h ; GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT call glClear add esp, 4 call glLoadIdentity ; Draw pyramid on the left of the screen _3call glTranslatef, [n1p5], 0, [n6] _4call glRotatef, [rottr], 0, [p1], 0 push dword 9h ; GL_POLYGON call glBegin add esp, 4 _3call glColor3f, [p1], 0, 0 ; Start drawing front face _3call glVertex3f, 0, [p1], 0 _3call glColor3f, 0, [p1], 0 _3call glVertex3f, [n1], [n1], [p1] _3call glColor3f, 0, 0, [p1] _3call glVertex3f, [p1], [n1], [p1] _3call glColor3f, [p1], 0, 0 ; Start drawing right face _3call glVertex3f, 0, [p1], 0 _3call glColor3f, 0, 0, [p1] _3call glVertex3f, [p1], [n1], [p1] _3call glColor3f, 0, [p1], 0 _3call glVertex3f, [p1], [n1], [n1] _3call glColor3f, [p1], 0, 0 ; Start drawing back face _3call glVertex3f, 0, [p1], 0 _3call glColor3f, 0, [p1], 0 _3call glVertex3f, [p1], [n1], [n1] _3call glColor3f, 0, 0, [p1] _3call glVertex3f, [n1], [n1], [n1] _3call glColor3f, [p1], 0, 0 ; Start drawing right face _3call glVertex3f, 0, [p1], 0 _3call glColor3f, 0, 0, [p1] _3call glVertex3f, [n1], [n1], [n1] _3call glColor3f, 0, [p1], 0 _3call glVertex3f, [n1], [n1], [p1] call glEnd ; Draw cube on the right of the screen call glLoadIdentity _3call glTranslatef, [p1p5], 0, [n7] _4call glRotatef, [rotsq], [p1], [p0p4], [p0p5] push dword 7h ; GL_QUADS call glBegin add esp, 4 _3call glColor3f, 0, [p1], 0 ; Start drawing top face _3call glVertex3f, [p1], [p1], [n1] _3call glVertex3f, [n1], [p1], [n1] _3call glVertex3f, [n1], [p1], [p1] _3call glVertex3f, [p1], [p1], [p1] _3call glColor3f, [p1], [p0p5], 0 ; Start drawing bottom face _3call glVertex3f, [p1], [n1], [p1] _3call glVertex3f, [n1], [n1], [p1] _3call glVertex3f, [n1], [n1], [n1] _3call glVertex3f, [p1], [n1], [n1] _3call glColor3f, [p1], 0, 0 ; Start drawing front face _3call glVertex3f, [p1], [p1], [p1] _3call glVertex3f, [n1], [p1], [p1] _3call glVertex3f, [n1], [n1], [p1] _3call glVertex3f, [p1], [n1], [p1] _3call glColor3f, [p1], [p1], 0 ; Start drawing back face _3call glVertex3f, [p1], [n1], [n1] _3call glVertex3f, [n1], [n1], [n1] _3call glVertex3f, [n1], [p1], [n1] _3call glVertex3f, [p1], [p1], [n1] _3call glColor3f, 0, 0, [p1] ; Start drawing left face _3call glVertex3f, [n1], [p1], [p1] _3call glVertex3f, [n1], [p1], [n1] _3call glVertex3f, [n1], [n1], [n1] _3call glVertex3f, [n1], [n1], [p1] _3call glColor3f, [p1], 0, [p1] ; Start drawing right face _3call glVertex3f, [p1], [p1], [n1] _3call glVertex3f, [p1], [p1], [p1] _3call glVertex3f, [p1], [n1], [p1] _3call glVertex3f, [p1], [n1], [n1] call glEnd ; Update rotation fld dword [rottr] fadd dword [rottrm] fstp dword [rottr] fld dword [rotsq] fadd dword [rotsqm] fstp dword [rotsq] call glutSwapBuffers ; Swap buffers and display call fpsmanager ; Cap framerate if necessary ret reshape: push ebp mov ebp, esp ; Prevent division by zero cmp dword [ebp+8], 0 jne reshape_2 inc dword [ebp+8] reshape_2: fild dword [ebp+8] fidiv dword [ebp+12] fstp qword [aspr] push dword [ebp+12] push dword [ebp+8] push dword 0 push dword 0 call glViewport add esp, 16 push dword 1701h; GL_PROJECTION call glMatrixMode add esp, 4 call glLoadIdentity push dword [q100+4] push dword [q100] push dword [q0p1+4] push dword [q0p1] push dword [aspr+4] push dword [aspr] push dword [q45+4] push dword [q45] call gluPerspective add esp, 32 push dword 1700h; GL_MODELVIEW call glMatrixMode add esp, 4 pop ebp ret keyhandler: ret _start: ; Initialize glut push dword [esp+8] lea eax, [esp+8] push eax call glutInit add esp, 8 push dword 1ah ; GLUT_RGBA|GLUT_DOUBLE|GLUT_ALPHA|GLUT_DEPTH call glutInitDisplayMode add esp, 4 push dword 480 push dword 640 call glutInitWindowSize add esp, 8 push dword 0 push dword 0 call glutInitWindowPosition add esp, 8 ; Create window push title call glutCreateWindow add esp, 4 ; Register functions push display call glutDisplayFunc call glutIdleFunc add esp, 4 push reshape call glutReshapeFunc add esp, 4 push keyhandler call glutKeyboardFunc add esp, 4 ; Initialize OpenGL push dword 0 push dword 0 push dword 0 push dword 0 call glClearColor add esp, 16 push dword [q1+4] push dword [q1] call glClearDepth add esp, 8 push dword 203h; GL_LEQUAL call glDepthFunc add esp, 4 push dword 0b71h; GL_DEPTH_TEST call glEnable add esp, 4 push dword 1d01h; GL_SMOOTH call glShadeModel add esp, 4 ; Frame rate cap initialization mov dword [oldslp], 0 ; Enter main loop call glutMainLoop ; Exit (return with error code 0) mov eax, 1 ; sys_exit mov ebx, 0 int 80h |
I have also written two other smaller examples:
- marketing.asm is a really simple statistics application which calculates the ideal sample size given a few parameters
- alsawav.asm is a simple audio library which utilizes ALSA to play an unbuffered raw WAV/PCM sample
Please note that all these examples require an x86 Linux distribution. These examples will not work on any other operating system.
Categories: Assembler, Linux, OpenGL, Programming
Nice work
I’ve noticed that your statistics application is littler than mine written in C++. A little investigation reveals that your ASM app is working out of the box. Keep up the good work
Thanks. Of course I couldn’t have done it without your C++ application, from which I stole the formula
Thanks. Nice example.