Matt's Homepage

In doing some robustness testing, I needed to crash my Linux VM intentionally to see if the rest of the system survived. I was thinking of writing a kernel module that just did something silly like dereference null or divide by zero, but turns out you can do it much easier than that. Just call panic.

panic.c:
#define __NO_VERSION__
#include <linux/version.h>
#include 
#include 

int init_module(void)
{
    panic(" insert lame excuse here");
    return 0;
}

Build with:

 gcc -I/usr/src/linux/include -D__KERNEL__ -DMODULE -o panic.o -c panic.c

Here’s a good link about building kernel modules without full kernel source.

Now, run the following insmod, and your system will kernel panic.

 insmod panic.o 

Credit to Paul’s Journal

Writing the OpenGL context creation plumbing on Linux isn’t 100% intuitive. It’s always good to have a handy getting started guide. With developers increasingly using engines such as Unity, the number of people writing directly to OpenGL is shrinking – and so are some of the online resources to get over this initial step. I decided to collect a few links and copy critical sample code here for when I need to whip something up quickly.

 

Some links to good ‘hello world’ Linux GL samples:
https://github.com/jckarter/hello-gl
https://www.opengl.org/wiki/Tutorial:_OpenGL_3.0_Context_Creation_(GLX)
http://www-f9.ijs.si/~matevz/docs/007-2392-003/sgi_html/ch04.html

 

Code:
Taken from: https://www.opengl.org/sdk/docs/man2/xhtml/glXIntro.xml

Below is a minimal example of creating an RGBA-format X window that’s compatible with OpenGL using GLX 1.3 commands. The window is cleared to yellow when the program runs. The program does minimal error checking; all return values should be checked.

#include < stdio.h >
#include < stdlib.h >
#include < GL/gl.h >
#include < GL/glx.h >

int singleBufferAttributess[] = {
    GLX_DRAWABLE_TYPE, GLX_WINDOW_BIT,
    GLX_RENDER_TYPE,   GLX_RGBA_BIT,
    GLX_RED_SIZE,      1,   /* Request a single buffered color buffer */
    GLX_GREEN_SIZE,    1,   /* with the maximum number of color bits  */
    GLX_BLUE_SIZE,     1,   /* for each component                     */
    None
};

int doubleBufferAttributes[] = {
    GLX_DRAWABLE_TYPE, GLX_WINDOW_BIT,
    GLX_RENDER_TYPE,   GLX_RGBA_BIT,
    GLX_DOUBLEBUFFER,  True,  /* Request a double-buffered color buffer with */
    GLX_RED_SIZE,      1,     /* the maximum number of bits per component    */
    GLX_GREEN_SIZE,    1, 
    GLX_BLUE_SIZE,     1,
    None
};


static Bool WaitForNotify( Display *dpy, XEvent *event, XPointer arg ) {
    return (event->type == MapNotify) && (event->xmap.window == (Window) arg);
}
int main( int argc, char *argv[] )
{
    Display              *dpy;
    Window                xWin;
    XEvent                event;
    XVisualInfo          *vInfo;
    XSetWindowAttributes  swa;
    GLXFBConfig          *fbConfigs;
    GLXContext            context;
    GLXWindow             glxWin;
    int                   swaMask;
    int                   numReturned;
    int                   swapFlag = True;

    /* Open a connection to the X server */
    dpy = XOpenDisplay( NULL );
    if ( dpy == NULL ) {
        printf( "Unable to open a connection to the X servern" );
        exit( EXIT_FAILURE );
    }

    /* Request a suitable framebuffer configuration - try for a double 
    ** buffered configuration first */
    fbConfigs = glXChooseFBConfig( dpy, DefaultScreen(dpy),
                                   doubleBufferAttributes, &numReturned );

    if ( fbConfigs == NULL ) {  /* no double buffered configs available */
      fbConfigs = glXChooseFBConfig( dpy, DefaultScreen(dpy),
                                     singleBufferAttributess, &numReturned );
      swapFlag = False;
    }

    /* Create an X colormap and window with a visual matching the first
    ** returned framebuffer config */
    vInfo = glXGetVisualFromFBConfig( dpy, fbConfigs[0] );

    swa.border_pixel = 0;
    swa.event_mask = StructureNotifyMask;
    swa.colormap = XCreateColormap( dpy, RootWindow(dpy, vInfo->screen),
                                    vInfo->visual, AllocNone );

    swaMask = CWBorderPixel | CWColormap | CWEventMask;

    xWin = XCreateWindow( dpy, RootWindow(dpy, vInfo->screen), 0, 0, 256, 256,
                          0, vInfo->depth, InputOutput, vInfo->visual,
                          swaMask, &swa );

    /* Create a GLX context for OpenGL rendering */
    context = glXCreateNewContext( dpy, fbConfigs[0], GLX_RGBA_TYPE,
				 NULL, True );

    /* Create a GLX window to associate the frame buffer configuration
    ** with the created X window */
    glxWin = glXCreateWindow( dpy, fbConfigs[0], xWin, NULL );
    
    /* Map the window to the screen, and wait for it to appear */
    XMapWindow( dpy, xWin );
    XIfEvent( dpy, &event, WaitForNotify, (XPointer) xWin );

    /* Bind the GLX context to the Window */
    glXMakeContextCurrent( dpy, glxWin, glxWin, context );

    /* OpenGL rendering ... */
    glClearColor( 1.0, 1.0, 0.0, 1.0 );
    glClear( GL_COLOR_BUFFER_BIT );

    glFlush();
    
    if ( swapFlag )
        glXSwapBuffers( dpy, glxWin );

    sleep( 10 );
    exit( EXIT_SUCCESS );
}