On Dec 8, 2011, at 1:25 PM, Rik Cabanier wrote: > This might no longer be true, but isn't it the case that shaders are designed > to take the same amount of time to execute, no matter what input they get? > ie if you have an if/else block, the time of the shader would be whatever > block takes the longest. This was done so you can schedule many of them at > the same time without having to worry about synchronizing them. > > Rik
That was only true in the early days of GLSL, etc when the hardware did not actually support branching. Now the hardware does support branching so these timing attacks are relatively trivial (see http://www.contextis.co.uk/resources/blog/webgl/poc/index.html). --Oliver _______________________________________________ webkit-dev mailing list webkit-dev@lists.webkit.org http://lists.webkit.org/mailman/listinfo.cgi/webkit-dev
