On Tue, Feb 14, 2012 at 5:50 AM, Ian Campbell Ian.Campbell@citrix.com wrote:
On Mon, 2012-02-13 at 23:21 +0900, Daniel Castro wrote:
I have encountered something a little strange, if I set up the debug lvl to 3 or more Y will get a Triple VCPU fault. If I set it to 1 the bios runs normally but I loose a lot of information that I need to debug. Sometimes if I try to print char * variables regardless of the debug level I still get the fault.
Any ideas why?
My guess is that there is a debug print at lvl>=3 which ends up dereferencing a NULL pointer in one of its arguments (probably a %s) and this leads to a page fault. This in turn leads to a double fault because SeaBIOS does not install a page fault handler and then a triple fault because it also does not install a double fault handler. Likewise when you are printing "char * variables regardless of the debug level".
You could test this by adding an explicit check for null in the bit of bvprintf which handles %s, perhaps putc()ing "(null)" instead.
Thanks for the response, I will try what you suggest.
Thanks for the ideas/pointers/ anything!