Dear gcc guys: Is there another way to p/x variables of kernel except I re-compile the it with the latest GCC? appreciate your help, miloody ---------- Forwarded message ---------- From: Jan Kratochvil Date: 2010/7/9 Subject: Re: some questions about kernel debugging To: loody On Fri, 09 Jul 2010 13:52:31 +0200, loody wrote: > I enable kernel hacking options about kernel debugging on my mips platform. > I can successfully connect to the target board. > My question is: > 1. why I cannot p/x the value of variable? > I have enabled CONFIG_ARCH_WANT_FRAME_POINTERS and CONFIG_FRAME_POINTER > but I still get the message which tell me "value optimized out". > did I miss anything? > my kernel version is 2.6.30.9? This is not a GDB problem, you should report it to GCC (you need a minimal reproducer for the bugreport). The problem is Linux kernel cannot (at least could not) compile with -O0, it requires -O2 to successfully build. -O2 was always mostly unsupported together with -g (=debuggingo information). For -O2 -g you should use the latest GCC - SVN HEAD best - and definitely at least 4.5 (for VTA - var-tracking-assignments). Besides resolving this -O2 -g problem at GCC the easy way is always to just `disassemble' the code in GDB, guess from the code+source in which register/memory is the value probably located and access it directly there. Regards, Jan
