Am 29.11.2010 09:16, schrieb Américo Wang: > On Mon, Nov 29, 2010 at 11:56:15AM +0800, Hui Zhu wrote: >> Hi, >> >> Now, there are a lot of ways to debug the Linux kernel with GDB, like >> qemu, kgtp or kgdb and so on. >> But the developer more like add a printk. It have a lot of reason, a big one is: >> (gdb) p ret >> $3 = <value optimized out> >> And the code execution order is not right. >> >> This is becuase the Kernel is bult with gcc -O2. Gcc will not >> generate enough debug message with file with -O2. >> So GDB cannot work very well with Linux kernel. >> >> So I make a patch that add a option in "Kernel hacking" called "Close >> GCC optimization". It will make kernel be built without -O2. >> >> I built and use it in i386 and x86_64. I will try to make it OK in other arch. >> > > The problem is that some functions _have to_ be inlined and gcc without -O2 > doesn't inline them. Have check all the cases? I doubt. In essence -O2 just tells gcc to activate a list of optimizations gcc -Q -O2 --help=optimizers tells you what. So what about making this patch much smaller by explicitely using the optimizations that are absolutely necessary? e.g: -finline-small-functions -finline-functions-called-once (what else do we need?) We might even be able to collapse this with the optimize for size option, by providing a Kconfig entry that allows to choose between -O0 -finline-small-functions -finline-functions-called-once -O1 -finline-small-functions -finline-functions-called-once -Os -O2 -O3 Christian -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
