On Mon, Nov 29, 2010 at 17:44, Christian Borntraeger <borntraeger@xxxxxxxxxx> wrote: > 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 > Hi Christian. If we can build without any optimization options just set some file to O2. I think keep it it will better than add some optimization options to all files, right? But make for this file that I add O2 to them, I can change them to to some others options like "-O0 -finline-small-functions -finline-functions-called-once". Thanks, Hui -- 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
