In this way, you will got a lot of error. Hui On Mon, Nov 29, 2010 at 16:41, 乔崇 <qiaochong@xxxxxxxxxxx> wrote: > does not need change kernel,just write a shell mycc as bellow: > > #!/bin/sh > gcc "$@" -O0 > > then > > make CC=./mycc vmlinux > > Hui Zhu said > > On Mon, Nov 29, 2010 at 16:16, Américo Wang <xiyou.wangcong@xxxxxxxxx> > wrote: > > > 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. > > > If they really need O2, I set them to O2. > Actually, this is the main work, find out the file that need the O2. :) > > For example: > ifdef CONFIG_CC_CLOSE_OPTIMIZATION > CFLAGS_fpu.o += -O2 > CFLAGS_aesni-intel_glue.o += -O2 > CFLAGS_ghash-clmulni-intel_glue.o += -O2 > endif > > And I will try to find more of these type files. > > > > Also, what is size of vmlinux before applying your patch and after that? > Does it increase too much? > > > > Before the patch: > ls -alh vmlinuz-2.6.37-rc3+ > -rw-r--r-- 1 root root 4.1M 2010-11-25 12:02 vmlinuz-2.6.37-rc3+ > ls -alh b26no/vmlinux > -rwxr-xr-x 1 teawater teawater 135M 2010-11-25 13:31 b26no/vmlinux > > After the patch: > ls -alh vmlinuz-2.6.37-rc3debug+ > -rw-r--r-- 1 root root 4.6M 2010-11-25 14:02 vmlinuz-2.6.37-rc3debug+ > ls -alh b26/vmlinux > -rwxr-xr-x 1 teawater teawater 140M 2010-11-25 11:14 b26/vmlinux > > Thanks, > Hui > > > > > -- > > 乔崇 qiaochong@xxxxxxxxxxx > > 2010年 11月 29日 星期一 16:35:38 CST