Messages in this thread | ![/](/images/icornerl.gif) | | Subject | Re: [hellogcc] Re: [PATCH] Built kernel without -O2 option | From | Steven <> | Date | Mon, 29 Nov 2010 16:55:29 +0800 |
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I replace -O2 with -O0 in Makefile of kernel source code root directory? I just do it and my gdb works well with this method.
You mean it is not enough?
Steven
On Mon, 2010-11-29 at 16:47 +0800, Hui Zhu wrote: > In this way, you will got a lot of error. > > Hui > > On Mon, Nov 29, 2010 at 16:41, 乔崇 <qiaochong@loongson.cn> 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@gmail.com> > > 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@loongson.cn > > > > 2010年 11月 29日 星期一 16:35:38 CST
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