linux-kernel - Re: [hellogcc] Re: [PATCH] Built kernel without -O2 option

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Message-ID: <AANLkTimGn53kwcTYe41Y-fwTQ0vzShLCr3LAr8yW9p=J@mail.gmail.com>
Date:	Wed, 1 Dec 2010 20:23:10 +0800
From:	bekars <bekars@...il.com>
To:	hellogcc@...elists.org
Cc:	Américo Wang <xiyou.wangcong@...il.com>,
	linux-kernel@...r.kernel.org, gdb@...rceware.org
Subject: Re: [hellogcc] Re: [PATCH] Built kernel without -O2 option

这个好像不行，我在2.6.35.4内核上编译，报错：

  ./mm.sh -Wp,-MD,arch/x86/kernel/.entry_32.o.d  -nostdinc -isystem
/usr/lib/gcc/i486-linux-gnu/4.3.2/include
-I/home/baiyu/Melon/RSW3/base_system/linux.DEV/LKGDB/arch/x86/include
-Iinclude  -include include/generated/autoconf.h -D__KERNEL__
-D__ASSEMBLY__ -m32 -DCONFIG_AS_CFI=1 -DCONFIG_AS_CFI_SIGNAL_FRAME=1
-DCONFIG_AS_CFI_SECTIONS=1  -gdwarf-2        -c -o
arch/x86/kernel/entry_32.o arch/x86/kernel/entry_32.S
/home/baiyu/Melon/RSW3/base_system/linux.DEV/LKGDB/arch/x86/include/asm/dwarf2.h:
Assembler messages:
/home/baiyu/Melon/RSW3/base_system/linux.DEV/LKGDB/arch/x86/include/asm/dwarf2.h:46:
Error: unknown pseudo-op: `.cfi_sections'
/home/baiyu/Melon/RSW3/base_system/linux.DEV/LKGDB/arch/x86/include/asm/dwarf2.h:
Assembler messages:
/home/baiyu/Melon/RSW3/base_system/linux.DEV/LKGDB/arch/x86/include/asm/dwarf2.h:46:
Error: unknown pseudo-op: `.cfi_sections'
/home/baiyu/Melon/RSW3/base_system/linux.DEV/LKGDB/arch/x86/include/asm/dwarf2.h:
Assembler messages:
/home/baiyu/Melon/RSW3/base_system/linux.DEV/LKGDB/arch/x86/include/asm/dwarf2.h:46:
Error: unknown pseudo-op: `.cfi_sections'
make[2]: *** [arch/x86/kernel/entry_32.o] Error 1
make[1]: *** [arch/x86/kernel] Error 2
make: *** [arch/x86] Error 2



在 2010年11月29日 下午5:45，乔崇 <qiaochong@...ngson.cn> 写道：
> Hui Zhu 写道:
>> In this way, you will got a lot of error.
>>
>> Hui
>>
>> On Mon, Nov 29, 2010 at 16:41, 乔崇 <qiaochong@...ngson.cn> wrote:
>>
>>> does not need change kernel,just write a shell mycc as bellow:
>>>
>>> #!/bin/sh
>>> gcc "$@" -O0
>>>
>>>
> change mycc to this will work,:)
>
> #!/bin/sh
> gcc "$@" -O0 ||
>  gcc "$@" -O1 ||
>  gcc "$@"
>
>
>>> then
>>>
>>> make CC=./mycc vmlinux
>>>
>>> Hui Zhu said
>>>
>>> On Mon, Nov 29, 2010 at 16:16, Américo Wang <xiyou.wangcong@...il.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@...ngson.cn
>>>
>>> 2010年 11月 29日 星期一 16:35:38 CST
>>>
>>
>>
>>
>
>
> --
>
> 乔崇 qiaochong@...ngson.cn
> 龙芯中科技术服务中心有限公司
> office:010-62600855-615
> mobile:13521990614
>
> 2010年 11月 29日 星期一 17:38:14 CST
>
>
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