Messages in this thread | | | From | Hui Zhu <> | Date | Wed, 1 Dec 2010 21:10:51 +0800 | Subject | Re: [PATCH] Built kernel without -O2 option |
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On Tue, Nov 30, 2010 at 05:07, Arnaud Lacombe <lacombar@gmail.com> wrote: > Hi, > > On Sun, Nov 28, 2010 at 10:56 PM, Hui Zhu <teawater@gmail.com> 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 >> $3 = <value optimized out> >> And the code execution order is not right. >> >> This is becuase the Kernel is bult with gcc -O2. Gcc will not >> generate enough debug message with file with -O2. >> So GDB cannot work very well with Linux kernel. >> >> So I make a patch that add a option in "Kernel hacking" called "Close >> GCC optimization". It will make kernel be built without -O2. >> > no, it does not, see below .. > >> I built and use it in i386 and x86_64. I will try to make it OK in other arch. >> >> And I will put new patch in here and >> http://code.google.com/p/kgtp/downloads/list >> >> Thanks, >> Hui >> >> Signed-off-by: Hui Zhu <teawater@gmail.com> >> --- >> [...] >> +ifdef CONFIG_CC_CLOSE_OPTIMIZATION >> +CFLAGS_process_$(BITS).o += -O2 >> +CFLAGS_entry_$(BITS).o += -O2 >> +CFLAGS_traps.o += -O2 >> +CFLAGS_i387.o += -O2 >> +CFLAGS_xsave.o += -O2 >> +CFLAGS_hpet.o += -O2 >> +endif >> >> [...] >> >> --- a/lib/Kconfig.debug >> +++ b/lib/Kconfig.debug >> @@ -136,6 +136,14 @@ config DEBUG_SECTION_MISMATCH >> - Enable verbose reporting from modpost to help solving >> the section mismatches reported. >> >> +config CC_CLOSE_OPTIMIZATION >> + bool "Close GCC optimization" >> + default n >> + help >> + Enabling this option will let gcc build kernel without "-O2". >> + >> + If unsure, say N. >> + > You are not consistent with yourself, you add an option saying "do not > build the kernel with -O2" and yet, you add "-O2" flags for unknown > reason all over the tree... > > - Arnaud >
You are really good at English. But not mathematics.
Add -O2 to build 30 files is better than add -O2 to all files(who know how much files in Linux Kernel?).
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