lkml.org 
[lkml]   [2010]   [Dec]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    Date
    SubjectRe: [PATCH] Built kernel without -O2 option
    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?).

    Thanks,
    Hui
    --
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2010-12-01 14:13    [W:0.034 / U:0.008 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site