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    SubjectRe: [PATCH] Built kernel without -O2 option
    On Mon, Nov 29, 2010 at 17:59, Andi Kleen <andi@firstfloor.org> wrote:
    > Hui Zhu <teawater@gmail.com> writes:
    >
    >> 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.
    >
    > Really the right place to fix a lot of this would be gcc (and perhaps
    > gdb). I suspect with some careful work the debugging experience
    > for -O2 could be improved a lot.
    > I also believe the latest gccs already have improvements in this area.
    >

    If you think they are OK, go get a new gcc and try. :)

    >>
    >> 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.
    >
    >
    > You need to at least keep aggressive inlining for header files,
    > otherwise there will be too much code bloat and bad code.
    >
    > Like -O1 -finline-functions ?
    >

    If I can build OK, why I need add some options?

    Thanks,
    Hui
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