Rebuild a changed kernel quickly with make?

[David kiarie]

On Thu, Jul 4, 2013 at 9:53 AM, Warlich, Christof <
christof.warlich at siemens.com> wrote:

> > When I change something in the kernel and just hit make from toplevel
> > dir, it always compiles everything again, no matter if it wasn't changed
> > at all in the meantime.
> > I thought make should be able to make a second build time really quick.
> > What am I doing wrong? Is there a make target I don't know of? I don't
> > type in any, just make.
>
> Are you sure it rebuilds _everything_, i.e. as in a fresh build or after a
> "make clean?"
>
> When I rerun make without changing anything, it just does the following,
> which is much
> Less than a complete build:
>
> $ make
> make -C /root/views/DCUOS_3/derived/tdc/kernel
> O=/root/views/DCUOS_3/derived/tdc/kernelObjects/.
>   Using /root/views/DCUOS_3/derived/tdc/kernel as source for kernel
>   GEN     /root/views/DCUOS_3/derived/tdc/kernelObjects/Makefile
>   CHK     include/linux/version.h
>   CHK     include/linux/utsrelease.h
>   SYMLINK include/asm -> include/asm-x86
>   CALL    /root/views/DCUOS_3/derived/tdc/kernel/scripts/checksyscalls.sh
>   CHK     include/linux/compile.h
>   VDSOSYM arch/x86/vdso/vdso32-int80-syms.lds
>   VDSOSYM arch/x86/vdso/vdso32-sysenter-syms.lds
>   VDSOSYM arch/x86/vdso/vdso32-syms.lds
>   LD      arch/x86/vdso/built-in.o
>   LD      arch/x86/built-in.o
>   LD      vmlinux.o
>   MODPOST vmlinux.o
>   GEN     .version
>   CHK     include/linux/compile.h
>   UPD     include/linux/compile.h
>   CC      init/version.o
>   LD      init/built-in.o
>   LD      .tmp_vmlinux1
>   KSYM    .tmp_kallsyms1.S
>   AS      .tmp_kallsyms1.o
>   LD      .tmp_vmlinux2
>   KSYM    .tmp_kallsyms2.S
>   AS      .tmp_kallsyms2.o
>   LD      vmlinux
>   SYSMAP  System.map
>   SYSMAP  .tmp_System.map
>   VOFFSET arch/x86/boot/voffset.h
>   OBJCOPY arch/x86/boot/compressed/vmlinux.bin
>   GZIP    arch/x86/boot/compressed/vmlinux.bin.gz
>   MKPIGGY arch/x86/boot/compressed/piggy.S
>   AS      arch/x86/boot/compressed/piggy.o
>   LD      arch/x86/boot/compressed/vmlinux
>   ZOFFSET arch/x86/boot/zoffset.h
>   AS      arch/x86/boot/header.o
>   CC      arch/x86/boot/version.o
>   LD      arch/x86/boot/setup.elf
>   OBJCOPY arch/x86/boot/setup.bin
>   OBJCOPY arch/x86/boot/vmlinux.bin
>   BUILD   arch/x86/boot/bzImage
> Root device is (8, 5)
> Setup is 11148 bytes (padded to 11264 bytes).
> System is 1759 kB
> CRC f583db84
> Kernel: arch/x86/boot/bzImage is ready  (#3)
>   Building modules, stage 2.
>   MODPOST 1 modules
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Am also pretty sure it does not compile everything.
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