Re: [PATCH 4/4] powerpc: Allow LD_DEAD_CODE_DATA_ELIMINATION to be selected

Nicholas Piggin
2018-04-20T10:37:10Z

On Fri, 20 Apr 2018 12:01:34 +0200
Christophe LEROY <christophe.leroy@c-s.fr> wrote:

> Le 20/04/2018 à 09:34, Nicholas Piggin a écrit :
> > This requires further changes to linker script to KEEP some tables
> > and wildcard compiler generated sections into the right place. This
> > includes pp32 modifications from Christophe Leroy.
> >
> > When compiling powernv_defconfig with this option:
> >
> > text data bss dec filename
> > 11827621 4810490 1341080 17979191 vmlinux
> > 11752437 4598858 1338776 17690071 vmlinux.dcde
> >
> > Resulting kernel is almost 400kB smaller (and still boots).
> >
> > [ppc32 numbers here]
> >
> > Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> > ---
> > arch/powerpc/Kconfig | 1 +
> > arch/powerpc/kernel/vmlinux.lds.S | 22 +++++++++++-----------
> > 2 files changed, 12 insertions(+), 11 deletions(-)
> >
> > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> > index c32a181a7cbb..ee6dbe2efc8b 100644
> > --- a/arch/powerpc/Kconfig
> > +++ b/arch/powerpc/Kconfig
> > @@ -205,6 +205,7 @@ config PPC
> > select HAVE_KPROBES
> > select HAVE_KPROBES_ON_FTRACE
> > select HAVE_KRETPROBES
> > + select HAVE_LD_DEAD_CODE_DATA_ELIMINATION
> > select HAVE_LIVEPATCH if HAVE_DYNAMIC_FTRACE_WITH_REGS
> > select HAVE_MEMBLOCK
> > select HAVE_MEMBLOCK_NODE_MAP
> > diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
> > index c8af90ff49f0..89381dc959ce 100644
> > --- a/arch/powerpc/kernel/vmlinux.lds.S
> > +++ b/arch/powerpc/kernel/vmlinux.lds.S
> > @@ -89,7 +89,7 @@ SECTIONS
> > */
> > .text BLOCK(0) : AT(ADDR(.text) - LOAD_OFFSET) {
> > #ifdef CONFIG_LD_HEAD_STUB_CATCH
> > - *(.linker_stub_catch);
> > + KEEP(*(.linker_stub_catch));
> > . = . ;
> > #endif
> >
> > @@ -98,7 +98,7 @@ SECTIONS
> > ALIGN_FUNCTION();
> > #endif
> > /* careful! __ftr_alt_* sections need to be close to .text */
> > - *(.text.hot .text .text.fixup .text.unlikely .fixup __ftr_alt_* .ref.text);
> > + *(.text.hot .text .text.[0-9a-zA-Z_]* .text.fixup .text.unlikely .fixup __ftr_alt_* .ref.text);
>
> Why not use TEXT_MAIN here instead of .text .text.[0-9a-zA-Z_]* ?

It's from my early patch before we added those in the generic linker
script. Yes your version looks nicer.

Thanks,
Nick