On Tue, Apr 17, 2018 at 6:49 PM, Christophe LEROY
[off-list ref] wrote:

Le 17/04/2018 =C3=A0 18:45, Mathieu Malaterre a =C3=A9crit :

quoted

On Tue, Apr 17, 2018 at 12:49 PM, Christophe Leroy
[off-list ref] wrote:

quoted

This option does dead code and data elimination with the linker by
compiling with -ffunction-sections -fdata-sections and linking with
--gc-sections.

By selecting this option on mpc885_ads_defconfig,
vmlinux LOAD segment size gets reduced by 10%

Program Header before the patch:
     LOAD off    0x00010000 vaddr 0xc0000000 paddr 0x00000000 align 2**=

16

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          filesz 0x0036eda4 memsz 0x0038de04 flags rwx

Program Header after the patch:
     LOAD off    0x00010000 vaddr 0xc0000000 paddr 0x00000000 align 2**=

16

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          filesz 0x00316da4 memsz 0x00334268 flags rwx

Signed-off-by: Christophe Leroy <redacted>
---
  arch/powerpc/Kconfig | 8 ++++++++
  1 file changed, 8 insertions(+)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 8fe4353be5e3..e1fac49cf465 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig

@@ -888,6 +888,14 @@ config PPC_MEM_KEYS

           If unsure, say y.

+config PPC_UNUSED_ELIMINATION
+       bool "Eliminate unused functions and data from vmlinux"
+       default n
+       select LD_DEAD_CODE_DATA_ELIMINATION
+       help
+         Select this to do dead code and data elimination with the

linker
+         by compiling with -ffunction-sections -fdata-sections and
linking
+         with --gc-sections.
  endmenu

Just for reference, I cannot boot my Mac Mini G4 anymore (yaboot). The
messages I can see (prom_init) are:

Which version of GCC do you use ?

$ powerpc-linux-gnu-gcc --version
powerpc-linux-gnu-gcc (Debian 6.3.0-18) 6.3.0 20170516
Copyright (C) 2016 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

this is simply coming from:

$ apt-cache policy crossbuild-essential-powerpc
crossbuild-essential-powerpc:
  Installed: 12.3
  Candidate: 12.3
  Version table:
 *** 12.3 500
        500 http://ftp.fr.debian.org/debian stretch/main amd64 Packages
        500 http://ftp.fr.debian.org/debian stretch/main i386 Packages
        100 /var/lib/dpkg/status

Can you provide the generated System.map with and without that option act=

ive

?

$ du -sh g4/System.map.*
1.7M g4/System.map.with
1.8M g4/System.map.without

Will send them by private emails.

Thanks
Christophe

quoted

---
done
copying OF device tree...
Building dt strings...
Building dt structure...
Device tree strings 0x01100000 -> 0x01100e02
Device tree struct   0x01101000 -> 0x01109000
Quiescing Open Firmware ...
Booting Linux via __start() @ 0x00140000 ...
_
---

quoted

  config ISA_DMA_API
--
2.13.3