lkml.org 
[lkml]   [2018]   [Apr]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH] powerpc: Allow selection of CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
On Tue, Apr 17, 2018 at 6:49 PM, Christophe LEROY
<christophe.leroy@c-s.fr> wrote:
>
>
> Le 17/04/2018 à 18:45, Mathieu Malaterre a écrit :
>>
>> On Tue, Apr 17, 2018 at 12:49 PM, Christophe Leroy
>> <christophe.leroy@c-s.fr> wrote:
>>>
>>> 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
>>> filesz 0x0036eda4 memsz 0x0038de04 flags rwx
>>>
>>> Program Header after the patch:
>>> LOAD off 0x00010000 vaddr 0xc0000000 paddr 0x00000000 align 2**16
>>> filesz 0x00316da4 memsz 0x00334268 flags rwx
>>>
>>> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
>>> ---
>>> 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 active
> ?

$ 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
>
>
>>
>> ---
>> 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 ...
>> _
>> ---
>>
>>
>>
>>> config ISA_DMA_API
>>> --
>>> 2.13.3
>>>
>

\
 
 \ /
  Last update: 2018-04-17 19:12    [W:0.065 / U:0.064 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site