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From: Christophe Leroy <christophe.leroy@c-s.fr>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>,
	Michael Ellerman <mpe@ellerman.id.au>
Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: [PATCH v2 2/2] powerpc: Allow selection of CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
Date: Wed, 18 Apr 2018 15:36:05 +0200 (CEST)	[thread overview]
Message-ID: <0051d3c950c957983c018230b7fd3c7ddde513f7.1524055122.git.christophe.leroy@c-s.fr> (raw)
In-Reply-To: <fe9959328efb520e6030476553ed23541c547639.1524055122.git.christophe.leroy@c-s.fr>

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
 
 config ISA_DMA_API
-- 
2.13.3

      reply	other threads:[~2018-04-18 13:36 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-18 13:36 [PATCH v2 1/2] powerpc: fix vmlinux.lds to build with CONFIG_LD_DEAD_CODE_DATA_ELIMINATION Christophe Leroy
2018-04-18 13:36 ` Christophe Leroy [this message]

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