[PATCH v2 1/2] powerpc: fix vmlinux.lds to build with CONFIG_LD_DEAD_CODE_DATA_ELIMINATION

[PATCH v2 1/2] powerpc: fix vmlinux.lds to build with CONFIG_LD_DEAD_CODE_DATA_ELIMINATION

[Christophe Leroy]

This patch fixes vmlinux.lds script to build properly with
CONFIG_LD_DEAD_CODE_DATA_ELIMINATION enabled

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 arch/powerpc/kernel/vmlinux.lds.S | 4 ++--
 include/asm-generic/vmlinux.lds.h | 6 +++++-
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index c8af90ff49f0..afff03e9be39 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -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_MAIN .text.fixup .text.unlikely .fixup __ftr_alt_* .ref.text);
 		SCHED_TEXT
 		CPUIDLE_TEXT
 		LOCK_TEXT
@@ -274,7 +274,7 @@ SECTIONS
 	.data : AT(ADDR(.data) - LOAD_OFFSET) {
 		DATA_DATA
 		*(.data.rel*)
-		*(.sdata)
+		*(SDATA_MAIN)
 		*(.sdata2)
 		*(.got.plt) *(.got)
 		*(.plt)
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 278841c75b97..5549be081931 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -68,11 +68,15 @@
 #ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
 #define TEXT_MAIN .text .text.[0-9a-zA-Z_]*
 #define DATA_MAIN .data .data.[0-9a-zA-Z_]*
+#define SDATA_MAIN .sdata .sdata.[0-9a-zA-Z_]*
 #define BSS_MAIN .bss .bss.[0-9a-zA-Z_]*
+#define SBSS_MAIN .sbss .sbss.[0-9a-zA-Z_]*
 #else
 #define TEXT_MAIN .text
 #define DATA_MAIN .data
+#define SDATA_MAIN .sdata
 #define BSS_MAIN .bss
+#define SBSS_MAIN .sbss
 #endif
 
 /*
@@ -629,7 +633,7 @@
 	. = ALIGN(sbss_align);						\
 	.sbss : AT(ADDR(.sbss) - LOAD_OFFSET) {				\
 		*(.dynsbss)						\
-		*(.sbss)						\
+		*(SBSS_MAIN)						\
 		*(.scommon)						\
 	}
 
-- 
2.13.3

[PATCH v2 2/2] powerpc: Allow selection of CONFIG_LD_DEAD_CODE_DATA_ELIMINATION

[Christophe Leroy]

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