Commit 4c1d9bb0 authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Masahiro Yamada
Browse files

powerpc: Allow LD_DEAD_CODE_DATA_ELIMINATION to be selected 



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, the resulting
kernel is almost 400kB smaller (and still boots):

    text      data       bss        dec   filename
11827621   4810490   1341080   17979191   vmlinux
11752437   4598858   1338776   17690071   vmlinux.dcde

Mathieu's numbers for custom Mac Mini G4 config has almost 200kB
saving. It also had some increase in vmlinux size for as-yet
unknown reasons.

    text      data       bss        dec   filename
 7461457   2475122   1428064   11364643   vmlinux
 7386425   2364370   1425432   11176227   vmlinux.dcde

Tested-by: Christophe Leroy <christophe.leroy@c-s.fr> [8xx]
Tested-by: Mathieu Malaterre <malat@debian.org> [32-bit powermac]
Signed-off-by: default avatarNicholas Piggin <npiggin@gmail.com>
Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
parent 5d20ee31

arch/powerpc/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -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

arch/powerpc/kernel/vmlinux.lds.S

+11 −11
Original line number Diff line number Diff line
@@ -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_MAIN .text.fixup .text.unlikely .fixup __ftr_alt_* .ref.text);

		SCHED_TEXT

		CPUIDLE_TEXT

		LOCK_TEXT
@@ -170,10 +170,10 @@ SECTIONS 
	.init.data : AT(ADDR(.init.data) - LOAD_OFFSET) {

		INIT_DATA

		__vtop_table_begin = .;

		*(.vtop_fixup);

		KEEP(*(.vtop_fixup));

		__vtop_table_end = .;

		__ptov_table_begin = .;

		*(.ptov_fixup);

		KEEP(*(.ptov_fixup));

		__ptov_table_end = .;

	}
@@ -194,26 +194,26 @@ SECTIONS 
	. = ALIGN(8);

	__ftr_fixup : AT(ADDR(__ftr_fixup) - LOAD_OFFSET) {

		__start___ftr_fixup = .;

		*(__ftr_fixup)

		KEEP(*(__ftr_fixup))

		__stop___ftr_fixup = .;

	}

	. = ALIGN(8);

	__mmu_ftr_fixup : AT(ADDR(__mmu_ftr_fixup) - LOAD_OFFSET) {

		__start___mmu_ftr_fixup = .;

		*(__mmu_ftr_fixup)

		KEEP(*(__mmu_ftr_fixup))

		__stop___mmu_ftr_fixup = .;

	}

	. = ALIGN(8);

	__lwsync_fixup : AT(ADDR(__lwsync_fixup) - LOAD_OFFSET) {

		__start___lwsync_fixup = .;

		*(__lwsync_fixup)

		KEEP(*(__lwsync_fixup))

		__stop___lwsync_fixup = .;

	}

#ifdef CONFIG_PPC64

	. = ALIGN(8);

	__fw_ftr_fixup : AT(ADDR(__fw_ftr_fixup) - LOAD_OFFSET) {

		__start___fw_ftr_fixup = .;

		*(__fw_ftr_fixup)

		KEEP(*(__fw_ftr_fixup))

		__stop___fw_ftr_fixup = .;

	}

#endif
@@ -226,7 +226,7 @@ SECTIONS 
	. = ALIGN(8);

	.machine.desc : AT(ADDR(.machine.desc) - LOAD_OFFSET) {

		__machine_desc_start = . ;

		*(.machine.desc)

		KEEP(*(.machine.desc))

		__machine_desc_end = . ;

	}

#ifdef CONFIG_RELOCATABLE
@@ -274,7 +274,7 @@ SECTIONS 
	.data : AT(ADDR(.data) - LOAD_OFFSET) {

		DATA_DATA

		*(.data.rel*)

		*(.sdata)

		*(SDATA_MAIN)

		*(.sdata2)

		*(.got.plt) *(.got)

		*(.plt)
@@ -289,7 +289,7 @@ SECTIONS 


	.opd : AT(ADDR(.opd) - LOAD_OFFSET) {

		__start_opd = .;

		*(.opd)

		KEEP(*(.opd))

		__end_opd = .;

	}

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