target/linux/generic/hack-5.4/220-arm-gc_sections.patch

   1 From e3d8676f5722b7622685581e06e8f53e6138e3ab Mon Sep 17 00:00:00 2001
   2 From: Felix Fietkau <nbd@nbd.name>
   3 Date: Sat, 15 Jul 2017 23:42:36 +0200
   4 Subject: use -ffunction-sections, -fdata-sections and --gc-sections
   5
   6 In combination with kernel symbol export stripping this significantly reduces
   7 the kernel image size. Used on both ARM and MIPS architectures.
   8
   9 Signed-off-by: Felix Fietkau <nbd@nbd.name>
  10 Signed-off-by: Jonas Gorski <jogo@openwrt.org>
  11 Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
  12 ---
  13  Makefile                          | 10 +++----
  14  arch/arm/Kconfig                  |  1 +
  15  arch/arm/boot/compressed/Makefile |  1 +
  16  arch/arm/kernel/vmlinux.lds.S     | 26 ++++++++--------
  17  arch/mips/Kconfig                 |  1 +
  18  arch/mips/kernel/vmlinux.lds.S    |  4 +--
  19  include/asm-generic/vmlinux.lds.h | 63 ++++++++++++++++++++-------------------
  20  7 files changed, 55 insertions(+), 51 deletions(-)
  21
  22 --- a/arch/arm/Kconfig
  23 +++ b/arch/arm/Kconfig
  24 @@ -112,6 +112,7 @@ config ARM
  25         select HAVE_UID16
  26         select HAVE_VIRT_CPU_ACCOUNTING_GEN
  27         select IRQ_FORCED_THREADING
  28 +       select HAVE_LD_DEAD_CODE_DATA_ELIMINATION
  29         select MODULES_USE_ELF_REL
  30         select NEED_DMA_MAP_STATE
  31         select OF_EARLY_FLATTREE if OF
  32 --- a/arch/arm/boot/compressed/Makefile
  33 +++ b/arch/arm/boot/compressed/Makefile
  34 @@ -108,6 +108,7 @@ ifeq ($(CONFIG_FUNCTION_TRACER),y)
  35  ORIG_CFLAGS := $(KBUILD_CFLAGS)
  36  KBUILD_CFLAGS = $(subst -pg, , $(ORIG_CFLAGS))
  37  endif
  38 +KBUILD_CFLAGS_KERNEL := $(patsubst -f%-sections,,$(KBUILD_CFLAGS_KERNEL))
  39
  40  # -fstack-protector-strong triggers protection checks in this code,
  41  # but it is being used too early to link to meaningful stack_chk logic.
  42 --- a/arch/arm/kernel/vmlinux.lds.S
  43 +++ b/arch/arm/kernel/vmlinux.lds.S
  44 @@ -73,7 +73,7 @@ SECTIONS
  45         . = ALIGN(4);
  46         __ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) {
  47                 __start___ex_table = .;
  48 -               ARM_MMU_KEEP(*(__ex_table))
  49 +               KEEP(*(__ex_table))
  50                 __stop___ex_table = .;
  51         }
  52
  53 @@ -100,24 +100,24 @@ SECTIONS
  54         }
  55         .init.arch.info : {
  56                 __arch_info_begin = .;
  57 -               *(.arch.info.init)
  58 +               KEEP(*(.arch.info.init))
  59                 __arch_info_end = .;
  60         }
  61         .init.tagtable : {
  62                 __tagtable_begin = .;
  63 -               *(.taglist.init)
  64 +               KEEP(*(.taglist.init))
  65                 __tagtable_end = .;
  66         }
  67  #ifdef CONFIG_SMP_ON_UP
  68         .init.smpalt : {
  69                 __smpalt_begin = .;
  70 -               *(.alt.smp.init)
  71 +               KEEP(*(.alt.smp.init))
  72                 __smpalt_end = .;
  73         }
  74  #endif
  75         .init.pv_table : {
  76                 __pv_table_begin = .;
  77 -               *(.pv_table)
  78 +               KEEP(*(.pv_table))
  79                 __pv_table_end = .;
  80         }
  81
  82 --- a/arch/arm/kernel/vmlinux.lds.h
  83 +++ b/arch/arm/kernel/vmlinux.lds.h
  84 @@ -28,7 +28,7 @@
  85  #define PROC_INFO                                                      \
  86                 . = ALIGN(4);                                           \
  87                 __proc_info_begin = .;                                  \
  88 -               *(.proc.info.init)                                      \
  89 +               KEEP(*(.proc.info.init))                                \
  90                 __proc_info_end = .;
  91
  92  #define HYPERVISOR_TEXT                                                        \
  93 @@ -39,11 +39,11 @@
  94  #define IDMAP_TEXT                                                     \
  95                 ALIGN_FUNCTION();                                       \
  96                 __idmap_text_start = .;                                 \
  97 -               *(.idmap.text)                                          \
  98 +               KEEP(*(.idmap.text))                                    \
  99                 __idmap_text_end = .;                                   \
 100                 . = ALIGN(PAGE_SIZE);                                   \
 101                 __hyp_idmap_text_start = .;                             \
 102 -               *(.hyp.idmap.text)                                      \
 103 +               KEEP(*(.hyp.idmap.text))                                \
 104                 __hyp_idmap_text_end = .;
 105
 106  #define ARM_DISCARD                                                    \
 107 @@ -86,12 +86,12 @@
 108         . = ALIGN(8);                                                   \
 109         .ARM.unwind_idx : {                                             \
 110                 __start_unwind_idx = .;                                 \
 111 -               *(.ARM.exidx*)                                          \
 112 +               KEEP(*(.ARM.exidx*))                                    \
 113                 __stop_unwind_idx = .;                                  \
 114         }                                                               \
 115         .ARM.unwind_tab : {                                             \
 116                 __start_unwind_tab = .;                                 \
 117 -               *(.ARM.extab*)                                          \
 118 +               KEEP(*(.ARM.extab*))                                    \
 119                 __stop_unwind_tab = .;                                  \
 120         }
 121
 122 @@ -102,14 +102,14 @@
 123  #define ARM_VECTORS                                                    \
 124         __vectors_start = .;                                            \
 125         .vectors 0xffff0000 : AT(__vectors_start) {                     \
 126 -               *(.vectors)                                             \
 127 +               KEEP(*(.vectors))                                       \
 128         }                                                               \
 129         . = __vectors_start + SIZEOF(.vectors);                         \
 130         __vectors_end = .;                                              \
 131                                                                         \
 132         __stubs_start = .;                                              \
 133         .stubs ADDR(.vectors) + 0x1000 : AT(__stubs_start) {            \
 134 -               *(.stubs)                                               \
 135 +               KEEP(*(.stubs))                                         \
 136         }                                                               \
 137         . = __stubs_start + SIZEOF(.stubs);                             \
 138         __stubs_end = .;                                                \