target/linux/generic/hack-5.4/220-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 @@ -100,24 +100,24 @@ SECTIONS
  45         }
  46         .init.arch.info : {
  47                 __arch_info_begin = .;
  48 -               *(.arch.info.init)
  49 +               KEEP(*(.arch.info.init))
  50                 __arch_info_end = .;
  51         }
  52         .init.tagtable : {
  53                 __tagtable_begin = .;
  54 -               *(.taglist.init)
  55 +               KEEP(*(.taglist.init))
  56                 __tagtable_end = .;
  57         }
  58  #ifdef CONFIG_SMP_ON_UP
  59         .init.smpalt : {
  60                 __smpalt_begin = .;
  61 -               *(.alt.smp.init)
  62 +               KEEP(*(.alt.smp.init))
  63                 __smpalt_end = .;
  64         }
  65  #endif
  66         .init.pv_table : {
  67                 __pv_table_begin = .;
  68 -               *(.pv_table)
  69 +               KEEP(*(.pv_table))
  70                 __pv_table_end = .;
  71         }
  72
  73 --- a/arch/arm/kernel/vmlinux.lds.h
  74 +++ b/arch/arm/kernel/vmlinux.lds.h
  75 @@ -22,7 +22,7 @@
  76  #define ARM_MMU_DISCARD(x)
  77  #else
  78  #define ARM_MMU_KEEP(x)
  79 -#define ARM_MMU_DISCARD(x)     x
  80 +#define ARM_MMU_DISCARD(x)     KEEP(x)
  81  #endif
  82
  83  /*
  84 @@ -41,7 +41,7 @@
  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 @@ -52,11 +52,11 @@
  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 @@ -99,12 +99,12 @@
 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 @@ -116,7 +116,7 @@
 123         __vectors_lma = .;                                              \
 124         OVERLAY 0xffff0000 : NOCROSSREFS AT(__vectors_lma) {            \
 125                 .vectors {                                              \
 126 -                       *(.vectors)                                     \
 127 +                       KEEP(*(.vectors))                               \
 128                 }                                                       \
 129                 .vectors.bhb.loop8 {                                    \
 130                         *(.vectors.bhb.loop8)                           \
 131 @@ -134,7 +134,7 @@
 132                                                                         \
 133         __stubs_lma = .;                                                \
 134         .stubs ADDR(.vectors) + 0x1000 : AT(__stubs_lma) {              \
 135 -               *(.stubs)                                               \
 136 +               KEEP(*(.stubs))                                         \
 137         }                                                               \
 138         ARM_LMA(__stubs, .stubs);                                       \
 139         . = __stubs_lma + SIZEOF(.stubs);                               \