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 @@ -22,13 +22,13 @@
  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  #define PROC_INFO                                                      \
  84                 . = ALIGN(4);                                           \
  85                 __proc_info_begin = .;                                  \
  86 -               *(.proc.info.init)                                      \
  87 +               KEEP(*(.proc.info.init))                                \
  88                 __proc_info_end = .;
  89
  90  #define HYPERVISOR_TEXT                                                        \
  91 @@ -39,11 +39,11 @@
  92  #define IDMAP_TEXT                                                     \
  93                 ALIGN_FUNCTION();                                       \
  94                 __idmap_text_start = .;                                 \
  95 -               *(.idmap.text)                                          \
  96 +               KEEP(*(.idmap.text))                                    \
  97                 __idmap_text_end = .;                                   \
  98                 . = ALIGN(PAGE_SIZE);                                   \
  99                 __hyp_idmap_text_start = .;                             \
 100 -               *(.hyp.idmap.text)                                      \
 101 +               KEEP(*(.hyp.idmap.text))                                \
 102                 __hyp_idmap_text_end = .;
 103
 104  #define ARM_DISCARD                                                    \
 105 @@ -86,12 +86,12 @@
 106         . = ALIGN(8);                                                   \
 107         .ARM.unwind_idx : {                                             \
 108                 __start_unwind_idx = .;                                 \
 109 -               *(.ARM.exidx*)                                          \
 110 +               KEEP(*(.ARM.exidx*))                                    \
 111                 __stop_unwind_idx = .;                                  \
 112         }                                                               \
 113         .ARM.unwind_tab : {                                             \
 114                 __start_unwind_tab = .;                                 \
 115 -               *(.ARM.extab*)                                          \
 116 +               KEEP(*(.ARM.extab*))                                    \
 117                 __stop_unwind_tab = .;                                  \
 118         }
 119
 120 @@ -102,14 +102,14 @@
 121  #define ARM_VECTORS                                                    \
 122         __vectors_start = .;                                            \
 123         .vectors 0xffff0000 : AT(__vectors_start) {                     \
 124 -               *(.vectors)                                             \
 125 +               KEEP(*(.vectors))                                       \
 126         }                                                               \
 127         . = __vectors_start + SIZEOF(.vectors);                         \
 128         __vectors_end = .;                                              \
 129                                                                         \
 130         __stubs_start = .;                                              \
 131         .stubs ADDR(.vectors) + 0x1000 : AT(__stubs_start) {            \
 132 -               *(.stubs)                                               \
 133 +               KEEP(*(.stubs))                                         \
 134         }                                                               \
 135         . = __stubs_start + SIZEOF(.stubs);                             \
 136         __stubs_end = .;                                                \