target/linux/generic/hack-4.19/220-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/Makefile
  23 +++ b/Makefile
  24 @@ -294,6 +294,11 @@ else
  25  scripts/Kbuild.include: ;
  26  include scripts/Kbuild.include
  27
  28 +ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
  29 +KBUILD_CFLAGS_KERNEL += -ffunction-sections -fdata-sections
  30 +LDFLAGS_vmlinux += --gc-sections
  31 +endif
  32 +
  33  # Read KERNELRELEASE from include/config/kernel.release (if it exists)
  34  KERNELRELEASE = $(shell cat include/config/kernel.release 2> /dev/null)
  35  KERNELVERSION = $(VERSION)$(if $(PATCHLEVEL),.$(PATCHLEVEL)$(if $(SUBLEVEL),.$(SUBLEVEL)))$(EXTRAVERSION)
  36 @@ -785,11 +790,6 @@ ifdef CONFIG_DEBUG_SECTION_MISMATCH
  37  KBUILD_CFLAGS += $(call cc-option, -fno-inline-functions-called-once)
  38  endif
  39
  40 -ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
  41 -KBUILD_CFLAGS_KERNEL += -ffunction-sections -fdata-sections
  42 -LDFLAGS_vmlinux += --gc-sections
  43 -endif
  44 -
  45  # arch Makefile may override CC so keep this after arch Makefile is included
  46  NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include)
  47
  48 --- a/arch/arm/Kconfig
  49 +++ b/arch/arm/Kconfig
  50 @@ -98,6 +98,7 @@ config ARM
  51         select HAVE_UID16
  52         select HAVE_VIRT_CPU_ACCOUNTING_GEN
  53         select IRQ_FORCED_THREADING
  54 +       select HAVE_LD_DEAD_CODE_DATA_ELIMINATION
  55         select MODULES_USE_ELF_REL
  56         select NEED_DMA_MAP_STATE
  57         select NO_BOOTMEM
  58 --- a/arch/arm/boot/compressed/Makefile
  59 +++ b/arch/arm/boot/compressed/Makefile
  60 @@ -106,6 +106,7 @@ ifeq ($(CONFIG_FUNCTION_TRACER),y)
  61  ORIG_CFLAGS := $(KBUILD_CFLAGS)
  62  KBUILD_CFLAGS = $(subst -pg, , $(ORIG_CFLAGS))
  63  endif
  64 +KBUILD_CFLAGS_KERNEL := $(patsubst -f%-sections,,$(KBUILD_CFLAGS_KERNEL))
  65
  66  # -fstack-protector-strong triggers protection checks in this code,
  67  # but it is being used too early to link to meaningful stack_chk logic.
  68 --- a/arch/arm/kernel/vmlinux.lds.S
  69 +++ b/arch/arm/kernel/vmlinux.lds.S
  70 @@ -100,24 +100,24 @@ SECTIONS
  71         }
  72         .init.arch.info : {
  73                 __arch_info_begin = .;
  74 -               *(.arch.info.init)
  75 +               KEEP(*(.arch.info.init))
  76                 __arch_info_end = .;
  77         }
  78         .init.tagtable : {
  79                 __tagtable_begin = .;
  80 -               *(.taglist.init)
  81 +               KEEP(*(.taglist.init))
  82                 __tagtable_end = .;
  83         }
  84  #ifdef CONFIG_SMP_ON_UP
  85         .init.smpalt : {
  86                 __smpalt_begin = .;
  87 -               *(.alt.smp.init)
  88 +               KEEP(*(.alt.smp.init))
  89                 __smpalt_end = .;
  90         }
  91  #endif
  92         .init.pv_table : {
  93                 __pv_table_begin = .;
  94 -               *(.pv_table)
  95 +               KEEP(*(.pv_table))
  96                 __pv_table_end = .;
  97         }
  98
  99 --- a/arch/arm/kernel/vmlinux.lds.h
 100 +++ b/arch/arm/kernel/vmlinux.lds.h
 101 @@ -22,13 +22,13 @@
 102  #define ARM_MMU_DISCARD(x)
 103  #else
 104  #define ARM_MMU_KEEP(x)
 105 -#define ARM_MMU_DISCARD(x)     x
 106 +#define ARM_MMU_DISCARD(x)     KEEP(x)
 107  #endif
 108
 109  #define PROC_INFO                                                      \
 110                 . = ALIGN(4);                                           \
 111                 __proc_info_begin = .;                                  \
 112 -               *(.proc.info.init)                                      \
 113 +               KEEP(*(.proc.info.init))                                \
 114                 __proc_info_end = .;
 115
 116  #define HYPERVISOR_TEXT                                                        \
 117 @@ -39,11 +39,11 @@
 118  #define IDMAP_TEXT                                                     \
 119                 ALIGN_FUNCTION();                                       \
 120                 __idmap_text_start = .;                                 \
 121 -               *(.idmap.text)                                          \
 122 +               KEEP(*(.idmap.text))                                    \
 123                 __idmap_text_end = .;                                   \
 124                 . = ALIGN(PAGE_SIZE);                                   \
 125                 __hyp_idmap_text_start = .;                             \
 126 -               *(.hyp.idmap.text)                                      \
 127 +               KEEP(*(.hyp.idmap.text))                                \
 128                 __hyp_idmap_text_end = .;
 129
 130  #define ARM_DISCARD                                                    \
 131 @@ -86,12 +86,12 @@
 132         . = ALIGN(8);                                                   \
 133         .ARM.unwind_idx : {                                             \
 134                 __start_unwind_idx = .;                                 \
 135 -               *(.ARM.exidx*)                                          \
 136 +               KEEP(*(.ARM.exidx*))                                    \
 137                 __stop_unwind_idx = .;                                  \
 138         }                                                               \
 139         .ARM.unwind_tab : {                                             \
 140                 __start_unwind_tab = .;                                 \
 141 -               *(.ARM.extab*)                                          \
 142 +               KEEP(*(.ARM.extab*))                                    \
 143                 __stop_unwind_tab = .;                                  \
 144         }
 145
 146 @@ -102,14 +102,14 @@
 147  #define ARM_VECTORS                                                    \
 148         __vectors_start = .;                                            \
 149         .vectors 0xffff0000 : AT(__vectors_start) {                     \
 150 -               *(.vectors)                                             \
 151 +               KEEP(*(.vectors))                                       \
 152         }                                                               \
 153         . = __vectors_start + SIZEOF(.vectors);                         \
 154         __vectors_end = .;                                              \
 155                                                                         \
 156         __stubs_start = .;                                              \
 157         .stubs ADDR(.vectors) + 0x1000 : AT(__stubs_start) {            \
 158 -               *(.stubs)                                               \
 159 +               KEEP(*(.stubs))                                         \
 160         }                                                               \
 161         . = __stubs_start + SIZEOF(.stubs);                             \
 162         __stubs_end = .;                                                \
 163 --- a/arch/mips/Kconfig
 164 +++ b/arch/mips/Kconfig
 165 @@ -43,6 +43,7 @@ config MIPS
 166         select HAVE_ARCH_TRANSPARENT_HUGEPAGE if CPU_SUPPORTS_HUGEPAGES && 64BIT
 167         select HAVE_CBPF_JIT if (!64BIT && !CPU_MICROMIPS)
 168         select HAVE_EBPF_JIT if (64BIT && !CPU_MICROMIPS)
 169 +       select HAVE_LD_DEAD_CODE_DATA_ELIMINATION
 170         select HAVE_CONTEXT_TRACKING
 171         select HAVE_COPY_THREAD_TLS
 172         select HAVE_C_RECORDMCOUNT
 173 --- a/arch/mips/kernel/vmlinux.lds.S
 174 +++ b/arch/mips/kernel/vmlinux.lds.S
 175 @@ -72,7 +72,7 @@ SECTIONS
 176         /* Exception table for data bus errors */
 177         __dbe_table : {
 178                 __start___dbe_table = .;
 179 -               *(__dbe_table)
 180 +               KEEP(*(__dbe_table))
 181                 __stop___dbe_table = .;
 182         }
 183
 184 @@ -123,7 +123,7 @@ SECTIONS
 185         . = ALIGN(4);
 186         .mips.machines.init : AT(ADDR(.mips.machines.init) - LOAD_OFFSET) {
 187                 __mips_machines_start = .;
 188 -               *(.mips.machines.init)
 189 +               KEEP(*(.mips.machines.init))
 190                 __mips_machines_end = .;
 191         }
 192