target/linux/generic/hack-4.14/220-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 @@ -272,6 +272,11 @@ else
  25  scripts/Kbuild.include: ;
  26  include scripts/Kbuild.include
  27
  28 +ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
  29 +KBUILD_CFLAGS_KERNEL   += $(call cc-option,-ffunction-sections,)
  30 +KBUILD_CFLAGS_KERNEL   += $(call cc-option,-fdata-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 @@ -779,11 +784,6 @@ 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  += $(call cc-option,-ffunction-sections,)
  42 -KBUILD_CFLAGS  += $(call cc-option,-fdata-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  CHECKFLAGS     += $(NOSTDINC_FLAGS)
  48 --- a/arch/arm/Kconfig
  49 +++ b/arch/arm/Kconfig
  50 @@ -91,6 +91,7 @@ config ARM
  51         select HAVE_UID16
  52         select HAVE_VIRT_CPU_ACCOUNTING_GEN
  53         select IRQ_FORCED_THREADING
  54 +       select LD_DEAD_CODE_DATA_ELIMINATION
  55         select MODULES_USE_ELF_REL
  56         select NO_BOOTMEM
  57         select OF_EARLY_FLATTREE if OF
  58 --- a/arch/arm/boot/compressed/Makefile
  59 +++ b/arch/arm/boot/compressed/Makefile
  60 @@ -103,6 +103,7 @@ ifeq ($(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 @@ -18,7 +18,7 @@
  71  #define PROC_INFO                                                      \
  72         . = ALIGN(4);                                                   \
  73         VMLINUX_SYMBOL(__proc_info_begin) = .;                          \
  74 -       *(.proc.info.init)                                              \
  75 +       KEEP(*(.proc.info.init))                                        \
  76         VMLINUX_SYMBOL(__proc_info_end) = .;
  77
  78  #define HYPERVISOR_TEXT                                                        \
  79 @@ -29,11 +29,11 @@
  80  #define IDMAP_TEXT                                                     \
  81         ALIGN_FUNCTION();                                               \
  82         VMLINUX_SYMBOL(__idmap_text_start) = .;                         \
  83 -       *(.idmap.text)                                                  \
  84 +       KEEP(*(.idmap.text))                                            \
  85         VMLINUX_SYMBOL(__idmap_text_end) = .;                           \
  86         . = ALIGN(PAGE_SIZE);                                           \
  87         VMLINUX_SYMBOL(__hyp_idmap_text_start) = .;                     \
  88 -       *(.hyp.idmap.text)                                              \
  89 +       KEEP(*(.hyp.idmap.text))                                        \
  90         VMLINUX_SYMBOL(__hyp_idmap_text_end) = .;
  91
  92  #ifdef CONFIG_HOTPLUG_CPU
  93 @@ -106,7 +106,7 @@ SECTIONS
  94                 _stext = .;             /* Text and read-only data      */
  95                         IDMAP_TEXT
  96                         __exception_text_start = .;
  97 -                       *(.exception.text)
  98 +                       KEEP(*(.exception.text))
  99                         __exception_text_end = .;
 100                         IRQENTRY_TEXT
 101                         SOFTIRQENTRY_TEXT
 102 @@ -135,7 +135,7 @@ SECTIONS
 103         __ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) {
 104                 __start___ex_table = .;
 105  #ifdef CONFIG_MMU
 106 -               *(__ex_table)
 107 +               KEEP(*(__ex_table))
 108  #endif
 109                 __stop___ex_table = .;
 110         }
 111 @@ -147,12 +147,12 @@ SECTIONS
 112         . = ALIGN(8);
 113         .ARM.unwind_idx : {
 114                 __start_unwind_idx = .;
 115 -               *(.ARM.exidx*)
 116 +               KEEP(*(.ARM.exidx*))
 117                 __stop_unwind_idx = .;
 118         }
 119         .ARM.unwind_tab : {
 120                 __start_unwind_tab = .;
 121 -               *(.ARM.extab*)
 122 +               KEEP(*(.ARM.extab*))
 123                 __stop_unwind_tab = .;
 124         }
 125  #endif
 126 @@ -172,14 +172,14 @@ SECTIONS
 127          */
 128         __vectors_start = .;
 129         .vectors 0xffff0000 : AT(__vectors_start) {
 130 -               *(.vectors)
 131 +               KEEP(*(.vectors))
 132         }
 133         . = __vectors_start + SIZEOF(.vectors);
 134         __vectors_end = .;
 135
 136         __stubs_start = .;
 137         .stubs ADDR(.vectors) + 0x1000 : AT(__stubs_start) {
 138 -               *(.stubs)
 139 +               KEEP(*(.stubs))
 140         }
 141         . = __stubs_start + SIZEOF(.stubs);
 142         __stubs_end = .;
 143 @@ -195,24 +195,24 @@ SECTIONS
 144         }
 145         .init.arch.info : {
 146                 __arch_info_begin = .;
 147 -               *(.arch.info.init)
 148 +               KEEP(*(.arch.info.init))
 149                 __arch_info_end = .;
 150         }
 151         .init.tagtable : {
 152                 __tagtable_begin = .;
 153 -               *(.taglist.init)
 154 +               KEEP(*(.taglist.init))
 155                 __tagtable_end = .;
 156         }
 157  #ifdef CONFIG_SMP_ON_UP
 158         .init.smpalt : {
 159                 __smpalt_begin = .;
 160 -               *(.alt.smp.init)
 161 +               KEEP(*(.alt.smp.init))
 162                 __smpalt_end = .;
 163         }
 164  #endif
 165         .init.pv_table : {
 166                 __pv_table_begin = .;
 167 -               *(.pv_table)
 168 +               KEEP(*(.pv_table))
 169                 __pv_table_end = .;
 170         }
 171         .init.data : {
 172 --- a/arch/mips/Kconfig
 173 +++ b/arch/mips/Kconfig
 174 @@ -40,6 +40,7 @@ config MIPS
 175         select HAVE_CBPF_JIT if (!64BIT && !CPU_MICROMIPS)
 176         select HAVE_EBPF_JIT if (64BIT && !CPU_MICROMIPS)
 177         select HAVE_CC_STACKPROTECTOR
 178 +       select LD_DEAD_CODE_DATA_ELIMINATION
 179         select HAVE_CONTEXT_TRACKING
 180         select HAVE_COPY_THREAD_TLS
 181         select HAVE_C_RECORDMCOUNT
 182 --- a/arch/mips/kernel/vmlinux.lds.S
 183 +++ b/arch/mips/kernel/vmlinux.lds.S
 184 @@ -72,7 +72,7 @@ SECTIONS
 185         /* Exception table for data bus errors */
 186         __dbe_table : {
 187                 __start___dbe_table = .;
 188 -               *(__dbe_table)
 189 +               KEEP(*(__dbe_table))
 190                 __stop___dbe_table = .;
 191         }
 192
 193 @@ -123,7 +123,7 @@ SECTIONS
 194         . = ALIGN(4);
 195         .mips.machines.init : AT(ADDR(.mips.machines.init) - LOAD_OFFSET) {
 196                 __mips_machines_start = .;
 197 -               *(.mips.machines.init)
 198 +               KEEP(*(.mips.machines.init))
 199                 __mips_machines_end = .;
 200         }
 201
 202 --- a/include/asm-generic/vmlinux.lds.h
 203 +++ b/include/asm-generic/vmlinux.lds.h
 204 @@ -105,7 +105,7 @@
 205  #ifdef CONFIG_FTRACE_MCOUNT_RECORD
 206  #define MCOUNT_REC()   . = ALIGN(8);                           \
 207                         VMLINUX_SYMBOL(__start_mcount_loc) = .; \
 208 -                       *(__mcount_loc)                         \
 209 +                       KEEP(*(__mcount_loc))                   \
 210                         VMLINUX_SYMBOL(__stop_mcount_loc) = .;
 211  #else
 212  #define MCOUNT_REC()
 213 @@ -113,7 +113,7 @@
 214
 215  #ifdef CONFIG_TRACE_BRANCH_PROFILING
 216  #define LIKELY_PROFILE()       VMLINUX_SYMBOL(__start_annotated_branch_profile) = .; \
 217 -                               *(_ftrace_annotated_branch)                           \
 218 +                               KEEP(*(_ftrace_annotated_branch))                     \
 219                                 VMLINUX_SYMBOL(__stop_annotated_branch_profile) = .;
 220  #else
 221  #define LIKELY_PROFILE()
 222 @@ -121,7 +121,7 @@
 223
 224  #ifdef CONFIG_PROFILE_ALL_BRANCHES
 225  #define BRANCH_PROFILE()       VMLINUX_SYMBOL(__start_branch_profile) = .;   \
 226 -                               *(_ftrace_branch)                             \
 227 +                               KEEP(*(_ftrace_branch))                       \
 228                                 VMLINUX_SYMBOL(__stop_branch_profile) = .;
 229  #else
 230  #define BRANCH_PROFILE()
 231 @@ -237,7 +237,8 @@
 232         LIKELY_PROFILE()                                                \
 233         BRANCH_PROFILE()                                                \
 234         TRACE_PRINTKS()                                                 \
 235 -       TRACEPOINT_STR()
 236 +       TRACEPOINT_STR()                                                \
 237 +       *(.data.[a-zA-Z_]*)
 238
 239  /*
 240   * Data section helpers
 241 @@ -497,7 +498,7 @@
 242  #define ENTRY_TEXT                                                     \
 243                 ALIGN_FUNCTION();                                       \
 244                 VMLINUX_SYMBOL(__entry_text_start) = .;                 \
 245 -               *(.entry.text)                                          \
 246 +               KEEP(*(.entry.text))                                    \
 247                 VMLINUX_SYMBOL(__entry_text_end) = .;
 248
 249  #define IRQENTRY_TEXT                                                  \
 250 @@ -604,7 +605,7 @@
 251         . = ALIGN(sbss_align);                                          \
 252         .sbss : AT(ADDR(.sbss) - LOAD_OFFSET) {                         \
 253                 *(.dynsbss)                                             \
 254 -               *(.sbss)                                                \
 255 +               *(.sbss .sbss.*)                                        \
 256                 *(.scommon)                                             \
 257         }
 258