target/linux/generic/hack-4.9/220-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 @@ -406,6 +406,11 @@ KBUILD_CFLAGS_MODULE  := -DMODULE
  25  KBUILD_LDFLAGS_MODULE = -T $(srctree)/scripts/module-common.lds $(if $(CONFIG_PROFILING),,-s)
  26  GCC_PLUGINS_CFLAGS :=
  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 @@ -673,11 +678,6 @@ KBUILD_CFLAGS      += $(call cc-disable-warni
  37  KBUILD_CFLAGS  += $(call cc-disable-warning, int-in-bool-context)
  38  KBUILD_CFLAGS  += $(call cc-disable-warning, attribute-alias)
  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  ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
  46  KBUILD_CFLAGS  += $(call cc-option,-Oz,-Os)
  47  KBUILD_CFLAGS  += $(call cc-disable-warning,maybe-uninitialized,) $(EXTRA_OPTIMIZATION)
  48 --- a/arch/arm/Kconfig
  49 +++ b/arch/arm/Kconfig
  50 @@ -81,6 +81,7 @@ config ARM
  51         select HAVE_UID16
  52         select HAVE_VIRT_CPU_ACCOUNTING_GEN
  53         select IRQ_FORCED_THREADING
  54 +       select LD_DEAD_CODE_DATA_ELIMINATION
  55         select MODULES_USE_ELF_REL
  56         select NO_BOOTMEM
  57         select OF_EARLY_FLATTREE if OF
  58 --- a/arch/arm/boot/compressed/Makefile
  59 +++ b/arch/arm/boot/compressed/Makefile
  60 @@ -102,6 +102,7 @@ ifeq ($(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 @@ -17,7 +17,7 @@
  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 @@ -28,11 +28,11 @@
  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 @@ -105,7 +105,7 @@ 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 @@ -134,7 +134,7 @@ 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 @@ -146,12 +146,12 @@ 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 @@ -171,14 +171,14 @@ 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 @@ -194,24 +194,24 @@ 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 @@ -55,6 +55,7 @@ config MIPS
 175         select CLONE_BACKWARDS
 176         select HAVE_DEBUG_STACKOVERFLOW
 177         select HAVE_CC_STACKPROTECTOR
 178 +       select LD_DEAD_CODE_DATA_ELIMINATION
 179         select CPU_PM if CPU_IDLE
 180         select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
 181         select ARCH_BINFMT_ELF_STATE
 182 --- a/arch/mips/kernel/vmlinux.lds.S
 183 +++ b/arch/mips/kernel/vmlinux.lds.S
 184 @@ -71,7 +71,7 @@ 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 @@ -121,7 +121,7 @@ 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 @@ -130,7 +130,7 @@
 232  #ifdef CONFIG_KPROBES
 233  #define KPROBE_BLACKLIST()     . = ALIGN(8);                                 \
 234                                 VMLINUX_SYMBOL(__start_kprobe_blacklist) = .; \
 235 -                               *(_kprobe_blacklist)                          \
 236 +                               KEEP(*(_kprobe_blacklist))                    \
 237                                 VMLINUX_SYMBOL(__stop_kprobe_blacklist) = .;
 238  #else
 239  #define KPROBE_BLACKLIST()
 240 @@ -139,10 +139,10 @@
 241  #ifdef CONFIG_EVENT_TRACING
 242  #define FTRACE_EVENTS()        . = ALIGN(8);                                   \
 243                         VMLINUX_SYMBOL(__start_ftrace_events) = .;      \
 244 -                       *(_ftrace_events)                               \
 245 +                       KEEP(*(_ftrace_events))                         \
 246                         VMLINUX_SYMBOL(__stop_ftrace_events) = .;       \
 247                         VMLINUX_SYMBOL(__start_ftrace_enum_maps) = .;   \
 248 -                       *(_ftrace_enum_map)                             \
 249 +                       KEEP(*(_ftrace_enum_map))                       \
 250                         VMLINUX_SYMBOL(__stop_ftrace_enum_maps) = .;
 251  #else
 252  #define FTRACE_EVENTS()
 253 @@ -163,7 +163,7 @@
 254  #ifdef CONFIG_FTRACE_SYSCALLS
 255  #define TRACE_SYSCALLS() . = ALIGN(8);                                 \
 256                          VMLINUX_SYMBOL(__start_syscalls_metadata) = .; \
 257 -                        *(__syscalls_metadata)                         \
 258 +                        KEEP(*(__syscalls_metadata))                   \
 259                          VMLINUX_SYMBOL(__stop_syscalls_metadata) = .;
 260  #else
 261  #define TRACE_SYSCALLS()
 262 @@ -172,7 +172,7 @@
 263  #ifdef CONFIG_SERIAL_EARLYCON
 264  #define EARLYCON_TABLE() . = ALIGN(8);                         \
 265                          VMLINUX_SYMBOL(__earlycon_table) = .;  \
 266 -                        *(__earlycon_table)                    \
 267 +                        KEEP(*(__earlycon_table))              \
 268                          VMLINUX_SYMBOL(__earlycon_table_end) = .;
 269  #else
 270  #define EARLYCON_TABLE()
 271 @@ -185,8 +185,8 @@
 272  #define _OF_TABLE_1(name)                                              \
 273         . = ALIGN(8);                                                   \
 274         VMLINUX_SYMBOL(__##name##_of_table) = .;                        \
 275 -       *(__##name##_of_table)                                          \
 276 -       *(__##name##_of_table_end)
 277 +       KEEP(*(__##name##_of_table))                                    \
 278 +       KEEP(*(__##name##_of_table_end))
 279
 280  #define CLKSRC_OF_TABLES()     OF_TABLE(CONFIG_CLKSRC_OF, clksrc)
 281  #define IRQCHIP_OF_MATCH_TABLE() OF_TABLE(CONFIG_IRQCHIP, irqchip)
 282 @@ -209,7 +209,7 @@
 283  #define KERNEL_DTB()                                                   \
 284         STRUCT_ALIGN();                                                 \
 285         VMLINUX_SYMBOL(__dtb_start) = .;                                \
 286 -       *(.dtb.init.rodata)                                             \
 287 +       KEEP(*(.dtb.init.rodata))                                       \
 288         VMLINUX_SYMBOL(__dtb_end) = .;
 289
 290  /*
 291 @@ -227,16 +227,17 @@
 292         /* implement dynamic printk debug */                            \
 293         . = ALIGN(8);                                                   \
 294         VMLINUX_SYMBOL(__start___jump_table) = .;                       \
 295 -       *(__jump_table)                                                 \
 296 +       KEEP(*(__jump_table))                                           \
 297         VMLINUX_SYMBOL(__stop___jump_table) = .;                        \
 298         . = ALIGN(8);                                                   \
 299         VMLINUX_SYMBOL(__start___verbose) = .;                          \
 300 -       *(__verbose)                                                    \
 301 +       KEEP(*(__verbose))                                              \
 302         VMLINUX_SYMBOL(__stop___verbose) = .;                           \
 303         LIKELY_PROFILE()                                                \
 304         BRANCH_PROFILE()                                                \
 305         TRACE_PRINTKS()                                                 \
 306 -       TRACEPOINT_STR()
 307 +       TRACEPOINT_STR()                                                \
 308 +       *(.data.[a-zA-Z_]*)
 309
 310  /*
 311   * Data section helpers
 312 @@ -304,35 +305,35 @@
 313         /* PCI quirks */                                                \
 314         .pci_fixup        : AT(ADDR(.pci_fixup) - LOAD_OFFSET) {        \
 315                 VMLINUX_SYMBOL(__start_pci_fixups_early) = .;           \
 316 -               *(.pci_fixup_early)                                     \
 317 +               KEEP(*(.pci_fixup_early))                               \
 318                 VMLINUX_SYMBOL(__end_pci_fixups_early) = .;             \
 319                 VMLINUX_SYMBOL(__start_pci_fixups_header) = .;          \
 320 -               *(.pci_fixup_header)                                    \
 321 +               KEEP(*(.pci_fixup_header))                              \
 322                 VMLINUX_SYMBOL(__end_pci_fixups_header) = .;            \
 323                 VMLINUX_SYMBOL(__start_pci_fixups_final) = .;           \
 324 -               *(.pci_fixup_final)                                     \
 325 +               KEEP(*(.pci_fixup_final))                               \
 326                 VMLINUX_SYMBOL(__end_pci_fixups_final) = .;             \
 327                 VMLINUX_SYMBOL(__start_pci_fixups_enable) = .;          \
 328 -               *(.pci_fixup_enable)                                    \
 329 +               KEEP(*(.pci_fixup_enable))                              \
 330                 VMLINUX_SYMBOL(__end_pci_fixups_enable) = .;            \
 331                 VMLINUX_SYMBOL(__start_pci_fixups_resume) = .;          \
 332 -               *(.pci_fixup_resume)                                    \
 333 +               KEEP(*(.pci_fixup_resume))                              \
 334                 VMLINUX_SYMBOL(__end_pci_fixups_resume) = .;            \
 335                 VMLINUX_SYMBOL(__start_pci_fixups_resume_early) = .;    \
 336 -               *(.pci_fixup_resume_early)                              \
 337 +               KEEP(*(.pci_fixup_resume_early))                        \
 338                 VMLINUX_SYMBOL(__end_pci_fixups_resume_early) = .;      \
 339                 VMLINUX_SYMBOL(__start_pci_fixups_suspend) = .;         \
 340 -               *(.pci_fixup_suspend)                                   \
 341 +               KEEP(*(.pci_fixup_suspend))                             \
 342                 VMLINUX_SYMBOL(__end_pci_fixups_suspend) = .;           \
 343                 VMLINUX_SYMBOL(__start_pci_fixups_suspend_late) = .;    \
 344 -               *(.pci_fixup_suspend_late)                              \
 345 +               KEEP(*(.pci_fixup_suspend_late))                        \
 346                 VMLINUX_SYMBOL(__end_pci_fixups_suspend_late) = .;      \
 347         }                                                               \
 348                                                                         \
 349         /* Built-in firmware blobs */                                   \
 350         .builtin_fw        : AT(ADDR(.builtin_fw) - LOAD_OFFSET) {      \
 351                 VMLINUX_SYMBOL(__start_builtin_fw) = .;                 \
 352 -               *(.builtin_fw)                                          \
 353 +               KEEP(*(.builtin_fw))                                    \
 354                 VMLINUX_SYMBOL(__end_builtin_fw) = .;                   \
 355         }                                                               \
 356                                                                         \
 357 @@ -410,7 +411,7 @@
 358                                                                         \
 359         /* Kernel symbol table: strings */                              \
 360          __ksymtab_strings : AT(ADDR(__ksymtab_strings) - LOAD_OFFSET) {        \
 361 -               KEEP(*(__ksymtab_strings))                              \
 362 +               *(__ksymtab_strings)                                    \
 363         }                                                               \
 364                                                                         \
 365         /* __*init sections */                                          \
 366 @@ -423,14 +424,14 @@
 367         /* Built-in module parameters. */                               \
 368         __param : AT(ADDR(__param) - LOAD_OFFSET) {                     \
 369                 VMLINUX_SYMBOL(__start___param) = .;                    \
 370 -               *(__param)                                              \
 371 +               KEEP(*(__param))                                        \
 372                 VMLINUX_SYMBOL(__stop___param) = .;                     \
 373         }                                                               \
 374                                                                         \
 375         /* Built-in module versions. */                                 \
 376         __modver : AT(ADDR(__modver) - LOAD_OFFSET) {                   \
 377                 VMLINUX_SYMBOL(__start___modver) = .;                   \
 378 -               *(__modver)                                             \
 379 +               KEEP(*(__modver))                                       \
 380                 VMLINUX_SYMBOL(__stop___modver) = .;                    \
 381                 . = ALIGN((align));                                     \
 382                 VMLINUX_SYMBOL(__end_rodata) = .;                       \
 383 @@ -496,7 +497,7 @@
 384  #define ENTRY_TEXT                                                     \
 385                 ALIGN_FUNCTION();                                       \
 386                 VMLINUX_SYMBOL(__entry_text_start) = .;                 \
 387 -               *(.entry.text)                                          \
 388 +               KEEP(*(.entry.text))                                    \
 389                 VMLINUX_SYMBOL(__entry_text_end) = .;
 390
 391  #if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN)
 392 @@ -534,7 +535,7 @@
 393         . = ALIGN(align);                                               \
 394         __ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) {               \
 395                 VMLINUX_SYMBOL(__start___ex_table) = .;                 \
 396 -               *(__ex_table)                                           \
 397 +               KEEP(*(__ex_table))                                             \
 398                 VMLINUX_SYMBOL(__stop___ex_table) = .;                  \
 399         }
 400
 401 @@ -550,9 +551,9 @@
 402  #ifdef CONFIG_CONSTRUCTORS
 403  #define KERNEL_CTORS() . = ALIGN(8);                      \
 404                         VMLINUX_SYMBOL(__ctors_start) = .; \
 405 -                       *(.ctors)                          \
 406 +                       KEEP(*(.ctors))                    \
 407                         *(SORT(.init_array.*))             \
 408 -                       *(.init_array)                     \
 409 +                       KEEP(*(.init_array))               \
 410                         VMLINUX_SYMBOL(__ctors_end) = .;
 411  #else
 412  #define KERNEL_CTORS()
 413 @@ -609,7 +610,7 @@
 414  #define SBSS(sbss_align)                                               \
 415         . = ALIGN(sbss_align);                                          \
 416         .sbss : AT(ADDR(.sbss) - LOAD_OFFSET) {                         \
 417 -               *(.sbss)                                                \
 418 +               *(.sbss .sbss.*)                                        \
 419                 *(.scommon)                                             \
 420         }
 421
 422 @@ -676,7 +677,7 @@
 423         . = ALIGN(8);                                                   \
 424         __bug_table : AT(ADDR(__bug_table) - LOAD_OFFSET) {             \
 425                 VMLINUX_SYMBOL(__start___bug_table) = .;                \
 426 -               *(__bug_table)                                          \
 427 +               KEEP(*(__bug_table))                                    \
 428                 VMLINUX_SYMBOL(__stop___bug_table) = .;                 \
 429         }
 430  #else
 431 @@ -688,7 +689,7 @@
 432         . = ALIGN(4);                                                   \
 433         .tracedata : AT(ADDR(.tracedata) - LOAD_OFFSET) {               \
 434                 VMLINUX_SYMBOL(__tracedata_start) = .;                  \
 435 -               *(.tracedata)                                           \
 436 +               KEEP(*(.tracedata))                                     \
 437                 VMLINUX_SYMBOL(__tracedata_end) = .;                    \
 438         }
 439  #else
 440 @@ -705,7 +706,7 @@
 441  #define INIT_SETUP(initsetup_align)                                    \
 442                 . = ALIGN(initsetup_align);                             \
 443                 VMLINUX_SYMBOL(__setup_start) = .;                      \
 444 -               *(.init.setup)                                          \
 445 +               KEEP(*(.init.setup))                                    \
 446                 VMLINUX_SYMBOL(__setup_end) = .;
 447
 448  #define INIT_CALLS_LEVEL(level)                                                \