1 From: Felix Fietkau <nbd@nbd.name>
3 use -ffunction-sections, -fdata-sections and --gc-sections
5 In combination with kernel symbol export stripping this significantly reduces
6 the kernel image size. Used on both ARM and MIPS architectures.
8 Signed-off-by: Felix Fietkau <nbd@nbd.name>
9 Signed-off-by: Jonas Gorski <jogo@openwrt.org>
10 Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
13 --- a/arch/mips/Makefile
14 +++ b/arch/mips/Makefile
15 @@ -89,10 +89,14 @@ all-$(CONFIG_SYS_SUPPORTS_ZBOOT)+= vmlin
17 cflags-y += -G 0 -mno-abicalls -fno-pic -pipe
18 cflags-y += -msoft-float
19 -LDFLAGS_vmlinux += -G 0 -static -n -nostdlib
20 +LDFLAGS_vmlinux += -G 0 -static -n -nostdlib --gc-sections
21 KBUILD_AFLAGS_MODULE += -mlong-calls
22 KBUILD_CFLAGS_MODULE += -mlong-calls
24 +ifndef CONFIG_FUNCTION_TRACER
25 +KBUILD_CFLAGS_KERNEL += -ffunction-sections -fdata-sections
29 # pass -msoft-float to GAS if it supports it. However on newer binutils
30 # (specifically newer than 2.24.51.20140728) we then also need to explicitly
31 --- a/arch/mips/kernel/vmlinux.lds.S
32 +++ b/arch/mips/kernel/vmlinux.lds.S
33 @@ -69,7 +69,7 @@ SECTIONS
34 /* Exception table for data bus errors */
36 __start___dbe_table = .;
38 + KEEP(*(__dbe_table))
39 __stop___dbe_table = .;
42 @@ -119,7 +119,7 @@ SECTIONS
44 .mips.machines.init : AT(ADDR(.mips.machines.init) - LOAD_OFFSET) {
45 __mips_machines_start = .;
46 - *(.mips.machines.init)
47 + KEEP(*(.mips.machines.init))
48 __mips_machines_end = .;
51 --- a/include/asm-generic/vmlinux.lds.h
52 +++ b/include/asm-generic/vmlinux.lds.h
54 #ifdef CONFIG_FTRACE_MCOUNT_RECORD
55 #define MCOUNT_REC() . = ALIGN(8); \
56 VMLINUX_SYMBOL(__start_mcount_loc) = .; \
58 + KEEP(*(__mcount_loc)) \
59 VMLINUX_SYMBOL(__stop_mcount_loc) = .;
64 #ifdef CONFIG_TRACE_BRANCH_PROFILING
65 #define LIKELY_PROFILE() VMLINUX_SYMBOL(__start_annotated_branch_profile) = .; \
66 - *(_ftrace_annotated_branch) \
67 + KEEP(*(_ftrace_annotated_branch)) \
68 VMLINUX_SYMBOL(__stop_annotated_branch_profile) = .;
70 #define LIKELY_PROFILE()
73 #ifdef CONFIG_PROFILE_ALL_BRANCHES
74 #define BRANCH_PROFILE() VMLINUX_SYMBOL(__start_branch_profile) = .; \
76 + KEEP(*(_ftrace_branch)) \
77 VMLINUX_SYMBOL(__stop_branch_profile) = .;
79 #define BRANCH_PROFILE()
82 #define KPROBE_BLACKLIST() . = ALIGN(8); \
83 VMLINUX_SYMBOL(__start_kprobe_blacklist) = .; \
84 - *(_kprobe_blacklist) \
85 + KEEP(*(_kprobe_blacklist)) \
86 VMLINUX_SYMBOL(__stop_kprobe_blacklist) = .;
88 #define KPROBE_BLACKLIST()
90 #ifdef CONFIG_EVENT_TRACING
91 #define FTRACE_EVENTS() . = ALIGN(8); \
92 VMLINUX_SYMBOL(__start_ftrace_events) = .; \
94 + KEEP(*(_ftrace_events)) \
95 VMLINUX_SYMBOL(__stop_ftrace_events) = .; \
96 VMLINUX_SYMBOL(__start_ftrace_enum_maps) = .; \
97 - *(_ftrace_enum_map) \
98 + KEEP(*(_ftrace_enum_map)) \
99 VMLINUX_SYMBOL(__stop_ftrace_enum_maps) = .;
101 #define FTRACE_EVENTS()
104 #ifdef CONFIG_TRACING
105 #define TRACE_PRINTKS() VMLINUX_SYMBOL(__start___trace_bprintk_fmt) = .; \
106 - *(__trace_printk_fmt) /* Trace_printk fmt' pointer */ \
107 + KEEP(*(__trace_printk_fmt)) /* Trace_printk fmt' pointer */ \
108 VMLINUX_SYMBOL(__stop___trace_bprintk_fmt) = .;
109 #define TRACEPOINT_STR() VMLINUX_SYMBOL(__start___tracepoint_str) = .; \
110 *(__tracepoint_str) /* Trace_printk fmt' pointer */ \
112 #ifdef CONFIG_FTRACE_SYSCALLS
113 #define TRACE_SYSCALLS() . = ALIGN(8); \
114 VMLINUX_SYMBOL(__start_syscalls_metadata) = .; \
115 - *(__syscalls_metadata) \
116 + KEEP(*(__syscalls_metadata)) \
117 VMLINUX_SYMBOL(__stop_syscalls_metadata) = .;
119 #define TRACE_SYSCALLS()
121 #define _OF_TABLE_1(name) \
123 VMLINUX_SYMBOL(__##name##_of_table) = .; \
124 - *(__##name##_of_table) \
125 - *(__##name##_of_table_end)
126 + KEEP(*(__##name##_of_table)) \
127 + KEEP(*(__##name##_of_table_end))
129 #define CLKSRC_OF_TABLES() OF_TABLE(CONFIG_CLKSRC_OF, clksrc)
130 #define IRQCHIP_OF_MATCH_TABLE() OF_TABLE(CONFIG_IRQCHIP, irqchip)
132 #define KERNEL_DTB() \
134 VMLINUX_SYMBOL(__dtb_start) = .; \
135 - *(.dtb.init.rodata) \
136 + KEEP(*(.dtb.init.rodata)) \
137 VMLINUX_SYMBOL(__dtb_end) = .;
140 @@ -210,16 +210,17 @@
141 /* implement dynamic printk debug */ \
143 VMLINUX_SYMBOL(__start___jump_table) = .; \
145 + KEEP(*(__jump_table)) \
146 VMLINUX_SYMBOL(__stop___jump_table) = .; \
148 VMLINUX_SYMBOL(__start___verbose) = .; \
150 + KEEP(*(__verbose)) \
151 VMLINUX_SYMBOL(__stop___verbose) = .; \
157 + *(.data.[a-zA-Z_]*)
160 * Data section helpers
161 @@ -273,35 +274,35 @@
163 .pci_fixup : AT(ADDR(.pci_fixup) - LOAD_OFFSET) { \
164 VMLINUX_SYMBOL(__start_pci_fixups_early) = .; \
165 - *(.pci_fixup_early) \
166 + KEEP(*(.pci_fixup_early)) \
167 VMLINUX_SYMBOL(__end_pci_fixups_early) = .; \
168 VMLINUX_SYMBOL(__start_pci_fixups_header) = .; \
169 - *(.pci_fixup_header) \
170 + KEEP(*(.pci_fixup_header)) \
171 VMLINUX_SYMBOL(__end_pci_fixups_header) = .; \
172 VMLINUX_SYMBOL(__start_pci_fixups_final) = .; \
173 - *(.pci_fixup_final) \
174 + KEEP(*(.pci_fixup_final)) \
175 VMLINUX_SYMBOL(__end_pci_fixups_final) = .; \
176 VMLINUX_SYMBOL(__start_pci_fixups_enable) = .; \
177 - *(.pci_fixup_enable) \
178 + KEEP(*(.pci_fixup_enable)) \
179 VMLINUX_SYMBOL(__end_pci_fixups_enable) = .; \
180 VMLINUX_SYMBOL(__start_pci_fixups_resume) = .; \
181 - *(.pci_fixup_resume) \
182 + KEEP(*(.pci_fixup_resume)) \
183 VMLINUX_SYMBOL(__end_pci_fixups_resume) = .; \
184 VMLINUX_SYMBOL(__start_pci_fixups_resume_early) = .; \
185 - *(.pci_fixup_resume_early) \
186 + KEEP(*(.pci_fixup_resume_early)) \
187 VMLINUX_SYMBOL(__end_pci_fixups_resume_early) = .; \
188 VMLINUX_SYMBOL(__start_pci_fixups_suspend) = .; \
189 - *(.pci_fixup_suspend) \
190 + KEEP(*(.pci_fixup_suspend)) \
191 VMLINUX_SYMBOL(__end_pci_fixups_suspend) = .; \
192 VMLINUX_SYMBOL(__start_pci_fixups_suspend_late) = .; \
193 - *(.pci_fixup_suspend_late) \
194 + KEEP(*(.pci_fixup_suspend_late)) \
195 VMLINUX_SYMBOL(__end_pci_fixups_suspend_late) = .; \
198 /* Built-in firmware blobs */ \
199 .builtin_fw : AT(ADDR(.builtin_fw) - LOAD_OFFSET) { \
200 VMLINUX_SYMBOL(__start_builtin_fw) = .; \
202 + KEEP(*(.builtin_fw)) \
203 VMLINUX_SYMBOL(__end_builtin_fw) = .; \
206 @@ -310,49 +311,49 @@
207 /* Kernel symbol table: Normal symbols */ \
208 __ksymtab : AT(ADDR(__ksymtab) - LOAD_OFFSET) { \
209 VMLINUX_SYMBOL(__start___ksymtab) = .; \
210 - *(SORT(___ksymtab+*)) \
211 + KEEP(*(SORT(___ksymtab+*))) \
212 VMLINUX_SYMBOL(__stop___ksymtab) = .; \
215 /* Kernel symbol table: GPL-only symbols */ \
216 __ksymtab_gpl : AT(ADDR(__ksymtab_gpl) - LOAD_OFFSET) { \
217 VMLINUX_SYMBOL(__start___ksymtab_gpl) = .; \
218 - *(SORT(___ksymtab_gpl+*)) \
219 + KEEP(*(SORT(___ksymtab_gpl+*))) \
220 VMLINUX_SYMBOL(__stop___ksymtab_gpl) = .; \
223 /* Kernel symbol table: Normal unused symbols */ \
224 __ksymtab_unused : AT(ADDR(__ksymtab_unused) - LOAD_OFFSET) { \
225 VMLINUX_SYMBOL(__start___ksymtab_unused) = .; \
226 - *(SORT(___ksymtab_unused+*)) \
227 + KEEP(*(SORT(___ksymtab_unused+*))) \
228 VMLINUX_SYMBOL(__stop___ksymtab_unused) = .; \
231 /* Kernel symbol table: GPL-only unused symbols */ \
232 __ksymtab_unused_gpl : AT(ADDR(__ksymtab_unused_gpl) - LOAD_OFFSET) { \
233 VMLINUX_SYMBOL(__start___ksymtab_unused_gpl) = .; \
234 - *(SORT(___ksymtab_unused_gpl+*)) \
235 + KEEP(*(SORT(___ksymtab_unused_gpl+*))) \
236 VMLINUX_SYMBOL(__stop___ksymtab_unused_gpl) = .; \
239 /* Kernel symbol table: GPL-future-only symbols */ \
240 __ksymtab_gpl_future : AT(ADDR(__ksymtab_gpl_future) - LOAD_OFFSET) { \
241 VMLINUX_SYMBOL(__start___ksymtab_gpl_future) = .; \
242 - *(SORT(___ksymtab_gpl_future+*)) \
243 + KEEP(*(SORT(___ksymtab_gpl_future+*))) \
244 VMLINUX_SYMBOL(__stop___ksymtab_gpl_future) = .; \
247 /* Kernel symbol table: Normal symbols */ \
248 __kcrctab : AT(ADDR(__kcrctab) - LOAD_OFFSET) { \
249 VMLINUX_SYMBOL(__start___kcrctab) = .; \
250 - *(SORT(___kcrctab+*)) \
251 + KEEP(*(SORT(___kcrctab+*))) \
252 VMLINUX_SYMBOL(__stop___kcrctab) = .; \
255 /* Kernel symbol table: GPL-only symbols */ \
256 __kcrctab_gpl : AT(ADDR(__kcrctab_gpl) - LOAD_OFFSET) { \
257 VMLINUX_SYMBOL(__start___kcrctab_gpl) = .; \
258 - *(SORT(___kcrctab_gpl+*)) \
259 + KEEP(*(SORT(___kcrctab_gpl+*))) \
260 VMLINUX_SYMBOL(__stop___kcrctab_gpl) = .; \
263 @@ -366,14 +367,14 @@
264 /* Kernel symbol table: GPL-only unused symbols */ \
265 __kcrctab_unused_gpl : AT(ADDR(__kcrctab_unused_gpl) - LOAD_OFFSET) { \
266 VMLINUX_SYMBOL(__start___kcrctab_unused_gpl) = .; \
267 - *(SORT(___kcrctab_unused_gpl+*)) \
268 + KEEP(*(SORT(___kcrctab_unused_gpl+*))) \
269 VMLINUX_SYMBOL(__stop___kcrctab_unused_gpl) = .; \
272 /* Kernel symbol table: GPL-future-only symbols */ \
273 __kcrctab_gpl_future : AT(ADDR(__kcrctab_gpl_future) - LOAD_OFFSET) { \
274 VMLINUX_SYMBOL(__start___kcrctab_gpl_future) = .; \
275 - *(SORT(___kcrctab_gpl_future+*)) \
276 + KEEP(*(SORT(___kcrctab_gpl_future+*))) \
277 VMLINUX_SYMBOL(__stop___kcrctab_gpl_future) = .; \
280 @@ -392,14 +393,14 @@
281 /* Built-in module parameters. */ \
282 __param : AT(ADDR(__param) - LOAD_OFFSET) { \
283 VMLINUX_SYMBOL(__start___param) = .; \
286 VMLINUX_SYMBOL(__stop___param) = .; \
289 /* Built-in module versions. */ \
290 __modver : AT(ADDR(__modver) - LOAD_OFFSET) { \
291 VMLINUX_SYMBOL(__start___modver) = .; \
293 + KEEP(*(__modver)) \
294 VMLINUX_SYMBOL(__stop___modver) = .; \
295 . = ALIGN((align)); \
296 VMLINUX_SYMBOL(__end_rodata) = .; \
300 VMLINUX_SYMBOL(__entry_text_start) = .; \
302 + KEEP(*(.entry.text)) \
303 VMLINUX_SYMBOL(__entry_text_end) = .;
305 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
308 __ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) { \
309 VMLINUX_SYMBOL(__start___ex_table) = .; \
311 + KEEP(*(__ex_table)) \
312 VMLINUX_SYMBOL(__stop___ex_table) = .; \
316 #ifdef CONFIG_CONSTRUCTORS
317 #define KERNEL_CTORS() . = ALIGN(8); \
318 VMLINUX_SYMBOL(__ctors_start) = .; \
321 *(SORT(.init_array.*)) \
323 + KEEP(*(.init_array)) \
324 VMLINUX_SYMBOL(__ctors_end) = .;
326 #define KERNEL_CTORS()
328 #define SBSS(sbss_align) \
329 . = ALIGN(sbss_align); \
330 .sbss : AT(ADDR(.sbss) - LOAD_OFFSET) { \
338 *(.bss..page_aligned) \
347 __bug_table : AT(ADDR(__bug_table) - LOAD_OFFSET) { \
348 VMLINUX_SYMBOL(__start___bug_table) = .; \
350 + KEEP(*(__bug_table)) \
351 VMLINUX_SYMBOL(__stop___bug_table) = .; \
356 .tracedata : AT(ADDR(.tracedata) - LOAD_OFFSET) { \
357 VMLINUX_SYMBOL(__tracedata_start) = .; \
359 + KEEP(*(.tracedata)) \
360 VMLINUX_SYMBOL(__tracedata_end) = .; \
363 @@ -652,17 +653,17 @@
364 #define INIT_SETUP(initsetup_align) \
365 . = ALIGN(initsetup_align); \
366 VMLINUX_SYMBOL(__setup_start) = .; \
368 + KEEP(*(.init.setup)) \
369 VMLINUX_SYMBOL(__setup_end) = .;
371 #define INIT_CALLS_LEVEL(level) \
372 VMLINUX_SYMBOL(__initcall##level##_start) = .; \
373 - *(.initcall##level##.init) \
374 - *(.initcall##level##s.init) \
375 + KEEP(*(.initcall##level##.init)) \
376 + KEEP(*(.initcall##level##s.init)) \
379 VMLINUX_SYMBOL(__initcall_start) = .; \
380 - *(.initcallearly.init) \
381 + KEEP(*(.initcallearly.init)) \
382 INIT_CALLS_LEVEL(0) \
383 INIT_CALLS_LEVEL(1) \
384 INIT_CALLS_LEVEL(2) \
385 @@ -676,21 +677,21 @@
387 #define CON_INITCALL \
388 VMLINUX_SYMBOL(__con_initcall_start) = .; \
389 - *(.con_initcall.init) \
390 + KEEP(*(.con_initcall.init)) \
391 VMLINUX_SYMBOL(__con_initcall_end) = .;
393 #define SECURITY_INITCALL \
394 VMLINUX_SYMBOL(__security_initcall_start) = .; \
395 - *(.security_initcall.init) \
396 + KEEP(*(.security_initcall.init)) \
397 VMLINUX_SYMBOL(__security_initcall_end) = .;
399 #ifdef CONFIG_BLK_DEV_INITRD
400 #define INIT_RAM_FS \
402 VMLINUX_SYMBOL(__initramfs_start) = .; \
404 + KEEP(*(.init.ramfs)) \
406 - *(.init.ramfs.info)
407 + KEEP(*(.init.ramfs.info))
411 --- a/arch/arm/Makefile
412 +++ b/arch/arm/Makefile
413 @@ -22,11 +22,16 @@ endif
414 ifeq ($(CONFIG_ARM_MODULE_PLTS),y)
415 LDFLAGS_MODULE += -T $(srctree)/arch/arm/kernel/module.lds
417 +LDFLAGS_vmlinux += --gc-sections
419 OBJCOPYFLAGS :=-O binary -R .comment -S
421 #KBUILD_CFLAGS +=-pipe
423 +ifndef CONFIG_FUNCTION_TRACER
424 +KBUILD_CFLAGS_KERNEL += -ffunction-sections -fdata-sections
427 # Never generate .eh_frame
428 KBUILD_CFLAGS += $(call cc-option,-fno-dwarf2-cfi-asm)
430 --- a/arch/arm/kernel/vmlinux.lds.S
431 +++ b/arch/arm/kernel/vmlinux.lds.S
435 VMLINUX_SYMBOL(__proc_info_begin) = .; \
436 - *(.proc.info.init) \
437 + KEEP(*(.proc.info.init)) \
438 VMLINUX_SYMBOL(__proc_info_end) = .;
442 VMLINUX_SYMBOL(__idmap_text_start) = .; \
444 + KEEP(*(.idmap.text)) \
445 VMLINUX_SYMBOL(__idmap_text_end) = .; \
446 . = ALIGN(PAGE_SIZE); \
447 VMLINUX_SYMBOL(__hyp_idmap_text_start) = .; \
448 @@ -102,7 +102,7 @@ SECTIONS
449 _stext = .; /* Text and read-only data */
451 __exception_text_start = .;
453 + KEEP(*(.exception.text))
454 __exception_text_end = .;
457 @@ -126,7 +126,7 @@ SECTIONS
458 __ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) {
459 __start___ex_table = .;
462 + KEEP(*(__ex_table))
464 __stop___ex_table = .;
466 @@ -138,12 +138,12 @@ SECTIONS
469 __start_unwind_idx = .;
471 + KEEP(*(.ARM.exidx*))
472 __stop_unwind_idx = .;
475 __start_unwind_tab = .;
477 + KEEP(*(.ARM.extab*))
478 __stop_unwind_tab = .;
481 @@ -166,14 +166,14 @@ SECTIONS
484 .vectors 0 : AT(__vectors_start) {
488 . = __vectors_start + SIZEOF(.vectors);
492 .stubs 0x1000 : AT(__stubs_start) {
496 . = __stubs_start + SIZEOF(.stubs);
498 @@ -187,24 +187,24 @@ SECTIONS
501 __arch_info_begin = .;
503 + KEEP(*(.arch.info.init))
507 __tagtable_begin = .;
509 + KEEP(*(.taglist.init))
512 #ifdef CONFIG_SMP_ON_UP
516 + KEEP(*(.alt.smp.init))
521 __pv_table_begin = .;
527 --- a/arch/arm/boot/compressed/Makefile
528 +++ b/arch/arm/boot/compressed/Makefile
529 @@ -105,6 +105,7 @@ ifeq ($(CONFIG_FUNCTION_TRACER),y)
530 ORIG_CFLAGS := $(KBUILD_CFLAGS)
531 KBUILD_CFLAGS = $(subst -pg, , $(ORIG_CFLAGS))
533 +KBUILD_CFLAGS_KERNEL := $(patsubst -f%-sections,,$(KBUILD_CFLAGS_KERNEL))
535 ccflags-y := -fpic -mno-single-pic-base -fno-builtin -I$(obj)
536 asflags-y := -DZIMAGE