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 @@ -67,7 +67,7 @@ SECTIONS
34 /* Exception table for data bus errors */
36 __start___dbe_table = .;
38 + KEEP(*(__dbe_table))
39 __stop___dbe_table = .;
42 @@ -112,7 +112,7 @@ 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) = .;
97 #define FTRACE_EVENTS()
100 #ifdef CONFIG_TRACING
101 #define TRACE_PRINTKS() VMLINUX_SYMBOL(__start___trace_bprintk_fmt) = .; \
102 - *(__trace_printk_fmt) /* Trace_printk fmt' pointer */ \
103 + KEEP(*(__trace_printk_fmt)) /* Trace_printk fmt' pointer */ \
104 VMLINUX_SYMBOL(__stop___trace_bprintk_fmt) = .;
105 #define TRACEPOINT_STR() VMLINUX_SYMBOL(__start___tracepoint_str) = .; \
106 *(__tracepoint_str) /* Trace_printk fmt' pointer */ \
108 #ifdef CONFIG_FTRACE_SYSCALLS
109 #define TRACE_SYSCALLS() . = ALIGN(8); \
110 VMLINUX_SYMBOL(__start_syscalls_metadata) = .; \
111 - *(__syscalls_metadata) \
112 + KEEP(*(__syscalls_metadata)) \
113 VMLINUX_SYMBOL(__stop_syscalls_metadata) = .;
115 #define TRACE_SYSCALLS()
117 #define _OF_TABLE_1(name) \
119 VMLINUX_SYMBOL(__##name##_of_table) = .; \
120 - *(__##name##_of_table) \
121 - *(__##name##_of_table_end)
122 + KEEP(*(__##name##_of_table)) \
123 + KEEP(*(__##name##_of_table_end))
125 #define CLKSRC_OF_TABLES() OF_TABLE(CONFIG_CLKSRC_OF, clksrc)
126 #define IRQCHIP_OF_MATCH_TABLE() OF_TABLE(CONFIG_IRQCHIP, irqchip)
128 #define KERNEL_DTB() \
130 VMLINUX_SYMBOL(__dtb_start) = .; \
131 - *(.dtb.init.rodata) \
132 + KEEP(*(.dtb.init.rodata)) \
133 VMLINUX_SYMBOL(__dtb_end) = .;
136 @@ -187,16 +187,17 @@
137 /* implement dynamic printk debug */ \
139 VMLINUX_SYMBOL(__start___jump_table) = .; \
141 + KEEP(*(__jump_table)) \
142 VMLINUX_SYMBOL(__stop___jump_table) = .; \
144 VMLINUX_SYMBOL(__start___verbose) = .; \
146 + KEEP(*(__verbose)) \
147 VMLINUX_SYMBOL(__stop___verbose) = .; \
153 + *(.data.[a-zA-Z_]*)
156 * Data section helpers
157 @@ -250,35 +251,35 @@
159 .pci_fixup : AT(ADDR(.pci_fixup) - LOAD_OFFSET) { \
160 VMLINUX_SYMBOL(__start_pci_fixups_early) = .; \
161 - *(.pci_fixup_early) \
162 + KEEP(*(.pci_fixup_early)) \
163 VMLINUX_SYMBOL(__end_pci_fixups_early) = .; \
164 VMLINUX_SYMBOL(__start_pci_fixups_header) = .; \
165 - *(.pci_fixup_header) \
166 + KEEP(*(.pci_fixup_header)) \
167 VMLINUX_SYMBOL(__end_pci_fixups_header) = .; \
168 VMLINUX_SYMBOL(__start_pci_fixups_final) = .; \
169 - *(.pci_fixup_final) \
170 + KEEP(*(.pci_fixup_final)) \
171 VMLINUX_SYMBOL(__end_pci_fixups_final) = .; \
172 VMLINUX_SYMBOL(__start_pci_fixups_enable) = .; \
173 - *(.pci_fixup_enable) \
174 + KEEP(*(.pci_fixup_enable)) \
175 VMLINUX_SYMBOL(__end_pci_fixups_enable) = .; \
176 VMLINUX_SYMBOL(__start_pci_fixups_resume) = .; \
177 - *(.pci_fixup_resume) \
178 + KEEP(*(.pci_fixup_resume)) \
179 VMLINUX_SYMBOL(__end_pci_fixups_resume) = .; \
180 VMLINUX_SYMBOL(__start_pci_fixups_resume_early) = .; \
181 - *(.pci_fixup_resume_early) \
182 + KEEP(*(.pci_fixup_resume_early)) \
183 VMLINUX_SYMBOL(__end_pci_fixups_resume_early) = .; \
184 VMLINUX_SYMBOL(__start_pci_fixups_suspend) = .; \
185 - *(.pci_fixup_suspend) \
186 + KEEP(*(.pci_fixup_suspend)) \
187 VMLINUX_SYMBOL(__end_pci_fixups_suspend) = .; \
188 VMLINUX_SYMBOL(__start_pci_fixups_suspend_late) = .; \
189 - *(.pci_fixup_suspend_late) \
190 + KEEP(*(.pci_fixup_suspend_late)) \
191 VMLINUX_SYMBOL(__end_pci_fixups_suspend_late) = .; \
194 /* Built-in firmware blobs */ \
195 .builtin_fw : AT(ADDR(.builtin_fw) - LOAD_OFFSET) { \
196 VMLINUX_SYMBOL(__start_builtin_fw) = .; \
198 + KEEP(*(.builtin_fw)) \
199 VMLINUX_SYMBOL(__end_builtin_fw) = .; \
202 @@ -287,49 +288,49 @@
203 /* Kernel symbol table: Normal symbols */ \
204 __ksymtab : AT(ADDR(__ksymtab) - LOAD_OFFSET) { \
205 VMLINUX_SYMBOL(__start___ksymtab) = .; \
206 - *(SORT(___ksymtab+*)) \
207 + KEEP(*(SORT(___ksymtab+*))) \
208 VMLINUX_SYMBOL(__stop___ksymtab) = .; \
211 /* Kernel symbol table: GPL-only symbols */ \
212 __ksymtab_gpl : AT(ADDR(__ksymtab_gpl) - LOAD_OFFSET) { \
213 VMLINUX_SYMBOL(__start___ksymtab_gpl) = .; \
214 - *(SORT(___ksymtab_gpl+*)) \
215 + KEEP(*(SORT(___ksymtab_gpl+*))) \
216 VMLINUX_SYMBOL(__stop___ksymtab_gpl) = .; \
219 /* Kernel symbol table: Normal unused symbols */ \
220 __ksymtab_unused : AT(ADDR(__ksymtab_unused) - LOAD_OFFSET) { \
221 VMLINUX_SYMBOL(__start___ksymtab_unused) = .; \
222 - *(SORT(___ksymtab_unused+*)) \
223 + KEEP(*(SORT(___ksymtab_unused+*))) \
224 VMLINUX_SYMBOL(__stop___ksymtab_unused) = .; \
227 /* Kernel symbol table: GPL-only unused symbols */ \
228 __ksymtab_unused_gpl : AT(ADDR(__ksymtab_unused_gpl) - LOAD_OFFSET) { \
229 VMLINUX_SYMBOL(__start___ksymtab_unused_gpl) = .; \
230 - *(SORT(___ksymtab_unused_gpl+*)) \
231 + KEEP(*(SORT(___ksymtab_unused_gpl+*))) \
232 VMLINUX_SYMBOL(__stop___ksymtab_unused_gpl) = .; \
235 /* Kernel symbol table: GPL-future-only symbols */ \
236 __ksymtab_gpl_future : AT(ADDR(__ksymtab_gpl_future) - LOAD_OFFSET) { \
237 VMLINUX_SYMBOL(__start___ksymtab_gpl_future) = .; \
238 - *(SORT(___ksymtab_gpl_future+*)) \
239 + KEEP(*(SORT(___ksymtab_gpl_future+*))) \
240 VMLINUX_SYMBOL(__stop___ksymtab_gpl_future) = .; \
243 /* Kernel symbol table: Normal symbols */ \
244 __kcrctab : AT(ADDR(__kcrctab) - LOAD_OFFSET) { \
245 VMLINUX_SYMBOL(__start___kcrctab) = .; \
246 - *(SORT(___kcrctab+*)) \
247 + KEEP(*(SORT(___kcrctab+*))) \
248 VMLINUX_SYMBOL(__stop___kcrctab) = .; \
251 /* Kernel symbol table: GPL-only symbols */ \
252 __kcrctab_gpl : AT(ADDR(__kcrctab_gpl) - LOAD_OFFSET) { \
253 VMLINUX_SYMBOL(__start___kcrctab_gpl) = .; \
254 - *(SORT(___kcrctab_gpl+*)) \
255 + KEEP(*(SORT(___kcrctab_gpl+*))) \
256 VMLINUX_SYMBOL(__stop___kcrctab_gpl) = .; \
259 @@ -343,14 +344,14 @@
260 /* Kernel symbol table: GPL-only unused symbols */ \
261 __kcrctab_unused_gpl : AT(ADDR(__kcrctab_unused_gpl) - LOAD_OFFSET) { \
262 VMLINUX_SYMBOL(__start___kcrctab_unused_gpl) = .; \
263 - *(SORT(___kcrctab_unused_gpl+*)) \
264 + KEEP(*(SORT(___kcrctab_unused_gpl+*))) \
265 VMLINUX_SYMBOL(__stop___kcrctab_unused_gpl) = .; \
268 /* Kernel symbol table: GPL-future-only symbols */ \
269 __kcrctab_gpl_future : AT(ADDR(__kcrctab_gpl_future) - LOAD_OFFSET) { \
270 VMLINUX_SYMBOL(__start___kcrctab_gpl_future) = .; \
271 - *(SORT(___kcrctab_gpl_future+*)) \
272 + KEEP(*(SORT(___kcrctab_gpl_future+*))) \
273 VMLINUX_SYMBOL(__stop___kcrctab_gpl_future) = .; \
276 @@ -369,14 +370,14 @@
277 /* Built-in module parameters. */ \
278 __param : AT(ADDR(__param) - LOAD_OFFSET) { \
279 VMLINUX_SYMBOL(__start___param) = .; \
282 VMLINUX_SYMBOL(__stop___param) = .; \
285 /* Built-in module versions. */ \
286 __modver : AT(ADDR(__modver) - LOAD_OFFSET) { \
287 VMLINUX_SYMBOL(__start___modver) = .; \
289 + KEEP(*(__modver)) \
290 VMLINUX_SYMBOL(__stop___modver) = .; \
291 . = ALIGN((align)); \
292 VMLINUX_SYMBOL(__end_rodata) = .; \
296 VMLINUX_SYMBOL(__entry_text_start) = .; \
298 + KEEP(*(.entry.text)) \
299 VMLINUX_SYMBOL(__entry_text_end) = .;
301 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
304 __ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) { \
305 VMLINUX_SYMBOL(__start___ex_table) = .; \
307 + KEEP(*(__ex_table)) \
308 VMLINUX_SYMBOL(__stop___ex_table) = .; \
312 #ifdef CONFIG_CONSTRUCTORS
313 #define KERNEL_CTORS() . = ALIGN(8); \
314 VMLINUX_SYMBOL(__ctors_start) = .; \
318 + KEEP(*(.init_array)) \
319 VMLINUX_SYMBOL(__ctors_end) = .;
321 #define KERNEL_CTORS()
323 #define SBSS(sbss_align) \
324 . = ALIGN(sbss_align); \
325 .sbss : AT(ADDR(.sbss) - LOAD_OFFSET) { \
333 *(.bss..page_aligned) \
342 __bug_table : AT(ADDR(__bug_table) - LOAD_OFFSET) { \
343 VMLINUX_SYMBOL(__start___bug_table) = .; \
345 + KEEP(*(__bug_table)) \
346 VMLINUX_SYMBOL(__stop___bug_table) = .; \
351 .tracedata : AT(ADDR(.tracedata) - LOAD_OFFSET) { \
352 VMLINUX_SYMBOL(__tracedata_start) = .; \
354 + KEEP(*(.tracedata)) \
355 VMLINUX_SYMBOL(__tracedata_end) = .; \
358 @@ -621,17 +622,17 @@
359 #define INIT_SETUP(initsetup_align) \
360 . = ALIGN(initsetup_align); \
361 VMLINUX_SYMBOL(__setup_start) = .; \
363 + KEEP(*(.init.setup)) \
364 VMLINUX_SYMBOL(__setup_end) = .;
366 #define INIT_CALLS_LEVEL(level) \
367 VMLINUX_SYMBOL(__initcall##level##_start) = .; \
368 - *(.initcall##level##.init) \
369 - *(.initcall##level##s.init) \
370 + KEEP(*(.initcall##level##.init)) \
371 + KEEP(*(.initcall##level##s.init)) \
374 VMLINUX_SYMBOL(__initcall_start) = .; \
375 - *(.initcallearly.init) \
376 + KEEP(*(.initcallearly.init)) \
377 INIT_CALLS_LEVEL(0) \
378 INIT_CALLS_LEVEL(1) \
379 INIT_CALLS_LEVEL(2) \
380 @@ -645,21 +646,21 @@
382 #define CON_INITCALL \
383 VMLINUX_SYMBOL(__con_initcall_start) = .; \
384 - *(.con_initcall.init) \
385 + KEEP(*(.con_initcall.init)) \
386 VMLINUX_SYMBOL(__con_initcall_end) = .;
388 #define SECURITY_INITCALL \
389 VMLINUX_SYMBOL(__security_initcall_start) = .; \
390 - *(.security_initcall.init) \
391 + KEEP(*(.security_initcall.init)) \
392 VMLINUX_SYMBOL(__security_initcall_end) = .;
394 #ifdef CONFIG_BLK_DEV_INITRD
395 #define INIT_RAM_FS \
397 VMLINUX_SYMBOL(__initramfs_start) = .; \
399 + KEEP(*(.init.ramfs)) \
401 - *(.init.ramfs.info)
402 + KEEP(*(.init.ramfs.info))
406 --- a/arch/arm/Makefile
407 +++ b/arch/arm/Makefile
408 @@ -18,11 +18,16 @@ ifeq ($(CONFIG_CPU_ENDIAN_BE8),y)
409 LDFLAGS_vmlinux += --be8
410 LDFLAGS_MODULE += --be8
412 +LDFLAGS_vmlinux += --gc-sections
414 OBJCOPYFLAGS :=-O binary -R .comment -S
416 #KBUILD_CFLAGS +=-pipe
418 +ifndef CONFIG_FUNCTION_TRACER
419 +KBUILD_CFLAGS_KERNEL += -ffunction-sections -fdata-sections
422 # Never generate .eh_frame
423 KBUILD_CFLAGS += $(call cc-option,-fno-dwarf2-cfi-asm)
425 --- a/arch/arm/kernel/vmlinux.lds.S
426 +++ b/arch/arm/kernel/vmlinux.lds.S
430 VMLINUX_SYMBOL(__proc_info_begin) = .; \
431 - *(.proc.info.init) \
432 + KEEP(*(.proc.info.init)) \
433 VMLINUX_SYMBOL(__proc_info_end) = .;
437 VMLINUX_SYMBOL(__idmap_text_start) = .; \
439 + KEEP(*(.idmap.text)) \
440 VMLINUX_SYMBOL(__idmap_text_end) = .; \
442 VMLINUX_SYMBOL(__hyp_idmap_text_start) = .; \
443 @@ -93,7 +93,7 @@ SECTIONS
444 .text : { /* Real text segment */
445 _stext = .; /* Text and read-only data */
446 __exception_text_start = .;
448 + KEEP(*(.exception.text))
449 __exception_text_end = .;
452 @@ -118,7 +118,7 @@ SECTIONS
453 __ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) {
454 __start___ex_table = .;
457 + KEEP(*(__ex_table))
459 __stop___ex_table = .;
461 @@ -130,12 +130,12 @@ SECTIONS
464 __start_unwind_idx = .;
466 + KEEP(*(.ARM.exidx*))
467 __stop_unwind_idx = .;
470 __start_unwind_tab = .;
472 + KEEP(*(.ARM.extab*))
473 __stop_unwind_tab = .;
476 @@ -154,14 +154,14 @@ SECTIONS
479 .vectors 0 : AT(__vectors_start) {
483 . = __vectors_start + SIZEOF(.vectors);
487 .stubs 0x1000 : AT(__stubs_start) {
491 . = __stubs_start + SIZEOF(.stubs);
493 @@ -175,24 +175,24 @@ SECTIONS
496 __arch_info_begin = .;
498 + KEEP(*(.arch.info.init))
502 __tagtable_begin = .;
504 + KEEP(*(.taglist.init))
507 #ifdef CONFIG_SMP_ON_UP
511 + KEEP(*(.alt.smp.init))
516 __pv_table_begin = .;
522 --- a/arch/arm/boot/compressed/Makefile
523 +++ b/arch/arm/boot/compressed/Makefile
524 @@ -122,6 +122,7 @@ ifeq ($(CONFIG_FUNCTION_TRACER),y)
525 ORIG_CFLAGS := $(KBUILD_CFLAGS)
526 KBUILD_CFLAGS = $(subst -pg, , $(ORIG_CFLAGS))
528 +KBUILD_CFLAGS_KERNEL := $(patsubst -f%-sections,,$(KBUILD_CFLAGS_KERNEL))
530 ccflags-y := -fpic -mno-single-pic-base -fno-builtin -I$(obj)
531 asflags-y := -DZIMAGE