1 From: Felix Fietkau <nbd@openwrt.org>
3 use -ffunction-sections, -fdata-sections and --gc-sections --sort-section=name
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@openwrt.org>
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 --sort-section=name
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()
81 #ifdef CONFIG_EVENT_TRACING
82 #define FTRACE_EVENTS() . = ALIGN(8); \
83 VMLINUX_SYMBOL(__start_ftrace_events) = .; \
85 + KEEP(*(_ftrace_events)) \
86 VMLINUX_SYMBOL(__stop_ftrace_events) = .;
88 #define FTRACE_EVENTS()
92 #define TRACE_PRINTKS() VMLINUX_SYMBOL(__start___trace_bprintk_fmt) = .; \
93 - *(__trace_printk_fmt) /* Trace_printk fmt' pointer */ \
94 + KEEP(*(__trace_printk_fmt)) /* Trace_printk fmt' pointer */ \
95 VMLINUX_SYMBOL(__stop___trace_bprintk_fmt) = .;
96 #define TRACEPOINT_STR() VMLINUX_SYMBOL(__start___tracepoint_str) = .; \
97 *(__tracepoint_str) /* Trace_printk fmt' pointer */ \
99 #ifdef CONFIG_FTRACE_SYSCALLS
100 #define TRACE_SYSCALLS() . = ALIGN(8); \
101 VMLINUX_SYMBOL(__start_syscalls_metadata) = .; \
102 - *(__syscalls_metadata) \
103 + KEEP(*(__syscalls_metadata)) \
104 VMLINUX_SYMBOL(__stop_syscalls_metadata) = .;
106 #define TRACE_SYSCALLS()
108 #define _OF_TABLE_1(name) \
110 VMLINUX_SYMBOL(__##name##_of_table) = .; \
111 - *(__##name##_of_table) \
112 - *(__##name##_of_table_end)
113 + KEEP(*(__##name##_of_table)) \
114 + KEEP(*(__##name##_of_table_end))
116 #define CLKSRC_OF_TABLES() OF_TABLE(CONFIG_CLKSRC_OF, clksrc)
117 #define IRQCHIP_OF_MATCH_TABLE() OF_TABLE(CONFIG_IRQCHIP, irqchip)
119 #define KERNEL_DTB() \
121 VMLINUX_SYMBOL(__dtb_start) = .; \
122 - *(.dtb.init.rodata) \
123 + KEEP(*(.dtb.init.rodata)) \
124 VMLINUX_SYMBOL(__dtb_end) = .;
127 @@ -187,16 +187,17 @@
128 /* implement dynamic printk debug */ \
130 VMLINUX_SYMBOL(__start___jump_table) = .; \
132 + KEEP(*(__jump_table)) \
133 VMLINUX_SYMBOL(__stop___jump_table) = .; \
135 VMLINUX_SYMBOL(__start___verbose) = .; \
137 + KEEP(*(__verbose)) \
138 VMLINUX_SYMBOL(__stop___verbose) = .; \
144 + *(.data.[a-zA-Z_]*)
147 * Data section helpers
148 @@ -250,35 +251,35 @@
150 .pci_fixup : AT(ADDR(.pci_fixup) - LOAD_OFFSET) { \
151 VMLINUX_SYMBOL(__start_pci_fixups_early) = .; \
152 - *(.pci_fixup_early) \
153 + KEEP(*(.pci_fixup_early)) \
154 VMLINUX_SYMBOL(__end_pci_fixups_early) = .; \
155 VMLINUX_SYMBOL(__start_pci_fixups_header) = .; \
156 - *(.pci_fixup_header) \
157 + KEEP(*(.pci_fixup_header)) \
158 VMLINUX_SYMBOL(__end_pci_fixups_header) = .; \
159 VMLINUX_SYMBOL(__start_pci_fixups_final) = .; \
160 - *(.pci_fixup_final) \
161 + KEEP(*(.pci_fixup_final)) \
162 VMLINUX_SYMBOL(__end_pci_fixups_final) = .; \
163 VMLINUX_SYMBOL(__start_pci_fixups_enable) = .; \
164 - *(.pci_fixup_enable) \
165 + KEEP(*(.pci_fixup_enable)) \
166 VMLINUX_SYMBOL(__end_pci_fixups_enable) = .; \
167 VMLINUX_SYMBOL(__start_pci_fixups_resume) = .; \
168 - *(.pci_fixup_resume) \
169 + KEEP(*(.pci_fixup_resume)) \
170 VMLINUX_SYMBOL(__end_pci_fixups_resume) = .; \
171 VMLINUX_SYMBOL(__start_pci_fixups_resume_early) = .; \
172 - *(.pci_fixup_resume_early) \
173 + KEEP(*(.pci_fixup_resume_early)) \
174 VMLINUX_SYMBOL(__end_pci_fixups_resume_early) = .; \
175 VMLINUX_SYMBOL(__start_pci_fixups_suspend) = .; \
176 - *(.pci_fixup_suspend) \
177 + KEEP(*(.pci_fixup_suspend)) \
178 VMLINUX_SYMBOL(__end_pci_fixups_suspend) = .; \
179 VMLINUX_SYMBOL(__start_pci_fixups_suspend_late) = .; \
180 - *(.pci_fixup_suspend_late) \
181 + KEEP(*(.pci_fixup_suspend_late)) \
182 VMLINUX_SYMBOL(__end_pci_fixups_suspend_late) = .; \
185 /* Built-in firmware blobs */ \
186 .builtin_fw : AT(ADDR(.builtin_fw) - LOAD_OFFSET) { \
187 VMLINUX_SYMBOL(__start_builtin_fw) = .; \
189 + KEEP(*(.builtin_fw)) \
190 VMLINUX_SYMBOL(__end_builtin_fw) = .; \
193 @@ -287,49 +288,49 @@
194 /* Kernel symbol table: Normal symbols */ \
195 __ksymtab : AT(ADDR(__ksymtab) - LOAD_OFFSET) { \
196 VMLINUX_SYMBOL(__start___ksymtab) = .; \
197 - *(SORT(___ksymtab+*)) \
198 + KEEP(*(SORT(___ksymtab+*))) \
199 VMLINUX_SYMBOL(__stop___ksymtab) = .; \
202 /* Kernel symbol table: GPL-only symbols */ \
203 __ksymtab_gpl : AT(ADDR(__ksymtab_gpl) - LOAD_OFFSET) { \
204 VMLINUX_SYMBOL(__start___ksymtab_gpl) = .; \
205 - *(SORT(___ksymtab_gpl+*)) \
206 + KEEP(*(SORT(___ksymtab_gpl+*))) \
207 VMLINUX_SYMBOL(__stop___ksymtab_gpl) = .; \
210 /* Kernel symbol table: Normal unused symbols */ \
211 __ksymtab_unused : AT(ADDR(__ksymtab_unused) - LOAD_OFFSET) { \
212 VMLINUX_SYMBOL(__start___ksymtab_unused) = .; \
213 - *(SORT(___ksymtab_unused+*)) \
214 + KEEP(*(SORT(___ksymtab_unused+*))) \
215 VMLINUX_SYMBOL(__stop___ksymtab_unused) = .; \
218 /* Kernel symbol table: GPL-only unused symbols */ \
219 __ksymtab_unused_gpl : AT(ADDR(__ksymtab_unused_gpl) - LOAD_OFFSET) { \
220 VMLINUX_SYMBOL(__start___ksymtab_unused_gpl) = .; \
221 - *(SORT(___ksymtab_unused_gpl+*)) \
222 + KEEP(*(SORT(___ksymtab_unused_gpl+*))) \
223 VMLINUX_SYMBOL(__stop___ksymtab_unused_gpl) = .; \
226 /* Kernel symbol table: GPL-future-only symbols */ \
227 __ksymtab_gpl_future : AT(ADDR(__ksymtab_gpl_future) - LOAD_OFFSET) { \
228 VMLINUX_SYMBOL(__start___ksymtab_gpl_future) = .; \
229 - *(SORT(___ksymtab_gpl_future+*)) \
230 + KEEP(*(SORT(___ksymtab_gpl_future+*))) \
231 VMLINUX_SYMBOL(__stop___ksymtab_gpl_future) = .; \
234 /* Kernel symbol table: Normal symbols */ \
235 __kcrctab : AT(ADDR(__kcrctab) - LOAD_OFFSET) { \
236 VMLINUX_SYMBOL(__start___kcrctab) = .; \
237 - *(SORT(___kcrctab+*)) \
238 + KEEP(*(SORT(___kcrctab+*))) \
239 VMLINUX_SYMBOL(__stop___kcrctab) = .; \
242 /* Kernel symbol table: GPL-only symbols */ \
243 __kcrctab_gpl : AT(ADDR(__kcrctab_gpl) - LOAD_OFFSET) { \
244 VMLINUX_SYMBOL(__start___kcrctab_gpl) = .; \
245 - *(SORT(___kcrctab_gpl+*)) \
246 + KEEP(*(SORT(___kcrctab_gpl+*))) \
247 VMLINUX_SYMBOL(__stop___kcrctab_gpl) = .; \
250 @@ -343,14 +344,14 @@
251 /* Kernel symbol table: GPL-only unused symbols */ \
252 __kcrctab_unused_gpl : AT(ADDR(__kcrctab_unused_gpl) - LOAD_OFFSET) { \
253 VMLINUX_SYMBOL(__start___kcrctab_unused_gpl) = .; \
254 - *(SORT(___kcrctab_unused_gpl+*)) \
255 + KEEP(*(SORT(___kcrctab_unused_gpl+*))) \
256 VMLINUX_SYMBOL(__stop___kcrctab_unused_gpl) = .; \
259 /* Kernel symbol table: GPL-future-only symbols */ \
260 __kcrctab_gpl_future : AT(ADDR(__kcrctab_gpl_future) - LOAD_OFFSET) { \
261 VMLINUX_SYMBOL(__start___kcrctab_gpl_future) = .; \
262 - *(SORT(___kcrctab_gpl_future+*)) \
263 + KEEP(*(SORT(___kcrctab_gpl_future+*))) \
264 VMLINUX_SYMBOL(__stop___kcrctab_gpl_future) = .; \
267 @@ -369,14 +370,14 @@
268 /* Built-in module parameters. */ \
269 __param : AT(ADDR(__param) - LOAD_OFFSET) { \
270 VMLINUX_SYMBOL(__start___param) = .; \
273 VMLINUX_SYMBOL(__stop___param) = .; \
276 /* Built-in module versions. */ \
277 __modver : AT(ADDR(__modver) - LOAD_OFFSET) { \
278 VMLINUX_SYMBOL(__start___modver) = .; \
280 + KEEP(*(__modver)) \
281 VMLINUX_SYMBOL(__stop___modver) = .; \
282 . = ALIGN((align)); \
283 VMLINUX_SYMBOL(__end_rodata) = .; \
287 VMLINUX_SYMBOL(__entry_text_start) = .; \
289 + KEEP(*(.entry.text)) \
290 VMLINUX_SYMBOL(__entry_text_end) = .;
292 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
295 __ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) { \
296 VMLINUX_SYMBOL(__start___ex_table) = .; \
298 + KEEP(*(__ex_table)) \
299 VMLINUX_SYMBOL(__stop___ex_table) = .; \
303 #ifdef CONFIG_CONSTRUCTORS
304 #define KERNEL_CTORS() . = ALIGN(8); \
305 VMLINUX_SYMBOL(__ctors_start) = .; \
309 + KEEP(*(.init_array)) \
310 VMLINUX_SYMBOL(__ctors_end) = .;
312 #define KERNEL_CTORS()
314 #define SBSS(sbss_align) \
315 . = ALIGN(sbss_align); \
316 .sbss : AT(ADDR(.sbss) - LOAD_OFFSET) { \
324 *(.bss..page_aligned) \
333 .tracedata : AT(ADDR(.tracedata) - LOAD_OFFSET) { \
334 VMLINUX_SYMBOL(__tracedata_start) = .; \
336 + KEEP(*(.tracedata)) \
337 VMLINUX_SYMBOL(__tracedata_end) = .; \
340 @@ -621,17 +622,17 @@
341 #define INIT_SETUP(initsetup_align) \
342 . = ALIGN(initsetup_align); \
343 VMLINUX_SYMBOL(__setup_start) = .; \
345 + KEEP(*(.init.setup)) \
346 VMLINUX_SYMBOL(__setup_end) = .;
348 #define INIT_CALLS_LEVEL(level) \
349 VMLINUX_SYMBOL(__initcall##level##_start) = .; \
350 - *(.initcall##level##.init) \
351 - *(.initcall##level##s.init) \
352 + KEEP(*(.initcall##level##.init)) \
353 + KEEP(*(.initcall##level##s.init)) \
356 VMLINUX_SYMBOL(__initcall_start) = .; \
357 - *(.initcallearly.init) \
358 + KEEP(*(.initcallearly.init)) \
359 INIT_CALLS_LEVEL(0) \
360 INIT_CALLS_LEVEL(1) \
361 INIT_CALLS_LEVEL(2) \
362 @@ -645,21 +646,21 @@
364 #define CON_INITCALL \
365 VMLINUX_SYMBOL(__con_initcall_start) = .; \
366 - *(.con_initcall.init) \
367 + KEEP(*(.con_initcall.init)) \
368 VMLINUX_SYMBOL(__con_initcall_end) = .;
370 #define SECURITY_INITCALL \
371 VMLINUX_SYMBOL(__security_initcall_start) = .; \
372 - *(.security_initcall.init) \
373 + KEEP(*(.security_initcall.init)) \
374 VMLINUX_SYMBOL(__security_initcall_end) = .;
376 #ifdef CONFIG_BLK_DEV_INITRD
377 #define INIT_RAM_FS \
379 VMLINUX_SYMBOL(__initramfs_start) = .; \
381 + KEEP(*(.init.ramfs)) \
383 - *(.init.ramfs.info)
384 + KEEP(*(.init.ramfs.info))
388 --- a/arch/arm/Makefile
389 +++ b/arch/arm/Makefile
390 @@ -18,11 +18,16 @@ ifeq ($(CONFIG_CPU_ENDIAN_BE8),y)
391 LDFLAGS_vmlinux += --be8
392 LDFLAGS_MODULE += --be8
394 +LDFLAGS_vmlinux += --gc-sections --sort-section=name
396 OBJCOPYFLAGS :=-O binary -R .comment -S
398 #KBUILD_CFLAGS +=-pipe
400 +ifndef CONFIG_FUNCTION_TRACER
401 +KBUILD_CFLAGS_KERNEL += -ffunction-sections -fdata-sections
404 # Never generate .eh_frame
405 KBUILD_CFLAGS += $(call cc-option,-fno-dwarf2-cfi-asm)
407 --- a/arch/arm/kernel/vmlinux.lds.S
408 +++ b/arch/arm/kernel/vmlinux.lds.S
412 VMLINUX_SYMBOL(__proc_info_begin) = .; \
413 - *(.proc.info.init) \
414 + KEEP(*(.proc.info.init)) \
415 VMLINUX_SYMBOL(__proc_info_end) = .;
419 VMLINUX_SYMBOL(__idmap_text_start) = .; \
421 + KEEP(*(.idmap.text)) \
422 VMLINUX_SYMBOL(__idmap_text_end) = .; \
424 VMLINUX_SYMBOL(__hyp_idmap_text_start) = .; \
425 @@ -93,7 +93,7 @@ SECTIONS
426 .text : { /* Real text segment */
427 _stext = .; /* Text and read-only data */
428 __exception_text_start = .;
430 + KEEP(*(.exception.text))
431 __exception_text_end = .;
434 @@ -118,7 +118,7 @@ SECTIONS
435 __ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) {
436 __start___ex_table = .;
439 + KEEP(*(__ex_table))
441 __stop___ex_table = .;
443 @@ -130,12 +130,12 @@ SECTIONS
446 __start_unwind_idx = .;
448 + KEEP(*(.ARM.exidx*))
449 __stop_unwind_idx = .;
452 __start_unwind_tab = .;
454 + KEEP(*(.ARM.extab*))
455 __stop_unwind_tab = .;
458 @@ -154,14 +154,14 @@ SECTIONS
461 .vectors 0 : AT(__vectors_start) {
465 . = __vectors_start + SIZEOF(.vectors);
469 .stubs 0x1000 : AT(__stubs_start) {
473 . = __stubs_start + SIZEOF(.stubs);
475 @@ -175,24 +175,24 @@ SECTIONS
478 __arch_info_begin = .;
480 + KEEP(*(.arch.info.init))
484 __tagtable_begin = .;
486 + KEEP(*(.taglist.init))
489 #ifdef CONFIG_SMP_ON_UP
493 + KEEP(*(.alt.smp.init))
498 __pv_table_begin = .;
504 --- a/arch/arm/boot/compressed/Makefile
505 +++ b/arch/arm/boot/compressed/Makefile
506 @@ -122,6 +122,7 @@ ifeq ($(CONFIG_FUNCTION_TRACER),y)
507 ORIG_CFLAGS := $(KBUILD_CFLAGS)
508 KBUILD_CFLAGS = $(subst -pg, , $(ORIG_CFLAGS))
510 +KBUILD_CFLAGS_KERNEL := $(patsubst -f%-sections,,$(KBUILD_CFLAGS_KERNEL))
512 ccflags-y := -fpic -mno-single-pic-base -fno-builtin -I$(obj)
513 asflags-y := -DZIMAGE