1 From: Felix Fietkau <nbd@openwrt.org>
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@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
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
28 cflags-y += -ffreestanding
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) = .;
97 #define TRACE_PRINTKS()
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 #ifdef CONFIG_CLKSRC_OF
109 #define CLKSRC_OF_TABLES() . = ALIGN(8); \
110 VMLINUX_SYMBOL(__clksrc_of_table) = .; \
111 - *(__clksrc_of_table) \
112 - *(__clksrc_of_table_end)
113 + KEEP(*(__clksrc_of_table)) \
114 + KEEP(*(__clksrc_of_table_end))
116 #define CLKSRC_OF_TABLES()
119 #define IRQCHIP_OF_MATCH_TABLE() \
121 VMLINUX_SYMBOL(__irqchip_begin) = .; \
122 - *(__irqchip_of_table) \
123 - *(__irqchip_of_end)
124 + KEEP(*(__irqchip_of_table)) \
125 + KEEP(*(__irqchip_of_end))
127 #define IRQCHIP_OF_MATCH_TABLE()
130 #ifdef CONFIG_COMMON_CLK
131 #define CLK_OF_TABLES() . = ALIGN(8); \
132 VMLINUX_SYMBOL(__clk_of_table) = .; \
133 - *(__clk_of_table) \
134 - *(__clk_of_table_end)
135 + KEEP(*(__clk_of_table)) \
136 + KEEP(*(__clk_of_table_end))
138 #define CLK_OF_TABLES()
141 #define KERNEL_DTB() \
143 VMLINUX_SYMBOL(__dtb_start) = .; \
144 - *(.dtb.init.rodata) \
145 + KEEP(*(.dtb.init.rodata)) \
146 VMLINUX_SYMBOL(__dtb_end) = .;
149 @@ -194,15 +194,16 @@
150 /* implement dynamic printk debug */ \
152 VMLINUX_SYMBOL(__start___jump_table) = .; \
154 + KEEP(*(__jump_table)) \
155 VMLINUX_SYMBOL(__stop___jump_table) = .; \
157 VMLINUX_SYMBOL(__start___verbose) = .; \
159 + KEEP(*(__verbose)) \
160 VMLINUX_SYMBOL(__stop___verbose) = .; \
165 + *(.data.[a-zA-Z_]*)
168 * Data section helpers
169 @@ -256,39 +257,39 @@
171 .pci_fixup : AT(ADDR(.pci_fixup) - LOAD_OFFSET) { \
172 VMLINUX_SYMBOL(__start_pci_fixups_early) = .; \
173 - *(.pci_fixup_early) \
174 + KEEP(*(.pci_fixup_early)) \
175 VMLINUX_SYMBOL(__end_pci_fixups_early) = .; \
176 VMLINUX_SYMBOL(__start_pci_fixups_header) = .; \
177 - *(.pci_fixup_header) \
178 + KEEP(*(.pci_fixup_header)) \
179 VMLINUX_SYMBOL(__end_pci_fixups_header) = .; \
180 VMLINUX_SYMBOL(__start_pci_fixups_final) = .; \
181 - *(.pci_fixup_final) \
182 + KEEP(*(.pci_fixup_final)) \
183 VMLINUX_SYMBOL(__end_pci_fixups_final) = .; \
184 VMLINUX_SYMBOL(__start_pci_fixups_enable) = .; \
185 - *(.pci_fixup_enable) \
186 + KEEP(*(.pci_fixup_enable)) \
187 VMLINUX_SYMBOL(__end_pci_fixups_enable) = .; \
188 VMLINUX_SYMBOL(__start_pci_fixups_resume) = .; \
189 - *(.pci_fixup_resume) \
190 + KEEP(*(.pci_fixup_resume)) \
191 VMLINUX_SYMBOL(__end_pci_fixups_resume) = .; \
192 VMLINUX_SYMBOL(__start_pci_fixups_resume_early) = .; \
193 - *(.pci_fixup_resume_early) \
194 + KEEP(*(.pci_fixup_resume_early)) \
195 VMLINUX_SYMBOL(__end_pci_fixups_resume_early) = .; \
196 VMLINUX_SYMBOL(__start_pci_fixups_suspend) = .; \
197 - *(.pci_fixup_suspend) \
198 + KEEP(*(.pci_fixup_suspend)) \
199 VMLINUX_SYMBOL(__end_pci_fixups_suspend) = .; \
202 /* Built-in firmware blobs */ \
203 .builtin_fw : AT(ADDR(.builtin_fw) - LOAD_OFFSET) { \
204 VMLINUX_SYMBOL(__start_builtin_fw) = .; \
206 + KEEP(*(.builtin_fw)) \
207 VMLINUX_SYMBOL(__end_builtin_fw) = .; \
210 /* RapidIO route ops */ \
211 .rio_ops : AT(ADDR(.rio_ops) - LOAD_OFFSET) { \
212 VMLINUX_SYMBOL(__start_rio_switch_ops) = .; \
213 - *(.rio_switch_ops) \
214 + KEEP(*(.rio_switch_ops)) \
215 VMLINUX_SYMBOL(__end_rio_switch_ops) = .; \
218 @@ -297,49 +298,49 @@
219 /* Kernel symbol table: Normal symbols */ \
220 __ksymtab : AT(ADDR(__ksymtab) - LOAD_OFFSET) { \
221 VMLINUX_SYMBOL(__start___ksymtab) = .; \
222 - *(SORT(___ksymtab+*)) \
223 + KEEP(*(SORT(___ksymtab+*))) \
224 VMLINUX_SYMBOL(__stop___ksymtab) = .; \
227 /* Kernel symbol table: GPL-only symbols */ \
228 __ksymtab_gpl : AT(ADDR(__ksymtab_gpl) - LOAD_OFFSET) { \
229 VMLINUX_SYMBOL(__start___ksymtab_gpl) = .; \
230 - *(SORT(___ksymtab_gpl+*)) \
231 + KEEP(*(SORT(___ksymtab_gpl+*))) \
232 VMLINUX_SYMBOL(__stop___ksymtab_gpl) = .; \
235 /* Kernel symbol table: Normal unused symbols */ \
236 __ksymtab_unused : AT(ADDR(__ksymtab_unused) - LOAD_OFFSET) { \
237 VMLINUX_SYMBOL(__start___ksymtab_unused) = .; \
238 - *(SORT(___ksymtab_unused+*)) \
239 + KEEP(*(SORT(___ksymtab_unused+*))) \
240 VMLINUX_SYMBOL(__stop___ksymtab_unused) = .; \
243 /* Kernel symbol table: GPL-only unused symbols */ \
244 __ksymtab_unused_gpl : AT(ADDR(__ksymtab_unused_gpl) - LOAD_OFFSET) { \
245 VMLINUX_SYMBOL(__start___ksymtab_unused_gpl) = .; \
246 - *(SORT(___ksymtab_unused_gpl+*)) \
247 + KEEP(*(SORT(___ksymtab_unused_gpl+*))) \
248 VMLINUX_SYMBOL(__stop___ksymtab_unused_gpl) = .; \
251 /* Kernel symbol table: GPL-future-only symbols */ \
252 __ksymtab_gpl_future : AT(ADDR(__ksymtab_gpl_future) - LOAD_OFFSET) { \
253 VMLINUX_SYMBOL(__start___ksymtab_gpl_future) = .; \
254 - *(SORT(___ksymtab_gpl_future+*)) \
255 + KEEP(*(SORT(___ksymtab_gpl_future+*))) \
256 VMLINUX_SYMBOL(__stop___ksymtab_gpl_future) = .; \
259 /* Kernel symbol table: Normal symbols */ \
260 __kcrctab : AT(ADDR(__kcrctab) - LOAD_OFFSET) { \
261 VMLINUX_SYMBOL(__start___kcrctab) = .; \
262 - *(SORT(___kcrctab+*)) \
263 + KEEP(*(SORT(___kcrctab+*))) \
264 VMLINUX_SYMBOL(__stop___kcrctab) = .; \
267 /* Kernel symbol table: GPL-only symbols */ \
268 __kcrctab_gpl : AT(ADDR(__kcrctab_gpl) - LOAD_OFFSET) { \
269 VMLINUX_SYMBOL(__start___kcrctab_gpl) = .; \
270 - *(SORT(___kcrctab_gpl+*)) \
271 + KEEP(*(SORT(___kcrctab_gpl+*))) \
272 VMLINUX_SYMBOL(__stop___kcrctab_gpl) = .; \
275 @@ -353,14 +354,14 @@
276 /* Kernel symbol table: GPL-only unused symbols */ \
277 __kcrctab_unused_gpl : AT(ADDR(__kcrctab_unused_gpl) - LOAD_OFFSET) { \
278 VMLINUX_SYMBOL(__start___kcrctab_unused_gpl) = .; \
279 - *(SORT(___kcrctab_unused_gpl+*)) \
280 + KEEP(*(SORT(___kcrctab_unused_gpl+*))) \
281 VMLINUX_SYMBOL(__stop___kcrctab_unused_gpl) = .; \
284 /* Kernel symbol table: GPL-future-only symbols */ \
285 __kcrctab_gpl_future : AT(ADDR(__kcrctab_gpl_future) - LOAD_OFFSET) { \
286 VMLINUX_SYMBOL(__start___kcrctab_gpl_future) = .; \
287 - *(SORT(___kcrctab_gpl_future+*)) \
288 + KEEP(*(SORT(___kcrctab_gpl_future+*))) \
289 VMLINUX_SYMBOL(__stop___kcrctab_gpl_future) = .; \
292 @@ -383,14 +384,14 @@
293 /* Built-in module parameters. */ \
294 __param : AT(ADDR(__param) - LOAD_OFFSET) { \
295 VMLINUX_SYMBOL(__start___param) = .; \
298 VMLINUX_SYMBOL(__stop___param) = .; \
301 /* Built-in module versions. */ \
302 __modver : AT(ADDR(__modver) - LOAD_OFFSET) { \
303 VMLINUX_SYMBOL(__start___modver) = .; \
305 + KEEP(*(__modver)) \
306 VMLINUX_SYMBOL(__stop___modver) = .; \
307 . = ALIGN((align)); \
308 VMLINUX_SYMBOL(__end_rodata) = .; \
312 VMLINUX_SYMBOL(__entry_text_start) = .; \
314 + KEEP(*(.entry.text)) \
315 VMLINUX_SYMBOL(__entry_text_end) = .;
317 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
320 __ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) { \
321 VMLINUX_SYMBOL(__start___ex_table) = .; \
323 + KEEP(*(__ex_table)) \
324 VMLINUX_SYMBOL(__stop___ex_table) = .; \
328 #ifdef CONFIG_CONSTRUCTORS
329 #define KERNEL_CTORS() . = ALIGN(8); \
330 VMLINUX_SYMBOL(__ctors_start) = .; \
333 VMLINUX_SYMBOL(__ctors_end) = .;
335 #define KERNEL_CTORS()
337 #define SBSS(sbss_align) \
338 . = ALIGN(sbss_align); \
339 .sbss : AT(ADDR(.sbss) - LOAD_OFFSET) { \
347 *(.bss..page_aligned) \
356 __bug_table : AT(ADDR(__bug_table) - LOAD_OFFSET) { \
357 VMLINUX_SYMBOL(__start___bug_table) = .; \
359 + KEEP(*(__bug_table)) \
360 VMLINUX_SYMBOL(__stop___bug_table) = .; \
365 .tracedata : AT(ADDR(.tracedata) - LOAD_OFFSET) { \
366 VMLINUX_SYMBOL(__tracedata_start) = .; \
368 + KEEP(*(.tracedata)) \
369 VMLINUX_SYMBOL(__tracedata_end) = .; \
372 @@ -646,17 +647,17 @@
373 #define INIT_SETUP(initsetup_align) \
374 . = ALIGN(initsetup_align); \
375 VMLINUX_SYMBOL(__setup_start) = .; \
377 + KEEP(*(.init.setup)) \
378 VMLINUX_SYMBOL(__setup_end) = .;
380 #define INIT_CALLS_LEVEL(level) \
381 VMLINUX_SYMBOL(__initcall##level##_start) = .; \
382 - *(.initcall##level##.init) \
383 - *(.initcall##level##s.init) \
384 + KEEP(*(.initcall##level##.init)) \
385 + KEEP(*(.initcall##level##s.init)) \
388 VMLINUX_SYMBOL(__initcall_start) = .; \
389 - *(.initcallearly.init) \
390 + KEEP(*(.initcallearly.init)) \
391 INIT_CALLS_LEVEL(0) \
392 INIT_CALLS_LEVEL(1) \
393 INIT_CALLS_LEVEL(2) \
394 @@ -670,21 +671,21 @@
396 #define CON_INITCALL \
397 VMLINUX_SYMBOL(__con_initcall_start) = .; \
398 - *(.con_initcall.init) \
399 + KEEP(*(.con_initcall.init)) \
400 VMLINUX_SYMBOL(__con_initcall_end) = .;
402 #define SECURITY_INITCALL \
403 VMLINUX_SYMBOL(__security_initcall_start) = .; \
404 - *(.security_initcall.init) \
405 + KEEP(*(.security_initcall.init)) \
406 VMLINUX_SYMBOL(__security_initcall_end) = .;
408 #ifdef CONFIG_BLK_DEV_INITRD
409 #define INIT_RAM_FS \
411 VMLINUX_SYMBOL(__initramfs_start) = .; \
413 + KEEP(*(.init.ramfs)) \
415 - *(.init.ramfs.info)
416 + KEEP(*(.init.ramfs.info))
420 --- a/arch/arm/Makefile
421 +++ b/arch/arm/Makefile
422 @@ -17,11 +17,16 @@ LDFLAGS_vmlinux :=-p --no-undefined -X
423 ifeq ($(CONFIG_CPU_ENDIAN_BE8),y)
424 LDFLAGS_vmlinux += --be8
426 +LDFLAGS_vmlinux += --gc-sections
428 OBJCOPYFLAGS :=-O binary -R .comment -S
430 #KBUILD_CFLAGS +=-pipe
432 +ifndef CONFIG_FUNCTION_TRACER
433 +KBUILD_CFLAGS_KERNEL += -ffunction-sections -fdata-sections
436 # Never generate .eh_frame
437 KBUILD_CFLAGS += $(call cc-option,-fno-dwarf2-cfi-asm)
439 --- a/arch/arm/kernel/vmlinux.lds.S
440 +++ b/arch/arm/kernel/vmlinux.lds.S
444 VMLINUX_SYMBOL(__proc_info_begin) = .; \
445 - *(.proc.info.init) \
446 + KEEP(*(.proc.info.init)) \
447 VMLINUX_SYMBOL(__proc_info_end) = .;
451 VMLINUX_SYMBOL(__idmap_text_start) = .; \
453 + KEEP(*(.idmap.text)) \
454 VMLINUX_SYMBOL(__idmap_text_end) = .; \
456 VMLINUX_SYMBOL(__hyp_idmap_text_start) = .; \
457 @@ -97,7 +97,7 @@ SECTIONS
458 .text : { /* Real text segment */
459 _stext = .; /* Text and read-only data */
460 __exception_text_start = .;
462 + KEEP(*(.exception.text))
463 __exception_text_end = .;
466 @@ -122,7 +122,7 @@ SECTIONS
467 __ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) {
468 __start___ex_table = .;
471 + KEEP(*(__ex_table))
473 __stop___ex_table = .;
475 @@ -134,12 +134,12 @@ SECTIONS
478 __start_unwind_idx = .;
480 + KEEP(*(.ARM.exidx*))
481 __stop_unwind_idx = .;
484 __start_unwind_tab = .;
486 + KEEP(*(.ARM.extab*))
487 __stop_unwind_tab = .;
490 @@ -158,14 +158,14 @@ SECTIONS
493 .vectors 0 : AT(__vectors_start) {
497 . = __vectors_start + SIZEOF(.vectors);
501 .stubs 0x1000 : AT(__stubs_start) {
505 . = __stubs_start + SIZEOF(.stubs);
507 @@ -179,24 +179,24 @@ SECTIONS
510 __arch_info_begin = .;
512 + KEEP(*(.arch.info.init))
516 __tagtable_begin = .;
518 + KEEP(*(.taglist.init))
521 #ifdef CONFIG_SMP_ON_UP
525 + KEEP(*(.alt.smp.init))
530 __pv_table_begin = .;
536 --- a/arch/arm/boot/compressed/Makefile
537 +++ b/arch/arm/boot/compressed/Makefile
538 @@ -123,6 +123,7 @@ ifeq ($(CONFIG_FUNCTION_TRACER),y)
539 ORIG_CFLAGS := $(KBUILD_CFLAGS)
540 KBUILD_CFLAGS = $(subst -pg, , $(ORIG_CFLAGS))
542 +KBUILD_CFLAGS_KERNEL := $(patsubst -f%-sections,,$(KBUILD_CFLAGS_KERNEL))
544 ccflags-y := -fpic -mno-single-pic-base -fno-builtin -I$(obj)
545 asflags-y := -DZIMAGE