1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
|
From e3d8676f5722b7622685581e06e8f53e6138e3ab Mon Sep 17 00:00:00 2001
From: Felix Fietkau <nbd@nbd.name>
Date: Sat, 15 Jul 2017 23:42:36 +0200
Subject: use -ffunction-sections, -fdata-sections and --gc-sections
In combination with kernel symbol export stripping this significantly reduces
the kernel image size. Used on both ARM and MIPS architectures.
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Jonas Gorski <jogo@openwrt.org>
Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
---
Makefile | 10 +++----
arch/arm/Kconfig | 1 +
arch/arm/boot/compressed/Makefile | 1 +
arch/arm/kernel/vmlinux.lds.S | 26 ++++++++--------
arch/mips/Kconfig | 1 +
arch/mips/kernel/vmlinux.lds.S | 4 +--
include/asm-generic/vmlinux.lds.h | 63 ++++++++++++++++++++-------------------
7 files changed, 55 insertions(+), 51 deletions(-)
--- a/Makefile
+++ b/Makefile
@@ -272,6 +272,11 @@ else
scripts/Kbuild.include: ;
include scripts/Kbuild.include
+ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
+KBUILD_CFLAGS_KERNEL += $(call cc-option,-ffunction-sections,)
+KBUILD_CFLAGS_KERNEL += $(call cc-option,-fdata-sections,)
+endif
+
# Read KERNELRELEASE from include/config/kernel.release (if it exists)
KERNELRELEASE = $(shell cat include/config/kernel.release 2> /dev/null)
KERNELVERSION = $(VERSION)$(if $(PATCHLEVEL),.$(PATCHLEVEL)$(if $(SUBLEVEL),.$(SUBLEVEL)))$(EXTRAVERSION)
@@ -787,11 +792,6 @@ ifdef CONFIG_DEBUG_SECTION_MISMATCH
KBUILD_CFLAGS += $(call cc-option, -fno-inline-functions-called-once)
endif
-ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
-KBUILD_CFLAGS += $(call cc-option,-ffunction-sections,)
-KBUILD_CFLAGS += $(call cc-option,-fdata-sections,)
-endif
-
# arch Makefile may override CC so keep this after arch Makefile is included
NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include)
CHECKFLAGS += $(NOSTDINC_FLAGS)
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -91,6 +91,7 @@ config ARM
select HAVE_UID16
select HAVE_VIRT_CPU_ACCOUNTING_GEN
select IRQ_FORCED_THREADING
+ select LD_DEAD_CODE_DATA_ELIMINATION
select MODULES_USE_ELF_REL
select NO_BOOTMEM
select OF_EARLY_FLATTREE if OF
--- a/arch/arm/boot/compressed/Makefile
+++ b/arch/arm/boot/compressed/Makefile
@@ -103,6 +103,7 @@ ifeq ($(CONFIG_FUNCTION_TRACER),y)
ORIG_CFLAGS := $(KBUILD_CFLAGS)
KBUILD_CFLAGS = $(subst -pg, , $(ORIG_CFLAGS))
endif
+KBUILD_CFLAGS_KERNEL := $(patsubst -f%-sections,,$(KBUILD_CFLAGS_KERNEL))
# -fstack-protector-strong triggers protection checks in this code,
# but it is being used too early to link to meaningful stack_chk logic.
--- a/arch/arm/kernel/vmlinux.lds.S
+++ b/arch/arm/kernel/vmlinux.lds.S
@@ -18,7 +18,7 @@
#define PROC_INFO \
. = ALIGN(4); \
VMLINUX_SYMBOL(__proc_info_begin) = .; \
- *(.proc.info.init) \
+ KEEP(*(.proc.info.init)) \
VMLINUX_SYMBOL(__proc_info_end) = .;
#define HYPERVISOR_TEXT \
@@ -29,11 +29,11 @@
#define IDMAP_TEXT \
ALIGN_FUNCTION(); \
VMLINUX_SYMBOL(__idmap_text_start) = .; \
- *(.idmap.text) \
+ KEEP(*(.idmap.text)) \
VMLINUX_SYMBOL(__idmap_text_end) = .; \
. = ALIGN(PAGE_SIZE); \
VMLINUX_SYMBOL(__hyp_idmap_text_start) = .; \
- *(.hyp.idmap.text) \
+ KEEP(*(.hyp.idmap.text)) \
VMLINUX_SYMBOL(__hyp_idmap_text_end) = .;
#ifdef CONFIG_HOTPLUG_CPU
@@ -106,7 +106,7 @@ SECTIONS
_stext = .; /* Text and read-only data */
IDMAP_TEXT
__exception_text_start = .;
- *(.exception.text)
+ KEEP(*(.exception.text))
__exception_text_end = .;
IRQENTRY_TEXT
SOFTIRQENTRY_TEXT
@@ -135,7 +135,7 @@ SECTIONS
__ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) {
__start___ex_table = .;
#ifdef CONFIG_MMU
- *(__ex_table)
+ KEEP(*(__ex_table))
#endif
__stop___ex_table = .;
}
@@ -147,12 +147,12 @@ SECTIONS
. = ALIGN(8);
.ARM.unwind_idx : {
__start_unwind_idx = .;
- *(.ARM.exidx*)
+ KEEP(*(.ARM.exidx*))
__stop_unwind_idx = .;
}
.ARM.unwind_tab : {
__start_unwind_tab = .;
- *(.ARM.extab*)
+ KEEP(*(.ARM.extab*))
__stop_unwind_tab = .;
}
#endif
@@ -172,14 +172,14 @@ SECTIONS
*/
__vectors_start = .;
.vectors 0xffff0000 : AT(__vectors_start) {
- *(.vectors)
+ KEEP(*(.vectors))
}
. = __vectors_start + SIZEOF(.vectors);
__vectors_end = .;
__stubs_start = .;
.stubs ADDR(.vectors) + 0x1000 : AT(__stubs_start) {
- *(.stubs)
+ KEEP(*(.stubs))
}
. = __stubs_start + SIZEOF(.stubs);
__stubs_end = .;
@@ -195,24 +195,24 @@ SECTIONS
}
.init.arch.info : {
__arch_info_begin = .;
- *(.arch.info.init)
+ KEEP(*(.arch.info.init))
__arch_info_end = .;
}
.init.tagtable : {
__tagtable_begin = .;
- *(.taglist.init)
+ KEEP(*(.taglist.init))
__tagtable_end = .;
}
#ifdef CONFIG_SMP_ON_UP
.init.smpalt : {
__smpalt_begin = .;
- *(.alt.smp.init)
+ KEEP(*(.alt.smp.init))
__smpalt_end = .;
}
#endif
.init.pv_table : {
__pv_table_begin = .;
- *(.pv_table)
+ KEEP(*(.pv_table))
__pv_table_end = .;
}
.init.data : {
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -40,6 +40,7 @@ config MIPS
select HAVE_CBPF_JIT if (!64BIT && !CPU_MICROMIPS)
select HAVE_EBPF_JIT if (64BIT && !CPU_MICROMIPS)
select HAVE_CC_STACKPROTECTOR
+ select LD_DEAD_CODE_DATA_ELIMINATION
select HAVE_CONTEXT_TRACKING
select HAVE_COPY_THREAD_TLS
select HAVE_C_RECORDMCOUNT
--- a/arch/mips/kernel/vmlinux.lds.S
+++ b/arch/mips/kernel/vmlinux.lds.S
@@ -72,7 +72,7 @@ SECTIONS
/* Exception table for data bus errors */
__dbe_table : {
__start___dbe_table = .;
- *(__dbe_table)
+ KEEP(*(__dbe_table))
__stop___dbe_table = .;
}
@@ -123,7 +123,7 @@ SECTIONS
. = ALIGN(4);
.mips.machines.init : AT(ADDR(.mips.machines.init) - LOAD_OFFSET) {
__mips_machines_start = .;
- *(.mips.machines.init)
+ KEEP(*(.mips.machines.init))
__mips_machines_end = .;
}
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -105,7 +105,7 @@
#ifdef CONFIG_FTRACE_MCOUNT_RECORD
#define MCOUNT_REC() . = ALIGN(8); \
VMLINUX_SYMBOL(__start_mcount_loc) = .; \
- *(__mcount_loc) \
+ KEEP(*(__mcount_loc)) \
VMLINUX_SYMBOL(__stop_mcount_loc) = .;
#else
#define MCOUNT_REC()
@@ -113,7 +113,7 @@
#ifdef CONFIG_TRACE_BRANCH_PROFILING
#define LIKELY_PROFILE() VMLINUX_SYMBOL(__start_annotated_branch_profile) = .; \
- *(_ftrace_annotated_branch) \
+ KEEP(*(_ftrace_annotated_branch)) \
VMLINUX_SYMBOL(__stop_annotated_branch_profile) = .;
#else
#define LIKELY_PROFILE()
@@ -121,7 +121,7 @@
#ifdef CONFIG_PROFILE_ALL_BRANCHES
#define BRANCH_PROFILE() VMLINUX_SYMBOL(__start_branch_profile) = .; \
- *(_ftrace_branch) \
+ KEEP(*(_ftrace_branch)) \
VMLINUX_SYMBOL(__stop_branch_profile) = .;
#else
#define BRANCH_PROFILE()
@@ -237,7 +237,8 @@
LIKELY_PROFILE() \
BRANCH_PROFILE() \
TRACE_PRINTKS() \
- TRACEPOINT_STR()
+ TRACEPOINT_STR() \
+ *(.data.[a-zA-Z_]*)
/*
* Data section helpers
@@ -496,7 +497,7 @@
#define ENTRY_TEXT \
ALIGN_FUNCTION(); \
VMLINUX_SYMBOL(__entry_text_start) = .; \
- *(.entry.text) \
+ KEEP(*(.entry.text)) \
VMLINUX_SYMBOL(__entry_text_end) = .;
#define IRQENTRY_TEXT \
@@ -603,7 +604,7 @@
. = ALIGN(sbss_align); \
.sbss : AT(ADDR(.sbss) - LOAD_OFFSET) { \
*(.dynsbss) \
- *(.sbss) \
+ *(.sbss .sbss.*) \
*(.scommon) \
}
|
