OpenWrt – Blame information for rev 1

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Rev Author Line No. Line
1 office 1 From e3d8676f5722b7622685581e06e8f53e6138e3ab Mon Sep 17 00:00:00 2001
2 From: Felix Fietkau <nbd@nbd.name>
3 Date: Sat, 15 Jul 2017 23:42:36 +0200
4 Subject: use -ffunction-sections, -fdata-sections and --gc-sections
5  
6 In combination with kernel symbol export stripping this significantly reduces
7 the kernel image size. Used on both ARM and MIPS architectures.
8  
9 Signed-off-by: Felix Fietkau <nbd@nbd.name>
10 Signed-off-by: Jonas Gorski <jogo@openwrt.org>
11 Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
12 ---
13 Makefile | 10 +++----
14 arch/arm/Kconfig | 1 +
15 arch/arm/boot/compressed/Makefile | 1 +
16 arch/arm/kernel/vmlinux.lds.S | 26 ++++++++--------
17 arch/mips/Kconfig | 1 +
18 arch/mips/kernel/vmlinux.lds.S | 4 +--
19 include/asm-generic/vmlinux.lds.h | 63 ++++++++++++++++++++-------------------
20 7 files changed, 55 insertions(+), 51 deletions(-)
21  
22 --- a/Makefile
23 +++ b/Makefile
24 @@ -294,6 +294,11 @@ else
25 scripts/Kbuild.include: ;
26 include scripts/Kbuild.include
27  
28 +ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
29 +KBUILD_CFLAGS_KERNEL += -ffunction-sections -fdata-sections
30 +LDFLAGS_vmlinux += --gc-sections
31 +endif
32 +
33 # Read KERNELRELEASE from include/config/kernel.release (if it exists)
34 KERNELRELEASE = $(shell cat include/config/kernel.release 2> /dev/null)
35 KERNELVERSION = $(VERSION)$(if $(PATCHLEVEL),.$(PATCHLEVEL)$(if $(SUBLEVEL),.$(SUBLEVEL)))$(EXTRAVERSION)
36 @@ -785,11 +790,6 @@ ifdef CONFIG_DEBUG_SECTION_MISMATCH
37 KBUILD_CFLAGS += $(call cc-option, -fno-inline-functions-called-once)
38 endif
39  
40 -ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
41 -KBUILD_CFLAGS_KERNEL += -ffunction-sections -fdata-sections
42 -LDFLAGS_vmlinux += --gc-sections
43 -endif
44 -
45 # arch Makefile may override CC so keep this after arch Makefile is included
46 NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include)
47  
48 --- a/arch/arm/Kconfig
49 +++ b/arch/arm/Kconfig
50 @@ -98,6 +98,7 @@ config ARM
51 select HAVE_UID16
52 select HAVE_VIRT_CPU_ACCOUNTING_GEN
53 select IRQ_FORCED_THREADING
54 + select HAVE_LD_DEAD_CODE_DATA_ELIMINATION
55 select MODULES_USE_ELF_REL
56 select NEED_DMA_MAP_STATE
57 select NO_BOOTMEM
58 --- a/arch/arm/boot/compressed/Makefile
59 +++ b/arch/arm/boot/compressed/Makefile
60 @@ -106,6 +106,7 @@ ifeq ($(CONFIG_FUNCTION_TRACER),y)
61 ORIG_CFLAGS := $(KBUILD_CFLAGS)
62 KBUILD_CFLAGS = $(subst -pg, , $(ORIG_CFLAGS))
63 endif
64 +KBUILD_CFLAGS_KERNEL := $(patsubst -f%-sections,,$(KBUILD_CFLAGS_KERNEL))
65  
66 # -fstack-protector-strong triggers protection checks in this code,
67 # but it is being used too early to link to meaningful stack_chk logic.
68 --- a/arch/arm/kernel/vmlinux.lds.S
69 +++ b/arch/arm/kernel/vmlinux.lds.S
70 @@ -100,24 +100,24 @@ SECTIONS
71 }
72 .init.arch.info : {
73 __arch_info_begin = .;
74 - *(.arch.info.init)
75 + KEEP(*(.arch.info.init))
76 __arch_info_end = .;
77 }
78 .init.tagtable : {
79 __tagtable_begin = .;
80 - *(.taglist.init)
81 + KEEP(*(.taglist.init))
82 __tagtable_end = .;
83 }
84 #ifdef CONFIG_SMP_ON_UP
85 .init.smpalt : {
86 __smpalt_begin = .;
87 - *(.alt.smp.init)
88 + KEEP(*(.alt.smp.init))
89 __smpalt_end = .;
90 }
91 #endif
92 .init.pv_table : {
93 __pv_table_begin = .;
94 - *(.pv_table)
95 + KEEP(*(.pv_table))
96 __pv_table_end = .;
97 }
98  
99 --- a/arch/arm/kernel/vmlinux.lds.h
100 +++ b/arch/arm/kernel/vmlinux.lds.h
101 @@ -22,13 +22,13 @@
102 #define ARM_MMU_DISCARD(x)
103 #else
104 #define ARM_MMU_KEEP(x)
105 -#define ARM_MMU_DISCARD(x) x
106 +#define ARM_MMU_DISCARD(x) KEEP(x)
107 #endif
108  
109 #define PROC_INFO \
110 . = ALIGN(4); \
111 __proc_info_begin = .; \
112 - *(.proc.info.init) \
113 + KEEP(*(.proc.info.init)) \
114 __proc_info_end = .;
115  
116 #define HYPERVISOR_TEXT \
117 @@ -39,11 +39,11 @@
118 #define IDMAP_TEXT \
119 ALIGN_FUNCTION(); \
120 __idmap_text_start = .; \
121 - *(.idmap.text) \
122 + KEEP(*(.idmap.text)) \
123 __idmap_text_end = .; \
124 . = ALIGN(PAGE_SIZE); \
125 __hyp_idmap_text_start = .; \
126 - *(.hyp.idmap.text) \
127 + KEEP(*(.hyp.idmap.text)) \
128 __hyp_idmap_text_end = .;
129  
130 #define ARM_DISCARD \
131 @@ -86,12 +86,12 @@
132 . = ALIGN(8); \
133 .ARM.unwind_idx : { \
134 __start_unwind_idx = .; \
135 - *(.ARM.exidx*) \
136 + KEEP(*(.ARM.exidx*)) \
137 __stop_unwind_idx = .; \
138 } \
139 .ARM.unwind_tab : { \
140 __start_unwind_tab = .; \
141 - *(.ARM.extab*) \
142 + KEEP(*(.ARM.extab*)) \
143 __stop_unwind_tab = .; \
144 }
145  
146 @@ -102,14 +102,14 @@
147 #define ARM_VECTORS \
148 __vectors_start = .; \
149 .vectors 0xffff0000 : AT(__vectors_start) { \
150 - *(.vectors) \
151 + KEEP(*(.vectors)) \
152 } \
153 . = __vectors_start + SIZEOF(.vectors); \
154 __vectors_end = .; \
155 \
156 __stubs_start = .; \
157 .stubs ADDR(.vectors) + 0x1000 : AT(__stubs_start) { \
158 - *(.stubs) \
159 + KEEP(*(.stubs)) \
160 } \
161 . = __stubs_start + SIZEOF(.stubs); \
162 __stubs_end = .; \
163 --- a/arch/mips/Kconfig
164 +++ b/arch/mips/Kconfig
165 @@ -43,6 +43,7 @@ config MIPS
166 select HAVE_ARCH_TRANSPARENT_HUGEPAGE if CPU_SUPPORTS_HUGEPAGES && 64BIT
167 select HAVE_CBPF_JIT if (!64BIT && !CPU_MICROMIPS)
168 select HAVE_EBPF_JIT if (64BIT && !CPU_MICROMIPS)
169 + select HAVE_LD_DEAD_CODE_DATA_ELIMINATION
170 select HAVE_CONTEXT_TRACKING
171 select HAVE_COPY_THREAD_TLS
172 select HAVE_C_RECORDMCOUNT
173 --- a/arch/mips/kernel/vmlinux.lds.S
174 +++ b/arch/mips/kernel/vmlinux.lds.S
175 @@ -72,7 +72,7 @@ SECTIONS
176 /* Exception table for data bus errors */
177 __dbe_table : {
178 __start___dbe_table = .;
179 - *(__dbe_table)
180 + KEEP(*(__dbe_table))
181 __stop___dbe_table = .;
182 }
183  
184 @@ -123,7 +123,7 @@ SECTIONS
185 . = ALIGN(4);
186 .mips.machines.init : AT(ADDR(.mips.machines.init) - LOAD_OFFSET) {
187 __mips_machines_start = .;
188 - *(.mips.machines.init)
189 + KEEP(*(.mips.machines.init))
190 __mips_machines_end = .;
191 }
192