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authorNicholas Piggin <npiggin@gmail.com>2016-08-24 15:29:20 +0300
committerMichal Marek <mmarek@suse.com>2016-09-09 11:47:00 +0300
commitb67067f1176df6ee727450546b58704e4b588563 (patch)
tree59cfd4ebc0ea13e799b9e4393740591f9e16985d /include/asm-generic
parenta5967db9af51a84f5e181600954714a9e4c69f1f (diff)
downloadlinux-b67067f1176df6ee727450546b58704e4b588563.tar.xz
kbuild: allow archs to select link dead code/data elimination
Introduce LD_DEAD_CODE_DATA_ELIMINATION option for architectures to select to build with -ffunction-sections, -fdata-sections, and link with --gc-sections. It requires some work (documented) to ensure all unreferenced entrypoints are live, and requires toolchain and build verification, so it is made a per-arch option for now. On a random powerpc64le build, this yelds a significant size saving, it boots and runs fine, but there is a lot I haven't tested as yet, so these savings may be reduced if there are bugs in the link. text data bss dec filename 11169741 1180744 1923176 14273661 vmlinux 10445269 1004127 1919707 13369103 vmlinux.dce ~700K text, ~170K data, 6% removed from kernel image size. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michal Marek <mmarek@suse.com>
Diffstat (limited to 'include/asm-generic')
-rw-r--r--include/asm-generic/vmlinux.lds.h52
1 files changed, 29 insertions, 23 deletions
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 24563970ff7b..ad9d8f94dc7a 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -196,9 +196,14 @@
*(.dtb.init.rodata) \
VMLINUX_SYMBOL(__dtb_end) = .;
-/* .data section */
+/*
+ * .data section
+ * -fdata-sections generates .data.identifier which needs to be pulled in
+ * with .data, but don't want to pull in .data..stuff which has its own
+ * requirements. Same for bss.
+ */
#define DATA_DATA \
- *(.data) \
+ *(.data .data.[0-9a-zA-Z_]*) \
*(.ref.data) \
*(.data..shared_aligned) /* percpu related */ \
MEM_KEEP(init.data) \
@@ -320,76 +325,76 @@
/* Kernel symbol table: Normal symbols */ \
__ksymtab : AT(ADDR(__ksymtab) - LOAD_OFFSET) { \
VMLINUX_SYMBOL(__start___ksymtab) = .; \
- *(SORT(___ksymtab+*)) \
+ KEEP(*(SORT(___ksymtab+*))) \
VMLINUX_SYMBOL(__stop___ksymtab) = .; \
} \
\
/* Kernel symbol table: GPL-only symbols */ \
__ksymtab_gpl : AT(ADDR(__ksymtab_gpl) - LOAD_OFFSET) { \
VMLINUX_SYMBOL(__start___ksymtab_gpl) = .; \
- *(SORT(___ksymtab_gpl+*)) \
+ KEEP(*(SORT(___ksymtab_gpl+*))) \
VMLINUX_SYMBOL(__stop___ksymtab_gpl) = .; \
} \
\
/* Kernel symbol table: Normal unused symbols */ \
__ksymtab_unused : AT(ADDR(__ksymtab_unused) - LOAD_OFFSET) { \
VMLINUX_SYMBOL(__start___ksymtab_unused) = .; \
- *(SORT(___ksymtab_unused+*)) \
+ KEEP(*(SORT(___ksymtab_unused+*))) \
VMLINUX_SYMBOL(__stop___ksymtab_unused) = .; \
} \
\
/* Kernel symbol table: GPL-only unused symbols */ \
__ksymtab_unused_gpl : AT(ADDR(__ksymtab_unused_gpl) - LOAD_OFFSET) { \
VMLINUX_SYMBOL(__start___ksymtab_unused_gpl) = .; \
- *(SORT(___ksymtab_unused_gpl+*)) \
+ KEEP(*(SORT(___ksymtab_unused_gpl+*))) \
VMLINUX_SYMBOL(__stop___ksymtab_unused_gpl) = .; \
} \
\
/* Kernel symbol table: GPL-future-only symbols */ \
__ksymtab_gpl_future : AT(ADDR(__ksymtab_gpl_future) - LOAD_OFFSET) { \
VMLINUX_SYMBOL(__start___ksymtab_gpl_future) = .; \
- *(SORT(___ksymtab_gpl_future+*)) \
+ KEEP(*(SORT(___ksymtab_gpl_future+*))) \
VMLINUX_SYMBOL(__stop___ksymtab_gpl_future) = .; \
} \
\
/* Kernel symbol table: Normal symbols */ \
__kcrctab : AT(ADDR(__kcrctab) - LOAD_OFFSET) { \
VMLINUX_SYMBOL(__start___kcrctab) = .; \
- *(SORT(___kcrctab+*)) \
+ KEEP(*(SORT(___kcrctab+*))) \
VMLINUX_SYMBOL(__stop___kcrctab) = .; \
} \
\
/* Kernel symbol table: GPL-only symbols */ \
__kcrctab_gpl : AT(ADDR(__kcrctab_gpl) - LOAD_OFFSET) { \
VMLINUX_SYMBOL(__start___kcrctab_gpl) = .; \
- *(SORT(___kcrctab_gpl+*)) \
+ KEEP(*(SORT(___kcrctab_gpl+*))) \
VMLINUX_SYMBOL(__stop___kcrctab_gpl) = .; \
} \
\
/* Kernel symbol table: Normal unused symbols */ \
__kcrctab_unused : AT(ADDR(__kcrctab_unused) - LOAD_OFFSET) { \
VMLINUX_SYMBOL(__start___kcrctab_unused) = .; \
- *(SORT(___kcrctab_unused+*)) \
+ KEEP(*(SORT(___kcrctab_unused+*))) \
VMLINUX_SYMBOL(__stop___kcrctab_unused) = .; \
} \
\
/* Kernel symbol table: GPL-only unused symbols */ \
__kcrctab_unused_gpl : AT(ADDR(__kcrctab_unused_gpl) - LOAD_OFFSET) { \
VMLINUX_SYMBOL(__start___kcrctab_unused_gpl) = .; \
- *(SORT(___kcrctab_unused_gpl+*)) \
+ KEEP(*(SORT(___kcrctab_unused_gpl+*))) \
VMLINUX_SYMBOL(__stop___kcrctab_unused_gpl) = .; \
} \
\
/* Kernel symbol table: GPL-future-only symbols */ \
__kcrctab_gpl_future : AT(ADDR(__kcrctab_gpl_future) - LOAD_OFFSET) { \
VMLINUX_SYMBOL(__start___kcrctab_gpl_future) = .; \
- *(SORT(___kcrctab_gpl_future+*)) \
+ KEEP(*(SORT(___kcrctab_gpl_future+*))) \
VMLINUX_SYMBOL(__stop___kcrctab_gpl_future) = .; \
} \
\
/* Kernel symbol table: strings */ \
__ksymtab_strings : AT(ADDR(__ksymtab_strings) - LOAD_OFFSET) { \
- *(__ksymtab_strings) \
+ KEEP(*(__ksymtab_strings)) \
} \
\
/* __*init sections */ \
@@ -424,7 +429,7 @@
#define SECURITY_INIT \
.security_initcall.init : AT(ADDR(.security_initcall.init) - LOAD_OFFSET) { \
VMLINUX_SYMBOL(__security_initcall_start) = .; \
- *(.security_initcall.init) \
+ KEEP(*(.security_initcall.init)) \
VMLINUX_SYMBOL(__security_initcall_end) = .; \
}
@@ -432,7 +437,7 @@
* during second ld run in second ld pass when generating System.map */
#define TEXT_TEXT \
ALIGN_FUNCTION(); \
- *(.text.hot .text .text.fixup .text.unlikely) \
+ *(.text.hot .text .text.fixup .text.unlikely .text.*) \
*(.ref.text) \
MEM_KEEP(init.text) \
MEM_KEEP(exit.text) \
@@ -527,6 +532,7 @@
/* init and exit section handling */
#define INIT_DATA \
+ KEEP(*(SORT(___kentry+*))) \
*(.init.data) \
MEM_DISCARD(init.data) \
KERNEL_CTORS() \
@@ -593,7 +599,7 @@
BSS_FIRST_SECTIONS \
*(.bss..page_aligned) \
*(.dynbss) \
- *(.bss) \
+ *(.bss .bss.[0-9a-zA-Z_]*) \
*(COMMON) \
}
@@ -676,12 +682,12 @@
#define INIT_CALLS_LEVEL(level) \
VMLINUX_SYMBOL(__initcall##level##_start) = .; \
- *(.initcall##level##.init) \
- *(.initcall##level##s.init) \
+ KEEP(*(.initcall##level##.init)) \
+ KEEP(*(.initcall##level##s.init)) \
#define INIT_CALLS \
VMLINUX_SYMBOL(__initcall_start) = .; \
- *(.initcallearly.init) \
+ KEEP(*(.initcallearly.init)) \
INIT_CALLS_LEVEL(0) \
INIT_CALLS_LEVEL(1) \
INIT_CALLS_LEVEL(2) \
@@ -695,21 +701,21 @@
#define CON_INITCALL \
VMLINUX_SYMBOL(__con_initcall_start) = .; \
- *(.con_initcall.init) \
+ KEEP(*(.con_initcall.init)) \
VMLINUX_SYMBOL(__con_initcall_end) = .;
#define SECURITY_INITCALL \
VMLINUX_SYMBOL(__security_initcall_start) = .; \
- *(.security_initcall.init) \
+ KEEP(*(.security_initcall.init)) \
VMLINUX_SYMBOL(__security_initcall_end) = .;
#ifdef CONFIG_BLK_DEV_INITRD
#define INIT_RAM_FS \
. = ALIGN(4); \
VMLINUX_SYMBOL(__initramfs_start) = .; \
- *(.init.ramfs) \
+ KEEP(*(.init.ramfs)) \
. = ALIGN(8); \
- *(.init.ramfs.info)
+ KEEP(*(.init.ramfs.info))
#else
#define INIT_RAM_FS
#endif