This enables the newly introduced text-relative kallsyms support when
building 64-bit targets. This cuts the size of the kallsyms address
table in half, reducing the memory footprint of the kernel .rodata
section by about 250 KB for a defconfig build.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
---
BEFORE:
=======
$ size vmlinux
text data bss dec hex filename
12329586 3107008 14727792 30164386 1cc45a2 vmlinux
$ readelf -S .tmp_kallsyms2.o
There are 9 section headers, starting at offset 0x125b50:
Section Headers:
[Nr] Name Type Address Offset
Size EntSize Flags Link Info Align
...
[ 4] .rodata PROGBITS 0000000000000000 00000040
0000000000125ad0 0000000000000000 A 0 0 8
[ 5] .rela.rodata RELA 0000000000000000 00125f28
000000000015ead8 0000000000000018 7 4 8
[ 6] .shstrtab STRTAB 0000000000000000 00125b10
0000000000000039 0000000000000000 0 0 1
...
$ ls -l arch/s390/boot/bzImage
-rwxrwxr-x 1 ard ard 5234224 Jan 20 08:22 arch/s390/boot/bzImage
AFTER:
======
$ size vmlinux
text data bss dec hex filename
12088114 3102912 14727792 29918818 1c88662 vmlinux
$ readelf -S .tmp_kallsyms2.o
There are 8 section headers, starting at offset 0xeb428:
Section Headers:
[Nr] Name Type Address Offset
...
[ 4] .rodata PROGBITS 0000000000000000 00000040
00000000000eb3b0 0000000000000000 A 0 0 8
[ 5] .shstrtab STRTAB 0000000000000000 000eb3f0
0000000000000034 0000000000000000 0 0 1
...
$ ls -l arch/s390/boot/bzImage
-rwxrwxr-x 1 ard ard 5224256 Jan 20 08:23 arch/s390/boot/bzImage
---
arch/s390/Kconfig | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index dbeeb3a049f2..588160fd1db0 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -149,6 +149,7 @@ config S390
select HAVE_REGS_AND_STACK_ACCESS_API
select HAVE_SYSCALL_TRACEPOINTS
select HAVE_VIRT_CPU_ACCOUNTING
+ select KALLSYMS_TEXT_RELATIVE if 64BIT
select MODULES_USE_ELF_RELA
select NO_BOOTMEM
select OLD_SIGACTION
--
2.5.0
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