| Message ID | 1453280738-18721-4-git-send-email-ard.biesheuvel@linaro.org |
|---|---|
| State | New |
| Headers | show |
On 20 January 2016 at 10:43, Heiko Carstens <heiko.carstens@de.ibm.com> wrote: > On Wed, Jan 20, 2016 at 10:05:37AM +0100, Ard Biesheuvel wrote: >> 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@linaro.org> >> --- >> >> 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 > > Please remove the "if 64BIT" since s390 is always 64BIT in the meantime. > Tested on s390 and everything seems still to work ;) > > Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com> > Thanks! Did you take a look at /proc/kallsyms, by any chance? It should look identical with and without these patches
On 20 January 2016 at 11:17, Heiko Carstens <heiko.carstens@de.ibm.com> wrote: > On Wed, Jan 20, 2016 at 11:04:24AM +0100, Ard Biesheuvel wrote: >> On 20 January 2016 at 10:43, Heiko Carstens <heiko.carstens@de.ibm.com> wrote: >> > On Wed, Jan 20, 2016 at 10:05:37AM +0100, Ard Biesheuvel wrote: >> >> 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@linaro.org> >> >> --- >> >> >> >> 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 >> > >> > Please remove the "if 64BIT" since s390 is always 64BIT in the meantime. >> > Tested on s390 and everything seems still to work ;) >> > >> > Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com> >> > >> >> Thanks! Did you take a look at /proc/kallsyms, by any chance? It >> should look identical with and without these patches > > Close to identical, since the generated code and offsets change a bit with > your new config option enabled and disabled. But only those parts that are > linked behind kernel/kallsyms.c. > > However I did run a couple of ftrace, kprobes tests and enforced call > backtraces. Everything still works. > > So it looks all good. > Thanks a lot!
=======
$ 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
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@linaro.org> --- BEFORE: -- 2.5.0