Re: [PATCH 3/4] s390: enable text relative kallsyms for 64-bit targets
From: Ard Biesheuvel
Date: Wed Jan 20 2016 - 05:19:03 EST
On 20 January 2016 at 11:17, Heiko Carstens <heiko.carstens@xxxxxxxxxx> 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@xxxxxxxxxx> 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@xxxxxxxxxx>
>> >> ---
>> >> 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@xxxxxxxxxx>
>> 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!