Re: [PATCH 04/11] s390: vmlinux.lds.S: Discard unnecessary sections

Nathan Chancellor
2024-02-13T00:15:50Z

On Mon, Feb 12, 2024 at 02:55:11PM +0100, Heiko Carstens wrote:
> On Wed, Feb 07, 2024 at 05:14:56PM -0700, Nathan Chancellor wrote:
> > When building with CONFIG_LD_ORPHAN_WARN after selecting
> > CONFIG_ARCH_HAS_LD_ORPHAN_WARN, there are some warnings around certain
> > ELF sections that are unnecessary for the kernel's purposes.
> >
> > s390-linux-ld: warning: orphan section `.dynstr' from `arch/s390/kernel/head64.o' being placed in section `.dynstr'
> > s390-linux-ld: warning: orphan section `.dynamic' from `arch/s390/kernel/head64.o' being placed in section `.dynamic'
> > s390-linux-ld: warning: orphan section `.hash' from `arch/s390/kernel/head64.o' being placed in section `.hash'
> > s390-linux-ld: warning: orphan section `.gnu.hash' from `arch/s390/kernel/head64.o' being placed in section `.gnu.hash'
> >
> > Add them to the discards to clear up the warnings, which matches other
> > architectures.
> >
> > Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> > ---
> > arch/s390/kernel/vmlinux.lds.S | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> ...
> > - *(.interp)
> > + *(.interp .dynamic)
> > + *(.dynstr .hash .gnu.hash)
>
> This seems to be wrong, since it leads to 1000s of error messages when
> using the "crash" utility e.g. when looking into a live dump of system
> with the generated debug info:
>
> BFD: /usr/lib/debug/usr/lib/modules/6.8.0-20240211.rc3.git0.bdca9b8dcf3f.300.fc39.s390x/vmlinux: attempt to load strings from a non-string section (number 0)
>
> I will change this commit to the below; it seems to work and is in
> line with other architectures:

Thanks a lot for catching that, your final change seems good to me.
Here's to hoping I did not get anything else wrong :)

Cheers,
Nathan

> -----
>
> When building with CONFIG_LD_ORPHAN_WARN after selecting
> CONFIG_ARCH_HAS_LD_ORPHAN_WARN, there are some warnings around certain
> ELF sections:
>
> s390-linux-ld: warning: orphan section `.dynstr' from `arch/s390/kernel/head64.o' being placed in section `.dynstr'
> s390-linux-ld: warning: orphan section `.dynamic' from `arch/s390/kernel/head64.o' being placed in section `.dynamic'
> s390-linux-ld: warning: orphan section `.hash' from `arch/s390/kernel/head64.o' being placed in section `.hash'
> s390-linux-ld: warning: orphan section `.gnu.hash' from `arch/s390/kernel/head64.o' being placed in section `.gnu.hash'
>
> Explicitly keep those sections like other architectures when
> CONFIG_RELOCATABLE is enabled, which is always true for s390.
>
> [hca@linux.ibm.com: keep sections instead of discarding]
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> Link: https://lore.kernel.org/r/20240207-s390-lld-and-orphan-warn-v1-4-8a665b3346ab@kernel.org
> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
> ---
> arch/s390/kernel/vmlinux.lds.S | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
> diff --git a/arch/s390/kernel/vmlinux.lds.S b/arch/s390/kernel/vmlinux.lds.S
> index 661a487a3048..d46e3c383952 100644
> --- a/arch/s390/kernel/vmlinux.lds.S
> +++ b/arch/s390/kernel/vmlinux.lds.S
> @@ -200,6 +200,21 @@ SECTIONS
> *(.rela*)
> __rela_dyn_end = .;
> }
> + .dynamic ALIGN(8) : {
> + *(.dynamic)
> + }
> + .dynsym ALIGN(8) : {
> + *(.dynsym)
> + }
> + .dynstr ALIGN(8) : {
> + *(.dynstr)
> + }
> + .hash ALIGN(8) : {
> + *(.hash)
> + }
> + .gnu.hash ALIGN(8) : {
> + *(.gnu.hash)
> + }
>
> . = ALIGN(PAGE_SIZE);
> __init_end = .; /* freed after init ends here */
> --
> 2.40.1
>