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

Heiko Carstens
2024-02-12T13:55:23Z

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:

-----

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