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

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Date: Mon, 12 Feb 2024 14:55:11 +0100
From: Heiko Carstens <hca@...ux.ibm.com>
To: Nathan Chancellor <nathan@...nel.org>
Cc: gor@...ux.ibm.com, agordeev@...ux.ibm.com, borntraeger@...ux.ibm.com,
        svens@...ux.ibm.com, maskray@...gle.com, ndesaulniers@...gle.com,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, patches@...ts.linux.dev
Subject: Re: [PATCH 04/11] s390: vmlinux.lds.S: Discard unnecessary sections

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@...nel.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@...ux.ibm.com: keep sections instead of discarding]
Signed-off-by: Nathan Chancellor <nathan@...nel.org>
Link: https://lore.kernel.org/r/20240207-s390-lld-and-orphan-warn-v1-4-8a665b3346ab@kernel.org
Signed-off-by: Heiko Carstens <hca@...ux.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