Re: [PATCH] sh: define RUNTIME_DISCARD_EXIT

[Tom Saeger <tom.saeger@oracle.com>]

On Mon, Jan 23, 2023 at 05:09:35PM -0700, Tom Saeger wrote:
> sh vmlinux fails to link with GNU ld < 2.40 (likely < 2.36) since
> commit 99cb0d917ffa ("arch: fix broken BuildID for arm64 and riscv").
> 
> This is similar to fixes for powerpc and s390:
> commit 4b9880dbf3bd ("powerpc/vmlinux.lds: Define RUNTIME_DISCARD_EXIT").
> commit a494398bde27 ("s390: define RUNTIME_DISCARD_EXIT to fix link error
> with GNU ld < 2.36").
> 
>   $ sh4-linux-gnu-ld --version | head -n1
>   GNU ld (GNU Binutils for Debian) 2.35.2
> 
>   $ make ARCH=sh CROSS_COMPILE=sh4-linux-gnu- microdev_defconfig
>   $ make ARCH=sh CROSS_COMPILE=sh4-linux-gnu-
> 
>   `.exit.text' referenced in section `__bug_table' of crypto/algboss.o:
>   defined in discarded section `.exit.text' of crypto/algboss.o
>   `.exit.text' referenced in section `__bug_table' of
>   drivers/char/hw_random/core.o: defined in discarded section
>   `.exit.text' of drivers/char/hw_random/core.o
>   make[2]: *** [scripts/Makefile.vmlinux:34: vmlinux] Error 1
>   make[1]: *** [Makefile:1252: vmlinux] Error 2
> 
> arch/sh/kernel/vmlinux.lds.S keeps EXIT_TEXT:
> 
> 	/*
> 	 * .exit.text is discarded at runtime, not link time, to deal with
> 	 * references from __bug_table
> 	 */
> 	.exit.text : AT(ADDR(.exit.text)) { EXIT_TEXT }
> 
> However, EXIT_TEXT is thrown away by
> DISCARD(include/asm-generic/vmlinux.lds.h) because
> sh does not define RUNTIME_DISCARD_EXIT.
> 
> GNU ld 2.40 does not have this issue and builds fine.
> This corresponds with Masahiro's comments in a494398bde27:
> "Nathan [Chancellor] also found that binutils
> commit 21401fc7bf67 ("Duplicate output sections in scripts") cured this
> issue, so we cannot reproduce it with binutils 2.36+, but it is better
> to not rely on it."
> 
> Fixes: 99cb0d917ffa ("arch: fix broken BuildID for arm64 and riscv")
> Link: https://lore.kernel.org/all/Y7Jal56f6UBh1abE@dev-arch.thelio-3990X/
> Link: https://lore.kernel.org/all/20230123194218.47ssfzhrpnv3xfez@oracle.com/
> Signed-off-by: Tom Saeger <tom.saeger@oracle.com>
> ---
> 
> This may be moot given sh might be soon removed:
> https://lore.kernel.org/all/20230113062339.1909087-1-hch@lst.de/#t
> 
> However this did come up here:
> https://lore.kernel.org/all/20230123194218.47ssfzhrpnv3xfez@oracle.com/

Andrew,
  Adrian suggested I ask if you can pick this up in your tree, while the
  arch/sh maintainership gets figured out:

  https://lore.kernel.org/all/8981c636-6145-6589-d4c9-8cdc12801be3@physik.fu-berlin.de/

  This is needed in stable 5.4, 5.10, and 5.15 as well.

> 
> 
> Regards,
> 
> --Tom
> 
> 
>  arch/sh/kernel/vmlinux.lds.S | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/sh/kernel/vmlinux.lds.S b/arch/sh/kernel/vmlinux.lds.S
> index 3161b9ccd2a5..b6276a3521d7 100644
> --- a/arch/sh/kernel/vmlinux.lds.S
> +++ b/arch/sh/kernel/vmlinux.lds.S
> @@ -4,6 +4,7 @@
>   * Written by Niibe Yutaka and Paul Mundt
>   */
>  OUTPUT_ARCH(sh)
> +#define RUNTIME_DISCARD_EXIT
>  #include <asm/thread_info.h>
>  #include <asm/cache.h>
>  #include <asm/vmlinux.lds.h>
> 
> base-commit: 2475bf0250dee99b477e0c56d7dc9d7ac3f04117
> -- 
> 2.39.1
>