Re: [PATCH] sh: define RUNTIME_DISCARD_EXIT

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

On Tue, Jan 24, 2023 at 09:09:26AM +0100, John Paul Adrian Glaubitz wrote:
> Hi Tom!
> 
> On 1/24/23 01:09, 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").
> 
> Works for me with binutils 2.36.1.

Thank you for confirming!

> 
> > 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>
> 
> I'm in favor of including this patch for the said reasons.
> 
> > 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/
> 
> We're currently busy trying to save arch/sh.

In that case, glad I sent this.

> 
> Thanks,
> Adrian
> 
> -- 
>  .''`.  John Paul Adrian Glaubitz
> : :' :  Debian Developer
> `. `'   Physicist
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