Re: [RESEND PATCH v1 1/1] s390/kexec: Make KEXEC_SIG available when CONFIG_MODULES=n

[Heiko Carstens <hca@linux.ibm.com>]

On Tue, Feb 10, 2026 at 10:23:01AM +0800, Baoquan He wrote:
> On 02/09/26 at 02:33pm, Alexander Egorenkov wrote:
> > The commit c8424e776b09 ("MODSIGN: Export module signature definitions")
> > replaced the dependency of KEXEC_SIG on SYSTEM_DATA_VERIFICATION with
> > the dependency on MODULE_SIG_FORMAT. This change disables KEXEC_SIG
> > in s390 kernels built with MODULES=n if nothing else selects
> > MODULE_SIG_FORMAT.
> > 
> > Furthermore, the signature verification in s390 kexec does not require
> > MODULE_SIG_FORMAT because it requires only the struct module_signature and,
> > therefore, does not depend on code in kernel/module_signature.c.
> > 
> > But making ARCH_SUPPORTS_KEXEC_SIG depend on SYSTEM_DATA_VERIFICATION
> > is also incorrect because it makes KEXEC_SIG available on s390 only
> > if some other arbitrary option (for instance a file system or device driver)
> > selects it directly or indirectly.
> > 
> > To properly make KEXEC_SIG available for s390 kernels built with MODULES=y
> > as well as MODULES=n _and_ also not depend on arbitrary options selecting
> > SYSTEM_DATA_VERIFICATION, we set ARCH_SUPPORTS_KEXEC_SIG=y for s390 and
> > select SYSTEM_DATA_VERIFICATION when KEXEC_SIG=y.
> 
> Thanks for fixing the issue.
> 
> Seems the background and change is a little twisting, and selecting
> SYSTEM_DATA_VERIFICATION will cause a bunch of verification feature
> selected. While the change is only s390 related, request s390 expert to
> have look at this change. If no concern from s390 developer, I am also
> fine to it.

...

> > diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
> > index c2c7bf974397..385c1052cf45 100644
> > --- a/arch/s390/Kconfig
> > +++ b/arch/s390/Kconfig
> > @@ -313,7 +313,7 @@ config ARCH_SUPPORTS_KEXEC_FILE
> >  	def_bool y
> >  
> >  config ARCH_SUPPORTS_KEXEC_SIG
> > -	def_bool MODULE_SIG_FORMAT
> > +	def_bool y
> >  
> >  config ARCH_SUPPORTS_KEXEC_PURGATORY
> >  	def_bool y
> > diff --git a/kernel/Kconfig.kexec b/kernel/Kconfig.kexec
> > index 15632358bcf7..df97227cfca9 100644
> > --- a/kernel/Kconfig.kexec
> > +++ b/kernel/Kconfig.kexec
> > @@ -50,6 +50,7 @@ config KEXEC_SIG
> >  	bool "Verify kernel signature during kexec_file_load() syscall"
> >  	depends on ARCH_SUPPORTS_KEXEC_SIG
> >  	depends on KEXEC_FILE
> > +	select SYSTEM_DATA_VERIFICATION if S390

Alexander, would it make sense to move this to arch/s390/Kconfig and
add something like

	select SYSTEM_DATA_VERIFICATION if KEXEC_SIG

instead? This would have the slight advantage to keep arch specifics
out of common code Kconfig.