panic: introduce arch_do_panic

Patch series "Introduce arch_do_panic", v6.

Replace architecture-specific ifdef sections in vpanic() with a clean
arch_do_panic() hook.  Currently s390 and sparc embed their panic handlers
directly in vpanic() using preprocessor conditionals, making the common
code path harder to maintain.

Introduce arch_do_panic() as an architecture extension point called at the
end of vpanic().  Architectures can use this hook to implement their
specific panic handling without polluting the generic panic code.

Remove s390s ifdef block in vpanic() and move the corresponding code block
to s390s own arch_do_panic() implementation in architecture specific code.

Move sparc panic handling from ifdef blocks to arch_do_panic().  Remove
the preprocessor conditionals from vpanic() and place the Stop-A
enablement code in architecture-specific files where it belongs.  Stop-A
enablement markers are now printed after "end Kernel panic" line.  To me,
there are no better alternatives other than setup.c to put sparc's
arch_do_panic() implementation.  The other files under arch/sparc/kernel
are either divided to *_32.c and *_64.c variants, which mean code
duplication, or unrelated.

The cleanup reduces vpanic() complexity and establishes a pattern for
other architectures needing custom panic behavior.  No functional changes,
only minor print order changes.


This patch (of 3):

Introduce a hook for architectures to put their specific panic handlers. 
s390 and sparc already have ifdef preprocessor checks to execute
architecture specific code.  Pave the way for vpanic() cleanup.

Link: https://lore.kernel.org/20260831-arch_do_panic-v6-1-a1e170a9e7fd@linux.ibm.com
Link: https://lore.kernel.org/all/20260730-arch_do_panic-v3-0-d5401e683cdb@linux.ibm.com/ [1]
Signed-off-by: Mete Durlu <meted@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Bradley Morgan <include@grrlz.net>
Suggested-by: Sven Schnelle <svens@linux.ibm.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Andreas Larsson <andreas@gaisler.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/kernel/panic.c b/kernel/panic.c
index 213725b612aa..726a97842232 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -567,6 +567,8 @@ static void panic_other_cpus_shutdown(bool crash_kexec)
 		crash_smp_send_stop();
 }
 
+void __weak arch_do_panic(void) {}
+
 /**
  * vpanic - halt the system
  * @fmt: The text string to print
@@ -756,6 +758,7 @@ void vpanic(const char *fmt, va_list args)
 #endif
 	pr_emerg("---[ end Kernel panic - not syncing: %s ]---\n", buf);
 
+	arch_do_panic();
 	/* Do not scroll important messages printed above */
 	suppress_printk = 1;