From 97c358198e73c4d3feff561ebf813e84cfb1ef5a Mon Sep 17 00:00:00 2001 From: Mete Durlu Date: Mon, 31 Aug 2026 11:57:15 +0200 Subject: 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 Signed-off-by: Andrew Morton Reviewed-by: Bradley Morgan Suggested-by: Sven Schnelle Reviewed-by: Andrew Morton Cc: Alexander Gordeev Cc: Andreas Larsson Cc: Christian Borntraeger Cc: David S. Miller Cc: Heiko Carstens Cc: Petr Mladek Cc: Vasily Gorbik --- include/linux/panic.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/panic.h') diff --git a/include/linux/panic.h b/include/linux/panic.h index f1dd417e54b2..98dd7dfd27de 100644 --- a/include/linux/panic.h +++ b/include/linux/panic.h @@ -110,4 +110,6 @@ extern void add_taint(unsigned flag, enum lockdep_ok); extern int test_taint(unsigned flag); extern unsigned long get_taint(void); +void arch_do_panic(void); + #endif /* _LINUX_PANIC_H */ -- cgit v1.2.3 From 9cbe4c3344734464263ac4561fe4f639d332fc6e Mon Sep 17 00:00:00 2001 From: Bradley Morgan Date: Wed, 16 Sep 2026 18:29:55 +0000 Subject: panic: restore variable arguments to nmi_panic() nmi_panic() used to accept variable arguments until commit ebc41f20d77f ("panic: change nmi_panic from macro to function") flattened it to a final message string. vpanic() did not exist back then, so the function had to format through panic("%s", msg). Bring the variable arguments back and format with vpanic() directly. The next patch makes nmi_panic() try the panic_force_cpu= redirect before claiming panic_cpu. panic_try_force_cpu() needs to print the message but it is used also by panic() which accepts variable argument list. The string could be formatted only when a CPU gets assigned to process the redirection. Otherwise, there might be a race when writing to the `panic_force_buf`. No current caller passes a string with format specifiers. The closest one is hpwdt_pretimeout(), which builds panic_msg with hex_byte_pack() and has only two variants, both plain strings. But the new __printf() annotation on nmi_panic() would warn with -Wformat-security there because the buffer is passed directly as the format argument, so switch it to nmi_panic(regs, "%s", panic_msg). [pmladek@suse.com: changelog fix] Link: https://lore.kernel.org/arJxFybmtD7OBIcL@pathway.suse.cz Link: https://lore.kernel.org/20260916182957.7788-5-brads@mainlining.org Signed-off-by: Bradley Morgan Signed-off-by: Andrew Morton Suggested-by: Petr Mladek Reviewed-by: Petr Mladek Cc: Guenetr Roeck Cc: Sashiko Cc: Wang Jinchao Cc: Wim Van Sebroeck Cc: --- drivers/watchdog/hpwdt.c | 2 +- include/linux/panic.h | 3 ++- kernel/panic.c | 10 ++++++++-- 3 files changed, 11 insertions(+), 4 deletions(-) (limited to 'include/linux/panic.h') diff --git a/drivers/watchdog/hpwdt.c b/drivers/watchdog/hpwdt.c index 8af1fad2de0b..78227d200afe 100644 --- a/drivers/watchdog/hpwdt.c +++ b/drivers/watchdog/hpwdt.c @@ -199,7 +199,7 @@ static int hpwdt_pretimeout(unsigned int ulReason, struct pt_regs *regs) } hex_byte_pack(panic_msg, nmistat); - nmi_panic(regs, panic_msg); + nmi_panic(regs, "%s", panic_msg); return NMI_HANDLED; } diff --git a/include/linux/panic.h b/include/linux/panic.h index 98dd7dfd27de..17e61b61c45f 100644 --- a/include/linux/panic.h +++ b/include/linux/panic.h @@ -13,7 +13,8 @@ __printf(1, 2) void panic(const char *fmt, ...) __noreturn __cold; __printf(1, 0) void vpanic(const char *fmt, va_list args) __noreturn __cold; -void nmi_panic(struct pt_regs *regs, const char *msg); +__printf(2, 3) +void nmi_panic(struct pt_regs *regs, const char *fmt, ...); void check_panic_on_warn(const char *origin); extern void oops_enter(void); extern void oops_exit(void); diff --git a/kernel/panic.c b/kernel/panic.c index 7388eb81a1c4..e240ca06faab 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -518,13 +518,19 @@ EXPORT_SYMBOL(panic_on_other_cpu); * nmi_panic_self_stop() which can provide architecture dependent code such * as saving register state for crash dump. */ -void nmi_panic(struct pt_regs *regs, const char *msg) +void nmi_panic(struct pt_regs *regs, const char *fmt, ...) { + va_list args; + + va_start(args, fmt); + if (panic_try_start()) - panic("%s", msg); + vpanic(fmt, args); if (panic_on_other_cpu()) nmi_panic_self_stop(regs); + + va_end(args); } EXPORT_SYMBOL(nmi_panic); -- cgit v1.2.3