linux-kernel - [PATCH 1/2] powerpc: mark more local variables as volatile

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Date:   Wed,  9 Aug 2023 15:10:08 +0200
From:   Arnd Bergmann <arnd@...nel.org>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     Arnd Bergmann <arnd@...db.de>, Nicholas Piggin <npiggin@...il.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Maninder Singh <maninder1.s@...sung.com>,
        Hugh Dickins <hughd@...gle.com>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Nathan Lynch <nathanl@...ux.ibm.com>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] powerpc: mark more local variables as volatile

From: Arnd Bergmann <arnd@...db.de>

A while ago I created a2305e3de8193 ("powerpc: mark local variables
around longjmp as volatile") in order to allow building powerpc with
-Wextra enabled on gcc-11.

I tried this again with gcc-13 and found two more of the same issues,
presumably based on slightly different optimization paths being taken
here:

arch/powerpc/xmon/xmon.c:3306:27: error: variable 'mm' might be clobbered by 'longjmp' or 'vfork' [-Werror=clobbered]
arch/powerpc/kexec/crash.c:353:22: error: variable 'i' might be clobbered by 'longjmp' or 'vfork' [-Werror=clobbered]

I checked a bunch of randconfigs and found only these two, so just
address them the same way as the others.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 arch/powerpc/kexec/crash.c | 2 +-
 arch/powerpc/xmon/xmon.c   | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kexec/crash.c b/arch/powerpc/kexec/crash.c
index 252724ed666a3..ef5c2d25ec397 100644
--- a/arch/powerpc/kexec/crash.c
+++ b/arch/powerpc/kexec/crash.c
@@ -350,7 +350,7 @@ EXPORT_SYMBOL(crash_shutdown_unregister);
 
 void default_machine_crash_shutdown(struct pt_regs *regs)
 {
-	unsigned int i;
+	volatile unsigned int i;
 	int (*old_handler)(struct pt_regs *regs);
 
 	if (TRAP(regs) == INTERRUPT_SYSTEM_RESET)
diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index 3b6f524c790e3..9e12b75850d75 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -3303,7 +3303,7 @@ static void show_pte(unsigned long addr)
 {
 	unsigned long tskv = 0;
 	struct task_struct *volatile tsk = NULL;
-	struct mm_struct *mm;
+	struct mm_struct *volatile mm;
 	pgd_t *pgdp;
 	p4d_t *p4dp;
 	pud_t *pudp;
-- 
2.39.2