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From:   Tiezhu Yang <yangtiezhu@loongson.cn>
To:     Huacai Chen <chenhuacai@kernel.org>
Cc:     loongarch@lists.linux.dev, linux-kernel@vger.kernel.org,
        loongson-kernel@lists.loongnix.cn
Subject: [PATCH v3 1/2] LoongArch: Remove noreturn attribute for die()
Date:   Mon, 14 Aug 2023 17:35:03 +0800
Message-Id: <1692005704-19126-2-git-send-email-yangtiezhu@loongson.cn>
In-Reply-To: <1692005704-19126-1-git-send-email-yangtiezhu@loongson.cn>
References: <1692005704-19126-1-git-send-email-yangtiezhu@loongson.cn>
Precedence: bulk

If notify_die() returns NOTIFY_STOP, honor the return value from the
handler chain invocation in die() as, through a debugger, the fault
may have been fixed. It makes sense even if ignoring the event will
make the system unstable, by allowing access through a debugger it
has been compromised already anyway. So we can remove the noreturn
attribute for die() to make our port consistent with x86, arm64,
riscv and csky.

Commit 20c0d2d44029 ("[PATCH] i386: pass proper trap numbers to die
chain handlers") may be the earliest of similar changes.

Link: https://lore.kernel.org/all/alpine.DEB.2.21.2308132148500.8596@angie.orcam.me.uk/
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---
 arch/loongarch/include/asm/ptrace.h |  2 +-
 arch/loongarch/kernel/traps.c       | 12 ++++++------
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/arch/loongarch/include/asm/ptrace.h b/arch/loongarch/include/asm/ptrace.h
index 35f0958..164bc90 100644
--- a/arch/loongarch/include/asm/ptrace.h
+++ b/arch/loongarch/include/asm/ptrace.h
@@ -162,7 +162,7 @@ static inline void regs_set_return_value(struct pt_regs *regs, unsigned long val
 #define instruction_pointer(regs) ((regs)->csr_era)
 #define profile_pc(regs) instruction_pointer(regs)
 
-extern void die(const char *, struct pt_regs *) __noreturn;
+extern void die(const char *, struct pt_regs *);
 
 static inline void die_if_kernel(const char *str, struct pt_regs *regs)
 {
diff --git a/arch/loongarch/kernel/traps.c b/arch/loongarch/kernel/traps.c
index 8fb5e7a..bbdfc5b 100644
--- a/arch/loongarch/kernel/traps.c
+++ b/arch/loongarch/kernel/traps.c
@@ -383,16 +383,15 @@ void show_registers(struct pt_regs *regs)
 
 static DEFINE_RAW_SPINLOCK(die_lock);
 
-void __noreturn die(const char *str, struct pt_regs *regs)
+void die(const char *str, struct pt_regs *regs)
 {
 	static int die_counter;
-	int sig = SIGSEGV;
+	int ret;
 
 	oops_enter();
 
-	if (notify_die(DIE_OOPS, str, regs, 0, current->thread.trap_nr,
-		       SIGSEGV) == NOTIFY_STOP)
-		sig = 0;
+	ret = notify_die(DIE_OOPS, str, regs, 0,
+			 current->thread.trap_nr, SIGSEGV);
 
 	console_verbose();
 	raw_spin_lock_irq(&die_lock);
@@ -414,7 +413,8 @@ void __noreturn die(const char *str, struct pt_regs *regs)
 	if (panic_on_oops)
 		panic("Fatal exception");
 
-	make_task_dead(sig);
+	if (ret != NOTIFY_STOP)
+		make_task_dead(SIGSEGV);
 }
 
 static inline void setup_vint_size(unsigned int size)
-- 
2.1.0