linux-kernel - [PATCH v4 1/3] LoongArch: Do not kill the task in die() if notify_die() returns NOTIFY

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Message-Id: <1692694437-27077-2-git-send-email-yangtiezhu@loongson.cn>
Date:   Tue, 22 Aug 2023 16:53:55 +0800
From:   Tiezhu Yang <yangtiezhu@...ngson.cn>
To:     Huacai Chen <chenhuacai@...nel.org>
Cc:     loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org,
        loongson-kernel@...ts.loongnix.cn
Subject: [PATCH v4 1/3] LoongArch: Do not kill the task in die() if notify_die() returns NOTIFY_STOP

If notify_die() returns NOTIFY_STOP, honor the return value from the
handler chain invocation in die() and return without killing the task
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. It
makes 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/r/43DDF02E.76F0.0078.0@novell.com/
Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.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