[PATCH 5/5] um: remove broken double fault detection

[Benjamin Berg]

From: Benjamin Berg <benjamin.berg at intel.com>

The show_stack function had some code to detect double faults. However,
the logic is wrong and it would e.g. trigger if a WARNING happened
inside an IRQ.

Remove it without trying to add a new logic. The current behaviour,
which will just fault repeatedly until the IRQ stack is used up and the
host kills UML, seems to be good enough.
---
 arch/um/include/shared/os.h | 1 -
 arch/um/kernel/sysrq.c      | 6 ------
 arch/um/os-Linux/signal.c   | 8 --------
 3 files changed, 15 deletions(-)

diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h
index 6c656ef096c9..5babad8c5f75 100644
--- a/arch/um/include/shared/os.h
+++ b/arch/um/include/shared/os.h
@@ -241,7 +241,6 @@ extern void block_signals(void);
 extern void unblock_signals(void);
 extern int um_set_signals(int enable);
 extern int um_set_signals_trace(int enable);
-extern int os_is_signal_stack(void);
 extern void deliver_alarm(void);
 extern void register_pm_wake_signal(void);
 extern void block_signals_hard(void);
diff --git a/arch/um/kernel/sysrq.c b/arch/um/kernel/sysrq.c
index 4bb8622dc512..a3bdab048617 100644
--- a/arch/um/kernel/sysrq.c
+++ b/arch/um/kernel/sysrq.c
@@ -32,12 +32,6 @@ void show_stack(struct task_struct *task, unsigned long *stack,
 	struct pt_regs *segv_regs = current->thread.segv_regs;
 	int i;
 
-	if (!segv_regs && os_is_signal_stack()) {
-		pr_err("Received SIGSEGV in SIGSEGV handler,"
-				" aborting stack trace!\n");
-		return;
-	}
-
 	if (!stack)
 		stack = get_stack_pointer(task, segv_regs);
 
diff --git a/arch/um/os-Linux/signal.c b/arch/um/os-Linux/signal.c
index 1c6caa9dbd6c..52852018a3ad 100644
--- a/arch/um/os-Linux/signal.c
+++ b/arch/um/os-Linux/signal.c
@@ -487,11 +487,3 @@ void unblock_signals_hard(void)
 	unblocking = false;
 }
 #endif
-
-int os_is_signal_stack(void)
-{
-	stack_t ss;
-	sigaltstack(NULL, &ss);
-
-	return ss.ss_flags & SS_ONSTACK;
-}
-- 
2.47.0