arm64: remove CONFIG_VMAP_STACK checks from stacktrace overflow logic

With VMAP_STACK now always enabled on arm64, remove all CONFIG_VMAP_STACK
conditionals from overflow stack handling in stacktrace code.

This change unconditionally defines the per-CPU overflow_stack and
stackinfo_get_overflow() helper in arch/arm64/include/asm/stacktrace.h,
and always includes the overflow stack in the stack_info array in
arch/arm64/kernel/stacktrace.c. Also, drop redundant CONFIG_VMAP_STACK
checks from SDEI stack declarations.

Signed-off-by: Breno Leitao <leitao@debian.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20250707-arm64_vmap-v1-6-8de98ca0f91c@debian.org
Signed-off-by: Will Deacon <will@kernel.org>

Author: leitao

arch/arm64/include/asm/stacktrace.h

@@ -59,7 +59,6 @@ static inline bool on_task_stack(const struct task_struct *tsk,
 
 #define on_thread_stack()	(on_task_stack(current, current_stack_pointer, 1))
 
-#ifdef CONFIG_VMAP_STACK
 DECLARE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)], overflow_stack);
 
 static inline struct stack_info stackinfo_get_overflow(void)
@@ -72,11 +71,8 @@ static inline struct stack_info stackinfo_get_overflow(void)
 		.high = high,
 	};
 }
-#else
-#define stackinfo_get_overflow()	stackinfo_get_unknown()
-#endif
 
-#if defined(CONFIG_ARM_SDE_INTERFACE) && defined(CONFIG_VMAP_STACK)
+#if defined(CONFIG_ARM_SDE_INTERFACE)
 DECLARE_PER_CPU(unsigned long *, sdei_stack_normal_ptr);
 DECLARE_PER_CPU(unsigned long *, sdei_stack_critical_ptr);
 

arch/arm64/kernel/stacktrace.c

@@ -332,10 +332,8 @@ kunwind_stack_walk(kunwind_consume_fn consume_state,
 	struct stack_info stacks[] = {
 		stackinfo_get_task(task),
 		STACKINFO_CPU(irq),
-#if defined(CONFIG_VMAP_STACK)
 		STACKINFO_CPU(overflow),
-#endif
-#if defined(CONFIG_VMAP_STACK) && defined(CONFIG_ARM_SDE_INTERFACE)
+#if defined(CONFIG_ARM_SDE_INTERFACE)
 		STACKINFO_SDEI(normal),
 		STACKINFO_SDEI(critical),
 #endif