arm64: stacktrace: rework stack boundary discovery

In subsequent patches we'll want to acquire the stack boundaries
ahead-of-time, and we'll need to be able to acquire the relevant
stack_info regardless of whether we have an object the happens to be on
the stack.

This patch replaces the on_XXX_stack() helpers with stackinfo_get_XXX()
helpers, with the caller being responsible for the checking whether an
object is on a relevant stack. For the moment this is moved into the
on_accessible_stack() functions, making these slightly larger;
subsequent patches will remove the on_accessible_stack() functions and
simplify the logic.

The on_irq_stack() and on_task_stack() helpers are kept as these are
used by IRQ entry sequences and stackleak respectively. As they're only
used as predicates, the stack_info pointer parameter is removed in both
cases.

As the on_accessible_stack() functions are always passed a non-NULL info
pointer, these now update info unconditionally. When updating the type
to STACK_TYPE_UNKNOWN, the low/high bounds are also modified, but as
these will not be consumed this should have no adverse affect.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Kalesh Singh <kaleshsingh@google.com>
Reviewed-by: Madhavan T. Venkataraman <madvenka@linux.microsoft.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Cc: Fuad Tabba <tabba@google.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20220901130646.1316937-7-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 42 insertions, 23 deletions

diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index edf9edca2055..ca56fd732c2a 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -67,36 +67,55 @@ static inline void unwind_init_from_task(struct unwind_state *state,
 	state->pc = thread_saved_pc(task);
 }
 
-/*
- * We can only safely access per-cpu stacks from current in a non-preemptible
- * context.
- */
 static bool on_accessible_stack(const struct task_struct *tsk,
 				unsigned long sp, unsigned long size,
 				struct stack_info *info)
 {
-	if (info)
-		info->type = STACK_TYPE_UNKNOWN;
+	struct stack_info tmp;
 
-	if (on_task_stack(tsk, sp, size, info))
-		return true;
-	if (tsk != current || preemptible())
-		return false;
-	if (on_irq_stack(sp, size, info))
-		return true;
-	if (on_overflow_stack(sp, size, info))
-		return true;
-
-	if (IS_ENABLED(CONFIG_VMAP_STACK) &&
-	    IS_ENABLED(CONFIG_ARM_SDE_INTERFACE) &&
-	    in_nmi()) {
-		if (on_sdei_critical_stack(sp, size, info))
-			return true;
-		if (on_sdei_normal_stack(sp, size, info))
-			return true;
-	}
+	tmp = stackinfo_get_task(tsk);
+	if (stackinfo_on_stack(&tmp, sp, size))
+		goto found;
 
+	/*
+	 * We can only safely access per-cpu stacks when unwinding the current
+	 * task in a non-preemptible context.
+	 */
+	if (tsk != current || preemptible())
+		goto not_found;
+
+	tmp = stackinfo_get_irq();
+	if (stackinfo_on_stack(&tmp, sp, size))
+		goto found;
+
+	tmp = stackinfo_get_overflow();
+	if (stackinfo_on_stack(&tmp, sp, size))
+		goto found;
+
+	/*
+	 * We can only safely access SDEI stacks which unwinding the current
+	 * task in an NMI context.
+	 */
+	if (!IS_ENABLED(CONFIG_VMAP_STACK) ||
+	    !IS_ENABLED(CONFIG_ARM_SDE_INTERFACE) ||
+	    !in_nmi())
+		goto not_found;
+
+	tmp = stackinfo_get_sdei_normal();
+	if (stackinfo_on_stack(&tmp, sp, size))
+		goto found;
+
+	tmp = stackinfo_get_sdei_critical();
+	if (stackinfo_on_stack(&tmp, sp, size))
+		goto found;
+
+not_found:
+	*info = stackinfo_get_unknown();
 	return false;
+
+found:
+	*info = tmp;
+	return true;
 }
 
 /*