linux-kernel - [PATCH v12 09/10] arm64: Introduce arch_stack_walk

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Date:   Mon,  3 Jan 2022 10:52:11 -0600
From:   madvenka@...ux.microsoft.com
To:     mark.rutland@....com, broonie@...nel.org, jpoimboe@...hat.com,
        ardb@...nel.org, nobuta.keiya@...itsu.com,
        sjitindarsingh@...il.com, catalin.marinas@....com, will@...nel.org,
        jmorris@...ei.org, linux-arm-kernel@...ts.infradead.org,
        live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
        madvenka@...ux.microsoft.com
Subject: [PATCH v12 09/10] arm64: Introduce arch_stack_walk_reliable()

From: "Madhavan T. Venkataraman" <madvenka@...ux.microsoft.com>

Introduce arch_stack_walk_reliable() for ARM64. This works like
arch_stack_walk() except that it returns -EINVAL if the stack trace is not
reliable.

Until all the reliability checks are in place, arch_stack_walk_reliable()
may not be used by livepatch. But it may be used by debug and test code.

Signed-off-by: Madhavan T. Venkataraman <madvenka@...ux.microsoft.com>
Reviewed-by: Mark Brown <broonie@...nel.org>
---
 arch/arm64/kernel/stacktrace.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index 1db1ccb61241..717d30833252 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -339,3 +339,27 @@ noinline notrace void arch_stack_walk(stack_trace_consume_fn consume_entry,
 
 	unwind(&state);
 }
+
+/*
+ * arch_stack_walk_reliable() may not be used for livepatch until all of
+ * the reliability checks are in place in unwind_consume(). However,
+ * debug and test code can choose to use it even if all the checks are not
+ * in place.
+ */
+noinline int notrace arch_stack_walk_reliable(stack_trace_consume_fn consume_fn,
+					      void *cookie,
+					      struct task_struct *task)
+{
+	struct unwind_state state;
+	bool reliable;
+
+	unwind_init_common(&state, task, NULL, consume_fn, cookie);
+
+	if (task == current)
+		unwind_init_current(&state);
+	else
+		unwind_init_task(&state);
+
+	reliable = unwind(&state);
+	return reliable ? 0 : -EINVAL;
+}
-- 
2.25.1