[RFC PATCH v2 6/8] arm64: Check the return PC of every stack frame

[madvenka@linux.microsoft.com]

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

If a function encountered in a stack trace is not a valid kernel text
address, the stack trace is considered unreliable. Mark the stack trace
as not reliable.

Signed-off-by: Madhavan T. Venkataraman <madvenka@linux.microsoft.com>
---
 arch/arm64/kernel/stacktrace.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index 594806a0c225..358aae3906d7 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -101,6 +101,16 @@ static void check_if_reliable(unsigned long fp, struct stackframe *frame,
 		}
 	}
 #endif
+
+	/*
+	 * A NULL or invalid return address probably means there's some
+	 * generated code which __kernel_text_address() doesn't know about.
+	 * Mark the stack trace as not reliable.
+	 */
+	if (!__kernel_text_address(frame->pc)) {
+		frame->reliable = false;
+		return;
+	}
 }
 
 /*
-- 
2.25.1