[PATCH v6 08/17] KVM: arm64: Stub implementation of non-protected nVHE HYP stack unwinder

[Kalesh Singh <kaleshsingh@google.com>]

Add stub implementations of non-protected nVHE stack unwinder, for
building. These are implemented later in this series.

Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Fuad Tabba <tabba@google.com>
---

Changes in v6:
  - Add Fuad’s Reviewed-by and Tested-by tags

Changes in v5:
  - Mark unwind_next() as inline, per Marc
  - Comment !__KVM_NVHE_HYPERVISOR__ unwinder path, per Marc

 arch/arm64/include/asm/stacktrace/nvhe.h | 47 ++++++++++++++++++++++++
 1 file changed, 47 insertions(+)
 create mode 100644 arch/arm64/include/asm/stacktrace/nvhe.h

diff --git a/arch/arm64/include/asm/stacktrace/nvhe.h b/arch/arm64/include/asm/stacktrace/nvhe.h
new file mode 100644
index 000000000000..1192ae0f80c1
--- /dev/null
+++ b/arch/arm64/include/asm/stacktrace/nvhe.h
@@ -0,0 +1,47 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * KVM nVHE hypervisor stack tracing support.
+ *
+ * The unwinder implementation depends on the nVHE mode:
+ *
+ *   1) Non-protected nVHE mode - the host can directly access the
+ *      HYP stack pages and unwind the HYP stack in EL1. This saves having
+ *      to allocate shared buffers for the host to read the unwinded
+ *      stacktrace.
+ *
+ * Copyright (C) 2022 Google LLC
+ */
+#ifndef __ASM_STACKTRACE_NVHE_H
+#define __ASM_STACKTRACE_NVHE_H
+
+#include <asm/stacktrace/common.h>
+
+static inline bool on_accessible_stack(const struct task_struct *tsk,
+				       unsigned long sp, unsigned long size,
+				       struct stack_info *info)
+{
+	return false;
+}
+
+#ifndef __KVM_NVHE_HYPERVISOR__
+/*
+ * Conventional (non-protected) nVHE HYP stack unwinder
+ *
+ * In non-protected mode, the unwinding is done from kernel proper context
+ * (by the host in EL1).
+ */
+
+static inline bool on_overflow_stack(unsigned long sp, unsigned long size,
+				     struct stack_info *info)
+{
+	return false;
+}
+
+static inline int notrace unwind_next(struct unwind_state *state)
+{
+	return 0;
+}
+NOKPROBE_SYMBOL(unwind_next);
+
+#endif	/* !__KVM_NVHE_HYPERVISOR__ */
+#endif	/* __ASM_STACKTRACE_NVHE_H */
-- 
2.37.1.359.gd136c6c3e2-goog

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