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Date:   Tue, 26 Jul 2022 00:37:41 -0700
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Subject: [PATCH v6 08/17] KVM: arm64: Stub implementation of non-protected
 nVHE HYP stack unwinder
From:   Kalesh Singh <kaleshsingh@google.com>
To:     maz@kernel.org, mark.rutland@arm.com, broonie@kernel.org,
        madvenka@linux.microsoft.com, tabba@google.com,
        oliver.upton@linux.dev
Cc:     will@kernel.org, qperret@google.com, kaleshsingh@google.com,
        james.morse@arm.com, alexandru.elisei@arm.com,
        suzuki.poulose@arm.com, catalin.marinas@arm.com,
        andreyknvl@gmail.com, vincenzo.frascino@arm.com,
        mhiramat@kernel.org, ast@kernel.org, wangkefeng.wang@huawei.com,
        elver@google.com, keirf@google.com, yuzenghui@huawei.com,
        ardb@kernel.org, oupton@google.com,
        linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu,
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Precedence: bulk

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=E2=80=99s 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 */
--=20
2.37.1.359.gd136c6c3e2-goog