linux-kernel - [PATCH v5 10/17] KVM: arm64: Stub implementation of pKVM HYP stack unwinder

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Message-Id: <20220721055728.718573-11-kaleshsingh@google.com>
Date:   Wed, 20 Jul 2022 22:57:21 -0700
From:   Kalesh Singh <kaleshsingh@...gle.com>
To:     maz@...nel.org, mark.rutland@....com, broonie@...nel.org,
        madvenka@...ux.microsoft.com, tabba@...gle.com
Cc:     will@...nel.org, qperret@...gle.com, kaleshsingh@...gle.com,
        james.morse@....com, alexandru.elisei@....com,
        suzuki.poulose@....com, catalin.marinas@....com,
        andreyknvl@...il.com, vincenzo.frascino@....com,
        mhiramat@...nel.org, ast@...nel.org, drjones@...hat.com,
        wangkefeng.wang@...wei.com, elver@...gle.com, keirf@...gle.com,
        yuzenghui@...wei.com, ardb@...nel.org, oupton@...gle.com,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-kernel@...r.kernel.org, android-mm@...gle.com,
        kernel-team@...roid.com
Subject: [PATCH v5 10/17] KVM: arm64: Stub implementation of pKVM HYP stack unwinder

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

Signed-off-by: Kalesh Singh <kaleshsingh@...gle.com>
---

Changes in v5:
  - Mark unwind_next() as inline, per Marc

 arch/arm64/include/asm/stacktrace/nvhe.h | 59 ++++++++++++++++++++++++
 arch/arm64/kvm/hyp/nvhe/stacktrace.c     |  3 +-
 2 files changed, 60 insertions(+), 2 deletions(-)
 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..80d71932afff
--- /dev/null
+++ b/arch/arm64/include/asm/stacktrace/nvhe.h
@@ -0,0 +1,59 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * KVM nVHE hypervisor stack tracing support.
+ *
+ * The unwinder implementation depends on the nVHE mode:
+ *
+ *   1) pKVM (protected nVHE) mode - the host cannot directly access
+ *      the HYP memory. The stack is unwinded in EL2 and dumped to a shared
+ *      buffer where the host can read and print the 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;
+}
+
+#ifdef __KVM_NVHE_HYPERVISOR__
+/*
+ * Protected nVHE HYP stack unwinder
+ *
+ * In protected mode, the unwinding is done by the hypervisor in EL2.
+ */
+
+#ifdef CONFIG_PROTECTED_NVHE_STACKTRACE
+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);
+#else	/* !CONFIG_PROTECTED_NVHE_STACKTRACE */
+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	/* CONFIG_PROTECTED_NVHE_STACKTRACE */
+
+#endif	/* __KVM_NVHE_HYPERVISOR__ */
+#endif	/* __ASM_STACKTRACE_NVHE_H */
diff --git a/arch/arm64/kvm/hyp/nvhe/stacktrace.c b/arch/arm64/kvm/hyp/nvhe/stacktrace.c
index 69e65b457f1c..96c8b93320eb 100644
--- a/arch/arm64/kvm/hyp/nvhe/stacktrace.c
+++ b/arch/arm64/kvm/hyp/nvhe/stacktrace.c
@@ -4,8 +4,7 @@
  *
  * Copyright (C) 2022 Google LLC
  */
-#include <asm/memory.h>
-#include <asm/percpu.h>
+#include <asm/stacktrace/nvhe.h>
 
 DEFINE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)], overflow_stack)
 	__aligned(16);
-- 
2.37.0.170.g444d1eabd0-goog