[PATCH v4 14/18] KVM: arm64: Implement protected nVHE hyp stack unwinder

[Kalesh Singh <kaleshsingh@xxxxxxxxxx>]

Implements the common framework necessary for unwind() to work in
the protected nVHE context:
   - on_accessible_stack()
   - on_overflow_stack()
   - unwind_next()

Protected nVHE unwind() is used to unwind and save the hyp stack
addresses to the shared stacktrace buffer. The host reads the
entries in this buffer, symbolizes and dumps the stacktrace (later
patch in the series).

Signed-off-by: Kalesh Singh <kaleshsingh@xxxxxxxxxx>
---
 arch/arm64/include/asm/stacktrace/common.h |  2 ++
 arch/arm64/include/asm/stacktrace/nvhe.h   | 34 ++++++++++++++++++++--
 2 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/stacktrace/common.h b/arch/arm64/include/asm/stacktrace/common.h
index b362086f4c70..cf442e67dccd 100644
--- a/arch/arm64/include/asm/stacktrace/common.h
+++ b/arch/arm64/include/asm/stacktrace/common.h
@@ -27,6 +27,7 @@ enum stack_type {
 	STACK_TYPE_OVERFLOW,
 	STACK_TYPE_SDEI_NORMAL,
 	STACK_TYPE_SDEI_CRITICAL,
+	STACK_TYPE_HYP,
 	__NR_STACK_TYPES
 };
 
@@ -171,6 +172,7 @@ static inline int unwind_next_common(struct unwind_state *state,
 	 *
 	 * TASK -> IRQ -> OVERFLOW -> SDEI_NORMAL
 	 * TASK -> SDEI_NORMAL -> SDEI_CRITICAL -> OVERFLOW
+	 * HYP -> OVERFLOW
 	 *
 	 * ... but the nesting itself is strict. Once we transition from one
 	 * stack to another, it's never valid to unwind back to that first
diff --git a/arch/arm64/include/asm/stacktrace/nvhe.h b/arch/arm64/include/asm/stacktrace/nvhe.h
index 1aadfd8d7ac9..c7c8ac889ec1 100644
--- a/arch/arm64/include/asm/stacktrace/nvhe.h
+++ b/arch/arm64/include/asm/stacktrace/nvhe.h
@@ -38,10 +38,19 @@ static __always_inline void kvm_nvhe_unwind_init(struct unwind_state *state,
 	state->pc = pc;
 }
 
+static inline bool on_hyp_stack(unsigned long sp, unsigned long size,
+				struct stack_info *info);
+
 static inline bool on_accessible_stack(const struct task_struct *tsk,
 				       unsigned long sp, unsigned long size,
 				       struct stack_info *info)
 {
+	if (on_accessible_stack_common(tsk, sp, size, info))
+		return true;
+
+	if (on_hyp_stack(sp, size, info))
+		return true;
+
 	return false;
 }
 
@@ -59,12 +68,27 @@ extern void kvm_nvhe_prepare_backtrace(unsigned long fp, unsigned long pc);
 static inline bool on_overflow_stack(unsigned long sp, unsigned long size,
 				     struct stack_info *info)
 {
-	return false;
+	unsigned long low = (unsigned long)this_cpu_ptr(overflow_stack);
+	unsigned long high = low + OVERFLOW_STACK_SIZE;
+
+	return on_stack(sp, size, low, high, STACK_TYPE_OVERFLOW, info);
+}
+
+static inline bool on_hyp_stack(unsigned long sp, unsigned long size,
+				struct stack_info *info)
+{
+	struct kvm_nvhe_init_params *params = this_cpu_ptr(&kvm_init_params);
+	unsigned long high = params->stack_hyp_va;
+	unsigned long low = high - PAGE_SIZE;
+
+	return on_stack(sp, size, low, high, STACK_TYPE_HYP, info);
 }
 
 static int notrace unwind_next(struct unwind_state *state)
 {
-	return 0;
+	struct stack_info info;
+
+	return unwind_next_common(state, &info, NULL);
 }
 NOKPROBE_SYMBOL(unwind_next);
 #else	/* !CONFIG_PROTECTED_NVHE_STACKTRACE */
@@ -74,6 +98,12 @@ static inline bool on_overflow_stack(unsigned long sp, unsigned long size,
 	return false;
 }
 
+static inline bool on_hyp_stack(unsigned long sp, unsigned long size,
+				struct stack_info *info)
+{
+	return false;
+}
+
 static int notrace unwind_next(struct unwind_state *state)
 {
 	return 0;
-- 
2.37.0.170.g444d1eabd0-goog

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