[PATCH v4 16/18] KVM: arm64: Introduce pkvm_dump_backtrace()

[Kalesh Singh <kaleshsingh@google.com>]

Dumps the pKVM hypervisor backtrace from EL1 by reading the unwinded
addresses from the shared stacktrace buffer.

Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
---
 arch/arm64/include/asm/stacktrace/nvhe.h | 49 ++++++++++++++++++++++++
 1 file changed, 49 insertions(+)

diff --git a/arch/arm64/include/asm/stacktrace/nvhe.h b/arch/arm64/include/asm/stacktrace/nvhe.h
index c3f94b10f8f0..ec1a4ee21c21 100644
--- a/arch/arm64/include/asm/stacktrace/nvhe.h
+++ b/arch/arm64/include/asm/stacktrace/nvhe.h
@@ -190,5 +190,54 @@ static int notrace unwind_next(struct unwind_state *state)
 }
 NOKPROBE_SYMBOL(unwind_next);
 
+#ifdef CONFIG_PROTECTED_NVHE_STACKTRACE
+DECLARE_KVM_NVHE_PER_CPU(unsigned long [NVHE_STACKTRACE_SIZE/sizeof(long)], pkvm_stacktrace);
+
+/**
+ * pkvm_dump_backtrace - Dump the protected nVHE HYP backtrace.
+ *
+ * @hyp_offset: hypervisor offset, used for address translation.
+ *
+ * Dumping of the pKVM HYP backtrace is done by reading the
+ * stack addresses from the shared stacktrace buffer, since the
+ * host cannot direclty access hyperviosr memory in protected
+ * mode.
+ */
+static inline void pkvm_dump_backtrace(unsigned long hyp_offset)
+{
+	unsigned long *stacktrace_pos;
+	unsigned long va_mask, pc;
+
+	stacktrace_pos = (unsigned long *)this_cpu_ptr_nvhe_sym(pkvm_stacktrace);
+	va_mask = GENMASK_ULL(vabits_actual - 1, 0);
+
+	kvm_err("Protected nVHE HYP call trace:\n");
+
+	/* The stack trace is terminated by a null entry */
+	for (; *stacktrace_pos; stacktrace_pos++) {
+		/* Mask tags and convert to kern addr */
+		pc = (*stacktrace_pos & va_mask) + hyp_offset;
+		kvm_err(" [<%016lx>] %pB\n", pc, (void *)pc);
+	}
+
+	kvm_err("---- End of Protected nVHE HYP call trace ----\n");
+}
+#else	/* !CONFIG_PROTECTED_NVHE_STACKTRACE */
+static inline void pkvm_dump_backtrace(unsigned long hyp_offset)
+{
+	kvm_err("Cannot dump pKVM nVHE stacktrace: !CONFIG_PROTECTED_NVHE_STACKTRACE\n");
+}
+#endif /* CONFIG_PROTECTED_NVHE_STACKTRACE */
+
+/**
+ * kvm_nvhe_dump_backtrace - Dump KVM nVHE hypervisor backtrace.
+ *
+ * @hyp_offset: hypervisor offset, used for address translation.
+ */
+static inline void kvm_nvhe_dump_backtrace(unsigned long hyp_offset)
+{
+	if (is_protected_kvm_enabled())
+		pkvm_dump_backtrace(hyp_offset);
+}
 #endif	/* __KVM_NVHE_HYPERVISOR__ */
 #endif	/* __ASM_STACKTRACE_NVHE_H */
-- 
2.37.0.170.g444d1eabd0-goog