ANDROID: KVM: arm64: Add func/func_ret pKVM hyp events

Those events are raised for whenever a function is entered and exit at
EL2. They rely on Ftrace in the pKVM hypervisor and the later must be
enabled with CONFIG_PROTECTED_NVHE_FTRACE.

Bug: 357781595
Change-Id: Ife7649fba88779ba3bb8bb7f11bbab244141200b
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>

arch/arm64/include/asm/kvm_hypevents.h

@@ -11,6 +11,32 @@
  * Hypervisor events definitions.
  */
 
+#ifdef CONFIG_PROTECTED_NVHE_FTRACE
+HYP_EVENT(func,
+	HE_PROTO(unsigned long ip, unsigned long parent),
+	HE_STRUCT(
+		he_field(unsigned long, ip)
+		he_field(unsigned long, parent)
+	),
+	HE_ASSIGN(
+		__entry->ip = ip;
+		__entry->parent = parent;
+	),
+	HE_PRINTK("    %ps <- %ps", (void *)__entry->ip, (void *)__entry->parent)
+);
+
+HYP_EVENT(func_ret,
+	HE_PROTO(unsigned long ip),
+	HE_STRUCT(
+		he_field(unsigned long, ip)
+	),
+	HE_ASSIGN(
+		__entry->ip = ip;
+	),
+	HE_PRINTK("%ps", (void *)__entry->ip)
+);
+#endif
+
 HYP_EVENT(hyp_enter,
 	HE_PROTO(void),
 	HE_STRUCT(

arch/arm64/kvm/Kconfig

@@ -92,6 +92,18 @@ config PROTECTED_NVHE_TESTING
 
 	  If unsure, say N.
 
+config PROTECTED_NVHE_FTRACE
+	bool "Protected KVM hypervisor function tracing"
+	depends on KVM
+	depends on TRACING
+	default n
+	help
+	  Say Y here to enable func and func_ret hypervisor tracing events.
+	  Those events are raised whenever the hypervisor branch to a
+	  function.
+
+	  If unsure, Say N.
+
 config PKVM_MODULE_PATH
 	string "Path to pKVM modules"
 	default ""

arch/arm64/kvm/hyp/nvhe/ftrace.c

@@ -97,6 +97,8 @@ unsigned long __hyp_ftrace_trace(unsigned long ip, unsigned long parent,
 	/* When modules are called from core */
 	parent_offset_idx = parent > (unsigned long)__hyp_text_start ? 0 : offset_idx;
 
+	trace_func(func, __kern_addr(parent_offset_idx, parent));
+
 	/* Only install the trampoline if we can revert to the original parent */
 	if (hyp_ftrace_func_push(func, parent))
 		return (unsigned long)__hyp_ftrace_ret_tramp;
@@ -109,6 +111,7 @@ unsigned long __hyp_ftrace_ret_trace(void)
 	struct hyp_ftrace_stack_frame *frame = hyp_ftrace_func_pop();
 
 	BUG_ON(!frame);
+	trace_func_ret(frame->func);
 
 	return frame->ret;
 }
@@ -117,8 +120,10 @@ void hyp_ftrace_ret_flush(void)
 {
 	struct hyp_ftrace_stack_frame *frame = hyp_ftrace_func_pop();
 
-	while (frame)
+	while (frame) {
+		trace_func_ret(frame->func);
 		frame = hyp_ftrace_func_pop();
+	}
 }
 
 static int __get_offset_idx_ins(unsigned long *func, unsigned long ip, u32 *insn,