uprobes/tracing: Generalize struct uprobe_trace_entry_head

struct uprobe_trace_entry_head has a single member for reporting,
"unsigned long ip". If we want to support uretprobes we need to
create another struct which has "func" and "ret_ip" and duplicate
a lot of functions, like trace_kprobe.c does.

To avoid this copy-and-paste horror we turn ->ip into ->vaddr[]
and add couple of trivial helpers to calculate sizeof/data. This
uglifies the code a bit, but this allows us to avoid a lot more
complications later, when we add the support for ret-probes.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Tested-by: Anton Arapov <anton@redhat.com>

kernel/trace/trace.h

@@ -103,11 +103,6 @@ struct kretprobe_trace_entry_head {
 	unsigned long		ret_ip;
 };
 
-struct uprobe_trace_entry_head {
-	struct trace_entry	ent;
-	unsigned long		ip;
-};
-
 /*
  * trace_flag_type is an enumeration that holds different
  * states when a trace occurs. These are:

kernel/trace/trace_uprobe.c

@@ -28,6 +28,18 @@
 
 #define UPROBE_EVENT_SYSTEM	"uprobes"
 
+struct uprobe_trace_entry_head {
+	struct trace_entry	ent;
+	unsigned long		vaddr[];
+};
+
+#define SIZEOF_TRACE_ENTRY(is_return)			\
+	(sizeof(struct uprobe_trace_entry_head) +	\
+	 sizeof(unsigned long) * (is_return ? 2 : 1))
+
+#define DATAOF_TRACE_ENTRY(entry, is_return)		\
+	((void*)(entry) + SIZEOF_TRACE_ENTRY(is_return))
+
 struct trace_uprobe_filter {
 	rwlock_t		rwlock;
 	int			nr_systemwide;
@@ -491,20 +503,19 @@ static int uprobe_trace_func(struct trace_uprobe *tu, struct pt_regs *regs)
 	struct uprobe_trace_entry_head *entry;
 	struct ring_buffer_event *event;
 	struct ring_buffer *buffer;
-	u8 *data;
+	void *data;
 	int size, i;
 	struct ftrace_event_call *call = &tu->call;
 
-	size = sizeof(*entry) + tu->size;
-
+	size = SIZEOF_TRACE_ENTRY(false) + tu->size;
 	event = trace_current_buffer_lock_reserve(&buffer, call->event.type,
 						  size, 0, 0);
 	if (!event)
 		return 0;
 
 	entry = ring_buffer_event_data(event);
-	entry->ip = instruction_pointer(regs);
-	data = (u8 *)&entry[1];
+	entry->vaddr[0] = instruction_pointer(regs);
+	data = DATAOF_TRACE_ENTRY(entry, false);
 	for (i = 0; i < tu->nr_args; i++)
 		call_fetch(&tu->args[i].fetch, regs, data + tu->args[i].offset);
 
@@ -518,22 +529,22 @@ static int uprobe_trace_func(struct trace_uprobe *tu, struct pt_regs *regs)
 static enum print_line_t
 print_uprobe_event(struct trace_iterator *iter, int flags, struct trace_event *event)
 {
-	struct uprobe_trace_entry_head *field;
+	struct uprobe_trace_entry_head *entry;
 	struct trace_seq *s = &iter->seq;
 	struct trace_uprobe *tu;
 	u8 *data;
 	int i;
 
-	field = (struct uprobe_trace_entry_head *)iter->ent;
+	entry = (struct uprobe_trace_entry_head *)iter->ent;
 	tu = container_of(event, struct trace_uprobe, call.event);
 
-	if (!trace_seq_printf(s, "%s: (0x%lx)", tu->call.name, field->ip))
+	if (!trace_seq_printf(s, "%s: (0x%lx)", tu->call.name, entry->vaddr[0]))
 		goto partial;
 
-	data = (u8 *)&field[1];
+	data = DATAOF_TRACE_ENTRY(entry, false);
 	for (i = 0; i < tu->nr_args; i++) {
 		if (!tu->args[i].type->print(s, tu->args[i].name,
-					     data + tu->args[i].offset, field))
+					     data + tu->args[i].offset, entry))
 			goto partial;
 	}
 
@@ -585,16 +596,17 @@ static void probe_event_disable(struct trace_uprobe *tu, int flag)
 
 static int uprobe_event_define_fields(struct ftrace_event_call *event_call)
 {
-	int ret, i;
+	int ret, i, size;
 	struct uprobe_trace_entry_head field;
-	struct trace_uprobe *tu = (struct trace_uprobe *)event_call->data;
+	struct trace_uprobe *tu = event_call->data;
 
-	DEFINE_FIELD(unsigned long, ip, FIELD_STRING_IP, 0);
+	DEFINE_FIELD(unsigned long, vaddr[0], FIELD_STRING_IP, 0);
+	size = SIZEOF_TRACE_ENTRY(false);
 	/* Set argument names as fields */
 	for (i = 0; i < tu->nr_args; i++) {
 		ret = trace_define_field(event_call, tu->args[i].type->fmttype,
 					 tu->args[i].name,
-					 sizeof(field) + tu->args[i].offset,
+					 size + tu->args[i].offset,
 					 tu->args[i].type->size,
 					 tu->args[i].type->is_signed,
 					 FILTER_OTHER);
@@ -748,33 +760,31 @@ static int uprobe_perf_func(struct trace_uprobe *tu, struct pt_regs *regs)
 	struct ftrace_event_call *call = &tu->call;
 	struct uprobe_trace_entry_head *entry;
 	struct hlist_head *head;
-	u8 *data;
-	int size, __size, i;
-	int rctx;
+	unsigned long ip;
+	void *data;
+	int size, rctx, i;
 
 	if (!uprobe_perf_filter(&tu->consumer, 0, current->mm))
 		return UPROBE_HANDLER_REMOVE;
 
-	__size = sizeof(*entry) + tu->size;
-	size = ALIGN(__size + sizeof(u32), sizeof(u64));
-	size -= sizeof(u32);
+	size = SIZEOF_TRACE_ENTRY(false);
+	size = ALIGN(size + tu->size + sizeof(u32), sizeof(u64)) - sizeof(u32);
 	if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE, "profile buffer not large enough"))
 		return 0;
 
 	preempt_disable();
-
 	entry = perf_trace_buf_prepare(size, call->event.type, regs, &rctx);
 	if (!entry)
 		goto out;
 
-	entry->ip = instruction_pointer(regs);
-	data = (u8 *)&entry[1];
+	ip = instruction_pointer(regs);
+	entry->vaddr[0] = ip;
+	data = DATAOF_TRACE_ENTRY(entry, false);
 	for (i = 0; i < tu->nr_args; i++)
 		call_fetch(&tu->args[i].fetch, regs, data + tu->args[i].offset);
 
 	head = this_cpu_ptr(call->perf_events);
-	perf_trace_buf_submit(entry, size, rctx, entry->ip, 1, regs, head, NULL);
-
+	perf_trace_buf_submit(entry, size, rctx, ip, 1, regs, head, NULL);
  out:
 	preempt_enable();
 	return 0;
@@ -784,7 +794,7 @@ static int uprobe_perf_func(struct trace_uprobe *tu, struct pt_regs *regs)
 static
 int trace_uprobe_register(struct ftrace_event_call *event, enum trace_reg type, void *data)
 {
-	struct trace_uprobe *tu = (struct trace_uprobe *)event->data;
+	struct trace_uprobe *tu = event->data;
 
 	switch (type) {
 	case TRACE_REG_REGISTER: