[RFC PATCH v9 01/50 -fix] tracing, perf: Implement BPF programs attached to uprobes

[Wang Nan]

By copying BPF related operation to uprobe processing path, this patch
allow users attach BPF programs to uprobes like what they are already
doing on kprobes.

After this patch, users are allowed to use PERF_EVENT_IOC_SET_BPF on a
uprobe perf event. Which make it possible to profile user space programs
and kernel events together using BPF.

Because of this patch, CONFIG_BPF_EVENT should be selected by
CONFIG_UPROBE_EVENT to ensure trace_call_bpf() is compiled even if
KPROBE_EVENT is not set.

Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
Acked-by: Alexei Starovoitov <ast@xxxxxxxxxxxx>
---

This patch fixes a building error found by buildlbot that, if
CONFIG_BPF_EVENT is not set, following error occures:

 kernel/built-in.o: In function `__uprobe_perf_func':
 trace_uprobe.c:(.text+0xd6403): undefined reference to `trace_call_bpf'

---
 include/linux/ftrace_event.h | 5 +++++
 kernel/events/core.c         | 4 ++--
 kernel/trace/Kconfig         | 2 +-
 kernel/trace/trace_uprobe.c  | 5 +++++
 4 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index 68cf311..d40272a 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -254,6 +254,7 @@ enum {
 	TRACE_EVENT_FL_USE_CALL_FILTER_BIT,
 	TRACE_EVENT_FL_TRACEPOINT_BIT,
 	TRACE_EVENT_FL_KPROBE_BIT,
+	TRACE_EVENT_FL_UPROBE_BIT,
 };
 
 /*
@@ -268,6 +269,7 @@ enum {
  *  USE_CALL_FILTER - For ftrace internal events, don't use file filter
  *  TRACEPOINT    - Event is a tracepoint
  *  KPROBE        - Event is a kprobe
+ *  UPROBE        - Event is a uprobe
  */
 enum {
 	TRACE_EVENT_FL_FILTERED		= (1 << TRACE_EVENT_FL_FILTERED_BIT),
@@ -278,8 +280,11 @@ enum {
 	TRACE_EVENT_FL_USE_CALL_FILTER	= (1 << TRACE_EVENT_FL_USE_CALL_FILTER_BIT),
 	TRACE_EVENT_FL_TRACEPOINT	= (1 << TRACE_EVENT_FL_TRACEPOINT_BIT),
 	TRACE_EVENT_FL_KPROBE		= (1 << TRACE_EVENT_FL_KPROBE_BIT),
+	TRACE_EVENT_FL_UPROBE		= (1 << TRACE_EVENT_FL_UPROBE_BIT),
 };
 
+#define TRACE_EVENT_FL_UKPROBE (TRACE_EVENT_FL_KPROBE | TRACE_EVENT_FL_UPROBE)
+
 struct ftrace_event_call {
 	struct list_head	list;
 	struct ftrace_event_class *class;
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 9e0773d..18835de 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6775,8 +6775,8 @@ static int perf_event_set_bpf_prog(struct perf_event *event, u32 prog_fd)
 	if (event->tp_event->prog)
 		return -EEXIST;
 
-	if (!(event->tp_event->flags & TRACE_EVENT_FL_KPROBE))
-		/* bpf programs can only be attached to kprobes */
+	if (!(event->tp_event->flags & TRACE_EVENT_FL_UKPROBE))
+		/* bpf programs can only be attached to u/kprobes */
 		return -EINVAL;
 
 	prog = bpf_prog_get(prog_fd);
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 3b9a48a..1153c43 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -434,7 +434,7 @@ config UPROBE_EVENT
 
 config BPF_EVENTS
 	depends on BPF_SYSCALL
-	depends on KPROBE_EVENT
+	depends on KPROBE_EVENT || UPROBE_EVENT
 	bool
 	default y
 	help
diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index 6dd022c..0b580bd 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -1095,11 +1095,15 @@ static void __uprobe_perf_func(struct trace_uprobe *tu,
 {
 	struct ftrace_event_call *call = &tu->tp.call;
 	struct uprobe_trace_entry_head *entry;
+	struct bpf_prog *prog = call->prog;
 	struct hlist_head *head;
 	void *data;
 	int size, esize;
 	int rctx;
 
+	if (prog && !trace_call_bpf(prog, regs))
+		return;
+
 	esize = SIZEOF_TRACE_ENTRY(is_ret_probe(tu));
 
 	size = esize + tu->tp.size + dsize;
@@ -1289,6 +1293,7 @@ static int register_uprobe_event(struct trace_uprobe *tu)
 		return -ENODEV;
 	}
 
+	call->flags = TRACE_EVENT_FL_UPROBE;
 	call->class->reg = trace_uprobe_register;
 	call->data = tu;
 	ret = trace_add_event_call(call);
-- 
1.8.3.4

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