[RFC PATCH v2 4/4] tracing/kprobe: Combine bpf output and perf event output

[He Kuang]

Check and collect temporary trace buffer in the stage of preparing
perf trace buffer. If there're data to be collected, set invalid flag,
extend the trace buffer size and move the data to proper offset, so
the combined data will be compatible to the orignal format and can be
processed by perf-script.

Signed-off-by: He Kuang <hekuang@xxxxxxxxxx>
---
 kernel/trace/trace_kprobe.c | 36 ++++++++++++++++++++++++++++++++++--
 1 file changed, 34 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 16ad88e..274735b 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -1140,6 +1140,8 @@ kprobe_perf_func(struct trace_kprobe *tk, struct pt_regs *regs)
 	struct hlist_head *head;
 	int size, __size, dsize;
 	int rctx;
+	u32 buf_tail_size;
+	char *buf_tail;
 
 	head = this_cpu_ptr(call->perf_events);
 	if (hlist_empty(head))
@@ -1152,15 +1154,29 @@ kprobe_perf_func(struct trace_kprobe *tk, struct pt_regs *regs)
 	if (prog && !trace_call_bpf(prog, regs))
 		goto out;
 
+	/* Check trace buf */
+	buf_tail = get_perf_trace_buf(rctx) +
+		PERF_MAX_TRACE_SIZE - sizeof(u32);
+	buf_tail_size = *(u32 *)buf_tail;
+
+	/* Clear size to invalid buf */
+	*(u32 *)buf_tail = 0;
+
+	if (buf_tail_size != 0)
+		buf_tail -= buf_tail_size;
+
 	dsize = __get_data_size(&tk->tp, regs);
 	__size = sizeof(*entry) + tk->tp.size + dsize;
-	size = ALIGN(__size + sizeof(u32), sizeof(u64));
+	size = ALIGN(__size + buf_tail_size + sizeof(u32), sizeof(u64));
 	size -= sizeof(u32);
 
 	entry = perf_trace_buf_prepare_rctx(size, call->event.type, NULL, rctx);
 	if (!entry)
 		goto out;
 
+	/* Move temporary buf to proper offset */
+	memmove((char *)entry + __size, buf_tail, buf_tail_size);
+
 	entry->ip = (unsigned long)tk->rp.kp.addr;
 	memset(&entry[1], 0, dsize);
 	store_trace_args(sizeof(*entry), &tk->tp, regs, (u8 *)&entry[1], dsize);
@@ -1183,6 +1199,8 @@ kretprobe_perf_func(struct trace_kprobe *tk, struct kretprobe_instance *ri,
 	struct hlist_head *head;
 	int size, __size, dsize;
 	int rctx;
+	u32 buf_tail_size;
+	char *buf_tail;
 
 	head = this_cpu_ptr(call->perf_events);
 	if (hlist_empty(head))
@@ -1195,15 +1213,29 @@ kretprobe_perf_func(struct trace_kprobe *tk, struct kretprobe_instance *ri,
 	if (prog && !trace_call_bpf(prog, regs))
 		goto out;
 
+	/* Check trace buf */
+	buf_tail = get_perf_trace_buf(rctx) +
+		PERF_MAX_TRACE_SIZE - sizeof(u32);
+	buf_tail_size = *(u32 *)buf_tail;
+
+	/* Clear size to invalid buf */
+	*(u32 *)buf_tail = 0;
+
+	if (buf_tail_size != 0)
+		buf_tail -= buf_tail_size;
+
 	dsize = __get_data_size(&tk->tp, regs);
 	__size = sizeof(*entry) + tk->tp.size + dsize;
-	size = ALIGN(__size + sizeof(u32), sizeof(u64));
+	size = ALIGN(__size + buf_tail_size + sizeof(u32), sizeof(u64));
 	size -= sizeof(u32);
 
 	entry = perf_trace_buf_prepare_rctx(size, call->event.type, NULL, rctx);
 	if (!entry)
 		goto out;
 
+	/* Move temporary buf to proper offset */
+	memmove((char *)entry + __size, buf_tail, buf_tail_size);
+
 	entry->func = (unsigned long)tk->rp.kp.addr;
 	entry->ret_ip = (unsigned long)ri->ret_addr;
 	store_trace_args(sizeof(*entry), &tk->tp, regs, (u8 *)&entry[1], dsize);
-- 
1.8.5.2

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