[PATCH bpf-next v3] tracing: perf_call_bpf: use struct trace_entry in struct syscall_tp_t

[Yauheni Kaliuta <ykaliuta@redhat.com>]

bpf tracepoint program uses struct trace_event_raw_sys_enter as
argument where trace_entry is the first field. Use the same instead
of unsigned long long since if it's amended (for example by RT
patch) it accesses data with wrong offset.

Signed-off-by: Yauheni Kaliuta <ykaliuta@redhat.com>

---

v3:
- Fixed comment

v2:
- remove extra BUILD_BUG_ON
- add structure alignement

---
 kernel/trace/trace_syscalls.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index 942ddbdace4a..de753403cdaf 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -555,12 +555,15 @@ static int perf_call_bpf_enter(struct trace_event_call *call, struct pt_regs *re
 			       struct syscall_trace_enter *rec)
 {
 	struct syscall_tp_t {
-		unsigned long long regs;
+		struct trace_entry ent;
 		unsigned long syscall_nr;
 		unsigned long args[SYSCALL_DEFINE_MAXARGS];
-	} param;
+	} __aligned(8) param;
 	int i;
 
+	BUILD_BUG_ON(sizeof(param.ent) < sizeof(void *));
+
+	/* bpf prog requires 'regs' to be the first member in the ctx (a.k.a. &param) */
 	*(struct pt_regs **)&param = regs;
 	param.syscall_nr = rec->nr;
 	for (i = 0; i < sys_data->nb_args; i++)
@@ -657,11 +660,12 @@ static int perf_call_bpf_exit(struct trace_event_call *call, struct pt_regs *reg
 			      struct syscall_trace_exit *rec)
 {
 	struct syscall_tp_t {
-		unsigned long long regs;
+		struct trace_entry ent;
 		unsigned long syscall_nr;
 		unsigned long ret;
-	} param;
+	} __aligned(8) param;
 
+	/* bpf prog requires 'regs' to be the first member in the ctx (a.k.a. &param) */
 	*(struct pt_regs **)&param = regs;
 	param.syscall_nr = rec->nr;
 	param.ret = rec->ret;
-- 
2.41.0