Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/tools/perf/include/bpf/bpf.h b/tools/perf/include/bpf/bpf.h
index 47897d6..b422aee 100644
--- a/tools/perf/include/bpf/bpf.h
+++ b/tools/perf/include/bpf/bpf.h
@@ -18,6 +18,35 @@
         unsigned int numa_node;
 };
 
+#define bpf_map(name, _type, type_key, type_val, _max_entries)	\
+struct bpf_map SEC("maps") name = {				\
+	.type	     = BPF_MAP_TYPE_##_type,			\
+	.key_size    = sizeof(type_key),			\
+	.value_size  = sizeof(type_val),			\
+	.max_entries = _max_entries,				\
+};								\
+struct ____btf_map_##name {					\
+	type_key key;						\
+	type_val value;                                 	\
+};								\
+struct ____btf_map_##name __attribute__((section(".maps." #name), used)) \
+	____btf_map_##name = { }
+
+/*
+ * FIXME: this should receive .max_entries as a parameter, as careful
+ *	  tuning of these limits is needed to avoid hitting limits that
+ *	  prevents other BPF constructs, such as tracepoint handlers,
+ *	  to get installed, with cryptic messages from libbpf, etc.
+ *	  For the current need, 'perf trace --filter-pids', 64 should
+ *	  be good enough, but this surely needs to be revisited.
+ */
+#define pid_map(name, value_type) bpf_map(name, HASH, pid_t, value_type, 64)
+
+static int (*bpf_map_update_elem)(struct bpf_map *map, void *key, void *value, u64 flags) = (void *)BPF_FUNC_map_update_elem;
+static void *(*bpf_map_lookup_elem)(struct bpf_map *map, void *key) = (void *)BPF_FUNC_map_lookup_elem;
+
+static void (*bpf_tail_call)(void *ctx, void *map, int index) = (void *)BPF_FUNC_tail_call;
+
 #define SEC(NAME) __attribute__((section(NAME),  used))
 
 #define probe(function, vars) \
@@ -26,6 +55,9 @@
 #define syscall_enter(name) \
 	SEC("syscalls:sys_enter_" #name) syscall_enter_ ## name
 
+#define syscall_exit(name) \
+	SEC("syscalls:sys_exit_" #name) syscall_exit_ ## name
+
 #define license(name) \
 char _license[] SEC("license") = #name; \
 int _version SEC("version") = LINUX_VERSION_CODE;
@@ -33,4 +65,6 @@
 static int (*probe_read)(void *dst, int size, const void *unsafe_addr) = (void *)BPF_FUNC_probe_read;
 static int (*probe_read_str)(void *dst, int size, const void *unsafe_addr) = (void *)BPF_FUNC_probe_read_str;
 
+static int (*perf_event_output)(void *, struct bpf_map *, int, void *, unsigned long) = (void *)BPF_FUNC_perf_event_output;
+
 #endif /* _PERF_BPF_H */