[PATCH v1 4/7] perf trace: hello fix libbpf 1.0+ compatibility

[Ian Rogers <irogers@google.com>]

Don't use deprecated and now broken map style. Avoid use of
tools/perf/include/bpf/bpf.h and use the more regular BPF headers.
Switch to raw_syscalls:sys_enter to avoid the evlist being
empty and fixing generating output.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/examples/bpf/hello.c | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/tools/perf/examples/bpf/hello.c b/tools/perf/examples/bpf/hello.c
index cf3c2fdc7f79..e9080b0df158 100644
--- a/tools/perf/examples/bpf/hello.c
+++ b/tools/perf/examples/bpf/hello.c
@@ -1,9 +1,27 @@
-#include <stdio.h>
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
 
-int syscall_enter(openat)(void *args)
+struct __bpf_stdout__ {
+	__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
+	__type(key, int);
+	__type(value, __u32);
+	__uint(max_entries, __NR_CPUS__);
+} __bpf_stdout__ SEC(".maps");
+
+#define puts(from) \
+	({ const int __len = sizeof(from); \
+	   char __from[sizeof(from)] = from;			\
+	   bpf_perf_event_output(args, &__bpf_stdout__, BPF_F_CURRENT_CPU, \
+			  &__from, __len & (sizeof(from) - 1)); })
+
+struct syscall_enter_args;
+
+SEC("raw_syscalls:sys_enter")
+int sys_enter(struct syscall_enter_args *args)
 {
 	puts("Hello, world\n");
 	return 0;
 }
 
-license(GPL);
+char _license[] SEC("license") = "GPL";
-- 
2.38.1.273.g43a17bfeac-goog