2 files changed, 62 insertions, 0 deletions

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 7232a7302580..9b4e24217c46 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -3240,6 +3240,13 @@ int cmd_trace(int argc, const char **argv)
 				       "cgroup monitoring only available in system-wide mode");
 	}
 
+	err = bpf__setup_output_event(trace.evlist, "__augmented_syscalls__");
+	if (err) {
+		bpf__strerror_setup_output_event(trace.evlist, err, bf, sizeof(bf));
+		pr_err("ERROR: Setup trace syscalls enter failed: %s\n", bf);
+		goto out;
+	}
+
 	err = bpf__setup_stdout(trace.evlist);
 	if (err) {
 		bpf__strerror_setup_stdout(trace.evlist, err, bf, sizeof(bf));
diff --git a/tools/perf/examples/bpf/augmented_syscalls.c b/tools/perf/examples/bpf/augmented_syscalls.c
new file mode 100644
index 000000000000..69a31386d8cd
--- /dev/null
+++ b/tools/perf/examples/bpf/augmented_syscalls.c
@@ -0,0 +1,55 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Augment the openat syscall with the contents of the filename pointer argument.
+ *
+ * Test it with:
+ *
+ * perf trace -e tools/perf/examples/bpf/augmented_syscalls.c cat /etc/passwd > /dev/null
+ *
+ * It'll catch some openat syscalls related to the dynamic linked and
+ * the last one should be the one for '/etc/passwd'.
+ *
+ * This matches what is marshalled into the raw_syscall:sys_enter payload
+ * expected by the 'perf trace' beautifiers, and can be used by them unmodified,
+ * which will be done as that feature is implemented in the next csets, for now
+ * it will appear in a dump done by the default tracepoint handler in 'perf trace',
+ * that uses bpf_output__fprintf() to just dump those contents, as done with
+ * the bpf-output event associated with the __bpf_output__ map declared in
+ * tools/perf/include/bpf/stdio.h.
+ */
+
+#include <stdio.h>
+
+struct bpf_map SEC("maps") __augmented_syscalls__ = {
+       .type = BPF_MAP_TYPE_PERF_EVENT_ARRAY,
+       .key_size = sizeof(int),
+       .value_size = sizeof(u32),
+       .max_entries = __NR_CPUS__,
+};
+
+struct syscall_enter_openat_args {
+	unsigned long long common_tp_fields;
+	long		   syscall_nr;
+	long		   dfd;
+	char		   *filename_ptr;
+	long		   flags;
+	long		   mode;
+};
+
+struct augmented_enter_openat_args {
+	struct syscall_enter_openat_args args;
+	char				 filename[64];
+};
+
+int syscall_enter(openat)(struct syscall_enter_openat_args *args)
+{
+	struct augmented_enter_openat_args augmented_args;
+
+	probe_read(&augmented_args.args, sizeof(augmented_args.args), args);
+	probe_read_str(&augmented_args.filename, sizeof(augmented_args.filename), args->filename_ptr);
+	perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU,
+			  &augmented_args, sizeof(augmented_args));
+	return 1;
+}
+
+license(GPL);