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-rw-r--r--tools/perf/examples/bpf/etcsnoop.c76
1 files changed, 76 insertions, 0 deletions
diff --git a/tools/perf/examples/bpf/etcsnoop.c b/tools/perf/examples/bpf/etcsnoop.c
new file mode 100644
index 000000000..e81b53534
--- /dev/null
+++ b/tools/perf/examples/bpf/etcsnoop.c
@@ -0,0 +1,76 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Augment the filename syscalls with the contents of the filename pointer argument
+ * filtering only those that do not start with /etc/.
+ *
+ * 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>
+
+/* bpf-output associated map */
+bpf_map(__augmented_syscalls__, PERF_EVENT_ARRAY, int, u32, __NR_CPUS__);
+
+struct augmented_filename {
+ int size;
+ int reserved;
+ char value[64];
+};
+
+#define augmented_filename_syscall_enter(syscall) \
+struct augmented_enter_##syscall##_args { \
+ struct syscall_enter_##syscall##_args args; \
+ struct augmented_filename filename; \
+}; \
+int syscall_enter(syscall)(struct syscall_enter_##syscall##_args *args) \
+{ \
+ char etc[6] = "/etc/"; \
+ struct augmented_enter_##syscall##_args augmented_args = { .filename.reserved = 0, }; \
+ probe_read(&augmented_args.args, sizeof(augmented_args.args), args); \
+ augmented_args.filename.size = probe_read_str(&augmented_args.filename.value, \
+ sizeof(augmented_args.filename.value), \
+ args->filename_ptr); \
+ if (__builtin_memcmp(augmented_args.filename.value, etc, 4) != 0) \
+ return 0; \
+ /* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */ \
+ return perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, \
+ &augmented_args, \
+ (sizeof(augmented_args) - sizeof(augmented_args.filename.value) + \
+ augmented_args.filename.size)); \
+}
+
+struct syscall_enter_openat_args {
+ unsigned long long common_tp_fields;
+ long syscall_nr;
+ long dfd;
+ char *filename_ptr;
+ long flags;
+ long mode;
+};
+
+augmented_filename_syscall_enter(openat);
+
+struct syscall_enter_open_args {
+ unsigned long long common_tp_fields;
+ long syscall_nr;
+ char *filename_ptr;
+ long flags;
+ long mode;
+};
+
+augmented_filename_syscall_enter(open);
+
+license(GPL);