1// SPDX-License-Identifier: GPL-2.0
 2/*
 3 * Augment the filename syscalls with the contents of the filename pointer argument
 4 * filtering only those that do not start with /etc/.
 5 *
 6 * Test it with:
 7 *
 8 * perf trace -e tools/perf/examples/bpf/augmented_syscalls.c cat /etc/passwd > /dev/null
 9 *
10 * It'll catch some openat syscalls related to the dynamic linked and
11 * the last one should be the one for '/etc/passwd'.
12 *
13 * This matches what is marshalled into the raw_syscall:sys_enter payload
14 * expected by the 'perf trace' beautifiers, and can be used by them unmodified,
15 * which will be done as that feature is implemented in the next csets, for now
16 * it will appear in a dump done by the default tracepoint handler in 'perf trace',
17 * that uses bpf_output__fprintf() to just dump those contents, as done with
18 * the bpf-output event associated with the __bpf_output__ map declared in
19 * tools/perf/include/bpf/stdio.h.
20 */
21
22#include <stdio.h>
23
24/* bpf-output associated map */
25bpf_map(__augmented_syscalls__, PERF_EVENT_ARRAY, int, u32, __NR_CPUS__);
26
27struct augmented_filename {
28	int	size;
29	int	reserved;
30	char	value[64];
31};
32
33#define augmented_filename_syscall_enter(syscall) 						\
34struct augmented_enter_##syscall##_args {			 				\
35	struct syscall_enter_##syscall##_args	args;				 		\
36	struct augmented_filename		filename;				 	\
37};												\
38int syscall_enter(syscall)(struct syscall_enter_##syscall##_args *args)				\
39{												\
40	char etc[6] = "/etc/";									\
41	struct augmented_enter_##syscall##_args augmented_args = { .filename.reserved = 0, }; 	\
42	probe_read(&augmented_args.args, sizeof(augmented_args.args), args);			\
43	augmented_args.filename.size = probe_read_str(&augmented_args.filename.value, 		\
44						      sizeof(augmented_args.filename.value), 	\
45						      args->filename_ptr); 			\
46	if (__builtin_memcmp(augmented_args.filename.value, etc, 4) != 0)			\
47		return 0;									\
48	/* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */	\
49	return perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, 		\
50				 &augmented_args,						\
51				 (sizeof(augmented_args) - sizeof(augmented_args.filename.value) + \
52				 augmented_args.filename.size));				\
53}
54
55struct syscall_enter_openat_args {
56	unsigned long long common_tp_fields;
57	long		   syscall_nr;
58	long		   dfd;
59	char		   *filename_ptr;
60	long		   flags;
61	long		   mode;
62};
63
64augmented_filename_syscall_enter(openat);
65
66struct syscall_enter_open_args {
67	unsigned long long common_tp_fields;
68	long		   syscall_nr;
69	char		   *filename_ptr;
70	long		   flags;
71	long		   mode;
72};
73
74augmented_filename_syscall_enter(open);
75
76license(GPL);