1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Augment the raw_syscalls tracepoints with the contents of the pointer arguments.
4  *
5  * This exactly matches what is marshalled into the raw_syscall:sys_enter
6  * payload expected by the 'perf trace' beautifiers.
7  */
8 
9 #include <linux/bpf.h>
10 #include <bpf/bpf_helpers.h>
11 #include <linux/limits.h>
12 
13 /**
14  * is_power_of_2() - check if a value is a power of two
15  * @n: the value to check
16  *
17  * Determine whether some value is a power of two, where zero is *not*
18  * considered a power of two.  Return: true if @n is a power of 2, otherwise
19  * false.
20  */
21 #define is_power_of_2(n) (n != 0 && ((n & (n - 1)) == 0))
22 
23 #define MAX_CPUS  4096
24 
25 // FIXME: These should come from system headers
26 #ifndef bool
27 typedef char bool;
28 #endif
29 typedef int pid_t;
30 typedef long long int __s64;
31 typedef __s64 time64_t;
32 
33 struct timespec64 {
34 	time64_t	tv_sec;
35 	long int	tv_nsec;
36 };
37 
38 /* bpf-output associated map */
39 struct __augmented_syscalls__ {
40 	__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
41 	__type(key, int);
42 	__type(value, __u32);
43 	__uint(max_entries, MAX_CPUS);
44 } __augmented_syscalls__ SEC(".maps");
45 
46 /*
47  * What to augment at entry?
48  *
49  * Pointer arg payloads (filenames, etc) passed from userspace to the kernel
50  */
51 struct syscalls_sys_enter {
52 	__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
53 	__type(key, __u32);
54 	__type(value, __u32);
55 	__uint(max_entries, 512);
56 } syscalls_sys_enter SEC(".maps");
57 
58 /*
59  * What to augment at exit?
60  *
61  * Pointer arg payloads returned from the kernel (struct stat, etc) to userspace.
62  */
63 struct syscalls_sys_exit {
64 	__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
65 	__type(key, __u32);
66 	__type(value, __u32);
67 	__uint(max_entries, 512);
68 } syscalls_sys_exit SEC(".maps");
69 
70 struct syscall_enter_args {
71 	unsigned long long common_tp_fields;
72 	long		   syscall_nr;
73 	unsigned long	   args[6];
74 };
75 
76 struct syscall_exit_args {
77 	unsigned long long common_tp_fields;
78 	long		   syscall_nr;
79 	long		   ret;
80 };
81 
82 struct augmented_arg {
83 	unsigned int	size;
84 	int		err;
85 	char		value[PATH_MAX];
86 };
87 
88 struct pids_filtered {
89 	__uint(type, BPF_MAP_TYPE_HASH);
90 	__type(key, pid_t);
91 	__type(value, bool);
92 	__uint(max_entries, 64);
93 } pids_filtered SEC(".maps");
94 
95 /*
96  * Desired design of maximum size and alignment (see RFC2553)
97  */
98 #define SS_MAXSIZE   128     /* Implementation specific max size */
99 
100 typedef unsigned short sa_family_t;
101 
102 /*
103  * FIXME: Should come from system headers
104  *
105  * The definition uses anonymous union and struct in order to control the
106  * default alignment.
107  */
108 struct sockaddr_storage {
109 	union {
110 		struct {
111 			sa_family_t    ss_family; /* address family */
112 			/* Following field(s) are implementation specific */
113 			char __data[SS_MAXSIZE - sizeof(unsigned short)];
114 				/* space to achieve desired size, */
115 				/* _SS_MAXSIZE value minus size of ss_family */
116 		};
117 		void *__align; /* implementation specific desired alignment */
118 	};
119 };
120 
121 struct augmented_args_payload {
122        struct syscall_enter_args args;
123        union {
124 		struct {
125 			struct augmented_arg arg, arg2;
126 		};
127 		struct sockaddr_storage saddr;
128 		char   __data[sizeof(struct augmented_arg)];
129 	};
130 };
131 
132 // We need more tmp space than the BPF stack can give us
133 struct augmented_args_tmp {
134 	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
135 	__type(key, int);
136 	__type(value, struct augmented_args_payload);
137 	__uint(max_entries, 1);
138 } augmented_args_tmp SEC(".maps");
139 
140 static inline struct augmented_args_payload *augmented_args_payload(void)
141 {
142 	int key = 0;
143 	return bpf_map_lookup_elem(&augmented_args_tmp, &key);
144 }
145 
146 static inline int augmented__output(void *ctx, struct augmented_args_payload *args, int len)
147 {
148 	/* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */
149 	return bpf_perf_event_output(ctx, &__augmented_syscalls__, BPF_F_CURRENT_CPU, args, len);
150 }
151 
152 static inline
153 unsigned int augmented_arg__read_str(struct augmented_arg *augmented_arg, const void *arg, unsigned int arg_len)
154 {
155 	unsigned int augmented_len = sizeof(*augmented_arg);
156 	int string_len = bpf_probe_read_str(&augmented_arg->value, arg_len, arg);
157 
158 	augmented_arg->size = augmented_arg->err = 0;
159 	/*
160 	 * probe_read_str may return < 0, e.g. -EFAULT
161 	 * So we leave that in the augmented_arg->size that userspace will
162 	 */
163 	if (string_len > 0) {
164 		augmented_len -= sizeof(augmented_arg->value) - string_len;
165 		_Static_assert(is_power_of_2(sizeof(augmented_arg->value)), "sizeof(augmented_arg->value) needs to be a power of two");
166 		augmented_len &= sizeof(augmented_arg->value) - 1;
167 		augmented_arg->size = string_len;
168 	} else {
169 		/*
170 		 * So that username notice the error while still being able
171 		 * to skip this augmented arg record
172 		 */
173 		augmented_arg->err = string_len;
174 		augmented_len = offsetof(struct augmented_arg, value);
175 	}
176 
177 	return augmented_len;
178 }
179 
180 SEC("tp/raw_syscalls/sys_enter")
181 int syscall_unaugmented(struct syscall_enter_args *args)
182 {
183 	return 1;
184 }
185 
186 /*
187  * These will be tail_called from SEC("raw_syscalls:sys_enter"), so will find in
188  * augmented_args_tmp what was read by that raw_syscalls:sys_enter and go
189  * on from there, reading the first syscall arg as a string, i.e. open's
190  * filename.
191  */
192 SEC("tp/syscalls/sys_enter_connect")
193 int sys_enter_connect(struct syscall_enter_args *args)
194 {
195 	struct augmented_args_payload *augmented_args = augmented_args_payload();
196 	const void *sockaddr_arg = (const void *)args->args[1];
197 	unsigned int socklen = args->args[2];
198 	unsigned int len = sizeof(augmented_args->args);
199 
200         if (augmented_args == NULL)
201                 return 1; /* Failure: don't filter */
202 
203 	_Static_assert(is_power_of_2(sizeof(augmented_args->saddr)), "sizeof(augmented_args->saddr) needs to be a power of two");
204 	socklen &= sizeof(augmented_args->saddr) - 1;
205 
206 	bpf_probe_read(&augmented_args->saddr, socklen, sockaddr_arg);
207 
208 	return augmented__output(args, augmented_args, len + socklen);
209 }
210 
211 SEC("tp/syscalls/sys_enter_sendto")
212 int sys_enter_sendto(struct syscall_enter_args *args)
213 {
214 	struct augmented_args_payload *augmented_args = augmented_args_payload();
215 	const void *sockaddr_arg = (const void *)args->args[4];
216 	unsigned int socklen = args->args[5];
217 	unsigned int len = sizeof(augmented_args->args);
218 
219         if (augmented_args == NULL)
220                 return 1; /* Failure: don't filter */
221 
222 	socklen &= sizeof(augmented_args->saddr) - 1;
223 
224 	bpf_probe_read(&augmented_args->saddr, socklen, sockaddr_arg);
225 
226 	return augmented__output(args, augmented_args, len + socklen);
227 }
228 
229 SEC("tp/syscalls/sys_enter_open")
230 int sys_enter_open(struct syscall_enter_args *args)
231 {
232 	struct augmented_args_payload *augmented_args = augmented_args_payload();
233 	const void *filename_arg = (const void *)args->args[0];
234 	unsigned int len = sizeof(augmented_args->args);
235 
236         if (augmented_args == NULL)
237                 return 1; /* Failure: don't filter */
238 
239 	len += augmented_arg__read_str(&augmented_args->arg, filename_arg, sizeof(augmented_args->arg.value));
240 
241 	return augmented__output(args, augmented_args, len);
242 }
243 
244 SEC("tp/syscalls/sys_enter_openat")
245 int sys_enter_openat(struct syscall_enter_args *args)
246 {
247 	struct augmented_args_payload *augmented_args = augmented_args_payload();
248 	const void *filename_arg = (const void *)args->args[1];
249 	unsigned int len = sizeof(augmented_args->args);
250 
251         if (augmented_args == NULL)
252                 return 1; /* Failure: don't filter */
253 
254 	len += augmented_arg__read_str(&augmented_args->arg, filename_arg, sizeof(augmented_args->arg.value));
255 
256 	return augmented__output(args, augmented_args, len);
257 }
258 
259 SEC("tp/syscalls/sys_enter_rename")
260 int sys_enter_rename(struct syscall_enter_args *args)
261 {
262 	struct augmented_args_payload *augmented_args = augmented_args_payload();
263 	const void *oldpath_arg = (const void *)args->args[0],
264 		   *newpath_arg = (const void *)args->args[1];
265 	unsigned int len = sizeof(augmented_args->args), oldpath_len;
266 
267         if (augmented_args == NULL)
268                 return 1; /* Failure: don't filter */
269 
270 	oldpath_len = augmented_arg__read_str(&augmented_args->arg, oldpath_arg, sizeof(augmented_args->arg.value));
271 	len += oldpath_len + augmented_arg__read_str((void *)(&augmented_args->arg) + oldpath_len, newpath_arg, sizeof(augmented_args->arg.value));
272 
273 	return augmented__output(args, augmented_args, len);
274 }
275 
276 SEC("tp/syscalls/sys_enter_renameat")
277 int sys_enter_renameat(struct syscall_enter_args *args)
278 {
279 	struct augmented_args_payload *augmented_args = augmented_args_payload();
280 	const void *oldpath_arg = (const void *)args->args[1],
281 		   *newpath_arg = (const void *)args->args[3];
282 	unsigned int len = sizeof(augmented_args->args), oldpath_len;
283 
284         if (augmented_args == NULL)
285                 return 1; /* Failure: don't filter */
286 
287 	oldpath_len = augmented_arg__read_str(&augmented_args->arg, oldpath_arg, sizeof(augmented_args->arg.value));
288 	len += oldpath_len + augmented_arg__read_str((void *)(&augmented_args->arg) + oldpath_len, newpath_arg, sizeof(augmented_args->arg.value));
289 
290 	return augmented__output(args, augmented_args, len);
291 }
292 
293 #define PERF_ATTR_SIZE_VER0     64      /* sizeof first published struct */
294 
295 // we need just the start, get the size to then copy it
296 struct perf_event_attr_size {
297         __u32                   type;
298         /*
299          * Size of the attr structure, for fwd/bwd compat.
300          */
301         __u32                   size;
302 };
303 
304 SEC("tp/syscalls/sys_enter_perf_event_open")
305 int sys_enter_perf_event_open(struct syscall_enter_args *args)
306 {
307 	struct augmented_args_payload *augmented_args = augmented_args_payload();
308 	const struct perf_event_attr_size *attr = (const struct perf_event_attr_size *)args->args[0], *attr_read;
309 	unsigned int len = sizeof(augmented_args->args);
310 
311         if (augmented_args == NULL)
312 		goto failure;
313 
314 	if (bpf_probe_read(&augmented_args->__data, sizeof(*attr), attr) < 0)
315 		goto failure;
316 
317 	attr_read = (const struct perf_event_attr_size *)augmented_args->__data;
318 
319 	__u32 size = attr_read->size;
320 
321 	if (!size)
322 		size = PERF_ATTR_SIZE_VER0;
323 
324 	if (size > sizeof(augmented_args->__data))
325                 goto failure;
326 
327 	// Now that we read attr->size and tested it against the size limits, read it completely
328 	if (bpf_probe_read(&augmented_args->__data, size, attr) < 0)
329 		goto failure;
330 
331 	return augmented__output(args, augmented_args, len + size);
332 failure:
333 	return 1; /* Failure: don't filter */
334 }
335 
336 SEC("tp/syscalls/sys_enter_clock_nanosleep")
337 int sys_enter_clock_nanosleep(struct syscall_enter_args *args)
338 {
339 	struct augmented_args_payload *augmented_args = augmented_args_payload();
340 	const void *rqtp_arg = (const void *)args->args[2];
341 	unsigned int len = sizeof(augmented_args->args);
342 	__u32 size = sizeof(struct timespec64);
343 
344         if (augmented_args == NULL)
345 		goto failure;
346 
347 	if (size > sizeof(augmented_args->__data))
348                 goto failure;
349 
350 	bpf_probe_read(&augmented_args->__data, size, rqtp_arg);
351 
352 	return augmented__output(args, augmented_args, len + size);
353 failure:
354 	return 1; /* Failure: don't filter */
355 }
356 
357 static pid_t getpid(void)
358 {
359 	return bpf_get_current_pid_tgid();
360 }
361 
362 static bool pid_filter__has(struct pids_filtered *pids, pid_t pid)
363 {
364 	return bpf_map_lookup_elem(pids, &pid) != NULL;
365 }
366 
367 SEC("tp/raw_syscalls/sys_enter")
368 int sys_enter(struct syscall_enter_args *args)
369 {
370 	struct augmented_args_payload *augmented_args;
371 	/*
372 	 * We start len, the amount of data that will be in the perf ring
373 	 * buffer, if this is not filtered out by one of pid_filter__has(),
374 	 * syscall->enabled, etc, with the non-augmented raw syscall payload,
375 	 * i.e. sizeof(augmented_args->args).
376 	 *
377 	 * We'll add to this as we add augmented syscalls right after that
378 	 * initial, non-augmented raw_syscalls:sys_enter payload.
379 	 */
380 
381 	if (pid_filter__has(&pids_filtered, getpid()))
382 		return 0;
383 
384 	augmented_args = augmented_args_payload();
385 	if (augmented_args == NULL)
386 		return 1;
387 
388 	bpf_probe_read(&augmented_args->args, sizeof(augmented_args->args), args);
389 
390 	/*
391 	 * Jump to syscall specific augmenter, even if the default one,
392 	 * "!raw_syscalls:unaugmented" that will just return 1 to return the
393 	 * unaugmented tracepoint payload.
394 	 */
395 	bpf_tail_call(args, &syscalls_sys_enter, augmented_args->args.syscall_nr);
396 
397 	// If not found on the PROG_ARRAY syscalls map, then we're filtering it:
398 	return 0;
399 }
400 
401 SEC("tp/raw_syscalls/sys_exit")
402 int sys_exit(struct syscall_exit_args *args)
403 {
404 	struct syscall_exit_args exit_args;
405 
406 	if (pid_filter__has(&pids_filtered, getpid()))
407 		return 0;
408 
409 	bpf_probe_read(&exit_args, sizeof(exit_args), args);
410 	/*
411 	 * Jump to syscall specific return augmenter, even if the default one,
412 	 * "!raw_syscalls:unaugmented" that will just return 1 to return the
413 	 * unaugmented tracepoint payload.
414 	 */
415 	bpf_tail_call(args, &syscalls_sys_exit, exit_args.syscall_nr);
416 	/*
417 	 * If not found on the PROG_ARRAY syscalls map, then we're filtering it:
418 	 */
419 	return 0;
420 }
421 
422 char _license[] SEC("license") = "GPL";
423