1 // SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
2 /* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */
3 #include <ctype.h>
4 #include <stdio.h>
5 #include <stdlib.h>
6 #include <string.h>
7 #include <libelf.h>
8 #include <gelf.h>
9 #include <unistd.h>
10 #include <linux/ptrace.h>
11 #include <linux/kernel.h>
12
13 /* s8 will be marked as poison while it's a reg of riscv */
14 #if defined(__riscv)
15 #define rv_s8 s8
16 #endif
17
18 #include "bpf.h"
19 #include "libbpf.h"
20 #include "libbpf_common.h"
21 #include "libbpf_internal.h"
22 #include "hashmap.h"
23
24 /* libbpf's USDT support consists of BPF-side state/code and user-space
25 * state/code working together in concert. BPF-side parts are defined in
26 * usdt.bpf.h header library. User-space state is encapsulated by struct
27 * usdt_manager and all the supporting code centered around usdt_manager.
28 *
29 * usdt.bpf.h defines two BPF maps that usdt_manager expects: USDT spec map
30 * and IP-to-spec-ID map, which is auxiliary map necessary for kernels that
31 * don't support BPF cookie (see below). These two maps are implicitly
32 * embedded into user's end BPF object file when user's code included
33 * usdt.bpf.h. This means that libbpf doesn't do anything special to create
34 * these USDT support maps. They are created by normal libbpf logic of
35 * instantiating BPF maps when opening and loading BPF object.
36 *
37 * As such, libbpf is basically unaware of the need to do anything
38 * USDT-related until the very first call to bpf_program__attach_usdt(), which
39 * can be called by user explicitly or happen automatically during skeleton
40 * attach (or, equivalently, through generic bpf_program__attach() call). At
41 * this point, libbpf will instantiate and initialize struct usdt_manager and
42 * store it in bpf_object. USDT manager is per-BPF object construct, as each
43 * independent BPF object might or might not have USDT programs, and thus all
44 * the expected USDT-related state. There is no coordination between two
45 * bpf_object in parts of USDT attachment, they are oblivious of each other's
46 * existence and libbpf is just oblivious, dealing with bpf_object-specific
47 * USDT state.
48 *
49 * Quick crash course on USDTs.
50 *
51 * From user-space application's point of view, USDT is essentially just
52 * a slightly special function call that normally has zero overhead, unless it
53 * is being traced by some external entity (e.g, BPF-based tool). Here's how
54 * a typical application can trigger USDT probe:
55 *
56 * #include <sys/sdt.h> // provided by systemtap-sdt-devel package
57 * // folly also provide similar functionality in folly/tracing/StaticTracepoint.h
58 *
59 * STAP_PROBE3(my_usdt_provider, my_usdt_probe_name, 123, x, &y);
60 *
61 * USDT is identified by it's <provider-name>:<probe-name> pair of names. Each
62 * individual USDT has a fixed number of arguments (3 in the above example)
63 * and specifies values of each argument as if it was a function call.
64 *
65 * USDT call is actually not a function call, but is instead replaced by
66 * a single NOP instruction (thus zero overhead, effectively). But in addition
67 * to that, those USDT macros generate special SHT_NOTE ELF records in
68 * .note.stapsdt ELF section. Here's an example USDT definition as emitted by
69 * `readelf -n <binary>`:
70 *
71 * stapsdt 0x00000089 NT_STAPSDT (SystemTap probe descriptors)
72 * Provider: test
73 * Name: usdt12
74 * Location: 0x0000000000549df3, Base: 0x00000000008effa4, Semaphore: 0x0000000000a4606e
75 * Arguments: -4@-1204(%rbp) -4@%edi -8@-1216(%rbp) -8@%r8 -4@$5 -8@%r9 8@%rdx 8@%r10 -4@$-9 -2@%cx -2@%ax -1@%sil
76 *
77 * In this case we have USDT test:usdt12 with 12 arguments.
78 *
79 * Location and base are offsets used to calculate absolute IP address of that
80 * NOP instruction that kernel can replace with an interrupt instruction to
81 * trigger instrumentation code (BPF program for all that we care about).
82 *
83 * Semaphore above is and optional feature. It records an address of a 2-byte
84 * refcount variable (normally in '.probes' ELF section) used for signaling if
85 * there is anything that is attached to USDT. This is useful for user
86 * applications if, for example, they need to prepare some arguments that are
87 * passed only to USDTs and preparation is expensive. By checking if USDT is
88 * "activated", an application can avoid paying those costs unnecessarily.
89 * Recent enough kernel has built-in support for automatically managing this
90 * refcount, which libbpf expects and relies on. If USDT is defined without
91 * associated semaphore, this value will be zero. See selftests for semaphore
92 * examples.
93 *
94 * Arguments is the most interesting part. This USDT specification string is
95 * providing information about all the USDT arguments and their locations. The
96 * part before @ sign defined byte size of the argument (1, 2, 4, or 8) and
97 * whether the argument is signed or unsigned (negative size means signed).
98 * The part after @ sign is assembly-like definition of argument location
99 * (see [0] for more details). Technically, assembler can provide some pretty
100 * advanced definitions, but libbpf is currently supporting three most common
101 * cases:
102 * 1) immediate constant, see 5th and 9th args above (-4@$5 and -4@-9);
103 * 2) register value, e.g., 8@%rdx, which means "unsigned 8-byte integer
104 * whose value is in register %rdx";
105 * 3) memory dereference addressed by register, e.g., -4@-1204(%rbp), which
106 * specifies signed 32-bit integer stored at offset -1204 bytes from
107 * memory address stored in %rbp.
108 *
109 * [0] https://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation
110 *
111 * During attachment, libbpf parses all the relevant USDT specifications and
112 * prepares `struct usdt_spec` (USDT spec), which is then provided to BPF-side
113 * code through spec map. This allows BPF applications to quickly fetch the
114 * actual value at runtime using a simple BPF-side code.
115 *
116 * With basics out of the way, let's go over less immediately obvious aspects
117 * of supporting USDTs.
118 *
119 * First, there is no special USDT BPF program type. It is actually just
120 * a uprobe BPF program (which for kernel, at least currently, is just a kprobe
121 * program, so BPF_PROG_TYPE_KPROBE program type). With the only difference
122 * that uprobe is usually attached at the function entry, while USDT will
123 * normally will be somewhere inside the function. But it should always be
124 * pointing to NOP instruction, which makes such uprobes the fastest uprobe
125 * kind.
126 *
127 * Second, it's important to realize that such STAP_PROBEn(provider, name, ...)
128 * macro invocations can end up being inlined many-many times, depending on
129 * specifics of each individual user application. So single conceptual USDT
130 * (identified by provider:name pair of identifiers) is, generally speaking,
131 * multiple uprobe locations (USDT call sites) in different places in user
132 * application. Further, again due to inlining, each USDT call site might end
133 * up having the same argument #N be located in a different place. In one call
134 * site it could be a constant, in another will end up in a register, and in
135 * yet another could be some other register or even somewhere on the stack.
136 *
137 * As such, "attaching to USDT" means (in general case) attaching the same
138 * uprobe BPF program to multiple target locations in user application, each
139 * potentially having a completely different USDT spec associated with it.
140 * To wire all this up together libbpf allocates a unique integer spec ID for
141 * each unique USDT spec. Spec IDs are allocated as sequential small integers
142 * so that they can be used as keys in array BPF map (for performance reasons).
143 * Spec ID allocation and accounting is big part of what usdt_manager is
144 * about. This state has to be maintained per-BPF object and coordinate
145 * between different USDT attachments within the same BPF object.
146 *
147 * Spec ID is the key in spec BPF map, value is the actual USDT spec layed out
148 * as struct usdt_spec. Each invocation of BPF program at runtime needs to
149 * know its associated spec ID. It gets it either through BPF cookie, which
150 * libbpf sets to spec ID during attach time, or, if kernel is too old to
151 * support BPF cookie, through IP-to-spec-ID map that libbpf maintains in such
152 * case. The latter means that some modes of operation can't be supported
153 * without BPF cookie. Such mode is attaching to shared library "generically",
154 * without specifying target process. In such case, it's impossible to
155 * calculate absolute IP addresses for IP-to-spec-ID map, and thus such mode
156 * is not supported without BPF cookie support.
157 *
158 * Note that libbpf is using BPF cookie functionality for its own internal
159 * needs, so user itself can't rely on BPF cookie feature. To that end, libbpf
160 * provides conceptually equivalent USDT cookie support. It's still u64
161 * user-provided value that can be associated with USDT attachment. Note that
162 * this will be the same value for all USDT call sites within the same single
163 * *logical* USDT attachment. This makes sense because to user attaching to
164 * USDT is a single BPF program triggered for singular USDT probe. The fact
165 * that this is done at multiple actual locations is a mostly hidden
166 * implementation details. This USDT cookie value can be fetched with
167 * bpf_usdt_cookie(ctx) API provided by usdt.bpf.h
168 *
169 * Lastly, while single USDT can have tons of USDT call sites, it doesn't
170 * necessarily have that many different USDT specs. It very well might be
171 * that 1000 USDT call sites only need 5 different USDT specs, because all the
172 * arguments are typically contained in a small set of registers or stack
173 * locations. As such, it's wasteful to allocate as many USDT spec IDs as
174 * there are USDT call sites. So libbpf tries to be frugal and performs
175 * on-the-fly deduplication during a single USDT attachment to only allocate
176 * the minimal required amount of unique USDT specs (and thus spec IDs). This
177 * is trivially achieved by using USDT spec string (Arguments string from USDT
178 * note) as a lookup key in a hashmap. USDT spec string uniquely defines
179 * everything about how to fetch USDT arguments, so two USDT call sites
180 * sharing USDT spec string can safely share the same USDT spec and spec ID.
181 * Note, this spec string deduplication is happening only during the same USDT
182 * attachment, so each USDT spec shares the same USDT cookie value. This is
183 * not generally true for other USDT attachments within the same BPF object,
184 * as even if USDT spec string is the same, USDT cookie value can be
185 * different. It was deemed excessive to try to deduplicate across independent
186 * USDT attachments by taking into account USDT spec string *and* USDT cookie
187 * value, which would complicated spec ID accounting significantly for little
188 * gain.
189 */
190
191 #define USDT_BASE_SEC ".stapsdt.base"
192 #define USDT_SEMA_SEC ".probes"
193 #define USDT_NOTE_SEC ".note.stapsdt"
194 #define USDT_NOTE_TYPE 3
195 #define USDT_NOTE_NAME "stapsdt"
196
197 /* should match exactly enum __bpf_usdt_arg_type from usdt.bpf.h */
198 enum usdt_arg_type {
199 USDT_ARG_CONST,
200 USDT_ARG_REG,
201 USDT_ARG_REG_DEREF,
202 };
203
204 /* should match exactly struct __bpf_usdt_arg_spec from usdt.bpf.h */
205 struct usdt_arg_spec {
206 __u64 val_off;
207 enum usdt_arg_type arg_type;
208 short reg_off;
209 bool arg_signed;
210 char arg_bitshift;
211 };
212
213 /* should match BPF_USDT_MAX_ARG_CNT in usdt.bpf.h */
214 #define USDT_MAX_ARG_CNT 12
215
216 /* should match struct __bpf_usdt_spec from usdt.bpf.h */
217 struct usdt_spec {
218 struct usdt_arg_spec args[USDT_MAX_ARG_CNT];
219 __u64 usdt_cookie;
220 short arg_cnt;
221 };
222
223 struct usdt_note {
224 const char *provider;
225 const char *name;
226 /* USDT args specification string, e.g.:
227 * "-4@%esi -4@-24(%rbp) -4@%ecx 2@%ax 8@%rdx"
228 */
229 const char *args;
230 long loc_addr;
231 long base_addr;
232 long sema_addr;
233 };
234
235 struct usdt_target {
236 long abs_ip;
237 long rel_ip;
238 long sema_off;
239 struct usdt_spec spec;
240 const char *spec_str;
241 };
242
243 struct usdt_manager {
244 struct bpf_map *specs_map;
245 struct bpf_map *ip_to_spec_id_map;
246
247 int *free_spec_ids;
248 size_t free_spec_cnt;
249 size_t next_free_spec_id;
250
251 bool has_bpf_cookie;
252 bool has_sema_refcnt;
253 bool has_uprobe_multi;
254 };
255
256 struct usdt_manager *usdt_manager_new(struct bpf_object *obj)
257 {
258 static const char *ref_ctr_sysfs_path = "/sys/bus/event_source/devices/uprobe/format/ref_ctr_offset";
259 struct usdt_manager *man;
260 struct bpf_map *specs_map, *ip_to_spec_id_map;
261
262 specs_map = bpf_object__find_map_by_name(obj, "__bpf_usdt_specs");
263 ip_to_spec_id_map = bpf_object__find_map_by_name(obj, "__bpf_usdt_ip_to_spec_id");
264 if (!specs_map || !ip_to_spec_id_map) {
265 pr_warn("usdt: failed to find USDT support BPF maps, did you forget to include bpf/usdt.bpf.h?\n");
266 return ERR_PTR(-ESRCH);
267 }
268
269 man = calloc(1, sizeof(*man));
270 if (!man)
271 return ERR_PTR(-ENOMEM);
272
273 man->specs_map = specs_map;
274 man->ip_to_spec_id_map = ip_to_spec_id_map;
275
276 /* Detect if BPF cookie is supported for kprobes.
277 * We don't need IP-to-ID mapping if we can use BPF cookies.
278 * Added in: 7adfc6c9b315 ("bpf: Add bpf_get_attach_cookie() BPF helper to access bpf_cookie value")
279 */
280 man->has_bpf_cookie = kernel_supports(obj, FEAT_BPF_COOKIE);
281
282 /* Detect kernel support for automatic refcounting of USDT semaphore.
283 * If this is not supported, USDTs with semaphores will not be supported.
284 * Added in: a6ca88b241d5 ("trace_uprobe: support reference counter in fd-based uprobe")
285 */
286 man->has_sema_refcnt = faccessat(AT_FDCWD, ref_ctr_sysfs_path, F_OK, AT_EACCESS) == 0;
287
288 /*
289 * Detect kernel support for uprobe multi link to be used for attaching
290 * usdt probes.
291 */
292 man->has_uprobe_multi = kernel_supports(obj, FEAT_UPROBE_MULTI_LINK);
293 return man;
294 }
295
296 void usdt_manager_free(struct usdt_manager *man)
297 {
298 if (IS_ERR_OR_NULL(man))
299 return;
300
301 free(man->free_spec_ids);
302 free(man);
303 }
304
305 static int sanity_check_usdt_elf(Elf *elf, const char *path)
306 {
307 GElf_Ehdr ehdr;
308 int endianness;
309
310 if (elf_kind(elf) != ELF_K_ELF) {
311 pr_warn("usdt: unrecognized ELF kind %d for '%s'\n", elf_kind(elf), path);
312 return -EBADF;
313 }
314
315 switch (gelf_getclass(elf)) {
316 case ELFCLASS64:
317 if (sizeof(void *) != 8) {
318 pr_warn("usdt: attaching to 64-bit ELF binary '%s' is not supported\n", path);
319 return -EBADF;
320 }
321 break;
322 case ELFCLASS32:
323 if (sizeof(void *) != 4) {
324 pr_warn("usdt: attaching to 32-bit ELF binary '%s' is not supported\n", path);
325 return -EBADF;
326 }
327 break;
328 default:
329 pr_warn("usdt: unsupported ELF class for '%s'\n", path);
330 return -EBADF;
331 }
332
333 if (!gelf_getehdr(elf, &ehdr))
334 return -EINVAL;
335
336 if (ehdr.e_type != ET_EXEC && ehdr.e_type != ET_DYN) {
337 pr_warn("usdt: unsupported type of ELF binary '%s' (%d), only ET_EXEC and ET_DYN are supported\n",
338 path, ehdr.e_type);
339 return -EBADF;
340 }
341
342 #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
343 endianness = ELFDATA2LSB;
344 #elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
345 endianness = ELFDATA2MSB;
346 #else
347 # error "Unrecognized __BYTE_ORDER__"
348 #endif
349 if (endianness != ehdr.e_ident[EI_DATA]) {
350 pr_warn("usdt: ELF endianness mismatch for '%s'\n", path);
351 return -EBADF;
352 }
353
354 return 0;
355 }
356
357 static int find_elf_sec_by_name(Elf *elf, const char *sec_name, GElf_Shdr *shdr, Elf_Scn **scn)
358 {
359 Elf_Scn *sec = NULL;
360 size_t shstrndx;
361
362 if (elf_getshdrstrndx(elf, &shstrndx))
363 return -EINVAL;
364
365 /* check if ELF is corrupted and avoid calling elf_strptr if yes */
366 if (!elf_rawdata(elf_getscn(elf, shstrndx), NULL))
367 return -EINVAL;
368
369 while ((sec = elf_nextscn(elf, sec)) != NULL) {
370 char *name;
371
372 if (!gelf_getshdr(sec, shdr))
373 return -EINVAL;
374
375 name = elf_strptr(elf, shstrndx, shdr->sh_name);
376 if (name && strcmp(sec_name, name) == 0) {
377 *scn = sec;
378 return 0;
379 }
380 }
381
382 return -ENOENT;
383 }
384
385 struct elf_seg {
386 long start;
387 long end;
388 long offset;
389 bool is_exec;
390 };
391
392 static int cmp_elf_segs(const void *_a, const void *_b)
393 {
394 const struct elf_seg *a = _a;
395 const struct elf_seg *b = _b;
396
397 return a->start < b->start ? -1 : 1;
398 }
399
400 static int parse_elf_segs(Elf *elf, const char *path, struct elf_seg **segs, size_t *seg_cnt)
401 {
402 GElf_Phdr phdr;
403 size_t n;
404 int i, err;
405 struct elf_seg *seg;
406 void *tmp;
407
408 *seg_cnt = 0;
409
410 if (elf_getphdrnum(elf, &n)) {
411 err = -errno;
412 return err;
413 }
414
415 for (i = 0; i < n; i++) {
416 if (!gelf_getphdr(elf, i, &phdr)) {
417 err = -errno;
418 return err;
419 }
420
421 pr_debug("usdt: discovered PHDR #%d in '%s': vaddr 0x%lx memsz 0x%lx offset 0x%lx type 0x%lx flags 0x%lx\n",
422 i, path, (long)phdr.p_vaddr, (long)phdr.p_memsz, (long)phdr.p_offset,
423 (long)phdr.p_type, (long)phdr.p_flags);
424 if (phdr.p_type != PT_LOAD)
425 continue;
426
427 tmp = libbpf_reallocarray(*segs, *seg_cnt + 1, sizeof(**segs));
428 if (!tmp)
429 return -ENOMEM;
430
431 *segs = tmp;
432 seg = *segs + *seg_cnt;
433 (*seg_cnt)++;
434
435 seg->start = phdr.p_vaddr;
436 seg->end = phdr.p_vaddr + phdr.p_memsz;
437 seg->offset = phdr.p_offset;
438 seg->is_exec = phdr.p_flags & PF_X;
439 }
440
441 if (*seg_cnt == 0) {
442 pr_warn("usdt: failed to find PT_LOAD program headers in '%s'\n", path);
443 return -ESRCH;
444 }
445
446 qsort(*segs, *seg_cnt, sizeof(**segs), cmp_elf_segs);
447 return 0;
448 }
449
450 static int parse_vma_segs(int pid, const char *lib_path, struct elf_seg **segs, size_t *seg_cnt)
451 {
452 char path[PATH_MAX], line[PATH_MAX], mode[16];
453 size_t seg_start, seg_end, seg_off;
454 struct elf_seg *seg;
455 int tmp_pid, i, err;
456 FILE *f;
457
458 *seg_cnt = 0;
459
460 /* Handle containerized binaries only accessible from
461 * /proc/<pid>/root/<path>. They will be reported as just /<path> in
462 * /proc/<pid>/maps.
463 */
464 if (sscanf(lib_path, "/proc/%d/root%s", &tmp_pid, path) == 2 && pid == tmp_pid)
465 goto proceed;
466
467 if (!realpath(lib_path, path)) {
468 pr_warn("usdt: failed to get absolute path of '%s' (err %d), using path as is...\n",
469 lib_path, -errno);
470 libbpf_strlcpy(path, lib_path, sizeof(path));
471 }
472
473 proceed:
474 sprintf(line, "/proc/%d/maps", pid);
475 f = fopen(line, "re");
476 if (!f) {
477 err = -errno;
478 pr_warn("usdt: failed to open '%s' to get base addr of '%s': %d\n",
479 line, lib_path, err);
480 return err;
481 }
482
483 /* We need to handle lines with no path at the end:
484 *
485 * 7f5c6f5d1000-7f5c6f5d3000 rw-p 001c7000 08:04 21238613 /usr/lib64/libc-2.17.so
486 * 7f5c6f5d3000-7f5c6f5d8000 rw-p 00000000 00:00 0
487 * 7f5c6f5d8000-7f5c6f5d9000 r-xp 00000000 103:01 362990598 /data/users/andriin/linux/tools/bpf/usdt/libhello_usdt.so
488 */
489 while (fscanf(f, "%zx-%zx %s %zx %*s %*d%[^\n]\n",
490 &seg_start, &seg_end, mode, &seg_off, line) == 5) {
491 void *tmp;
492
493 /* to handle no path case (see above) we need to capture line
494 * without skipping any whitespaces. So we need to strip
495 * leading whitespaces manually here
496 */
497 i = 0;
498 while (isblank(line[i]))
499 i++;
500 if (strcmp(line + i, path) != 0)
501 continue;
502
503 pr_debug("usdt: discovered segment for lib '%s': addrs %zx-%zx mode %s offset %zx\n",
504 path, seg_start, seg_end, mode, seg_off);
505
506 /* ignore non-executable sections for shared libs */
507 if (mode[2] != 'x')
508 continue;
509
510 tmp = libbpf_reallocarray(*segs, *seg_cnt + 1, sizeof(**segs));
511 if (!tmp) {
512 err = -ENOMEM;
513 goto err_out;
514 }
515
516 *segs = tmp;
517 seg = *segs + *seg_cnt;
518 *seg_cnt += 1;
519
520 seg->start = seg_start;
521 seg->end = seg_end;
522 seg->offset = seg_off;
523 seg->is_exec = true;
524 }
525
526 if (*seg_cnt == 0) {
527 pr_warn("usdt: failed to find '%s' (resolved to '%s') within PID %d memory mappings\n",
528 lib_path, path, pid);
529 err = -ESRCH;
530 goto err_out;
531 }
532
533 qsort(*segs, *seg_cnt, sizeof(**segs), cmp_elf_segs);
534 err = 0;
535 err_out:
536 fclose(f);
537 return err;
538 }
539
540 static struct elf_seg *find_elf_seg(struct elf_seg *segs, size_t seg_cnt, long virtaddr)
541 {
542 struct elf_seg *seg;
543 int i;
544
545 /* for ELF binaries (both executables and shared libraries), we are
546 * given virtual address (absolute for executables, relative for
547 * libraries) which should match address range of [seg_start, seg_end)
548 */
549 for (i = 0, seg = segs; i < seg_cnt; i++, seg++) {
550 if (seg->start <= virtaddr && virtaddr < seg->end)
551 return seg;
552 }
553 return NULL;
554 }
555
556 static struct elf_seg *find_vma_seg(struct elf_seg *segs, size_t seg_cnt, long offset)
557 {
558 struct elf_seg *seg;
559 int i;
560
561 /* for VMA segments from /proc/<pid>/maps file, provided "address" is
562 * actually a file offset, so should be fall within logical
563 * offset-based range of [offset_start, offset_end)
564 */
565 for (i = 0, seg = segs; i < seg_cnt; i++, seg++) {
566 if (seg->offset <= offset && offset < seg->offset + (seg->end - seg->start))
567 return seg;
568 }
569 return NULL;
570 }
571
572 static int parse_usdt_note(Elf *elf, const char *path, GElf_Nhdr *nhdr,
573 const char *data, size_t name_off, size_t desc_off,
574 struct usdt_note *usdt_note);
575
576 static int parse_usdt_spec(struct usdt_spec *spec, const struct usdt_note *note, __u64 usdt_cookie);
577
578 static int collect_usdt_targets(struct usdt_manager *man, Elf *elf, const char *path, pid_t pid,
579 const char *usdt_provider, const char *usdt_name, __u64 usdt_cookie,
580 struct usdt_target **out_targets, size_t *out_target_cnt)
581 {
582 size_t off, name_off, desc_off, seg_cnt = 0, vma_seg_cnt = 0, target_cnt = 0;
583 struct elf_seg *segs = NULL, *vma_segs = NULL;
584 struct usdt_target *targets = NULL, *target;
585 long base_addr = 0;
586 Elf_Scn *notes_scn, *base_scn;
587 GElf_Shdr base_shdr, notes_shdr;
588 GElf_Ehdr ehdr;
589 GElf_Nhdr nhdr;
590 Elf_Data *data;
591 int err;
592
593 *out_targets = NULL;
594 *out_target_cnt = 0;
595
596 err = find_elf_sec_by_name(elf, USDT_NOTE_SEC, ¬es_shdr, ¬es_scn);
597 if (err) {
598 pr_warn("usdt: no USDT notes section (%s) found in '%s'\n", USDT_NOTE_SEC, path);
599 return err;
600 }
601
602 if (notes_shdr.sh_type != SHT_NOTE || !gelf_getehdr(elf, &ehdr)) {
603 pr_warn("usdt: invalid USDT notes section (%s) in '%s'\n", USDT_NOTE_SEC, path);
604 return -EINVAL;
605 }
606
607 err = parse_elf_segs(elf, path, &segs, &seg_cnt);
608 if (err) {
609 pr_warn("usdt: failed to process ELF program segments for '%s': %d\n", path, err);
610 goto err_out;
611 }
612
613 /* .stapsdt.base ELF section is optional, but is used for prelink
614 * offset compensation (see a big comment further below)
615 */
616 if (find_elf_sec_by_name(elf, USDT_BASE_SEC, &base_shdr, &base_scn) == 0)
617 base_addr = base_shdr.sh_addr;
618
619 data = elf_getdata(notes_scn, 0);
620 off = 0;
621 while ((off = gelf_getnote(data, off, &nhdr, &name_off, &desc_off)) > 0) {
622 long usdt_abs_ip, usdt_rel_ip, usdt_sema_off = 0;
623 struct usdt_note note;
624 struct elf_seg *seg = NULL;
625 void *tmp;
626
627 err = parse_usdt_note(elf, path, &nhdr, data->d_buf, name_off, desc_off, ¬e);
628 if (err)
629 goto err_out;
630
631 if (strcmp(note.provider, usdt_provider) != 0 || strcmp(note.name, usdt_name) != 0)
632 continue;
633
634 /* We need to compensate "prelink effect". See [0] for details,
635 * relevant parts quoted here:
636 *
637 * Each SDT probe also expands into a non-allocated ELF note. You can
638 * find this by looking at SHT_NOTE sections and decoding the format;
639 * see below for details. Because the note is non-allocated, it means
640 * there is no runtime cost, and also preserved in both stripped files
641 * and .debug files.
642 *
643 * However, this means that prelink won't adjust the note's contents
644 * for address offsets. Instead, this is done via the .stapsdt.base
645 * section. This is a special section that is added to the text. We
646 * will only ever have one of these sections in a final link and it
647 * will only ever be one byte long. Nothing about this section itself
648 * matters, we just use it as a marker to detect prelink address
649 * adjustments.
650 *
651 * Each probe note records the link-time address of the .stapsdt.base
652 * section alongside the probe PC address. The decoder compares the
653 * base address stored in the note with the .stapsdt.base section's
654 * sh_addr. Initially these are the same, but the section header will
655 * be adjusted by prelink. So the decoder applies the difference to
656 * the probe PC address to get the correct prelinked PC address; the
657 * same adjustment is applied to the semaphore address, if any.
658 *
659 * [0] https://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation
660 */
661 usdt_abs_ip = note.loc_addr;
662 if (base_addr)
663 usdt_abs_ip += base_addr - note.base_addr;
664
665 /* When attaching uprobes (which is what USDTs basically are)
666 * kernel expects file offset to be specified, not a relative
667 * virtual address, so we need to translate virtual address to
668 * file offset, for both ET_EXEC and ET_DYN binaries.
669 */
670 seg = find_elf_seg(segs, seg_cnt, usdt_abs_ip);
671 if (!seg) {
672 err = -ESRCH;
673 pr_warn("usdt: failed to find ELF program segment for '%s:%s' in '%s' at IP 0x%lx\n",
674 usdt_provider, usdt_name, path, usdt_abs_ip);
675 goto err_out;
676 }
677 if (!seg->is_exec) {
678 err = -ESRCH;
679 pr_warn("usdt: matched ELF binary '%s' segment [0x%lx, 0x%lx) for '%s:%s' at IP 0x%lx is not executable\n",
680 path, seg->start, seg->end, usdt_provider, usdt_name,
681 usdt_abs_ip);
682 goto err_out;
683 }
684 /* translate from virtual address to file offset */
685 usdt_rel_ip = usdt_abs_ip - seg->start + seg->offset;
686
687 if (ehdr.e_type == ET_DYN && !man->has_bpf_cookie) {
688 /* If we don't have BPF cookie support but need to
689 * attach to a shared library, we'll need to know and
690 * record absolute addresses of attach points due to
691 * the need to lookup USDT spec by absolute IP of
692 * triggered uprobe. Doing this resolution is only
693 * possible when we have a specific PID of the process
694 * that's using specified shared library. BPF cookie
695 * removes the absolute address limitation as we don't
696 * need to do this lookup (we just use BPF cookie as
697 * an index of USDT spec), so for newer kernels with
698 * BPF cookie support libbpf supports USDT attachment
699 * to shared libraries with no PID filter.
700 */
701 if (pid < 0) {
702 pr_warn("usdt: attaching to shared libraries without specific PID is not supported on current kernel\n");
703 err = -ENOTSUP;
704 goto err_out;
705 }
706
707 /* vma_segs are lazily initialized only if necessary */
708 if (vma_seg_cnt == 0) {
709 err = parse_vma_segs(pid, path, &vma_segs, &vma_seg_cnt);
710 if (err) {
711 pr_warn("usdt: failed to get memory segments in PID %d for shared library '%s': %d\n",
712 pid, path, err);
713 goto err_out;
714 }
715 }
716
717 seg = find_vma_seg(vma_segs, vma_seg_cnt, usdt_rel_ip);
718 if (!seg) {
719 err = -ESRCH;
720 pr_warn("usdt: failed to find shared lib memory segment for '%s:%s' in '%s' at relative IP 0x%lx\n",
721 usdt_provider, usdt_name, path, usdt_rel_ip);
722 goto err_out;
723 }
724
725 usdt_abs_ip = seg->start - seg->offset + usdt_rel_ip;
726 }
727
728 pr_debug("usdt: probe for '%s:%s' in %s '%s': addr 0x%lx base 0x%lx (resolved abs_ip 0x%lx rel_ip 0x%lx) args '%s' in segment [0x%lx, 0x%lx) at offset 0x%lx\n",
729 usdt_provider, usdt_name, ehdr.e_type == ET_EXEC ? "exec" : "lib ", path,
730 note.loc_addr, note.base_addr, usdt_abs_ip, usdt_rel_ip, note.args,
731 seg ? seg->start : 0, seg ? seg->end : 0, seg ? seg->offset : 0);
732
733 /* Adjust semaphore address to be a file offset */
734 if (note.sema_addr) {
735 if (!man->has_sema_refcnt) {
736 pr_warn("usdt: kernel doesn't support USDT semaphore refcounting for '%s:%s' in '%s'\n",
737 usdt_provider, usdt_name, path);
738 err = -ENOTSUP;
739 goto err_out;
740 }
741
742 seg = find_elf_seg(segs, seg_cnt, note.sema_addr);
743 if (!seg) {
744 err = -ESRCH;
745 pr_warn("usdt: failed to find ELF loadable segment with semaphore of '%s:%s' in '%s' at 0x%lx\n",
746 usdt_provider, usdt_name, path, note.sema_addr);
747 goto err_out;
748 }
749 if (seg->is_exec) {
750 err = -ESRCH;
751 pr_warn("usdt: matched ELF binary '%s' segment [0x%lx, 0x%lx] for semaphore of '%s:%s' at 0x%lx is executable\n",
752 path, seg->start, seg->end, usdt_provider, usdt_name,
753 note.sema_addr);
754 goto err_out;
755 }
756
757 usdt_sema_off = note.sema_addr - seg->start + seg->offset;
758
759 pr_debug("usdt: sema for '%s:%s' in %s '%s': addr 0x%lx base 0x%lx (resolved 0x%lx) in segment [0x%lx, 0x%lx] at offset 0x%lx\n",
760 usdt_provider, usdt_name, ehdr.e_type == ET_EXEC ? "exec" : "lib ",
761 path, note.sema_addr, note.base_addr, usdt_sema_off,
762 seg->start, seg->end, seg->offset);
763 }
764
765 /* Record adjusted addresses and offsets and parse USDT spec */
766 tmp = libbpf_reallocarray(targets, target_cnt + 1, sizeof(*targets));
767 if (!tmp) {
768 err = -ENOMEM;
769 goto err_out;
770 }
771 targets = tmp;
772
773 target = &targets[target_cnt];
774 memset(target, 0, sizeof(*target));
775
776 target->abs_ip = usdt_abs_ip;
777 target->rel_ip = usdt_rel_ip;
778 target->sema_off = usdt_sema_off;
779
780 /* notes.args references strings from ELF itself, so they can
781 * be referenced safely until elf_end() call
782 */
783 target->spec_str = note.args;
784
785 err = parse_usdt_spec(&target->spec, ¬e, usdt_cookie);
786 if (err)
787 goto err_out;
788
789 target_cnt++;
790 }
791
792 *out_targets = targets;
793 *out_target_cnt = target_cnt;
794 err = target_cnt;
795
796 err_out:
797 free(segs);
798 free(vma_segs);
799 if (err < 0)
800 free(targets);
801 return err;
802 }
803
804 struct bpf_link_usdt {
805 struct bpf_link link;
806
807 struct usdt_manager *usdt_man;
808
809 size_t spec_cnt;
810 int *spec_ids;
811
812 size_t uprobe_cnt;
813 struct {
814 long abs_ip;
815 struct bpf_link *link;
816 } *uprobes;
817
818 struct bpf_link *multi_link;
819 };
820
821 static int bpf_link_usdt_detach(struct bpf_link *link)
822 {
823 struct bpf_link_usdt *usdt_link = container_of(link, struct bpf_link_usdt, link);
824 struct usdt_manager *man = usdt_link->usdt_man;
825 int i;
826
827 bpf_link__destroy(usdt_link->multi_link);
828
829 /* When having multi_link, uprobe_cnt is 0 */
830 for (i = 0; i < usdt_link->uprobe_cnt; i++) {
831 /* detach underlying uprobe link */
832 bpf_link__destroy(usdt_link->uprobes[i].link);
833 /* there is no need to update specs map because it will be
834 * unconditionally overwritten on subsequent USDT attaches,
835 * but if BPF cookies are not used we need to remove entry
836 * from ip_to_spec_id map, otherwise we'll run into false
837 * conflicting IP errors
838 */
839 if (!man->has_bpf_cookie) {
840 /* not much we can do about errors here */
841 (void)bpf_map_delete_elem(bpf_map__fd(man->ip_to_spec_id_map),
842 &usdt_link->uprobes[i].abs_ip);
843 }
844 }
845
846 /* try to return the list of previously used spec IDs to usdt_manager
847 * for future reuse for subsequent USDT attaches
848 */
849 if (!man->free_spec_ids) {
850 /* if there were no free spec IDs yet, just transfer our IDs */
851 man->free_spec_ids = usdt_link->spec_ids;
852 man->free_spec_cnt = usdt_link->spec_cnt;
853 usdt_link->spec_ids = NULL;
854 } else {
855 /* otherwise concat IDs */
856 size_t new_cnt = man->free_spec_cnt + usdt_link->spec_cnt;
857 int *new_free_ids;
858
859 new_free_ids = libbpf_reallocarray(man->free_spec_ids, new_cnt,
860 sizeof(*new_free_ids));
861 /* If we couldn't resize free_spec_ids, we'll just leak
862 * a bunch of free IDs; this is very unlikely to happen and if
863 * system is so exhausted on memory, it's the least of user's
864 * concerns, probably.
865 * So just do our best here to return those IDs to usdt_manager.
866 * Another edge case when we can legitimately get NULL is when
867 * new_cnt is zero, which can happen in some edge cases, so we
868 * need to be careful about that.
869 */
870 if (new_free_ids || new_cnt == 0) {
871 memcpy(new_free_ids + man->free_spec_cnt, usdt_link->spec_ids,
872 usdt_link->spec_cnt * sizeof(*usdt_link->spec_ids));
873 man->free_spec_ids = new_free_ids;
874 man->free_spec_cnt = new_cnt;
875 }
876 }
877
878 return 0;
879 }
880
881 static void bpf_link_usdt_dealloc(struct bpf_link *link)
882 {
883 struct bpf_link_usdt *usdt_link = container_of(link, struct bpf_link_usdt, link);
884
885 free(usdt_link->spec_ids);
886 free(usdt_link->uprobes);
887 free(usdt_link);
888 }
889
890 static size_t specs_hash_fn(long key, void *ctx)
891 {
892 return str_hash((char *)key);
893 }
894
895 static bool specs_equal_fn(long key1, long key2, void *ctx)
896 {
897 return strcmp((char *)key1, (char *)key2) == 0;
898 }
899
900 static int allocate_spec_id(struct usdt_manager *man, struct hashmap *specs_hash,
901 struct bpf_link_usdt *link, struct usdt_target *target,
902 int *spec_id, bool *is_new)
903 {
904 long tmp;
905 void *new_ids;
906 int err;
907
908 /* check if we already allocated spec ID for this spec string */
909 if (hashmap__find(specs_hash, target->spec_str, &tmp)) {
910 *spec_id = tmp;
911 *is_new = false;
912 return 0;
913 }
914
915 /* otherwise it's a new ID that needs to be set up in specs map and
916 * returned back to usdt_manager when USDT link is detached
917 */
918 new_ids = libbpf_reallocarray(link->spec_ids, link->spec_cnt + 1, sizeof(*link->spec_ids));
919 if (!new_ids)
920 return -ENOMEM;
921 link->spec_ids = new_ids;
922
923 /* get next free spec ID, giving preference to free list, if not empty */
924 if (man->free_spec_cnt) {
925 *spec_id = man->free_spec_ids[man->free_spec_cnt - 1];
926
927 /* cache spec ID for current spec string for future lookups */
928 err = hashmap__add(specs_hash, target->spec_str, *spec_id);
929 if (err)
930 return err;
931
932 man->free_spec_cnt--;
933 } else {
934 /* don't allocate spec ID bigger than what fits in specs map */
935 if (man->next_free_spec_id >= bpf_map__max_entries(man->specs_map))
936 return -E2BIG;
937
938 *spec_id = man->next_free_spec_id;
939
940 /* cache spec ID for current spec string for future lookups */
941 err = hashmap__add(specs_hash, target->spec_str, *spec_id);
942 if (err)
943 return err;
944
945 man->next_free_spec_id++;
946 }
947
948 /* remember new spec ID in the link for later return back to free list on detach */
949 link->spec_ids[link->spec_cnt] = *spec_id;
950 link->spec_cnt++;
951 *is_new = true;
952 return 0;
953 }
954
955 struct bpf_link *usdt_manager_attach_usdt(struct usdt_manager *man, const struct bpf_program *prog,
956 pid_t pid, const char *path,
957 const char *usdt_provider, const char *usdt_name,
958 __u64 usdt_cookie)
959 {
960 unsigned long *offsets = NULL, *ref_ctr_offsets = NULL;
961 int i, err, spec_map_fd, ip_map_fd;
962 LIBBPF_OPTS(bpf_uprobe_opts, opts);
963 struct hashmap *specs_hash = NULL;
964 struct bpf_link_usdt *link = NULL;
965 struct usdt_target *targets = NULL;
966 __u64 *cookies = NULL;
967 struct elf_fd elf_fd;
968 size_t target_cnt;
969
970 spec_map_fd = bpf_map__fd(man->specs_map);
971 ip_map_fd = bpf_map__fd(man->ip_to_spec_id_map);
972
973 err = elf_open(path, &elf_fd);
974 if (err)
975 return libbpf_err_ptr(err);
976
977 err = sanity_check_usdt_elf(elf_fd.elf, path);
978 if (err)
979 goto err_out;
980
981 /* normalize PID filter */
982 if (pid < 0)
983 pid = -1;
984 else if (pid == 0)
985 pid = getpid();
986
987 /* discover USDT in given binary, optionally limiting
988 * activations to a given PID, if pid > 0
989 */
990 err = collect_usdt_targets(man, elf_fd.elf, path, pid, usdt_provider, usdt_name,
991 usdt_cookie, &targets, &target_cnt);
992 if (err <= 0) {
993 err = (err == 0) ? -ENOENT : err;
994 goto err_out;
995 }
996
997 specs_hash = hashmap__new(specs_hash_fn, specs_equal_fn, NULL);
998 if (IS_ERR(specs_hash)) {
999 err = PTR_ERR(specs_hash);
1000 goto err_out;
1001 }
1002
1003 link = calloc(1, sizeof(*link));
1004 if (!link) {
1005 err = -ENOMEM;
1006 goto err_out;
1007 }
1008
1009 link->usdt_man = man;
1010 link->link.detach = &bpf_link_usdt_detach;
1011 link->link.dealloc = &bpf_link_usdt_dealloc;
1012
1013 if (man->has_uprobe_multi) {
1014 offsets = calloc(target_cnt, sizeof(*offsets));
1015 cookies = calloc(target_cnt, sizeof(*cookies));
1016 ref_ctr_offsets = calloc(target_cnt, sizeof(*ref_ctr_offsets));
1017
1018 if (!offsets || !ref_ctr_offsets || !cookies) {
1019 err = -ENOMEM;
1020 goto err_out;
1021 }
1022 } else {
1023 link->uprobes = calloc(target_cnt, sizeof(*link->uprobes));
1024 if (!link->uprobes) {
1025 err = -ENOMEM;
1026 goto err_out;
1027 }
1028 }
1029
1030 for (i = 0; i < target_cnt; i++) {
1031 struct usdt_target *target = &targets[i];
1032 struct bpf_link *uprobe_link;
1033 bool is_new;
1034 int spec_id;
1035
1036 /* Spec ID can be either reused or newly allocated. If it is
1037 * newly allocated, we'll need to fill out spec map, otherwise
1038 * entire spec should be valid and can be just used by a new
1039 * uprobe. We reuse spec when USDT arg spec is identical. We
1040 * also never share specs between two different USDT
1041 * attachments ("links"), so all the reused specs already
1042 * share USDT cookie value implicitly.
1043 */
1044 err = allocate_spec_id(man, specs_hash, link, target, &spec_id, &is_new);
1045 if (err)
1046 goto err_out;
1047
1048 if (is_new && bpf_map_update_elem(spec_map_fd, &spec_id, &target->spec, BPF_ANY)) {
1049 err = -errno;
1050 pr_warn("usdt: failed to set USDT spec #%d for '%s:%s' in '%s': %d\n",
1051 spec_id, usdt_provider, usdt_name, path, err);
1052 goto err_out;
1053 }
1054 if (!man->has_bpf_cookie &&
1055 bpf_map_update_elem(ip_map_fd, &target->abs_ip, &spec_id, BPF_NOEXIST)) {
1056 err = -errno;
1057 if (err == -EEXIST) {
1058 pr_warn("usdt: IP collision detected for spec #%d for '%s:%s' in '%s'\n",
1059 spec_id, usdt_provider, usdt_name, path);
1060 } else {
1061 pr_warn("usdt: failed to map IP 0x%lx to spec #%d for '%s:%s' in '%s': %d\n",
1062 target->abs_ip, spec_id, usdt_provider, usdt_name,
1063 path, err);
1064 }
1065 goto err_out;
1066 }
1067
1068 if (man->has_uprobe_multi) {
1069 offsets[i] = target->rel_ip;
1070 ref_ctr_offsets[i] = target->sema_off;
1071 cookies[i] = spec_id;
1072 } else {
1073 opts.ref_ctr_offset = target->sema_off;
1074 opts.bpf_cookie = man->has_bpf_cookie ? spec_id : 0;
1075 uprobe_link = bpf_program__attach_uprobe_opts(prog, pid, path,
1076 target->rel_ip, &opts);
1077 err = libbpf_get_error(uprobe_link);
1078 if (err) {
1079 pr_warn("usdt: failed to attach uprobe #%d for '%s:%s' in '%s': %d\n",
1080 i, usdt_provider, usdt_name, path, err);
1081 goto err_out;
1082 }
1083
1084 link->uprobes[i].link = uprobe_link;
1085 link->uprobes[i].abs_ip = target->abs_ip;
1086 link->uprobe_cnt++;
1087 }
1088 }
1089
1090 if (man->has_uprobe_multi) {
1091 LIBBPF_OPTS(bpf_uprobe_multi_opts, opts_multi,
1092 .ref_ctr_offsets = ref_ctr_offsets,
1093 .offsets = offsets,
1094 .cookies = cookies,
1095 .cnt = target_cnt,
1096 );
1097
1098 link->multi_link = bpf_program__attach_uprobe_multi(prog, pid, path,
1099 NULL, &opts_multi);
1100 if (!link->multi_link) {
1101 err = -errno;
1102 pr_warn("usdt: failed to attach uprobe multi for '%s:%s' in '%s': %d\n",
1103 usdt_provider, usdt_name, path, err);
1104 goto err_out;
1105 }
1106
1107 free(offsets);
1108 free(ref_ctr_offsets);
1109 free(cookies);
1110 }
1111
1112 free(targets);
1113 hashmap__free(specs_hash);
1114 elf_close(&elf_fd);
1115 return &link->link;
1116
1117 err_out:
1118 free(offsets);
1119 free(ref_ctr_offsets);
1120 free(cookies);
1121
1122 if (link)
1123 bpf_link__destroy(&link->link);
1124 free(targets);
1125 hashmap__free(specs_hash);
1126 elf_close(&elf_fd);
1127 return libbpf_err_ptr(err);
1128 }
1129
1130 /* Parse out USDT ELF note from '.note.stapsdt' section.
1131 * Logic inspired by perf's code.
1132 */
1133 static int parse_usdt_note(Elf *elf, const char *path, GElf_Nhdr *nhdr,
1134 const char *data, size_t name_off, size_t desc_off,
1135 struct usdt_note *note)
1136 {
1137 const char *provider, *name, *args;
1138 long addrs[3];
1139 size_t len;
1140
1141 /* sanity check USDT note name and type first */
1142 if (strncmp(data + name_off, USDT_NOTE_NAME, nhdr->n_namesz) != 0)
1143 return -EINVAL;
1144 if (nhdr->n_type != USDT_NOTE_TYPE)
1145 return -EINVAL;
1146
1147 /* sanity check USDT note contents ("description" in ELF terminology) */
1148 len = nhdr->n_descsz;
1149 data = data + desc_off;
1150
1151 /* +3 is the very minimum required to store three empty strings */
1152 if (len < sizeof(addrs) + 3)
1153 return -EINVAL;
1154
1155 /* get location, base, and semaphore addrs */
1156 memcpy(&addrs, data, sizeof(addrs));
1157
1158 /* parse string fields: provider, name, args */
1159 provider = data + sizeof(addrs);
1160
1161 name = (const char *)memchr(provider, '\0', data + len - provider);
1162 if (!name) /* non-zero-terminated provider */
1163 return -EINVAL;
1164 name++;
1165 if (name >= data + len || *name == '\0') /* missing or empty name */
1166 return -EINVAL;
1167
1168 args = memchr(name, '\0', data + len - name);
1169 if (!args) /* non-zero-terminated name */
1170 return -EINVAL;
1171 ++args;
1172 if (args >= data + len) /* missing arguments spec */
1173 return -EINVAL;
1174
1175 note->provider = provider;
1176 note->name = name;
1177 if (*args == '\0' || *args == ':')
1178 note->args = "";
1179 else
1180 note->args = args;
1181 note->loc_addr = addrs[0];
1182 note->base_addr = addrs[1];
1183 note->sema_addr = addrs[2];
1184
1185 return 0;
1186 }
1187
1188 static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec *arg, int *arg_sz);
1189
1190 static int parse_usdt_spec(struct usdt_spec *spec, const struct usdt_note *note, __u64 usdt_cookie)
1191 {
1192 struct usdt_arg_spec *arg;
1193 const char *s;
1194 int arg_sz, len;
1195
1196 spec->usdt_cookie = usdt_cookie;
1197 spec->arg_cnt = 0;
1198
1199 s = note->args;
1200 while (s[0]) {
1201 if (spec->arg_cnt >= USDT_MAX_ARG_CNT) {
1202 pr_warn("usdt: too many USDT arguments (> %d) for '%s:%s' with args spec '%s'\n",
1203 USDT_MAX_ARG_CNT, note->provider, note->name, note->args);
1204 return -E2BIG;
1205 }
1206
1207 arg = &spec->args[spec->arg_cnt];
1208 len = parse_usdt_arg(s, spec->arg_cnt, arg, &arg_sz);
1209 if (len < 0)
1210 return len;
1211
1212 arg->arg_signed = arg_sz < 0;
1213 if (arg_sz < 0)
1214 arg_sz = -arg_sz;
1215
1216 switch (arg_sz) {
1217 case 1: case 2: case 4: case 8:
1218 arg->arg_bitshift = 64 - arg_sz * 8;
1219 break;
1220 default:
1221 pr_warn("usdt: unsupported arg #%d (spec '%s') size: %d\n",
1222 spec->arg_cnt, s, arg_sz);
1223 return -EINVAL;
1224 }
1225
1226 s += len;
1227 spec->arg_cnt++;
1228 }
1229
1230 return 0;
1231 }
1232
1233 /* Architecture-specific logic for parsing USDT argument location specs */
1234
1235 #if defined(__x86_64__) || defined(__i386__)
1236
1237 static int calc_pt_regs_off(const char *reg_name)
1238 {
1239 static struct {
1240 const char *names[4];
1241 size_t pt_regs_off;
1242 } reg_map[] = {
1243 #ifdef __x86_64__
1244 #define reg_off(reg64, reg32) offsetof(struct pt_regs, reg64)
1245 #else
1246 #define reg_off(reg64, reg32) offsetof(struct pt_regs, reg32)
1247 #endif
1248 { {"rip", "eip", "", ""}, reg_off(rip, eip) },
1249 { {"rax", "eax", "ax", "al"}, reg_off(rax, eax) },
1250 { {"rbx", "ebx", "bx", "bl"}, reg_off(rbx, ebx) },
1251 { {"rcx", "ecx", "cx", "cl"}, reg_off(rcx, ecx) },
1252 { {"rdx", "edx", "dx", "dl"}, reg_off(rdx, edx) },
1253 { {"rsi", "esi", "si", "sil"}, reg_off(rsi, esi) },
1254 { {"rdi", "edi", "di", "dil"}, reg_off(rdi, edi) },
1255 { {"rbp", "ebp", "bp", "bpl"}, reg_off(rbp, ebp) },
1256 { {"rsp", "esp", "sp", "spl"}, reg_off(rsp, esp) },
1257 #undef reg_off
1258 #ifdef __x86_64__
1259 { {"r8", "r8d", "r8w", "r8b"}, offsetof(struct pt_regs, r8) },
1260 { {"r9", "r9d", "r9w", "r9b"}, offsetof(struct pt_regs, r9) },
1261 { {"r10", "r10d", "r10w", "r10b"}, offsetof(struct pt_regs, r10) },
1262 { {"r11", "r11d", "r11w", "r11b"}, offsetof(struct pt_regs, r11) },
1263 { {"r12", "r12d", "r12w", "r12b"}, offsetof(struct pt_regs, r12) },
1264 { {"r13", "r13d", "r13w", "r13b"}, offsetof(struct pt_regs, r13) },
1265 { {"r14", "r14d", "r14w", "r14b"}, offsetof(struct pt_regs, r14) },
1266 { {"r15", "r15d", "r15w", "r15b"}, offsetof(struct pt_regs, r15) },
1267 #endif
1268 };
1269 int i, j;
1270
1271 for (i = 0; i < ARRAY_SIZE(reg_map); i++) {
1272 for (j = 0; j < ARRAY_SIZE(reg_map[i].names); j++) {
1273 if (strcmp(reg_name, reg_map[i].names[j]) == 0)
1274 return reg_map[i].pt_regs_off;
1275 }
1276 }
1277
1278 pr_warn("usdt: unrecognized register '%s'\n", reg_name);
1279 return -ENOENT;
1280 }
1281
1282 static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec *arg, int *arg_sz)
1283 {
1284 char reg_name[16];
1285 int len, reg_off;
1286 long off;
1287
1288 if (sscanf(arg_str, " %d @ %ld ( %%%15[^)] ) %n", arg_sz, &off, reg_name, &len) == 3) {
1289 /* Memory dereference case, e.g., -4@-20(%rbp) */
1290 arg->arg_type = USDT_ARG_REG_DEREF;
1291 arg->val_off = off;
1292 reg_off = calc_pt_regs_off(reg_name);
1293 if (reg_off < 0)
1294 return reg_off;
1295 arg->reg_off = reg_off;
1296 } else if (sscanf(arg_str, " %d @ ( %%%15[^)] ) %n", arg_sz, reg_name, &len) == 2) {
1297 /* Memory dereference case without offset, e.g., 8@(%rsp) */
1298 arg->arg_type = USDT_ARG_REG_DEREF;
1299 arg->val_off = 0;
1300 reg_off = calc_pt_regs_off(reg_name);
1301 if (reg_off < 0)
1302 return reg_off;
1303 arg->reg_off = reg_off;
1304 } else if (sscanf(arg_str, " %d @ %%%15s %n", arg_sz, reg_name, &len) == 2) {
1305 /* Register read case, e.g., -4@%eax */
1306 arg->arg_type = USDT_ARG_REG;
1307 arg->val_off = 0;
1308
1309 reg_off = calc_pt_regs_off(reg_name);
1310 if (reg_off < 0)
1311 return reg_off;
1312 arg->reg_off = reg_off;
1313 } else if (sscanf(arg_str, " %d @ $%ld %n", arg_sz, &off, &len) == 2) {
1314 /* Constant value case, e.g., 4@$71 */
1315 arg->arg_type = USDT_ARG_CONST;
1316 arg->val_off = off;
1317 arg->reg_off = 0;
1318 } else {
1319 pr_warn("usdt: unrecognized arg #%d spec '%s'\n", arg_num, arg_str);
1320 return -EINVAL;
1321 }
1322
1323 return len;
1324 }
1325
1326 #elif defined(__s390x__)
1327
1328 /* Do not support __s390__ for now, since user_pt_regs is broken with -m31. */
1329
1330 static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec *arg, int *arg_sz)
1331 {
1332 unsigned int reg;
1333 int len;
1334 long off;
1335
1336 if (sscanf(arg_str, " %d @ %ld ( %%r%u ) %n", arg_sz, &off, ®, &len) == 3) {
1337 /* Memory dereference case, e.g., -2@-28(%r15) */
1338 arg->arg_type = USDT_ARG_REG_DEREF;
1339 arg->val_off = off;
1340 if (reg > 15) {
1341 pr_warn("usdt: unrecognized register '%%r%u'\n", reg);
1342 return -EINVAL;
1343 }
1344 arg->reg_off = offsetof(user_pt_regs, gprs[reg]);
1345 } else if (sscanf(arg_str, " %d @ %%r%u %n", arg_sz, ®, &len) == 2) {
1346 /* Register read case, e.g., -8@%r0 */
1347 arg->arg_type = USDT_ARG_REG;
1348 arg->val_off = 0;
1349 if (reg > 15) {
1350 pr_warn("usdt: unrecognized register '%%r%u'\n", reg);
1351 return -EINVAL;
1352 }
1353 arg->reg_off = offsetof(user_pt_regs, gprs[reg]);
1354 } else if (sscanf(arg_str, " %d @ %ld %n", arg_sz, &off, &len) == 2) {
1355 /* Constant value case, e.g., 4@71 */
1356 arg->arg_type = USDT_ARG_CONST;
1357 arg->val_off = off;
1358 arg->reg_off = 0;
1359 } else {
1360 pr_warn("usdt: unrecognized arg #%d spec '%s'\n", arg_num, arg_str);
1361 return -EINVAL;
1362 }
1363
1364 return len;
1365 }
1366
1367 #elif defined(__aarch64__)
1368
1369 static int calc_pt_regs_off(const char *reg_name)
1370 {
1371 int reg_num;
1372
1373 if (sscanf(reg_name, "x%d", ®_num) == 1) {
1374 if (reg_num >= 0 && reg_num < 31)
1375 return offsetof(struct user_pt_regs, regs[reg_num]);
1376 } else if (strcmp(reg_name, "sp") == 0) {
1377 return offsetof(struct user_pt_regs, sp);
1378 }
1379 pr_warn("usdt: unrecognized register '%s'\n", reg_name);
1380 return -ENOENT;
1381 }
1382
1383 static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec *arg, int *arg_sz)
1384 {
1385 char reg_name[16];
1386 int len, reg_off;
1387 long off;
1388
1389 if (sscanf(arg_str, " %d @ \[ %15[a-z0-9] , %ld ] %n", arg_sz, reg_name, &off, &len) == 3) {
1390 /* Memory dereference case, e.g., -4@[sp, 96] */
1391 arg->arg_type = USDT_ARG_REG_DEREF;
1392 arg->val_off = off;
1393 reg_off = calc_pt_regs_off(reg_name);
1394 if (reg_off < 0)
1395 return reg_off;
1396 arg->reg_off = reg_off;
1397 } else if (sscanf(arg_str, " %d @ \[ %15[a-z0-9] ] %n", arg_sz, reg_name, &len) == 2) {
1398 /* Memory dereference case, e.g., -4@[sp] */
1399 arg->arg_type = USDT_ARG_REG_DEREF;
1400 arg->val_off = 0;
1401 reg_off = calc_pt_regs_off(reg_name);
1402 if (reg_off < 0)
1403 return reg_off;
1404 arg->reg_off = reg_off;
1405 } else if (sscanf(arg_str, " %d @ %ld %n", arg_sz, &off, &len) == 2) {
1406 /* Constant value case, e.g., 4@5 */
1407 arg->arg_type = USDT_ARG_CONST;
1408 arg->val_off = off;
1409 arg->reg_off = 0;
1410 } else if (sscanf(arg_str, " %d @ %15[a-z0-9] %n", arg_sz, reg_name, &len) == 2) {
1411 /* Register read case, e.g., -8@x4 */
1412 arg->arg_type = USDT_ARG_REG;
1413 arg->val_off = 0;
1414 reg_off = calc_pt_regs_off(reg_name);
1415 if (reg_off < 0)
1416 return reg_off;
1417 arg->reg_off = reg_off;
1418 } else {
1419 pr_warn("usdt: unrecognized arg #%d spec '%s'\n", arg_num, arg_str);
1420 return -EINVAL;
1421 }
1422
1423 return len;
1424 }
1425
1426 #elif defined(__riscv)
1427
1428 static int calc_pt_regs_off(const char *reg_name)
1429 {
1430 static struct {
1431 const char *name;
1432 size_t pt_regs_off;
1433 } reg_map[] = {
1434 { "ra", offsetof(struct user_regs_struct, ra) },
1435 { "sp", offsetof(struct user_regs_struct, sp) },
1436 { "gp", offsetof(struct user_regs_struct, gp) },
1437 { "tp", offsetof(struct user_regs_struct, tp) },
1438 { "a0", offsetof(struct user_regs_struct, a0) },
1439 { "a1", offsetof(struct user_regs_struct, a1) },
1440 { "a2", offsetof(struct user_regs_struct, a2) },
1441 { "a3", offsetof(struct user_regs_struct, a3) },
1442 { "a4", offsetof(struct user_regs_struct, a4) },
1443 { "a5", offsetof(struct user_regs_struct, a5) },
1444 { "a6", offsetof(struct user_regs_struct, a6) },
1445 { "a7", offsetof(struct user_regs_struct, a7) },
1446 { "s0", offsetof(struct user_regs_struct, s0) },
1447 { "s1", offsetof(struct user_regs_struct, s1) },
1448 { "s2", offsetof(struct user_regs_struct, s2) },
1449 { "s3", offsetof(struct user_regs_struct, s3) },
1450 { "s4", offsetof(struct user_regs_struct, s4) },
1451 { "s5", offsetof(struct user_regs_struct, s5) },
1452 { "s6", offsetof(struct user_regs_struct, s6) },
1453 { "s7", offsetof(struct user_regs_struct, s7) },
1454 { "s8", offsetof(struct user_regs_struct, rv_s8) },
1455 { "s9", offsetof(struct user_regs_struct, s9) },
1456 { "s10", offsetof(struct user_regs_struct, s10) },
1457 { "s11", offsetof(struct user_regs_struct, s11) },
1458 { "t0", offsetof(struct user_regs_struct, t0) },
1459 { "t1", offsetof(struct user_regs_struct, t1) },
1460 { "t2", offsetof(struct user_regs_struct, t2) },
1461 { "t3", offsetof(struct user_regs_struct, t3) },
1462 { "t4", offsetof(struct user_regs_struct, t4) },
1463 { "t5", offsetof(struct user_regs_struct, t5) },
1464 { "t6", offsetof(struct user_regs_struct, t6) },
1465 };
1466 int i;
1467
1468 for (i = 0; i < ARRAY_SIZE(reg_map); i++) {
1469 if (strcmp(reg_name, reg_map[i].name) == 0)
1470 return reg_map[i].pt_regs_off;
1471 }
1472
1473 pr_warn("usdt: unrecognized register '%s'\n", reg_name);
1474 return -ENOENT;
1475 }
1476
1477 static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec *arg, int *arg_sz)
1478 {
1479 char reg_name[16];
1480 int len, reg_off;
1481 long off;
1482
1483 if (sscanf(arg_str, " %d @ %ld ( %15[a-z0-9] ) %n", arg_sz, &off, reg_name, &len) == 3) {
1484 /* Memory dereference case, e.g., -8@-88(s0) */
1485 arg->arg_type = USDT_ARG_REG_DEREF;
1486 arg->val_off = off;
1487 reg_off = calc_pt_regs_off(reg_name);
1488 if (reg_off < 0)
1489 return reg_off;
1490 arg->reg_off = reg_off;
1491 } else if (sscanf(arg_str, " %d @ %ld %n", arg_sz, &off, &len) == 2) {
1492 /* Constant value case, e.g., 4@5 */
1493 arg->arg_type = USDT_ARG_CONST;
1494 arg->val_off = off;
1495 arg->reg_off = 0;
1496 } else if (sscanf(arg_str, " %d @ %15[a-z0-9] %n", arg_sz, reg_name, &len) == 2) {
1497 /* Register read case, e.g., -8@a1 */
1498 arg->arg_type = USDT_ARG_REG;
1499 arg->val_off = 0;
1500 reg_off = calc_pt_regs_off(reg_name);
1501 if (reg_off < 0)
1502 return reg_off;
1503 arg->reg_off = reg_off;
1504 } else {
1505 pr_warn("usdt: unrecognized arg #%d spec '%s'\n", arg_num, arg_str);
1506 return -EINVAL;
1507 }
1508
1509 return len;
1510 }
1511
1512 #elif defined(__arm__)
1513
1514 static int calc_pt_regs_off(const char *reg_name)
1515 {
1516 static struct {
1517 const char *name;
1518 size_t pt_regs_off;
1519 } reg_map[] = {
1520 { "r0", offsetof(struct pt_regs, uregs[0]) },
1521 { "r1", offsetof(struct pt_regs, uregs[1]) },
1522 { "r2", offsetof(struct pt_regs, uregs[2]) },
1523 { "r3", offsetof(struct pt_regs, uregs[3]) },
1524 { "r4", offsetof(struct pt_regs, uregs[4]) },
1525 { "r5", offsetof(struct pt_regs, uregs[5]) },
1526 { "r6", offsetof(struct pt_regs, uregs[6]) },
1527 { "r7", offsetof(struct pt_regs, uregs[7]) },
1528 { "r8", offsetof(struct pt_regs, uregs[8]) },
1529 { "r9", offsetof(struct pt_regs, uregs[9]) },
1530 { "r10", offsetof(struct pt_regs, uregs[10]) },
1531 { "fp", offsetof(struct pt_regs, uregs[11]) },
1532 { "ip", offsetof(struct pt_regs, uregs[12]) },
1533 { "sp", offsetof(struct pt_regs, uregs[13]) },
1534 { "lr", offsetof(struct pt_regs, uregs[14]) },
1535 { "pc", offsetof(struct pt_regs, uregs[15]) },
1536 };
1537 int i;
1538
1539 for (i = 0; i < ARRAY_SIZE(reg_map); i++) {
1540 if (strcmp(reg_name, reg_map[i].name) == 0)
1541 return reg_map[i].pt_regs_off;
1542 }
1543
1544 pr_warn("usdt: unrecognized register '%s'\n", reg_name);
1545 return -ENOENT;
1546 }
1547
1548 static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec *arg, int *arg_sz)
1549 {
1550 char reg_name[16];
1551 int len, reg_off;
1552 long off;
1553
1554 if (sscanf(arg_str, " %d @ \[ %15[a-z0-9] , #%ld ] %n",
1555 arg_sz, reg_name, &off, &len) == 3) {
1556 /* Memory dereference case, e.g., -4@[fp, #96] */
1557 arg->arg_type = USDT_ARG_REG_DEREF;
1558 arg->val_off = off;
1559 reg_off = calc_pt_regs_off(reg_name);
1560 if (reg_off < 0)
1561 return reg_off;
1562 arg->reg_off = reg_off;
1563 } else if (sscanf(arg_str, " %d @ \[ %15[a-z0-9] ] %n", arg_sz, reg_name, &len) == 2) {
1564 /* Memory dereference case, e.g., -4@[sp] */
1565 arg->arg_type = USDT_ARG_REG_DEREF;
1566 arg->val_off = 0;
1567 reg_off = calc_pt_regs_off(reg_name);
1568 if (reg_off < 0)
1569 return reg_off;
1570 arg->reg_off = reg_off;
1571 } else if (sscanf(arg_str, " %d @ #%ld %n", arg_sz, &off, &len) == 2) {
1572 /* Constant value case, e.g., 4@#5 */
1573 arg->arg_type = USDT_ARG_CONST;
1574 arg->val_off = off;
1575 arg->reg_off = 0;
1576 } else if (sscanf(arg_str, " %d @ %15[a-z0-9] %n", arg_sz, reg_name, &len) == 2) {
1577 /* Register read case, e.g., -8@r4 */
1578 arg->arg_type = USDT_ARG_REG;
1579 arg->val_off = 0;
1580 reg_off = calc_pt_regs_off(reg_name);
1581 if (reg_off < 0)
1582 return reg_off;
1583 arg->reg_off = reg_off;
1584 } else {
1585 pr_warn("usdt: unrecognized arg #%d spec '%s'\n", arg_num, arg_str);
1586 return -EINVAL;
1587 }
1588
1589 return len;
1590 }
1591
1592 #else
1593
1594 static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec *arg, int *arg_sz)
1595 {
1596 pr_warn("usdt: libbpf doesn't support USDTs on current architecture\n");
1597 return -ENOTSUP;
1598 }
1599
1600 #endif
1601
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