xref: /linux/tools/perf/util/probe-finder.c (revision 621cde16e49b3ecf7d59a8106a20aaebfb4a59a9)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * probe-finder.c : C expression to kprobe event converter
4  *
5  * Written by Masami Hiramatsu <mhiramat@redhat.com>
6  */
7 
8 #include <inttypes.h>
9 #include <sys/utsname.h>
10 #include <sys/types.h>
11 #include <sys/stat.h>
12 #include <fcntl.h>
13 #include <errno.h>
14 #include <stdio.h>
15 #include <unistd.h>
16 #include <stdlib.h>
17 #include <string.h>
18 #include <stdarg.h>
19 #include <dwarf-regs.h>
20 
21 #include <linux/bitops.h>
22 #include <linux/zalloc.h>
23 #include "event.h"
24 #include "dso.h"
25 #include "debug.h"
26 #include "debuginfo.h"
27 #include "intlist.h"
28 #include "strbuf.h"
29 #include "strlist.h"
30 #include "symbol.h"
31 #include "probe-finder.h"
32 #include "probe-file.h"
33 #include "string2.h"
34 
35 /* Kprobe tracer basic type is up to u64 */
36 #define MAX_BASIC_TYPE_BITS	64
37 
38 /*
39  * Probe finder related functions
40  */
41 
alloc_trace_arg_ref(long offs)42 static struct probe_trace_arg_ref *alloc_trace_arg_ref(long offs)
43 {
44 	struct probe_trace_arg_ref *ref;
45 	ref = zalloc(sizeof(struct probe_trace_arg_ref));
46 	if (ref != NULL)
47 		ref->offset = offs;
48 	return ref;
49 }
50 
51 /*
52  * Convert a location into trace_arg.
53  * If tvar == NULL, this just checks variable can be converted.
54  * If fentry == true and vr_die is a parameter, do heuristic search
55  * for the location fuzzed by function entry mcount.
56  */
convert_variable_location(Dwarf_Die * vr_die,Dwarf_Addr addr,Dwarf_Op * fb_ops,Dwarf_Die * sp_die,unsigned int machine,struct probe_trace_arg * tvar)57 static int convert_variable_location(Dwarf_Die *vr_die, Dwarf_Addr addr,
58 				     Dwarf_Op *fb_ops, Dwarf_Die *sp_die,
59 				     unsigned int machine,
60 				     struct probe_trace_arg *tvar)
61 {
62 	Dwarf_Attribute attr;
63 	Dwarf_Addr tmp = 0;
64 	Dwarf_Op *op;
65 	size_t nops;
66 	unsigned int regn;
67 	Dwarf_Word offs = 0;
68 	bool ref = false;
69 	const char *regs;
70 	int ret, ret2 = 0;
71 
72 	if (dwarf_attr(vr_die, DW_AT_external, &attr) != NULL)
73 		goto static_var;
74 
75 	/* Constant value */
76 	if (dwarf_attr(vr_die, DW_AT_const_value, &attr) &&
77 	    immediate_value_is_supported()) {
78 		Dwarf_Sword snum;
79 
80 		if (!tvar)
81 			return 0;
82 
83 		dwarf_formsdata(&attr, &snum);
84 		ret = asprintf(&tvar->value, "\\%ld", (long)snum);
85 
86 		return ret < 0 ? -ENOMEM : 0;
87 	}
88 
89 	/* TODO: handle more than 1 exprs */
90 	if (dwarf_attr(vr_die, DW_AT_location, &attr) == NULL)
91 		return -EINVAL;	/* Broken DIE ? */
92 	if (dwarf_getlocation_addr(&attr, addr, &op, &nops, 1) <= 0) {
93 		ret = dwarf_entrypc(sp_die, &tmp);
94 		if (ret)
95 			return -ENOENT;
96 
97 		if (probe_conf.show_location_range &&
98 			(dwarf_tag(vr_die) == DW_TAG_variable)) {
99 			ret2 = -ERANGE;
100 		} else if (addr != tmp ||
101 			dwarf_tag(vr_die) != DW_TAG_formal_parameter) {
102 			return -ENOENT;
103 		}
104 
105 		ret = dwarf_highpc(sp_die, &tmp);
106 		if (ret)
107 			return -ENOENT;
108 		/*
109 		 * This is fuzzed by fentry mcount. We try to find the
110 		 * parameter location at the earliest address.
111 		 */
112 		for (addr += 1; addr <= tmp; addr++) {
113 			if (dwarf_getlocation_addr(&attr, addr, &op,
114 						   &nops, 1) > 0)
115 				goto found;
116 		}
117 		return -ENOENT;
118 	}
119 found:
120 	if (nops == 0)
121 		/* TODO: Support const_value */
122 		return -ENOENT;
123 
124 	if (op->atom == DW_OP_addr) {
125 static_var:
126 		if (!tvar)
127 			return ret2;
128 		/* Static variables on memory (not stack), make @varname */
129 		ret = strlen(dwarf_diename(vr_die));
130 		tvar->value = zalloc(ret + 2);
131 		if (tvar->value == NULL)
132 			return -ENOMEM;
133 		snprintf(tvar->value, ret + 2, "@%s", dwarf_diename(vr_die));
134 		tvar->ref = alloc_trace_arg_ref((long)offs);
135 		if (tvar->ref == NULL)
136 			return -ENOMEM;
137 		return ret2;
138 	}
139 
140 	/* If this is based on frame buffer, set the offset */
141 	if (op->atom == DW_OP_fbreg) {
142 		if (fb_ops == NULL)
143 			return -ENOTSUP;
144 		ref = true;
145 		offs = op->number;
146 		op = &fb_ops[0];
147 	}
148 
149 	if (op->atom >= DW_OP_breg0 && op->atom <= DW_OP_breg31) {
150 		regn = op->atom - DW_OP_breg0;
151 		offs += op->number;
152 		ref = true;
153 	} else if (op->atom >= DW_OP_reg0 && op->atom <= DW_OP_reg31) {
154 		regn = op->atom - DW_OP_reg0;
155 	} else if (op->atom == DW_OP_bregx) {
156 		regn = op->number;
157 		offs += op->number2;
158 		ref = true;
159 	} else if (op->atom == DW_OP_regx) {
160 		regn = op->number;
161 	} else {
162 		pr_debug("DW_OP %x is not supported.\n", op->atom);
163 		return -ENOTSUP;
164 	}
165 
166 	if (!tvar)
167 		return ret2;
168 
169 	regs = get_dwarf_regstr(regn, machine);
170 	if (!regs) {
171 		/* This should be a bug in DWARF or this tool */
172 		pr_warning("Mapping for the register number %u "
173 			   "missing on this architecture.\n", regn);
174 		return -ENOTSUP;
175 	}
176 
177 	tvar->value = strdup(regs);
178 	if (tvar->value == NULL)
179 		return -ENOMEM;
180 
181 	if (ref) {
182 		tvar->ref = alloc_trace_arg_ref((long)offs);
183 		if (tvar->ref == NULL)
184 			return -ENOMEM;
185 	}
186 	return ret2;
187 }
188 
convert_variable_type(Dwarf_Die * vr_die,struct probe_trace_arg * tvar,const char * cast,bool user_access)189 static int convert_variable_type(Dwarf_Die *vr_die,
190 				 struct probe_trace_arg *tvar,
191 				 const char *cast, bool user_access)
192 {
193 	struct probe_trace_arg_ref **ref_ptr = &tvar->ref;
194 	Dwarf_Die type;
195 	char buf[16];
196 	char sbuf[STRERR_BUFSIZE];
197 	int bsize, boffs, total;
198 	int ret;
199 	char prefix;
200 
201 	/* TODO: check all types */
202 	if (cast && strcmp(cast, "string") != 0 && strcmp(cast, "ustring") &&
203 	    strcmp(cast, "x") != 0 &&
204 	    strcmp(cast, "s") != 0 && strcmp(cast, "u") != 0) {
205 		/* Non string type is OK */
206 		/* and respect signedness/hexadecimal cast */
207 		tvar->type = strdup(cast);
208 		return (tvar->type == NULL) ? -ENOMEM : 0;
209 	}
210 
211 	bsize = dwarf_bitsize(vr_die);
212 	if (bsize > 0) {
213 		/* This is a bitfield */
214 		boffs = dwarf_bitoffset(vr_die);
215 		total = dwarf_bytesize(vr_die);
216 		if (boffs < 0 || total < 0)
217 			return -ENOENT;
218 		ret = snprintf(buf, 16, "b%d@%d/%d", bsize, boffs,
219 				BYTES_TO_BITS(total));
220 		goto formatted;
221 	}
222 
223 	if (die_get_real_type(vr_die, &type) == NULL) {
224 		pr_warning("Failed to get a type information of %s.\n",
225 			   dwarf_diename(vr_die));
226 		return -ENOENT;
227 	}
228 
229 	pr_debug("%s type is %s.\n",
230 		 dwarf_diename(vr_die), dwarf_diename(&type));
231 
232 	if (cast && (!strcmp(cast, "string") || !strcmp(cast, "ustring"))) {
233 		/* String type */
234 		ret = dwarf_tag(&type);
235 		if (ret != DW_TAG_pointer_type &&
236 		    ret != DW_TAG_array_type) {
237 			pr_warning("Failed to cast into string: "
238 				   "%s(%s) is not a pointer nor array.\n",
239 				   dwarf_diename(vr_die), dwarf_diename(&type));
240 			return -EINVAL;
241 		}
242 		if (die_get_real_type(&type, &type) == NULL) {
243 			pr_warning("Failed to get a type"
244 				   " information.\n");
245 			return -ENOENT;
246 		}
247 		if (ret == DW_TAG_pointer_type) {
248 			while (*ref_ptr)
249 				ref_ptr = &(*ref_ptr)->next;
250 			/* Add new reference with offset +0 */
251 			*ref_ptr = zalloc(sizeof(struct probe_trace_arg_ref));
252 			if (*ref_ptr == NULL) {
253 				pr_warning("Out of memory error\n");
254 				return -ENOMEM;
255 			}
256 			(*ref_ptr)->user_access = user_access;
257 		}
258 		if (!die_compare_name(&type, "char") &&
259 		    !die_compare_name(&type, "unsigned char")) {
260 			pr_warning("Failed to cast into string: "
261 				   "%s is not (unsigned) char *.\n",
262 				   dwarf_diename(vr_die));
263 			return -EINVAL;
264 		}
265 		tvar->type = strdup(cast);
266 		return (tvar->type == NULL) ? -ENOMEM : 0;
267 	}
268 
269 	if (cast && (strcmp(cast, "u") == 0))
270 		prefix = 'u';
271 	else if (cast && (strcmp(cast, "s") == 0))
272 		prefix = 's';
273 	else if (cast && (strcmp(cast, "x") == 0) &&
274 		 probe_type_is_available(PROBE_TYPE_X))
275 		prefix = 'x';
276 	else
277 		prefix = die_is_signed_type(&type) ? 's' :
278 			 probe_type_is_available(PROBE_TYPE_X) ? 'x' : 'u';
279 
280 	ret = dwarf_bytesize(&type);
281 	if (ret <= 0)
282 		/* No size ... try to use default type */
283 		return 0;
284 	ret = BYTES_TO_BITS(ret);
285 
286 	/* Check the bitwidth */
287 	if (ret > MAX_BASIC_TYPE_BITS) {
288 		pr_info("%s exceeds max-bitwidth. Cut down to %d bits.\n",
289 			dwarf_diename(&type), MAX_BASIC_TYPE_BITS);
290 		ret = MAX_BASIC_TYPE_BITS;
291 	}
292 	ret = snprintf(buf, 16, "%c%d", prefix, ret);
293 
294 formatted:
295 	if (ret < 0 || ret >= 16) {
296 		if (ret >= 16)
297 			ret = -E2BIG;
298 		pr_warning("Failed to convert variable type: %s\n",
299 			   str_error_r(-ret, sbuf, sizeof(sbuf)));
300 		return ret;
301 	}
302 	tvar->type = strdup(buf);
303 	if (tvar->type == NULL)
304 		return -ENOMEM;
305 	return 0;
306 }
307 
convert_variable_fields(Dwarf_Die * vr_die,const char * varname,struct perf_probe_arg_field * field,struct probe_trace_arg_ref ** ref_ptr,Dwarf_Die * die_mem,bool user_access)308 static int convert_variable_fields(Dwarf_Die *vr_die, const char *varname,
309 				    struct perf_probe_arg_field *field,
310 				    struct probe_trace_arg_ref **ref_ptr,
311 				    Dwarf_Die *die_mem, bool user_access)
312 {
313 	struct probe_trace_arg_ref *ref = *ref_ptr;
314 	Dwarf_Die type;
315 	Dwarf_Word offs;
316 	int ret, tag;
317 
318 	pr_debug("converting %s in %s\n", field->name, varname);
319 	if (die_get_real_type(vr_die, &type) == NULL) {
320 		pr_warning("Failed to get the type of %s.\n", varname);
321 		return -ENOENT;
322 	}
323 	pr_debug2("Var real type: %s (%x)\n", dwarf_diename(&type),
324 		  (unsigned)dwarf_dieoffset(&type));
325 	tag = dwarf_tag(&type);
326 
327 	if (field->name[0] == '[' &&
328 	    (tag == DW_TAG_array_type || tag == DW_TAG_pointer_type)) {
329 		/* Save original type for next field or type */
330 		memcpy(die_mem, &type, sizeof(*die_mem));
331 		/* Get the type of this array */
332 		if (die_get_real_type(&type, &type) == NULL) {
333 			pr_warning("Failed to get the type of %s.\n", varname);
334 			return -ENOENT;
335 		}
336 		pr_debug2("Array real type: %s (%x)\n", dwarf_diename(&type),
337 			 (unsigned)dwarf_dieoffset(&type));
338 		if (tag == DW_TAG_pointer_type) {
339 			ref = zalloc(sizeof(struct probe_trace_arg_ref));
340 			if (ref == NULL)
341 				return -ENOMEM;
342 			if (*ref_ptr)
343 				(*ref_ptr)->next = ref;
344 			else
345 				*ref_ptr = ref;
346 		}
347 		ref->offset += dwarf_bytesize(&type) * field->index;
348 		ref->user_access = user_access;
349 		goto next;
350 	} else if (tag == DW_TAG_pointer_type) {
351 		/* Check the pointer and dereference */
352 		if (!field->ref) {
353 			pr_err("Semantic error: %s must be referred by '->'\n",
354 			       field->name);
355 			return -EINVAL;
356 		}
357 		/* Get the type pointed by this pointer */
358 		if (die_get_real_type(&type, &type) == NULL) {
359 			pr_warning("Failed to get the type of %s.\n", varname);
360 			return -ENOENT;
361 		}
362 		/* Verify it is a data structure  */
363 		tag = dwarf_tag(&type);
364 		if (tag != DW_TAG_structure_type && tag != DW_TAG_union_type) {
365 			pr_warning("%s is not a data structure nor a union.\n",
366 				   varname);
367 			return -EINVAL;
368 		}
369 
370 		ref = zalloc(sizeof(struct probe_trace_arg_ref));
371 		if (ref == NULL)
372 			return -ENOMEM;
373 		if (*ref_ptr)
374 			(*ref_ptr)->next = ref;
375 		else
376 			*ref_ptr = ref;
377 	} else {
378 		/* Verify it is a data structure  */
379 		if (tag != DW_TAG_structure_type && tag != DW_TAG_union_type) {
380 			pr_warning("%s is not a data structure nor a union.\n",
381 				   varname);
382 			return -EINVAL;
383 		}
384 		if (field->name[0] == '[') {
385 			pr_err("Semantic error: %s is not a pointer"
386 			       " nor array.\n", varname);
387 			return -EINVAL;
388 		}
389 		/* While processing unnamed field, we don't care about this */
390 		if (field->ref && dwarf_diename(vr_die)) {
391 			pr_err("Semantic error: %s must be referred by '.'\n",
392 			       field->name);
393 			return -EINVAL;
394 		}
395 		if (!ref) {
396 			pr_warning("Structure on a register is not "
397 				   "supported yet.\n");
398 			return -ENOTSUP;
399 		}
400 	}
401 
402 	if (die_find_member(&type, field->name, die_mem) == NULL) {
403 		pr_warning("%s(type:%s) has no member %s.\n", varname,
404 			   dwarf_diename(&type), field->name);
405 		return -EINVAL;
406 	}
407 
408 	/* Get the offset of the field */
409 	if (tag == DW_TAG_union_type) {
410 		offs = 0;
411 	} else {
412 		ret = die_get_data_member_location(die_mem, &offs);
413 		if (ret < 0) {
414 			pr_warning("Failed to get the offset of %s.\n",
415 				   field->name);
416 			return ret;
417 		}
418 	}
419 	ref->offset += (long)offs;
420 	ref->user_access = user_access;
421 
422 	/* If this member is unnamed, we need to reuse this field */
423 	if (!dwarf_diename(die_mem))
424 		return convert_variable_fields(die_mem, varname, field,
425 						&ref, die_mem, user_access);
426 
427 next:
428 	/* Converting next field */
429 	if (field->next)
430 		return convert_variable_fields(die_mem, field->name,
431 				field->next, &ref, die_mem, user_access);
432 	else
433 		return 0;
434 }
435 
print_var_not_found(const char * varname)436 static void print_var_not_found(const char *varname)
437 {
438 	pr_err("Failed to find the location of the '%s' variable at this address.\n"
439 	       " Perhaps it has been optimized out.\n"
440 	       " Use -V with the --range option to show '%s' location range.\n",
441 		varname, varname);
442 }
443 
444 /* Show a variables in kprobe event format */
convert_variable(Dwarf_Die * vr_die,struct probe_finder * pf)445 static int convert_variable(Dwarf_Die *vr_die, struct probe_finder *pf)
446 {
447 	Dwarf_Die die_mem;
448 	int ret;
449 
450 	pr_debug("Converting variable %s into trace event.\n",
451 		 dwarf_diename(vr_die));
452 
453 	ret = convert_variable_location(vr_die, pf->addr, pf->fb_ops,
454 					&pf->sp_die, pf->machine, pf->tvar);
455 	if (ret == -ENOENT && pf->skip_empty_arg)
456 		/* This can be found in other place. skip it */
457 		return 0;
458 	if (ret == -ENOENT || ret == -EINVAL) {
459 		print_var_not_found(pf->pvar->var);
460 	} else if (ret == -ENOTSUP)
461 		pr_err("Sorry, we don't support this variable location yet.\n");
462 	else if (ret == 0 && pf->pvar->field) {
463 		ret = convert_variable_fields(vr_die, pf->pvar->var,
464 					      pf->pvar->field, &pf->tvar->ref,
465 					      &die_mem, pf->pvar->user_access);
466 		vr_die = &die_mem;
467 	}
468 	if (ret == 0)
469 		ret = convert_variable_type(vr_die, pf->tvar, pf->pvar->type,
470 					    pf->pvar->user_access);
471 	/* *expr will be cached in libdw. Don't free it. */
472 	return ret;
473 }
474 
475 /* Find a variable in a scope DIE */
find_variable(Dwarf_Die * sc_die,struct probe_finder * pf)476 static int find_variable(Dwarf_Die *sc_die, struct probe_finder *pf)
477 {
478 	Dwarf_Die vr_die;
479 	char *buf, *ptr;
480 	int ret = 0;
481 
482 	/* Copy raw parameters */
483 	if (!is_c_varname(pf->pvar->var))
484 		return copy_to_probe_trace_arg(pf->tvar, pf->pvar);
485 
486 	if (pf->pvar->name)
487 		pf->tvar->name = strdup(pf->pvar->name);
488 	else {
489 		buf = synthesize_perf_probe_arg(pf->pvar);
490 		if (!buf)
491 			return -ENOMEM;
492 		ptr = strchr(buf, ':');	/* Change type separator to _ */
493 		if (ptr)
494 			*ptr = '_';
495 		pf->tvar->name = buf;
496 	}
497 	if (pf->tvar->name == NULL)
498 		return -ENOMEM;
499 
500 	pr_debug("Searching '%s' variable in context.\n", pf->pvar->var);
501 	/* Search child die for local variables and parameters. */
502 	if (!die_find_variable_at(sc_die, pf->pvar->var, pf->addr, &vr_die)) {
503 		/* Search again in global variables */
504 		if (!die_find_variable_at(&pf->cu_die, pf->pvar->var,
505 						0, &vr_die)) {
506 			if (pf->skip_empty_arg)
507 				return 0;
508 			pr_warning("Failed to find '%s' in this function.\n",
509 				   pf->pvar->var);
510 			ret = -ENOENT;
511 		}
512 	}
513 	if (ret >= 0)
514 		ret = convert_variable(&vr_die, pf);
515 
516 	return ret;
517 }
518 
519 /* Convert subprogram DIE to trace point */
convert_to_trace_point(Dwarf_Die * sp_die,Dwfl_Module * mod,Dwarf_Addr paddr,bool retprobe,const char * function,struct probe_trace_point * tp)520 static int convert_to_trace_point(Dwarf_Die *sp_die, Dwfl_Module *mod,
521 				  Dwarf_Addr paddr, bool retprobe,
522 				  const char *function,
523 				  struct probe_trace_point *tp)
524 {
525 	Dwarf_Addr eaddr;
526 	GElf_Sym sym;
527 	const char *symbol;
528 
529 	/* Verify the address is correct */
530 	if (!dwarf_haspc(sp_die, paddr)) {
531 		pr_warning("Specified offset is out of %s\n",
532 			   dwarf_diename(sp_die));
533 		return -EINVAL;
534 	}
535 
536 	if (dwarf_entrypc(sp_die, &eaddr) == 0) {
537 		/* If the DIE has entrypc, use it. */
538 		symbol = dwarf_diename(sp_die);
539 	} else {
540 		/* Try to get actual symbol name and address from symtab */
541 		symbol = dwfl_module_addrsym(mod, paddr, &sym, NULL);
542 		eaddr = sym.st_value;
543 	}
544 	if (!symbol) {
545 		pr_warning("Failed to find symbol at 0x%lx\n",
546 			   (unsigned long)paddr);
547 		return -ENOENT;
548 	}
549 
550 	tp->offset = (unsigned long)(paddr - eaddr);
551 	tp->address = paddr;
552 	tp->symbol = strdup(symbol);
553 	if (!tp->symbol)
554 		return -ENOMEM;
555 
556 	/* Return probe must be on the head of a subprogram */
557 	if (retprobe) {
558 		if (eaddr != paddr) {
559 			pr_warning("Failed to find \"%s%%return\",\n"
560 				   " because %s is an inlined function and"
561 				   " has no return point.\n", function,
562 				   function);
563 			return -EINVAL;
564 		}
565 		tp->retprobe = true;
566 	}
567 
568 	return 0;
569 }
570 
571 /* Call probe_finder callback with scope DIE */
call_probe_finder(Dwarf_Die * sc_die,struct probe_finder * pf)572 static int call_probe_finder(Dwarf_Die *sc_die, struct probe_finder *pf)
573 {
574 	Dwarf_Attribute fb_attr;
575 	Dwarf_Frame *frame = NULL;
576 	size_t nops;
577 	int ret;
578 
579 	if (!sc_die) {
580 		pr_err("Caller must pass a scope DIE. Program error.\n");
581 		return -EINVAL;
582 	}
583 
584 	/* If not a real subprogram, find a real one */
585 	if (!die_is_func_def(sc_die)) {
586 		if (!die_find_realfunc(&pf->cu_die, pf->addr, &pf->sp_die)) {
587 			if (die_find_tailfunc(&pf->cu_die, pf->addr, &pf->sp_die)) {
588 				pr_warning("Ignoring tail call from %s\n",
589 						dwarf_diename(&pf->sp_die));
590 				return 0;
591 			} else {
592 				pr_warning("Failed to find probe point in any "
593 					   "functions.\n");
594 				return -ENOENT;
595 			}
596 		}
597 	} else
598 		memcpy(&pf->sp_die, sc_die, sizeof(Dwarf_Die));
599 
600 	/* Get the frame base attribute/ops from subprogram */
601 	dwarf_attr(&pf->sp_die, DW_AT_frame_base, &fb_attr);
602 	ret = dwarf_getlocation_addr(&fb_attr, pf->addr, &pf->fb_ops, &nops, 1);
603 	if (ret <= 0 || nops == 0) {
604 		pf->fb_ops = NULL;
605 #ifdef HAVE_DWARF_CFI_SUPPORT
606 	} else if (nops == 1 && pf->fb_ops[0].atom == DW_OP_call_frame_cfa &&
607 		   (pf->cfi_eh != NULL || pf->cfi_dbg != NULL)) {
608 		if ((dwarf_cfi_addrframe(pf->cfi_eh, pf->addr, &frame) != 0 &&
609 		     (dwarf_cfi_addrframe(pf->cfi_dbg, pf->addr, &frame) != 0)) ||
610 		    dwarf_frame_cfa(frame, &pf->fb_ops, &nops) != 0) {
611 			pr_warning("Failed to get call frame on 0x%jx\n",
612 				   (uintmax_t)pf->addr);
613 			free(frame);
614 			return -ENOENT;
615 		}
616 #endif /* HAVE_DWARF_CFI_SUPPORT */
617 	}
618 
619 	/* Call finder's callback handler */
620 	ret = pf->callback(sc_die, pf);
621 
622 	/* Since *pf->fb_ops can be a part of frame. we should free it here. */
623 	free(frame);
624 	pf->fb_ops = NULL;
625 
626 	return ret;
627 }
628 
629 struct find_scope_param {
630 	const char *function;
631 	const char *file;
632 	int line;
633 	int diff;
634 	Dwarf_Die *die_mem;
635 	bool found;
636 };
637 
find_best_scope_cb(Dwarf_Die * fn_die,void * data)638 static int find_best_scope_cb(Dwarf_Die *fn_die, void *data)
639 {
640 	struct find_scope_param *fsp = data;
641 	const char *file;
642 	int lno;
643 
644 	/* Skip if declared file name does not match */
645 	if (fsp->file) {
646 		file = die_get_decl_file(fn_die);
647 		if (!file || strcmp(fsp->file, file) != 0)
648 			return 0;
649 	}
650 	/* If the function name is given, that's what user expects */
651 	if (fsp->function) {
652 		if (die_match_name(fn_die, fsp->function)) {
653 			memcpy(fsp->die_mem, fn_die, sizeof(Dwarf_Die));
654 			fsp->found = true;
655 			return 1;
656 		}
657 	} else {
658 		/* With the line number, find the nearest declared DIE */
659 		dwarf_decl_line(fn_die, &lno);
660 		if (lno < fsp->line && fsp->diff > fsp->line - lno) {
661 			/* Keep a candidate and continue */
662 			fsp->diff = fsp->line - lno;
663 			memcpy(fsp->die_mem, fn_die, sizeof(Dwarf_Die));
664 			fsp->found = true;
665 		}
666 	}
667 	return 0;
668 }
669 
670 /* Return innermost DIE */
find_inner_scope_cb(Dwarf_Die * fn_die,void * data)671 static int find_inner_scope_cb(Dwarf_Die *fn_die, void *data)
672 {
673 	struct find_scope_param *fsp = data;
674 
675 	memcpy(fsp->die_mem, fn_die, sizeof(Dwarf_Die));
676 	fsp->found = true;
677 	return 1;
678 }
679 
680 /* Find an appropriate scope fits to given conditions */
find_best_scope(struct probe_finder * pf,Dwarf_Die * die_mem)681 static Dwarf_Die *find_best_scope(struct probe_finder *pf, Dwarf_Die *die_mem)
682 {
683 	struct find_scope_param fsp = {
684 		.function = pf->pev->point.function,
685 		.file = pf->fname,
686 		.line = pf->lno,
687 		.diff = INT_MAX,
688 		.die_mem = die_mem,
689 		.found = false,
690 	};
691 	int ret;
692 
693 	ret = cu_walk_functions_at(&pf->cu_die, pf->addr, find_best_scope_cb,
694 				   &fsp);
695 	if (!ret && !fsp.found)
696 		cu_walk_functions_at(&pf->cu_die, pf->addr,
697 				     find_inner_scope_cb, &fsp);
698 
699 	return fsp.found ? die_mem : NULL;
700 }
701 
verify_representive_line(struct probe_finder * pf,const char * fname,int lineno,Dwarf_Addr addr)702 static int verify_representive_line(struct probe_finder *pf, const char *fname,
703 				int lineno, Dwarf_Addr addr)
704 {
705 	const char *__fname, *__func = NULL;
706 	Dwarf_Die die_mem;
707 	int __lineno;
708 
709 	/* Verify line number and address by reverse search */
710 	if (cu_find_lineinfo(&pf->cu_die, addr, &__fname, &__lineno) < 0)
711 		return 0;
712 
713 	pr_debug2("Reversed line: %s:%d\n", __fname, __lineno);
714 	if (strcmp(fname, __fname) || lineno == __lineno)
715 		return 0;
716 
717 	pr_warning("This line is sharing the address with other lines.\n");
718 
719 	if (pf->pev->point.function) {
720 		/* Find best match function name and lines */
721 		pf->addr = addr;
722 		if (find_best_scope(pf, &die_mem)
723 		    && die_match_name(&die_mem, pf->pev->point.function)
724 		    && dwarf_decl_line(&die_mem, &lineno) == 0) {
725 			__func = dwarf_diename(&die_mem);
726 			__lineno -= lineno;
727 		}
728 	}
729 	pr_warning("Please try to probe at %s:%d instead.\n",
730 		   __func ? : __fname, __lineno);
731 
732 	return -ENOENT;
733 }
734 
probe_point_line_walker(const char * fname,int lineno,Dwarf_Addr addr,void * data)735 static int probe_point_line_walker(const char *fname, int lineno,
736 				   Dwarf_Addr addr, void *data)
737 {
738 	struct probe_finder *pf = data;
739 	Dwarf_Die *sc_die, die_mem;
740 	int ret;
741 
742 	if (lineno != pf->lno || strtailcmp(fname, pf->fname) != 0)
743 		return 0;
744 
745 	if (verify_representive_line(pf, fname, lineno, addr))
746 		return -ENOENT;
747 
748 	pf->addr = addr;
749 	sc_die = find_best_scope(pf, &die_mem);
750 	if (!sc_die) {
751 		pr_warning("Failed to find scope of probe point.\n");
752 		return -ENOENT;
753 	}
754 
755 	ret = call_probe_finder(sc_die, pf);
756 
757 	/* Continue if no error, because the line will be in inline function */
758 	return ret < 0 ? ret : 0;
759 }
760 
761 /* Find probe point from its line number */
find_probe_point_by_line(struct probe_finder * pf)762 static int find_probe_point_by_line(struct probe_finder *pf)
763 {
764 	return die_walk_lines(&pf->cu_die, probe_point_line_walker, pf);
765 }
766 
767 /* Find lines which match lazy pattern */
find_lazy_match_lines(struct intlist * list,const char * fname,const char * pat)768 static int find_lazy_match_lines(struct intlist *list,
769 				 const char *fname, const char *pat)
770 {
771 	FILE *fp;
772 	char *line = NULL;
773 	size_t line_len;
774 	ssize_t len;
775 	int count = 0, linenum = 1;
776 	char sbuf[STRERR_BUFSIZE];
777 
778 	fp = fopen(fname, "r");
779 	if (!fp) {
780 		pr_warning("Failed to open %s: %s\n", fname,
781 			   str_error_r(errno, sbuf, sizeof(sbuf)));
782 		return -errno;
783 	}
784 
785 	while ((len = getline(&line, &line_len, fp)) > 0) {
786 
787 		if (line[len - 1] == '\n')
788 			line[len - 1] = '\0';
789 
790 		if (strlazymatch(line, pat)) {
791 			intlist__add(list, linenum);
792 			count++;
793 		}
794 		linenum++;
795 	}
796 
797 	if (ferror(fp))
798 		count = -errno;
799 	free(line);
800 	fclose(fp);
801 
802 	if (count == 0)
803 		pr_debug("No matched lines found in %s.\n", fname);
804 	return count;
805 }
806 
probe_point_lazy_walker(const char * fname,int lineno,Dwarf_Addr addr,void * data)807 static int probe_point_lazy_walker(const char *fname, int lineno,
808 				   Dwarf_Addr addr, void *data)
809 {
810 	struct probe_finder *pf = data;
811 	Dwarf_Die *sc_die, die_mem;
812 	int ret;
813 
814 	if (!intlist__has_entry(pf->lcache, lineno) ||
815 	    strtailcmp(fname, pf->fname) != 0)
816 		return 0;
817 
818 	pr_debug("Probe line found: line:%d addr:0x%llx\n",
819 		 lineno, (unsigned long long)addr);
820 	pf->addr = addr;
821 	pf->lno = lineno;
822 	sc_die = find_best_scope(pf, &die_mem);
823 	if (!sc_die) {
824 		pr_warning("Failed to find scope of probe point.\n");
825 		return -ENOENT;
826 	}
827 
828 	ret = call_probe_finder(sc_die, pf);
829 
830 	/*
831 	 * Continue if no error, because the lazy pattern will match
832 	 * to other lines
833 	 */
834 	return ret < 0 ? ret : 0;
835 }
836 
837 /* Find probe points from lazy pattern  */
find_probe_point_lazy(Dwarf_Die * sp_die,struct probe_finder * pf)838 static int find_probe_point_lazy(Dwarf_Die *sp_die, struct probe_finder *pf)
839 {
840 	struct build_id bid;
841 	char sbuild_id[SBUILD_ID_SIZE] = "";
842 	int ret = 0;
843 	char *fpath;
844 
845 	if (intlist__empty(pf->lcache)) {
846 		const char *comp_dir;
847 
848 		comp_dir = cu_get_comp_dir(&pf->cu_die);
849 		if (pf->dbg->build_id) {
850 			build_id__init(&bid, pf->dbg->build_id, BUILD_ID_SIZE);
851 			build_id__sprintf(&bid, sbuild_id);
852 		}
853 		ret = find_source_path(pf->fname, sbuild_id, comp_dir, &fpath);
854 		if (ret < 0) {
855 			pr_warning("Failed to find source file path.\n");
856 			return ret;
857 		}
858 
859 		/* Matching lazy line pattern */
860 		ret = find_lazy_match_lines(pf->lcache, fpath,
861 					    pf->pev->point.lazy_line);
862 		free(fpath);
863 		if (ret <= 0)
864 			return ret;
865 	}
866 
867 	return die_walk_lines(sp_die, probe_point_lazy_walker, pf);
868 }
869 
skip_prologue(Dwarf_Die * sp_die,struct probe_finder * pf)870 static void skip_prologue(Dwarf_Die *sp_die, struct probe_finder *pf)
871 {
872 	struct perf_probe_point *pp = &pf->pev->point;
873 
874 	/* Not uprobe? */
875 	if (!pf->pev->uprobes)
876 		return;
877 
878 	/* Compiled with optimization? */
879 	if (die_is_optimized_target(&pf->cu_die))
880 		return;
881 
882 	/* Don't know entrypc? */
883 	if (!pf->addr)
884 		return;
885 
886 	/* Only FUNC and FUNC@SRC are eligible. */
887 	if (!pp->function || pp->line || pp->retprobe || pp->lazy_line ||
888 	    pp->offset || pp->abs_address)
889 		return;
890 
891 	/* Not interested in func parameter? */
892 	if (!perf_probe_with_var(pf->pev))
893 		return;
894 
895 	pr_info("Target program is compiled without optimization. Skipping prologue.\n"
896 		"Probe on address 0x%" PRIx64 " to force probing at the function entry.\n\n",
897 		pf->addr);
898 
899 	die_skip_prologue(sp_die, &pf->cu_die, &pf->addr);
900 }
901 
probe_point_inline_cb(Dwarf_Die * in_die,void * data)902 static int probe_point_inline_cb(Dwarf_Die *in_die, void *data)
903 {
904 	struct probe_finder *pf = data;
905 	struct perf_probe_point *pp = &pf->pev->point;
906 	Dwarf_Addr addr;
907 	int ret;
908 
909 	if (pp->lazy_line)
910 		ret = find_probe_point_lazy(in_die, pf);
911 	else {
912 		/* Get probe address */
913 		if (die_entrypc(in_die, &addr) != 0) {
914 			pr_warning("Failed to get entry address of %s.\n",
915 				   dwarf_diename(in_die));
916 			return -ENOENT;
917 		}
918 		if (addr == 0) {
919 			pr_debug("%s has no valid entry address. skipped.\n",
920 				 dwarf_diename(in_die));
921 			return -ENOENT;
922 		}
923 		pf->addr = addr;
924 		pf->addr += pp->offset;
925 		pr_debug("found inline addr: 0x%jx\n",
926 			 (uintmax_t)pf->addr);
927 
928 		ret = call_probe_finder(in_die, pf);
929 	}
930 
931 	return ret;
932 }
933 
934 /* Callback parameter with return value for libdw */
935 struct dwarf_callback_param {
936 	void *data;
937 	int retval;
938 };
939 
940 /* Search function from function name */
probe_point_search_cb(Dwarf_Die * sp_die,void * data)941 static int probe_point_search_cb(Dwarf_Die *sp_die, void *data)
942 {
943 	struct dwarf_callback_param *param = data;
944 	struct probe_finder *pf = param->data;
945 	struct perf_probe_point *pp = &pf->pev->point;
946 	const char *fname;
947 
948 	/* Check tag and diename */
949 	if (!die_is_func_def(sp_die) ||
950 	    !die_match_name(sp_die, pp->function))
951 		return DWARF_CB_OK;
952 
953 	/* Check declared file */
954 	fname = die_get_decl_file(sp_die);
955 	if (!fname) {
956 		pr_warning("A function DIE doesn't have decl_line. Maybe broken DWARF?\n");
957 		return DWARF_CB_OK;
958 	}
959 	if (pp->file && fname && strtailcmp(pp->file, fname))
960 		return DWARF_CB_OK;
961 
962 	pr_debug("Matched function: %s [%lx]\n", dwarf_diename(sp_die),
963 		 (unsigned long)dwarf_dieoffset(sp_die));
964 	pf->fname = fname;
965 	if (pp->line) { /* Function relative line */
966 		dwarf_decl_line(sp_die, &pf->lno);
967 		pf->lno += pp->line;
968 		param->retval = find_probe_point_by_line(pf);
969 	} else if (die_is_func_instance(sp_die)) {
970 		/* Instances always have the entry address */
971 		die_entrypc(sp_die, &pf->addr);
972 		/* But in some case the entry address is 0 */
973 		if (pf->addr == 0) {
974 			pr_debug("%s has no entry PC. Skipped\n",
975 				 dwarf_diename(sp_die));
976 			param->retval = 0;
977 		/* Real function */
978 		} else if (pp->lazy_line)
979 			param->retval = find_probe_point_lazy(sp_die, pf);
980 		else {
981 			skip_prologue(sp_die, pf);
982 			pf->addr += pp->offset;
983 			/* TODO: Check the address in this function */
984 			param->retval = call_probe_finder(sp_die, pf);
985 		}
986 	} else if (!probe_conf.no_inlines) {
987 		/* Inlined function: search instances */
988 		param->retval = die_walk_instances(sp_die,
989 					probe_point_inline_cb, (void *)pf);
990 		/* This could be a non-existed inline definition */
991 		if (param->retval == -ENOENT)
992 			param->retval = 0;
993 	}
994 
995 	/* We need to find other candidates */
996 	if (strisglob(pp->function) && param->retval >= 0) {
997 		param->retval = 0;	/* We have to clear the result */
998 		return DWARF_CB_OK;
999 	}
1000 
1001 	return DWARF_CB_ABORT; /* Exit; no same symbol in this CU. */
1002 }
1003 
find_probe_point_by_func(struct probe_finder * pf)1004 static int find_probe_point_by_func(struct probe_finder *pf)
1005 {
1006 	struct dwarf_callback_param _param = {.data = (void *)pf,
1007 					      .retval = 0};
1008 	dwarf_getfuncs(&pf->cu_die, probe_point_search_cb, &_param, 0);
1009 	return _param.retval;
1010 }
1011 
1012 struct pubname_callback_param {
1013 	char *function;
1014 	char *file;
1015 	Dwarf_Die *cu_die;
1016 	Dwarf_Die *sp_die;
1017 	int found;
1018 };
1019 
pubname_search_cb(Dwarf * dbg,Dwarf_Global * gl,void * data)1020 static int pubname_search_cb(Dwarf *dbg, Dwarf_Global *gl, void *data)
1021 {
1022 	struct pubname_callback_param *param = data;
1023 	const char *fname;
1024 
1025 	if (dwarf_offdie(dbg, gl->die_offset, param->sp_die)) {
1026 		if (dwarf_tag(param->sp_die) != DW_TAG_subprogram)
1027 			return DWARF_CB_OK;
1028 
1029 		if (die_match_name(param->sp_die, param->function)) {
1030 			if (!dwarf_offdie(dbg, gl->cu_offset, param->cu_die))
1031 				return DWARF_CB_OK;
1032 
1033 			if (param->file) {
1034 				fname = die_get_decl_file(param->sp_die);
1035 				if (!fname || strtailcmp(param->file, fname))
1036 					return DWARF_CB_OK;
1037 			}
1038 
1039 			param->found = 1;
1040 			return DWARF_CB_ABORT;
1041 		}
1042 	}
1043 
1044 	return DWARF_CB_OK;
1045 }
1046 
debuginfo__find_probe_location(struct debuginfo * dbg,struct probe_finder * pf)1047 static int debuginfo__find_probe_location(struct debuginfo *dbg,
1048 				  struct probe_finder *pf)
1049 {
1050 	struct perf_probe_point *pp = &pf->pev->point;
1051 	Dwarf_Off off, noff;
1052 	size_t cuhl;
1053 	Dwarf_Die *diep;
1054 	int ret = 0;
1055 
1056 	off = 0;
1057 	pf->lcache = intlist__new(NULL);
1058 	if (!pf->lcache)
1059 		return -ENOMEM;
1060 
1061 	/* Fastpath: lookup by function name from .debug_pubnames section */
1062 	if (pp->function && !strisglob(pp->function)) {
1063 		struct pubname_callback_param pubname_param = {
1064 			.function = pp->function,
1065 			.file	  = pp->file,
1066 			.cu_die	  = &pf->cu_die,
1067 			.sp_die	  = &pf->sp_die,
1068 			.found	  = 0,
1069 		};
1070 		struct dwarf_callback_param probe_param = {
1071 			.data = pf,
1072 		};
1073 
1074 		dwarf_getpubnames(dbg->dbg, pubname_search_cb,
1075 				  &pubname_param, 0);
1076 		if (pubname_param.found) {
1077 			ret = probe_point_search_cb(&pf->sp_die, &probe_param);
1078 			if (ret)
1079 				goto found;
1080 		}
1081 	}
1082 
1083 	/* Loop on CUs (Compilation Unit) */
1084 	while (!dwarf_nextcu(dbg->dbg, off, &noff, &cuhl, NULL, NULL, NULL)) {
1085 		/* Get the DIE(Debugging Information Entry) of this CU */
1086 		diep = dwarf_offdie(dbg->dbg, off + cuhl, &pf->cu_die);
1087 		if (!diep) {
1088 			off = noff;
1089 			continue;
1090 		}
1091 
1092 		/* Check if target file is included. */
1093 		if (pp->file)
1094 			pf->fname = cu_find_realpath(&pf->cu_die, pp->file);
1095 		else
1096 			pf->fname = NULL;
1097 
1098 		if (!pp->file || pf->fname) {
1099 			if (pp->function)
1100 				ret = find_probe_point_by_func(pf);
1101 			else if (pp->lazy_line)
1102 				ret = find_probe_point_lazy(&pf->cu_die, pf);
1103 			else {
1104 				pf->lno = pp->line;
1105 				ret = find_probe_point_by_line(pf);
1106 			}
1107 			if (ret < 0)
1108 				break;
1109 		}
1110 		off = noff;
1111 	}
1112 
1113 found:
1114 	intlist__delete(pf->lcache);
1115 	pf->lcache = NULL;
1116 
1117 	return ret;
1118 }
1119 
1120 /* Find probe points from debuginfo */
debuginfo__find_probes(struct debuginfo * dbg,struct probe_finder * pf)1121 static int debuginfo__find_probes(struct debuginfo *dbg,
1122 				  struct probe_finder *pf)
1123 {
1124 	int ret = 0;
1125 	Elf *elf;
1126 	GElf_Ehdr ehdr;
1127 
1128 	if (pf->cfi_eh || pf->cfi_dbg)
1129 		return debuginfo__find_probe_location(dbg, pf);
1130 
1131 	/* Get the call frame information from this dwarf */
1132 	elf = dwarf_getelf(dbg->dbg);
1133 	if (elf == NULL)
1134 		return -EINVAL;
1135 
1136 	if (gelf_getehdr(elf, &ehdr) == NULL)
1137 		return -EINVAL;
1138 
1139 	pf->machine = ehdr.e_machine;
1140 
1141 #ifdef HAVE_DWARF_CFI_SUPPORT
1142 	do {
1143 		GElf_Shdr shdr;
1144 
1145 		if (elf_section_by_name(elf, &ehdr, &shdr, ".eh_frame", NULL) &&
1146 		    shdr.sh_type == SHT_PROGBITS)
1147 			pf->cfi_eh = dwarf_getcfi_elf(elf);
1148 
1149 		pf->cfi_dbg = dwarf_getcfi(dbg->dbg);
1150 	} while (0);
1151 #endif /* HAVE_DWARF_CFI_SUPPORT */
1152 
1153 	ret = debuginfo__find_probe_location(dbg, pf);
1154 	return ret;
1155 }
1156 
1157 struct local_vars_finder {
1158 	struct probe_finder *pf;
1159 	struct perf_probe_arg *args;
1160 	bool vars;
1161 	int max_args;
1162 	int nargs;
1163 	int ret;
1164 };
1165 
1166 /* Collect available variables in this scope */
copy_variables_cb(Dwarf_Die * die_mem,void * data)1167 static int copy_variables_cb(Dwarf_Die *die_mem, void *data)
1168 {
1169 	struct local_vars_finder *vf = data;
1170 	struct probe_finder *pf = vf->pf;
1171 	int tag;
1172 
1173 	tag = dwarf_tag(die_mem);
1174 	if (tag == DW_TAG_formal_parameter ||
1175 	    (tag == DW_TAG_variable && vf->vars)) {
1176 		if (convert_variable_location(die_mem, vf->pf->addr,
1177 					      vf->pf->fb_ops, &pf->sp_die,
1178 					      pf->machine, NULL) == 0) {
1179 			vf->args[vf->nargs].var = (char *)dwarf_diename(die_mem);
1180 			if (vf->args[vf->nargs].var == NULL) {
1181 				vf->ret = -ENOMEM;
1182 				return DIE_FIND_CB_END;
1183 			}
1184 			pr_debug(" %s", vf->args[vf->nargs].var);
1185 			vf->nargs++;
1186 		}
1187 	}
1188 
1189 	if (dwarf_haspc(die_mem, vf->pf->addr))
1190 		return DIE_FIND_CB_CONTINUE;
1191 	else
1192 		return DIE_FIND_CB_SIBLING;
1193 }
1194 
expand_probe_args(Dwarf_Die * sc_die,struct probe_finder * pf,struct perf_probe_arg * args)1195 static int expand_probe_args(Dwarf_Die *sc_die, struct probe_finder *pf,
1196 			     struct perf_probe_arg *args)
1197 {
1198 	Dwarf_Die die_mem;
1199 	int i;
1200 	int n = 0;
1201 	struct local_vars_finder vf = {.pf = pf, .args = args, .vars = false,
1202 				.max_args = MAX_PROBE_ARGS, .ret = 0};
1203 
1204 	for (i = 0; i < pf->pev->nargs; i++) {
1205 		/* var never be NULL */
1206 		if (strcmp(pf->pev->args[i].var, PROBE_ARG_VARS) == 0)
1207 			vf.vars = true;
1208 		else if (strcmp(pf->pev->args[i].var, PROBE_ARG_PARAMS) != 0) {
1209 			/* Copy normal argument */
1210 			args[n] = pf->pev->args[i];
1211 			n++;
1212 			continue;
1213 		}
1214 		pr_debug("Expanding %s into:", pf->pev->args[i].var);
1215 		vf.nargs = n;
1216 		/* Special local variables */
1217 		die_find_child(sc_die, copy_variables_cb, (void *)&vf,
1218 			       &die_mem);
1219 		pr_debug(" (%d)\n", vf.nargs - n);
1220 		if (vf.ret < 0)
1221 			return vf.ret;
1222 		n = vf.nargs;
1223 	}
1224 	return n;
1225 }
1226 
trace_event_finder_overlap(struct trace_event_finder * tf)1227 static bool trace_event_finder_overlap(struct trace_event_finder *tf)
1228 {
1229 	int i;
1230 
1231 	for (i = 0; i < tf->ntevs; i++) {
1232 		if (tf->pf.addr == tf->tevs[i].point.address)
1233 			return true;
1234 	}
1235 	return false;
1236 }
1237 
1238 /* Add a found probe point into trace event list */
add_probe_trace_event(Dwarf_Die * sc_die,struct probe_finder * pf)1239 static int add_probe_trace_event(Dwarf_Die *sc_die, struct probe_finder *pf)
1240 {
1241 	struct trace_event_finder *tf =
1242 			container_of(pf, struct trace_event_finder, pf);
1243 	struct perf_probe_point *pp = &pf->pev->point;
1244 	struct probe_trace_event *tev;
1245 	struct perf_probe_arg *args = NULL;
1246 	int ret, i;
1247 
1248 	/*
1249 	 * For some reason (e.g. different column assigned to same address)
1250 	 * This callback can be called with the address which already passed.
1251 	 * Ignore it first.
1252 	 */
1253 	if (trace_event_finder_overlap(tf))
1254 		return 0;
1255 
1256 	/* Check number of tevs */
1257 	if (tf->ntevs == tf->max_tevs) {
1258 		pr_warning("Too many( > %d) probe point found.\n",
1259 			   tf->max_tevs);
1260 		return -ERANGE;
1261 	}
1262 	tev = &tf->tevs[tf->ntevs++];
1263 
1264 	/* Trace point should be converted from subprogram DIE */
1265 	ret = convert_to_trace_point(&pf->sp_die, tf->mod, pf->addr,
1266 				     pp->retprobe, pp->function, &tev->point);
1267 	if (ret < 0)
1268 		goto end;
1269 
1270 	tev->point.realname = strdup(dwarf_diename(sc_die));
1271 	if (!tev->point.realname) {
1272 		ret = -ENOMEM;
1273 		goto end;
1274 	}
1275 
1276 	pr_debug("Probe point found: %s+%lu\n", tev->point.symbol,
1277 		 tev->point.offset);
1278 
1279 	/* Expand special probe argument if exist */
1280 	args = zalloc(sizeof(struct perf_probe_arg) * MAX_PROBE_ARGS);
1281 	if (args == NULL) {
1282 		ret = -ENOMEM;
1283 		goto end;
1284 	}
1285 
1286 	ret = expand_probe_args(sc_die, pf, args);
1287 	if (ret < 0)
1288 		goto end;
1289 
1290 	tev->nargs = ret;
1291 	tev->args = zalloc(sizeof(struct probe_trace_arg) * tev->nargs);
1292 	if (tev->args == NULL) {
1293 		ret = -ENOMEM;
1294 		goto end;
1295 	}
1296 
1297 	/* Find each argument */
1298 	for (i = 0; i < tev->nargs; i++) {
1299 		pf->pvar = &args[i];
1300 		pf->tvar = &tev->args[i];
1301 		/* Variable should be found from scope DIE */
1302 		ret = find_variable(sc_die, pf);
1303 		if (ret != 0)
1304 			break;
1305 	}
1306 
1307 end:
1308 	if (ret) {
1309 		clear_probe_trace_event(tev);
1310 		tf->ntevs--;
1311 	}
1312 	free(args);
1313 	return ret;
1314 }
1315 
fill_empty_trace_arg(struct perf_probe_event * pev,struct probe_trace_event * tevs,int ntevs)1316 static int fill_empty_trace_arg(struct perf_probe_event *pev,
1317 				struct probe_trace_event *tevs, int ntevs)
1318 {
1319 	char **valp;
1320 	char *type;
1321 	int i, j, ret;
1322 
1323 	if (!ntevs)
1324 		return -ENOENT;
1325 
1326 	for (i = 0; i < pev->nargs; i++) {
1327 		type = NULL;
1328 		for (j = 0; j < ntevs; j++) {
1329 			if (tevs[j].args[i].value) {
1330 				type = tevs[j].args[i].type;
1331 				break;
1332 			}
1333 		}
1334 		if (j == ntevs) {
1335 			print_var_not_found(pev->args[i].var);
1336 			return -ENOENT;
1337 		}
1338 		for (j = 0; j < ntevs; j++) {
1339 			valp = &tevs[j].args[i].value;
1340 			if (*valp)
1341 				continue;
1342 
1343 			ret = asprintf(valp, "\\%lx", probe_conf.magic_num);
1344 			if (ret < 0)
1345 				return -ENOMEM;
1346 			/* Note that type can be NULL */
1347 			if (type) {
1348 				tevs[j].args[i].type = strdup(type);
1349 				if (!tevs[j].args[i].type)
1350 					return -ENOMEM;
1351 			}
1352 		}
1353 	}
1354 	return 0;
1355 }
1356 
1357 /* Find probe_trace_events specified by perf_probe_event from debuginfo */
debuginfo__find_trace_events(struct debuginfo * dbg,struct perf_probe_event * pev,struct probe_trace_event ** tevs)1358 int debuginfo__find_trace_events(struct debuginfo *dbg,
1359 				 struct perf_probe_event *pev,
1360 				 struct probe_trace_event **tevs)
1361 {
1362 	struct trace_event_finder tf = {
1363 			.pf = {.pev = pev, .dbg = dbg, .callback = add_probe_trace_event},
1364 			.max_tevs = probe_conf.max_probes, .mod = dbg->mod};
1365 	int ret, i;
1366 
1367 	/* Allocate result tevs array */
1368 	*tevs = zalloc(sizeof(struct probe_trace_event) * tf.max_tevs);
1369 	if (*tevs == NULL)
1370 		return -ENOMEM;
1371 
1372 	tf.tevs = *tevs;
1373 	tf.ntevs = 0;
1374 
1375 	if (pev->nargs != 0 && immediate_value_is_supported())
1376 		tf.pf.skip_empty_arg = true;
1377 
1378 	ret = debuginfo__find_probes(dbg, &tf.pf);
1379 	if (ret >= 0 && tf.pf.skip_empty_arg)
1380 		ret = fill_empty_trace_arg(pev, tf.tevs, tf.ntevs);
1381 
1382 	if (ret < 0 || tf.ntevs == 0) {
1383 		for (i = 0; i < tf.ntevs; i++)
1384 			clear_probe_trace_event(&tf.tevs[i]);
1385 		zfree(tevs);
1386 		return ret;
1387 	}
1388 
1389 	return (ret < 0) ? ret : tf.ntevs;
1390 }
1391 
1392 /* Collect available variables in this scope */
collect_variables_cb(Dwarf_Die * die_mem,void * data)1393 static int collect_variables_cb(Dwarf_Die *die_mem, void *data)
1394 {
1395 	struct available_var_finder *af = data;
1396 	struct variable_list *vl;
1397 	struct strbuf buf = STRBUF_INIT;
1398 	int tag, ret;
1399 
1400 	vl = &af->vls[af->nvls - 1];
1401 
1402 	tag = dwarf_tag(die_mem);
1403 	if (tag == DW_TAG_formal_parameter ||
1404 	    tag == DW_TAG_variable) {
1405 		ret = convert_variable_location(die_mem, af->pf.addr,
1406 						af->pf.fb_ops, &af->pf.sp_die,
1407 						af->pf.machine, NULL);
1408 		if (ret == 0 || ret == -ERANGE) {
1409 			int ret2;
1410 			bool externs = !af->child;
1411 
1412 			if (strbuf_init(&buf, 64) < 0)
1413 				goto error;
1414 
1415 			if (probe_conf.show_location_range) {
1416 				if (!externs)
1417 					ret2 = strbuf_add(&buf,
1418 						ret ? "[INV]\t" : "[VAL]\t", 6);
1419 				else
1420 					ret2 = strbuf_add(&buf, "[EXT]\t", 6);
1421 				if (ret2)
1422 					goto error;
1423 			}
1424 
1425 			ret2 = die_get_varname(die_mem, &buf);
1426 
1427 			if (!ret2 && probe_conf.show_location_range &&
1428 				!externs) {
1429 				if (strbuf_addch(&buf, '\t') < 0)
1430 					goto error;
1431 				ret2 = die_get_var_range(&af->pf.sp_die,
1432 							die_mem, &buf);
1433 			}
1434 
1435 			pr_debug("Add new var: %s\n", buf.buf);
1436 			if (ret2 == 0) {
1437 				strlist__add(vl->vars,
1438 					strbuf_detach(&buf, NULL));
1439 			}
1440 			strbuf_release(&buf);
1441 		}
1442 	}
1443 
1444 	if (af->child && dwarf_haspc(die_mem, af->pf.addr))
1445 		return DIE_FIND_CB_CONTINUE;
1446 	else
1447 		return DIE_FIND_CB_SIBLING;
1448 error:
1449 	strbuf_release(&buf);
1450 	pr_debug("Error in strbuf\n");
1451 	return DIE_FIND_CB_END;
1452 }
1453 
available_var_finder_overlap(struct available_var_finder * af)1454 static bool available_var_finder_overlap(struct available_var_finder *af)
1455 {
1456 	int i;
1457 
1458 	for (i = 0; i < af->nvls; i++) {
1459 		if (af->pf.addr == af->vls[i].point.address)
1460 			return true;
1461 	}
1462 	return false;
1463 
1464 }
1465 
1466 /* Add a found vars into available variables list */
add_available_vars(Dwarf_Die * sc_die,struct probe_finder * pf)1467 static int add_available_vars(Dwarf_Die *sc_die, struct probe_finder *pf)
1468 {
1469 	struct available_var_finder *af =
1470 			container_of(pf, struct available_var_finder, pf);
1471 	struct perf_probe_point *pp = &pf->pev->point;
1472 	struct variable_list *vl;
1473 	Dwarf_Die die_mem;
1474 	int ret;
1475 
1476 	/*
1477 	 * For some reason (e.g. different column assigned to same address),
1478 	 * this callback can be called with the address which already passed.
1479 	 * Ignore it first.
1480 	 */
1481 	if (available_var_finder_overlap(af))
1482 		return 0;
1483 
1484 	/* Check number of tevs */
1485 	if (af->nvls == af->max_vls) {
1486 		pr_warning("Too many( > %d) probe point found.\n", af->max_vls);
1487 		return -ERANGE;
1488 	}
1489 	vl = &af->vls[af->nvls++];
1490 
1491 	/* Trace point should be converted from subprogram DIE */
1492 	ret = convert_to_trace_point(&pf->sp_die, af->mod, pf->addr,
1493 				     pp->retprobe, pp->function, &vl->point);
1494 	if (ret < 0)
1495 		return ret;
1496 
1497 	pr_debug("Probe point found: %s+%lu\n", vl->point.symbol,
1498 		 vl->point.offset);
1499 
1500 	/* Find local variables */
1501 	vl->vars = strlist__new(NULL, NULL);
1502 	if (vl->vars == NULL)
1503 		return -ENOMEM;
1504 	af->child = true;
1505 	die_find_child(sc_die, collect_variables_cb, (void *)af, &die_mem);
1506 
1507 	/* Find external variables */
1508 	if (!probe_conf.show_ext_vars)
1509 		goto out;
1510 	/* Don't need to search child DIE for external vars. */
1511 	af->child = false;
1512 	die_find_child(&pf->cu_die, collect_variables_cb, (void *)af, &die_mem);
1513 
1514 out:
1515 	if (strlist__empty(vl->vars)) {
1516 		strlist__delete(vl->vars);
1517 		vl->vars = NULL;
1518 	}
1519 
1520 	return ret;
1521 }
1522 
1523 /*
1524  * Find available variables at given probe point
1525  * Return the number of found probe points. Return 0 if there is no
1526  * matched probe point. Return <0 if an error occurs.
1527  */
debuginfo__find_available_vars_at(struct debuginfo * dbg,struct perf_probe_event * pev,struct variable_list ** vls)1528 int debuginfo__find_available_vars_at(struct debuginfo *dbg,
1529 				      struct perf_probe_event *pev,
1530 				      struct variable_list **vls)
1531 {
1532 	struct available_var_finder af = {
1533 			.pf = {.pev = pev, .dbg = dbg, .callback = add_available_vars},
1534 			.mod = dbg->mod,
1535 			.max_vls = probe_conf.max_probes};
1536 	int ret;
1537 
1538 	/* Allocate result vls array */
1539 	*vls = zalloc(sizeof(struct variable_list) * af.max_vls);
1540 	if (*vls == NULL)
1541 		return -ENOMEM;
1542 
1543 	af.vls = *vls;
1544 	af.nvls = 0;
1545 
1546 	ret = debuginfo__find_probes(dbg, &af.pf);
1547 	if (ret < 0) {
1548 		/* Free vlist for error */
1549 		while (af.nvls--) {
1550 			zfree(&af.vls[af.nvls].point.symbol);
1551 			strlist__delete(af.vls[af.nvls].vars);
1552 		}
1553 		zfree(vls);
1554 		return ret;
1555 	}
1556 
1557 	return (ret < 0) ? ret : af.nvls;
1558 }
1559 
1560 /* Reverse search */
debuginfo__find_probe_point(struct debuginfo * dbg,u64 addr,struct perf_probe_point * ppt)1561 int debuginfo__find_probe_point(struct debuginfo *dbg, u64 addr,
1562 				struct perf_probe_point *ppt)
1563 {
1564 	Dwarf_Die cudie, spdie, indie;
1565 	Dwarf_Addr _addr = 0, baseaddr = 0;
1566 	const char *fname = NULL, *func = NULL, *basefunc = NULL, *tmp;
1567 	int baseline = 0, lineno = 0, ret = 0;
1568 
1569 	/* We always need to relocate the address for aranges */
1570 	if (debuginfo__get_text_offset(dbg, &baseaddr, false) == 0)
1571 		addr += baseaddr;
1572 	/* Find cu die */
1573 	if (!dwarf_addrdie(dbg->dbg, (Dwarf_Addr)addr, &cudie)) {
1574 		pr_warning("Failed to find debug information for address %#" PRIx64 "\n",
1575 			   addr);
1576 		ret = -EINVAL;
1577 		goto end;
1578 	}
1579 
1580 	/* Find a corresponding line (filename and lineno) */
1581 	cu_find_lineinfo(&cudie, (Dwarf_Addr)addr, &fname, &lineno);
1582 	/* Don't care whether it failed or not */
1583 
1584 	/* Find a corresponding function (name, baseline and baseaddr) */
1585 	if (die_find_realfunc(&cudie, (Dwarf_Addr)addr, &spdie)) {
1586 		/* Get function entry information */
1587 		func = basefunc = dwarf_diename(&spdie);
1588 		if (!func ||
1589 		    die_entrypc(&spdie, &baseaddr) != 0 ||
1590 		    dwarf_decl_line(&spdie, &baseline) != 0) {
1591 			lineno = 0;
1592 			goto post;
1593 		}
1594 
1595 		fname = die_get_decl_file(&spdie);
1596 		if (addr == baseaddr) {
1597 			/* Function entry - Relative line number is 0 */
1598 			lineno = baseline;
1599 			goto post;
1600 		}
1601 
1602 		/* Track down the inline functions step by step */
1603 		while (die_find_top_inlinefunc(&spdie, (Dwarf_Addr)addr,
1604 						&indie)) {
1605 			/* There is an inline function */
1606 			if (die_entrypc(&indie, &_addr) == 0 &&
1607 			    _addr == addr) {
1608 				/*
1609 				 * addr is at an inline function entry.
1610 				 * In this case, lineno should be the call-site
1611 				 * line number. (overwrite lineinfo)
1612 				 */
1613 				lineno = die_get_call_lineno(&indie);
1614 				fname = die_get_call_file(&indie);
1615 				break;
1616 			} else {
1617 				/*
1618 				 * addr is in an inline function body.
1619 				 * Since lineno points one of the lines
1620 				 * of the inline function, baseline should
1621 				 * be the entry line of the inline function.
1622 				 */
1623 				tmp = dwarf_diename(&indie);
1624 				if (!tmp ||
1625 				    dwarf_decl_line(&indie, &baseline) != 0)
1626 					break;
1627 				func = tmp;
1628 				spdie = indie;
1629 			}
1630 		}
1631 		/* Verify the lineno and baseline are in a same file */
1632 		tmp = die_get_decl_file(&spdie);
1633 		if (!tmp || (fname && strcmp(tmp, fname) != 0))
1634 			lineno = 0;
1635 	}
1636 
1637 post:
1638 	/* Make a relative line number or an offset */
1639 	if (lineno)
1640 		ppt->line = lineno - baseline;
1641 	else if (basefunc) {
1642 		ppt->offset = addr - baseaddr;
1643 		func = basefunc;
1644 	}
1645 
1646 	/* Duplicate strings */
1647 	if (func) {
1648 		ppt->function = strdup(func);
1649 		if (ppt->function == NULL) {
1650 			ret = -ENOMEM;
1651 			goto end;
1652 		}
1653 	}
1654 	if (fname) {
1655 		ppt->file = strdup(fname);
1656 		if (ppt->file == NULL) {
1657 			zfree(&ppt->function);
1658 			ret = -ENOMEM;
1659 			goto end;
1660 		}
1661 	}
1662 end:
1663 	if (ret == 0 && (fname || func))
1664 		ret = 1;	/* Found a point */
1665 	return ret;
1666 }
1667 
1668 /* Add a line and store the src path */
line_range_add_line(const char * src,unsigned int lineno,struct line_range * lr)1669 static int line_range_add_line(const char *src, unsigned int lineno,
1670 			       struct line_range *lr)
1671 {
1672 	/* Copy source path */
1673 	if (!lr->path) {
1674 		lr->path = strdup(src);
1675 		if (lr->path == NULL)
1676 			return -ENOMEM;
1677 	}
1678 	return intlist__add(lr->line_list, lineno);
1679 }
1680 
line_range_walk_cb(const char * fname,int lineno,Dwarf_Addr addr,void * data)1681 static int line_range_walk_cb(const char *fname, int lineno,
1682 			      Dwarf_Addr addr, void *data)
1683 {
1684 	struct line_finder *lf = data;
1685 	const char *__fname;
1686 	int __lineno;
1687 	int err;
1688 
1689 	if ((strtailcmp(fname, lf->fname) != 0) ||
1690 	    (lf->lno_s > lineno || lf->lno_e < lineno))
1691 		return 0;
1692 
1693 	/* Make sure this line can be reversible */
1694 	if (cu_find_lineinfo(&lf->cu_die, addr, &__fname, &__lineno) > 0
1695 	    && (lineno != __lineno || strcmp(fname, __fname)))
1696 		return 0;
1697 
1698 	err = line_range_add_line(fname, lineno, lf->lr);
1699 	if (err < 0 && err != -EEXIST)
1700 		return err;
1701 
1702 	return 0;
1703 }
1704 
1705 /* Find line range from its line number */
find_line_range_by_line(Dwarf_Die * sp_die,struct line_finder * lf)1706 static int find_line_range_by_line(Dwarf_Die *sp_die, struct line_finder *lf)
1707 {
1708 	int ret;
1709 
1710 	ret = die_walk_lines(sp_die ?: &lf->cu_die, line_range_walk_cb, lf);
1711 
1712 	/* Update status */
1713 	if (ret >= 0)
1714 		if (!intlist__empty(lf->lr->line_list))
1715 			ret = lf->found = 1;
1716 		else
1717 			ret = 0;	/* Lines are not found */
1718 	else {
1719 		zfree(&lf->lr->path);
1720 	}
1721 	return ret;
1722 }
1723 
line_range_inline_cb(Dwarf_Die * in_die,void * data)1724 static int line_range_inline_cb(Dwarf_Die *in_die, void *data)
1725 {
1726 	int ret = find_line_range_by_line(in_die, data);
1727 
1728 	/*
1729 	 * We have to check all instances of inlined function, because
1730 	 * some execution paths can be optimized out depends on the
1731 	 * function argument of instances. However, if an error occurs,
1732 	 * it should be handled by the caller.
1733 	 */
1734 	return ret < 0 ? ret : 0;
1735 }
1736 
1737 /* Search function definition from function name */
line_range_search_cb(Dwarf_Die * sp_die,void * data)1738 static int line_range_search_cb(Dwarf_Die *sp_die, void *data)
1739 {
1740 	struct dwarf_callback_param *param = data;
1741 	struct line_finder *lf = param->data;
1742 	struct line_range *lr = lf->lr;
1743 	const char *fname;
1744 
1745 	/* Check declared file */
1746 	if (lr->file) {
1747 		fname = die_get_decl_file(sp_die);
1748 		if (!fname || strtailcmp(lr->file, fname))
1749 			return DWARF_CB_OK;
1750 	}
1751 
1752 	if (die_match_name(sp_die, lr->function) && die_is_func_def(sp_die)) {
1753 		lf->fname = die_get_decl_file(sp_die);
1754 		dwarf_decl_line(sp_die, &lr->offset);
1755 		pr_debug("fname: %s, lineno:%d\n", lf->fname, lr->offset);
1756 		lf->lno_s = lr->offset + lr->start;
1757 		if (lf->lno_s < 0)	/* Overflow */
1758 			lf->lno_s = INT_MAX;
1759 		lf->lno_e = lr->offset + lr->end;
1760 		if (lf->lno_e < 0)	/* Overflow */
1761 			lf->lno_e = INT_MAX;
1762 		pr_debug("New line range: %d to %d\n", lf->lno_s, lf->lno_e);
1763 		lr->start = lf->lno_s;
1764 		lr->end = lf->lno_e;
1765 		if (!die_is_func_instance(sp_die))
1766 			param->retval = die_walk_instances(sp_die,
1767 						line_range_inline_cb, lf);
1768 		else
1769 			param->retval = find_line_range_by_line(sp_die, lf);
1770 		return DWARF_CB_ABORT;
1771 	}
1772 	return DWARF_CB_OK;
1773 }
1774 
find_line_range_by_func(struct line_finder * lf)1775 static int find_line_range_by_func(struct line_finder *lf)
1776 {
1777 	struct dwarf_callback_param param = {.data = (void *)lf, .retval = 0};
1778 	dwarf_getfuncs(&lf->cu_die, line_range_search_cb, &param, 0);
1779 	return param.retval;
1780 }
1781 
debuginfo__find_line_range(struct debuginfo * dbg,struct line_range * lr)1782 int debuginfo__find_line_range(struct debuginfo *dbg, struct line_range *lr)
1783 {
1784 	struct line_finder lf = {.lr = lr, .found = 0};
1785 	int ret = 0;
1786 	Dwarf_Off off = 0, noff;
1787 	size_t cuhl;
1788 	Dwarf_Die *diep;
1789 	const char *comp_dir;
1790 
1791 	/* Fastpath: lookup by function name from .debug_pubnames section */
1792 	if (lr->function) {
1793 		struct pubname_callback_param pubname_param = {
1794 			.function = lr->function, .file = lr->file,
1795 			.cu_die = &lf.cu_die, .sp_die = &lf.sp_die, .found = 0};
1796 		struct dwarf_callback_param line_range_param = {
1797 			.data = (void *)&lf, .retval = 0};
1798 
1799 		dwarf_getpubnames(dbg->dbg, pubname_search_cb,
1800 				  &pubname_param, 0);
1801 		if (pubname_param.found) {
1802 			line_range_search_cb(&lf.sp_die, &line_range_param);
1803 			if (lf.found)
1804 				goto found;
1805 		}
1806 	}
1807 
1808 	/* Loop on CUs (Compilation Unit) */
1809 	while (!lf.found && ret >= 0) {
1810 		if (dwarf_nextcu(dbg->dbg, off, &noff, &cuhl,
1811 				 NULL, NULL, NULL) != 0)
1812 			break;
1813 
1814 		/* Get the DIE(Debugging Information Entry) of this CU */
1815 		diep = dwarf_offdie(dbg->dbg, off + cuhl, &lf.cu_die);
1816 		if (!diep) {
1817 			off = noff;
1818 			continue;
1819 		}
1820 
1821 		/* Check if target file is included. */
1822 		if (lr->file)
1823 			lf.fname = cu_find_realpath(&lf.cu_die, lr->file);
1824 		else
1825 			lf.fname = 0;
1826 
1827 		if (!lr->file || lf.fname) {
1828 			if (lr->function)
1829 				ret = find_line_range_by_func(&lf);
1830 			else {
1831 				lf.lno_s = lr->start;
1832 				lf.lno_e = lr->end;
1833 				ret = find_line_range_by_line(NULL, &lf);
1834 			}
1835 		}
1836 		off = noff;
1837 	}
1838 
1839 found:
1840 	/* Store comp_dir */
1841 	if (lf.found) {
1842 		comp_dir = cu_get_comp_dir(&lf.cu_die);
1843 		if (comp_dir) {
1844 			lr->comp_dir = strdup(comp_dir);
1845 			if (!lr->comp_dir)
1846 				ret = -ENOMEM;
1847 		}
1848 	}
1849 
1850 	pr_debug("path: %s\n", lr->path);
1851 	return (ret < 0) ? ret : lf.found;
1852 }
1853 
1854 /*
1855  * Find a src file from a DWARF tag path. Prepend optional source path prefix
1856  * and chop off leading directories that do not exist. Result is passed back as
1857  * a newly allocated path on success.
1858  * Return 0 if file was found and readable, -errno otherwise.
1859  */
find_source_path(const char * raw_path,const char * sbuild_id,const char * comp_dir,char ** new_path)1860 int find_source_path(const char *raw_path, const char *sbuild_id,
1861 		const char *comp_dir, char **new_path)
1862 {
1863 	const char *prefix = symbol_conf.source_prefix;
1864 
1865 	if (sbuild_id && !prefix) {
1866 		if (!get_source_from_debuginfod(raw_path, sbuild_id, new_path))
1867 			return 0;
1868 	}
1869 
1870 	if (!prefix) {
1871 		if (raw_path[0] != '/' && comp_dir)
1872 			/* If not an absolute path, try to use comp_dir */
1873 			prefix = comp_dir;
1874 		else {
1875 			if (access(raw_path, R_OK) == 0) {
1876 				*new_path = strdup(raw_path);
1877 				return *new_path ? 0 : -ENOMEM;
1878 			} else
1879 				return -errno;
1880 		}
1881 	}
1882 
1883 	*new_path = malloc((strlen(prefix) + strlen(raw_path) + 2));
1884 	if (!*new_path)
1885 		return -ENOMEM;
1886 
1887 	for (;;) {
1888 		sprintf(*new_path, "%s/%s", prefix, raw_path);
1889 
1890 		if (access(*new_path, R_OK) == 0)
1891 			return 0;
1892 
1893 		if (!symbol_conf.source_prefix) {
1894 			/* In case of searching comp_dir, don't retry */
1895 			zfree(new_path);
1896 			return -errno;
1897 		}
1898 
1899 		switch (errno) {
1900 		case ENAMETOOLONG:
1901 		case ENOENT:
1902 		case EROFS:
1903 		case EFAULT:
1904 			raw_path = strchr(++raw_path, '/');
1905 			if (!raw_path) {
1906 				zfree(new_path);
1907 				return -ENOENT;
1908 			}
1909 			continue;
1910 
1911 		default:
1912 			zfree(new_path);
1913 			return -errno;
1914 		}
1915 	}
1916 }
1917