probe-finder.c

/*
 * probe-finder.c : C expression to kprobe event converter
 *
 * Written by Masami Hiramatsu <mhiramat@redhat.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 */

#include <sys/utsname.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <stdio.h>
#include <unistd.h>
#include <getopt.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include <dwarf-regs.h>

#include <linux/bitops.h>
#include "event.h"
#include "debug.h"
#include "util.h"
#include "symbol.h"
#include "probe-finder.h"

/* Kprobe tracer basic type is up to u64 */
#define MAX_BASIC_TYPE_BITS	64

/* Line number list operations */

/* Add a line to line number list */
static int line_list__add_line(struct list_head *head, int line)
{
	struct line_node *ln;
	struct list_head *p;

	/* Reverse search, because new line will be the last one */
	list_for_each_entry_reverse(ln, head, list) {
		if (ln->line < line) {
			p = &ln->list;
			goto found;
		} else if (ln->line == line)	/* Already exist */
			return 1;
	}
	/* List is empty, or the smallest entry */
	p = head;
found:
	pr_debug("line list: add a line %u\n", line);
	ln = zalloc(sizeof(struct line_node));
	if (ln == NULL)
		return -ENOMEM;
	ln->line = line;
	INIT_LIST_HEAD(&ln->list);
	list_add(&ln->list, p);
	return 0;
}

/* Check if the line in line number list */
static int line_list__has_line(struct list_head *head, int line)
{
	struct line_node *ln;

	/* Reverse search, because new line will be the last one */
	list_for_each_entry(ln, head, list)
		if (ln->line == line)
			return 1;

	return 0;
}

/* Init line number list */
static void line_list__init(struct list_head *head)
{
	INIT_LIST_HEAD(head);
}

/* Free line number list */
static void line_list__free(struct list_head *head)
{
	struct line_node *ln;
	while (!list_empty(head)) {
		ln = list_first_entry(head, struct line_node, list);
		list_del(&ln->list);
		free(ln);
	}
}

/* Dwarf FL wrappers */
static char *debuginfo_path;	/* Currently dummy */

static const Dwfl_Callbacks offline_callbacks = {
	.find_debuginfo = dwfl_standard_find_debuginfo,
	.debuginfo_path = &debuginfo_path,

	.section_address = dwfl_offline_section_address,

	/* We use this table for core files too.  */
	.find_elf = dwfl_build_id_find_elf,
};

/* Get a Dwarf from offline image */
static int debuginfo__init_offline_dwarf(struct debuginfo *self,
					 const char *path)
{
	Dwfl_Module *mod;
	int fd;

	fd = open(path, O_RDONLY);
	if (fd < 0)
		return fd;

	self->dwfl = dwfl_begin(&offline_callbacks);
	if (!self->dwfl)
		goto error;

	mod = dwfl_report_offline(self->dwfl, "", "", fd);
	if (!mod)
		goto error;

	self->dbg = dwfl_module_getdwarf(mod, &self->bias);
	if (!self->dbg)
		goto error;

	return 0;
error:
	if (self->dwfl)
		dwfl_end(self->dwfl);
	else
		close(fd);
	memset(self, 0, sizeof(*self));

	return -ENOENT;
}

#if _ELFUTILS_PREREQ(0, 148)
/* This method is buggy if elfutils is older than 0.148 */
static int __linux_kernel_find_elf(Dwfl_Module *mod,
				   void **userdata,
				   const char *module_name,
				   Dwarf_Addr base,
				   char **file_name, Elf **elfp)
{
	int fd;
	const char *path = kernel_get_module_path(module_name);

	pr_debug2("Use file %s for %s\n", path, module_name);
	if (path) {
		fd = open(path, O_RDONLY);
		if (fd >= 0) {
			*file_name = strdup(path);
			return fd;
		}
	}
	/* If failed, try to call standard method */
	return dwfl_linux_kernel_find_elf(mod, userdata, module_name, base,
					  file_name, elfp);
}

static const Dwfl_Callbacks kernel_callbacks = {
	.find_debuginfo = dwfl_standard_find_debuginfo,
	.debuginfo_path = &debuginfo_path,

	.find_elf = __linux_kernel_find_elf,
	.section_address = dwfl_linux_kernel_module_section_address,
};

/* Get a Dwarf from live kernel image */
static int debuginfo__init_online_kernel_dwarf(struct debuginfo *self,
					       Dwarf_Addr addr)
{
	self->dwfl = dwfl_begin(&kernel_callbacks);
	if (!self->dwfl)
		return -EINVAL;

	/* Load the kernel dwarves: Don't care the result here */
	dwfl_linux_kernel_report_kernel(self->dwfl);
	dwfl_linux_kernel_report_modules(self->dwfl);

	self->dbg = dwfl_addrdwarf(self->dwfl, addr, &self->bias);
	/* Here, check whether we could get a real dwarf */
	if (!self->dbg) {
		pr_debug("Failed to find kernel dwarf at %lx\n",
			 (unsigned long)addr);
		dwfl_end(self->dwfl);
		memset(self, 0, sizeof(*self));
		return -ENOENT;
	}

	return 0;
}
#else
/* With older elfutils, this just support kernel module... */
static int debuginfo__init_online_kernel_dwarf(struct debuginfo *self,
					       Dwarf_Addr addr __maybe_unused)
{
	const char *path = kernel_get_module_path("kernel");

	if (!path) {
		pr_err("Failed to find vmlinux path\n");
		return -ENOENT;
	}

	pr_debug2("Use file %s for debuginfo\n", path);
	return debuginfo__init_offline_dwarf(self, path);
}
#endif

struct debuginfo *debuginfo__new(const char *path)
{
	struct debuginfo *self = zalloc(sizeof(struct debuginfo));
	if (!self)
		return NULL;

	if (debuginfo__init_offline_dwarf(self, path) < 0) {
		free(self);
		self = NULL;
	}

	return self;
}

struct debuginfo *debuginfo__new_online_kernel(unsigned long addr)
{
	struct debuginfo *self = zalloc(sizeof(struct debuginfo));
	if (!self)
		return NULL;

	if (debuginfo__init_online_kernel_dwarf(self, (Dwarf_Addr)addr) < 0) {
		free(self);
		self = NULL;
	}

	return self;
}

void debuginfo__delete(struct debuginfo *self)
{
	if (self) {
		if (self->dwfl)
			dwfl_end(self->dwfl);
		free(self);
	}
}

/*
 * Probe finder related functions
 */

static struct probe_trace_arg_ref *alloc_trace_arg_ref(long offs)
{
	struct probe_trace_arg_ref *ref;
	ref = zalloc(sizeof(struct probe_trace_arg_ref));
	if (ref != NULL)
		ref->offset = offs;
	return ref;
}

/*
 * Convert a location into trace_arg.
 * If tvar == NULL, this just checks variable can be converted.
 */
static int convert_variable_location(Dwarf_Die *vr_die, Dwarf_Addr addr,
				     Dwarf_Op *fb_ops,
				     struct probe_trace_arg *tvar)
{
	Dwarf_Attribute attr;
	Dwarf_Op *op;
	size_t nops;
	unsigned int regn;
	Dwarf_Word offs = 0;
	bool ref = false;
	const char *regs;
	int ret;

	if (dwarf_attr(vr_die, DW_AT_external, &attr) != NULL)
		goto static_var;

	/* TODO: handle more than 1 exprs */
	if (dwarf_attr(vr_die, DW_AT_location, &attr) == NULL ||
	    dwarf_getlocation_addr(&attr, addr, &op, &nops, 1) <= 0 ||
	    nops == 0) {
		/* TODO: Support const_value */
		return -ENOENT;
	}

	if (op->atom == DW_OP_addr) {
static_var:
		if (!tvar)
			return 0;
		/* Static variables on memory (not stack), make @varname */
		ret = strlen(dwarf_diename(vr_die));
		tvar->value = zalloc(ret + 2);
		if (tvar->value == NULL)
			return -ENOMEM;
		snprintf(tvar->value, ret + 2, "@%s", dwarf_diename(vr_die));
		tvar->ref = alloc_trace_arg_ref((long)offs);
		if (tvar->ref == NULL)
			return -ENOMEM;
		return 0;
	}

	/* If this is based on frame buffer, set the offset */
	if (op->atom == DW_OP_fbreg) {
		if (fb_ops == NULL)
			return -ENOTSUP;
		ref = true;
		offs = op->number;
		op = &fb_ops[0];
	}

	if (op->atom >= DW_OP_breg0 && op->atom <= DW_OP_breg31) {
		regn = op->atom - DW_OP_breg0;
		offs += op->number;
		ref = true;
	} else if (op->atom >= DW_OP_reg0 && op->atom <= DW_OP_reg31) {
		regn = op->atom - DW_OP_reg0;
	} else if (op->atom == DW_OP_bregx) {
		regn = op->number;
		offs += op->number2;
		ref = true;
	} else if (op->atom == DW_OP_regx) {
		regn = op->number;
	} else {
		pr_debug("DW_OP %x is not supported.\n", op->atom);
		return -ENOTSUP;
	}

	if (!tvar)
		return 0;

	regs = get_arch_regstr(regn);
	if (!regs) {
		/* This should be a bug in DWARF or this tool */
		pr_warning("Mapping for the register number %u "
			   "missing on this architecture.\n", regn);
		return -ERANGE;
	}

	tvar->value = strdup(regs);
	if (tvar->value == NULL)
		return -ENOMEM;

	if (ref) {
		tvar->ref = alloc_trace_arg_ref((long)offs);
		if (tvar->ref == NULL)
			return -ENOMEM;
	}
	return 0;
}

#define BYTES_TO_BITS(nb)	((nb) * BITS_PER_LONG / sizeof(long))

static int convert_variable_type(Dwarf_Die *vr_die,
				 struct probe_trace_arg *tvar,
				 const char *cast)
{
	struct probe_trace_arg_ref **ref_ptr = &tvar->ref;
	Dwarf_Die type;
	char buf[16];
	int bsize, boffs, total;
	int ret;

	/* TODO: check all types */
	if (cast && strcmp(cast, "string") != 0) {
		/* Non string type is OK */
		tvar->type = strdup(cast);
		return (tvar->type == NULL) ? -ENOMEM : 0;
	}

	bsize = dwarf_bitsize(vr_die);
	if (bsize > 0) {
		/* This is a bitfield */
		boffs = dwarf_bitoffset(vr_die);
		total = dwarf_bytesize(vr_die);
		if (boffs < 0 || total < 0)
			return -ENOENT;
		ret = snprintf(buf, 16, "b%d@%d/%zd", bsize, boffs,
				BYTES_TO_BITS(total));
		goto formatted;
	}

	if (die_get_real_type(vr_die, &type) == NULL) {
		pr_warning("Failed to get a type information of %s.\n",
			   dwarf_diename(vr_die));
		return -ENOENT;
	}

	pr_debug("%s type is %s.\n",
		 dwarf_diename(vr_die), dwarf_diename(&type));

	if (cast && strcmp(cast, "string") == 0) {	/* String type */
		ret = dwarf_tag(&type);
		if (ret != DW_TAG_pointer_type &&
		    ret != DW_TAG_array_type) {
			pr_warning("Failed to cast into string: "
				   "%s(%s) is not a pointer nor array.\n",
				   dwarf_diename(vr_die), dwarf_diename(&type));
			return -EINVAL;
		}
		if (die_get_real_type(&type, &type) == NULL) {
			pr_warning("Failed to get a type"
				   " information.\n");
			return -ENOENT;
		}
		if (ret == DW_TAG_pointer_type) {
			while (*ref_ptr)
				ref_ptr = &(*ref_ptr)->next;
			/* Add new reference with offset +0 */
			*ref_ptr = zalloc(sizeof(struct probe_trace_arg_ref));
			if (*ref_ptr == NULL) {
				pr_warning("Out of memory error\n");
				return -ENOMEM;
			}
		}
		if (!die_compare_name(&type, "char") &&
		    !die_compare_name(&type, "unsigned char")) {
			pr_warning("Failed to cast into string: "
				   "%s is not (unsigned) char *.\n",
				   dwarf_diename(vr_die));
			return -EINVAL;
		}
		tvar->type = strdup(cast);
		return (tvar->type == NULL) ? -ENOMEM : 0;
	}

	ret = dwarf_bytesize(&type);
	if (ret <= 0)
		/* No size ... try to use default type */
		return 0;
	ret = BYTES_TO_BITS(ret);

	/* Check the bitwidth */
	if (ret > MAX_BASIC_TYPE_BITS) {
		pr_info("%s exceeds max-bitwidth. Cut down to %d bits.\n",
			dwarf_diename(&type), MAX_BASIC_TYPE_BITS);
		ret = MAX_BASIC_TYPE_BITS;
	}
	ret = snprintf(buf, 16, "%c%d",
		       die_is_signed_type(&type) ? 's' : 'u', ret);

formatted:
	if (ret < 0 || ret >= 16) {
		if (ret >= 16)
			ret = -E2BIG;
		pr_warning("Failed to convert variable type: %s\n",
			   strerror(-ret));
		return ret;
	}
	tvar->type = strdup(buf);
	if (tvar->type == NULL)
		return -ENOMEM;
	return 0;
}

static int 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)
{
	struct probe_trace_arg_ref *ref = *ref_ptr;
	Dwarf_Die type;
	Dwarf_Word offs;
	int ret, tag;

	pr_debug("converting %s in %s\n", field->name, varname);
	if (die_get_real_type(vr_die, &type) == NULL) {
		pr_warning("Failed to get the type of %s.\n", varname);
		return -ENOENT;
	}
	pr_debug2("Var real type: (%x)\n", (unsigned)dwarf_dieoffset(&type));
	tag = dwarf_tag(&type);

	if (field->name[0] == '[' &&
	    (tag == DW_TAG_array_type || tag == DW_TAG_pointer_type)) {
		if (field->next)
			/* Save original type for next field */
			memcpy(die_mem, &type, sizeof(*die_mem));
		/* Get the type of this array */
		if (die_get_real_type(&type, &type) == NULL) {
			pr_warning("Failed to get the type of %s.\n", varname);
			return -ENOENT;
		}
		pr_debug2("Array real type: (%x)\n",
			 (unsigned)dwarf_dieoffset(&type));
		if (tag == DW_TAG_pointer_type) {
			ref = zalloc(sizeof(struct probe_trace_arg_ref));
			if (ref == NULL)
				return -ENOMEM;
			if (*ref_ptr)
				(*ref_ptr)->next = ref;
			else
				*ref_ptr = ref;
		}
		ref->offset += dwarf_bytesize(&type) * field->index;
		if (!field->next)
			/* Save vr_die for converting types */
			memcpy(die_mem, vr_die, sizeof(*die_mem));
		goto next;
	} else if (tag == DW_TAG_pointer_type) {
		/* Check the pointer and dereference */
		if (!field->ref) {
			pr_err("Semantic error: %s must be referred by '->'\n",
			       field->name);
			return -EINVAL;
		}
		/* Get the type pointed by this pointer */
		if (die_get_real_type(&type, &type) == NULL) {
			pr_warning("Failed to get the type of %s.\n", varname);
			return -ENOENT;
		}
		/* Verify it is a data structure  */
		tag = dwarf_tag(&type);
		if (tag != DW_TAG_structure_type && tag != DW_TAG_union_type) {
			pr_warning("%s is not a data structure nor an union.\n",
				   varname);
			return -EINVAL;
		}

		ref = zalloc(sizeof(struct probe_trace_arg_ref));
		if (ref == NULL)
			return -ENOMEM;
		if (*ref_ptr)
			(*ref_ptr)->next = ref;
		else
			*ref_ptr = ref;
	} else {
		/* Verify it is a data structure  */
		if (tag != DW_TAG_structure_type && tag != DW_TAG_union_type) {
			pr_warning("%s is not a data structure nor an union.\n",
				   varname);
			return -EINVAL;
		}
		if (field->name[0] == '[') {
			pr_err("Semantic error: %s is not a pointor"
			       " nor array.\n", varname);
			return -EINVAL;
		}
		if (field->ref) {
			pr_err("Semantic error: %s must be referred by '.'\n",
			       field->name);
			return -EINVAL;
		}
		if (!ref) {
			pr_warning("Structure on a register is not "
				   "supported yet.\n");
			return -ENOTSUP;
		}
	}

	if (die_find_member(&type, field->name, die_mem) == NULL) {
		pr_warning("%s(tyep:%s) has no member %s.\n", varname,
			   dwarf_diename(&type), field->name);
		return -EINVAL;
	}

	/* Get the offset of the field */
	if (tag == DW_TAG_union_type) {
		offs = 0;
	} else {
		ret = die_get_data_member_location(die_mem, &offs);
		if (ret < 0) {
			pr_warning("Failed to get the offset of %s.\n",
				   field->name);
			return ret;
		}
	}
	ref->offset += (long)offs;

next:
	/* Converting next field */
	if (field->next)
		return convert_variable_fields(die_mem, field->name,
					field->next, &ref, die_mem);
	else
		return 0;
}

/* Show a variables in kprobe event format */
static int convert_variable(Dwarf_Die *vr_die, struct probe_finder *pf)
{
	Dwarf_Die die_mem;
	int ret;

	pr_debug("Converting variable %s into trace event.\n",
		 dwarf_diename(vr_die));

	ret = convert_variable_location(vr_die, pf->addr, pf->fb_ops,
					pf->tvar);
	if (ret == -ENOENT)
		pr_err("Failed to find the location of %s at this address.\n"
		       " Perhaps, it has been optimized out.\n", pf->pvar->var);
	else if (ret == -ENOTSUP)
		pr_err("Sorry, we don't support this variable location yet.\n");
	else if (pf->pvar->field) {
		ret = convert_variable_fields(vr_die, pf->pvar->var,
					      pf->pvar->field, &pf->tvar->ref,
					      &die_mem);
		vr_die = &die_mem;
	}
	if (ret == 0)
		ret = convert_variable_type(vr_die, pf->tvar, pf->pvar->type);
	/* *expr will be cached in libdw. Don't free it. */
	return ret;
}

/* Find a variable in a scope DIE */
static int find_variable(Dwarf_Die *sc_die, struct probe_finder *pf)
{
	Dwarf_Die vr_die;
	char buf[32], *ptr;
	int ret = 0;

	if (!is_c_varname(pf->pvar->var)) {
		/* Copy raw parameters */
		pf->tvar->value = strdup(pf->pvar->var);
		if (pf->tvar->value == NULL)
			return -ENOMEM;
		if (pf->pvar->type) {
			pf->tvar->type = strdup(pf->pvar->type);
			if (pf->tvar->type == NULL)
				return -ENOMEM;
		}
		if (pf->pvar->name) {
			pf->tvar->name = strdup(pf->pvar->name);
			if (pf->tvar->name == NULL)
				return -ENOMEM;
		} else
			pf->tvar->name = NULL;
		return 0;
	}

	if (pf->pvar->name)
		pf->tvar->name = strdup(pf->pvar->name);
	else {
		ret = synthesize_perf_probe_arg(pf->pvar, buf, 32);
		if (ret < 0)
			return ret;
		ptr = strchr(buf, ':');	/* Change type separator to _ */
		if (ptr)
			*ptr = '_';
		pf->tvar->name = strdup(buf);
	}
	if (pf->tvar->name == NULL)
		return -ENOMEM;

	pr_debug("Searching '%s' variable in context.\n", pf->pvar->var);
	/* Search child die for local variables and parameters. */
	if (!die_find_variable_at(sc_die, pf->pvar->var, pf->addr, &vr_die)) {
		/* Search again in global variables */
		if (!die_find_variable_at(&pf->cu_die, pf->pvar->var, 0, &vr_die))
			ret = -ENOENT;
	}
	if (ret >= 0)
		ret = convert_variable(&vr_die, pf);

	if (ret < 0)
		pr_warning("Failed to find '%s' in this function.\n",
			   pf->pvar->var);
	return ret;
}

/* Convert subprogram DIE to trace point */
static int convert_to_trace_point(Dwarf_Die *sp_die, Dwarf_Addr paddr,
				  bool retprobe, struct probe_trace_point *tp)
{
	Dwarf_Addr eaddr, highaddr;
	const char *name;

	/* Copy the name of probe point */
	name = dwarf_diename(sp_die);
	if (name) {
		if (dwarf_entrypc(sp_die, &eaddr) != 0) {
			pr_warning("Failed to get entry address of %s\n",
				   dwarf_diename(sp_die));
			return -ENOENT;
		}
		if (dwarf_highpc(sp_die, &highaddr) != 0) {
			pr_warning("Failed to get end address of %s\n",
				   dwarf_diename(sp_die));
			return -ENOENT;
		}
		if (paddr > highaddr) {
			pr_warning("Offset specified is greater than size of %s\n",
				   dwarf_diename(sp_die));
			return -EINVAL;
		}
		tp->symbol = strdup(name);
		if (tp->symbol == NULL)
			return -ENOMEM;
		tp->offset = (unsigned long)(paddr - eaddr);
	} else
		/* This function has no name. */
		tp->offset = (unsigned long)paddr;

	/* Return probe must be on the head of a subprogram */
	if (retprobe) {
		if (eaddr != paddr) {
			pr_warning("Return probe must be on the head of"
				   " a real function.\n");
			return -EINVAL;
		}
		tp->retprobe = true;
	}

	return 0;
}

/* Call probe_finder callback with scope DIE */
static int call_probe_finder(Dwarf_Die *sc_die, struct probe_finder *pf)
{
	Dwarf_Attribute fb_attr;
	size_t nops;
	int ret;

	if (!sc_die) {
		pr_err("Caller must pass a scope DIE. Program error.\n");
		return -EINVAL;
	}

	/* If not a real subprogram, find a real one */
	if (!die_is_func_def(sc_die)) {
		if (!die_find_realfunc(&pf->cu_die, pf->addr, &pf->sp_die)) {
			pr_warning("Failed to find probe point in any "
				   "functions.\n");
			return -ENOENT;
		}
	} else
		memcpy(&pf->sp_die, sc_die, sizeof(Dwarf_Die));

	/* Get the frame base attribute/ops from subprogram */
	dwarf_attr(&pf->sp_die, DW_AT_frame_base, &fb_attr);
	ret = dwarf_getlocation_addr(&fb_attr, pf->addr, &pf->fb_ops, &nops, 1);
	if (ret <= 0 || nops == 0) {
		pf->fb_ops = NULL;
#if _ELFUTILS_PREREQ(0, 142)
	} else if (nops == 1 && pf->fb_ops[0].atom == DW_OP_call_frame_cfa &&
		   pf->cfi != NULL) {
		Dwarf_Frame *frame;
		if (dwarf_cfi_addrframe(pf->cfi, pf->addr, &frame) != 0 ||
		    dwarf_frame_cfa(frame, &pf->fb_ops, &nops) != 0) {
			pr_warning("Failed to get call frame on 0x%jx\n",
				   (uintmax_t)pf->addr);
			return -ENOENT;
		}
#endif
	}

	/* Call finder's callback handler */
	ret = pf->callback(sc_die, pf);

	/* *pf->fb_ops will be cached in libdw. Don't free it. */
	pf->fb_ops = NULL;

	return ret;
}

struct find_scope_param {
	const char *function;
	const char *file;
	int line;
	int diff;
	Dwarf_Die *die_mem;
	bool found;
};

static int find_best_scope_cb(Dwarf_Die *fn_die, void *data)
{
	struct find_scope_param *fsp = data;
	const char *file;
	int lno;

	/* Skip if declared file name does not match */
	if (fsp->file) {
		file = dwarf_decl_file(fn_die);
		if (!file || strcmp(fsp->file, file) != 0)
			return 0;
	}
	/* If the function name is given, that's what user expects */
	if (fsp->function) {
		if (die_compare_name(fn_die, fsp->function)) {
			memcpy(fsp->die_mem, fn_die, sizeof(Dwarf_Die));
			fsp->found = true;
			return 1;
		}
	} else {
		/* With the line number, find the nearest declared DIE */
		dwarf_decl_line(fn_die, &lno);
		if (lno < fsp->line && fsp->diff > fsp->line - lno) {
			/* Keep a candidate and continue */
			fsp->diff = fsp->line - lno;
			memcpy(fsp->die_mem, fn_die, sizeof(Dwarf_Die));
			fsp->found = true;
		}
	}
	return 0;
}

/* Find an appropriate scope fits to given conditions */
static Dwarf_Die *find_best_scope(struct probe_finder *pf, Dwarf_Die *die_mem)
{
	struct find_scope_param fsp = {
		.function = pf->pev->point.function,
		.file = pf->fname,
		.line = pf->lno,
		.diff = INT_MAX,
		.die_mem = die_mem,
		.found = false,
	};

	cu_walk_functions_at(&pf->cu_die, pf->addr, find_best_scope_cb, &fsp);

	return fsp.found ? die_mem : NULL;
}

static int probe_point_line_walker(const char *fname, int lineno,
				   Dwarf_Addr addr, void *data)
{
	struct probe_finder *pf = data;
	Dwarf_Die *sc_die, die_mem;
	int ret;

	if (lineno != pf->lno || strtailcmp(fname, pf->fname) != 0)
		return 0;

	pf->addr = addr;
	sc_die = find_best_scope(pf, &die_mem);
	if (!sc_die) {
		pr_warning("Failed to find scope of probe point.\n");
		return -ENOENT;
	}

	ret = call_probe_finder(sc_die, pf);

	/* Continue if no error, because the line will be in inline function */
	return ret < 0 ? ret : 0;
}

/* Find probe point from its line number */
static int find_probe_point_by_line(struct probe_finder *pf)
{
	return die_walk_lines(&pf->cu_die, probe_point_line_walker, pf);
}

/* Find lines which match lazy pattern */
static int find_lazy_match_lines(struct list_head *head,
				 const char *fname, const char *pat)
{
	FILE *fp;
	char *line = NULL;
	size_t line_len;
	ssize_t len;
	int count = 0, linenum = 1;

	fp = fopen(fname, "r");
	if (!fp) {
		pr_warning("Failed to open %s: %s\n", fname, strerror(errno));
		return -errno;
	}

	while ((len = getline(&line, &line_len, fp)) > 0) {

		if (line[len - 1] == '\n')
			line[len - 1] = '\0';

		if (strlazymatch(line, pat)) {
			line_list__add_line(head, linenum);
			count++;
		}
		linenum++;
	}

	if (ferror(fp))
		count = -errno;
	free(line);
	fclose(fp);

	if (count == 0)
		pr_debug("No matched lines found in %s.\n", fname);
	return count;
}

static int probe_point_lazy_walker(const char *fname, int lineno,
				   Dwarf_Addr addr, void *data)
{
	struct probe_finder *pf = data;
	Dwarf_Die *sc_die, die_mem;
	int ret;

	if (!line_list__has_line(&pf->lcache, lineno) ||
	    strtailcmp(fname, pf->fname) != 0)
		return 0;

	pr_debug("Probe line found: line:%d addr:0x%llx\n",
		 lineno, (unsigned long long)addr);
	pf->addr = addr;
	pf->lno = lineno;
	sc_die = find_best_scope(pf, &die_mem);
	if (!sc_die) {
		pr_warning("Failed to find scope of probe point.\n");
		return -ENOENT;
	}

	ret = call_probe_finder(sc_die, pf);

	/*
	 * Continue if no error, because the lazy pattern will match
	 * to other lines
	 */
	return ret < 0 ? ret : 0;
}

/* Find probe points from lazy pattern  */
static int find_probe_point_lazy(Dwarf_Die *sp_die, struct probe_finder *pf)
{
	int ret = 0;

	if (list_empty(&pf->lcache)) {
		/* Matching lazy line pattern */
		ret = find_lazy_match_lines(&pf->lcache, pf->fname,
					    pf->pev->point.lazy_line);
		if (ret <= 0)
			return ret;
	}

	return die_walk_lines(sp_die, probe_point_lazy_walker, pf);
}

static int probe_point_inline_cb(Dwarf_Die *in_die, void *data)
{
	struct probe_finder *pf = data;
	struct perf_probe_point *pp = &pf->pev->point;
	Dwarf_Addr addr;
	int ret;

	if (pp->lazy_line)
		ret = find_probe_point_lazy(in_die, pf);
	else {
		/* Get probe address */
		if (dwarf_entrypc(in_die, &addr) != 0) {
			pr_warning("Failed to get entry address of %s.\n",
				   dwarf_diename(in_die));
			return -ENOENT;
		}
		pf->addr = addr;
		pf->addr += pp->offset;
		pr_debug("found inline addr: 0x%jx\n",
			 (uintmax_t)pf->addr);

		ret = call_probe_finder(in_die, pf);
	}

	return ret;
}

/* Callback parameter with return value for libdw */
struct dwarf_callback_param {
	void *data;
	int retval;
};

/* Search function from function name */
static int probe_point_search_cb(Dwarf_Die *sp_die, void *data)
{
	struct dwarf_callback_param *param = data;
	struct probe_finder *pf = param->data;
	struct perf_probe_point *pp = &pf->pev->point;

	/* Check tag and diename */
	if (!die_is_func_def(sp_die) ||
	    !die_compare_name(sp_die, pp->function))
		return DWARF_CB_OK;

	/* Check declared file */
	if (pp->file && strtailcmp(pp->file, dwarf_decl_file(sp_die)))
		return DWARF_CB_OK;

	pf->fname = dwarf_decl_file(sp_die);
	if (pp->line) { /* Function relative line */
		dwarf_decl_line(sp_die, &pf->lno);
		pf->lno += pp->line;
		param->retval = find_probe_point_by_line(pf);
	} else if (!dwarf_func_inline(sp_die)) {
		/* Real function */
		if (pp->lazy_line)
			param->retval = find_probe_point_lazy(sp_die, pf);
		else {
			if (dwarf_entrypc(sp_die, &pf->addr) != 0) {
				pr_warning("Failed to get entry address of "
					   "%s.\n", dwarf_diename(sp_die));
				param->retval = -ENOENT;
				return DWARF_CB_ABORT;
			}
			pf->addr += pp->offset;
			/* TODO: Check the address in this function */
			param->retval = call_probe_finder(sp_die, pf);
		}
	} else
		/* Inlined function: search instances */
		param->retval = die_walk_instances(sp_die,
					probe_point_inline_cb, (void *)pf);

	return DWARF_CB_ABORT; /* Exit; no same symbol in this CU. */
}

static int find_probe_point_by_func(struct probe_finder *pf)
{
	struct dwarf_callback_param _param = {.data = (void *)pf,
					      .retval = 0};
	dwarf_getfuncs(&pf->cu_die, probe_point_search_cb, &_param, 0);
	return _param.retval;
}

struct pubname_callback_param {
	char *function;
	char *file;
	Dwarf_Die *cu_die;
	Dwarf_Die *sp_die;
	int found;
};

static int pubname_search_cb(Dwarf *dbg, Dwarf_Global *gl, void *data)
{
	struct pubname_callback_param *param = data;

	if (dwarf_offdie(dbg, gl->die_offset, param->sp_die)) {
		if (dwarf_tag(param->sp_die) != DW_TAG_subprogram)
			return DWARF_CB_OK;

		if (die_compare_name(param->sp_die, param->function)) {
			if (!dwarf_offdie(dbg, gl->cu_offset, param->cu_die))
				return DWARF_CB_OK;

			if (param->file &&
			    strtailcmp(param->file, dwarf_decl_file(param->sp_die)))
				return DWARF_CB_OK;

			param->found = 1;
			return DWARF_CB_ABORT;
		}
	}

	return DWARF_CB_OK;
}

/* Find probe points from debuginfo */
static int debuginfo__find_probes(struct debuginfo *self,
				  struct probe_finder *pf)
{
	struct perf_probe_point *pp = &pf->pev->point;
	Dwarf_Off off, noff;
	size_t cuhl;
	Dwarf_Die *diep;
	int ret = 0;

#if _ELFUTILS_PREREQ(0, 142)
	/* Get the call frame information from this dwarf */
	pf->cfi = dwarf_getcfi(self->dbg);
#endif

	off = 0;
	line_list__init(&pf->lcache);

	/* Fastpath: lookup by function name from .debug_pubnames section */
	if (pp->function) {
		struct pubname_callback_param pubname_param = {
			.function = pp->function,
			.file	  = pp->file,
			.cu_die	  = &pf->cu_die,
			.sp_die	  = &pf->sp_die,
			.found	  = 0,
		};
		struct dwarf_callback_param probe_param = {
			.data = pf,
		};

		dwarf_getpubnames(self->dbg, pubname_search_cb,
				  &pubname_param, 0);
		if (pubname_param.found) {
			ret = probe_point_search_cb(&pf->sp_die, &probe_param);
			if (ret)
				goto found;
		}
	}

	/* Loop on CUs (Compilation Unit) */
	while (!dwarf_nextcu(self->dbg, off, &noff, &cuhl, NULL, NULL, NULL)) {
		/* Get the DIE(Debugging Information Entry) of this CU */
		diep = dwarf_offdie(self->dbg, off + cuhl, &pf->cu_die);
		if (!diep)
			continue;

		/* Check if target file is included. */
		if (pp->file)
			pf->fname = cu_find_realpath(&pf->cu_die, pp->file);
		else
			pf->fname = NULL;

		if (!pp->file || pf->fname) {
			if (pp->function)
				ret = find_probe_point_by_func(pf);
			else if (pp->lazy_line)
				ret = find_probe_point_lazy(NULL, pf);
			else {
				pf->lno = pp->line;
				ret = find_probe_point_by_line(pf);
			}
			if (ret < 0)
				break;
		}
		off = noff;
	}

found:
	line_list__free(&pf->lcache);

	return ret;
}

/* Add a found probe point into trace event list */
static int add_probe_trace_event(Dwarf_Die *sc_die, struct probe_finder *pf)
{
	struct trace_event_finder *tf =
			container_of(pf, struct trace_event_finder, pf);
	struct probe_trace_event *tev;
	int ret, i;

	/* Check number of tevs */
	if (tf->ntevs == tf->max_tevs) {
		pr_warning("Too many( > %d) probe point found.\n",
			   tf->max_tevs);
		return -ERANGE;
	}
	tev = &tf->tevs[tf->ntevs++];

	/* Trace point should be converted from subprogram DIE */
	ret = convert_to_trace_point(&pf->sp_die, pf->addr,
				     pf->pev->point.retprobe, &tev->point);
	if (ret < 0)
		return ret;

	pr_debug("Probe point found: %s+%lu\n", tev->point.symbol,
		 tev->point.offset);

	/* Find each argument */
	tev->nargs = pf->pev->nargs;
	tev->args = zalloc(sizeof(struct probe_trace_arg) * tev->nargs);
	if (tev->args == NULL)
		return -ENOMEM;
	for (i = 0; i < pf->pev->nargs; i++) {
		pf->pvar = &pf->pev->args[i];
		pf->tvar = &tev->args[i];
		/* Variable should be found from scope DIE */
		ret = find_variable(sc_die, pf);
		if (ret != 0)
			return ret;
	}

	return 0;
}

/* Find probe_trace_events specified by perf_probe_event from debuginfo */
int debuginfo__find_trace_events(struct debuginfo *self,
				 struct perf_probe_event *pev,
				 struct probe_trace_event **tevs, int max_tevs)
{
	struct trace_event_finder tf = {
			.pf = {.pev = pev, .callback = add_probe_trace_event},
			.max_tevs = max_tevs};
	int ret;

	/* Allocate result tevs array */
	*tevs = zalloc(sizeof(struct probe_trace_event) * max_tevs);
	if (*tevs == NULL)
		return -ENOMEM;

	tf.tevs = *tevs;
	tf.ntevs = 0;

	ret = debuginfo__find_probes(self, &tf.pf);
	if (ret < 0) {
		free(*tevs);
		*tevs = NULL;
		return ret;
	}

	return (ret < 0) ? ret : tf.ntevs;
}

#define MAX_VAR_LEN 64

/* Collect available variables in this scope */
static int collect_variables_cb(Dwarf_Die *die_mem, void *data)
{
	struct available_var_finder *af = data;
	struct variable_list *vl;
	char buf[MAX_VAR_LEN];
	int tag, ret;

	vl = &af->vls[af->nvls - 1];

	tag = dwarf_tag(die_mem);
	if (tag == DW_TAG_formal_parameter ||
	    tag == DW_TAG_variable) {
		ret = convert_variable_location(die_mem, af->pf.addr,
						af->pf.fb_ops, NULL);
		if (ret == 0) {
			ret = die_get_varname(die_mem, buf, MAX_VAR_LEN);
			pr_debug2("Add new var: %s\n", buf);
			if (ret > 0)
				strlist__add(vl->vars, buf);
		}
	}

	if (af->child && dwarf_haspc(die_mem, af->pf.addr))
		return DIE_FIND_CB_CONTINUE;
	else
		return DIE_FIND_CB_SIBLING;
}

/* Add a found vars into available variables list */
static int add_available_vars(Dwarf_Die *sc_die, struct probe_finder *pf)
{
	struct available_var_finder *af =
			container_of(pf, struct available_var_finder, pf);
	struct variable_list *vl;
	Dwarf_Die die_mem;
	int ret;

	/* Check number of tevs */
	if (af->nvls == af->max_vls) {
		pr_warning("Too many( > %d) probe point found.\n", af->max_vls);
		return -ERANGE;
	}
	vl = &af->vls[af->nvls++];

	/* Trace point should be converted from subprogram DIE */
	ret = convert_to_trace_point(&pf->sp_die, pf->addr,
				     pf->pev->point.retprobe, &vl->point);
	if (ret < 0)
		return ret;

	pr_debug("Probe point found: %s+%lu\n", vl->point.symbol,
		 vl->point.offset);

	/* Find local variables */
	vl->vars = strlist__new(true, NULL);
	if (vl->vars == NULL)
		return -ENOMEM;
	af->child = true;
	die_find_child(sc_die, collect_variables_cb, (void *)af, &die_mem);

	/* Find external variables */
	if (!af->externs)
		goto out;
	/* Don't need to search child DIE for externs. */
	af->child = false;
	die_find_child(&pf->cu_die, collect_variables_cb, (void *)af, &die_mem);

out:
	if (strlist__empty(vl->vars)) {
		strlist__delete(vl->vars);
		vl->vars = NULL;
	}

	return ret;
}

/* Find available variables at given probe point */
int debuginfo__find_available_vars_at(struct debuginfo *self,
				      struct perf_probe_event *pev,
				      struct variable_list **vls,
				      int max_vls, bool externs)
{
	struct available_var_finder af = {
			.pf = {.pev = pev, .callback = add_available_vars},
			.max_vls = max_vls, .externs = externs};
	int ret;

	/* Allocate result vls array */
	*vls = zalloc(sizeof(struct variable_list) * max_vls);
	if (*vls == NULL)
		return -ENOMEM;

	af.vls = *vls;
	af.nvls = 0;

	ret = debuginfo__find_probes(self, &af.pf);
	if (ret < 0) {
		/* Free vlist for error */
		while (af.nvls--) {
			if (af.vls[af.nvls].point.symbol)
				free(af.vls[af.nvls].point.symbol);
			if (af.vls[af.nvls].vars)
				strlist__delete(af.vls[af.nvls].vars);
		}
		free(af.vls);
		*vls = NULL;
		return ret;
	}

	return (ret < 0) ? ret : af.nvls;
}

/* Reverse search */
int debuginfo__find_probe_point(struct debuginfo *self, unsigned long addr,
				struct perf_probe_point *ppt)
{
	Dwarf_Die cudie, spdie, indie;
	Dwarf_Addr _addr, baseaddr;
	const char *fname = NULL, *func = NULL, *tmp;
	int baseline = 0, lineno = 0, ret = 0;

	/* Adjust address with bias */
	addr += self->bias;

	/* Find cu die */
	if (!dwarf_addrdie(self->dbg, (Dwarf_Addr)addr - self->bias, &cudie)) {
		pr_warning("Failed to find debug information for address %lx\n",
			   addr);
		ret = -EINVAL;
		goto end;
	}

	/* Find a corresponding line (filename and lineno) */
	cu_find_lineinfo(&cudie, addr, &fname, &lineno);
	/* Don't care whether it failed or not */

	/* Find a corresponding function (name, baseline and baseaddr) */
	if (die_find_realfunc(&cudie, (Dwarf_Addr)addr, &spdie)) {
		/* Get function entry information */
		tmp = dwarf_diename(&spdie);
		if (!tmp ||
		    dwarf_entrypc(&spdie, &baseaddr) != 0 ||
		    dwarf_decl_line(&spdie, &baseline) != 0)
			goto post;
		func = tmp;

		if (addr == (unsigned long)baseaddr)
			/* Function entry - Relative line number is 0 */
			lineno = baseline;
		else if (die_find_inlinefunc(&spdie, (Dwarf_Addr)addr,
					     &indie)) {
			if (dwarf_entrypc(&indie, &_addr) == 0 &&
			    _addr == addr)
				/*
				 * addr is at an inline function entry.
				 * In this case, lineno should be the call-site
				 * line number.
				 */
				lineno = die_get_call_lineno(&indie);
			else {
				/*
				 * addr is in an inline function body.
				 * Since lineno points one of the lines
				 * of the inline function, baseline should
				 * be the entry line of the inline function.
				 */
				tmp = dwarf_diename(&indie);
				if (tmp &&
				    dwarf_decl_line(&spdie, &baseline) == 0)
					func = tmp;
			}
		}
	}

post:
	/* Make a relative line number or an offset */
	if (lineno)
		ppt->line = lineno - baseline;
	else if (func)
		ppt->offset = addr - (unsigned long)baseaddr;

	/* Duplicate strings */
	if (func) {
		ppt->function = strdup(func);
		if (ppt->function == NULL) {
			ret = -ENOMEM;
			goto end;
		}
	}
	if (fname) {
		ppt->file = strdup(fname);
		if (ppt->file == NULL) {
			if (ppt->function) {
				free(ppt->function);
				ppt->function = NULL;
			}
			ret = -ENOMEM;
			goto end;
		}
	}
end:
	if (ret == 0 && (fname || func))
		ret = 1;	/* Found a point */
	return ret;
}

/* Add a line and store the src path */
static int line_range_add_line(const char *src, unsigned int lineno,
			       struct line_range *lr)
{
	/* Copy source path */
	if (!lr->path) {
		lr->path = strdup(src);
		if (lr->path == NULL)
			return -ENOMEM;
	}
	return line_list__add_line(&lr->line_list, lineno);
}

static int line_range_walk_cb(const char *fname, int lineno,
			      Dwarf_Addr addr __maybe_unused,
			      void *data)
{
	struct line_finder *lf = data;

	if ((strtailcmp(fname, lf->fname) != 0) ||
	    (lf->lno_s > lineno || lf->lno_e < lineno))
		return 0;

	if (line_range_add_line(fname, lineno, lf->lr) < 0)
		return -EINVAL;

	return 0;
}

/* Find line range from its line number */
static int find_line_range_by_line(Dwarf_Die *sp_die, struct line_finder *lf)
{
	int ret;

	ret = die_walk_lines(sp_die ?: &lf->cu_die, line_range_walk_cb, lf);

	/* Update status */
	if (ret >= 0)
		if (!list_empty(&lf->lr->line_list))
			ret = lf->found = 1;
		else
			ret = 0;	/* Lines are not found */
	else {
		free(lf->lr->path);
		lf->lr->path = NULL;
	}
	return ret;
}

static int line_range_inline_cb(Dwarf_Die *in_die, void *data)
{
	find_line_range_by_line(in_die, data);

	/*
	 * We have to check all instances of inlined function, because
	 * some execution paths can be optimized out depends on the
	 * function argument of instances
	 */
	return 0;
}

/* Search function definition from function name */
static int line_range_search_cb(Dwarf_Die *sp_die, void *data)
{
	struct dwarf_callback_param *param = data;
	struct line_finder *lf = param->data;
	struct line_range *lr = lf->lr;

	/* Check declared file */
	if (lr->file && strtailcmp(lr->file, dwarf_decl_file(sp_die)))
		return DWARF_CB_OK;

	if (die_is_func_def(sp_die) &&
	    die_compare_name(sp_die, lr->function)) {
		lf->fname = dwarf_decl_file(sp_die);
		dwarf_decl_line(sp_die, &lr->offset);
		pr_debug("fname: %s, lineno:%d\n", lf->fname, lr->offset);
		lf->lno_s = lr->offset + lr->start;
		if (lf->lno_s < 0)	/* Overflow */
			lf->lno_s = INT_MAX;
		lf->lno_e = lr->offset + lr->end;
		if (lf->lno_e < 0)	/* Overflow */
			lf->lno_e = INT_MAX;
		pr_debug("New line range: %d to %d\n", lf->lno_s, lf->lno_e);
		lr->start = lf->lno_s;
		lr->end = lf->lno_e;
		if (dwarf_func_inline(sp_die))
			param->retval = die_walk_instances(sp_die,
						line_range_inline_cb, lf);
		else
			param->retval = find_line_range_by_line(sp_die, lf);
		return DWARF_CB_ABORT;
	}
	return DWARF_CB_OK;
}

static int find_line_range_by_func(struct line_finder *lf)
{
	struct dwarf_callback_param param = {.data = (void *)lf, .retval = 0};
	dwarf_getfuncs(&lf->cu_die, line_range_search_cb, &param, 0);
	return param.retval;
}

int debuginfo__find_line_range(struct debuginfo *self, struct line_range *lr)
{
	struct line_finder lf = {.lr = lr, .found = 0};
	int ret = 0;
	Dwarf_Off off = 0, noff;
	size_t cuhl;
	Dwarf_Die *diep;
	const char *comp_dir;

	/* Fastpath: lookup by function name from .debug_pubnames section */
	if (lr->function) {
		struct pubname_callback_param pubname_param = {
			.function = lr->function, .file = lr->file,
			.cu_die = &lf.cu_die, .sp_die = &lf.sp_die, .found = 0};
		struct dwarf_callback_param line_range_param = {
			.data = (void *)&lf, .retval = 0};

		dwarf_getpubnames(self->dbg, pubname_search_cb,
				  &pubname_param, 0);
		if (pubname_param.found) {
			line_range_search_cb(&lf.sp_die, &line_range_param);
			if (lf.found)
				goto found;
		}
	}

	/* Loop on CUs (Compilation Unit) */
	while (!lf.found && ret >= 0) {
		if (dwarf_nextcu(self->dbg, off, &noff, &cuhl,
				 NULL, NULL, NULL) != 0)
			break;

		/* Get the DIE(Debugging Information Entry) of this CU */
		diep = dwarf_offdie(self->dbg, off + cuhl, &lf.cu_die);
		if (!diep)
			continue;

		/* Check if target file is included. */
		if (lr->file)
			lf.fname = cu_find_realpath(&lf.cu_die, lr->file);
		else
			lf.fname = 0;

		if (!lr->file || lf.fname) {
			if (lr->function)
				ret = find_line_range_by_func(&lf);
			else {
				lf.lno_s = lr->start;
				lf.lno_e = lr->end;
				ret = find_line_range_by_line(NULL, &lf);
			}
		}
		off = noff;
	}

found:
	/* Store comp_dir */
	if (lf.found) {
		comp_dir = cu_get_comp_dir(&lf.cu_die);
		if (comp_dir) {
			lr->comp_dir = strdup(comp_dir);
			if (!lr->comp_dir)
				ret = -ENOMEM;
		}
	}

	pr_debug("path: %s\n", lr->path);
	return (ret < 0) ? ret : lf.found;
}