probe-finder.c

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/*
 * probe-finder.c : C expression to kprobe event converter
 *
 * Written by Masami Hiramatsu <[email protected]>
 *
 * 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 (ret == DW_TAG_pointer_type) {
            if (die_get_real_type(&type, &type) == NULL) {
                pr_warning("Failed to get a type"
                       " information.\n");
                return -ENOENT;
            }
            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 (dwarf_tag(sc_die) != DW_TAG_subprogram) {
        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;
    Dwarf_Attribute attr;

    /* Check tag and diename */
    if (dwarf_tag(sp_die) != DW_TAG_subprogram ||
        !die_compare_name(sp_die, pp->function) ||
        dwarf_attr(sp_die, DW_AT_declaration, &attr))
        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 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 (dwarf_tag(sp_die) == DW_TAG_subprogram &&
        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;
}