Linux 4.1.18

[linux/fpc-iii.git] / tools / perf / util / dwarf-aux.c

/*
 * dwarf-aux.c : libdw auxiliary interfaces
 *
 * 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 <stdbool.h>
#include "util.h"
#include "debug.h"
#include "dwarf-aux.h"

/**
 * cu_find_realpath - Find the realpath of the target file
 * @cu_die: A DIE(dwarf information entry) of CU(compilation Unit)
 * @fname:  The tail filename of the target file
 *
 * Find the real(long) path of @fname in @cu_die.
 */
const char *cu_find_realpath(Dwarf_Die *cu_die, const char *fname)
{
        Dwarf_Files *files;
        size_t nfiles, i;
        const char *src = NULL;
        int ret;

        if (!fname)
                return NULL;

        ret = dwarf_getsrcfiles(cu_die, &files, &nfiles);
        if (ret != 0)
                return NULL;

        for (i = 0; i < nfiles; i++) {
                src = dwarf_filesrc(files, i, NULL, NULL);
                if (strtailcmp(src, fname) == 0)
                        break;
        }
        if (i == nfiles)
                return NULL;
        return src;
}

/**
 * cu_get_comp_dir - Get the path of compilation directory
 * @cu_die: a CU DIE
 *
 * Get the path of compilation directory of given @cu_die.
 * Since this depends on DW_AT_comp_dir, older gcc will not
 * embedded it. In that case, this returns NULL.
 */
const char *cu_get_comp_dir(Dwarf_Die *cu_die)
{
        Dwarf_Attribute attr;
        if (dwarf_attr(cu_die, DW_AT_comp_dir, &attr) == NULL)
                return NULL;
        return dwarf_formstring(&attr);
}

/**
 * cu_find_lineinfo - Get a line number and file name for given address
 * @cu_die: a CU DIE
 * @addr: An address
 * @fname: a pointer which returns the file name string
 * @lineno: a pointer which returns the line number
 *
 * Find a line number and file name for @addr in @cu_die.
 */
int cu_find_lineinfo(Dwarf_Die *cu_die, unsigned long addr,
                    const char **fname, int *lineno)
{
        Dwarf_Line *line;
        Dwarf_Addr laddr;

        line = dwarf_getsrc_die(cu_die, (Dwarf_Addr)addr);
        if (line && dwarf_lineaddr(line, &laddr) == 0 &&
            addr == (unsigned long)laddr && dwarf_lineno(line, lineno) == 0) {
                *fname = dwarf_linesrc(line, NULL, NULL);
                if (!*fname)
                        /* line number is useless without filename */
                        *lineno = 0;
        }

        return *lineno ?: -ENOENT;
}

static int __die_find_inline_cb(Dwarf_Die *die_mem, void *data);

/**
 * cu_walk_functions_at - Walk on function DIEs at given address
 * @cu_die: A CU DIE
 * @addr: An address
 * @callback: A callback which called with found DIEs
 * @data: A user data
 *
 * Walk on function DIEs at given @addr in @cu_die. Passed DIEs
 * should be subprogram or inlined-subroutines.
 */
int cu_walk_functions_at(Dwarf_Die *cu_die, Dwarf_Addr addr,
                    int (*callback)(Dwarf_Die *, void *), void *data)
{
        Dwarf_Die die_mem;
        Dwarf_Die *sc_die;
        int ret = -ENOENT;

        /* Inlined function could be recursive. Trace it until fail */
        for (sc_die = die_find_realfunc(cu_die, addr, &die_mem);
             sc_die != NULL;
             sc_die = die_find_child(sc_die, __die_find_inline_cb, &addr,
                                     &die_mem)) {
                ret = callback(sc_die, data);
                if (ret)
                        break;
        }

        return ret;

}

/**
 * die_compare_name - Compare diename and tname
 * @dw_die: a DIE
 * @tname: a string of target name
 *
 * Compare the name of @dw_die and @tname. Return false if @dw_die has no name.
 */
bool die_compare_name(Dwarf_Die *dw_die, const char *tname)
{
        const char *name;
        name = dwarf_diename(dw_die);
        return name ? (strcmp(tname, name) == 0) : false;
}

/**
 * die_get_call_lineno - Get callsite line number of inline-function instance
 * @in_die: a DIE of an inlined function instance
 *
 * Get call-site line number of @in_die. This means from where the inline
 * function is called.
 */
int die_get_call_lineno(Dwarf_Die *in_die)
{
        Dwarf_Attribute attr;
        Dwarf_Word ret;

        if (!dwarf_attr(in_die, DW_AT_call_line, &attr))
                return -ENOENT;

        dwarf_formudata(&attr, &ret);
        return (int)ret;
}

/**
 * die_get_type - Get type DIE
 * @vr_die: a DIE of a variable
 * @die_mem: where to store a type DIE
 *
 * Get a DIE of the type of given variable (@vr_die), and store
 * it to die_mem. Return NULL if fails to get a type DIE.
 */
Dwarf_Die *die_get_type(Dwarf_Die *vr_die, Dwarf_Die *die_mem)
{
        Dwarf_Attribute attr;

        if (dwarf_attr_integrate(vr_die, DW_AT_type, &attr) &&
            dwarf_formref_die(&attr, die_mem))
                return die_mem;
        else
                return NULL;
}

/* Get a type die, but skip qualifiers */
static Dwarf_Die *__die_get_real_type(Dwarf_Die *vr_die, Dwarf_Die *die_mem)
{
        int tag;

        do {
                vr_die = die_get_type(vr_die, die_mem);
                if (!vr_die)
                        break;
                tag = dwarf_tag(vr_die);
        } while (tag == DW_TAG_const_type ||
                 tag == DW_TAG_restrict_type ||
                 tag == DW_TAG_volatile_type ||
                 tag == DW_TAG_shared_type);

        return vr_die;
}

/**
 * die_get_real_type - Get a type die, but skip qualifiers and typedef
 * @vr_die: a DIE of a variable
 * @die_mem: where to store a type DIE
 *
 * Get a DIE of the type of given variable (@vr_die), and store
 * it to die_mem. Return NULL if fails to get a type DIE.
 * If the type is qualifiers (e.g. const) or typedef, this skips it
 * and tries to find real type (structure or basic types, e.g. int).
 */
Dwarf_Die *die_get_real_type(Dwarf_Die *vr_die, Dwarf_Die *die_mem)
{
        do {
                vr_die = __die_get_real_type(vr_die, die_mem);
        } while (vr_die && dwarf_tag(vr_die) == DW_TAG_typedef);

        return vr_die;
}

/* Get attribute and translate it as a udata */
static int die_get_attr_udata(Dwarf_Die *tp_die, unsigned int attr_name,
                              Dwarf_Word *result)
{
        Dwarf_Attribute attr;

        if (dwarf_attr(tp_die, attr_name, &attr) == NULL ||
            dwarf_formudata(&attr, result) != 0)
                return -ENOENT;

        return 0;
}

/* Get attribute and translate it as a sdata */
static int die_get_attr_sdata(Dwarf_Die *tp_die, unsigned int attr_name,
                              Dwarf_Sword *result)
{
        Dwarf_Attribute attr;

        if (dwarf_attr(tp_die, attr_name, &attr) == NULL ||
            dwarf_formsdata(&attr, result) != 0)
                return -ENOENT;

        return 0;
}

/**
 * die_is_signed_type - Check whether a type DIE is signed or not
 * @tp_die: a DIE of a type
 *
 * Get the encoding of @tp_die and return true if the encoding
 * is signed.
 */
bool die_is_signed_type(Dwarf_Die *tp_die)
{
        Dwarf_Word ret;

        if (die_get_attr_udata(tp_die, DW_AT_encoding, &ret))
                return false;

        return (ret == DW_ATE_signed_char || ret == DW_ATE_signed ||
                ret == DW_ATE_signed_fixed);
}

/**
 * die_is_func_def - Ensure that this DIE is a subprogram and definition
 * @dw_die: a DIE
 *
 * Ensure that this DIE is a subprogram and NOT a declaration. This
 * returns true if @dw_die is a function definition.
 **/
bool die_is_func_def(Dwarf_Die *dw_die)
{
        Dwarf_Attribute attr;

        return (dwarf_tag(dw_die) == DW_TAG_subprogram &&
                dwarf_attr(dw_die, DW_AT_declaration, &attr) == NULL);
}

/**
 * die_is_func_instance - Ensure that this DIE is an instance of a subprogram
 * @dw_die: a DIE
 *
 * Ensure that this DIE is an instance (which has an entry address).
 * This returns true if @dw_die is a function instance. If not, you need to
 * call die_walk_instances() to find actual instances.
 **/
bool die_is_func_instance(Dwarf_Die *dw_die)
{
        Dwarf_Addr tmp;

        /* Actually gcc optimizes non-inline as like as inlined */
        return !dwarf_func_inline(dw_die) && dwarf_entrypc(dw_die, &tmp) == 0;
}
/**
 * die_get_data_member_location - Get the data-member offset
 * @mb_die: a DIE of a member of a data structure
 * @offs: The offset of the member in the data structure
 *
 * Get the offset of @mb_die in the data structure including @mb_die, and
 * stores result offset to @offs. If any error occurs this returns errno.
 */
int die_get_data_member_location(Dwarf_Die *mb_die, Dwarf_Word *offs)
{
        Dwarf_Attribute attr;
        Dwarf_Op *expr;
        size_t nexpr;
        int ret;

        if (dwarf_attr(mb_die, DW_AT_data_member_location, &attr) == NULL)
                return -ENOENT;

        if (dwarf_formudata(&attr, offs) != 0) {
                /* DW_AT_data_member_location should be DW_OP_plus_uconst */
                ret = dwarf_getlocation(&attr, &expr, &nexpr);
                if (ret < 0 || nexpr == 0)
                        return -ENOENT;

                if (expr[0].atom != DW_OP_plus_uconst || nexpr != 1) {
                        pr_debug("Unable to get offset:Unexpected OP %x (%zd)\n",
                                 expr[0].atom, nexpr);
                        return -ENOTSUP;
                }
                *offs = (Dwarf_Word)expr[0].number;
        }
        return 0;
}

/* Get the call file index number in CU DIE */
static int die_get_call_fileno(Dwarf_Die *in_die)
{
        Dwarf_Sword idx;

        if (die_get_attr_sdata(in_die, DW_AT_call_file, &idx) == 0)
                return (int)idx;
        else
                return -ENOENT;
}

/* Get the declared file index number in CU DIE */
static int die_get_decl_fileno(Dwarf_Die *pdie)
{
        Dwarf_Sword idx;

        if (die_get_attr_sdata(pdie, DW_AT_decl_file, &idx) == 0)
                return (int)idx;
        else
                return -ENOENT;
}

/**
 * die_get_call_file - Get callsite file name of inlined function instance
 * @in_die: a DIE of an inlined function instance
 *
 * Get call-site file name of @in_die. This means from which file the inline
 * function is called.
 */
const char *die_get_call_file(Dwarf_Die *in_die)
{
        Dwarf_Die cu_die;
        Dwarf_Files *files;
        int idx;

        idx = die_get_call_fileno(in_die);
        if (idx < 0 || !dwarf_diecu(in_die, &cu_die, NULL, NULL) ||
            dwarf_getsrcfiles(&cu_die, &files, NULL) != 0)
                return NULL;

        return dwarf_filesrc(files, idx, NULL, NULL);
}


/**
 * die_find_child - Generic DIE search function in DIE tree
 * @rt_die: a root DIE
 * @callback: a callback function
 * @data: a user data passed to the callback function
 * @die_mem: a buffer for result DIE
 *
 * Trace DIE tree from @rt_die and call @callback for each child DIE.
 * If @callback returns DIE_FIND_CB_END, this stores the DIE into
 * @die_mem and returns it. If @callback returns DIE_FIND_CB_CONTINUE,
 * this continues to trace the tree. Optionally, @callback can return
 * DIE_FIND_CB_CHILD and DIE_FIND_CB_SIBLING, those means trace only
 * the children and trace only the siblings respectively.
 * Returns NULL if @callback can't find any appropriate DIE.
 */
Dwarf_Die *die_find_child(Dwarf_Die *rt_die,
                          int (*callback)(Dwarf_Die *, void *),
                          void *data, Dwarf_Die *die_mem)
{
        Dwarf_Die child_die;
        int ret;

        ret = dwarf_child(rt_die, die_mem);
        if (ret != 0)
                return NULL;

        do {
                ret = callback(die_mem, data);
                if (ret == DIE_FIND_CB_END)
                        return die_mem;

                if ((ret & DIE_FIND_CB_CHILD) &&
                    die_find_child(die_mem, callback, data, &child_die)) {
                        memcpy(die_mem, &child_die, sizeof(Dwarf_Die));
                        return die_mem;
                }
        } while ((ret & DIE_FIND_CB_SIBLING) &&
                 dwarf_siblingof(die_mem, die_mem) == 0);

        return NULL;
}

struct __addr_die_search_param {
        Dwarf_Addr      addr;
        Dwarf_Die       *die_mem;
};

/* die_find callback for non-inlined function search */
static int __die_search_func_cb(Dwarf_Die *fn_die, void *data)
{
        struct __addr_die_search_param *ad = data;

        /*
         * Since a declaration entry doesn't has given pc, this always returns
         * function definition entry.
         */
        if (dwarf_tag(fn_die) == DW_TAG_subprogram &&
            dwarf_haspc(fn_die, ad->addr)) {
                memcpy(ad->die_mem, fn_die, sizeof(Dwarf_Die));
                return DWARF_CB_ABORT;
        }
        return DWARF_CB_OK;
}

/**
 * die_find_realfunc - Search a non-inlined function at given address
 * @cu_die: a CU DIE which including @addr
 * @addr: target address
 * @die_mem: a buffer for result DIE
 *
 * Search a non-inlined function DIE which includes @addr. Stores the
 * DIE to @die_mem and returns it if found. Returns NULL if failed.
 */
Dwarf_Die *die_find_realfunc(Dwarf_Die *cu_die, Dwarf_Addr addr,
                                    Dwarf_Die *die_mem)
{
        struct __addr_die_search_param ad;
        ad.addr = addr;
        ad.die_mem = die_mem;
        /* dwarf_getscopes can't find subprogram. */
        if (!dwarf_getfuncs(cu_die, __die_search_func_cb, &ad, 0))
                return NULL;
        else
                return die_mem;
}

/* die_find callback for inline function search */
static int __die_find_inline_cb(Dwarf_Die *die_mem, void *data)
{
        Dwarf_Addr *addr = data;

        if (dwarf_tag(die_mem) == DW_TAG_inlined_subroutine &&
            dwarf_haspc(die_mem, *addr))
                return DIE_FIND_CB_END;

        return DIE_FIND_CB_CONTINUE;
}

/**
 * die_find_top_inlinefunc - Search the top inlined function at given address
 * @sp_die: a subprogram DIE which including @addr
 * @addr: target address
 * @die_mem: a buffer for result DIE
 *
 * Search an inlined function DIE which includes @addr. Stores the
 * DIE to @die_mem and returns it if found. Returns NULL if failed.
 * Even if several inlined functions are expanded recursively, this
 * doesn't trace it down, and returns the topmost one.
 */
Dwarf_Die *die_find_top_inlinefunc(Dwarf_Die *sp_die, Dwarf_Addr addr,
                                   Dwarf_Die *die_mem)
{
        return die_find_child(sp_die, __die_find_inline_cb, &addr, die_mem);
}

/**
 * die_find_inlinefunc - Search an inlined function at given address
 * @sp_die: a subprogram DIE which including @addr
 * @addr: target address
 * @die_mem: a buffer for result DIE
 *
 * Search an inlined function DIE which includes @addr. Stores the
 * DIE to @die_mem and returns it if found. Returns NULL if failed.
 * If several inlined functions are expanded recursively, this trace
 * it down and returns deepest one.
 */
Dwarf_Die *die_find_inlinefunc(Dwarf_Die *sp_die, Dwarf_Addr addr,
                               Dwarf_Die *die_mem)
{
        Dwarf_Die tmp_die;

        sp_die = die_find_child(sp_die, __die_find_inline_cb, &addr, &tmp_die);
        if (!sp_die)
                return NULL;

        /* Inlined function could be recursive. Trace it until fail */
        while (sp_die) {
                memcpy(die_mem, sp_die, sizeof(Dwarf_Die));
                sp_die = die_find_child(sp_die, __die_find_inline_cb, &addr,
                                        &tmp_die);
        }

        return die_mem;
}

struct __instance_walk_param {
        void    *addr;
        int     (*callback)(Dwarf_Die *, void *);
        void    *data;
        int     retval;
};

static int __die_walk_instances_cb(Dwarf_Die *inst, void *data)
{
        struct __instance_walk_param *iwp = data;
        Dwarf_Attribute attr_mem;
        Dwarf_Die origin_mem;
        Dwarf_Attribute *attr;
        Dwarf_Die *origin;
        int tmp;

        attr = dwarf_attr(inst, DW_AT_abstract_origin, &attr_mem);
        if (attr == NULL)
                return DIE_FIND_CB_CONTINUE;

        origin = dwarf_formref_die(attr, &origin_mem);
        if (origin == NULL || origin->addr != iwp->addr)
                return DIE_FIND_CB_CONTINUE;

        /* Ignore redundant instances */
        if (dwarf_tag(inst) == DW_TAG_inlined_subroutine) {
                dwarf_decl_line(origin, &tmp);
                if (die_get_call_lineno(inst) == tmp) {
                        tmp = die_get_decl_fileno(origin);
                        if (die_get_call_fileno(inst) == tmp)
                                return DIE_FIND_CB_CONTINUE;
                }
        }

        iwp->retval = iwp->callback(inst, iwp->data);

        return (iwp->retval) ? DIE_FIND_CB_END : DIE_FIND_CB_CONTINUE;
}

/**
 * die_walk_instances - Walk on instances of given DIE
 * @or_die: an abstract original DIE
 * @callback: a callback function which is called with instance DIE
 * @data: user data
 *
 * Walk on the instances of give @in_die. @in_die must be an inlined function
 * declartion. This returns the return value of @callback if it returns
 * non-zero value, or -ENOENT if there is no instance.
 */
int die_walk_instances(Dwarf_Die *or_die, int (*callback)(Dwarf_Die *, void *),
                       void *data)
{
        Dwarf_Die cu_die;
        Dwarf_Die die_mem;
        struct __instance_walk_param iwp = {
                .addr = or_die->addr,
                .callback = callback,
                .data = data,
                .retval = -ENOENT,
        };

        if (dwarf_diecu(or_die, &cu_die, NULL, NULL) == NULL)
                return -ENOENT;

        die_find_child(&cu_die, __die_walk_instances_cb, &iwp, &die_mem);

        return iwp.retval;
}

/* Line walker internal parameters */
struct __line_walk_param {
        bool recursive;
        line_walk_callback_t callback;
        void *data;
        int retval;
};

static int __die_walk_funclines_cb(Dwarf_Die *in_die, void *data)
{
        struct __line_walk_param *lw = data;
        Dwarf_Addr addr = 0;
        const char *fname;
        int lineno;

        if (dwarf_tag(in_die) == DW_TAG_inlined_subroutine) {
                fname = die_get_call_file(in_die);
                lineno = die_get_call_lineno(in_die);
                if (fname && lineno > 0 && dwarf_entrypc(in_die, &addr) == 0) {
                        lw->retval = lw->callback(fname, lineno, addr, lw->data);
                        if (lw->retval != 0)
                                return DIE_FIND_CB_END;
                }
        }
        if (!lw->recursive)
                /* Don't need to search recursively */
                return DIE_FIND_CB_SIBLING;

        if (addr) {
                fname = dwarf_decl_file(in_die);
                if (fname && dwarf_decl_line(in_die, &lineno) == 0) {
                        lw->retval = lw->callback(fname, lineno, addr, lw->data);
                        if (lw->retval != 0)
                                return DIE_FIND_CB_END;
                }
        }

        /* Continue to search nested inlined function call-sites */
        return DIE_FIND_CB_CONTINUE;
}

/* Walk on lines of blocks included in given DIE */
static int __die_walk_funclines(Dwarf_Die *sp_die, bool recursive,
                                line_walk_callback_t callback, void *data)
{
        struct __line_walk_param lw = {
                .recursive = recursive,
                .callback = callback,
                .data = data,
                .retval = 0,
        };
        Dwarf_Die die_mem;
        Dwarf_Addr addr;
        const char *fname;
        int lineno;

        /* Handle function declaration line */
        fname = dwarf_decl_file(sp_die);
        if (fname && dwarf_decl_line(sp_die, &lineno) == 0 &&
            dwarf_entrypc(sp_die, &addr) == 0) {
                lw.retval = callback(fname, lineno, addr, data);
                if (lw.retval != 0)
                        goto done;
        }
        die_find_child(sp_die, __die_walk_funclines_cb, &lw, &die_mem);
done:
        return lw.retval;
}

static int __die_walk_culines_cb(Dwarf_Die *sp_die, void *data)
{
        struct __line_walk_param *lw = data;

        lw->retval = __die_walk_funclines(sp_die, true, lw->callback, lw->data);
        if (lw->retval != 0)
                return DWARF_CB_ABORT;

        return DWARF_CB_OK;
}

/**
 * die_walk_lines - Walk on lines inside given DIE
 * @rt_die: a root DIE (CU, subprogram or inlined_subroutine)
 * @callback: callback routine
 * @data: user data
 *
 * Walk on all lines inside given @rt_die and call @callback on each line.
 * If the @rt_die is a function, walk only on the lines inside the function,
 * otherwise @rt_die must be a CU DIE.
 * Note that this walks not only dwarf line list, but also function entries
 * and inline call-site.
 */
int die_walk_lines(Dwarf_Die *rt_die, line_walk_callback_t callback, void *data)
{
        Dwarf_Lines *lines;
        Dwarf_Line *line;
        Dwarf_Addr addr;
        const char *fname;
        int lineno, ret = 0;
        Dwarf_Die die_mem, *cu_die;
        size_t nlines, i;

        /* Get the CU die */
        if (dwarf_tag(rt_die) != DW_TAG_compile_unit)
                cu_die = dwarf_diecu(rt_die, &die_mem, NULL, NULL);
        else
                cu_die = rt_die;
        if (!cu_die) {
                pr_debug2("Failed to get CU from given DIE.\n");
                return -EINVAL;
        }

        /* Get lines list in the CU */
        if (dwarf_getsrclines(cu_die, &lines, &nlines) != 0) {
                pr_debug2("Failed to get source lines on this CU.\n");
                return -ENOENT;
        }
        pr_debug2("Get %zd lines from this CU\n", nlines);

        /* Walk on the lines on lines list */
        for (i = 0; i < nlines; i++) {
                line = dwarf_onesrcline(lines, i);
                if (line == NULL ||
                    dwarf_lineno(line, &lineno) != 0 ||
                    dwarf_lineaddr(line, &addr) != 0) {
                        pr_debug2("Failed to get line info. "
                                  "Possible error in debuginfo.\n");
                        continue;
                }
                /* Filter lines based on address */
                if (rt_die != cu_die)
                        /*
                         * Address filtering
                         * The line is included in given function, and
                         * no inline block includes it.
                         */
                        if (!dwarf_haspc(rt_die, addr) ||
                            die_find_inlinefunc(rt_die, addr, &die_mem))
                                continue;
                /* Get source line */
                fname = dwarf_linesrc(line, NULL, NULL);

                ret = callback(fname, lineno, addr, data);
                if (ret != 0)
                        return ret;
        }

        /*
         * Dwarf lines doesn't include function declarations and inlined
         * subroutines. We have to check functions list or given function.
         */
        if (rt_die != cu_die)
                /*
                 * Don't need walk functions recursively, because nested
                 * inlined functions don't have lines of the specified DIE.
                 */
                ret = __die_walk_funclines(rt_die, false, callback, data);
        else {
                struct __line_walk_param param = {
                        .callback = callback,
                        .data = data,
                        .retval = 0,
                };
                dwarf_getfuncs(cu_die, __die_walk_culines_cb, &param, 0);
                ret = param.retval;
        }

        return ret;
}

struct __find_variable_param {
        const char *name;
        Dwarf_Addr addr;
};

static int __die_find_variable_cb(Dwarf_Die *die_mem, void *data)
{
        struct __find_variable_param *fvp = data;
        Dwarf_Attribute attr;
        int tag;

        tag = dwarf_tag(die_mem);
        if ((tag == DW_TAG_formal_parameter ||
             tag == DW_TAG_variable) &&
            die_compare_name(die_mem, fvp->name) &&
        /* Does the DIE have location information or external instance? */
            (dwarf_attr(die_mem, DW_AT_external, &attr) ||
             dwarf_attr(die_mem, DW_AT_location, &attr)))
                return DIE_FIND_CB_END;
        if (dwarf_haspc(die_mem, fvp->addr))
                return DIE_FIND_CB_CONTINUE;
        else
                return DIE_FIND_CB_SIBLING;
}

/**
 * die_find_variable_at - Find a given name variable at given address
 * @sp_die: a function DIE
 * @name: variable name
 * @addr: address
 * @die_mem: a buffer for result DIE
 *
 * Find a variable DIE called @name at @addr in @sp_die.
 */
Dwarf_Die *die_find_variable_at(Dwarf_Die *sp_die, const char *name,
                                Dwarf_Addr addr, Dwarf_Die *die_mem)
{
        struct __find_variable_param fvp = { .name = name, .addr = addr};

        return die_find_child(sp_die, __die_find_variable_cb, (void *)&fvp,
                              die_mem);
}

static int __die_find_member_cb(Dwarf_Die *die_mem, void *data)
{
        const char *name = data;

        if (dwarf_tag(die_mem) == DW_TAG_member) {
                if (die_compare_name(die_mem, name))
                        return DIE_FIND_CB_END;
                else if (!dwarf_diename(die_mem)) {     /* Unnamed structure */
                        Dwarf_Die type_die, tmp_die;
                        if (die_get_type(die_mem, &type_die) &&
                            die_find_member(&type_die, name, &tmp_die))
                                return DIE_FIND_CB_END;
                }
        }
        return DIE_FIND_CB_SIBLING;
}

/**
 * die_find_member - Find a given name member in a data structure
 * @st_die: a data structure type DIE
 * @name: member name
 * @die_mem: a buffer for result DIE
 *
 * Find a member DIE called @name in @st_die.
 */
Dwarf_Die *die_find_member(Dwarf_Die *st_die, const char *name,
                           Dwarf_Die *die_mem)
{
        return die_find_child(st_die, __die_find_member_cb, (void *)name,
                              die_mem);
}

/**
 * die_get_typename - Get the name of given variable DIE
 * @vr_die: a variable DIE
 * @buf: a buffer for result type name
 * @len: a max-length of @buf
 *
 * Get the name of @vr_die and stores it to @buf. Return the actual length
 * of type name if succeeded. Return -E2BIG if @len is not enough long, and
 * Return -ENOENT if failed to find type name.
 * Note that the result will stores typedef name if possible, and stores
 * "*(function_type)" if the type is a function pointer.
 */
int die_get_typename(Dwarf_Die *vr_die, char *buf, int len)
{
        Dwarf_Die type;
        int tag, ret, ret2;
        const char *tmp = "";

        if (__die_get_real_type(vr_die, &type) == NULL)
                return -ENOENT;

        tag = dwarf_tag(&type);
        if (tag == DW_TAG_array_type || tag == DW_TAG_pointer_type)
                tmp = "*";
        else if (tag == DW_TAG_subroutine_type) {
                /* Function pointer */
                ret = snprintf(buf, len, "(function_type)");
                return (ret >= len) ? -E2BIG : ret;
        } else {
                if (!dwarf_diename(&type))
                        return -ENOENT;
                if (tag == DW_TAG_union_type)
                        tmp = "union ";
                else if (tag == DW_TAG_structure_type)
                        tmp = "struct ";
                else if (tag == DW_TAG_enumeration_type)
                        tmp = "enum ";
                /* Write a base name */
                ret = snprintf(buf, len, "%s%s", tmp, dwarf_diename(&type));
                return (ret >= len) ? -E2BIG : ret;
        }
        ret = die_get_typename(&type, buf, len);
        if (ret > 0) {
                ret2 = snprintf(buf + ret, len - ret, "%s", tmp);
                ret = (ret2 >= len - ret) ? -E2BIG : ret2 + ret;
        }
        return ret;
}

/**
 * die_get_varname - Get the name and type of given variable DIE
 * @vr_die: a variable DIE
 * @buf: a buffer for type and variable name
 * @len: the max-length of @buf
 *
 * Get the name and type of @vr_die and stores it in @buf as "type\tname".
 */
int die_get_varname(Dwarf_Die *vr_die, char *buf, int len)
{
        int ret, ret2;

        ret = die_get_typename(vr_die, buf, len);
        if (ret < 0) {
                pr_debug("Failed to get type, make it unknown.\n");
                ret = snprintf(buf, len, "(unknown_type)");
        }
        if (ret > 0) {
                ret2 = snprintf(buf + ret, len - ret, "\t%s",
                                dwarf_diename(vr_die));
                ret = (ret2 >= len - ret) ? -E2BIG : ret2 + ret;
        }
        return ret;
}