libdwarf的使用

       例子来源于libdwarf的发布版本，可以参考例子前面的版权声明。我加了部分注释（原有注释用/**/，我加的注释用//）.

/*
  Copyright (c) 2009-2010 David Anderson.  All rights reserved.
 
  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions are met:
  * Redistributions of source code must retain the above copyright
    notice, this list of conditions and the following disclaimer.
  * Redistributions in binary form must reproduce the above copyright
    notice, this list of conditions and the following disclaimer in the
    documentation and/or other materials provided with the distribution.
  * Neither the name of the example nor the
    names of its contributors may be used to endorse or promote products
    derived from this software without specific prior written permission.
 
  THIS SOFTWARE IS PROVIDED BY David Anderson ''AS IS'' AND ANY
  EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  DISCLAIMED. IN NO EVENT SHALL David Anderson BE LIABLE FOR ANY
  DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
*/
/*  simplereader.c
    This is an example of code reading dwarf .debug_info.
    It is kept as simple as possible to expose essential features.
    It does not do all possible error reporting or error handling.

    The --names 
    option adds some extra printing.

    To use, try
        make
        ./simplereader simplereader
*/
#include <sys/types.h> /* For open() */
#include <sys/stat.h>  /* For open() */
#include <fcntl.h>     /* For open() */
#include <stdlib.h>     /* For exit() */
#include <unistd.h>     /* For close() */
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include "dwarf.h"
#include "libdwarf.h"

struct srcfilesdata {
    char ** srcfiles;
    Dwarf_Signed srcfilescount;
    int srcfilesres;
};

static void read_cu_list(Dwarf_Debug dbg);
static void print_die_data(Dwarf_Debug dbg, Dwarf_Die print_me,int level,
   struct srcfilesdata *sf);
static void get_die_and_siblings(Dwarf_Debug dbg, Dwarf_Die in_die,int in_level,
   struct srcfilesdata *sf);
static void resetsrcfiles(Dwarf_Debug dbg,struct srcfilesdata *sf);

static int namesoptionon = 0;

int 
main(int argc, char **argv)
{

    Dwarf_Debug dbg = 0;
    int fd = -1;
    const char *filepath = "<stdin>";
    int res = DW_DLV_ERROR;
    Dwarf_Error error;
    Dwarf_Handler errhand = 0;
    Dwarf_Ptr errarg = 0;

    if(argc < 2) {
        fd = 0; /* stdin */
    } else {
        int i = 0;
        for(i = 1; i < (argc-1) ; ++i) {
            if(strcmp(argv[i],"--names") == 0) {
                namesoptionon=1;
            } else {
                printf("Unknown argument \"%s\" ignored\n",argv[i]);
            }
        }
        filepath = argv[i];
        fd = open(filepath,O_RDONLY);  // Open the object file before dwarf_init
    }
    if(argc > 2) {
    }
    if(fd < 0) {
        printf("Failure attempting to open \"%s\"\n",filepath);
    }
    res = dwarf_init(fd,DW_DLC_READ,errhand,errarg, &dbg,&error); // Obtain the debug info as stored int dbg
    if(res != DW_DLV_OK) {
        printf("Giving up, cannot do DWARF processing\n");
        exit(1);
    }

    read_cu_list(dbg);      // read and print all compiler units
    res = dwarf_finish(dbg,&error);
    if(res != DW_DLV_OK) {
        printf("dwarf_finish failed!\n");
    }
    close(fd);      // Close the object file after dwarf_finish
    return 0;
}

static void 
read_cu_list(Dwarf_Debug dbg)
{
    Dwarf_Unsigned cu_header_length = 0;
    Dwarf_Half version_stamp = 0;
    Dwarf_Unsigned abbrev_offset = 0;
    Dwarf_Half address_size = 0;
    Dwarf_Unsigned next_cu_header = 0;
    Dwarf_Error error;
    int cu_number = 0;

    for(;;++cu_number) {
        struct srcfilesdata sf;
        sf.srcfilesres = DW_DLV_ERROR;
        sf.srcfiles = 0;
        sf.srcfilescount = 0;
        Dwarf_Die no_die = 0;
        Dwarf_Die cu_die = 0;
        int res = DW_DLV_ERROR;
        res = dwarf_next_cu_header(dbg,&cu_header_length,
            &version_stamp, &abbrev_offset, &address_size,
            &next_cu_header, &error);            // get the offset of the next CU header
        if(res == DW_DLV_ERROR) {
            printf("Error in dwarf_next_cu_header\n");
            exit(1);
        }
        if(res == DW_DLV_NO_ENTRY) {
            /* Done. */
            return;
        }
        /* The CU will have a single sibling, a cu_die. */
        res = dwarf_siblingof(dbg,no_die,&cu_die,&error);  // get the first die (cu, pu, or tu) of dbg
        if(res == DW_DLV_ERROR) {
            printf("Error in dwarf_siblingof on CU die \n");
            exit(1);
        }
        if(res == DW_DLV_NO_ENTRY) {
            /* Impossible case. */
            printf("no entry! in dwarf_siblingof on CU die \n");
            exit(1);
        }
        get_die_and_siblings(dbg,cu_die,0,&sf);      // travel the tree-grouped dies in pre-order
        dwarf_dealloc(dbg,cu_die,DW_DLA_DIE);
        resetsrcfiles(dbg,&sf);
    }
}

static void
get_die_and_siblings(Dwarf_Debug dbg, Dwarf_Die in_die,int in_level,
   struct srcfilesdata *sf)
{
    int res = DW_DLV_ERROR;
    Dwarf_Die cur_die=in_die;
    Dwarf_Die child = 0;
    Dwarf_Error error;
   
    print_die_data(dbg,in_die,in_level,sf);     // print out the die element first (root node first)

    for(;;) {
        Dwarf_Die sib_die = 0;
        res = dwarf_child(cur_die,&child,&error);
        if(res == DW_DLV_ERROR) {
            printf("Error in dwarf_child , level %d \n",in_level);
            exit(1);
        }
        if(res == DW_DLV_OK) {       // foreach child-node, call the same function recursively (left first)                  
            get_die_and_siblings(dbg,child,in_level+1,sf);
        }
        /* res == DW_DLV_NO_ENTRY */
        res = dwarf_siblingof(dbg,cur_die,&sib_die,&error); // deal with the siblings last
        if(res == DW_DLV_ERROR) {
            printf("Error in dwarf_siblingof , level %d \n",in_level);
            exit(1);
        }
        if(res == DW_DLV_NO_ENTRY) {
            /* Done at this level. */
            break;
        }
        /* res == DW_DLV_OK */
        if(cur_die != in_die) {
            dwarf_dealloc(dbg,cur_die,DW_DLA_DIE);
        }
        cur_die = sib_die;
        print_die_data(dbg,cur_die,in_level,sf);
    }
    return;
}

// Get the address-typed value of an attribute
static void
get_addr(Dwarf_Attribute attr,Dwarf_Addr *val)
{
    Dwarf_Error error = 0;
    int res;
    Dwarf_Addr uval = 0;
    res = dwarf_formaddr(attr,&uval,&error);
    if(res == DW_DLV_OK) {
        *val = uval;
        return;
    }
    return;
}

// Get the integer-typed value of an attribute
static void
get_number(Dwarf_Attribute attr,Dwarf_Unsigned *val)
{
    Dwarf_Error error = 0;
    int res;
    Dwarf_Signed sval = 0;
    Dwarf_Unsigned uval = 0;
    res = dwarf_formudata(attr,&uval,&error);
    if(res == DW_DLV_OK) {
        *val = uval;
        return;
    }
    res = dwarf_formsdata(attr,&sval,&error);
    if(res == DW_DLV_OK) {
        *val = sval;
        return;
    }
    return;
}

// print the subprogram
static void
print_subprog(Dwarf_Debug dbg,Dwarf_Die die, int level,
    struct srcfilesdata *sf)
{
    int res;
    Dwarf_Error error = 0;
    Dwarf_Attribute *attrbuf = 0;
    Dwarf_Addr lowpc = 0;
    Dwarf_Addr highpc = 0;
    Dwarf_Signed attrcount = 0;
    Dwarf_Unsigned i;
    Dwarf_Unsigned filenum = 0;
    Dwarf_Unsigned linenum = 0;
    char *filename = 0;
    res = dwarf_attrlist(die,&attrbuf,&attrcount,&error);     // obtain the attribute list of this die
    if(res != DW_DLV_OK) {
        return;
    }
    for(i = 0; i < attrcount ; ++i) {
        Dwarf_Half aform;
        res = dwarf_whatattr(attrbuf[i],&aform,&error);   // obtain the attribute code into aform
        if(res == DW_DLV_OK) {
            if(aform == DW_AT_decl_file) {                // 1. in which file is this subprogram defined
                get_number(attrbuf[i],&filenum);          // get the file number
                if((filenum > 0) && (sf->srcfilescount > (filenum-1))) {
                    filename = sf->srcfiles[filenum-1];   // get the finename      
                }
            }
            if(aform == DW_AT_decl_line) {      // 2. at which line is this subprogram defined
                get_number(attrbuf[i],&linenum);
            }
            if(aform == DW_AT_low_pc) {         // 3. the low memory address occupied by this subprogram 
                get_addr(attrbuf[i],&lowpc);
            }
            if(aform == DW_AT_high_pc) {		// 4. the high memory address occupied by this subprogram
                get_addr(attrbuf[i],&highpc);
            }
        }
        dwarf_dealloc(dbg,attrbuf[i],DW_DLA_ATTR);
    }
    if(filenum || linenum) {
        printf("<%3d> file: %" DW_PR_DUu " %s  line %"
            DW_PR_DUu "\n",level,filenum,filename?filename:"",linenum);
    }
    if(lowpc) {
        printf("<%3d> low_pc : 0x%" DW_PR_DUx  "\n",
            level, (Dwarf_Unsigned)lowpc);
    }
    if(highpc) {
        printf("<%3d> high_pc: 0x%" DW_PR_DUx  "\n",
            level, (Dwarf_Unsigned)highpc);
    }
    dwarf_dealloc(dbg,attrbuf,DW_DLA_LIST);
}

// print out the compilation directory
static void
print_comp_dir(Dwarf_Debug dbg,Dwarf_Die die,int level, struct srcfilesdata *sf)
{
    int res;
    Dwarf_Error error = 0;
    Dwarf_Attribute *attrbuf = 0;
    Dwarf_Signed attrcount = 0;
    Dwarf_Unsigned i;
    res = dwarf_attrlist(die,&attrbuf,&attrcount,&error);   // Obtain the attribute list for a die
    if(res != DW_DLV_OK) {
        return;
    }
    sf->srcfilesres = dwarf_srcfiles(die,&sf->srcfiles,&sf->srcfilescount, 
        &error);   // Obtain the source file list associated with this compiler-unit die
    for(i = 0; i < attrcount ; ++i) {
        Dwarf_Half aform;
        res = dwarf_whatattr(attrbuf[i],&aform,&error); // Obtain and store the attribute code into aform
        if(res == DW_DLV_OK) {
            if(aform == DW_AT_comp_dir) {      // If it is the compilation directory
                char *name = 0;
                res = dwarf_formstring(attrbuf[i],&name,&error); // Obtain the string-type value for this attribute
                if(res == DW_DLV_OK) {
                    printf(    "<%3d> compilation directory : \"%s\"\n",
                        level,name);
                }
            }
            if(aform == DW_AT_stmt_list) {
                /* Offset of stmt list for this CU in .debug_line */
            }
        }
        dwarf_dealloc(dbg,attrbuf[i],DW_DLA_ATTR);
    }
    dwarf_dealloc(dbg,attrbuf,DW_DLA_LIST);
}

// reset the struct srcfilesdata
static void
resetsrcfiles(Dwarf_Debug dbg,struct srcfilesdata *sf)
{
    Dwarf_Signed sri = 0;
    for (sri = 0; sri < sf->srcfilescount; ++sri) {
        dwarf_dealloc(dbg, sf->srcfiles[sri], DW_DLA_STRING);
    }
    dwarf_dealloc(dbg, sf->srcfiles, DW_DLA_LIST);
    sf->srcfilesres = DW_DLV_ERROR;
    sf->srcfiles = 0;
    sf->srcfilescount = 0;
}

// print out the die element
static void
print_die_data(Dwarf_Debug dbg, Dwarf_Die print_me,int level,
    struct srcfilesdata *sf)
{
    char *name = 0;
    Dwarf_Error error = 0;
    Dwarf_Half tag = 0;
    const char *tagname = 0;
    int localname = 0;

    int res = dwarf_diename(print_me,&name,&error);		// get the value of the name attribute 

    if(res == DW_DLV_ERROR) {
        printf("Error in dwarf_diename , level %d \n",level);
        exit(1);
    }
    if(res == DW_DLV_NO_ENTRY) {
        name = "<no DW_AT_name attr>";
        localname = 1;
    }
    res = dwarf_tag(print_me,&tag,&error);		// get the tag number
    if(res != DW_DLV_OK) {
        printf("Error in dwarf_tag , level %d \n",level);
        exit(1);
    }
    res = dwarf_get_TAG_name(tag,&tagname);		// get the tag name
    if(res != DW_DLV_OK) {
        printf("Error in dwarf_get_TAG_name , level %d \n",level);
        exit(1);
    }
    if(namesoptionon) {
        if( tag == DW_TAG_subprogram) {              // if it is a subprogram, print where it is defined and stored
            printf(    "<%3d> subprogram            : \"%s\"\n",level,name);
            print_subprog(dbg,print_me,level,sf);
        } else if (tag == DW_TAG_compile_unit ||     // if it is a file, print the compilation directory
            tag == DW_TAG_partial_unit ||
            tag == DW_TAG_type_unit) {

            resetsrcfiles(dbg,sf);
            printf(    "<%3d> source file           : \"%s\"\n",level,name);
            print_comp_dir(dbg,print_me,level,sf);
        }
    } else {				// if it is an datum of smaller granularity, just print the tagname, and die name
        printf("<%d> tag: %d %s  name: \"%s\"\n",level,tag,tagname,name);
    }
    if(!localname) {
        dwarf_dealloc(dbg,name,DW_DLA_STRING);
    }
}