/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright (c) 1995, 2010, Oracle and/or its affiliates. All rights reserved.
 */

/*
 * pcom: Print Comment
 *
 * This program demonstrates the use of the libelf interface to
 * read an ELF file.  pcom will open an ELF file using
 * elf_begin(ELF_C_READ) and examine search the ELF file
 * for a .comment section.  If a .comment section is found it's
 * contents will be displayed on stdout.
 */

#include <stdio.h>
#include <libelf.h>
#include <gelf.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>


static const char       *CommentStr = ".comment";

static void
print_comment(Elf *elf, const char *file)
{
        Elf_Scn         *scn = NULL;
        GElf_Shdr       shdr;
        Elf_Data        *data;
        size_t          shstrndx;


        (void) printf("%s .comment:\n", file);

        if (elf_getshdrstrndx(elf, &shstrndx) == -1) {
                (void) fprintf(stderr, "%s: elf_getshdrstrndx() failed: %s\n",
                    file, elf_errmsg(0));
                return;
        }

        while ((scn = elf_nextscn(elf, scn)) != NULL) {
                /*
                 * Do a string compare to examine each section header
                 * to see if it is a ".comment" section.  If it is then
                 * this is the section we want to process.
                 */
                if (gelf_getshdr(scn, &shdr) == NULL) {
                        (void) fprintf(stderr, "%s: elf_getshdr() failed: %s\n",
                            file, elf_errmsg(0));
                        return;
                }
                if (strcmp(CommentStr, elf_strptr(elf, shstrndx,
                    shdr.sh_name)) == 0) {
                        int     i;
                        char    *ptr;

                        /*
                         * Get the data associated with the .comment
                         * section.
                         */
                        if ((data = elf_getdata(scn, NULL)) == NULL) {
                                (void) fprintf(stderr,
                                    "%s: elf_getdata() failed: %s\n",
                                    file, elf_errmsg(0));
                                return;
                        }

                        /*
                         * Data in a .comment section is a list of 'null'
                         * terminated strings.  The following will print
                         * one string per line.
                         */
                        for (i = 0, ptr = (char *)data->d_buf;
                            i < data->d_size; i++)
                                if (ptr[i]) {
                                        (void) puts(&ptr[i]);
                                        i += strlen(&ptr[i]);
                                }
                        (void) putchar('\n');
                }
        }

}

static void
process_elf(Elf *elf, char *file, int fd, int member)
{
        Elf_Cmd cmd;
        Elf     *_elf;

        switch (elf_kind(elf)) {
        case ELF_K_ELF:
                /*
                 * This is an ELF file, now attempt to find it's
                 * .comment section and to display it.
                 */
                print_comment(elf, file);
                break;
        case ELF_K_AR:
                /*
                 * Archives contain multiple ELF files, which can each
                 * in turn be examined with libelf.
                 *
                 * The below loop will iterate over each member of the
                 * archive and recursively call process_elf().
                 */
                cmd = ELF_C_READ;
                while ((_elf = elf_begin(fd, cmd, elf)) != NULL) {
                        Elf_Arhdr       *arhdr;
                        char            buffer[1024];

                        arhdr = elf_getarhdr(_elf);

                        /*
                         * Build up file names based off of
                         * 'archivename(membername)'.
                         */
                        (void) sprintf(buffer, "%s(%s)", file, arhdr->ar_name);

                        /*
                         * Recursively process the ELF members.
                         */
                        process_elf(_elf, buffer, fd, 1);
                        cmd = elf_next(_elf);
                        (void) elf_end(_elf);
                }
                break;
        default:
                if (!member)
                        (void) fprintf(stderr,
                            "%s: unexpected elf_kind(): 0x%x\n",
                            file, elf_kind(elf));
                return;
        }
}

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

        if (argc < 2) {
                (void) printf("usage: %s elf_file ...\n", argv[0]);
                return (1);
        }

        /*
         * Initialize the elf library, must be called before elf_begin()
         * can be called.
         */
        if (elf_version(EV_CURRENT) == EV_NONE) {
                (void) fprintf(stderr,
                    "elf_version() failed: %s\n", elf_errmsg(0));
                return (1);
        }

        for (i = 1; i < argc; i++) {
                int     fd;
                Elf     *elf;
                char    *elf_fname;

                elf_fname = argv[i];
                if ((fd = open(elf_fname, O_RDONLY)) == -1) {
                        perror("open");
                        continue;
                }

                /*
                 * Attempt to open an Elf descriptor Read/Write
                 * for each file.
                 */
                if ((elf = elf_begin(fd, ELF_C_READ, 0)) == NULL) {
                        (void) fprintf(stderr, "elf_begin() failed: %s\n",
                            elf_errmsg(0));
                        (void) close(fd);
                        continue;
                }

                /*
                 * Process each elf descriptor.
                 */
                process_elf(elf, elf_fname, fd, 0);
                (void) elf_end(elf);
                (void) close(fd);
        }

        return (0);
}