kernel debug: priv can be NULL early on

[minix.git] / lib / libelf / libelf_ar.c

/*-
 * Copyright (c) 2006,2008,2010 Joseph Koshy
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS `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 THE AUTHOR OR CONTRIBUTORS 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.
 */

#include <sys/cdefs.h>

#include <assert.h>
#include <ctype.h>
#include <libelf.h>
#include <stdlib.h>
#include <string.h>

#include "_libelf.h"
#include "_libelf_ar.h"

LIBELF_VCSID("$Id$");

#define LIBELF_NALLOC_SIZE      16

/*
 * `ar' archive handling.
 *
 * `ar' archives start with signature `ARMAG'.  Each archive member is
 * preceded by a header containing meta-data for the member.  This
 * header is described in <ar.h> (struct ar_hdr).  The header always
 * starts on an even address.  File data is padded with "\n"
 * characters to keep this invariant.
 *
 * Special considerations for `ar' archives:
 *
 * There are two variants of the `ar' archive format: traditional BSD
 * and SVR4.  These differ in the way long file names are treated, and
 * in the layout of the archive symbol table.
 *
 * The `ar' header only has space for a 16 character file name.
 *
 * In the SVR4 format, file names are terminated with a '/', so this
 * effectively leaves 15 characters for the actual file name.  Longer
 * file names stored in a separate 'string table' and referenced
 * indirectly from the name field.  The string table itself appears as
 * an archive member with name "// ".  An `indirect' file name in an
 * `ar' header matches the pattern "/[0-9]*". The digits form a
 * decimal number that corresponds to a byte offset into the string
 * table where the actual file name of the object starts.  Strings in
 * the string table are padded to start on even addresses.
 *
 * In the BSD format, file names can be upto 16 characters.  File
 * names shorter than 16 characters are padded to 16 characters using
 * (ASCII) space characters.  File names with embedded spaces and file
 * names longer than 16 characters are stored immediately after the
 * archive header and the name field set to a special indirect name
 * matching the pattern "#1/[0-9]+".  The digits form a decimal number
 * that corresponds to the actual length of the file name following
 * the archive header.  The content of the archive member immediately
 * follows the file name, and the size field of the archive member
 * holds the sum of the sizes of the member and of the appended file
 * name.
 *
 * Archives may also have a symbol table (see ranlib(1)), mapping
 * program symbols to object files inside the archive.
 *
 * In the SVR4 format, a symbol table uses a file name of "/ " in its
 * archive header.  The symbol table is structured as:
 *  - a 4-byte count of entries stored as a binary value, MSB first
 *  - 'n' 4-byte offsets, stored as binary values, MSB first
 *  - 'n' NUL-terminated strings, for ELF symbol names, stored unpadded.
 *
 * In the BSD format, the symbol table uses a file name of "__.SYMDEF".
 * It is structured as two parts:
 *  - The first part is an array of "ranlib" structures preceded by
 *    the size of the array in bytes.  Each "ranlib" structure
 *    describes one symbol.  Each structure contains an offset into
 *    the string table for the symbol name, and a file offset into the
 *    archive for the member defining the symbol.
 *  - The second part is a string table containing NUL-terminated
 *    strings, preceded by the size of the string table in bytes.
 *
 * If the symbol table and string table are is present in an archive
 * they must be the very first objects and in that order.
 */


/*
 * Retrieve an archive header descriptor.
 */

Elf_Arhdr *
_libelf_ar_gethdr(Elf *e)
{
        Elf *parent;
        char *namelen;
        Elf_Arhdr *eh;
        size_t n, nlen;
        struct ar_hdr *arh;

        if ((parent = e->e_parent) == NULL) {
                LIBELF_SET_ERROR(ARGUMENT, 0);
                return (NULL);
        }

        assert((e->e_flags & LIBELF_F_AR_HEADER) == 0);

        arh = (struct ar_hdr *) (uintptr_t) e->e_hdr.e_rawhdr;

        assert((uintptr_t) arh >= (uintptr_t) parent->e_rawfile + SARMAG);
        assert((uintptr_t) arh <= (uintptr_t) parent->e_rawfile +
            parent->e_rawsize - sizeof(struct ar_hdr));

        if ((eh = malloc(sizeof(Elf_Arhdr))) == NULL) {
                LIBELF_SET_ERROR(RESOURCE, 0);
                return (NULL);
        }

        e->e_hdr.e_arhdr = eh;
        e->e_flags |= LIBELF_F_AR_HEADER;

        eh->ar_name = eh->ar_rawname = NULL;

        if ((eh->ar_name = _libelf_ar_get_translated_name(arh, parent)) ==
            NULL)
                goto error;

        if (_libelf_ar_get_number(arh->ar_uid, sizeof(arh->ar_uid), 10,
            &n) == 0)
                goto error;
        eh->ar_uid = (uid_t) n;

        if (_libelf_ar_get_number(arh->ar_gid, sizeof(arh->ar_gid), 10,
            &n) == 0)
                goto error;
        eh->ar_gid = (gid_t) n;

        if (_libelf_ar_get_number(arh->ar_mode, sizeof(arh->ar_mode), 8,
            &n) == 0)
                goto error;
        eh->ar_mode = (mode_t) n;

        if (_libelf_ar_get_number(arh->ar_size, sizeof(arh->ar_size), 10,
            &n) == 0)
                goto error;

        /*
         * Get the true size of the member if extended naming is being used.
         */
        if (IS_EXTENDED_BSD_NAME(arh->ar_name)) {
                namelen = arh->ar_name +
                    LIBELF_AR_BSD_EXTENDED_NAME_PREFIX_SIZE;
                if (_libelf_ar_get_number(namelen, sizeof(arh->ar_name) -
                    LIBELF_AR_BSD_EXTENDED_NAME_PREFIX_SIZE, 10, &nlen) == 0)
                        goto error;
                n -= nlen;
        }

        eh->ar_size = n;

        if ((eh->ar_rawname = _libelf_ar_get_raw_name(arh)) == NULL)
                goto error;

        eh->ar_flags = 0;

        return (eh);

 error:
        if (eh) {
                if (eh->ar_name)
                        free(eh->ar_name);
                if (eh->ar_rawname)
                        free(eh->ar_rawname);
                free(eh);
        }

        e->e_flags &= ~LIBELF_F_AR_HEADER;
        e->e_hdr.e_rawhdr = (char *) arh;

        return (NULL);
}

Elf *
_libelf_ar_open_member(int fd, Elf_Cmd c, Elf *elf)
{
        Elf *e;
        char *member, *namelen;
        size_t nsz, sz;
        off_t next;
        struct ar_hdr *arh;

        assert(elf->e_kind == ELF_K_AR);

        next = elf->e_u.e_ar.e_next;

        /*
         * `next' is only set to zero by elf_next() when the last
         * member of an archive is processed.
         */
        if (next == (off_t) 0)
                return (NULL);

        assert((next & 1) == 0);

        arh = (struct ar_hdr *) (elf->e_rawfile + next);

        /*
         * Retrieve the size of the member.
         */
        if (_libelf_ar_get_number(arh->ar_size, sizeof(arh->ar_size), 10,
            &sz) == 0) {
                LIBELF_SET_ERROR(ARCHIVE, 0);
                return (NULL);
        }

        /*
         * Adjust the size field for members in BSD archives using
         * extended naming.
         */
        if (IS_EXTENDED_BSD_NAME(arh->ar_name)) {
                namelen = arh->ar_name +
                    LIBELF_AR_BSD_EXTENDED_NAME_PREFIX_SIZE;
                if (_libelf_ar_get_number(namelen, sizeof(arh->ar_name) -
                    LIBELF_AR_BSD_EXTENDED_NAME_PREFIX_SIZE, 10, &nsz) == 0) {
                        LIBELF_SET_ERROR(ARCHIVE, 0);
                        return (NULL);
                }

                member = (char *) (arh + 1) + nsz;
                sz -= nsz;
        } else
                member = (char *) (arh + 1);


        if ((e = elf_memory((char *) member, sz)) == NULL)
                return (NULL);

        e->e_fd = fd;
        e->e_cmd = c;
        e->e_hdr.e_rawhdr = (char *) arh;

        elf->e_u.e_ar.e_nchildren++;
        e->e_parent = elf;

        return (e);
}

/*
 * A BSD-style ar(1) symbol table has the following layout:
 *
 * - A count of bytes used by the following array of 'ranlib'
 *   structures, stored as a 'long'.
 * - An array of 'ranlib' structures.  Each array element is
 *   two 'long's in size.
 * - A count of bytes used for the following symbol table.
 * - The symbol table itself.
 */

/*
 * A helper macro to read in a 'long' value from the archive.  We use
 * memcpy() since the source pointer may be misaligned with respect to
 * the natural alignment for a C 'long'.
 */
#define GET_LONG(P, V)do {                              \
                memcpy(&(V), (P), sizeof(long));        \
                (P) += sizeof(long);                    \
        } while (0)

Elf_Arsym *
_libelf_ar_process_bsd_symtab(Elf *e, size_t *count)
{
        Elf_Arsym *symtab, *sym;
        unsigned char *end, *p, *p0, *s, *s0;
        const unsigned int entrysize = 2 * sizeof(long);
        long arraysize, fileoffset, n, nentries, stroffset, strtabsize;

        assert(e != NULL);
        assert(count != NULL);
        assert(e->e_u.e_ar.e_symtab == NULL);

        symtab = NULL;

        /*
         * The BSD symbol table always contains the count fields even
         * if there are no entries in it.
         */
        if (e->e_u.e_ar.e_rawsymtabsz < 2 * sizeof(long))
                goto symtaberror;

        p = p0 = (unsigned char *) e->e_u.e_ar.e_rawsymtab;
        end = p0 + e->e_u.e_ar.e_rawsymtabsz;

        /*
         * Retrieve the size of the array of ranlib descriptors and
         * check it for validity.
         */
        GET_LONG(p, arraysize);

        if (p0 + arraysize >= end || (arraysize % entrysize != 0))
                goto symtaberror;

        /*
         * Check the value of the string table size.
         */
        s = p + arraysize;
        GET_LONG(s, strtabsize);

        s0 = s;                 /* Start of string table. */
        if (s0 + strtabsize > end)
                goto symtaberror;

        nentries = arraysize / entrysize;

        /*
         * Allocate space for the returned Elf_Arsym array.
         */
        if ((symtab = malloc(sizeof(Elf_Arsym) * (nentries + 1))) == NULL) {
                LIBELF_SET_ERROR(RESOURCE, 0);
                return (NULL);
        }

        /* Read in symbol table entries. */
        for (n = 0, sym = symtab; n < nentries; n++, sym++) {
                GET_LONG(p, stroffset);
                GET_LONG(p, fileoffset);

                s = s0 + stroffset;

                if (s >= end)
                        goto symtaberror;

                sym->as_off = fileoffset;
                sym->as_hash = elf_hash((char *) s);
                sym->as_name = (char *) s;
        }

        /* Fill up the sentinel entry. */
        sym->as_name = NULL;
        sym->as_hash = ~0UL;
        sym->as_off = (off_t) 0;

        /* Remember the processed symbol table. */
        e->e_u.e_ar.e_symtab = symtab;

        *count = e->e_u.e_ar.e_symtabsz = nentries + 1;

        return (symtab);

symtaberror:
        if (symtab)
                free(symtab);
        LIBELF_SET_ERROR(ARCHIVE, 0);
        return (NULL);
}

/*
 * An SVR4-style ar(1) symbol table has the following layout:
 *
 * - The first 4 bytes are a binary count of the number of entries in the
 *   symbol table, stored MSB-first.
 * - Then there are 'n' 4-byte binary offsets, also stored MSB first.
 * - Following this, there are 'n' null-terminated strings.
 */

#define GET_WORD(P, V) do {                     \
                (V) = 0;                        \
                (V) = (P)[0]; (V) <<= 8;        \
                (V) += (P)[1]; (V) <<= 8;       \
                (V) += (P)[2]; (V) <<= 8;       \
                (V) += (P)[3];                  \
        } while (0)

#define INTSZ   4


Elf_Arsym *
_libelf_ar_process_svr4_symtab(Elf *e, size_t *count)
{
        size_t n, nentries, off;
        Elf_Arsym *symtab, *sym;
        unsigned char *p, *s, *end;

        assert(e != NULL);
        assert(count != NULL);
        assert(e->e_u.e_ar.e_symtab == NULL);

        symtab = NULL;

        if (e->e_u.e_ar.e_rawsymtabsz < INTSZ)
                goto symtaberror;

        p = (unsigned char *) e->e_u.e_ar.e_rawsymtab;
        end = p + e->e_u.e_ar.e_rawsymtabsz;

        GET_WORD(p, nentries);
        p += INTSZ;

        if (nentries == 0 || p + nentries * INTSZ >= end)
                goto symtaberror;

        /* Allocate space for a nentries + a sentinel. */
        if ((symtab = malloc(sizeof(Elf_Arsym) * (nentries+1))) == NULL) {
                LIBELF_SET_ERROR(RESOURCE, 0);
                return (NULL);
        }

        s = p + (nentries * INTSZ); /* start of the string table. */

        for (n = nentries, sym = symtab; n > 0; n--) {

                if (s >= end)
                        goto symtaberror;

                off = 0;

                GET_WORD(p, off);

                sym->as_off = off;
                sym->as_hash = elf_hash((char *) s);
                sym->as_name = (char *) s;

                p += INTSZ;
                sym++;

                for (; s < end && *s++ != '\0';) /* skip to next string */
                        ;
        }

        /* Fill up the sentinel entry. */
        sym->as_name = NULL;
        sym->as_hash = ~0UL;
        sym->as_off = (off_t) 0;

        *count = e->e_u.e_ar.e_symtabsz = nentries + 1;
        e->e_u.e_ar.e_symtab = symtab;

        return (symtab);

symtaberror:
        if (symtab)
                free(symtab);
        LIBELF_SET_ERROR(ARCHIVE, 0);
        return (NULL);
}