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      1 /* $NetBSD: exec_aout.c,v 1.12 2009/08/20 17:40:26 he Exp $ */
      2 
      3 /*
      4  * Copyright (c) 1997 Christopher G. Demetriou.  All rights reserved.
      5  * Copyright (c) 1994 University of Maryland
      6  * All Rights Reserved.
      7  *
      8  * Permission to use, copy, modify, distribute, and sell this software and its
      9  * documentation for any purpose is hereby granted without fee, provided that
     10  * the above copyright notice appear in all copies and that both that
     11  * copyright notice and this permission notice appear in supporting
     12  * documentation, and that the name of U.M. not be used in advertising or
     13  * publicity pertaining to distribution of the software without specific,
     14  * written prior permission.  U.M. makes no representations about the
     15  * suitability of this software for any purpose.  It is provided "as is"
     16  * without express or implied warranty.
     17  *
     18  * U.M. DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL
     19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL U.M.
     20  * BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
     21  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
     22  * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
     23  * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
     24  *
     25  * Author: James da Silva, Systems Design and Analysis Group
     26  *			   Computer Science Department
     27  *			   University of Maryland at College Park
     28  */
     29 
     30 #include <sys/cdefs.h>
     31 #ifndef lint
     32 __RCSID("$NetBSD: exec_aout.c,v 1.12 2009/08/20 17:40:26 he Exp $");
     33 #endif
     34 
     35 #include <unistd.h>
     36 #include <stdio.h>
     37 #include <stdlib.h>
     38 #include <string.h>
     39 #include <errno.h>
     40 #include <sys/types.h>
     41 #include <sys/stat.h>
     42 
     43 #include "extern.h"
     44 
     45 #if defined(NLIST_AOUT)
     46 
     47 #include <a.out.h>
     48 #include <sys/exec_aout.h>
     49 
     50 int nsyms, ntextrel, ndatarel;
     51 struct exec *hdrp;
     52 char *aoutdata, *strbase;
     53 struct relocation_info *textrel, *datarel;
     54 struct nlist *symbase;
     55 
     56 
     57 #define SYMSTR(sp)	(&strbase[(sp)->n_un.n_strx])
     58 
     59 /* is the symbol a global symbol defined in the current file? */
     60 #define IS_GLOBAL_DEFINED(sp) \
     61                   (((sp)->n_type & N_EXT) && ((sp)->n_type & N_TYPE) != N_UNDF)
     62 
     63 #ifdef __sparc__
     64 /* is the relocation entry dependent on a symbol? */
     65 #define IS_SYMBOL_RELOC(rp)   \
     66 	((rp)->r_extern || \
     67 	((rp)->r_type >= RELOC_BASE10 && (rp)->r_type <= RELOC_BASE22) || \
     68 	(rp)->r_type == RELOC_JMP_TBL)
     69 #else
     70 /* is the relocation entry dependent on a symbol? */
     71 #define IS_SYMBOL_RELOC(rp)   \
     72                   ((rp)->r_extern||(rp)->r_baserel||(rp)->r_jmptable)
     73 #endif
     74 
     75 static void check_reloc(const char *filename, struct relocation_info *relp);
     76 
     77 int check_aout(int inf, const char *filename)
     78 {
     79     struct stat infstat;
     80     struct exec eh;
     81 
     82     /*
     83      * check the header to make sure it's an a.out-format file.
     84      */
     85 
     86     if(fstat(inf, &infstat) == -1)
     87 	return 0;
     88     if(infstat.st_size < (ssize_t)sizeof eh)
     89 	return 0;
     90     if(read(inf, &eh, sizeof eh) != sizeof eh)
     91 	return 0;
     92 
     93     if(N_BADMAG(eh))
     94 	return 0;
     95 
     96     return 1;
     97 }
     98 
     99 int hide_aout(int inf, const char *filename)
    100 {
    101     struct stat infstat;
    102     struct relocation_info *relp;
    103     struct nlist *symp;
    104     int rc;
    105 
    106     /*
    107      * do some error checking.
    108      */
    109 
    110     if(fstat(inf, &infstat) == -1) {
    111 	perror(filename);
    112 	return 1;
    113     }
    114 
    115     /*
    116      * Read the entire file into memory.  XXX - Really, we only need to
    117      * read the header and from TRELOFF to the end of the file.
    118      */
    119 
    120     if((aoutdata = (char *) malloc(infstat.st_size)) == NULL) {
    121 	fprintf(stderr, "%s: too big to read into memory\n", filename);
    122 	return 1;
    123     }
    124 
    125     if((rc = read(inf, aoutdata, infstat.st_size)) < infstat.st_size) {
    126 	fprintf(stderr, "%s: read error: %s\n", filename,
    127 		rc == -1? strerror(errno) : "short read");
    128 	return 1;
    129     }
    130 
    131     /*
    132      * Calculate offsets and sizes from the header.
    133      */
    134 
    135     hdrp = (struct exec *) aoutdata;
    136 
    137 #ifdef __FreeBSD__
    138     textrel = (struct relocation_info *) (aoutdata + N_RELOFF(*hdrp));
    139     datarel = (struct relocation_info *) (aoutdata + N_RELOFF(*hdrp) +
    140 					  hdrp->a_trsize);
    141 #else
    142     textrel = (struct relocation_info *) (aoutdata + N_TRELOFF(*hdrp));
    143     datarel = (struct relocation_info *) (aoutdata + N_DRELOFF(*hdrp));
    144 #endif
    145     symbase = (struct nlist *)		 (aoutdata + N_SYMOFF(*hdrp));
    146     strbase = (char *) 			 (aoutdata + N_STROFF(*hdrp));
    147 
    148     ntextrel = hdrp->a_trsize / sizeof(struct relocation_info);
    149     ndatarel = hdrp->a_drsize / sizeof(struct relocation_info);
    150     nsyms    = hdrp->a_syms   / sizeof(struct nlist);
    151 
    152     /*
    153      * Zap the type field of all globally-defined symbols.  The linker will
    154      * subsequently ignore these entries.  Don't zap any symbols in the
    155      * keep list.
    156      */
    157 
    158     for(symp = symbase; symp < symbase + nsyms; symp++) {
    159 	if(!IS_GLOBAL_DEFINED(symp))		/* keep undefined syms */
    160 	    continue;
    161 
    162 	/* keep (C) symbols which are on the keep list */
    163 	if(SYMSTR(symp)[0] == '_' && in_keep_list(SYMSTR(symp) + 1))
    164 	    continue;
    165 
    166 	symp->n_type = 0;
    167     }
    168 
    169     /*
    170      * Check whether the relocation entries reference any symbols that we
    171      * just zapped.  I don't know whether ld can handle this case, but I
    172      * haven't encountered it yet.  These checks are here so that the program
    173      * doesn't fail silently should such symbols be encountered.
    174      */
    175 
    176     for(relp = textrel; relp < textrel + ntextrel; relp++)
    177 	check_reloc(filename, relp);
    178     for(relp = datarel; relp < datarel + ndatarel; relp++)
    179 	check_reloc(filename, relp);
    180 
    181     /*
    182      * Write the .o file back out to disk.  XXX - Really, we only need to
    183      * write the symbol table entries back out.
    184      */
    185     lseek(inf, 0, SEEK_SET);
    186     if((rc = write(inf, aoutdata, infstat.st_size)) < infstat.st_size) {
    187 	fprintf(stderr, "%s: write error: %s\n", filename,
    188 		rc == -1? strerror(errno) : "short write");
    189 	return 1;
    190     }
    191 
    192     return 0;
    193 }
    194 
    195 
    196 static void check_reloc(const char *filename, struct relocation_info *relp)
    197 {
    198     /* bail out if we zapped a symbol that is needed */
    199     if(IS_SYMBOL_RELOC(relp) && symbase[relp->r_symbolnum].n_type == 0) {
    200 	fprintf(stderr,
    201 		"%s: oops, have hanging relocation for %s: bailing out!\n",
    202 		filename, SYMSTR(&symbase[relp->r_symbolnum]));
    203 	exit(1);
    204     }
    205 }
    206 
    207 #endif /* defined(NLIST_AOUT) */
    208