/* $NetBSD: crunchide.c,v 1.8 1997/11/01 06:51:45 lukem Exp $ */ /* * Copyright (c) 1997 Christopher G. Demetriou. All rights reserved. * Copyright (c) 1994 University of Maryland * All Rights Reserved. * * Permission to use, copy, modify, distribute, and sell this software and its * documentation for any purpose is hereby granted without fee, provided that * the above copyright notice appear in all copies and that both that * copyright notice and this permission notice appear in supporting * documentation, and that the name of U.M. not be used in advertising or * publicity pertaining to distribution of the software without specific, * written prior permission. U.M. makes no representations about the * suitability of this software for any purpose. It is provided "as is" * without express or implied warranty. * * U.M. DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL U.M. * BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. * * Author: James da Silva, Systems Design and Analysis Group * Computer Science Department * University of Maryland at College Park */ /* * crunchide.c - tiptoes through an a.out symbol table, hiding all defined * global symbols. Allows the user to supply a "keep list" of symbols * that are not to be hidden. This program relies on the use of the * linker's -dc flag to actually put global bss data into the file's * bss segment (rather than leaving it as undefined "common" data). * * The point of all this is to allow multiple programs to be linked * together without getting multiple-defined errors. * * For example, consider a program "foo.c". It can be linked with a * small stub routine, called "foostub.c", eg: * int foo_main(int argc, char **argv){ return main(argc, argv); } * like so: * cc -c foo.c foostub.c * ld -dc -r foo.o foostub.o -o foo.combined.o * crunchide -k _foo_main foo.combined.o * at this point, foo.combined.o can be linked with another program * and invoked with "foo_main(argc, argv)". foo's main() and any * other globals are hidden and will not conflict with other symbols. * * TODO: * - resolve the theoretical hanging reloc problem (see check_reloc() * below). I have yet to see this problem actually occur in any real * program. In what cases will gcc/gas generate code that needs a * relative reloc from a global symbol, other than PIC? The * solution is to not hide the symbol from the linker in this case, * but to generate some random name for it so that it doesn't link * with anything but holds the place for the reloc. * - arrange that all the BSS segments start at the same address, so * that the final crunched binary BSS size is the max of all the * component programs' BSS sizes, rather than their sum. */ #include #ifndef lint __RCSID("$NetBSD: crunchide.c,v 1.8 1997/11/01 06:51:45 lukem Exp $"); #endif #include #include #include #include #include #include #include #include #include #include "extern.h" char *pname = "crunchide"; void usage(void); void add_to_keep_list(char *symbol); void add_file_to_keep_list(char *filename); int hide_syms(const char *filename); int verbose; int main __P((int, char *[])); int main(argc, argv) int argc; char **argv; { int ch, errors; if(argc > 0) pname = argv[0]; while ((ch = getopt(argc, argv, "k:f:v")) != -1) switch(ch) { case 'k': add_to_keep_list(optarg); break; case 'f': add_file_to_keep_list(optarg); break; case 'v': verbose = 1; break; default: usage(); } argc -= optind; argv += optind; if(argc == 0) usage(); errors = 0; while(argc) { if (hide_syms(*argv)) errors = 1; argc--, argv++; } return errors; } void usage(void) { fprintf(stderr, "Usage: %s [-k ] [-f ] ...\n", pname); exit(1); } /* ---------------------------- */ struct keep { struct keep *next; char *sym; } *keep_list; void add_to_keep_list(char *symbol) { struct keep *newp, *prevp, *curp; int cmp; cmp = 0; for(curp = keep_list, prevp = NULL; curp; prevp = curp, curp = curp->next) if((cmp = strcmp(symbol, curp->sym)) <= 0) break; if(curp && cmp == 0) return; /* already in table */ newp = (struct keep *) malloc(sizeof(struct keep)); if(newp) newp->sym = strdup(symbol); if(newp == NULL || newp->sym == NULL) { fprintf(stderr, "%s: out of memory for keep list\n", pname); exit(1); } newp->next = curp; if(prevp) prevp->next = newp; else keep_list = newp; } int in_keep_list(const char *symbol) { struct keep *curp; int cmp; cmp = 0; for(curp = keep_list; curp; curp = curp->next) if((cmp = strcmp(symbol, curp->sym)) <= 0) break; return curp && cmp == 0; } void add_file_to_keep_list(char *filename) { FILE *keepf; char symbol[1024]; int len; if((keepf = fopen(filename, "r")) == NULL) { perror(filename); usage(); } while(fgets(symbol, 1024, keepf)) { len = strlen(symbol); if(len && symbol[len-1] == '\n') symbol[len-1] = '\0'; add_to_keep_list(symbol); } fclose(keepf); } /* ---------------------------- */ struct { const char *name; int (*check)(int, const char *); /* 1 if match, zero if not */ int (*hide)(int, const char *); /* non-zero if error */ } exec_formats[] = { #ifdef NLIST_AOUT { "a.out", check_aout, hide_aout, }, #endif #ifdef NLIST_ECOFF { "ECOFF", check_ecoff, hide_ecoff, }, #endif #ifdef NLIST_ELF32 { "ELF32", check_elf32, hide_elf32, }, #endif #ifdef NLIST_ELF64 { "ELF64", check_elf64, hide_elf64, }, #endif }; int hide_syms(const char *filename) { int fd, i, n, rv; fd = open(filename, O_RDWR, 0); if (fd == -1) { perror(filename); return 1; } rv = 0; n = sizeof exec_formats / sizeof exec_formats[0]; for (i = 0; i < n; i++) { if (lseek(fd, 0, SEEK_SET) != 0) { perror(filename); goto err; } if ((*exec_formats[i].check)(fd, filename) != 0) break; } if (i == n) { fprintf(stderr, "%s: unknown executable format\n", filename); goto err; } if (verbose) fprintf(stderr, "%s is an %s binary\n", filename, exec_formats[i].name); if (lseek(fd, 0, SEEK_SET) != 0) { perror(filename); goto err; } rv = (*exec_formats[i].hide)(fd, filename); out: close (fd); return (rv); err: rv = 1; goto out; }