markgc.c

   1 /*
   2  * Copyright (c) 2007-2009 Apple Inc.  All Rights Reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23
  24 #include <stdlib.h>
  25 #include <unistd.h>
  26 #include <string.h>
  27 #import <stdio.h>
  28 #include <fcntl.h>
  29 #import <sys/stat.h>
  30 #import <mach-o/fat.h>
  31 #import <mach-o/arch.h>
  32 #import <mach-o/loader.h>
  33
  34 // from "objc-private.h"
  35 // masks for objc_image_info.flags
  36 #define OBJC_IMAGE_IS_REPLACEMENT (1<<0)
  37 #define OBJC_IMAGE_SUPPORTS_GC (1<<1)
  38 #define OBJC_IMAGE_REQUIRES_GC (1<<2)
  39 #define OBJC_IMAGE_OPTIMIZED_BY_DYLD (1<<3)
  40 #define OBJC_IMAGE_SUPPORTS_COMPACTION (1<<4)
  41
  42 typedef char bool;
  43 #define true 1
  44 #define false 0
  45
  46 bool debug;
  47 bool verbose;
  48 bool quiet;
  49 bool rrOnly;
  50 bool patch = true;
  51 bool unpatch = false;
  52
  53 struct gcinfo {
  54         bool hasObjC;
  55         bool hasInfo;
  56         uint32_t flags;
  57         char *arch;
  58 } GCInfo[4];
  59
  60 void dumpinfo(char *filename);
  61
  62 int Errors = 0;
  63 char *FileBase;
  64 size_t FileSize;
  65 const char *FileName;
  66
  67 int main(int argc, char *argv[]) {
  68     //NSAutoreleasePool *pool = [NSAutoreleasePool new];
  69     int i;
  70     //dumpinfo("/System/Library/Frameworks/AppKit.framework/AppKit");
  71     if (argc == 1) {
  72         printf("Usage: markgc [-v] [-r] [--] library_or_executable_image [image2 ...]\n");
  73         printf(" changes Garbage Collection readiness of named images, ignoring those without ObjC segments\n");
  74         printf("  -p        - patch RR binary to (apparently) support GC (default)\n");
  75         printf("  -u        - unpatch GC binary to RR only\n");
  76         printf("\nAuthor: blaine@apple.com\n");
  77         exit(0);
  78     }
  79     for (i = 1; i < argc; ++i) {
  80         if (!strcmp(argv[i], "-v")) {
  81             verbose = true;
  82             continue;
  83         }
  84         if (!strcmp(argv[i], "-d")) {
  85             debug = true;
  86             continue;
  87         }
  88         if (!strcmp(argv[i], "-q")) {
  89             quiet = true;
  90             continue;
  91         }
  92         if (!strcmp(argv[i], "-p")) {
  93             patch = true;
  94             continue;
  95         }
  96         if (!strcmp(argv[i], "-u")) {
  97             unpatch = true;
  98             patch = false;
  99             continue;
 100         }
 101         dumpinfo(argv[i]);
 102     }
 103     return Errors;
 104 }
 105
 106 struct imageInfo {
 107     uint32_t version;
 108     uint32_t flags;
 109 };
 110
 111 void patchFile(uint32_t value, size_t offset) {
 112     int fd = open(FileName, 1);
 113     off_t lresult = lseek(fd, offset, SEEK_SET);
 114     if (lresult == -1) {
 115         printf("couldn't seek to 0x%lx position on fd %d\n", offset, fd);
 116         ++Errors;
 117         return;
 118     }
 119     size_t wresult = write(fd, &value, 4);
 120     if (wresult != 4) {
 121         ++Errors;
 122         printf("didn't write new value\n");
 123     }
 124     else {
 125         printf("patched %s at offset 0x%lx\n", FileName, offset);
 126     }
 127     close(fd);
 128 }
 129
 130 uint32_t iiflags(struct imageInfo *ii, size_t size, bool needsFlip) {
 131     if (needsFlip) {
 132         ii->flags = OSSwapInt32(ii->flags);
 133     }
 134     if (debug) printf("flags->%x, nitems %lu\n", ii->flags, size/sizeof(struct imageInfo));
 135     uint32_t support_mask = (OBJC_IMAGE_SUPPORTS_GC | OBJC_IMAGE_SUPPORTS_COMPACTION);
 136     uint32_t flags = ii->flags;
 137     if (patch && (flags & support_mask) != support_mask) {
 138         //printf("will patch %s at offset %p\n", FileName, (char*)(&ii->flags) - FileBase);
 139         uint32_t newvalue = flags | support_mask;
 140         if (needsFlip) newvalue = OSSwapInt32(newvalue);
 141         patchFile(newvalue, (char*)(&ii->flags) - FileBase);
 142     }
 143     if (unpatch && (flags & support_mask) == support_mask) {
 144         uint32_t newvalue = flags & ~support_mask;
 145         if (needsFlip) newvalue = OSSwapInt32(newvalue);
 146         patchFile(newvalue, (char*)(&ii->flags) - FileBase);
 147     }
 148     for(int niis = 1; niis < size/sizeof(struct imageInfo); ++niis) {
 149         if (needsFlip) ii[niis].flags = OSSwapInt32(ii[niis].flags);
 150         if (ii[niis].flags != flags) {
 151             // uh, oh.
 152             printf("XXX ii[%d].flags %x != ii[0].flags %x\n", niis, ii[niis].flags, flags);
 153             ++Errors;
 154         }
 155     }
 156     return flags;
 157 }
 158
 159 void printflags(uint32_t flags) {
 160     if (flags & 0x1) printf(" F&C");
 161     if (flags & 0x2) printf(" GC");
 162     if (flags & 0x4) printf(" GC-only");
 163     else printf(" RR");
 164 }
 165
 166 /*
 167 void doimageinfo(struct imageInfo *ii, uint32_t size, bool needsFlip) {
 168     uint32_t flags = iiflags(ii, size, needsFlip);
 169     printflags(flags);
 170 }
 171 */
 172
 173
 174 void dosect32(void *start, struct section *sect, bool needsFlip, struct gcinfo *gcip) {
 175     if (debug) printf("section %s from segment %s\n", sect->sectname, sect->segname);
 176     if (strcmp(sect->segname, "__OBJC")) return;
 177     gcip->hasObjC = true;
 178     if (strcmp(sect->sectname, "__image_info")) return;
 179     gcip->hasInfo = true;
 180     if (needsFlip) {
 181         sect->offset = OSSwapInt32(sect->offset);
 182         sect->size = OSSwapInt32(sect->size);
 183     }
 184     // these guys aren't inline - they point elsewhere
 185     gcip->flags = iiflags(start + sect->offset, sect->size, needsFlip);
 186 }
 187
 188 void dosect64(void *start, struct section_64 *sect, bool needsFlip, struct gcinfo *gcip) {
 189     if (debug) printf("section %s from segment %s\n", sect->sectname, sect->segname);
 190     if (strcmp(sect->segname, "__OBJC") && strcmp(sect->segname, "__DATA")) return;
 191     if (strcmp(sect->sectname, "__image_info") && strncmp(sect->sectname, "__objc_imageinfo", 16)) return;
 192     gcip->hasObjC = true;
 193     gcip->hasInfo = true;
 194     if (needsFlip) {
 195         sect->offset = OSSwapInt32(sect->offset);
 196         sect->size = OSSwapInt64(sect->size);
 197     }
 198     // these guys aren't inline - they point elsewhere
 199     gcip->flags = iiflags(start + sect->offset, (size_t)sect->size, needsFlip);
 200 }
 201
 202 void doseg32(void *start, struct segment_command *seg, bool needsFlip, struct gcinfo *gcip) {
 203     // lets do sections
 204     if (needsFlip) {
 205         seg->fileoff = OSSwapInt32(seg->fileoff);
 206         seg->nsects = OSSwapInt32(seg->nsects);
 207     }
 208     if (debug) printf("segment name: %s, nsects %d\n", seg->segname, seg->nsects);
 209     if (seg->segname[0]) {
 210         if (strcmp("__OBJC", seg->segname)) return;
 211     }
 212     struct section *sect = (struct section *)(seg + 1);
 213     for (uint32_t nsects = 0; nsects < seg->nsects; ++nsects) {
 214         // sections directly follow
 215
 216         dosect32(start, sect + nsects, needsFlip, gcip);
 217     }
 218 }
 219 void doseg64(void *start, struct segment_command_64 *seg, bool needsFlip, struct gcinfo *gcip) {
 220     if (debug) printf("segment name: %s\n", seg->segname);
 221     if (seg->segname[0] && strcmp("__OBJC", seg->segname) && strcmp("__DATA", seg->segname)) return;
 222     gcip->hasObjC = true;
 223     // lets do sections
 224     if (needsFlip) {
 225         seg->fileoff = OSSwapInt64(seg->fileoff);
 226         seg->nsects = OSSwapInt32(seg->nsects);
 227     }
 228     struct section_64 *sect = (struct section_64 *)(seg + 1);
 229     for (uint32_t nsects = 0; nsects < seg->nsects; ++nsects) {
 230         // sections directly follow
 231
 232         dosect64(start, sect + nsects, needsFlip, gcip);
 233     }
 234 }
 235
 236 #if 0
 237 /*
 238  * A variable length string in a load command is represented by an lc_str
 239  * union.  The strings are stored just after the load command structure and
 240  * the offset is from the start of the load command structure.  The size
 241  * of the string is reflected in the cmdsize field of the load command.
 242  * Once again any padded bytes to bring the cmdsize field to a multiple
 243  * of 4 bytes must be zero.
 244  */
 245 union lc_str {
 246         uint32_t        offset; /* offset to the string */
 247 #ifndef __LP64__
 248         char            *ptr;   /* pointer to the string */
 249 #endif
 250 };
 251
 252 struct dylib {
 253     union lc_str  name;                 /* library's path name */
 254     uint32_t timestamp;                 /* library's build time stamp */
 255     uint32_t current_version;           /* library's current version number */
 256     uint32_t compatibility_version;     /* library's compatibility vers number*/
 257 };
 258
 259  * A dynamically linked shared library (filetype == MH_DYLIB in the mach header)
 260  * contains a dylib_command (cmd == LC_ID_DYLIB) to identify the library.
 261  * An object that uses a dynamically linked shared library also contains a
 262  * dylib_command (cmd == LC_LOAD_DYLIB, LC_LOAD_WEAK_DYLIB, or
 263  * LC_REEXPORT_DYLIB) for each library it uses.
 264
 265 struct dylib_command {
 266         uint32_t        cmd;            /* LC_ID_DYLIB, LC_LOAD_{,WEAK_}DYLIB,
 267                                            LC_REEXPORT_DYLIB */
 268         uint32_t        cmdsize;        /* includes pathname string */
 269         struct dylib    dylib;          /* the library identification */
 270 };
 271 #endif
 272
 273 void dodylib(void *start, struct dylib_command *dylibCmd, bool needsFlip) {
 274     if (!verbose) return;
 275     if (needsFlip) {
 276     }
 277     size_t count = dylibCmd->cmdsize - sizeof(struct dylib_command);
 278     //printf("offset is %d, count is %d\n", dylibCmd->dylib.name.offset, count);
 279     if (dylibCmd->dylib.name.offset > count) return;
 280     //printf("-->%.*s<---", count, ((void *)dylibCmd)+dylibCmd->dylib.name.offset);
 281     if (verbose) printf("load %s\n", ((char *)dylibCmd)+dylibCmd->dylib.name.offset);
 282 }
 283
 284 struct load_command *doloadcommand(void *start, struct load_command *lc, bool needsFlip, bool is32, struct gcinfo *gcip) {
 285     if (needsFlip) {
 286         lc->cmd = OSSwapInt32(lc->cmd);
 287         lc->cmdsize = OSSwapInt32(lc->cmdsize);
 288     }
 289
 290     switch(lc->cmd) {
 291     case LC_SEGMENT_64:
 292         if (debug) printf("...segment64\n");
 293         if (is32) printf("XXX we have a 64-bit segment in a 32-bit mach-o\n");
 294         doseg64(start, (struct segment_command_64 *)lc, needsFlip, gcip);
 295         break;
 296     case LC_SEGMENT:
 297         if (debug) printf("...segment32\n");
 298         doseg32(start, (struct segment_command *)lc, needsFlip, gcip);
 299         break;
 300     case LC_SYMTAB: if (debug) printf("...dynamic symtab\n"); break;
 301     case LC_DYSYMTAB: if (debug) printf("...symtab\n"); break;
 302     case LC_LOAD_DYLIB:
 303         dodylib(start, (struct dylib_command *)lc, needsFlip);
 304         break;
 305     case LC_SUB_UMBRELLA: if (debug) printf("...load subumbrella\n"); break;
 306     default:    if (debug) printf("cmd is %x\n", lc->cmd); break;
 307     }
 308
 309     return (struct load_command *)((void *)lc + lc->cmdsize);
 310 }
 311
 312 void doofile(void *start, size_t size, struct gcinfo *gcip) {
 313     struct mach_header *mh = (struct mach_header *)start;
 314     bool isFlipped = false;
 315     if (mh->magic == MH_CIGAM || mh->magic == MH_CIGAM_64) {
 316         if (debug) printf("(flipping)\n");
 317         mh->magic = OSSwapInt32(mh->magic);
 318         mh->cputype = OSSwapInt32(mh->cputype);
 319         mh->cpusubtype = OSSwapInt32(mh->cpusubtype);
 320         mh->filetype = OSSwapInt32(mh->filetype);
 321         mh->ncmds = OSSwapInt32(mh->ncmds);
 322         mh->sizeofcmds = OSSwapInt32(mh->sizeofcmds);
 323         mh->flags = OSSwapInt32(mh->flags);
 324         isFlipped = true;
 325     }
 326     if (rrOnly && mh->filetype != MH_DYLIB) return; // ignore executables
 327     NXArchInfo *info = (NXArchInfo *)NXGetArchInfoFromCpuType(mh->cputype, mh->cpusubtype);
 328     //printf("%s:", info->description);
 329     gcip->arch = (char *)info->description;
 330     //if (debug) printf("...description is %s\n", info->description);
 331     bool is32 = !(mh->cputype & CPU_ARCH_ABI64);
 332     if (debug) printf("is 32? %d\n", is32);
 333     if (debug) printf("filetype -> %d\n", mh->filetype);
 334     if (debug) printf("ncmds -> %d\n", mh->ncmds);
 335     struct load_command *lc = (is32 ? (struct load_command *)(mh + 1) : (struct load_command *)((struct mach_header_64 *)start + 1));
 336     int ncmds;
 337     for (ncmds = 0; ncmds < mh->ncmds; ++ncmds) {
 338         lc = doloadcommand(start, lc, isFlipped, is32, gcip);
 339     }
 340     //printf("\n");
 341 }
 342
 343 void initGCInfo() {
 344     bzero((void *)GCInfo, sizeof(GCInfo));
 345 }
 346
 347 void printGCInfo(char *filename) {
 348     if (!GCInfo[0].hasObjC) return; // don't bother
 349     // verify that flags are all the same
 350     uint32_t flags = GCInfo[0].flags;
 351     bool allSame = true;
 352     for (int i = 1; i < 4 && GCInfo[i].arch; ++i) {
 353         if (flags != GCInfo[i].flags) {
 354             allSame = false;
 355         }
 356     }
 357     if (rrOnly) {
 358         if (allSame && (flags & 0x2))
 359             return;
 360         printf("*** not all GC in %s:\n", filename);
 361     }
 362     if (allSame && !verbose) {
 363         printf("%s:", filename);
 364         printflags(flags);
 365         printf("\n");
 366     }
 367     else {
 368         printf("%s:\n", filename);
 369         for (int i = 0; i < 4 && GCInfo[i].arch; ++i) {
 370             printf("%s:", GCInfo[i].arch);
 371             printflags(GCInfo[i].flags);
 372             printf("\n");
 373         }
 374         printf("\n");
 375     }
 376 }
 377
 378 void dofat(void *start) {
 379     struct fat_header *fh = start;
 380     bool needsFlip = false;
 381     if (fh->magic == FAT_CIGAM) {
 382         fh->nfat_arch = OSSwapInt32(fh->nfat_arch);
 383         needsFlip = true;
 384     }
 385     if (debug) printf("%d architectures\n", fh->nfat_arch);
 386     int narchs;
 387     struct fat_arch *arch_ptr = (struct fat_arch *)(fh + 1);
 388     for (narchs = 0; narchs < fh->nfat_arch; ++narchs) {
 389         if (debug) printf("doing arch %d\n", narchs);
 390         if (needsFlip) {
 391             arch_ptr->offset = OSSwapInt32(arch_ptr->offset);
 392             arch_ptr->size = OSSwapInt32(arch_ptr->size);
 393         }
 394         doofile(start+arch_ptr->offset, arch_ptr->size, &GCInfo[narchs]);
 395         arch_ptr++;
 396     }
 397 }
 398
 399 bool openFile(const char *filename) {
 400     FileName = filename;
 401     // get size
 402     struct stat statb;
 403     int fd = open(filename, 0);
 404     if (fd < 0) {
 405         printf("couldn't open %s for reading\n", filename);
 406         return false;
 407     }
 408     int osresult = fstat(fd, &statb);
 409     if (osresult != 0) {
 410         printf("couldn't get size of %s\n", filename);
 411         close(fd);
 412         return false;
 413     }
 414     FileSize = (size_t)statb.st_size;
 415     FileBase = malloc(FileSize);
 416     if (!FileBase) {
 417         printf("couldn't malloc %lu bytes\n", FileSize);
 418         close(fd);
 419         return false;
 420     }
 421     off_t readsize = read(fd, FileBase, FileSize);
 422     if (readsize != FileSize) {
 423         printf("read %ld bytes, wanted %ld\n", (size_t)readsize, FileSize);
 424         close(fd);
 425         return false;
 426     }
 427     close(fd);
 428     return true;
 429 }
 430
 431 void closeFile() {
 432     free(FileBase);
 433 }
 434
 435 void dumpinfo(char *filename) {
 436     initGCInfo();
 437     if (!openFile(filename)) exit(1);
 438     struct fat_header *fh = (struct fat_header *)FileBase;
 439     if (fh->magic == FAT_MAGIC || fh->magic == FAT_CIGAM) {
 440         dofat((void *)FileBase);
 441         //printGCInfo(filename);
 442     }
 443     else if (fh->magic == MH_MAGIC || fh->magic == MH_CIGAM || fh->magic == MH_MAGIC_64 || fh->magic == MH_CIGAM_64) {
 444         doofile((void *)FileBase, FileSize, &GCInfo[0]);
 445         //printGCInfo(filename);
 446     }
 447     else if (!quiet) {
 448         printf("don't understand %s!\n", filename);
 449     }
 450     closeFile();
 451  }
 452