summaryrefslogtreecommitdiffstats
path: root/sources/patchelf/patchelf.cc
blob: e8b70b4afee3b915c11f29c3831931cb3ecb9f46 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
#include <string>
#include <vector>
#include <map>
#include <algorithm>

#include <stdlib.h>
#include <stdio.h>
#include <stdarg.h>
#include <assert.h>
#include <string.h>
#include <errno.h>

#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <limits.h>

#include "elf.h"

using namespace std;


#ifdef MIPSEL
/* The lemote fuloong 2f kernel defconfig sets a page size of 16KB */
const unsigned int pageSize = 4096*4;
#else
const unsigned int pageSize = 4096;
#endif


static bool debugMode = false;

static bool forceRPath = false;

static string fileName;


off_t fileSize, maxSize;
unsigned char * contents = 0;


#define ElfFileParams class Elf_Ehdr, class Elf_Phdr, class Elf_Shdr, class Elf_Addr, class Elf_Off, class Elf_Dyn
#define ElfFileParamNames Elf_Ehdr, Elf_Phdr, Elf_Shdr, Elf_Addr, Elf_Off, Elf_Dyn


template<ElfFileParams>
class ElfFile
{
    Elf_Ehdr * hdr;
    vector<Elf_Phdr> phdrs;
    vector<Elf_Shdr> shdrs;

    bool littleEndian;

    bool changed;

    bool isExecutable;

    typedef string SectionName;
    typedef map<SectionName, string> ReplacedSections;

    ReplacedSections replacedSections;

    string sectionNames; /* content of the .shstrtab section */

    /* Align on 4 or 8 bytes boundaries on 32- or 64-bit platforms
       respectively. */
    unsigned int sectionAlignment;

public:

    ElfFile() 
    {
        changed = false;
        sectionAlignment = sizeof(Elf_Off);
    }

    bool isChanged()
    {
        return changed;
    }
    
    void parse();

private:

    struct CompPhdr
    {
        ElfFile * elfFile;
        bool operator ()(const Elf_Phdr & x, const Elf_Phdr & y)
        {
            if (x.p_type == PT_PHDR) return true;
            if (y.p_type == PT_PHDR) return false;
            return elfFile->rdi(x.p_paddr) < elfFile->rdi(y.p_paddr);
        }
    };

    friend struct CompPhdr;

    void sortPhdrs();

    struct CompShdr 
    {
        ElfFile * elfFile;
        bool operator ()(const Elf_Shdr & x, const Elf_Shdr & y)
        {
            return elfFile->rdi(x.sh_offset) < elfFile->rdi(y.sh_offset);
        }
    };
    
    friend struct CompShdr;

    void sortShdrs();

    void shiftFile(unsigned int extraPages, Elf_Addr startPage);

    string getSectionName(const Elf_Shdr & shdr);

    Elf_Shdr & findSection(const SectionName & sectionName);
    
    Elf_Shdr * findSection2(const SectionName & sectionName);

    unsigned int findSection3(const SectionName & sectionName);

    string & replaceSection(const SectionName & sectionName,
        unsigned int size);

    void writeReplacedSections(Elf_Off & curOff,
        Elf_Addr startAddr, Elf_Off startOffset);
    
    void rewriteHeaders(Elf_Addr phdrAddress);

    void rewriteSectionsLibrary();
    
    void rewriteSectionsExecutable();

public:

    void rewriteSections();

    string getInterpreter();

    void setInterpreter(const string & newInterpreter);

    typedef enum { rpPrint, rpShrink, rpSet } RPathOp;

    void modifyRPath(RPathOp op, string newRPath);

private:
    
    /* Convert an integer in big or little endian representation (as
       specified by the ELF header) to this platform's integer
       representation. */
    template<class I>
    I rdi(I i);

    /* Convert back to the ELF representation. */
    template<class I>
    I wri(I & t, unsigned long long i) 
    {
        t = rdi((I) i);
        return i;
    }
};


/* !!! G++ creates broken code if this function is inlined, don't know
   why... */
template<ElfFileParams>
template<class I>
I ElfFile<ElfFileParamNames>::rdi(I i) 
{
    I r = 0;
    if (littleEndian) {
        for (unsigned int n = 0; n < sizeof(I); ++n) {
            r |= ((I) *(((unsigned char *) &i) + n)) << (n * 8);
        }
    } else {
        for (unsigned int n = 0; n < sizeof(I); ++n) {
            r |= ((I) *(((unsigned char *) &i) + n)) << ((sizeof(I) - n - 1) * 8);
        }
    }
    return r;
}


/* Ugly: used to erase DT_RUNPATH when using --force-rpath. */
#define DT_IGNORE       0x00726e67


static void debug(const char * format, ...)
{
    if (debugMode) {
        va_list ap;
        va_start(ap, format);
        vfprintf(stderr, format, ap);
        va_end(ap);
    }
}


static void error(string msg)
{
    if (errno) perror(msg.c_str()); else fprintf(stderr, "%s\n", msg.c_str());
    exit(1);
}


static void growFile(off_t newSize)
{
    if (newSize > maxSize) error("maximum file size exceeded");
    if (newSize <= fileSize) return;
    if (newSize > fileSize)
        memset(contents + fileSize, 0, newSize - fileSize);
    fileSize = newSize;
}


static void readFile(string fileName, mode_t * fileMode)
{
    struct stat st;
    if (stat(fileName.c_str(), &st) != 0) error("stat");
    fileSize = st.st_size;
    *fileMode = st.st_mode;
    maxSize = fileSize + 8 * 1024 * 1024;
    
    contents = (unsigned char *) malloc(fileSize + maxSize);
    if (!contents) abort();

    int fd = open(fileName.c_str(), O_RDONLY);
    if (fd == -1) error("open");

    if (read(fd, contents, fileSize) != fileSize) error("read");
    
    close(fd);
}


static void checkPointer(void * p, unsigned int size)
{
    unsigned char * q = (unsigned char *) p;
    assert(q >= contents && q + size <= contents + fileSize);
}


template<ElfFileParams>
void ElfFile<ElfFileParamNames>::parse()
{
    isExecutable = false;
    
    /* Check the ELF header for basic validity. */
    if (fileSize < (off_t) sizeof(Elf_Ehdr)) error("missing ELF header");

    hdr = (Elf_Ehdr *) contents;

    if (memcmp(hdr->e_ident, ELFMAG, SELFMAG) != 0)
        error("not an ELF executable");

    littleEndian = contents[EI_DATA] == ELFDATA2LSB;
    
    if (rdi(hdr->e_type) != ET_EXEC && rdi(hdr->e_type) != ET_DYN)
        error("wrong ELF type");

    if ((off_t) (rdi(hdr->e_phoff) + rdi(hdr->e_phnum) * rdi(hdr->e_phentsize)) > fileSize)
        error("missing program headers");
    
    if ((off_t) (rdi(hdr->e_shoff) + rdi(hdr->e_shnum) * rdi(hdr->e_shentsize)) > fileSize)
        error("missing section headers");

    if (rdi(hdr->e_phentsize) != sizeof(Elf_Phdr))
        error("program headers have wrong size");

    /* Copy the program and section headers. */
    for (int i = 0; i < rdi(hdr->e_phnum); ++i) {
        phdrs.push_back(* ((Elf_Phdr *) (contents + rdi(hdr->e_phoff)) + i));
        if (rdi(phdrs[i].p_type) == PT_INTERP) isExecutable = true;
    }
    
    for (int i = 0; i < rdi(hdr->e_shnum); ++i)
        shdrs.push_back(* ((Elf_Shdr *) (contents + rdi(hdr->e_shoff)) + i));

    /* Get the section header string table section (".shstrtab").  Its
       index in the section header table is given by e_shstrndx field
       of the ELF header. */
    unsigned int shstrtabIndex = rdi(hdr->e_shstrndx);
    assert(shstrtabIndex < shdrs.size());
    unsigned int shstrtabSize = rdi(shdrs[shstrtabIndex].sh_size);
    char * shstrtab = (char * ) contents + rdi(shdrs[shstrtabIndex].sh_offset);
    checkPointer(shstrtab, shstrtabSize);

    assert(shstrtabSize > 0);
    assert(shstrtab[shstrtabSize - 1] == 0);

    sectionNames = string(shstrtab, shstrtabSize);
}


template<ElfFileParams>
void ElfFile<ElfFileParamNames>::sortPhdrs()
{
    /* Sort the segments by offset. */
    CompPhdr comp;
    comp.elfFile = this;
    sort(phdrs.begin(), phdrs.end(), comp);
}


template<ElfFileParams>
void ElfFile<ElfFileParamNames>::sortShdrs()
{
    /* Translate sh_link mappings to section names, since sorting the
       sections will invalidate the sh_link fields. */
    map<SectionName, SectionName> linkage;
    for (unsigned int i = 1; i < rdi(hdr->e_shnum); ++i)
        if (rdi(shdrs[i].sh_link) != 0)
            linkage[getSectionName(shdrs[i])] = getSectionName(shdrs[rdi(shdrs[i].sh_link)]);

    /* Idem for sh_info on certain sections. */
    map<SectionName, SectionName> info;
    for (unsigned int i = 1; i < rdi(hdr->e_shnum); ++i)
        if (rdi(shdrs[i].sh_info) != 0 &&
            (rdi(shdrs[i].sh_type) == SHT_REL || rdi(shdrs[i].sh_type) == SHT_RELA))
            info[getSectionName(shdrs[i])] = getSectionName(shdrs[rdi(shdrs[i].sh_info)]);

    /* Idem for the index of the .shstrtab section in the ELF header. */
    SectionName shstrtabName = getSectionName(shdrs[rdi(hdr->e_shstrndx)]);
    
    /* Sort the sections by offset. */
    CompShdr comp;
    comp.elfFile = this;
    sort(shdrs.begin(), shdrs.end(), comp);

    /* Restore the sh_link mappings. */
    for (unsigned int i = 1; i < rdi(hdr->e_shnum); ++i)
        if (rdi(shdrs[i].sh_link) != 0)
            wri(shdrs[i].sh_link,
                findSection3(linkage[getSectionName(shdrs[i])]));

    /* And the st_info mappings. */
    for (unsigned int i = 1; i < rdi(hdr->e_shnum); ++i)
        if (rdi(shdrs[i].sh_info) != 0 &&
            (rdi(shdrs[i].sh_type) == SHT_REL || rdi(shdrs[i].sh_type) == SHT_RELA))
            wri(shdrs[i].sh_info,
                findSection3(info[getSectionName(shdrs[i])]));

    /* And the .shstrtab index. */
    wri(hdr->e_shstrndx, findSection3(shstrtabName));
}


static void writeFile(string fileName, mode_t fileMode)
{
    string fileName2 = fileName + "_patchelf_tmp";
    
    int fd = open(fileName2.c_str(),
        O_CREAT | O_TRUNC | O_WRONLY, 0700);
    if (fd == -1) error("open");

    if (write(fd, contents, fileSize) != fileSize) error("write");
    
    if (close(fd) != 0) error("close");

    if (chmod(fileName2.c_str(), fileMode) != 0) error("chmod");

    if (rename(fileName2.c_str(), fileName.c_str()) != 0) error("rename");
}


static unsigned int roundUp(unsigned int n, unsigned int m)
{
    return ((n - 1) / m + 1) * m;
}


template<ElfFileParams>
void ElfFile<ElfFileParamNames>::shiftFile(unsigned int extraPages, Elf_Addr startPage)
{
    /* Move the entire contents of the file `extraPages' pages
       further. */
    unsigned int oldSize = fileSize;
    unsigned int shift = extraPages * pageSize;
    growFile(fileSize + extraPages * pageSize);
    memmove(contents + extraPages * pageSize, contents, oldSize);
    memset(contents + sizeof(Elf_Ehdr), 0, shift - sizeof(Elf_Ehdr));

    /* Adjust the ELF header. */
    wri(hdr->e_phoff, sizeof(Elf_Ehdr));
    wri(hdr->e_shoff, rdi(hdr->e_shoff) + shift);
    
    /* Update the offsets in the section headers. */
    for (int i = 1; i < rdi(hdr->e_shnum); ++i)
        wri(shdrs[i].sh_offset, rdi(shdrs[i].sh_offset) + shift);
    
    /* Update the offsets in the program headers. */
    for (int i = 0; i < rdi(hdr->e_phnum); ++i) {
        wri(phdrs[i].p_offset, rdi(phdrs[i].p_offset) + shift);
        if (rdi(phdrs[i].p_align) != 0 &&
            (rdi(phdrs[i].p_vaddr) - rdi(phdrs[i].p_offset)) % rdi(phdrs[i].p_align) != 0) {
            debug("changing alignment of program header %d from %d to %d\n", i,
                rdi(phdrs[i].p_align), pageSize);
            wri(phdrs[i].p_align, pageSize);
        }
    }

    /* Add a segment that maps the new program/section headers and
       PT_INTERP segment into memory.  Otherwise glibc will choke. */
    phdrs.resize(rdi(hdr->e_phnum) + 1);
    wri(hdr->e_phnum, rdi(hdr->e_phnum) + 1);
    Elf_Phdr & phdr = phdrs[rdi(hdr->e_phnum) - 1];
    wri(phdr.p_type, PT_LOAD);
    wri(phdr.p_offset, 0);
    wri(phdr.p_vaddr, wri(phdr.p_paddr, startPage));
    wri(phdr.p_filesz, wri(phdr.p_memsz, shift)); 
    wri(phdr.p_flags, PF_R | PF_W);
    wri(phdr.p_align, pageSize);
}


template<ElfFileParams>
string ElfFile<ElfFileParamNames>::getSectionName(const Elf_Shdr & shdr)
{
    return string(sectionNames.c_str() + rdi(shdr.sh_name));
}


template<ElfFileParams>
Elf_Shdr & ElfFile<ElfFileParamNames>::findSection(const SectionName & sectionName)
{
    Elf_Shdr * shdr = findSection2(sectionName);
    if (!shdr)
        error("cannot find section " + sectionName);
    return *shdr;
}


template<ElfFileParams>
Elf_Shdr * ElfFile<ElfFileParamNames>::findSection2(const SectionName & sectionName)
{
    unsigned int i = findSection3(sectionName);
    return i ? &shdrs[i] : 0;
}


template<ElfFileParams>
unsigned int ElfFile<ElfFileParamNames>::findSection3(const SectionName & sectionName)
{
    for (unsigned int i = 1; i < rdi(hdr->e_shnum); ++i)
        if (getSectionName(shdrs[i]) == sectionName) return i;
    return 0;
}


template<ElfFileParams>
string & ElfFile<ElfFileParamNames>::replaceSection(const SectionName & sectionName,
    unsigned int size)
{
    ReplacedSections::iterator i = replacedSections.find(sectionName);
    string s;
    
    if (i != replacedSections.end()) {
        s = string(i->second);
    } else {
        Elf_Shdr & shdr = findSection(sectionName);
        s = string((char *) contents + rdi(shdr.sh_offset), rdi(shdr.sh_size));
    }
    
    s.resize(size);
    replacedSections[sectionName] = s;

    return replacedSections[sectionName];
}


template<ElfFileParams>
void ElfFile<ElfFileParamNames>::writeReplacedSections(Elf_Off & curOff,
    Elf_Addr startAddr, Elf_Off startOffset)
{
    /* Overwrite the old section contents with 'X's.  Do this
       *before* writing the new section contents (below) to prevent
       clobbering previously written new section contents. */
    for (ReplacedSections::iterator i = replacedSections.begin();
         i != replacedSections.end(); ++i)
    {
        string sectionName = i->first;
        Elf_Shdr & shdr = findSection(sectionName);
        memset(contents + rdi(shdr.sh_offset), 'X', rdi(shdr.sh_size));
    }
    
    for (ReplacedSections::iterator i = replacedSections.begin();
         i != replacedSections.end(); ++i)
    {
        string sectionName = i->first;
        Elf_Shdr & shdr = findSection(sectionName);
        debug("rewriting section `%s' from offset 0x%x (size %d) to offset 0x%x (size %d)\n",
            sectionName.c_str(), rdi(shdr.sh_offset), rdi(shdr.sh_size), curOff, i->second.size());

        memcpy(contents + curOff, (unsigned char *) i->second.c_str(),
            i->second.size());

        /* Update the section header for this section. */
        wri(shdr.sh_offset, curOff);
        wri(shdr.sh_addr, startAddr + (curOff - startOffset));
        wri(shdr.sh_size, i->second.size());
        wri(shdr.sh_addralign, sectionAlignment);

        /* If this is the .interp section, then the PT_INTERP segment
           must be sync'ed with it. */
        if (sectionName == ".interp") {
            for (unsigned int j = 0; j < phdrs.size(); ++j)
                if (rdi(phdrs[j].p_type) == PT_INTERP) {
                    phdrs[j].p_offset = shdr.sh_offset;
                    phdrs[j].p_vaddr = phdrs[j].p_paddr = shdr.sh_addr;
                    phdrs[j].p_filesz = phdrs[j].p_memsz = shdr.sh_size;
                }
        }

        /* If this is the .dynamic section, then the PT_DYNAMIC segment
           must be sync'ed with it. */
        if (sectionName == ".dynamic") {
            for (unsigned int j = 0; j < phdrs.size(); ++j)
                if (rdi(phdrs[j].p_type) == PT_DYNAMIC) {
                    phdrs[j].p_offset = shdr.sh_offset;
                    phdrs[j].p_vaddr = phdrs[j].p_paddr = shdr.sh_addr;
                    phdrs[j].p_filesz = phdrs[j].p_memsz = shdr.sh_size;
                }
        }

        curOff += roundUp(i->second.size(), sectionAlignment);
    }

    replacedSections.clear();
}


template<ElfFileParams>
void ElfFile<ElfFileParamNames>::rewriteSectionsLibrary()
{
    /* For dynamic libraries, we just place the replacement sections
       at the end of the file.  They're mapped into memory by a
       PT_LOAD segment located directly after the last virtual address
       page of other segments. */
    Elf_Addr startPage = 0;
    for (unsigned int i = 0; i < phdrs.size(); ++i) {
        Elf_Addr thisPage = roundUp(rdi(phdrs[i].p_vaddr) + rdi(phdrs[i].p_memsz), pageSize);
        if (thisPage > startPage) startPage = thisPage;
    }

    debug("last page is 0x%llx\n", (unsigned long long) startPage);


    /* Compute the total space needed for the replaced sections and
       the program headers. */
    off_t neededSpace = (phdrs.size() + 1) * sizeof(Elf_Phdr);
    for (ReplacedSections::iterator i = replacedSections.begin();
         i != replacedSections.end(); ++i)
        neededSpace += roundUp(i->second.size(), sectionAlignment);
    debug("needed space is %d\n", neededSpace);


    size_t startOffset = roundUp(fileSize, pageSize);

    growFile(startOffset + neededSpace);


    /* Even though this file is of type ET_DYN, it could actually be
       an executable.  For instance, Gold produces executables marked
       ET_DYN.  In that case we can still hit the kernel bug that
       necessitated rewriteSectionsExecutable().  However, such
       executables also tend to start at virtual address 0, so
       rewriteSectionsExecutable() won't work because it doesn't have
       any virtual address space to grow downwards into.  As a
       workaround, make sure that the virtual address of our new
       PT_LOAD segment relative to the first PT_LOAD segment is equal
       to its offset; otherwise we hit the kernel bug.  This may
       require creating a hole in the executable.  The bigger the size
       of the uninitialised data segment, the bigger the hole. */
    if (isExecutable) {
        if (startOffset >= startPage) {
            debug("shifting new PT_LOAD segment by %d bytes to work around a Linux kernel bug\n", startOffset - startPage);
        } else {
            size_t hole = startPage - startOffset;
            /* Print a warning, because the hole could be very big. */
            fprintf(stderr, "warning: working around a Linux kernel bug by creating a hole of %zu bytes in ā€˜%sā€™\n", hole, fileName.c_str());
            assert(hole % pageSize == 0);
            /* !!! We could create an actual hole in the file here,
               but it's probably not worth the effort. */
            growFile(fileSize + hole);
            startOffset += hole;
        }
        startPage = startOffset;
    }

    
    /* Add a segment that maps the replaced sections and program
       headers into memory. */
    phdrs.resize(rdi(hdr->e_phnum) + 1);
    wri(hdr->e_phnum, rdi(hdr->e_phnum) + 1);
    Elf_Phdr & phdr = phdrs[rdi(hdr->e_phnum) - 1];
    wri(phdr.p_type, PT_LOAD);
    wri(phdr.p_offset, startOffset);
    wri(phdr.p_vaddr, wri(phdr.p_paddr, startPage));
    wri(phdr.p_filesz, wri(phdr.p_memsz, neededSpace));
    wri(phdr.p_flags, PF_R | PF_W);
    wri(phdr.p_align, pageSize);


    /* Write out the replaced sections. */
    Elf_Off curOff = startOffset + phdrs.size() * sizeof(Elf_Phdr);
    writeReplacedSections(curOff, startPage, startOffset);
    assert((off_t) curOff == startOffset + neededSpace);


    /* Move the program header to the start of the new area. */
    wri(hdr->e_phoff, startOffset);

    rewriteHeaders(startPage);
}


template<ElfFileParams>
void ElfFile<ElfFileParamNames>::rewriteSectionsExecutable()
{
    /* Sort the sections by offset, otherwise we won't correctly find
       all the sections before the last replaced section. */
    sortShdrs();


    /* What is the index of the last replaced section? */
    unsigned int lastReplaced = 0;
    for (unsigned int i = 1; i < rdi(hdr->e_shnum); ++i) {
        string sectionName = getSectionName(shdrs[i]);
        if (replacedSections.find(sectionName) != replacedSections.end()) {
            debug("using replaced section `%s'\n", sectionName.c_str());
            lastReplaced = i;
        }
    }

    assert(lastReplaced != 0);

    debug("last replaced is %d\n", lastReplaced);
    
    /* Try to replace all sections before that, as far as possible.
       Stop when we reach an irreplacable section (such as one of type
       SHT_PROGBITS).  These cannot be moved in virtual address space
       since that would invalidate absolute references to them. */
    assert(lastReplaced + 1 < shdrs.size()); /* !!! I'm lazy. */
    size_t startOffset = rdi(shdrs[lastReplaced + 1].sh_offset);
    Elf_Addr startAddr = rdi(shdrs[lastReplaced + 1].sh_addr);
    string prevSection;
    for (unsigned int i = 1; i <= lastReplaced; ++i) {
        Elf_Shdr & shdr(shdrs[i]);
        string sectionName = getSectionName(shdr);
        debug("looking at section `%s'\n", sectionName.c_str());
        /* !!! Why do we stop after a .dynstr section? I can't
           remember! */
        if ((rdi(shdr.sh_type) == SHT_PROGBITS && sectionName != ".interp")
            || prevSection == ".dynstr")
        {
            startOffset = rdi(shdr.sh_offset);
            startAddr = rdi(shdr.sh_addr);
            lastReplaced = i - 1;
            break;
        } else {
            if (replacedSections.find(sectionName) == replacedSections.end()) {
                debug("replacing section `%s' which is in the way\n", sectionName.c_str());
                replaceSection(sectionName, rdi(shdr.sh_size));
            }
        }
        prevSection = sectionName;
    }

    debug("first reserved offset/addr is 0x%x/0x%llx\n",
        startOffset, (unsigned long long) startAddr);
    
    assert(startAddr % pageSize == startOffset % pageSize);
    Elf_Addr firstPage = startAddr - startOffset;
    debug("first page is 0x%llx\n", (unsigned long long) firstPage);
        
    /* Right now we assume that the section headers are somewhere near
       the end, which appears to be the case most of the time.
       Therefore they're not accidentally overwritten by the replaced
       sections. !!!  Fix this. */
    assert((off_t) rdi(hdr->e_shoff) >= startOffset);

    
    /* Compute the total space needed for the replaced sections, the
       ELF header, and the program headers. */
    size_t neededSpace = sizeof(Elf_Ehdr) + phdrs.size() * sizeof(Elf_Phdr);
    for (ReplacedSections::iterator i = replacedSections.begin();
         i != replacedSections.end(); ++i)
        neededSpace += roundUp(i->second.size(), sectionAlignment);

    debug("needed space is %d\n", neededSpace);

    /* If we need more space at the start of the file, then grow the
       file by the minimum number of pages and adjust internal
       offsets. */
    if (neededSpace > startOffset) {

        /* We also need an additional program header, so adjust for that. */
        neededSpace += sizeof(Elf_Phdr);
        debug("needed space is %d\n", neededSpace);
        
        unsigned int neededPages = roundUp(neededSpace - startOffset, pageSize) / pageSize;
        debug("needed pages is %d\n", neededPages);
        if (neededPages * pageSize > firstPage)
            error("virtual address space underrun!");
        
        firstPage -= neededPages * pageSize;
        startOffset += neededPages * pageSize;

        shiftFile(neededPages, firstPage);
    }


    /* Clear out the free space. */
    Elf_Off curOff = sizeof(Elf_Ehdr) + phdrs.size() * sizeof(Elf_Phdr);
    debug("clearing first %d bytes\n", startOffset - curOff);
    memset(contents + curOff, 0, startOffset - curOff);
    

    /* Write out the replaced sections. */
    writeReplacedSections(curOff, firstPage, 0);
    assert((off_t) curOff == neededSpace);

    
    rewriteHeaders(firstPage + rdi(hdr->e_phoff));
}

    
template<ElfFileParams>
void ElfFile<ElfFileParamNames>::rewriteSections()
{
    if (replacedSections.empty()) return;

    for (ReplacedSections::iterator i = replacedSections.begin();
         i != replacedSections.end(); ++i)
        debug("replacing section `%s' with size %d\n",
            i->first.c_str(), i->second.size());

    if (rdi(hdr->e_type) == ET_DYN) {
        debug("this is a dynamic library\n");
        rewriteSectionsLibrary();
    } else if (rdi(hdr->e_type) == ET_EXEC) {
        debug("this is an executable\n");
        rewriteSectionsExecutable();
    } else error("unknown ELF type");
}


template<ElfFileParams>
void ElfFile<ElfFileParamNames>::rewriteHeaders(Elf_Addr phdrAddress)
{
    /* Rewrite the program header table. */

    /* If there is a segment for the program header table, update it.
       (According to the ELF spec, it must be the first entry.) */
    if (rdi(phdrs[0].p_type) == PT_PHDR) {
        phdrs[0].p_offset = hdr->e_phoff;
        wri(phdrs[0].p_vaddr, wri(phdrs[0].p_paddr, phdrAddress));
        wri(phdrs[0].p_filesz, wri(phdrs[0].p_memsz, phdrs.size() * sizeof(Elf_Phdr)));
    }

    sortPhdrs();

    for (unsigned int i = 0; i < phdrs.size(); ++i)
        * ((Elf_Phdr *) (contents + rdi(hdr->e_phoff)) + i) = phdrs[i];

    
    /* Rewrite the section header table.  For neatness, keep the
       sections sorted. */
    assert(rdi(hdr->e_shnum) == shdrs.size());
    sortShdrs();
    for (unsigned int i = 1; i < rdi(hdr->e_shnum); ++i)
        * ((Elf_Shdr *) (contents + rdi(hdr->e_shoff)) + i) = shdrs[i];

    
    /* Update all those nasty virtual addresses in the .dynamic
       section.  Note that not all executables have .dynamic sections
       (e.g., those produced by klibc's klcc). */
    Elf_Shdr * shdrDynamic = findSection2(".dynamic");
    if (shdrDynamic) {
        Elf_Dyn * dyn = (Elf_Dyn *) (contents + rdi(shdrDynamic->sh_offset));
        unsigned int d_tag;
        for ( ; (d_tag = rdi(dyn->d_tag)) != DT_NULL; dyn++)
            if (d_tag == DT_STRTAB)
                dyn->d_un.d_ptr = findSection(".dynstr").sh_addr;
            else if (d_tag == DT_STRSZ)
                dyn->d_un.d_val = findSection(".dynstr").sh_size;
            else if (d_tag == DT_SYMTAB)
                dyn->d_un.d_ptr = findSection(".dynsym").sh_addr;
            else if (d_tag == DT_HASH)
                dyn->d_un.d_ptr = findSection(".hash").sh_addr;
            else if (d_tag == DT_GNU_HASH)
                dyn->d_un.d_ptr = findSection(".gnu.hash").sh_addr;
            else if (d_tag == DT_JMPREL) {
                Elf_Shdr * shdr = findSection2(".rel.plt");
                if (!shdr) shdr = findSection2(".rela.plt"); /* 64-bit Linux, x86-64 */
                if (!shdr) shdr = findSection2(".rela.IA_64.pltoff"); /* 64-bit Linux, IA-64 */
                if (!shdr) error("cannot find section corresponding to DT_JMPREL");
                dyn->d_un.d_ptr = shdr->sh_addr;
            }
            else if (d_tag == DT_REL) { /* !!! hack! */
                Elf_Shdr * shdr = findSection2(".rel.dyn");
                /* no idea if this makes sense, but it was needed for some
                   program */
                if (!shdr) shdr = findSection2(".rel.got");
                if (!shdr) error("cannot find .rel.dyn or .rel.got");
                dyn->d_un.d_ptr = shdr->sh_addr;
            }
            else if (d_tag == DT_RELA)
                dyn->d_un.d_ptr = findSection(".rela.dyn").sh_addr; /* PPC Linux */
            else if (d_tag == DT_VERNEED)
                dyn->d_un.d_ptr = findSection(".gnu.version_r").sh_addr;
            else if (d_tag == DT_VERSYM)
                dyn->d_un.d_ptr = findSection(".gnu.version").sh_addr;
    }
}



static void setSubstr(string & s, unsigned int pos, const string & t)
{
    assert(pos + t.size() <= s.size());
    copy(t.begin(), t.end(), s.begin() + pos);
}


template<ElfFileParams>
string ElfFile<ElfFileParamNames>::getInterpreter()
{
    Elf_Shdr & shdr = findSection(".interp");
    return string((char *) contents + rdi(shdr.sh_offset), rdi(shdr.sh_size));
}


template<ElfFileParams>
void ElfFile<ElfFileParamNames>::setInterpreter(const string & newInterpreter)
{
    string & section = replaceSection(".interp", newInterpreter.size() + 1);
    setSubstr(section, 0, newInterpreter + '\0');
    changed = true;
}


static void concatToRPath(string & rpath, const string & path)
{
    if (!rpath.empty()) rpath += ":";
    rpath += path;
}


template<ElfFileParams>
void ElfFile<ElfFileParamNames>::modifyRPath(RPathOp op, string newRPath)
{
    Elf_Shdr & shdrDynamic = findSection(".dynamic");

    /* !!! We assume that the virtual address in the DT_STRTAB entry
       of the dynamic section corresponds to the .dynstr section. */ 
    Elf_Shdr & shdrDynStr = findSection(".dynstr");
    char * strTab = (char *) contents + rdi(shdrDynStr.sh_offset);

    /* Find the DT_STRTAB entry in the dynamic section. */
    Elf_Dyn * dyn = (Elf_Dyn *) (contents + rdi(shdrDynamic.sh_offset));
    Elf_Addr strTabAddr = 0;
    for ( ; rdi(dyn->d_tag) != DT_NULL; dyn++)
        if (rdi(dyn->d_tag) == DT_STRTAB) strTabAddr = rdi(dyn->d_un.d_ptr);
    if (!strTabAddr) error("strange: no string table");

    assert(strTabAddr == rdi(shdrDynStr.sh_addr));
    
    
    /* Walk through the dynamic section, look for the RPATH/RUNPATH
       entry.

       According to the ld.so docs, DT_RPATH is obsolete, we should
       use DT_RUNPATH.  DT_RUNPATH has two advantages: it can be
       overriden by LD_LIBRARY_PATH, and it's scoped (the DT_RUNPATH
       for an executable or library doesn't affect the search path for
       libraries used by it).  DT_RPATH is ignored if DT_RUNPATH is
       present.  The binutils `ld' still generates only DT_RPATH,
       unless you use its `--enable-new-dtag' option, in which case it
       generates a DT_RPATH and DT_RUNPATH pointing at the same
       string. */
    static vector<string> neededLibs;
    dyn = (Elf_Dyn *) (contents + rdi(shdrDynamic.sh_offset));
    Elf_Dyn * dynRPath = 0, * dynRunPath = 0;
    char * rpath = 0;
    for ( ; rdi(dyn->d_tag) != DT_NULL; dyn++) {
        if (rdi(dyn->d_tag) == DT_RPATH) {
            dynRPath = dyn;
            /* Only use DT_RPATH if there is no DT_RUNPATH. */
            if (!dynRunPath) 
                rpath = strTab + rdi(dyn->d_un.d_val);
        }
        else if (rdi(dyn->d_tag) == DT_RUNPATH) {
            dynRunPath = dyn;
            rpath = strTab + rdi(dyn->d_un.d_val);
        }
        else if (rdi(dyn->d_tag) == DT_NEEDED)
	  neededLibs.push_back(string(strTab + rdi(dyn->d_un.d_val)));
    }

    if (op == rpPrint) {
        printf("%s\n", rpath ? rpath : "");
        return;
    }
    
    if (op == rpShrink && !rpath) {
        debug("no RPATH to shrink\n");
        return;
    }

    
    /* For each directory in the RPATH, check if it contains any
       needed library. */
    if (op == rpShrink) {
        static vector<bool> neededLibFound(neededLibs.size(), false);

        newRPath = "";

        char * pos = rpath;
        while (*pos) {
            char * end = strchr(pos, ':');
            if (!end) end = strchr(pos, 0);

            /* Get the name of the directory. */
            string dirName(pos, end - pos);
            if (*end == ':') ++end;
            pos = end;

            /* Non-absolute entries are allowed (e.g., the special
               "$ORIGIN" hack). */
            if (dirName[0] != '/') {
                concatToRPath(newRPath, dirName);
                continue;
            }

            /* For each library that we haven't found yet, see if it
               exists in this directory. */
            bool libFound = false;
            for (unsigned int j = 0; j < neededLibs.size(); ++j)
                if (!neededLibFound[j]) {
                    string libName = dirName + "/" + neededLibs[j];
                    struct stat st;
                    if (stat(libName.c_str(), &st) == 0) {
                        neededLibFound[j] = true;
                        libFound = true;
                    }
                }

            if (!libFound)
                debug("removing directory `%s' from RPATH\n", dirName.c_str());
            else
                concatToRPath(newRPath, dirName);
        }
    }

    
    if (string(rpath ? rpath : "") == newRPath) return;

    changed = true;
    
    /* Zero out the previous rpath to prevent retained dependencies in
       Nix. */
    unsigned int rpathSize = 0;
    if (rpath) {
        rpathSize = strlen(rpath);
        memset(rpath, 'X', rpathSize);
    }

    debug("new rpath is `%s'\n", newRPath.c_str());

    if (!forceRPath && dynRPath && !dynRunPath) { /* convert DT_RPATH to DT_RUNPATH */
        dynRPath->d_tag = DT_RUNPATH;
        dynRunPath = dynRPath;
        dynRPath = 0;
    }

    if (forceRPath && dynRPath && dynRunPath) { /* convert DT_RUNPATH to DT_RPATH */
        dynRunPath->d_tag = DT_IGNORE;
    }
    
    if (newRPath.size() <= rpathSize) {
        strcpy(rpath, newRPath.c_str());
        return;
    }

    /* Grow the .dynstr section to make room for the new RPATH. */
    debug("rpath is too long, resizing...\n");

    string & newDynStr = replaceSection(".dynstr",
        rdi(shdrDynStr.sh_size) + newRPath.size() + 1);
    setSubstr(newDynStr, rdi(shdrDynStr.sh_size), newRPath + '\0');

    /* Update the DT_RUNPATH and DT_RPATH entries. */
    if (dynRunPath || dynRPath) {
        if (dynRunPath) dynRunPath->d_un.d_val = shdrDynStr.sh_size;
        if (dynRPath) dynRPath->d_un.d_val = shdrDynStr.sh_size;
    }

    else {
        /* There is no DT_RUNPATH entry in the .dynamic section, so we
           have to grow the .dynamic section. */
        string & newDynamic = replaceSection(".dynamic",
            rdi(shdrDynamic.sh_size) + sizeof(Elf_Dyn));

        unsigned int idx = 0;
        for ( ; rdi(((Elf_Dyn *) newDynamic.c_str())[idx].d_tag) != DT_NULL; idx++) ;
        debug("DT_NULL index is %d\n", idx);

        /* Shift all entries down by one. */
        setSubstr(newDynamic, sizeof(Elf_Dyn),
            string(newDynamic, 0, sizeof(Elf_Dyn) * (idx + 1)));

        /* Add the DT_RUNPATH entry at the top. */
        Elf_Dyn newDyn;
        wri(newDyn.d_tag, forceRPath ? DT_RPATH : DT_RUNPATH);
        newDyn.d_un.d_val = shdrDynStr.sh_size;
        setSubstr(newDynamic, 0, string((char *) &newDyn, sizeof(Elf_Dyn)));
    }
}


static bool printInterpreter = false;
static string newInterpreter;

static bool shrinkRPath = false;
static bool setRPath = false;
static bool printRPath = false;
static string newRPath;


template<class ElfFile>
static void patchElf2(ElfFile & elfFile, mode_t fileMode)
{
    elfFile.parse();


    if (printInterpreter)
        printf("%s\n", elfFile.getInterpreter().c_str());
    
    if (newInterpreter != "")
        elfFile.setInterpreter(newInterpreter);

    if (printRPath)
        elfFile.modifyRPath(elfFile.rpPrint, "");

    if (shrinkRPath)
        elfFile.modifyRPath(elfFile.rpShrink, "");
    else if (setRPath)
        elfFile.modifyRPath(elfFile.rpSet, newRPath);
    
    
    if (elfFile.isChanged()){
        elfFile.rewriteSections();
        writeFile(fileName, fileMode);
    }
}

    
static void patchElf()
{
    if (!printInterpreter && !printRPath)
        debug("patching ELF file `%s'\n", fileName.c_str());

    mode_t fileMode;
    
    readFile(fileName, &fileMode);


    /* Check the ELF header for basic validity. */
    if (fileSize < (off_t) sizeof(Elf32_Ehdr)) error("missing ELF header");

    if (memcmp(contents, ELFMAG, SELFMAG) != 0)
        error("not an ELF executable");
    
    if (contents[EI_CLASS] == ELFCLASS32 &&
        contents[EI_VERSION] == EV_CURRENT)
    {
        ElfFile<Elf32_Ehdr, Elf32_Phdr, Elf32_Shdr, Elf32_Addr, Elf32_Off, Elf32_Dyn> elfFile;
        patchElf2(elfFile, fileMode);
    }
    else if (contents[EI_CLASS] == ELFCLASS64 &&
        contents[EI_VERSION] == EV_CURRENT)
    {
        ElfFile<Elf64_Ehdr, Elf64_Phdr, Elf64_Shdr, Elf64_Addr, Elf64_Off, Elf64_Dyn> elfFile;
        patchElf2(elfFile, fileMode);
    }
    else {
        error("ELF executable is not 32/64-bit, little/big-endian, version 1");
    }
}


void showHelp(const string & progName)
{
        fprintf(stderr, "syntax: %s\n\
  [--set-interpreter FILENAME]\n\
  [--print-interpreter]\n\
  [--set-rpath RPATH]\n\
  [--shrink-rpath]\n\
  [--print-rpath]\n\
  [--force-rpath]\n\
  [--debug]\n\
  [--version]\n\
  FILENAME\n", progName.c_str());
}


int main(int argc, char * * argv)
{
    if (argc <= 1) {
        showHelp(argv[0]);
        return 1;
    }

    if (getenv("PATCHELF_DEBUG") != 0) debugMode = true;

    int i;
    for (i = 1; i < argc; ++i) {
        string arg(argv[i]);
        if (arg == "--set-interpreter" || arg == "--interpreter") {
            if (++i == argc) error("missing argument");
            newInterpreter = argv[i];
        }
        else if (arg == "--print-interpreter") {
            printInterpreter = true;
        }
        else if (arg == "--shrink-rpath") {
            shrinkRPath = true;
        }
        else if (arg == "--set-rpath") {
            if (++i == argc) error("missing argument");
            setRPath = true;
            newRPath = argv[i];
        }
        else if (arg == "--print-rpath") {
            printRPath = true;
        }
        else if (arg == "--force-rpath") {
            /* Generally we prefer to emit DT_RUNPATH instead of
               DT_RPATH, as the latter is obsolete.  However, there is
               a slight semantic difference: DT_RUNPATH is "scoped",
               it only affects the executable or library in question,
               not its recursive imports.  So maybe you really want to
               force the use of DT_RPATH.  That's what this option
               does.  Without it, DT_RPATH (if encountered) is
               converted to DT_RUNPATH, and if neither is present, a
               DT_RUNPATH is added.  With it, DT_RPATH isn't converted
               to DT_RUNPATH, and if neither is present, a DT_RPATH is
               added. */
            forceRPath = true;
        }
        else if (arg == "--debug") {
            debugMode = true;
        }
        else if (arg == "--help") {
            showHelp(argv[0]);
            return 0;
        }
        else if (arg == "--version") {
            printf("1.0\n");
            return 0;
        }
        else break;
    }

    if (i == argc) error("missing filename");
    fileName = argv[i];

    patchElf();

    return 0;
}