diff -r 000000000000 -r 6474c204b198 build/unix/elfhack/elfhack.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/build/unix/elfhack/elfhack.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,823 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#undef NDEBUG
+#include <assert.h>
+#include <cstring>
+#include <cstdlib>
+#include <cstdio>
+#include "elfxx.h"
+
+#define ver "0"
+#define elfhack_data ".elfhack.data.v" ver
+#define elfhack_text ".elfhack.text.v" ver
+
+#ifndef R_ARM_V4BX
+#define R_ARM_V4BX 0x28
+#endif
+#ifndef R_ARM_CALL
+#define R_ARM_CALL 0x1c
+#endif
+#ifndef R_ARM_JUMP24
+#define R_ARM_JUMP24 0x1d
+#endif
+#ifndef R_ARM_THM_JUMP24
+#define R_ARM_THM_JUMP24 0x1e
+#endif
+
+char *rundir = nullptr;
+
+template <typename T>
+struct wrapped {
+    T value;
+};
+
+class Elf_Addr_Traits {
+public:
+    typedef wrapped<Elf32_Addr> Type32;
+    typedef wrapped<Elf64_Addr> Type64;
+
+    template <class endian, typename R, typename T>
+    static inline void swap(T &t, R &r) {
+        r.value = endian::swap(t.value);
+    }
+};
+
+typedef serializable<Elf_Addr_Traits> Elf_Addr;
+
+class Elf_RelHack_Traits {
+public:
+    typedef Elf32_Rel Type32;
+    typedef Elf32_Rel Type64;
+
+    template <class endian, typename R, typename T>
+    static inline void swap(T &t, R &r) {
+        r.r_offset = endian::swap(t.r_offset);
+        r.r_info = endian::swap(t.r_info);
+    }
+};
+
+typedef serializable<Elf_RelHack_Traits> Elf_RelHack;
+
+class ElfRelHack_Section: public ElfSection {
+public:
+    ElfRelHack_Section(Elf_Shdr &s)
+    : ElfSection(s, nullptr, nullptr)
+    {
+        name = elfhack_data;
+    };
+
+    void serialize(std::ofstream &file, char ei_class, char ei_data)
+    {
+        for (std::vector<Elf_RelHack>::iterator i = rels.begin();
+             i != rels.end(); ++i)
+            (*i).serialize(file, ei_class, ei_data);
+    }
+
+    bool isRelocatable() {
+        return true;
+    }
+
+    void push_back(Elf_RelHack &r) {
+        rels.push_back(r);
+        shdr.sh_size = rels.size() * shdr.sh_entsize;
+    }
+private:
+    std::vector<Elf_RelHack> rels;
+};
+
+class ElfRelHackCode_Section: public ElfSection {
+public:
+    ElfRelHackCode_Section(Elf_Shdr &s, Elf &e, unsigned int init)
+    : ElfSection(s, nullptr, nullptr), parent(e), init(init) {
+        std::string file(rundir);
+        file += "/inject/";
+        switch (parent.getMachine()) {
+        case EM_386:
+            file += "x86";
+            break;
+        case EM_X86_64:
+            file += "x86_64";
+            break;
+        case EM_ARM:
+            file += "arm";
+            break;
+        default:
+            throw std::runtime_error("unsupported architecture");
+        }
+        file += ".o";
+        std::ifstream inject(file.c_str(), std::ios::in|std::ios::binary);
+        elf = new Elf(inject);
+        if (elf->getType() != ET_REL)
+            throw std::runtime_error("object for injected code is not ET_REL");
+        if (elf->getMachine() != parent.getMachine())
+            throw std::runtime_error("architecture of object for injected code doesn't match");
+
+        ElfSymtab_Section *symtab = nullptr;
+
+        // Find the symbol table.
+        for (ElfSection *section = elf->getSection(1); section != nullptr;
+             section = section->getNext()) {
+            if (section->getType() == SHT_SYMTAB)
+                symtab = (ElfSymtab_Section *) section;
+        }
+        if (symtab == nullptr)
+            throw std::runtime_error("Couldn't find a symbol table for the injected code");
+
+        // Find the init symbol
+        entry_point = -1;
+        Elf_SymValue *sym = symtab->lookup(init ? "init" : "init_noinit");
+        if (!sym)
+            throw std::runtime_error("Couldn't find an 'init' symbol in the injected code");
+
+        entry_point = sym->value.getValue();
+
+        // Get all relevant sections from the injected code object.
+        add_code_section(sym->value.getSection());
+
+        // Adjust code sections offsets according to their size
+        std::vector<ElfSection *>::iterator c = code.begin();
+        (*c)->getShdr().sh_addr = 0;
+        for(ElfSection *last = *(c++); c != code.end(); c++) {
+            unsigned int addr = last->getShdr().sh_addr + last->getSize();
+            if (addr & ((*c)->getAddrAlign() - 1))
+                addr = (addr | ((*c)->getAddrAlign() - 1)) + 1;
+            (*c)->getShdr().sh_addr = addr;
+            // We need to align this section depending on the greater
+            // alignment required by code sections.
+            if (shdr.sh_addralign < (*c)->getAddrAlign())
+                shdr.sh_addralign = (*c)->getAddrAlign();
+        }
+        shdr.sh_size = code.back()->getAddr() + code.back()->getSize();
+        data = new char[shdr.sh_size];
+        char *buf = data;
+        for (c = code.begin(); c != code.end(); c++) {
+            memcpy(buf, (*c)->getData(), (*c)->getSize());
+            buf += (*c)->getSize();
+        }
+        name = elfhack_text;
+    }
+
+    ~ElfRelHackCode_Section() {
+        delete elf;
+    }
+
+    void serialize(std::ofstream &file, char ei_class, char ei_data)
+    {
+        // Readjust code offsets
+        for (std::vector<ElfSection *>::iterator c = code.begin(); c != code.end(); c++)
+            (*c)->getShdr().sh_addr += getAddr();
+
+        // Apply relocations
+        for (std::vector<ElfSection *>::iterator c = code.begin(); c != code.end(); c++) {
+            for (ElfSection *rel = elf->getSection(1); rel != nullptr; rel = rel->getNext())
+                if (((rel->getType() == SHT_REL) ||
+                     (rel->getType() == SHT_RELA)) &&
+                    (rel->getInfo().section == *c)) {
+                    if (rel->getType() == SHT_REL)
+                        apply_relocations((ElfRel_Section<Elf_Rel> *)rel, *c);
+                    else
+                        apply_relocations((ElfRel_Section<Elf_Rela> *)rel, *c);
+                }
+            }
+
+        ElfSection::serialize(file, ei_class, ei_data);
+    }
+
+    bool isRelocatable() {
+        return true;
+    }
+
+    unsigned int getEntryPoint() {
+        return entry_point;
+    }
+private:
+    void add_code_section(ElfSection *section)
+    {
+        if (section) {
+            /* Don't add section if it's already been added in the past */
+            for (auto s = code.begin(); s != code.end(); ++s) {
+                if (section == *s)
+                    return;
+            }
+            code.push_back(section);
+            find_code(section);
+        }
+    }
+
+    /* Look at the relocations associated to the given section to find other
+     * sections that it requires */
+    void find_code(ElfSection *section)
+    {
+        for (ElfSection *s = elf->getSection(1); s != nullptr;
+             s = s->getNext()) {
+            if (((s->getType() == SHT_REL) ||
+                 (s->getType() == SHT_RELA)) &&
+                (s->getInfo().section == section)) {
+                if (s->getType() == SHT_REL)
+                    scan_relocs_for_code((ElfRel_Section<Elf_Rel> *)s);
+                else
+                    scan_relocs_for_code((ElfRel_Section<Elf_Rela> *)s);
+            }
+        }
+    }
+
+    template <typename Rel_Type>
+    void scan_relocs_for_code(ElfRel_Section<Rel_Type> *rel)
+    {
+        ElfSymtab_Section *symtab = (ElfSymtab_Section *)rel->getLink();
+        for (auto r = rel->rels.begin(); r != rel->rels.end(); r++) {
+            ElfSection *section = symtab->syms[ELF32_R_SYM(r->r_info)].value.getSection();
+            add_code_section(section);
+        }
+    }
+
+    class pc32_relocation {
+    public:
+        Elf32_Addr operator()(unsigned int base_addr, Elf32_Off offset,
+                              Elf32_Word addend, unsigned int addr)
+        {
+            return addr + addend - offset - base_addr;
+        }
+    };
+
+    class arm_plt32_relocation {
+    public:
+        Elf32_Addr operator()(unsigned int base_addr, Elf32_Off offset,
+                              Elf32_Word addend, unsigned int addr)
+        {
+            // We don't care about sign_extend because the only case where this is
+            // going to be used only jumps forward.
+            Elf32_Addr tmp = (Elf32_Addr) (addr - offset - base_addr) >> 2;
+            tmp = (addend + tmp) & 0x00ffffff;
+            return (addend & 0xff000000) | tmp;
+        }
+    };
+
+    class arm_thm_jump24_relocation {
+    public:
+        Elf32_Addr operator()(unsigned int base_addr, Elf32_Off offset,
+                              Elf32_Word addend, unsigned int addr)
+        {
+            /* Follows description of b.w and bl instructions as per
+               ARM Architecture Reference Manual ARM® v7-A and ARM® v7-R edition, A8.6.16
+               We limit ourselves to Encoding T4 of b.w and Encoding T1 of bl.
+               We don't care about sign_extend because the only case where this is
+               going to be used only jumps forward. */
+            Elf32_Addr tmp = (Elf32_Addr) (addr - offset - base_addr);
+            unsigned int word0 = addend & 0xffff,
+                         word1 = addend >> 16;
+
+            /* Encoding T4 of B.W is 10x1 ; Encoding T1 of BL is 11x1. */
+            unsigned int type = (word1 & 0xd000) >> 12;
+            if (((word0 & 0xf800) != 0xf000) || ((type & 0x9) != 0x9))
+                throw std::runtime_error("R_ARM_THM_JUMP24/R_ARM_THM_CALL relocation only supported for B.W <label> and BL <label>");
+
+            /* When the target address points to ARM code, switch a BL to a
+             * BLX. This however can't be done with a B.W without adding a
+             * trampoline, which is not supported as of now. */
+            if ((addr & 0x1) == 0) {
+                if (type == 0x9)
+                    throw std::runtime_error("R_ARM_THM_JUMP24/R_ARM_THM_CALL relocation only supported for BL <label> when label points to ARM code");
+                /* The address of the target is always relative to a 4-bytes
+                 * aligned address, so if the address of the BL instruction is
+                 * not 4-bytes aligned, adjust for it. */
+                if ((base_addr + offset) & 0x2)
+                    tmp += 2;
+                /* Encoding T2 of BLX is 11x0. */
+                type = 0xc;
+            }
+
+            unsigned int s = (word0 & (1 << 10)) >> 10;
+            unsigned int j1 = (word1 & (1 << 13)) >> 13;
+            unsigned int j2 = (word1 & (1 << 11)) >> 11;
+            unsigned int i1 = j1 ^ s ? 0 : 1;
+            unsigned int i2 = j2 ^ s ? 0 : 1;
+
+            tmp += ((s << 24) | (i1 << 23) | (i2 << 22) | ((word0 & 0x3ff) << 12) | ((word1 & 0x7ff) << 1));
+
+            s = (tmp & (1 << 24)) >> 24;
+            j1 = ((tmp & (1 << 23)) >> 23) ^ !s;
+            j2 = ((tmp & (1 << 22)) >> 22) ^ !s;
+
+            return 0xf000 | (s << 10) | ((tmp & (0x3ff << 12)) >> 12) |
+                   (type << 28) | (j1 << 29) | (j2 << 27) | ((tmp & 0xffe) << 15);
+        }
+    };
+
+    class gotoff_relocation {
+    public:
+        Elf32_Addr operator()(unsigned int base_addr, Elf32_Off offset,
+                              Elf32_Word addend, unsigned int addr)
+        {
+            return addr + addend;
+        }
+    };
+
+    template <class relocation_type>
+    void apply_relocation(ElfSection *the_code, char *base, Elf_Rel *r, unsigned int addr)
+    {
+        relocation_type relocation;
+        Elf32_Addr value;
+        memcpy(&value, base + r->r_offset, 4);
+        value = relocation(the_code->getAddr(), r->r_offset, value, addr);
+        memcpy(base + r->r_offset, &value, 4);
+    }
+
+    template <class relocation_type>
+    void apply_relocation(ElfSection *the_code, char *base, Elf_Rela *r, unsigned int addr)
+    {
+        relocation_type relocation;
+        Elf32_Addr value = relocation(the_code->getAddr(), r->r_offset, r->r_addend, addr);
+        memcpy(base + r->r_offset, &value, 4);
+    }
+
+    template <typename Rel_Type>
+    void apply_relocations(ElfRel_Section<Rel_Type> *rel, ElfSection *the_code)
+    {
+        assert(rel->getType() == Rel_Type::sh_type);
+        char *buf = data + (the_code->getAddr() - code.front()->getAddr());
+        // TODO: various checks on the sections
+        ElfSymtab_Section *symtab = (ElfSymtab_Section *)rel->getLink();
+        for (typename std::vector<Rel_Type>::iterator r = rel->rels.begin(); r != rel->rels.end(); r++) {
+            // TODO: various checks on the symbol
+            const char *name = symtab->syms[ELF32_R_SYM(r->r_info)].name;
+            unsigned int addr;
+            if (symtab->syms[ELF32_R_SYM(r->r_info)].value.getSection() == nullptr) {
+                if (strcmp(name, "relhack") == 0) {
+                    addr = getNext()->getAddr();
+                } else if (strcmp(name, "elf_header") == 0) {
+                    // TODO: change this ungly hack to something better
+                    ElfSection *ehdr = parent.getSection(1)->getPrevious()->getPrevious();
+                    addr = ehdr->getAddr();
+                } else if (strcmp(name, "original_init") == 0) {
+                    addr = init;
+                } else if (strcmp(name, "_GLOBAL_OFFSET_TABLE_") == 0) {
+                    // We actually don't need a GOT, but need it as a reference for
+                    // GOTOFF relocations. We'll just use the start of the ELF file
+                    addr = 0;
+                } else if (strcmp(name, "") == 0) {
+                    // This is for R_ARM_V4BX, until we find something better
+                    addr = -1;
+                } else {
+                    throw std::runtime_error("Unsupported symbol in relocation");
+                }
+            } else {
+                ElfSection *section = symtab->syms[ELF32_R_SYM(r->r_info)].value.getSection();
+                assert((section->getType() == SHT_PROGBITS) && (section->getFlags() & SHF_EXECINSTR));
+                addr = symtab->syms[ELF32_R_SYM(r->r_info)].value.getValue();
+            }
+            // Do the relocation
+#define REL(machine, type) (EM_ ## machine | (R_ ## machine ## _ ## type << 8))
+            switch (elf->getMachine() | (ELF32_R_TYPE(r->r_info) << 8)) {
+            case REL(X86_64, PC32):
+            case REL(386, PC32):
+            case REL(386, GOTPC):
+            case REL(ARM, GOTPC):
+            case REL(ARM, REL32):
+                apply_relocation<pc32_relocation>(the_code, buf, &*r, addr);
+                break;
+            case REL(ARM, CALL):
+            case REL(ARM, JUMP24):
+            case REL(ARM, PLT32):
+                apply_relocation<arm_plt32_relocation>(the_code, buf, &*r, addr);
+                break;
+            case REL(ARM, THM_PC22 /* THM_CALL */):
+            case REL(ARM, THM_JUMP24):
+                apply_relocation<arm_thm_jump24_relocation>(the_code, buf, &*r, addr);
+                break;
+            case REL(386, GOTOFF):
+            case REL(ARM, GOTOFF):
+                apply_relocation<gotoff_relocation>(the_code, buf, &*r, addr);
+                break;
+            case REL(ARM, V4BX):
+                // Ignore R_ARM_V4BX relocations
+                break;
+            default:
+                throw std::runtime_error("Unsupported relocation type");
+            }
+        }
+    }
+
+    Elf *elf, &parent;
+    std::vector<ElfSection *> code;
+    unsigned int init;
+    int entry_point;
+};
+
+unsigned int get_addend(Elf_Rel *rel, Elf *elf) {
+    ElfLocation loc(rel->r_offset, elf);
+    Elf_Addr addr(loc.getBuffer(), Elf_Addr::size(elf->getClass()), elf->getClass(), elf->getData());
+    return addr.value;
+}
+
+unsigned int get_addend(Elf_Rela *rel, Elf *elf) {
+    return rel->r_addend;
+}
+
+void set_relative_reloc(Elf_Rel *rel, Elf *elf, unsigned int value) {
+    ElfLocation loc(rel->r_offset, elf);
+    Elf_Addr addr;
+    addr.value = value;
+    addr.serialize(const_cast<char *>(loc.getBuffer()), Elf_Addr::size(elf->getClass()), elf->getClass(), elf->getData());
+}
+
+void set_relative_reloc(Elf_Rela *rel, Elf *elf, unsigned int value) {
+    // ld puts the value of relocated relocations both in the addend and
+    // at r_offset. For consistency, keep it that way.
+    set_relative_reloc((Elf_Rel *)rel, elf, value);
+    rel->r_addend = value;
+}
+
+void maybe_split_segment(Elf *elf, ElfSegment *segment, bool fill)
+{
+    std::list<ElfSection *>::iterator it = segment->begin();
+    for (ElfSection *last = *(it++); it != segment->end(); last = *(it++)) {
+        // When two consecutive non-SHT_NOBITS sections are apart by more
+        // than the alignment of the section, the second can be moved closer
+        // to the first, but this requires the segment to be split.
+        if (((*it)->getType() != SHT_NOBITS) && (last->getType() != SHT_NOBITS) &&
+            ((*it)->getOffset() - last->getOffset() - last->getSize() > segment->getAlign())) {
+            // Probably very wrong.
+            Elf_Phdr phdr;
+            phdr.p_type = PT_LOAD;
+            phdr.p_vaddr = 0;
+            phdr.p_paddr = phdr.p_vaddr + segment->getVPDiff();
+            phdr.p_flags = segment->getFlags();
+            phdr.p_align = segment->getAlign();
+            phdr.p_filesz = (unsigned int)-1;
+            phdr.p_memsz = (unsigned int)-1;
+            ElfSegment *newSegment = new ElfSegment(&phdr);
+            elf->insertSegmentAfter(segment, newSegment);
+            ElfSection *section = *it;
+            for (; it != segment->end(); ++it) {
+                newSegment->addSection(*it);
+            }
+            for (it = newSegment->begin(); it != newSegment->end(); it++) {
+                segment->removeSection(*it);
+            }
+            // Fill the virtual address space gap left between the two PT_LOADs
+            // with a new PT_LOAD with no permissions. This avoids the linker
+            // (especially bionic's) filling the gap with anonymous memory,
+            // which breakpad doesn't like.
+            // /!\ running strip on a elfhacked binary will break this filler
+            // PT_LOAD.
+            if (!fill)
+                break;
+            // Insert dummy segment to normalize the entire Elf with the header
+            // sizes adjusted, before inserting a filler segment.
+            {
+              memset(&phdr, 0, sizeof(phdr));
+              ElfSegment dummySegment(&phdr);
+              elf->insertSegmentAfter(segment, &dummySegment);
+              elf->normalize();
+              elf->removeSegment(&dummySegment);
+            }
+            ElfSection *previous = section->getPrevious();
+            phdr.p_type = PT_LOAD;
+            phdr.p_vaddr = (previous->getAddr() + previous->getSize() + segment->getAlign() - 1) & ~(segment->getAlign() - 1);
+            phdr.p_paddr = phdr.p_vaddr + segment->getVPDiff();
+            phdr.p_flags = 0;
+            phdr.p_align = 0;
+            phdr.p_filesz = (section->getAddr() & ~(newSegment->getAlign() - 1)) - phdr.p_vaddr;
+            phdr.p_memsz = phdr.p_filesz;
+            if (phdr.p_filesz) {
+                newSegment = new ElfSegment(&phdr);
+                assert(newSegment->isElfHackFillerSegment());
+                elf->insertSegmentAfter(segment, newSegment);
+            } else {
+                elf->normalize();
+            }
+            break;
+        }
+    }
+}
+
+template <typename Rel_Type>
+int do_relocation_section(Elf *elf, unsigned int rel_type, unsigned int rel_type2, bool force, bool fill)
+{
+    ElfDynamic_Section *dyn = elf->getDynSection();
+    if (dyn == nullptr) {
+        fprintf(stderr, "Couldn't find SHT_DYNAMIC section\n");
+        return -1;
+    }
+
+    ElfSegment *relro = elf->getSegmentByType(PT_GNU_RELRO);
+
+    ElfRel_Section<Rel_Type> *section = (ElfRel_Section<Rel_Type> *)dyn->getSectionForType(Rel_Type::d_tag);
+    assert(section->getType() == Rel_Type::sh_type);
+
+    Elf32_Shdr relhack32_section =
+        { 0, SHT_PROGBITS, SHF_ALLOC, 0, (Elf32_Off)-1, 0, SHN_UNDEF, 0,
+          Elf_RelHack::size(elf->getClass()), Elf_RelHack::size(elf->getClass()) }; // TODO: sh_addralign should be an alignment, not size
+    Elf32_Shdr relhackcode32_section =
+        { 0, SHT_PROGBITS, SHF_ALLOC | SHF_EXECINSTR, 0, (Elf32_Off)-1, 0,
+          SHN_UNDEF, 0, 1, 0 };
+
+    unsigned int entry_sz = Elf_Addr::size(elf->getClass());
+
+    // The injected code needs to be executed before any init code in the
+    // binary. There are three possible cases:
+    // - The binary has no init code at all. In this case, we will add a
+    //   DT_INIT entry pointing to the injected code.
+    // - The binary has a DT_INIT entry. In this case, we will interpose:
+    //   we change DT_INIT to point to the injected code, and have the
+    //   injected code call the original DT_INIT entry point.
+    // - The binary has no DT_INIT entry, but has a DT_INIT_ARRAY. In this
+    //   case, we interpose as well, by replacing the first entry in the
+    //   array to point to the injected code, and have the injected code
+    //   call the original first entry.
+    // The binary may have .ctors instead of DT_INIT_ARRAY, for its init
+    // functions, but this falls into the second case above, since .ctors
+    // are actually run by DT_INIT code.
+    ElfValue *value = dyn->getValueForType(DT_INIT);
+    unsigned int original_init = value ? value->getValue() : 0;
+    ElfSection *init_array = nullptr;
+    if (!value || !value->getValue()) {
+        value = dyn->getValueForType(DT_INIT_ARRAYSZ);
+        if (value && value->getValue() >= entry_sz)
+            init_array = dyn->getSectionForType(DT_INIT_ARRAY);
+    }
+
+    Elf_Shdr relhack_section(relhack32_section);
+    Elf_Shdr relhackcode_section(relhackcode32_section);
+    ElfRelHack_Section *relhack = new ElfRelHack_Section(relhack_section);
+
+    ElfSymtab_Section *symtab = (ElfSymtab_Section *) section->getLink();
+    Elf_SymValue *sym = symtab->lookup("__cxa_pure_virtual");
+
+    std::vector<Rel_Type> new_rels;
+    Elf_RelHack relhack_entry;
+    relhack_entry.r_offset = relhack_entry.r_info = 0;
+    size_t init_array_reloc = 0;
+    for (typename std::vector<Rel_Type>::iterator i = section->rels.begin();
+         i != section->rels.end(); i++) {
+        // We don't need to keep R_*_NONE relocations
+        if (!ELF32_R_TYPE(i->r_info))
+            continue;
+        ElfLocation loc(i->r_offset, elf);
+        // __cxa_pure_virtual is a function used in vtables to point at pure
+        // virtual methods. The __cxa_pure_virtual function usually abort()s.
+        // These functions are however normally never called. In the case
+        // where they would, jumping to the null address instead of calling
+        // __cxa_pure_virtual is going to work just as well. So we can remove
+        // relocations for the __cxa_pure_virtual symbol and null out the
+        // content at the offset pointed by the relocation.
+        if (sym) {
+            if (sym->defined) {
+                // If we are statically linked to libstdc++, the
+                // __cxa_pure_virtual symbol is defined in our lib, and we
+                // have relative relocations (rel_type) for it.
+                if (ELF32_R_TYPE(i->r_info) == rel_type) {
+                    Elf_Addr addr(loc.getBuffer(), entry_sz, elf->getClass(), elf->getData());
+                    if (addr.value == sym->value.getValue()) {
+                        memset((char *)loc.getBuffer(), 0, entry_sz);
+                        continue;
+                    }
+                }
+            } else {
+                // If we are dynamically linked to libstdc++, the
+                // __cxa_pure_virtual symbol is undefined in our lib, and we
+                // have absolute relocations (rel_type2) for it.
+                if ((ELF32_R_TYPE(i->r_info) == rel_type2) &&
+                    (sym == &symtab->syms[ELF32_R_SYM(i->r_info)])) {
+                    memset((char *)loc.getBuffer(), 0, entry_sz);
+                    continue;
+                }
+            }
+        }
+        // Keep track of the relocation associated with the first init_array entry.
+        if (init_array && i->r_offset == init_array->getAddr()) {
+            if (init_array_reloc) {
+                fprintf(stderr, "Found multiple relocations for the first init_array entry. Skipping\n");
+                return -1;
+            }
+            new_rels.push_back(*i);
+            init_array_reloc = new_rels.size();
+        } else if (!(loc.getSection()->getFlags() & SHF_WRITE) || (ELF32_R_TYPE(i->r_info) != rel_type) ||
+                   (relro && (i->r_offset >= relro->getAddr()) &&
+                   (i->r_offset < relro->getAddr() + relro->getMemSize()))) {
+            // Don't pack relocations happening in non writable sections.
+            // Our injected code is likely not to be allowed to write there.
+            new_rels.push_back(*i);
+        } else {
+            // TODO: check that i->r_addend == *i->r_offset
+            if (i->r_offset == relhack_entry.r_offset + relhack_entry.r_info * entry_sz) {
+                relhack_entry.r_info++;
+            } else {
+                if (relhack_entry.r_offset)
+                    relhack->push_back(relhack_entry);
+                relhack_entry.r_offset = i->r_offset;
+                relhack_entry.r_info = 1;
+            }
+        }
+    }
+    if (relhack_entry.r_offset)
+        relhack->push_back(relhack_entry);
+    // Last entry must be nullptr
+    relhack_entry.r_offset = relhack_entry.r_info = 0;
+    relhack->push_back(relhack_entry);
+
+    unsigned int old_end = section->getOffset() + section->getSize();
+
+    if (init_array) {
+        if (! init_array_reloc) {
+            fprintf(stderr, "Didn't find relocation for DT_INIT_ARRAY's first entry. Skipping\n");
+            return -1;
+        }
+        Rel_Type *rel = &new_rels[init_array_reloc - 1];
+        unsigned int addend = get_addend(rel, elf);
+        // Use relocated value of DT_INIT_ARRAY's first entry for the
+        // function to be called by the injected code.
+        if (ELF32_R_TYPE(rel->r_info) == rel_type) {
+            original_init = addend;
+        } else if (ELF32_R_TYPE(rel->r_info) == rel_type2) {
+            ElfSymtab_Section *symtab = (ElfSymtab_Section *)section->getLink();
+            original_init = symtab->syms[ELF32_R_SYM(rel->r_info)].value.getValue() + addend;
+        } else {
+            fprintf(stderr, "Unsupported relocation type for DT_INIT_ARRAY's first entry. Skipping\n");
+            return -1;
+        }
+    }
+
+    section->rels.assign(new_rels.begin(), new_rels.end());
+    section->shrink(new_rels.size() * section->getEntSize());
+
+    ElfRelHackCode_Section *relhackcode = new ElfRelHackCode_Section(relhackcode_section, *elf, original_init);
+    relhackcode->insertBefore(section);
+    relhack->insertAfter(relhackcode);
+    if (section->getOffset() + section->getSize() >= old_end) {
+        fprintf(stderr, "No gain. Skipping\n");
+        return -1;
+    }
+
+    // Adjust PT_LOAD segments
+    for (ElfSegment *segment = elf->getSegmentByType(PT_LOAD); segment;
+         segment = elf->getSegmentByType(PT_LOAD, segment)) {
+        maybe_split_segment(elf, segment, fill);
+    }
+
+    // Ensure Elf sections will be at their final location.
+    elf->normalize();
+    ElfLocation *init = new ElfLocation(relhackcode, relhackcode->getEntryPoint());
+    if (init_array) {
+        // Adjust the first DT_INIT_ARRAY entry to point at the injected code
+        // by transforming its relocation into a relative one pointing to the
+        // address of the injected code.
+        Rel_Type *rel = &section->rels[init_array_reloc - 1];
+        rel->r_info = ELF32_R_INFO(0, rel_type); // Set as a relative relocation
+        set_relative_reloc(&section->rels[init_array_reloc - 1], elf, init->getValue());
+    } else if (!dyn->setValueForType(DT_INIT, init)) {
+        fprintf(stderr, "Can't grow .dynamic section to set DT_INIT. Skipping\n");
+        return -1;
+    }
+    // TODO: adjust the value according to the remaining number of relative relocations
+    if (dyn->getValueForType(Rel_Type::d_tag_count))
+        dyn->setValueForType(Rel_Type::d_tag_count, new ElfPlainValue(0));
+
+    return 0;
+}
+
+static inline int backup_file(const char *name)
+{
+    std::string fname(name);
+    fname += ".bak";
+    return rename(name, fname.c_str());
+}
+
+void do_file(const char *name, bool backup = false, bool force = false, bool fill = false)
+{
+    std::ifstream file(name, std::ios::in|std::ios::binary);
+    Elf elf(file);
+    unsigned int size = elf.getSize();
+    fprintf(stderr, "%s: ", name);
+    if (elf.getType() != ET_DYN) {
+        fprintf(stderr, "Not a shared object. Skipping\n");
+        return;
+    }
+
+    for (ElfSection *section = elf.getSection(1); section != nullptr;
+         section = section->getNext()) {
+        if (section->getName() &&
+            (strncmp(section->getName(), ".elfhack.", 9) == 0)) {
+            fprintf(stderr, "Already elfhacked. Skipping\n");
+            return;
+        }
+    }
+
+    int exit = -1;
+    switch (elf.getMachine()) {
+    case EM_386:
+        exit = do_relocation_section<Elf_Rel>(&elf, R_386_RELATIVE, R_386_32, force, fill);
+        break;
+    case EM_X86_64:
+        exit = do_relocation_section<Elf_Rela>(&elf, R_X86_64_RELATIVE, R_X86_64_64, force, fill);
+        break;
+    case EM_ARM:
+        exit = do_relocation_section<Elf_Rel>(&elf, R_ARM_RELATIVE, R_ARM_ABS32, force, fill);
+        break;
+    }
+    if (exit == 0) {
+        if (!force && (elf.getSize() >= size)) {
+            fprintf(stderr, "No gain. Skipping\n");
+        } else if (backup && backup_file(name) != 0) {
+            fprintf(stderr, "Couln't create backup file\n");
+        } else {
+            std::ofstream ofile(name, std::ios::out|std::ios::binary|std::ios::trunc);
+            elf.write(ofile);
+            fprintf(stderr, "Reduced by %d bytes\n", size - elf.getSize());
+        }
+    }
+}
+
+void undo_file(const char *name, bool backup = false)
+{
+    std::ifstream file(name, std::ios::in|std::ios::binary);
+    Elf elf(file);
+    unsigned int size = elf.getSize();
+    fprintf(stderr, "%s: ", name);
+    if (elf.getType() != ET_DYN) {
+        fprintf(stderr, "Not a shared object. Skipping\n");
+        return;
+    }
+
+    ElfSection *data = nullptr, *text = nullptr;
+    for (ElfSection *section = elf.getSection(1); section != nullptr;
+         section = section->getNext()) {
+        if (section->getName() &&
+            (strcmp(section->getName(), elfhack_data) == 0))
+            data = section;
+        if (section->getName() &&
+            (strcmp(section->getName(), elfhack_text) == 0))
+            text = section;
+    }
+
+    if (!data || !text) {
+        fprintf(stderr, "Not elfhacked. Skipping\n");
+        return;
+    }
+    if (data != text->getNext()) {
+        fprintf(stderr, elfhack_data " section not following " elfhack_text ". Skipping\n");
+        return;
+    }
+
+    ElfSegment *first = elf.getSegmentByType(PT_LOAD);
+    ElfSegment *second = elf.getSegmentByType(PT_LOAD, first);
+    ElfSegment *filler = nullptr;
+    // If the second PT_LOAD is a filler from elfhack --fill, check the third.
+    if (second->isElfHackFillerSegment()) {
+        filler = second;
+        second = elf.getSegmentByType(PT_LOAD, filler);
+    }
+    if (second->getFlags() != first->getFlags()) {
+        fprintf(stderr, "Couldn't identify elfhacked PT_LOAD segments. Skipping\n");
+        return;
+    }
+    // Move sections from the second PT_LOAD to the first, and remove the
+    // second PT_LOAD segment.
+    for (std::list<ElfSection *>::iterator section = second->begin();
+         section != second->end(); ++section)
+        first->addSection(*section);
+
+    elf.removeSegment(second);
+    if (filler)
+        elf.removeSegment(filler);
+
+    if (backup && backup_file(name) != 0) {
+        fprintf(stderr, "Couln't create backup file\n");
+    } else {
+        std::ofstream ofile(name, std::ios::out|std::ios::binary|std::ios::trunc);
+        elf.write(ofile);
+        fprintf(stderr, "Grown by %d bytes\n", elf.getSize() - size);
+    }
+}
+
+int main(int argc, char *argv[])
+{
+    int arg;
+    bool backup = false;
+    bool force = false;
+    bool revert = false;
+    bool fill = false;
+    char *lastSlash = rindex(argv[0], '/');
+    if (lastSlash != nullptr)
+        rundir = strndup(argv[0], lastSlash - argv[0]);
+    for (arg = 1; arg < argc; arg++) {
+        if (strcmp(argv[arg], "-f") == 0)
+            force = true;
+        else if (strcmp(argv[arg], "-b") == 0)
+            backup = true;
+        else if (strcmp(argv[arg], "-r") == 0)
+            revert = true;
+        else if (strcmp(argv[arg], "--fill") == 0)
+            fill = true;
+        else if (revert) {
+            undo_file(argv[arg], backup);
+        } else
+            do_file(argv[arg], backup, force, fill);
+    }
+
+    free(rundir);
+    return 0;
+}