Examples with ElfSection com.facebook.buck.cxx.elf.ElfSection used on opensource projects

Example 1 with ElfSection

use of com.facebook.buck.cxx.elf.ElfSection in project buck by facebook.

the class AbstractElfDynamicSectionScrubberStep method execute.

@Override
public StepExecutionResult execute(ExecutionContext context) throws IOException {
    try (FileChannel channel = FileChannel.open(getFilesystem().resolve(getPath()), StandardOpenOption.READ, StandardOpenOption.WRITE)) {
        MappedByteBuffer buffer = channel.map(READ_WRITE, 0, channel.size());
        Elf elf = new Elf(buffer);
        Optional<ElfSection> section = elf.getSectionByName(SECTION).map(Pair::getSecond);
        if (!section.isPresent()) {
            throw new IOException(String.format("Error parsing ELF file %s: no such section \"%s\"", getPath(), SECTION));
        }
        for (ByteBuffer body = section.get().body; body.hasRemaining(); ) {
            ElfDynamicSection.DTag dTag = ElfDynamicSection.DTag.valueOf(elf.header.ei_class == ElfHeader.EIClass.ELFCLASS32 ? Elf.Elf32.getElf32Sword(body) : (int) Elf.Elf64.getElf64Sxword(body));
            if (!WHITELISTED_TAGS.contains(dTag)) {
                if (elf.header.ei_class == ElfHeader.EIClass.ELFCLASS32) {
                    // d_ptr
                    Elf.Elf32.putElf32Addr(body, 0);
                } else {
                    // d_ptr
                    Elf.Elf64.putElf64Addr(body, 0);
                }
            } else {
                if (elf.header.ei_class == ElfHeader.EIClass.ELFCLASS32) {
                    // d_ptr
                    Elf.Elf32.getElf32Addr(body);
                } else {
                    // d_ptr
                    Elf.Elf64.getElf64Addr(body);
                }
            }
        }
    }
    return StepExecutionResult.SUCCESS;
}

Example 2 with ElfSection

use of com.facebook.buck.cxx.elf.ElfSection in project buck by facebook.

the class AbstractElfExtractSectionsStep method getNewSectionAddresses.

// We want to compact the sections into the new ELF file, so find out the new addresses of each
// section.
private ImmutableMap<String, Long> getNewSectionAddresses() throws IOException {
    ImmutableMap.Builder<String, Long> addresses = ImmutableMap.builder();
    try (FileChannel channel = FileChannel.open(getFilesystem().resolve(getInput()), StandardOpenOption.READ)) {
        MappedByteBuffer buffer = channel.map(READ_ONLY, 0, channel.size());
        Elf elf = new Elf(buffer);
        // We start placing sections right after the program headers.
        long end = elf.header.e_phoff + elf.header.e_phnum * elf.header.e_phentsize;
        for (int index = 0; index < elf.getNumberOfSections(); index++) {
            ElfSection section = elf.getSectionByIndex(index);
            String name = elf.getSectionName(section.header);
            // address by this sections size.
            if (getSections().contains(name)) {
                addresses.put(name, end);
                end += section.header.sh_size;
            }
        }
    }
    return addresses.build();
}

Example 3 with ElfSection

use of com.facebook.buck.cxx.elf.ElfSection in project buck by facebook.

the class AbstractElfSymbolTableScrubberStep method execute.

@Override
public StepExecutionResult execute(ExecutionContext context) throws IOException {
    try (FileChannel channel = FileChannel.open(getFilesystem().resolve(getPath()), StandardOpenOption.READ, StandardOpenOption.WRITE)) {
        MappedByteBuffer buffer = channel.map(READ_WRITE, 0, channel.size());
        Elf elf = new Elf(buffer);
        // Locate the symbol table section.
        Optional<ElfSection> section = elf.getSectionByName(getSection()).map(Pair::getSecond);
        if (!section.isPresent()) {
            if (isAllowMissing()) {
                return StepExecutionResult.SUCCESS;
            } else {
                throw new IOException(String.format("Error parsing ELF file %s: no such section \"%s\"", getPath(), getSection()));
            }
        }
        // Read in and fixup the symbol table then write it back out.
        ElfSymbolTable table = ElfSymbolTable.parse(elf.header.ei_class, section.get().body);
        ElfSymbolTable fixedUpTable = fixUpSymbolTable(table);
        Preconditions.checkState(table.entries.size() == fixedUpTable.entries.size());
        section.get().body.rewind();
        fixedUpTable.write(elf.header.ei_class, section.get().body);
    }
    return StepExecutionResult.SUCCESS;
}

Example 4 with ElfSection

use of com.facebook.buck.cxx.elf.ElfSection in project buck by facebook.

the class DebugSectionFinder method findElf.

// Locate, if any, the debug sections in the ELF file represented by the given buffer.
private ImmutableMap<String, DebugSection> findElf(ByteBuffer buffer) {
    ImmutableMap.Builder<String, DebugSection> debugSectionsBuilder = ImmutableMap.builder();
    Elf elf = new Elf(buffer);
    for (int i = 0; i < elf.getNumberOfSections(); i++) {
        ElfSection section = elf.getSectionByIndex(i);
        String name = elf.getSectionName(section.header);
        ImmutableSet<DebugSectionProperty> properties = ELF_DEBUG_SECTIONS.get(name);
        if (properties != null) {
            buffer.position((int) section.header.sh_off);
            ByteBuffer body = buffer.slice();
            body.limit((int) section.header.sh_size);
            debugSectionsBuilder.put(name, new DebugSection(properties, body));
        }
    }
    return debugSectionsBuilder.build();
}

Example 5 with ElfSection

use of com.facebook.buck.cxx.elf.ElfSection in project buck by facebook.

the class ElfDynamicSectionScrubberStepTest method test.

@Test
public void test() throws IOException {
    ProjectWorkspace workspace = TestDataHelper.createProjectWorkspaceForScenario(this, "elf_shared_lib", tmp);
    workspace.setUp();
    ElfDynamicSectionScrubberStep step = ElfDynamicSectionScrubberStep.of(new ProjectFilesystem(tmp.getRoot()), tmp.getRoot().getFileSystem().getPath("libfoo.so"));
    step.execute(TestExecutionContext.newInstance());
    // Verify that the relevant dynamic section tag have been zero'd out.
    try (FileChannel channel = FileChannel.open(step.getFilesystem().resolve(step.getPath()), StandardOpenOption.READ)) {
        MappedByteBuffer buffer = channel.map(READ_ONLY, 0, channel.size());
        Elf elf = new Elf(buffer);
        Optional<ElfSection> section = elf.getSectionByName(ElfDynamicSectionScrubberStep.SECTION).map(Pair::getSecond);
        for (ByteBuffer body = section.get().body; body.hasRemaining(); ) {
            ElfDynamicSection.DTag dTag = ElfDynamicSection.DTag.valueOf(elf.header.ei_class == ElfHeader.EIClass.ELFCLASS32 ? Elf.Elf32.getElf32Sword(body) : (int) Elf.Elf64.getElf64Sxword(body));
            long dPtr = elf.header.ei_class == ElfHeader.EIClass.ELFCLASS32 ? Elf.Elf32.getElf32Addr(body) : Elf.Elf64.getElf64Addr(body);
            if (!ElfDynamicSectionScrubberStep.WHITELISTED_TAGS.contains(dTag)) {
                assertThat(dPtr, Matchers.equalTo(0L));
            }
        }
    }
}