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LibELF: Add support for loading objects with multiple data and text segments

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This enables loading executables with multiple data and text segments. Also
it fixes loading executables where the text segment has a non-zero offset.

Example:

  $ echo "main () {}" > test.c
  $ gcc -Wl,-z,separate-code -o test test.c
  $ objdump -p test
  test:     file format elf32-i386

  Program Header:
      PHDR off    0x00000034 vaddr 0x00000034 paddr 0x00000034 align 2**2
           filesz 0x000000e0 memsz 0x000000e0 flags r--
    INTERP off    0x00000114 vaddr 0x00000114 paddr 0x00000114 align 2**0
           filesz 0x00000013 memsz 0x00000013 flags r--
      LOAD off    0x00000000 vaddr 0x00000000 paddr 0x00000000 align 2**12
           filesz 0x000003c4 memsz 0x000003c4 flags r--
      LOAD off    0x00001000 vaddr 0x00001000 paddr 0x00001000 align 2**12
           filesz 0x00000279 memsz 0x00000279 flags r-x
      LOAD off    0x00002000 vaddr 0x00002000 paddr 0x00002000 align 2**12
           filesz 0x00000004 memsz 0x00000004 flags r--
      LOAD off    0x00002004 vaddr 0x00003004 paddr 0x00003004 align 2**12
           filesz 0x00000100 memsz 0x00000124 flags rw-
   DYNAMIC off    0x00002014 vaddr 0x00003014 paddr 0x00003014 align 2**2
           filesz 0x000000c8 memsz 0x000000c8 flags rw-
This commit is contained in:
Gunnar Beutner 2021-04-13 19:31:34 +02:00 • committed by Andreas Kling
parent c3ee70591a
commit cd7512a2ad
4 changed files with 121 additions and 77 deletions
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23
Userland/Libraries/LibELF/DynamicLoader.h
View file

@ -38,6 +38,22 @@
namespace ELF {
class LoadedSegment {
public:
LoadedSegment(VirtualAddress address, size_t size)
: m_address(address)
, m_size(size)
{
}
VirtualAddress address() const { return m_address; }
size_t size() const { return m_size; }
private:
VirtualAddress m_address;
size_t m_size;
};
class DynamicLoader : public RefCounted<DynamicLoader> {
public:
static RefPtr<DynamicLoader> try_create(int fd, String filename);
@ -74,7 +90,8 @@ public:
template<typename F>
void for_each_needed_library(F) const;
VirtualAddress text_segment_load_address() const { return m_text_segment_load_address; }
VirtualAddress base_address() const { return m_base_address; }
const Vector<LoadedSegment> text_segments() const { return m_text_segments; }
bool is_dynamic() const { return m_elf_image.is_dynamic(); }
static Optional<DynamicObject::SymbolLookupResult> lookup_symbol(const ELF::DynamicObject::Symbol&);
@ -141,8 +158,8 @@ private:
RefPtr<DynamicObject> m_dynamic_object;
VirtualAddress m_text_segment_load_address;
size_t m_text_segment_size { 0 };
VirtualAddress m_base_address;
Vector<LoadedSegment> m_text_segments;
VirtualAddress m_relro_segment_address;
size_t m_relro_segment_size { 0 };