Implemented R_ARM_ABS32 relocation.

README.md

@@ -1,6 +1,8 @@
 # AndroidNativeEmu
+
 Allows you to partly emulate an Android native library.
 
+This is an educational project to learn more about the ELF file format and [Unicorn](https://github.com/unicorn-engine/unicorn).
 
 ## Resources
 
@@ -9,6 +11,8 @@ All resources used while developing AndroidNativeEmu.
 ### Text sources
 - https://greek0.net/elf.html
 - https://stackoverflow.com/questions/13908276/loading-elf-file-in-c-in-user-space
+- https://programtalk.com/python-examples/pyelftools.elftools.elf.relocation.Relocation/
+- http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044f/IHI0044F_aaelf.pdf
 
 ### Code sources
 - https://github.com/lunixbochs/usercorn

androidemu/internal/arm.py

@@ -0,0 +1,6 @@
+# From http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044f/IHI0044F_aaelf.pdf
+
+R_ARM_ABS32 = 2
+R_ARM_GLOB_DAT = 21
+R_ARM_JUMP_SLOT = 22
+R_ARM_RELATIVE = 23

androidemu/internal/modules.py

@@ -1,7 +1,8 @@
 from elftools.elf.elffile import ELFFile
+from elftools.elf.relocation import RelocationSection
 from unicorn import UC_PROT_ALL
 
-from androidemu.internal import get_segment_protection
+from androidemu.internal import get_segment_protection, arm
 
 
 class Module:
@@ -38,10 +39,6 @@ def load_module(self, filename, main=True):
             if not dynamic:
                 raise NotImplementedError("Only ET_DYN is supported at the moment.")
 
-            # Parse section header (Linking view).
-            # for section in elf.iter_sections():
-            #     print(section.name + " " + section.header.sh_type)
-
             # Parse program header (Execution view).
 
             # - LOAD (determinate what parts of the ELF file get mapped into memory)
@@ -80,3 +77,34 @@ def load_module(self, filename, main=True):
                 self.module_main = module
             else:
                 self.modules.append(module)
+
+            # Parse section header (Linking view).
+            dynsym = elf.get_section_by_name(".dynsym")
+            dynstr = elf.get_section_by_name(".dynstr")
+
+            # Relocate.
+            for section in elf.iter_sections():
+                if not isinstance(section, RelocationSection):
+                    continue
+
+                for rel in section.iter_relocations():
+                    sym = dynsym.get_symbol(rel['r_info_sym'])
+                    sym_value = sym['st_value']
+
+                    rel_addr = load_base + rel['r_offset']  # Location where relocation should happen
+
+                    # Relocation table for ARM
+                    if rel.entry.r_info_type == arm.R_ARM_ABS32:  # Static | Data | Op: (S + A) | T
+                        # Create the new value.
+                        value = load_base + sym_value
+
+                        # Write the new value
+                        self.emu.mu.mem_write(rel_addr, value.to_bytes(4, byteorder='little'))
+                    elif rel.entry.r_info_type == arm.R_ARM_GLOB_DAT:  # Dyn | Data | Op: (S + A) | T
+                        pass
+                    elif rel.entry.r_info_type == arm.R_ARM_JUMP_SLOT:  # Dyn | Data | Op: (S + A) | T
+                        pass
+                    elif rel.entry.r_info_type == arm.R_ARM_RELATIVE:  # Dyn | Data | Op: B(S) + A[Note: see Table 4-18]
+                        pass
+                    else:
+                        print("Unhandled relocation type %i." % rel.entry.r_info_type)