DynamicLoader+LibELF: Move self-relocation code into a separate file

Userland/DynamicLoader/main.cpp

@@ -8,6 +8,7 @@
 #include <LibC/unistd.h>
 #include <LibELF/AuxiliaryVector.h>
 #include <LibELF/DynamicLinker.h>
+#include <LibELF/Relocation.h>
 
 char* __static_environ[] = { nullptr }; // We don't get the environment without some libc workarounds..
 
@@ -35,52 +36,8 @@ static void perform_self_relocations(auxv_t* auxvp)
         }
     }
     VERIFY(found_base_address);
-    ElfW(Ehdr)* header = (ElfW(Ehdr)*)(base_address);
+    if (!ELF::perform_relative_relocations(base_address))
-    ElfW(Phdr)* pheader = (ElfW(Phdr)*)(base_address + header->e_phoff);
-    FlatPtr dynamic_section_addr = 0;
-    for (size_t i = 0; i < (size_t)header->e_phnum; ++i, ++pheader) {
-        if (pheader->p_type != PT_DYNAMIC)
-            continue;
-        dynamic_section_addr = pheader->p_vaddr + base_address;
-    }
-    if (!dynamic_section_addr)
         exit(1);
-
-    FlatPtr relocation_section_addr = 0;
-    size_t relocation_table_size = 0;
-    size_t relocation_count = 0;
-    bool use_addend = false;
-    auto* dyns = reinterpret_cast<const ElfW(Dyn)*>(dynamic_section_addr);
-    for (unsigned i = 0;; ++i) {
-        auto& dyn = dyns[i];
-        if (dyn.d_tag == DT_NULL)
-            break;
-        if (dyn.d_tag == DT_RELA)
-            use_addend = true;
-        if (dyn.d_tag == DT_REL || dyn.d_tag == DT_RELA)
-            relocation_section_addr = base_address + dyn.d_un.d_ptr;
-        else if (dyn.d_tag == DT_RELCOUNT || dyn.d_tag == DT_RELACOUNT)
-            relocation_count = dyn.d_un.d_val;
-        else if (dyn.d_tag == DT_RELSZ || dyn.d_tag == DT_RELASZ)
-            relocation_table_size = dyn.d_un.d_val;
-    }
-    if (!relocation_section_addr || !relocation_table_size || !relocation_count)
-        exit(1);
-
-    auto relocation_entry_size = relocation_table_size / relocation_count;
-    for (unsigned i = 0; i < relocation_count; ++i) {
-        size_t offset_in_section = i * relocation_entry_size;
-        auto* relocation = (ElfW(Rela)*)(relocation_section_addr + offset_in_section);
-#if ARCH(I386)
-        VERIFY(ELF32_R_TYPE(relocation->r_info) == R_386_RELATIVE);
-#else
-        VERIFY(ELF64_R_TYPE(relocation->r_info) == R_X86_64_RELATIVE);
-#endif
-        if (use_addend)
-            *(FlatPtr*)(base_address + relocation->r_offset) = base_address + relocation->r_addend;
-        else
-            *(FlatPtr*)(base_address + relocation->r_offset) += base_address;
-    }
 }
 
 static void display_help()

Userland/Libraries/LibC/elf.h

@@ -33,6 +33,7 @@
 #pragma once
 
 #ifndef KERNEL
+#    include <stdint.h>
 #    include <sys/types.h>
 #else
 #    include <AK/Types.h>

Userland/Libraries/LibELF/Relocation.cpp

@@ -0,0 +1,64 @@
+/*
+ * Copyright (c) 2021, Gunnar Beutner <gbeutner@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibC/elf.h>
+#include <LibELF/Relocation.h>
+
+namespace ELF {
+
+bool perform_relative_relocations(FlatPtr base_address)
+{
+
+    ElfW(Ehdr)* header = (ElfW(Ehdr)*)(base_address);
+    ElfW(Phdr)* pheader = (ElfW(Phdr)*)(base_address + header->e_phoff);
+    FlatPtr dynamic_section_addr = 0;
+    for (size_t i = 0; i < (size_t)header->e_phnum; ++i, ++pheader) {
+        if (pheader->p_type != PT_DYNAMIC)
+            continue;
+        dynamic_section_addr = pheader->p_vaddr + base_address;
+    }
+    if (!dynamic_section_addr)
+        return false;
+
+    FlatPtr relocation_section_addr = 0;
+    size_t relocation_table_size = 0;
+    size_t relocation_count = 0;
+    bool use_addend = false;
+    auto* dyns = reinterpret_cast<const ElfW(Dyn)*>(dynamic_section_addr);
+    for (unsigned i = 0;; ++i) {
+        auto& dyn = dyns[i];
+        if (dyn.d_tag == DT_NULL)
+            break;
+        if (dyn.d_tag == DT_RELA)
+            use_addend = true;
+        if (dyn.d_tag == DT_REL || dyn.d_tag == DT_RELA)
+            relocation_section_addr = base_address + dyn.d_un.d_ptr;
+        else if (dyn.d_tag == DT_RELCOUNT || dyn.d_tag == DT_RELACOUNT)
+            relocation_count = dyn.d_un.d_val;
+        else if (dyn.d_tag == DT_RELSZ || dyn.d_tag == DT_RELASZ)
+            relocation_table_size = dyn.d_un.d_val;
+    }
+    if (!relocation_section_addr || !relocation_table_size || !relocation_count)
+        return false;
+
+    auto relocation_entry_size = relocation_table_size / relocation_count;
+    for (unsigned i = 0; i < relocation_count; ++i) {
+        size_t offset_in_section = i * relocation_entry_size;
+        auto* relocation = (ElfW(Rela)*)(relocation_section_addr + offset_in_section);
+#if ARCH(I386)
+        VERIFY(ELF32_R_TYPE(relocation->r_info) == R_386_RELATIVE);
+#else
+        VERIFY(ELF64_R_TYPE(relocation->r_info) == R_X86_64_RELATIVE);
+#endif
+        if (use_addend)
+            *(FlatPtr*)(base_address + relocation->r_offset) = base_address + relocation->r_addend;
+        else
+            *(FlatPtr*)(base_address + relocation->r_offset) += base_address;
+    }
+
+    return true;
+}
+}

Userland/Libraries/LibELF/Relocation.h

@@ -0,0 +1,18 @@
+/*
+ * Copyright (c) 2021, Gunnar Beutner <gbeutner@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Concepts.h>
+#include <AK/String.h>
+#include <AK/Vector.h>
+#include <Kernel/VirtualAddress.h>
+
+namespace ELF {
+
+bool perform_relative_relocations(FlatPtr base_address);
+
+}