From 33ea53094cc1f34c27ca295472f01f8dd09a300b Mon Sep 17 00:00:00 2001
From: bunnei <bunneidev@gmail.com>
Date: Thu, 5 Oct 2017 23:30:08 -0400
Subject: loader: Add support for NRO, as well as various fixes and shared
 linker.

---
 src/core/loader/linker.cpp | 151 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 151 insertions(+)
 create mode 100644 src/core/loader/linker.cpp

(limited to 'src/core/loader/linker.cpp')

diff --git a/src/core/loader/linker.cpp b/src/core/loader/linker.cpp
new file mode 100644
index 000000000..a265b9315
--- /dev/null
+++ b/src/core/loader/linker.cpp
@@ -0,0 +1,151 @@
+// Copyright 2017 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include <vector>
+
+#include "common/common_funcs.h"
+#include "common/logging/log.h"
+#include "common/swap.h"
+#include "core/loader/linker.h"
+#include "core/memory.h"
+
+namespace Loader {
+
+enum class RelocationType : u32 { ABS64 = 257, GLOB_DAT = 1025, JUMP_SLOT = 1026, RELATIVE = 1027 };
+
+enum DynamicType : u32 {
+    DT_NULL = 0,
+    DT_PLTRELSZ = 2,
+    DT_STRTAB = 5,
+    DT_SYMTAB = 6,
+    DT_RELA = 7,
+    DT_RELASZ = 8,
+    DT_STRSZ = 10,
+    DT_JMPREL = 23,
+};
+
+struct Elf64_Rela {
+    u64_le offset;
+    RelocationType type;
+    u32_le symbol;
+    s64_le addend;
+};
+static_assert(sizeof(Elf64_Rela) == 0x18, "Elf64_Rela has incorrect size.");
+
+struct Elf64_Dyn {
+    u64_le tag;
+    u64_le value;
+};
+static_assert(sizeof(Elf64_Dyn) == 0x10, "Elf64_Dyn has incorrect size.");
+
+struct Elf64_Sym {
+    u32_le name;
+    INSERT_PADDING_BYTES(0x2);
+    u16_le shndx;
+    u64_le value;
+    u64_le size;
+};
+static_assert(sizeof(Elf64_Sym) == 0x18, "Elf64_Sym has incorrect size.");
+
+void Linker::WriteRelocations(std::vector<u8>& program_image,
+                                  const std::vector<Symbol>& symbols, u64 relocation_offset,
+                                  u64 size, bool is_jump_relocation, VAddr load_base) {
+    for (u64 i = 0; i < size; i += sizeof(Elf64_Rela)) {
+        Elf64_Rela rela;
+        std::memcpy(&rela, &program_image[relocation_offset + i], sizeof(Elf64_Rela));
+
+        const Symbol& symbol = symbols[rela.symbol];
+        switch (rela.type) {
+        case RelocationType::RELATIVE: {
+            const u64 value = load_base + rela.addend;
+            if (!symbol.name.empty()) {
+                exports[symbol.name] = value;
+            }
+            std::memcpy(&program_image[rela.offset], &value, sizeof(u64));
+            break;
+        }
+        case RelocationType::JUMP_SLOT:
+        case RelocationType::GLOB_DAT:
+            if (!symbol.value) {
+                imports[symbol.name] = {rela.offset + load_base, 0};
+            } else {
+                exports[symbol.name] = symbol.value;
+                std::memcpy(&program_image[rela.offset], &symbol.value, sizeof(u64));
+            }
+            break;
+        case RelocationType::ABS64:
+            if (!symbol.value) {
+                imports[symbol.name] = {rela.offset + load_base, rela.addend};
+            } else {
+                const u64 value = symbol.value + rela.addend;
+                exports[symbol.name] = value;
+                std::memcpy(&program_image[rela.offset], &value, sizeof(u64));
+            }
+            break;
+        default:
+            LOG_CRITICAL(Loader, "Unknown relocation type: %d", rela.type);
+            break;
+        }
+    }
+}
+
+void Linker::Relocate(std::vector<u8>& program_image, u32 dynamic_section_offset,
+                          VAddr load_base) {
+    std::map<u64, u64> dynamic;
+    while (dynamic_section_offset < program_image.size()) {
+        Elf64_Dyn dyn;
+        std::memcpy(&dyn, &program_image[dynamic_section_offset], sizeof(Elf64_Dyn));
+        dynamic_section_offset += sizeof(Elf64_Dyn);
+
+        if (dyn.tag == DT_NULL) {
+            break;
+        }
+        dynamic[dyn.tag] = dyn.value;
+    }
+
+    u64 offset = dynamic[DT_SYMTAB];
+    std::vector<Symbol> symbols;
+    while (offset < program_image.size()) {
+        Elf64_Sym sym;
+        std::memcpy(&sym, &program_image[offset], sizeof(Elf64_Sym));
+        offset += sizeof(Elf64_Sym);
+
+        if (sym.name >= dynamic[DT_STRSZ]) {
+            break;
+        }
+
+        std::string name = reinterpret_cast<char*>(&program_image[dynamic[DT_STRTAB] + sym.name]);
+        if (sym.value) {
+            exports[name] = load_base + sym.value;
+            symbols.emplace_back(std::move(name), load_base + sym.value);
+        } else {
+            symbols.emplace_back(std::move(name), 0);
+        }
+    }
+
+    if (dynamic.find(DT_RELA) != dynamic.end()) {
+        WriteRelocations(program_image, symbols, dynamic[DT_RELA], dynamic[DT_RELASZ], false,
+                         load_base);
+    }
+
+    if (dynamic.find(DT_JMPREL) != dynamic.end()) {
+        WriteRelocations(program_image, symbols, dynamic[DT_JMPREL], dynamic[DT_PLTRELSZ], true,
+                         load_base);
+    }
+}
+
+void Linker::ResolveImports() {
+    // Resolve imports
+    for (const auto& import : imports) {
+        const auto& search = exports.find(import.first);
+        if (search != exports.end()) {
+            Memory::Write64(import.second.ea, search->second + import.second.addend);
+        }
+        else {
+            LOG_ERROR(Loader, "Unresolved import: %s", import.first.c_str());
+        }
+    }
+}
+
+} // namespace Loader
-- 
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