From 11813469f7d19927e0f2f1d6ad6629ca9c551e29 Mon Sep 17 00:00:00 2001
From: Nathan Giddings <nathang567@gmail.com>
Date: Wed, 9 Dec 2020 05:07:12 -0600
Subject: [PATCH] Re-added (bare bones) ELF program loader

---
 src/elf.cpp |  44 ++++++++++++++++
 src/elf.hpp | 142 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 186 insertions(+)
 create mode 100644 src/elf.cpp
 create mode 100644 src/elf.hpp

diff --git a/src/elf.cpp b/src/elf.cpp
new file mode 100644
index 0000000..e327acf
--- /dev/null
+++ b/src/elf.cpp
@@ -0,0 +1,44 @@
+#include "elf.hpp"
+#include "util.hpp"
+
+kernel::ELF::ELF()
+{
+    this->m_fileLocation = (void*) NULL;
+}
+
+kernel::ELF::ELF(void* location)
+{
+    this->m_fileLocation = location;
+}
+
+void* kernel::ELF::entry()
+{
+    Header* fileHeader = (Header*) m_fileLocation;
+    return fileHeader->entry;
+}
+
+int kernel::ELF::validate()
+{
+    Header* fileHeader = (Header*) m_fileLocation;
+    if(fileHeader->magic != 0x464c457f)
+        return -1;
+    else if((ISA) fileHeader->machine != HOST_ISA)
+        return -1;
+    else if((Endianness) fileHeader->endianness != Little)
+        return -1;
+    return 0;
+}
+
+int kernel::ELF::load()
+{
+    Header* fileHeader = (Header*) m_fileLocation;
+    ProgramHeader* programHeader = (ProgramHeader*) ((size_t) m_fileLocation + fileHeader->phoffset);
+    int count = (int) fileHeader->phcount;
+    for(int i = 0; i < count; i++)
+    {
+        if((SegmentType) programHeader->type != Load)
+            continue;
+        memcpy(programHeader->vaddr, m_fileLocation + programHeader->offset, programHeader->filesize);
+    }
+    return 0;
+}
\ No newline at end of file
diff --git a/src/elf.hpp b/src/elf.hpp
new file mode 100644
index 0000000..341296c
--- /dev/null
+++ b/src/elf.hpp
@@ -0,0 +1,142 @@
+#ifndef ELF_H
+#define ELF_H
+
+#include "systypes.hpp"
+
+namespace kernel
+{
+
+class ELF
+{
+public:
+
+    enum Endianness
+    {
+        Little = 1,
+        Big = 2
+    };
+
+    enum ISA
+    {
+        NA = 0x00,
+        x86 = 0x03,
+        MIPS = 0x08,
+        PPC = 0x14,
+        PPC64 = 0x15,
+        ARM = 0x28,
+        x86_64 = 0x3E,
+        aarch64 = 0xB7
+    };
+
+    enum SegmentType
+    {
+        Unused = 0,
+        Load = 1,
+        Dynamic = 2
+    };
+
+    struct Header
+    {
+        uint32_t magic;
+        char size;
+        char endianness;
+        char version;
+        char abi;
+        char abiVersion;
+        char reserved[7];
+        uint16_t type;
+        uint16_t machine;
+        uint32_t _version;
+        void* entry;
+#if defined __i386__ || defined __arm__
+        uint32_t phoffset;
+        uint32_t shoffset;
+#elif defined __x86_64__ || defined __aarch64__
+        uint64_t phoffset;
+        uint64_t shoffset;
+#endif
+        uint32_t flags;
+        uint16_t headerSize;
+        uint16_t phsize;
+        uint16_t phcount;
+        uint16_t shsize;
+        uint16_t shcount;
+        uint16_t shstrndx;
+    };
+
+    struct ProgramHeader
+    {
+        uint32_t type;
+#if defined __i386__ || defined __arm__
+        uint32_t offset;
+        void* vaddr;
+        physaddr_t paddr;
+        uint32_t filesize;
+        uint32_t memsize;
+        uint32_t flags;
+        uint32_t align;
+#elif defined __x86_64__ || defined __aarch64__
+        uint32_t flags;
+        uint64_t offset;
+        void* vaddr;
+        physaddr_t paddr;
+        uint64_t filesize;
+        uint64_t memsize;
+        uint64_t align;
+#endif
+    };
+
+    struct SectionHeader
+    {
+        uint32_t name;
+        uint32_t type;
+#if defined __i386__ || defined __arm__
+        uint32_t flags;
+        void* addr;
+        uint32_t offset;
+        uint32_t size;
+        uint32_t link;
+        uint32_t info;
+        uint32_t align;
+        uint32_t entrysize;
+#elif defined __x86_64__ || defined __aarch64__
+        uint64_t flags;
+        void* addr;
+        uint64_t offset;
+        uint64_t size;
+        uint32_t link;
+        uint32_t info;
+        uint64_t align;
+        uint64_t entrysize;
+#endif
+    };
+
+#if defined __i386__
+    static const ISA HOST_ISA = x86;
+#elif defined __x86_64__
+    static const ISA HOST_ISA = x86_64;
+#elif defined __arm__
+    static const ISA HOST_ISA = ARM;
+#elif defined __aarch64__
+    static const ISA HOST_ISA = aarch64;
+#endif
+
+    ELF();
+
+    ELF(void* location);
+
+    void* entry();
+
+    int validate();
+
+    int load();
+
+private:
+
+    void* m_fileLocation;
+
+};
+
+}
+
+#endif
\ No newline at end of file