1 files changed, 63 insertions, 0 deletions
diff --git a/source/elfload.cpp b/source/elfload.cpp
new file mode 100644
index 0000000..a430ad2
--- /dev/null
+++ b/source/elfload.cpp
@@ -0,0 +1,63 @@
+/**
+ * @file elfload.cpp
+ * @brief Loads ELF binary data into memory for execution.
+ *
+ * Copyright (C) 2021 Clyne Sullivan
+ *
+ * Distributed under the GNU GPL v3 or later. You should have received a copy of
+ * the GNU General Public License along with this program.
+ * If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include "elfload.hpp"
+#include "elf.h"
+
+#include <algorithm>
+#include <cstring>
+
+__attribute__((section(".convdata")))
+ELFManager::EntryFunc ELFManager::m_entry = nullptr;
+std::array<unsigned char, MAX_ELF_FILE_SIZE> ELFManager::m_file_buffer = {};
+
+static const unsigned char elf_header[] = { '\177', 'E', 'L', 'F' };
+
+template<typename T>
+constexpr static auto ptr_from_offset(void *base, uint32_t offset)
+{
+    return reinterpret_cast<T>(reinterpret_cast<uint8_t *>(base) + offset);
+}
+
+ELFManager::EntryFunc ELFManager::loadFromInternalBuffer()
+{
+    auto elf_data = m_file_buffer.data();
+
+    // Check the ELF's header signature
+    auto ehdr = reinterpret_cast<Elf32_Ehdr *>(elf_data);
+    if (!std::equal(ehdr->e_ident, ehdr->e_ident + 4, elf_header))
+        return nullptr;
+
+    // Iterate through program header LOAD sections
+    bool loaded = false;
+    auto phdr = ptr_from_offset<Elf32_Phdr *>(elf_data, ehdr->e_phoff);
+    for (Elf32_Half i = 0; i < ehdr->e_phnum; i++) {
+        if (phdr->p_type == PT_LOAD) {
+            if (phdr->p_filesz == 0) {
+                std::memset(reinterpret_cast<void *>(phdr->p_vaddr),
+                            0,
+                            phdr->p_memsz);
+            } else {
+                std::memcpy(reinterpret_cast<void *>(phdr->p_vaddr),
+                            ptr_from_offset<void *>(elf_data, phdr->p_offset),
+                            phdr->p_filesz);
+                if (!loaded)
+                    loaded = true;
+            }
+        }
+
+        phdr = ptr_from_offset<Elf32_Phdr *>(phdr, ehdr->e_phentsize);
+    }
+
+
+    return loaded ? reinterpret_cast<ELFManager::EntryFunc>(ehdr->e_entry) : nullptr;
+}
+