1 files changed, 77 insertions, 0 deletions
diff --git a/source/elf_load.cpp b/source/elf_load.cpp
new file mode 100644
index 0000000..661dbc3
--- /dev/null
+++ b/source/elf_load.cpp
@@ -0,0 +1,77 @@
+#include "elf_load.hpp"
+#include "elf_format.hpp"
+
+#include <algorithm>
+#include <cstring>
+
+extern void *elf_load_offset;
+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);
+}
+
+static Elf32_Shdr *find_section(Elf32_Ehdr *ehdr, const char *name);
+
+namespace elf {
+
+entry_t elf_load(void *elf_data)
+{
+    auto ehdr = reinterpret_cast<Elf32_Ehdr *>(elf_data);
+    if (std::equal(ehdr->e_ident, ehdr->e_ident + 4, elf_header))
+        return nullptr;
+
+    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) {
+            std::memcpy(ptr_from_offset<void *>(elf_load_offset, phdr->p_vaddr),
+                        ptr_from_offset<void *>(elf_data, phdr->p_offset),
+                        phdr->p_filesz);
+            //break;
+        }
+    }
+
+    // Zero .bss section
+    if (auto bss_section = find_section(ehdr, ".bss"); bss_section) {
+        auto bss = ptr_from_offset<uint32_t *>(elf_load_offset, bss_section->sh_addr);
+        std::fill(bss, bss + bss_section->sh_size / sizeof(uint32_t), 0);
+    }
+
+    // Fix global offset table (GOT) entries
+    if (auto got_section = find_section(ehdr, ".got"); got_section) {
+        auto got = ptr_from_offset<void **>(elf_load_offset, got_section->sh_addr);
+        for (size_t i = 0; i < got_section->sh_size / sizeof(void *); i++)
+            got[i] = ptr_from_offset<void *>(got[i], reinterpret_cast<uint32_t>(elf_load_offset));
+    }
+
+    //// Run any initial constructors
+    //if (auto init_section = find_section(ehdr, ".init_array"); init_section) {
+    //    auto init_array = reinterpret_cast<void (**)()>(elf_load_offset + init_section->sh_addr);
+    //    std::for_each(init_array, init_array + init_section->sh_size / sizeof(void (*)()),
+    //                  [elf_load_offset](auto func) { (func + elf_load_offset)(); });
+    //}
+
+    return ptr_from_offset<entry_t>(elf_load_offset, ehdr->e_entry);
+}
+
+} // namespace elf
+
+Elf32_Shdr *find_section(Elf32_Ehdr *ehdr, const char *name)
+{
+	auto shdr = ptr_from_offset<Elf32_Shdr *>(ehdr, ehdr->e_shoff);
+	auto shdr_str = ptr_from_offset<Elf32_Shdr *>(ehdr,
+        ehdr->e_shoff + ehdr->e_shstrndx * ehdr->e_shentsize);
+
+	for (Elf32_Half i = 0; i < ehdr->e_shnum; i++) {
+		char *section = ptr_from_offset<char *>(ehdr, shdr_str->sh_offset) + shdr->sh_name;
+		if (!strcmp(section, name))
+			return shdr;
+
+		shdr = ptr_from_offset<Elf32_Shdr *>(shdr, ehdr->e_shentsize);
+	}
+
+	return 0;
+}
+