Simple ELF program loader

Now any initrd file is treated like a program image and passed to the
loader to load as a process. Very rudimentary elf loading just allocates
pages, copies sections, and sets the ELF's entrypoint as the RIP to
iretq to.

src/libraries/elf/headers.h

@@ -0,0 +1,98 @@
+#pragma once
+#include <stdint.h>
+#include "kutil/enum_bitfields.h"
+
+namespace elf {
+
+enum class wordsize : uint8_t { invalid, bits32, bits64 };
+enum class encoding : uint8_t { invalid, lsb, msb };
+enum class osabi : uint8_t { sysV, hpux, standalone = 255 };
+enum class machine : uint16_t { none, x64 = 0x3e };
+
+enum class filetype : uint16_t
+{
+	none,
+	relocatable,
+	executable,
+	shared,
+	core
+};
+
+
+struct file_header
+{
+	uint32_t magic;
+
+	wordsize word_size;
+	encoding endianness;
+	uint8_t ident_version;
+	osabi os_abi;
+
+	uint64_t reserved;
+
+	filetype file_type;
+	machine machine_type;
+
+	uint32_t version;
+
+	uint64_t entrypoint;
+	uint64_t ph_offset;
+	uint64_t sh_offset;
+
+	uint32_t flags;
+
+	uint16_t eh_size;
+
+	uint16_t ph_entsize;
+	uint16_t ph_num;
+
+	uint16_t sh_entsize;
+	uint16_t sh_num;
+
+	uint16_t sh_str_idx;
+} __attribute__ ((packed));
+
+
+enum class segment_type : uint32_t { null, load, dynamic, interpreter, note };
+
+struct program_header
+{
+	segment_type type;
+	uint32_t flags;
+	uint64_t offset;
+
+	uint64_t vaddr;
+	uint64_t paddr;
+
+	uint64_t file_size;
+	uint64_t mem_size;
+
+	uint64_t align;
+} __attribute__ ((packed));
+
+
+enum class section_type : uint32_t { null, progbits };
+enum class section_flags : uint64_t
+{
+	write = 0x01,
+	alloc = 0x02,
+	exec  = 0x04,
+};
+
+struct section_header
+{
+	uint32_t name_offset;
+	section_type type;
+	section_flags flags;
+	uint64_t addr;
+	uint64_t offset;
+	uint64_t size;
+	uint32_t link;
+	uint32_t info;
+	uint64_t align;
+	uint64_t entry_size;
+} __attribute__ ((packed));
+
+} // namespace elf
+
+IS_BITFIELD(elf::section_flags);