elf: add elf_memory_image

Used to encapsulate an already-loaded image, for providing symbols to later
objects.

elf.cc

@@ -24,6 +24,15 @@ namespace elf {
 	load_program_headers();
     }
 
+    elf_memory_image::elf_memory_image(void* base)
+    {
+        set_base(base);
+        _ehdr = *static_cast<Elf64_Ehdr*>(base);
+        auto p = static_cast<Elf64_Phdr*>(base + _ehdr.e_phoff);
+        assert(_ehdr.e_phentsize == sizeof(*p));
+        _phdrs.assign(p, p + _ehdr.e_phnum);
+    }
+
     void elf_file::load_elf_header()
     {
 	_f.read(&_ehdr, 0, sizeof(_ehdr));

elf.hh

@@ -233,6 +233,11 @@ namespace elf {
         ::file& _f;
     };
 
+    class elf_memory_image : public elf_object {
+    public:
+        explicit elf_memory_image(void* base);
+    };
+
 }
 
 void load_elf(file& f, void* addr = reinterpret_cast<void*>(64 << 20));