ldso: check e_machine of ELF binaries

Check if e_machine matches architecture the linker was build for.

repos/base/src/lib/ldso/include/elf.h

@@ -112,9 +112,13 @@ namespace Linker {
 	/**
 	 * Legal values for e_machine (architecture)
 	 */
-	enum {
+	enum Em_machine {
 		EM_NONE    = 0,   /* no machine */
-		EM_386  = 3,   /* intel 80386 */
+		EM_386     = 3,   /* x86_32     */
+		EM_ARM     = 40,  /* arm_v6/7   */
+		EM_X86_64  = 62,  /* x86_64     */
+		EM_AARCH64 = 183, /* arm_v8     */
+		EM_RISCV   = 243, /* riscv      */
 	};
 
 	/**

repos/base/src/lib/ldso/include/file.h

@@ -34,6 +34,11 @@ namespace Linker {
 
 	static inline bool is_rw(Elf::Phdr const &ph) {
 		return ((ph.p_flags & PF_MASK) == (PF_R | PF_W)); }
+
+	/**
+	 * Returns machine linker is compiled for
+	 */
+	Elf::Half machine();
 }
 
 
@@ -154,6 +159,18 @@ struct Linker::Elf_file : File
 		start = 0;
 	}
 
+	char const * _machine(Elf::Half machine)
+	{
+		switch (machine) {
+		case EM_386:     return "x86_32";
+		case EM_ARM:     return "arm";
+		case EM_X86_64:  return "x86_64";
+		case EM_AARCH64: return "aarch64";
+		case EM_RISCV:   return "riscv";
+		default:         return "unknown";
+		}
+	}
+
 	Elf_file(Env &env, Allocator &md_alloc, Name const &name, bool load)
 	:
 		env(env), rom_cap(_rom_dataspace(name)), loaded(load)
@@ -193,6 +210,14 @@ struct Linker::Elf_file : File
 			return false;
 		}
 
+		/* check if machine matches linker's machine */
+		if (ehdr.e_machine != Linker::machine()) {
+			error("LD: incompatbile machine in ELF ('",
+			       _machine(ehdr.e_machine), "'), expected '",
+			       _machine(Linker::machine()), "'");
+			return false;
+		}
+
 		if (ehdr.e_ident[EI_CLASS] != ELFCLASS) {
 			error("LD: support for 32/64-bit objects only");
 			return false;

repos/base/src/lib/ldso/main.cc

@@ -75,6 +75,8 @@ Genode::Mutex &Linker::shared_object_mutex()
 	return _mutex;
 }
 
+Elf::Half Linker::machine() { return E_MACHINE; };
+
 
 /**************************************************************
  ** ELF object types (shared object, dynamic binaries, ldso  **

repos/base/src/lib/ldso/spec/arm/relocation.h

@@ -18,6 +18,9 @@
 #include <dynamic_generic.h>
 
 namespace Linker {
+
+	static constexpr Elf::Half E_MACHINE = EM_ARM;
+
 	enum Reloc_types {
 		R_ABS32    = 2,
 		R_REL32    = 3,

repos/base/src/lib/ldso/spec/arm_64/relocation.h

@@ -20,6 +20,8 @@
 
 namespace Linker {
 
+	static constexpr Elf::Half E_MACHINE = EM_AARCH64;
+
 /**
  * Relocation types
  */

repos/base/src/lib/ldso/spec/riscv/relocation.h

@@ -18,6 +18,8 @@
 
 namespace Linker {
 
+	static constexpr Elf::Half E_MACHINE = EM_RISCV;
+
 	inline unsigned long dynamic_address()
 	{
 		unsigned long addr;

repos/base/src/lib/ldso/spec/x86_32/relocation.h

@@ -19,6 +19,8 @@
 
 namespace Linker {
 
+	static constexpr Elf::Half E_MACHINE = EM_386;
+
 	enum Reloc_types {
 		R_32       = 1,
 		R_COPY     = 5,

repos/base/src/lib/ldso/spec/x86_64/relocation.h

@@ -19,6 +19,8 @@
 
 namespace Linker {
 
+	static constexpr Elf::Half E_MACHINE = EM_X86_64;
+
 /**
  * Relocation types
  */