[elf] Allow checking for different file types

Previously `elf::file::valid()` only returned true for ELF files of type
`ET_EXEC`, now allow passing in of an expected file type.

src/libraries/elf/file.cpp

@@ -20,22 +20,29 @@ file::file(util::const_buffer data) :
 }
 
 bool
-file::valid() const
+file::valid(elf::filetype type) const
 {
     if (m_data.count < sizeof(file_header))
         return false;
 
     const file_header *fheader = header();
 
-    return
+    bool abi_valid =
         fheader->magic == expected_magic &&
         fheader->word_size == wordsize::bits64 &&
         fheader->endianness == encoding::lsb &&
         fheader->os_abi == osabi::sysV &&
-        fheader->file_type == filetype::executable &&
         fheader->machine_type == machine::x64 &&
         fheader->ident_version == 1 &&
         fheader->version == 1;
+
+    if (!abi_valid)
+        return false;
+
+    if (type != filetype::none && fheader->file_type != type)
+        return false;
+
+    return true;
 }
 
 uintptr_t

src/libraries/elf/include/elf/file.h

@@ -2,6 +2,7 @@
 #include <stddef.h>
 #include <stdint.h>
 
+#include <elf/headers.h>
 #include <util/counted.h>
 #include <util/pointers.h>
 
@@ -42,8 +43,9 @@ public:
     file(util::const_buffer data);
 
     /// Check the validity of the ELF data
-    /// \returns  true for valid ELF data
-    bool valid() const;
+    /// \arg type  Expected file type of the data
+    /// \returns   true for valid ELF data
+    bool valid(elf::filetype type = elf::filetype::executable) const;
 
     /// Get the entrypoint address of the program image
     /// \returns  A pointer to the entrypoint of the program
@@ -60,10 +62,14 @@ public:
     /// Get the ELF section headers
     inline const subheaders<section_header> & sections() const { return m_sections; }
 
+    /// Get the ELF file header
     inline const file_header * header() const {
         return reinterpret_cast<const file_header *>(m_data.pointer);
     }
 
+    /// Get the ELF file type from the header
+    inline filetype type() const { return header()->file_type; }
+
 private:
     subheaders<segment_header> m_segments;
     subheaders<section_header> m_sections;