Use pkg-config.multiarch file to determine architecture

The file contains a GNU Target Triplet string that describes the
sysroot. It is needed for the cross-compilation step so can safely
assume to be available.

Signed-off-by: Louis-Francis Ratté-Boulianne <lfrb@collabora.com>
Reviewed-by: Guillaume Desmottes <guillaume.desmottes@collabora.co.uk>
Differential Revision: https://phabricator.apertis.org/D4916

doc/man/ade-sysroot.1

@@ -115,8 +115,8 @@ Checks a sysroot <archive> file for validity\&.
 .sp
 It makes sure the file is a valid gzip compressed tarball (\&.tar\&.gz) and
 that it contains a valid version file (/etc/image_version)\&. The tool also
-assumes that the \fBls\fR utility will be part of the sysroot as it reads
-its ELF header to determine the architecture\&.
+assumes that the pkg-config\&.multiarch file will be part of the sysroot as
+it uses it to determine the architecture\&.
 .sp
 .RE
 .PP

tools/ade

@@ -85,46 +85,22 @@ class Colors:
         cls.ENDC = '\033[0m'
 
 
-class ELFHeader:
-
-    def __init__(self, data):
-        fields = struct.unpack('<4sBBBBB7sHHI', data[0:24])
-
-        # ELF Magic
-        if fields[0] != b'\x7fELF':
-            raise ValueError("Wrong ELF header magic")
-
-        # Address size (32 or 64 bits)
-        if fields[1] == 1:
-            self.addr_size = 32
-        elif fields[1] == 2:
-            self.addr_size = 64
-        else:
-            raise ValueError("Not supported ELF address size {0}".format(fields[1]))
-
-        # Instruction Set Architecture
-        if fields[8] == 0x28:
-            self.machine = 'arm'
-        elif fields[8] == 0xB7:
-            self.machine = 'aarch64'
-        else:
-            raise ValueError("Not supported machine type: {0}".format(fields[8]))
-
-        if self.addr_size == 32:
-            self.flags, = struct.unpack('<I', data[36:40])
-        elif self.addr_size == 64:
-            self.flags, = struct.unpack('<I', data[48:52])
+class TargetTriplet:
+    SUPPORTED = {
+        'armhf': "arm-linux-gnueabihf",
+        'arm64': "aarch64-linux-gnu"
+    }
+
+    def __init__(self, string):
+        self.triplet = string
+        for arch, triplet in self.SUPPORTED.items():
+            if string == triplet:
+                self.arch = arch
+                return
+        raise NotSupportedError()
 
     def get_architecture(self):
-        if self.machine == 'arm' and self.addr_size == 32:
-            if self.flags & HARD_FLOAT_FLAG:
-                return 'armhf'
-            else:
-                return 'armel'
-        elif self.machine == 'aarch64' and self.addr_size == 64:
-            return 'arm64'
-        else:
-            raise ValueError("Unsupported architecture")
+        return self.arch
 
 
 class SysrootVersion:
@@ -159,8 +135,8 @@ class SysrootVersion:
         try:
             with open(os.path.join(path, 'etc', 'image_version')) as f:
                 self.parse_string(f.read())
-            with open(os.path.join(path, 'bin', 'ls'), 'rb') as f:
-                self.arch = ELFHeader(f.read(64)).get_architecture()
+            with open(os.path.join(path, 'usr', 'lib', 'pkg-config.multiarch')) as f:
+                self.arch = TargetTriplet(f.read().strip()).get_architecture()
         except FileNotFoundError as e:
             if not os.path.exists(path) or not os.listdir(path):
                 raise NotInstalledError
@@ -251,25 +227,25 @@ class SysrootArchive:
                 except Exception as e:
                     raise InvalidSysrootArchiveError('Invalid image_version file in archive')
 
-                # Extract /bin/ls and determine sysroot architecture
-                ls_file = None
-                for path in ['bin/ls', 'binary/bin/ls']:
+                # Extract /usr/lib/pkg-config.multiarch and determine sysroot architecture
+                arch_file = None
+                for path in ['usr/lib/pkg-config.multiarch', 'binary/usr/lib/pkg-config.multiarch']:
                     try:
-                        ls_file = f.getmember(path)
+                        arch_file = f.getmember(path)
                         break
                     except KeyError:
                         continue
-                    if not ls_file:
-                        raise InvalidSysrootArchiveError('Missing ls executable in archive')
+
+                if not arch_file:
+                    raise InvalidSysrootArchiveError('Missing pkg-config.multiarch file in archive')
 
                 try:
-                    with f.extractfile(ls_file) as reader:
-                        header = ELFHeader(reader.read(64))
-                        self.version.arch = header.get_architecture()
+                    with f.extractfile(arch_file) as reader:
+                        self.version.arch = TargetTriplet(reader.read().decode().strip()).get_architecture()
                 except NotSupportedError:
                     raise InvalidSysrootArchiveError('Architecture is not supported')
                 except:
-                    raise InvalidSysrootArchiveError('Invalid ELF header for /bin/ls executable')
+                    raise InvalidSysrootArchiveError('Invalid content in pkg-config.multiarch file')
         except tarfile.ReadError as e:
             raise InvalidSysrootArchiveError(e)