package: skip strip on signed kernel modules

Executing strip action on kernel modules removes the signature.
Is not possible to strip and keep the signature, therefore avoid
strip signed kernel modules.

(From OE-Core rev: 4c47e5f171fa2603355e2f9183065ce8137a18c7)

Signed-off-by: Omar Ocampo <omar.ocampo.coronado@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oe/package.py

@@ -21,11 +21,15 @@ def runstrip(arg):
         os.chmod(file, newmode)
 
     stripcmd = [strip]
-
+    skip_strip = False
     # kernel module    
     if elftype & 16:
-        stripcmd.extend(["--strip-debug", "--remove-section=.comment",
-            "--remove-section=.note", "--preserve-dates"])
+        if is_kernel_module_signed(file):
+            bb.debug(1, "Skip strip on signed module %s" % file)
+            skip_strip = True
+        else:
+            stripcmd.extend(["--strip-debug", "--remove-section=.comment",
+                "--remove-section=.note", "--preserve-dates"])
     # .so and shared library
     elif ".so" in file and elftype & 8:
         stripcmd.extend(["--remove-section=.comment", "--remove-section=.note", "--strip-unneeded"])
@@ -36,7 +40,8 @@ def runstrip(arg):
     stripcmd.append(file)
     bb.debug(1, "runstrip: %s" % stripcmd)
 
-    output = subprocess.check_output(stripcmd, stderr=subprocess.STDOUT)
+    if not skip_strip:
+        output = subprocess.check_output(stripcmd, stderr=subprocess.STDOUT)
 
     if newmode:
         os.chmod(file, origmode)
@@ -46,6 +51,13 @@ def is_kernel_module(path):
     with open(path) as f:
         return mmap.mmap(f.fileno(), 0, prot=mmap.PROT_READ).find(b"vermagic=") >= 0
 
+# Detect if .ko module is signed
+def is_kernel_module_signed(path):
+    with open(path, "rb") as f:
+        f.seek(-28, 2)
+        module_tail = f.read()
+        return "Module signature appended" in "".join(chr(c) for c in bytearray(module_tail))
+
 # Return type (bits):
 # 0 - not elf
 # 1 - ELF