Let extract_kernel return full kernel release.

Also add relevant soong rules for genrules to use it.

Test: use it in GKI APEX
Bug: 161563386
Change-Id: I04f80ba91748ee5783088d4e20e6438418863f62

tools/Android.bp

@@ -56,3 +56,23 @@ python_test_host {
   test_config: "post_process_props_unittest.xml",
   test_suites: ["general-tests"],
 }
+
+python_binary_host {
+  name: "extract_kernel",
+  srcs: ["extract_kernel.py"],
+  version: {
+    py2: {
+      enabled: true,
+    },
+    py3: {
+      enabled: false,
+    },
+  },
+}
+
+genrule_defaults {
+  name: "extract_kernel_release_defaults",
+  tools: ["extract_kernel", "lz4"],
+  out: ["kernel_release.txt"],
+  cmd: "$(location) --tools lz4:$(location lz4) --input $(in) --output-release > $(out)"
+}

tools/extract_kernel.py

@@ -40,10 +40,10 @@ COMPRESSION_ALGO = (
 # LINUX_COMPILE_HOST ") (" LINUX_COMPILER ") " UTS_VERSION "\n";
 LINUX_BANNER_PREFIX = b'Linux version '
 LINUX_BANNER_REGEX = LINUX_BANNER_PREFIX + \
-    r'([0-9]+[.][0-9]+[.][0-9]+).* \(.*@.*\) \(.*\) .*\n'
+    r'(?P<release>(?P<version>[0-9]+[.][0-9]+[.][0-9]+).*) \(.*@.*\) \(.*\) .*\n'
 
 
-def get_version(input_bytes, start_idx):
+def get_from_release(input_bytes, start_idx, key):
   null_idx = input_bytes.find('\x00', start_idx)
   if null_idx < 0:
     return None
@@ -53,24 +53,43 @@ def get_version(input_bytes, start_idx):
     return None
   mo = re.match(LINUX_BANNER_REGEX, linux_banner)
   if mo:
-    return mo.group(1)
+    return mo.group(key)
   return None
 
 
-def dump_version(input_bytes):
+def dump_from_release(input_bytes, key):
+  """
+  Helper of dump_version and dump_release
+  """
   idx = 0
   while True:
     idx = input_bytes.find(LINUX_BANNER_PREFIX, idx)
     if idx < 0:
       return None
 
-    version = get_version(input_bytes, idx)
-    if version:
-      return version
+    value = get_from_release(input_bytes, idx, key)
+    if value:
+      return value
 
     idx += len(LINUX_BANNER_PREFIX)
 
 
+def dump_version(input_bytes):
+  """
+  Dump kernel version, w.x.y, from input_bytes. Search for the string
+  "Linux version " and do pattern matching after it. See LINUX_BANNER_REGEX.
+  """
+  return dump_from_release(input_bytes, "version")
+
+
+def dump_release(input_bytes):
+  """
+  Dump kernel release, w.x.y-..., from input_bytes. Search for the string
+  "Linux version " and do pattern matching after it. See LINUX_BANNER_REGEX.
+  """
+  return dump_from_release(input_bytes, "release")
+
+
 def dump_configs(input_bytes):
   """
   Dump kernel configuration from input_bytes. This can be done when
@@ -140,6 +159,23 @@ def decompress_dump(func, input_bytes):
       if o:
         return o
 
+
+def dump_to_file(f, dump_fn, input_bytes, desc):
+  """
+  Call decompress_dump(dump_fn, input_bytes) and write to f. If it fails, return
+  False; otherwise return True.
+  """
+  if f is not None:
+    o = decompress_dump(dump_fn, input_bytes)
+    if o:
+      f.write(o)
+    else:
+      sys.stderr.write(
+          "Cannot extract kernel {}".format(desc))
+      return False
+  return True
+
+
 def main():
   parser = argparse.ArgumentParser(
       formatter_class=argparse.RawTextHelpFormatter,
@@ -165,6 +201,13 @@ def main():
                       nargs='?',
                       type=argparse.FileType('wb'),
                       const=sys.stdout)
+  parser.add_argument('--output-release',
+                      help='If specified, write kernel release. Use stdout if '
+                           'no file is specified.',
+                      metavar='FILE',
+                      nargs='?',
+                      type=argparse.FileType('wb'),
+                      const=sys.stdout)
   parser.add_argument('--tools',
                       help='Decompression tools to use. If not specified, PATH '
                            'is searched.',
@@ -181,25 +224,18 @@ def main():
   input_bytes = args.input.read()
 
   ret = 0
-  if args.output_configs is not None:
-    o = decompress_dump(dump_configs, input_bytes)
-    if o:
-      args.output_configs.write(o)
-    else:
-      sys.stderr.write(
-          "Cannot extract kernel configs in {}".format(args.input.name))
-      ret = 1
-  if args.output_version is not None:
-    o = decompress_dump(dump_version, input_bytes)
-    if o:
-      args.output_version.write(o)
-    else:
-      sys.stderr.write(
-          "Cannot extract kernel versions in {}".format(args.input.name))
-      ret = 1
+  if not dump_to_file(args.output_configs, dump_configs, input_bytes,
+                      "configs in {}".format(args.input.name)):
+    ret = 1
+  if not dump_to_file(args.output_version, dump_version, input_bytes,
+                      "version in {}".format(args.input.name)):
+    ret = 1
+  if not dump_to_file(args.output_release, dump_release, input_bytes,
+                      "kernel release in {}".format(args.input.name)):
+    ret = 1
 
   return ret
 
 
 if __name__ == '__main__':
-  exit(main())
+  sys.exit(main())