Allows sel_ldr.py to run arm binaries through qemu-arm.

native_client_sdk/src/tools/sel_ldr.py

 #!/usr/bin/env python
 # Copyright 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Wrapper script for launching application within the sel_ldr.
 """
 
 import optparse
 import os
 import subprocess
 import sys
 
+SCRIPT_DIR = os.path.dirname(os.path.abspath(__file__))
+sys.path.append(SCRIPT_DIR)

[Sam Clegg, 2014/05/01 19:19:10]

This is the default for python normally.

I think its a google3-ism that this is needed so we should probably instead
include this patch in the google3 import scripts.

I wonder if there is a way we can tell google3 python to behave like normal
python?

[cdonner, 2014/05/02 17:58:06]

Reverted.
Unlikely, since it's not python that's the problem, it's the build system.

+
 import create_nmf
 import getos
 
-SCRIPT_DIR = os.path.dirname(os.path.abspath(__file__))
 NACL_SDK_ROOT = os.path.dirname(SCRIPT_DIR)
 
 if sys.version_info < (2, 6, 0):
   sys.stderr.write("python 2.6 or later is required run this script\n")
   sys.exit(1)
 
 
 class Error(Exception):
   pass
 
@@ skipping 34 matching lines @@
     Log.verbose = True
 
   osname = getos.GetPlatform()
   if not os.path.exists(nexe):
     raise Error('executable not found: %s' % nexe)
   if not os.path.isfile(nexe):
     raise Error('not a file: %s' % nexe)
 
   arch, dynamic = create_nmf.ParseElfHeader(nexe)
 
-  if arch == 'arm':
-    raise Error('Cannot run ARM executables under sel_ldr')
+  if arch == 'arm' and osname != 'linux':
+    raise Error('Cannot run ARM executables under sel_ldr on ' + osname)
 
   arch_suffix = arch.replace('-', '_')
 
   sel_ldr = os.path.join(SCRIPT_DIR, 'sel_ldr_%s' % arch_suffix)
   irt = os.path.join(SCRIPT_DIR, 'irt_core_%s.nexe' % arch_suffix)
   if osname == 'win':
     sel_ldr += '.exe'
   Log('ROOT    = %s' % NACL_SDK_ROOT)
   Log('SEL_LDR = %s' % sel_ldr)
   Log('IRT     = %s' % irt)
   cmd = [sel_ldr]
 
   if osname == 'linux':
     # Run sel_ldr under nacl_helper_bootstrap
     helper = os.path.join(SCRIPT_DIR, 'nacl_helper_bootstrap_%s' % arch_suffix)
     Log('HELPER  = %s' % helper)
     cmd.insert(0, helper)
     cmd.append('--r_debug=0xXXXXXXXXXXXXXXXX')
     cmd.append('--reserved_at_zero=0xXXXXXXXXXXXXXXXX')
 
   cmd += ['-a', '-B', irt]
 
   if options.debug:
     cmd.append('-g')
 
   if not options.verbose:
     cmd += ['-l', os.devnull]
 
+  if arch == 'arm':
+    # Use the QEMU arm emulator if available.
+    qemu_locations = [os.path.join(SCRIPT_DIR, 'qemu_arm'),
+                      os.path.join(SCRIPT_DIR, 'qemu-arm')]
+    qemu_locations += [os.path.join(path, 'qemu_arm')
+                       for path in os.environ["PATH"].split(os.pathsep)]

[Sam Clegg, 2014/05/01 19:19:10]

Can probably drop these two lines?  Isn't it always called qemu-arm when its in
the system PATH?

[cdonner, 2014/05/02 17:58:06]

google3 has qemu_arm, but I noticed that the native_client repo has
toolchain/linux_x86/arm_trusted/qemu-arm.  I'm ok dropping qemu-arm since that
doens't seem to be common, but if that's the case perhaps the file in
arm_trusted here should be renamed?

+    qemu_locations += [os.path.join(path, 'qemu-arm')
+                       for path in os.environ["PATH"].split(os.pathsep)]
+    # See if qemu is in any of these locations.
+    qemu_bin = None
+    for loc in qemu_locations:
+      if os.path.isfile(loc) and os.access(loc, os.X_OK):
+        qemu_bin = loc
+        break
+    if qemu_bin:
+      qemu = [qemu_bin, '-cpu', 'cortex-a8', '-L',
+              os.path.abspath(os.path.join(NACL_SDK_ROOT, 'toolchain',
+                                           'linux_arm_trusted'))]
+      # '-Q' disables platform qualification, allowing arm binaries to run.
+      cmd = qemu + cmd + ['-Q']
+    else:
+      raise Error('Cannot run ARM executables under sel_ldr without an emulator'
+                  '. Try installing QEMU (http://wiki.qemu.org/).')

[Sam Clegg, 2014/05/01 19:19:10]

How about a separate FindQemu() function?

[cdonner, 2014/05/02 17:58:06]

Done.

+
   if dynamic:
     if options.debug_libs:
       libpath = os.path.join(NACL_SDK_ROOT, 'lib',
                             'glibc_%s' % arch_suffix, 'Debug')
     else:
       libpath = os.path.join(NACL_SDK_ROOT, 'lib',
                             'glibc_%s' % arch_suffix, 'Release')
     toolchain = '%s_x86_glibc' % osname
     sdk_lib_dir = os.path.join(NACL_SDK_ROOT, 'toolchain',
                                toolchain, 'x86_64-nacl')
@@ skipping 17 matching lines @@
   rtn = subprocess.call(cmd)
   return rtn
 
 
 if __name__ == '__main__':
   try:
     sys.exit(main(sys.argv[1:]))
   except Error as e:
     sys.stderr.write(str(e) + '\n')
     sys.exit(1)