#59 WIP: Fix test_gdb when CET protection is enabled
Closed 9 months ago by vstinner. Opened 11 months ago by vstinner.
rpms/ vstinner/python3 test_gdb_cet  into  master

@@ -0,0 +1,87 @@ 

+ commit 0ce31d340b264a550a3c574e1d6913f4affd4669

+ Author: Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com>

+ Date:   Tue Oct 9 08:21:17 2018 -0700

+ 

+     bpo-32962: Fix test_gdb failure in debug build with -mcet -fcf-protection -O0 (GH-9656)

+     

+     

+     When Python is built with the intel control-flow protection flags,

+     -mcet -fcf-protection, gdb is not able to read the stack without

+     actually jumping inside the function. This means an extra

+     'next' command is required to make the $pc (program counter)

+     enter the function and make the stack of the function exposed to gdb.

+     

+     Co-Authored-By: Marcel Plch <gmarcel.plch@gmail.com>

+     

+     (cherry picked from commit 9b7c74ca32d1bec7128d550a9ab1b2ddc7046287)

+     (cherry picked from commit 79d21331e605fdc941f947621846b8563485aab6)

+     

+     Co-authored-by: Victor Stinner <vstinner@redhat.com>

+ 

+ diff --git a/Lib/test/test_gdb.py b/Lib/test/test_gdb.py

+ index 93a2c7dd57..0f950b2325 100644

+ --- a/Lib/test/test_gdb.py

+ +++ b/Lib/test/test_gdb.py

+ @@ -54,6 +54,23 @@ checkout_hook_path = os.path.join(os.path.dirname(sys.executable),

+  

+  PYTHONHASHSEED = '123'

+  

+ +

+ +def cet_protection():

+ +    cflags = sysconfig.get_config_var('CFLAGS')

+ +    if not cflags:

+ +        return False

+ +    flags = cflags.split()

+ +    # True if "-mcet -fcf-protection" options are found, but false

+ +    # if "-fcf-protection=none" or "-fcf-protection=return" is found.

+ +    return (('-mcet' in flags)

+ +            and any((flag.startswith('-fcf-protection')

+ +                     and not flag.endswith(("=none", "=return")))

+ +                    for flag in flags))

+ +

+ +# Control-flow enforcement technology

+ +CET_PROTECTION = cet_protection()

+ +

+ +

+  def run_gdb(*args, **env_vars):

+      """Runs gdb in --batch mode with the additional arguments given by *args.

+  

+ @@ -162,6 +179,12 @@ class DebuggerTests(unittest.TestCase):

+              commands += ['set print entry-values no']

+  

+          if cmds_after_breakpoint:

+ +            if CET_PROTECTION:

+ +                # bpo-32962: When Python is compiled with -mcet

+ +                # -fcf-protection, function arguments are unusable before

+ +                # running the first instruction of the function entry point.

+ +                # The 'next' command makes the required first step.

+ +                commands += ['next']

+              commands += cmds_after_breakpoint

+          else:

+              commands += ['backtrace']

+ @@ -869,9 +892,17 @@ id(42)

+              id("first break point")

+              l = MyList()

+          ''')

+ +        cmds_after_breakpoint = ['break wrapper_call', 'continue']

+ +        if CET_PROTECTION:

+ +            # bpo-32962: same case as in get_stack_trace():

+ +            # we need an additional 'next' command in order to read

+ +            # arguments of the innermost function of the call stack.

+ +            cmds_after_breakpoint.append('next')

+ +        cmds_after_breakpoint.append('py-bt')

+ +

+          # Verify with "py-bt":

+          gdb_output = self.get_stack_trace(cmd,

+ -                                          cmds_after_breakpoint=['break wrapper_call', 'continue', 'py-bt'])

+ +                                          cmds_after_breakpoint=cmds_after_breakpoint)

+          self.assertRegex(gdb_output,

+                           r"<method-wrapper u?'__init__' of MyList object at ")

+  

+ diff --git a/Misc/NEWS.d/next/Tests/2018-05-10-16-59-15.bpo-32962.S-rcIN.rst b/Misc/NEWS.d/next/Tests/2018-05-10-16-59-15.bpo-32962.S-rcIN.rst

+ new file mode 100644

+ index 0000000000..97328ebafe

+ --- /dev/null

+ +++ b/Misc/NEWS.d/next/Tests/2018-05-10-16-59-15.bpo-32962.S-rcIN.rst

+ @@ -0,0 +1 @@

+ +Fixed test_gdb when Python is compiled with flags -mcet -fcf-protection -O0.

file modified
+10 -2

@@ -14,7 +14,7 @@ 

  #  WARNING  When rebasing to a new Python version,

  #           remember to update the python3-docs package as well

  Version: %{pybasever}.0

- Release: 10%{?dist}

+ Release: 11%{?dist}

  License: Python

  

  

@@ -320,6 +320,12 @@ 

  # See: https://bugzilla.redhat.com/show_bug.cgi?id=1609291

  Patch308: 00308-tls-1.3.patch

  

+ # 00309 #

+ # Fix test_gdb failure in debug build with "-mcet -fcf-protection -O0".

+ # commit 0ce31d340b264a550a3c574e1d6913f4affd4669

+ # https://bugs.python.org/issue32962

+ Patch309: 00309-test_gdb_cet_protection.patch

+ 

  # (New patches go here ^^^)

  #

  # When adding new patches to "python" and "python3" in Fedora, EL, etc.,

@@ -1059,7 +1065,6 @@ 

      -wW --slowest --findleaks \

      -x test_distutils \

      -x test_bdist_rpm \

-     -x test_gdb \

      %ifarch %{mips64}

      -x test_ctypes \

      %endif

@@ -1551,6 +1556,9 @@ 

  # ======================================================

  

  %changelog

+ * Wed Oct 10 2018 Victor Stinner <vstinner@redhat.com> - 3.7.0-11

+ - Fix test_gdb when CET protection is enabled on x86_64 (rhbz#1541967)

+ 

  * Thu Sep 27 2018 Petr Viktorin <pviktori@redhat.com> - 3.7.0-10

  - Compile the debug build with -Og rather than -O0

  

test_gdb was failing when CET protection is enabled on x86_64
(rhbz#1541967): backport fix from upstream.

Will this be in 3.7.1?

I'm not sure, since 3.7.1 has been tagged at 2018-10-09, and I pushed my fixed at 2018-10-09. I hope that it will be part of 3.7.1 :-) I created this PR to reenable test_gdb and to learn how to create a PR also :-)

Too bad. test_gdb failed on the CI :-(

https://koji.fedoraproject.org/koji/taskinfo?taskID=30181306

Example:

+ echo STARTING: CHECKING OF PYTHON FOR CONFIGURATION: debug
(...)
======================================================================
FAIL: test_NULL_ob_type (test.test_gdb.PrettyPrintTests)
Ensure that a PyObject* with NULL ob_type is handled gracefully
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/builddir/build/BUILD/Python-3.7.0/Lib/test/test_gdb.py", line 485, in test_NULL_ob_type
    'set v->ob_type=0')
  File "/builddir/build/BUILD/Python-3.7.0/Lib/test/test_gdb.py", line 456, in assertSane
    cmds_after_breakpoint=cmds_after_breakpoint)
  File "/builddir/build/BUILD/Python-3.7.0/Lib/test/test_gdb.py", line 242, in get_gdb_repr
    self.fail('Unexpected gdb output: %r\n%s' % (gdb_output, gdb_output))
AssertionError: Unexpected gdb output: 'Breakpoint 1 (builtin_id) pending.\n[Thread debugging using libthread_db enabled]\nUsing host libthread_db library "/lib64/libthread_db.so.1".\n'
Breakpoint 1 (builtin_id) pending.
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".

The issue that happens now is a different one. The PR actually fixes the bug, but this is due to the rebase of gdb which changes some of its python API.

test_gdb fails on Fedora Rawhide because of a bug in gdb: https://bugzilla.redhat.com/show_bug.cgi?id=1638798

Metadata Update from @churchyard:
- Pull-request tagged with: WIP, bugfix, tests

10 months ago

Metadata Update from @churchyard:
- Pull-request tagged with: blocked

10 months ago

This PR is no longer needed, the fix is part of Python 3.7.1 and the python3 package has been updated to Python 3.7.1. I just forgot to close this PR :-)

Pull-Request has been closed by vstinner

9 months ago