fix errno command (#1112)

* fix errno command

* fix isort

* try to fix CI

* Update test_command_errno.py

pwndbg/commands/__init__.py

@@ -339,7 +339,7 @@ class _ArgparsedCommand(Command):
 class ArgparsedCommand:
     """Adds documentation and offloads parsing for a Command via argparse"""
 
-    def __init__(self, parser_or_desc, aliases=[]):
+    def __init__(self, parser_or_desc, aliases=[], command_name=None):
         """
         :param parser_or_desc: `argparse.ArgumentParser` instance or `str`
         """
@@ -348,6 +348,8 @@ class ArgparsedCommand:
         else:
             self.parser = parser_or_desc
         self.aliases = aliases
+        self._command_name = command_name
+
         # We want to run all integer and otherwise-unspecified arguments
         # through fix() so that GDB parses it.
         for action in self.parser._actions:
@@ -360,8 +362,8 @@ class ArgparsedCommand:
 
     def __call__(self, function):
         for alias in self.aliases:
-            _ArgparsedCommand(self.parser, function, alias)
-        return _ArgparsedCommand(self.parser, function)
+            _ArgparsedCommand(self.parser, function, command_name=alias)
+        return _ArgparsedCommand(self.parser, function, command_name=self._command_name)
 
 
 # We use a 64-bit max value literal here instead of pwndbg.arch.current

pwndbg/commands/misc.py

@@ -1,14 +1,14 @@
 import argparse
-import errno as _errno
+import errno
+
+import gdb
 
-import pwndbg as _pwndbg
-import pwndbg.arch as _arch
 import pwndbg.auxv
 import pwndbg.commands
 import pwndbg.regs
 import pwndbg.symbol
 
-_errno.errorcode[0] = "OK"
+errno.errorcode[0] = "OK"
 
 parser = argparse.ArgumentParser(
     description="""
@@ -24,24 +24,25 @@ parser.add_argument(
 )
 
 
-@_pwndbg.commands.ArgparsedCommand(parser)
+@pwndbg.commands.ArgparsedCommand(parser, command_name="errno")
 @pwndbg.commands.OnlyWhenRunning
-def errno(err):
+def errno_(err):
     if err is None:
-        # Dont ask.
-        errno_location = pwndbg.symbol.get("__errno_location")
-        err = pwndbg.memory.int(errno_location)
-        # err = int(gdb.parse_and_eval('*((int *(*) (void)) __errno_location) ()'))
-
-    err = abs(int(err))
-
-    if err >> 63:
-        err -= 1 << 64
-    elif err >> 31:
-        err -= 1 << 32
-
-    msg = _errno.errorcode.get(int(err), "Unknown error code")
-    print("Errno %i: %s" % (err, msg))
+        # Try to get the `errno` variable value
+        # if it does not exist, get the errno variable from its location
+        try:
+            err = int(gdb.parse_and_eval("errno"))
+        except gdb.error:
+            try:
+                err = int(gdb.parse_and_eval("*((int *(*) (void)) __errno_location) ()"))
+            except gdb.error:
+                print(
+                    "Could not determine error code automatically: neither `errno` nor `__errno_location` symbols were provided (was libc.so loaded already?)"
+                )
+                return
+
+    msg = errno.errorcode.get(int(err), "Unknown error code")
+    print("Errno %s: %s" % (err, msg))
 
 
 parser = argparse.ArgumentParser(
@@ -58,8 +59,8 @@ parser.add_argument(
 )
 
 
-@_pwndbg.commands.ArgparsedCommand(parser)
-def pwndbg(filter_pattern):
+@pwndbg.commands.ArgparsedCommand(parser, command_name="pwndbg")
+def pwndbg_(filter_pattern):
     for name, docs in list_and_filter_commands(filter_pattern):
         print("%-20s %s" % (name, docs))
 
@@ -69,19 +70,19 @@ parser.add_argument("a", type=int, help="The first address.")
 parser.add_argument("b", type=int, help="The second address.")
 
 
-@_pwndbg.commands.ArgparsedCommand(parser)
+@pwndbg.commands.ArgparsedCommand(parser)
 def distance(a, b):
     """Print the distance between the two arguments"""
-    a = int(a) & _arch.ptrmask
-    b = int(b) & _arch.ptrmask
+    a = int(a) & pwndbg.arch.ptrmask
+    b = int(b) & pwndbg.arch.ptrmask
 
     distance = b - a
 
-    print("%#x->%#x is %#x bytes (%#x words)" % (a, b, distance, distance // _arch.ptrsize))
+    print("%#x->%#x is %#x bytes (%#x words)" % (a, b, distance, distance // pwndbg.arch.ptrsize))
 
 
 def list_and_filter_commands(filter_str):
-    sorted_commands = list(_pwndbg.commands.commands)
+    sorted_commands = list(pwndbg.commands.commands)
     sorted_commands.sort(key=lambda x: x.__name__)
 
     if filter_str:

tests/test_command_errno.py

@@ -0,0 +1,48 @@
+import gdb
+
+import pwndbg
+import pwndbg.memory
+import pwndbg.regs
+import tests
+
+# We use the heap_vis binary as it enforces pthreads and so will have TLS on all distros
+REFERENCE_BINARY = tests.binaries.get("heap_vis.out")
+
+
+def test_command_errno(start_binary):
+    """
+    Tests the errno command display
+    """
+    start_binary(REFERENCE_BINARY)
+
+    # Since start_binary does 'starti' which stops on the very first instruction
+    # the errno is not yet an available symbol, because the libc library it is
+    # defined in is not yet loaded
+    result = "".join(gdb.execute("errno", to_string=True).splitlines())
+    assert (
+        result
+        == "Could not determine error code automatically: neither `errno` nor `__errno_location` symbols were provided (was libc.so loaded already?)"
+    )
+
+    gdb.execute("break main")
+    gdb.execute("continue")
+
+    result = gdb.execute("errno", to_string=True)
+    assert result == "Errno 0: OK\n"
+
+    gdb.execute("set *(int*)&errno=11")
+    result = gdb.execute("errno", to_string=True)
+    assert result == "Errno 11: EAGAIN\n"
+
+    gdb.execute("set *(int*)&errno=111")
+    result = gdb.execute("errno", to_string=True)
+    assert result == "Errno 111: ECONNREFUSED\n"
+
+    result = gdb.execute("errno 8", to_string=True)
+    assert result == "Errno 8: ENOEXEC\n"
+
+    result = gdb.execute("errno 123", to_string=True)
+    assert result == "Errno 123: ENOMEDIUM\n"
+
+    result = gdb.execute("errno 250", to_string=True)
+    assert result == "Errno 250: Unknown error code\n"