Add a whatis command to sdb

Author: PaulZ-98

.github/scripts/install-drgn.sh

@@ -5,7 +5,7 @@
 # build/install of "drgn" will fail below.
 #
 sudo apt update
-sudo apt install bison flex libelf-dev libdw-dev libomp5 libomp-dev
+sudo apt install bison flex libelf-dev=0.170-0.4ubuntu0.1 libdw-dev=0.170-0.4ubuntu0.1 libomp5 libomp-dev
 
 git clone https://github.com/osandov/drgn.git
 

sdb/commands/linux/whatis.py

@@ -0,0 +1,75 @@
+#
+# Copyright 2020 Delphix
+# Copyright 2021 Datto Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+# pylint: disable=missing-docstring
+
+import argparse
+from typing import Iterable
+
+import drgn
+import drgn.helpers.linux.mm as mm
+import sdb
+
+
+def lookup_in_kmem(obj: drgn.Object) -> None:
+    pfn = mm.virt_to_pfn(sdb.get_prog(), obj)
+    page = mm.pfn_to_page(pfn)
+    try:
+        cache = page.slab_cache
+        cache_nm = cache.name.string_().decode('utf-8')
+        print(f"{hex(int(obj))} is allocated from {cache_nm}")
+    except drgn.FaultError:
+        print(f"{hex(int(obj))} does not map to a kmem_cache")
+
+
+class WhatIs(sdb.Command):
+    """
+    Print the name of the kmem cache from which the address is allocated.
+
+    DESCRIPTION
+       The address can be specified as an argument, or
+       passed through a pipe.
+
+    EXAMPLES
+        Determine the kmem_cache for a given address:
+
+            sdb> whatis 0xfffffe06596e21b8
+            0xfffffe06596e21b8 is allocated from dmu_buf_impl_t
+
+        Determine the kmem_cache of address passed through a
+        pipe:
+
+            sdb> dbuf |head 1 |deref |member db_buf |whatis
+            0xffff8e804368ac80 is allocated from arc_buf_t
+    """
+
+    names = ["whatis"]
+
+    @classmethod
+    def _init_parser(cls, name: str) -> argparse.ArgumentParser:
+        parser = super()._init_parser(name)
+        parser.add_argument("address", nargs="*", metavar="<address>")
+        return parser
+
+    def _call(self, objs: Iterable[drgn.Object]) -> None:
+        for obj in objs:
+            lookup_in_kmem(obj)
+        for addr in self.args.address:
+            try:
+                lookup_in_kmem(drgn.Object(sdb.get_prog(), "void *", int(addr, 16)))
+            except ValueError:
+                print(f"{addr} is not a valid address")

tests/integration/data/regression_output/linux/dbuf |head 1 |deref |member db_buf |whatis

@@ -0,0 +1 @@
+0xffffa08943a90050 is allocated from arc_buf_t

tests/integration/data/regression_output/linux/whatis 0xf987kkbbh

@@ -0,0 +1 @@
+0xf987kkbbh is not a valid address

tests/integration/data/regression_output/linux/whatis 0xffff

@@ -0,0 +1 @@
+0xffff does not map to a kmem_cache

tests/integration/data/regression_output/linux/whatis 0xffffa0888c766000 0xffffa089407ca870

@@ -0,0 +1,2 @@
+0xffffa0888c766000 is allocated from arc_buf_hdr_t_full
+0xffffa089407ca870 is allocated from dmu_buf_impl_t

tests/integration/data/regression_output/linux/whatis 0xffffa089407ca870

@@ -0,0 +1 @@
+0xffffa089407ca870 is allocated from dmu_buf_impl_t

tests/integration/test_linux_generic.py

@@ -94,6 +94,13 @@
     "threads | count",
     'threads | filter \'obj.comm == "java"\' | threads',
     "thread",
+
+    # whatis
+    "dbuf |head 1 |deref |member db_buf |whatis",
+    "whatis 0xffffa089407ca870",
+    "whatis 0xffffa0888c766000 0xffffa089407ca870",
+    "whatis 0xffff",
+    "whatis 0xf987kkbbh"
 ]
 
 STRIPPED_POS_CMDS = [