Merge pull request #273 from delphix/master

Merge branch 'master' into '6.0/stage'

Author: sdimitro

README.md

@@ -1,5 +1,5 @@
 # sdb
-The Slick/Simple Debugger
+The Slick Debugger
 
 ![](https://github.com/delphix/sdb/workflows/.github/workflows/main.yml/badge.svg)
 
@@ -21,6 +21,35 @@ $ sudo python3 setup.py install
 
 The above should install `sdb` under `/usr/local/bin/`.
 
+### Quickstart
+
+Running `sudo sdb` attaches sdb to the running kernel by default.
+To debug a running program, run `sudo sdb -p <PID>`.
+For post-mortem debugging (either a kernel crash dump or a userland core dump), use `sudo sdb <vmlinux path|userland binary path> <dump>`.
+
+```
+$ sudo sdb
+sdb> find_task 1 | member comm
+(char [16])"systemd"
+sdb> find_task 1 | stack
+TASK_STRUCT        STATE             COUNT
+==========================================
+0xffff89cea441dd00 INTERRUPTIBLE         1
+                  __schedule+0x2e5
+                  schedule+0x33
+                  schedule_hrtimeout_range_clock+0xfd
+                  schedule_hrtimeout_range+0x13
+                  ep_poll+0x40a
+                  do_epoll_wait+0xb7
+                  __x64_sys_epoll_wait+0x1e
+                  do_syscall_64+0x57
+                  entry_SYSCALL_64+0x7c
+sdb> addr modules | lxlist "struct module" list | member name ! sort | head -n 3
+(char [56])"aesni_intel"
+(char [56])"async_memcpy"
+(char [56])"async_pq"
+```
+
 ### Resources
 
 User and developer resources for sdb can be found in the [project's wiki](https://github.com/delphix/sdb/wiki).

sdb/commands/linux/internal/slub_helpers.py

@@ -16,11 +16,11 @@
 
 # pylint: disable=missing-docstring
 
-from typing import Iterable, Set
+from typing import Iterable, Set, Optional
 
 import drgn
 from drgn.helpers.linux.list import list_for_each_entry
-from drgn.helpers.linux.mm import for_each_page, page_to_virt
+from drgn.helpers.linux.mm import for_each_page, page_to_virt, virt_to_pfn, pfn_to_page
 
 import sdb
 
@@ -136,6 +136,18 @@ def cache_red_left_padding(cache: drgn.Object) -> int:
     return padding
 
 
+def lookup_cache_by_address(obj: drgn.Object) -> Optional[drgn.Object]:
+    pfn = virt_to_pfn(sdb.get_prog(), obj)
+    page = pfn_to_page(pfn)
+    cache = page.slab_cache
+    try:
+        # read the name to force FaultError if any
+        _ = cache.name.string_().decode('utf-8')
+    except drgn.FaultError:
+        return None
+    return cache
+
+
 def cache_get_free_pointer(cache: drgn.Object, p: drgn.Object) -> drgn.Object:
     """
     Get the next pointer in the freelist. Note, that this

sdb/commands/linux/whatis.py

@@ -0,0 +1,77 @@
+#
+# 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 sdb
+from sdb.commands.linux.internal import slub_helpers as slub
+
+
+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"]
+
+    @staticmethod
+    def print_cache(cache: drgn.Object, addr: str) -> None:
+        if cache is None:
+            print(f"{addr} does not map to a kmem_cache")
+        else:
+            assert sdb.type_canonical_name(cache.type_) == 'struct kmem_cache *'
+            cache_nm = cache.name.string_().decode('utf-8')
+            print(f"{addr} is allocated from {cache_nm}")
+
+    @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:
+            cache = slub.lookup_cache_by_address(obj)
+            self.print_cache(cache, hex(int(obj)))
+        for addr in self.args.address:
+            try:
+                obj = sdb.create_object("void *", int(addr, 16))
+            except ValueError:
+                print(f"{addr} is not a valid address")
+                continue
+            cache = slub.lookup_cache_by_address(obj)
+            self.print_cache(cache, addr)

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 = [