Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 213 insertions, 0 deletions

diff --git a/Documentation/bpf/drgn.rst b/Documentation/bpf/drgn.rst
new file mode 100644
index 000000000..cabf702eb
--- /dev/null
+++ b/Documentation/bpf/drgn.rst
@@ -0,0 +1,213 @@
+.. SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
+
+==============
+BPF drgn tools
+==============
+
+drgn scripts is a convenient and easy to use mechanism to retrieve arbitrary
+kernel data structures. drgn is not relying on kernel UAPI to read the data.
+Instead it's reading directly from ``/proc/kcore`` or vmcore and pretty prints
+the data based on DWARF debug information from vmlinux.
+
+This document describes BPF related drgn tools.
+
+See `drgn/tools`_ for all tools available at the moment and `drgn/doc`_ for
+more details on drgn itself.
+
+bpf_inspect.py
+--------------
+
+Description
+===========
+
+`bpf_inspect.py`_ is a tool intended to inspect BPF programs and maps. It can
+iterate over all programs and maps in the system and print basic information
+about these objects, including id, type and name.
+
+The main use-case `bpf_inspect.py`_ covers is to show BPF programs of types
+``BPF_PROG_TYPE_EXT`` and ``BPF_PROG_TYPE_TRACING`` attached to other BPF
+programs via ``freplace``/``fentry``/``fexit``/``fsession`` mechanisms, since
+there is no user-space API to get this information.
+
+Getting started
+===============
+
+List BPF programs (full names are obtained from BTF)::
+
+    % sudo bpf_inspect.py prog
+        27: BPF_PROG_TYPE_TRACEPOINT         tracepoint__tcp__tcp_send_reset
+      4632: BPF_PROG_TYPE_CGROUP_SOCK_ADDR   tw_ipt_bind
+     49464: BPF_PROG_TYPE_RAW_TRACEPOINT     raw_tracepoint__sched_process_exit
+
+List BPF maps::
+
+      % sudo bpf_inspect.py map
+        2577: BPF_MAP_TYPE_HASH                tw_ipt_vips
+        4050: BPF_MAP_TYPE_STACK_TRACE         stack_traces
+        4069: BPF_MAP_TYPE_PERCPU_ARRAY        ned_dctcp_cntr
+
+Find BPF programs attached to BPF program ``test_pkt_access``::
+
+      % sudo bpf_inspect.py p | grep test_pkt_access
+         650: BPF_PROG_TYPE_SCHED_CLS          test_pkt_access
+         654: BPF_PROG_TYPE_TRACING            test_main                        linked:[650->25: BPF_TRAMP_FEXIT test_pkt_access->test_pkt_access()]
+         655: BPF_PROG_TYPE_TRACING            test_subprog1                    linked:[650->29: BPF_TRAMP_FEXIT test_pkt_access->test_pkt_access_subprog1()]
+         656: BPF_PROG_TYPE_TRACING            test_subprog2                    linked:[650->31: BPF_TRAMP_FEXIT test_pkt_access->test_pkt_access_subprog2()]
+         657: BPF_PROG_TYPE_TRACING            test_subprog3                    linked:[650->21: BPF_TRAMP_FEXIT test_pkt_access->test_pkt_access_subprog3()]
+         658: BPF_PROG_TYPE_EXT                new_get_skb_len                  linked:[650->16: BPF_TRAMP_REPLACE test_pkt_access->get_skb_len()]
+         659: BPF_PROG_TYPE_EXT                new_get_skb_ifindex              linked:[650->23: BPF_TRAMP_REPLACE test_pkt_access->get_skb_ifindex()]
+         660: BPF_PROG_TYPE_EXT                new_get_constant                 linked:[650->19: BPF_TRAMP_REPLACE test_pkt_access->get_constant()]
+
+It can be seen that there is a program ``test_pkt_access``, id 650 and there
+are multiple other tracing and ext programs attached to functions in
+``test_pkt_access``.
+
+For example the line::
+
+         658: BPF_PROG_TYPE_EXT                new_get_skb_len                  linked:[650->16: BPF_TRAMP_REPLACE test_pkt_access->get_skb_len()]
+
+, means that BPF program id 658, type ``BPF_PROG_TYPE_EXT``, name
+``new_get_skb_len`` replaces (``BPF_TRAMP_REPLACE``) function ``get_skb_len()``
+that has BTF id 16 in BPF program id 650, name ``test_pkt_access``.
+
+Getting help:
+
+.. code-block:: none
+
+    % sudo bpf_inspect.py
+    usage: bpf_inspect.py [-h] {prog,p,map,m} ...
+
+    drgn script to list BPF programs or maps and their properties
+    unavailable via kernel API.
+
+    See https://github.com/osandov/drgn/ for more details on drgn.
+
+    optional arguments:
+      -h, --help      show this help message and exit
+
+    subcommands:
+      {prog,p,map,m}
+        prog (p)      list BPF programs
+        map (m)       list BPF maps
+
+Customization
+=============
+
+The script is intended to be customized by developers to print relevant
+information about BPF programs, maps and other objects.
+
+For example, to print ``struct bpf_prog_aux`` for BPF program id 53077:
+
+.. code-block:: none
+
+    % git diff
+    diff --git a/tools/bpf_inspect.py b/tools/bpf_inspect.py
+    index 650e228..aea2357 100755
+    --- a/tools/bpf_inspect.py
+    +++ b/tools/bpf_inspect.py
+    @@ -112,7 +112,9 @@ def list_bpf_progs(args):
+             if linked:
+                 linked = f" linked:[{linked}]"
+
+    -        print(f"{id_:>6}: {type_:32} {name:32} {linked}")
+    +        if id_ == 53077:
+    +            print(f"{id_:>6}: {type_:32} {name:32}")
+    +            print(f"{bpf_prog.aux}")
+
+
+     def list_bpf_maps(args):
+
+It produces the output::
+
+    % sudo bpf_inspect.py p
+     53077: BPF_PROG_TYPE_XDP                tw_xdp_policer
+    *(struct bpf_prog_aux *)0xffff8893fad4b400 = {
+            .refcnt = (atomic64_t){
+                    .counter = (long)58,
+            },
+            .used_map_cnt = (u32)1,
+            .max_ctx_offset = (u32)8,
+            .max_pkt_offset = (u32)15,
+            .max_tp_access = (u32)0,
+            .stack_depth = (u32)8,
+            .id = (u32)53077,
+            .func_cnt = (u32)0,
+            .func_idx = (u32)0,
+            .attach_btf_id = (u32)0,
+            .linked_prog = (struct bpf_prog *)0x0,
+            .verifier_zext = (bool)0,
+            .offload_requested = (bool)0,
+            .attach_btf_trace = (bool)0,
+            .func_proto_unreliable = (bool)0,
+            .trampoline_prog_type = (enum bpf_tramp_prog_type)BPF_TRAMP_FENTRY,
+            .trampoline = (struct bpf_trampoline *)0x0,
+            .tramp_hlist = (struct hlist_node){
+                    .next = (struct hlist_node *)0x0,
+                    .pprev = (struct hlist_node **)0x0,
+            },
+            .attach_func_proto = (const struct btf_type *)0x0,
+            .attach_func_name = (const char *)0x0,
+            .func = (struct bpf_prog **)0x0,
+            .jit_data = (void *)0x0,
+            .poke_tab = (struct bpf_jit_poke_descriptor *)0x0,
+            .size_poke_tab = (u32)0,
+            .ksym_tnode = (struct latch_tree_node){
+                    .node = (struct rb_node [2]){
+                            {
+                                    .__rb_parent_color = (unsigned long)18446612956263126665,
+                                    .rb_right = (struct rb_node *)0x0,
+                                    .rb_left = (struct rb_node *)0xffff88a0be3d0088,
+                            },
+                            {
+                                    .__rb_parent_color = (unsigned long)18446612956263126689,
+                                    .rb_right = (struct rb_node *)0x0,
+                                    .rb_left = (struct rb_node *)0xffff88a0be3d00a0,
+                            },
+                    },
+            },
+            .ksym_lnode = (struct list_head){
+                    .next = (struct list_head *)0xffff88bf481830b8,
+                    .prev = (struct list_head *)0xffff888309f536b8,
+            },
+            .ops = (const struct bpf_prog_ops *)xdp_prog_ops+0x0 = 0xffffffff820fa350,
+            .used_maps = (struct bpf_map **)0xffff889ff795de98,
+            .prog = (struct bpf_prog *)0xffffc9000cf2d000,
+            .user = (struct user_struct *)root_user+0x0 = 0xffffffff82444820,
+            .load_time = (u64)2408348759285319,
+            .cgroup_storage = (struct bpf_map *[2]){},
+            .name = (char [16])"tw_xdp_policer",
+            .security = (void *)0xffff889ff795d548,
+            .offload = (struct bpf_prog_offload *)0x0,
+            .btf = (struct btf *)0xffff8890ce6d0580,
+            .func_info = (struct bpf_func_info *)0xffff889ff795d240,
+            .func_info_aux = (struct bpf_func_info_aux *)0xffff889ff795de20,
+            .linfo = (struct bpf_line_info *)0xffff888a707afc00,
+            .jited_linfo = (void **)0xffff8893fad48600,
+            .func_info_cnt = (u32)1,
+            .nr_linfo = (u32)37,
+            .linfo_idx = (u32)0,
+            .num_exentries = (u32)0,
+            .extable = (struct exception_table_entry *)0xffffffffa032d950,
+            .stats = (struct bpf_prog_stats *)0x603fe3a1f6d0,
+            .work = (struct work_struct){
+                    .data = (atomic_long_t){
+                            .counter = (long)0,
+                    },
+                    .entry = (struct list_head){
+                            .next = (struct list_head *)0x0,
+                            .prev = (struct list_head *)0x0,
+                    },
+                    .func = (work_func_t)0x0,
+            },
+            .rcu = (struct callback_head){
+                    .next = (struct callback_head *)0x0,
+                    .func = (void (*)(struct callback_head *))0x0,
+            },
+    }
+
+
+.. Links
+.. _drgn/doc: https://drgn.readthedocs.io/en/latest/
+.. _drgn/tools: https://github.com/osandov/drgn/tree/master/tools
+.. _bpf_inspect.py:
+   https://github.com/osandov/drgn/blob/master/tools/bpf_inspect.py