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, 238 insertions, 0 deletions

diff --git a/Documentation/bpf/map_devmap.rst b/Documentation/bpf/map_devmap.rst
new file mode 100644
index 000000000..927312c7b
--- /dev/null
+++ b/Documentation/bpf/map_devmap.rst
@@ -0,0 +1,238 @@
+.. SPDX-License-Identifier: GPL-2.0-only
+.. Copyright (C) 2022 Red Hat, Inc.
+
+=================================================
+BPF_MAP_TYPE_DEVMAP and BPF_MAP_TYPE_DEVMAP_HASH
+=================================================
+
+.. note::
+   - ``BPF_MAP_TYPE_DEVMAP`` was introduced in kernel version 4.14
+   - ``BPF_MAP_TYPE_DEVMAP_HASH`` was introduced in kernel version 5.4
+
+``BPF_MAP_TYPE_DEVMAP`` and ``BPF_MAP_TYPE_DEVMAP_HASH`` are BPF maps primarily
+used as backend maps for the XDP BPF helper call ``bpf_redirect_map()``.
+``BPF_MAP_TYPE_DEVMAP`` is backed by an array that uses the key as
+the index to lookup a reference to a net device. While ``BPF_MAP_TYPE_DEVMAP_HASH``
+is backed by a hash table that uses a key to lookup a reference to a net device.
+The user provides either <``key``/ ``ifindex``> or <``key``/ ``struct bpf_devmap_val``>
+pairs to update the maps with new net devices.
+
+.. note::
+    - The key to a hash map doesn't have to be an ``ifindex``.
+    - While ``BPF_MAP_TYPE_DEVMAP_HASH`` allows for densely packing the net devices
+      it comes at the cost of a hash of the key when performing a look up.
+
+The setup and packet enqueue/send code is shared between the two types of
+devmap; only the lookup and insertion is different.
+
+Usage
+=====
+Kernel BPF
+----------
+bpf_redirect_map()
+^^^^^^^^^^^^^^^^^^
+.. code-block:: c
+
+    long bpf_redirect_map(struct bpf_map *map, u32 key, u64 flags)
+
+Redirect the packet to the endpoint referenced by ``map`` at index ``key``.
+For ``BPF_MAP_TYPE_DEVMAP`` and ``BPF_MAP_TYPE_DEVMAP_HASH`` this map contains
+references to net devices (for forwarding packets through other ports).
+
+The lower two bits of *flags* are used as the return code if the map lookup
+fails. This is so that the return value can be one of the XDP program return
+codes up to ``XDP_TX``, as chosen by the caller. The higher bits of ``flags``
+can be set to ``BPF_F_BROADCAST`` or ``BPF_F_EXCLUDE_INGRESS`` as defined
+below.
+
+With ``BPF_F_BROADCAST`` the packet will be broadcast to all the interfaces
+in the map, with ``BPF_F_EXCLUDE_INGRESS`` the ingress interface will be excluded
+from the broadcast.
+
+.. note::
+    - The key is ignored if BPF_F_BROADCAST is set.
+    - The broadcast feature can also be used to implement multicast forwarding:
+      simply create multiple DEVMAPs, each one corresponding to a single multicast group.
+
+This helper will return ``XDP_REDIRECT`` on success, or the value of the two
+lower bits of the ``flags`` argument if the map lookup fails.
+
+More information about redirection can be found :doc:`redirect`
+
+bpf_map_lookup_elem()
+^^^^^^^^^^^^^^^^^^^^^
+.. code-block:: c
+
+   void *bpf_map_lookup_elem(struct bpf_map *map, const void *key)
+
+Net device entries can be retrieved using the ``bpf_map_lookup_elem()``
+helper.
+
+User space
+----------
+.. note::
+    DEVMAP entries can only be updated/deleted from user space and not
+    from an eBPF program. Trying to call these functions from a kernel eBPF
+    program will result in the program failing to load and a verifier warning.
+
+bpf_map_update_elem()
+^^^^^^^^^^^^^^^^^^^^^
+.. code-block:: c
+
+   int bpf_map_update_elem(int fd, const void *key, const void *value, __u64 flags);
+
+Net device entries can be added or updated using the ``bpf_map_update_elem()``
+helper. This helper replaces existing elements atomically. The ``value`` parameter
+can be ``struct bpf_devmap_val`` or a simple ``int ifindex`` for backwards
+compatibility.
+
+ .. code-block:: c
+
+    struct bpf_devmap_val {
+        __u32 ifindex;   /* device index */
+        union {
+            int   fd;  /* prog fd on map write */
+            __u32 id;  /* prog id on map read */
+        } bpf_prog;
+    };
+
+The ``flags`` argument can be one of the following:
+  - ``BPF_ANY``: Create a new element or update an existing element.
+  - ``BPF_NOEXIST``: Create a new element only if it did not exist.
+  - ``BPF_EXIST``: Update an existing element.
+
+DEVMAPs can associate a program with a device entry by adding a ``bpf_prog.fd``
+to ``struct bpf_devmap_val``. Programs are run after ``XDP_REDIRECT`` and have
+access to both Rx device and Tx device. The  program associated with the ``fd``
+must have type XDP with expected attach type ``xdp_devmap``.
+When a program is associated with a device index, the program is run on an
+``XDP_REDIRECT`` and before the buffer is added to the per-cpu queue. Examples
+of how to attach/use xdp_devmap progs can be found in the kernel selftests:
+
+- ``tools/testing/selftests/bpf/prog_tests/xdp_devmap_attach.c``
+- ``tools/testing/selftests/bpf/progs/test_xdp_with_devmap_helpers.c``
+
+bpf_map_lookup_elem()
+^^^^^^^^^^^^^^^^^^^^^
+.. code-block:: c
+
+.. c:function::
+   int bpf_map_lookup_elem(int fd, const void *key, void *value);
+
+Net device entries can be retrieved using the ``bpf_map_lookup_elem()``
+helper.
+
+bpf_map_delete_elem()
+^^^^^^^^^^^^^^^^^^^^^
+.. code-block:: c
+
+.. c:function::
+   int bpf_map_delete_elem(int fd, const void *key);
+
+Net device entries can be deleted using the ``bpf_map_delete_elem()``
+helper. This helper will return 0 on success, or negative error in case of
+failure.
+
+Examples
+========
+
+Kernel BPF
+----------
+
+The following code snippet shows how to declare a ``BPF_MAP_TYPE_DEVMAP``
+called tx_port.
+
+.. code-block:: c
+
+    struct {
+        __uint(type, BPF_MAP_TYPE_DEVMAP);
+        __type(key, __u32);
+        __type(value, __u32);
+        __uint(max_entries, 256);
+    } tx_port SEC(".maps");
+
+The following code snippet shows how to declare a ``BPF_MAP_TYPE_DEVMAP_HASH``
+called forward_map.
+
+.. code-block:: c
+
+    struct {
+        __uint(type, BPF_MAP_TYPE_DEVMAP_HASH);
+        __type(key, __u32);
+        __type(value, struct bpf_devmap_val);
+        __uint(max_entries, 32);
+    } forward_map SEC(".maps");
+
+.. note::
+
+    The value type in the DEVMAP above is a ``struct bpf_devmap_val``
+
+The following code snippet shows a simple xdp_redirect_map program. This program
+would work with a user space program that populates the devmap ``forward_map`` based
+on ingress ifindexes. The BPF program (below) is redirecting packets using the
+ingress ``ifindex`` as the ``key``.
+
+.. code-block:: c
+
+    SEC("xdp")
+    int xdp_redirect_map_func(struct xdp_md *ctx)
+    {
+        int index = ctx->ingress_ifindex;
+
+        return bpf_redirect_map(&forward_map, index, 0);
+    }
+
+The following code snippet shows a BPF program that is broadcasting packets to
+all the interfaces in the ``tx_port`` devmap.
+
+.. code-block:: c
+
+    SEC("xdp")
+    int xdp_redirect_map_func(struct xdp_md *ctx)
+    {
+        return bpf_redirect_map(&tx_port, 0, BPF_F_BROADCAST | BPF_F_EXCLUDE_INGRESS);
+    }
+
+User space
+----------
+
+The following code snippet shows how to update a devmap called ``tx_port``.
+
+.. code-block:: c
+
+    int update_devmap(int ifindex, int redirect_ifindex)
+    {
+        int ret;
+
+        ret = bpf_map_update_elem(bpf_map__fd(tx_port), &ifindex, &redirect_ifindex, 0);
+        if (ret < 0) {
+            fprintf(stderr, "Failed to update devmap_ value: %s\n",
+                strerror(errno));
+        }
+
+        return ret;
+    }
+
+The following code snippet shows how to update a hash_devmap called ``forward_map``.
+
+.. code-block:: c
+
+    int update_devmap(int ifindex, int redirect_ifindex)
+    {
+        struct bpf_devmap_val devmap_val = { .ifindex = redirect_ifindex };
+        int ret;
+
+        ret = bpf_map_update_elem(bpf_map__fd(forward_map), &ifindex, &devmap_val, 0);
+        if (ret < 0) {
+            fprintf(stderr, "Failed to update devmap_ value: %s\n",
+                strerror(errno));
+        }
+        return ret;
+    }
+
+References
+===========
+
+- https://lwn.net/Articles/728146/
+- https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/commit/?id=6f9d451ab1a33728adb72d7ff66a7b374d665176
+- https://elixir.bootlin.com/linux/latest/source/net/core/filter.c#L4106