Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next

Daniel Borkmann says:

====================
pull-request: bpf-next 2019-01-29

The following pull-request contains BPF updates for your *net-next* tree.

The main changes are:

1) Teach verifier dead code removal, this also allows for optimizing /
   removing conditional branches around dead code and to shrink the
   resulting image. Code store constrained architectures like nfp would
   have hard time doing this at JIT level, from Jakub.

2) Add JMP32 instructions to BPF ISA in order to allow for optimizing
   code generation for 32-bit sub-registers. Evaluation shows that this
   can result in code reduction of ~5-20% compared to 64 bit-only code
   generation. Also add implementation for most JITs, from Jiong.

3) Add support for __int128 types in BTF which is also needed for
   vmlinux's BTF conversion to work, from Yonghong.

4) Add a new command to bpftool in order to dump a list of BPF-related
   parameters from the system or for a specific network device e.g. in
   terms of available prog/map types or helper functions, from Quentin.

5) Add AF_XDP sock_diag interface for querying sockets from user
   space which provides information about the RX/TX/fill/completion
   rings, umem, memory usage etc, from Björn.

6) Add skb context access for skb_shared_info->gso_segs field, from Eric.

7) Add support for testing flow dissector BPF programs by extending
   existing BPF_PROG_TEST_RUN infrastructure, from Stanislav.

8) Split BPF kselftest's test_verifier into various subgroups of tests
   in order better deal with merge conflicts in this area, from Jakub.

9) Add support for queue/stack manipulations in bpftool, from Stanislav.

10) Document BTF, from Yonghong.

11) Dump supported ELF section names in libbpf on program load
    failure, from Taeung.

12) Silence a false positive compiler warning in verifier's BTF
    handling, from Peter.

13) Fix help string in bpftool's feature probing, from Prashant.

14) Remove duplicate includes in BPF kselftests, from Yue.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 885 insertions, 7 deletions

diff --git a/Documentation/bpf/btf.rst b/Documentation/bpf/btf.rst
new file mode 100644
index 000000000000..1d434c3a268d
--- /dev/null
+++ b/Documentation/bpf/btf.rst
@@ -0,0 +1,870 @@
+=====================
+BPF Type Format (BTF)
+=====================
+
+1. Introduction
+***************
+
+BTF (BPF Type Format) is the meta data format which
+encodes the debug info related to BPF program/map.
+The name BTF was used initially to describe
+data types. The BTF was later extended to include
+function info for defined subroutines, and line info
+for source/line information.
+
+The debug info is used for map pretty print, function
+signature, etc. The function signature enables better
+bpf program/function kernel symbol.
+The line info helps generate
+source annotated translated byte code, jited code
+and verifier log.
+
+The BTF specification contains two parts,
+  * BTF kernel API
+  * BTF ELF file format
+
+The kernel API is the contract between
+user space and kernel. The kernel verifies
+the BTF info before using it.
+The ELF file format is a user space contract
+between ELF file and libbpf loader.
+
+The type and string sections are part of the
+BTF kernel API, describing the debug info
+(mostly types related) referenced by the bpf program.
+These two sections are discussed in
+details in :ref:`BTF_Type_String`.
+
+.. _BTF_Type_String:
+
+2. BTF Type and String Encoding
+*******************************
+
+The file ``include/uapi/linux/btf.h`` provides high
+level definition on how types/strings are encoded.
+
+The beginning of data blob must be::
+
+    struct btf_header {
+        __u16   magic;
+        __u8    version;
+        __u8    flags;
+        __u32   hdr_len;
+
+        /* All offsets are in bytes relative to the end of this header */
+        __u32   type_off;       /* offset of type section       */
+        __u32   type_len;       /* length of type section       */
+        __u32   str_off;        /* offset of string section     */
+        __u32   str_len;        /* length of string section     */
+    };
+
+The magic is ``0xeB9F``, which has different encoding for big and little
+endian system, and can be used to test whether BTF is generated for
+big or little endian target.
+The btf_header is designed to be extensible with hdr_len equal to
+``sizeof(struct btf_header)`` when the data blob is generated.
+
+2.1 String Encoding
+===================
+
+The first string in the string section must be a null string.
+The rest of string table is a concatenation of other null-treminated
+strings.
+
+2.2 Type Encoding
+=================
+
+The type id ``0`` is reserved for ``void`` type.
+The type section is parsed sequentially and the type id is assigned to
+each recognized type starting from id ``1``.
+Currently, the following types are supported::
+
+    #define BTF_KIND_INT            1       /* Integer      */
+    #define BTF_KIND_PTR            2       /* Pointer      */
+    #define BTF_KIND_ARRAY          3       /* Array        */
+    #define BTF_KIND_STRUCT         4       /* Struct       */
+    #define BTF_KIND_UNION          5       /* Union        */
+    #define BTF_KIND_ENUM           6       /* Enumeration  */
+    #define BTF_KIND_FWD            7       /* Forward      */
+    #define BTF_KIND_TYPEDEF        8       /* Typedef      */
+    #define BTF_KIND_VOLATILE       9       /* Volatile     */
+    #define BTF_KIND_CONST          10      /* Const        */
+    #define BTF_KIND_RESTRICT       11      /* Restrict     */
+    #define BTF_KIND_FUNC           12      /* Function     */
+    #define BTF_KIND_FUNC_PROTO     13      /* Function Proto       */
+
+Note that the type section encodes debug info, not just pure types.
+``BTF_KIND_FUNC`` is not a type, and it represents a defined subprogram.
+
+Each type contains the following common data::
+
+    struct btf_type {
+        __u32 name_off;
+        /* "info" bits arrangement
+         * bits  0-15: vlen (e.g. # of struct's members)
+         * bits 16-23: unused
+         * bits 24-27: kind (e.g. int, ptr, array...etc)
+         * bits 28-30: unused
+         * bit     31: kind_flag, currently used by
+         *             struct, union and fwd
+         */
+        __u32 info;
+        /* "size" is used by INT, ENUM, STRUCT and UNION.
+         * "size" tells the size of the type it is describing.
+         *
+         * "type" is used by PTR, TYPEDEF, VOLATILE, CONST, RESTRICT,
+         * FUNC and FUNC_PROTO.
+         * "type" is a type_id referring to another type.
+         */
+        union {
+                __u32 size;
+                __u32 type;
+        };
+    };
+
+For certain kinds, the common data are followed by kind specific data.
+The ``name_off`` in ``struct btf_type`` specifies the offset in the string table.
+The following details encoding of each kind.
+
+2.2.1 BTF_KIND_INT
+~~~~~~~~~~~~~~~~~~
+
+``struct btf_type`` encoding requirement:
+ * ``name_off``: any valid offset
+ * ``info.kind_flag``: 0
+ * ``info.kind``: BTF_KIND_INT
+ * ``info.vlen``: 0
+ * ``size``: the size of the int type in bytes.
+
+``btf_type`` is followed by a ``u32`` with following bits arrangement::
+
+  #define BTF_INT_ENCODING(VAL)   (((VAL) & 0x0f000000) >> 24)
+  #define BTF_INT_OFFSET(VAL)     (((VAL  & 0x00ff0000)) >> 16)
+  #define BTF_INT_BITS(VAL)       ((VAL)  & 0x000000ff)
+
+The ``BTF_INT_ENCODING`` has the following attributes::
+
+  #define BTF_INT_SIGNED  (1 << 0)
+  #define BTF_INT_CHAR    (1 << 1)
+  #define BTF_INT_BOOL    (1 << 2)
+
+The ``BTF_INT_ENCODING()`` provides extra information, signness,
+char, or bool, for the int type. The char and bool encoding
+are mostly useful for pretty print. At most one encoding can
+be specified for the int type.
+
+The ``BTF_INT_BITS()`` specifies the number of actual bits held by
+this int type. For example, a 4-bit bitfield encodes
+``BTF_INT_BITS()`` equals to 4. The ``btf_type.size * 8``
+must be equal to or greater than ``BTF_INT_BITS()`` for the type.
+The maximum value of ``BTF_INT_BITS()`` is 128.
+
+The ``BTF_INT_OFFSET()`` specifies the starting bit offset to
+calculate values for this int. For example, a bitfield struct
+member has
+
+ * btf member bit offset 100 from the start of the structure,
+ * btf member pointing to an int type,
+ * the int type has ``BTF_INT_OFFSET() = 2`` and ``BTF_INT_BITS() = 4``
+
+Then in the struct memory layout, this member will occupy
+``4`` bits starting from bits ``100 + 2 = 102``.
+
+Alternatively, the bitfield struct member can be the following to
+access the same bits as the above:
+
+ * btf member bit offset 102,
+ * btf member pointing to an int type,
+ * the int type has ``BTF_INT_OFFSET() = 0`` and ``BTF_INT_BITS() = 4``
+
+The original intention of ``BTF_INT_OFFSET()`` is to provide
+flexibility of bitfield encoding.
+Currently, both llvm and pahole generates ``BTF_INT_OFFSET() = 0``
+for all int types.
+
+2.2.2 BTF_KIND_PTR
+~~~~~~~~~~~~~~~~~~
+
+``struct btf_type`` encoding requirement:
+  * ``name_off``: 0
+  * ``info.kind_flag``: 0
+  * ``info.kind``: BTF_KIND_PTR
+  * ``info.vlen``: 0
+  * ``type``: the pointee type of the pointer
+
+No additional type data follow ``btf_type``.
+
+2.2.3 BTF_KIND_ARRAY
+~~~~~~~~~~~~~~~~~~~~
+
+``struct btf_type`` encoding requirement:
+  * ``name_off``: 0
+  * ``info.kind_flag``: 0
+  * ``info.kind``: BTF_KIND_ARRAY
+  * ``info.vlen``: 0
+  * ``size/type``: 0, not used
+
+btf_type is followed by one "struct btf_array"::
+
+    struct btf_array {
+        __u32   type;
+        __u32   index_type;
+        __u32   nelems;
+    };
+
+The ``struct btf_array`` encoding:
+  * ``type``: the element type
+  * ``index_type``: the index type
+  * ``nelems``: the number of elements for this array (``0`` is also allowed).
+
+The ``index_type`` can be any regular int types
+(u8, u16, u32, u64, unsigned __int128).
+The original design of including ``index_type`` follows dwarf
+which has a ``index_type`` for its array type.
+Currently in BTF, beyond type verification, the ``index_type`` is not used.
+
+The ``struct btf_array`` allows chaining through element type to represent
+multiple dimensional arrays. For example, ``int a[5][6]``, the following
+type system illustrates the chaining:
+
+  * [1]: int
+  * [2]: array, ``btf_array.type = [1]``, ``btf_array.nelems = 6``
+  * [3]: array, ``btf_array.type = [2]``, ``btf_array.nelems = 5``
+
+Currently, both pahole and llvm collapse multiple dimensional array
+into one dimensional array, e.g., ``a[5][6]``, the btf_array.nelems
+equal to ``30``. This is because the original use case is map pretty
+print where the whole array is dumped out so one dimensional array
+is enough. As more BTF usage is explored, pahole and llvm can be
+changed to generate proper chained representation for
+multiple dimensional arrays.
+
+2.2.4 BTF_KIND_STRUCT
+~~~~~~~~~~~~~~~~~~~~~
+2.2.5 BTF_KIND_UNION
+~~~~~~~~~~~~~~~~~~~~
+
+``struct btf_type`` encoding requirement:
+  * ``name_off``: 0 or offset to a valid C identifier
+  * ``info.kind_flag``: 0 or 1
+  * ``info.kind``: BTF_KIND_STRUCT or BTF_KIND_UNION
+  * ``info.vlen``: the number of struct/union members
+  * ``info.size``: the size of the struct/union in bytes
+
+``btf_type`` is followed by ``info.vlen`` number of ``struct btf_member``.::
+
+    struct btf_member {
+        __u32   name_off;
+        __u32   type;
+        __u32   offset;
+    };
+
+``struct btf_member`` encoding:
+  * ``name_off``: offset to a valid C identifier
+  * ``type``: the member type
+  * ``offset``: <see below>
+
+If the type info ``kind_flag`` is not set, the offset contains
+only bit offset of the member. Note that the base type of the
+bitfield can only be int or enum type. If the bitfield size
+is 32, the base type can be either int or enum type.
+If the bitfield size is not 32, the base type must be int,
+and int type ``BTF_INT_BITS()`` encodes the bitfield size.
+
+If the ``kind_flag`` is set, the ``btf_member.offset``
+contains both member bitfield size and bit offset. The
+bitfield size and bit offset are calculated as below.::
+
+  #define BTF_MEMBER_BITFIELD_SIZE(val)   ((val) >> 24)
+  #define BTF_MEMBER_BIT_OFFSET(val)      ((val) & 0xffffff)
+
+In this case, if the base type is an int type, it must
+be a regular int type:
+
+  * ``BTF_INT_OFFSET()`` must be 0.
+  * ``BTF_INT_BITS()`` must be equal to ``{1,2,4,8,16} * 8``.
+
+The following kernel patch introduced ``kind_flag`` and
+explained why both modes exist:
+
+  https://github.com/torvalds/linux/commit/9d5f9f701b1891466fb3dbb1806ad97716f95cc3#diff-fa650a64fdd3968396883d2fe8215ff3
+
+2.2.6 BTF_KIND_ENUM
+~~~~~~~~~~~~~~~~~~~
+
+``struct btf_type`` encoding requirement:
+  * ``name_off``: 0 or offset to a valid C identifier
+  * ``info.kind_flag``: 0
+  * ``info.kind``: BTF_KIND_ENUM
+  * ``info.vlen``: number of enum values
+  * ``size``: 4
+
+``btf_type`` is followed by ``info.vlen`` number of ``struct btf_enum``.::
+
+    struct btf_enum {
+        __u32   name_off;
+        __s32   val;
+    };
+
+The ``btf_enum`` encoding:
+  * ``name_off``: offset to a valid C identifier
+  * ``val``: any value
+
+2.2.7 BTF_KIND_FWD
+~~~~~~~~~~~~~~~~~~
+
+``struct btf_type`` encoding requirement:
+  * ``name_off``: offset to a valid C identifier
+  * ``info.kind_flag``: 0 for struct, 1 for union
+  * ``info.kind``: BTF_KIND_FWD
+  * ``info.vlen``: 0
+  * ``type``: 0
+
+No additional type data follow ``btf_type``.
+
+2.2.8 BTF_KIND_TYPEDEF
+~~~~~~~~~~~~~~~~~~~~~~
+
+``struct btf_type`` encoding requirement:
+  * ``name_off``: offset to a valid C identifier
+  * ``info.kind_flag``: 0
+  * ``info.kind``: BTF_KIND_TYPEDEF
+  * ``info.vlen``: 0
+  * ``type``: the type which can be referred by name at ``name_off``
+
+No additional type data follow ``btf_type``.
+
+2.2.9 BTF_KIND_VOLATILE
+~~~~~~~~~~~~~~~~~~~~~~~
+
+``struct btf_type`` encoding requirement:
+  * ``name_off``: 0
+  * ``info.kind_flag``: 0
+  * ``info.kind``: BTF_KIND_VOLATILE
+  * ``info.vlen``: 0
+  * ``type``: the type with ``volatile`` qualifier
+
+No additional type data follow ``btf_type``.
+
+2.2.10 BTF_KIND_CONST
+~~~~~~~~~~~~~~~~~~~~~
+
+``struct btf_type`` encoding requirement:
+  * ``name_off``: 0
+  * ``info.kind_flag``: 0
+  * ``info.kind``: BTF_KIND_CONST
+  * ``info.vlen``: 0
+  * ``type``: the type with ``const`` qualifier
+
+No additional type data follow ``btf_type``.
+
+2.2.11 BTF_KIND_RESTRICT
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+``struct btf_type`` encoding requirement:
+  * ``name_off``: 0
+  * ``info.kind_flag``: 0
+  * ``info.kind``: BTF_KIND_RESTRICT
+  * ``info.vlen``: 0
+  * ``type``: the type with ``restrict`` qualifier
+
+No additional type data follow ``btf_type``.
+
+2.2.12 BTF_KIND_FUNC
+~~~~~~~~~~~~~~~~~~~~
+
+``struct btf_type`` encoding requirement:
+  * ``name_off``: offset to a valid C identifier
+  * ``info.kind_flag``: 0
+  * ``info.kind``: BTF_KIND_FUNC
+  * ``info.vlen``: 0
+  * ``type``: a BTF_KIND_FUNC_PROTO type
+
+No additional type data follow ``btf_type``.
+
+A BTF_KIND_FUNC defines, not a type, but a subprogram (function) whose
+signature is defined by ``type``. The subprogram is thus an instance of
+that type. The BTF_KIND_FUNC may in turn be referenced by a func_info in
+the :ref:`BTF_Ext_Section` (ELF) or in the arguments to
+:ref:`BPF_Prog_Load` (ABI).
+
+2.2.13 BTF_KIND_FUNC_PROTO
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+``struct btf_type`` encoding requirement:
+  * ``name_off``: 0
+  * ``info.kind_flag``: 0
+  * ``info.kind``: BTF_KIND_FUNC_PROTO
+  * ``info.vlen``: # of parameters
+  * ``type``: the return type
+
+``btf_type`` is followed by ``info.vlen`` number of ``struct btf_param``.::
+
+    struct btf_param {
+        __u32   name_off;
+        __u32   type;
+    };
+
+If a BTF_KIND_FUNC_PROTO type is referred by a BTF_KIND_FUNC type,
+then ``btf_param.name_off`` must point to a valid C identifier
+except for the possible last argument representing the variable
+argument. The btf_param.type refers to parameter type.
+
+If the function has variable arguments, the last parameter
+is encoded with ``name_off = 0`` and ``type = 0``.
+
+3. BTF Kernel API
+*****************
+
+The following bpf syscall command involves BTF:
+   * BPF_BTF_LOAD: load a blob of BTF data into kernel
+   * BPF_MAP_CREATE: map creation with btf key and value type info.
+   * BPF_PROG_LOAD: prog load with btf function and line info.
+   * BPF_BTF_GET_FD_BY_ID: get a btf fd
+   * BPF_OBJ_GET_INFO_BY_FD: btf, func_info, line_info
+     and other btf related info are returned.
+
+The workflow typically looks like:
+::
+
+  Application:
+      BPF_BTF_LOAD
+          |
+          v
+      BPF_MAP_CREATE and BPF_PROG_LOAD
+          |
+          V
+      ......
+
+  Introspection tool:
+      ......
+      BPF_{PROG,MAP}_GET_NEXT_ID (get prog/map id's)
+          |
+          V
+      BPF_{PROG,MAP}_GET_FD_BY_ID (get a prog/map fd)
+          |
+          V
+      BPF_OBJ_GET_INFO_BY_FD (get bpf_prog_info/bpf_map_info with btf_id)
+          |                                     |
+          V                                     |
+      BPF_BTF_GET_FD_BY_ID (get btf_fd)         |
+          |                                     |
+          V                                     |
+      BPF_OBJ_GET_INFO_BY_FD (get btf)          |
+          |                                     |
+          V                                     V
+      pretty print types, dump func signatures and line info, etc.
+
+
+3.1 BPF_BTF_LOAD
+================
+
+Load a blob of BTF data into kernel. A blob of data
+described in :ref:`BTF_Type_String`
+can be directly loaded into the kernel.
+A ``btf_fd`` returns to userspace.
+
+3.2 BPF_MAP_CREATE
+==================
+
+A map can be created with ``btf_fd`` and specified key/value type id.::
+
+    __u32   btf_fd;         /* fd pointing to a BTF type data */
+    __u32   btf_key_type_id;        /* BTF type_id of the key */
+    __u32   btf_value_type_id;      /* BTF type_id of the value */
+
+In libbpf, the map can be defined with extra annotation like below:
+::
+
+    struct bpf_map_def SEC("maps") btf_map = {
+        .type = BPF_MAP_TYPE_ARRAY,
+        .key_size = sizeof(int),
+        .value_size = sizeof(struct ipv_counts),
+        .max_entries = 4,
+    };
+    BPF_ANNOTATE_KV_PAIR(btf_map, int, struct ipv_counts);
+
+Here, the parameters for macro BPF_ANNOTATE_KV_PAIR are map name,
+key and value types for the map.
+During ELF parsing, libbpf is able to extract key/value type_id's
+and assigned them to BPF_MAP_CREATE attributes automatically.
+
+.. _BPF_Prog_Load:
+
+3.3 BPF_PROG_LOAD
+=================
+
+During prog_load, func_info and line_info can be passed to kernel with
+proper values for the following attributes:
+::
+
+    __u32           insn_cnt;
+    __aligned_u64   insns;
+    ......
+    __u32           prog_btf_fd;    /* fd pointing to BTF type data */
+    __u32           func_info_rec_size;     /* userspace bpf_func_info size */
+    __aligned_u64   func_info;      /* func info */
+    __u32           func_info_cnt;  /* number of bpf_func_info records */
+    __u32           line_info_rec_size;     /* userspace bpf_line_info size */
+    __aligned_u64   line_info;      /* line info */
+    __u32           line_info_cnt;  /* number of bpf_line_info records */
+
+The func_info and line_info are an array of below, respectively.::
+
+    struct bpf_func_info {
+        __u32   insn_off; /* [0, insn_cnt - 1] */
+        __u32   type_id;  /* pointing to a BTF_KIND_FUNC type */
+    };
+    struct bpf_line_info {
+        __u32   insn_off; /* [0, insn_cnt - 1] */
+        __u32   file_name_off; /* offset to string table for the filename */
+        __u32   line_off; /* offset to string table for the source line */
+        __u32   line_col; /* line number and column number */
+    };
+
+func_info_rec_size is the size of each func_info record, and line_info_rec_size
+is the size of each line_info record. Passing the record size to kernel make
+it possible to extend the record itself in the future.
+
+Below are requirements for func_info:
+  * func_info[0].insn_off must be 0.
+  * the func_info insn_off is in strictly increasing order and matches
+    bpf func boundaries.
+
+Below are requirements for line_info:
+  * the first insn in each func must points to a line_info record.
+  * the line_info insn_off is in strictly increasing order.
+
+For line_info, the line number and column number are defined as below:
+::
+
+    #define BPF_LINE_INFO_LINE_NUM(line_col)        ((line_col) >> 10)
+    #define BPF_LINE_INFO_LINE_COL(line_col)        ((line_col) & 0x3ff)
+
+3.4 BPF_{PROG,MAP}_GET_NEXT_ID
+
+In kernel, every loaded program, map or btf has a unique id.
+The id won't change during the life time of the program, map or btf.
+
+The bpf syscall command BPF_{PROG,MAP}_GET_NEXT_ID
+returns all id's, one for each command, to user space, for bpf
+program or maps,
+so the inspection tool can inspect all programs and maps.
+
+3.5 BPF_{PROG,MAP}_GET_FD_BY_ID
+
+The introspection tool cannot use id to get details about program or maps.
+A file descriptor needs to be obtained first for reference counting purpose.
+
+3.6 BPF_OBJ_GET_INFO_BY_FD
+==========================
+
+Once a program/map fd is acquired, the introspection tool can
+get the detailed information from kernel about this fd,
+some of which is btf related. For example,
+``bpf_map_info`` returns ``btf_id``, key/value type id.
+``bpf_prog_info`` returns ``btf_id``, func_info and line info
+for translated bpf byte codes, and jited_line_info.
+
+3.7 BPF_BTF_GET_FD_BY_ID
+========================
+
+With ``btf_id`` obtained in ``bpf_map_info`` and ``bpf_prog_info``,
+bpf syscall command BPF_BTF_GET_FD_BY_ID can retrieve a btf fd.
+Then, with command BPF_OBJ_GET_INFO_BY_FD, the btf blob, originally
+loaded into the kernel with BPF_BTF_LOAD, can be retrieved.
+
+With the btf blob, ``bpf_map_info`` and ``bpf_prog_info``, the introspection
+tool has full btf knowledge and is able to pretty print map key/values,
+dump func signatures, dump line info along with byte/jit codes.
+
+4. ELF File Format Interface
+****************************
+
+4.1 .BTF section
+================
+
+The .BTF section contains type and string data. The format of this section
+is same as the one describe in :ref:`BTF_Type_String`.
+
+.. _BTF_Ext_Section:
+
+4.2 .BTF.ext section
+====================
+
+The .BTF.ext section encodes func_info and line_info which
+needs loader manipulation before loading into the kernel.
+
+The specification for .BTF.ext section is defined at
+``tools/lib/bpf/btf.h`` and ``tools/lib/bpf/btf.c``.
+
+The current header of .BTF.ext section::
+
+    struct btf_ext_header {
+        __u16   magic;
+        __u8    version;
+        __u8    flags;
+        __u32   hdr_len;
+
+        /* All offsets are in bytes relative to the end of this header */
+        __u32   func_info_off;
+        __u32   func_info_len;
+        __u32   line_info_off;
+        __u32   line_info_len;
+    };
+
+It is very similar to .BTF section. Instead of type/string section,
+it contains func_info and line_info section. See :ref:`BPF_Prog_Load`
+for details about func_info and line_info record format.
+
+The func_info is organized as below.::
+
+     func_info_rec_size
+     btf_ext_info_sec for section #1 /* func_info for section #1 */
+     btf_ext_info_sec for section #2 /* func_info for section #2 */
+     ...
+
+``func_info_rec_size`` specifies the size of ``bpf_func_info`` structure
+when .BTF.ext is generated. btf_ext_info_sec, defined below, is
+the func_info for each specific ELF section.::
+
+     struct btf_ext_info_sec {
+        __u32   sec_name_off; /* offset to section name */
+        __u32   num_info;
+        /* Followed by num_info * record_size number of bytes */
+        __u8    data[0];
+     };
+
+Here, num_info must be greater than 0.
+
+The line_info is organized as below.::
+
+     line_info_rec_size
+     btf_ext_info_sec for section #1 /* line_info for section #1 */
+     btf_ext_info_sec for section #2 /* line_info for section #2 */
+     ...
+
+``line_info_rec_size`` specifies the size of ``bpf_line_info`` structure
+when .BTF.ext is generated.
+
+The interpretation of ``bpf_func_info->insn_off`` and
+``bpf_line_info->insn_off`` is different between kernel API and ELF API.
+For kernel API, the ``insn_off`` is the instruction offset in the unit
+of ``struct bpf_insn``. For ELF API, the ``insn_off`` is the byte offset
+from the beginning of section (``btf_ext_info_sec->sec_name_off``).
+
+5. Using BTF
+************
+
+5.1 bpftool map pretty print
+============================
+
+With BTF, the map key/value can be printed based on fields rather than
+simply raw bytes. This is especially
+valuable for large structure or if you data structure
+has bitfields. For example, for the following map,::
+
+      enum A { A1, A2, A3, A4, A5 };
+      typedef enum A ___A;
+      struct tmp_t {
+           char a1:4;
+           int  a2:4;
+           int  :4;
+           __u32 a3:4;
+           int b;
+           ___A b1:4;
+           enum A b2:4;
+      };
+      struct bpf_map_def SEC("maps") tmpmap = {
+           .type = BPF_MAP_TYPE_ARRAY,
+           .key_size = sizeof(__u32),
+           .value_size = sizeof(struct tmp_t),
+           .max_entries = 1,
+      };
+      BPF_ANNOTATE_KV_PAIR(tmpmap, int, struct tmp_t);
+
+bpftool is able to pretty print like below:
+::
+
+      [{
+            "key": 0,
+            "value": {
+                "a1": 0x2,
+                "a2": 0x4,
+                "a3": 0x6,
+                "b": 7,
+                "b1": 0x8,
+                "b2": 0xa
+            }
+        }
+      ]
+
+5.2 bpftool prog dump
+=====================
+
+The following is an example to show func_info and line_info
+can help prog dump with better kernel symbol name, function prototype
+and line information.::
+
+    $ bpftool prog dump jited pinned /sys/fs/bpf/test_btf_haskv
+    [...]
+    int test_long_fname_2(struct dummy_tracepoint_args * arg):
+    bpf_prog_44a040bf25481309_test_long_fname_2:
+    ; static int test_long_fname_2(struct dummy_tracepoint_args *arg)
+       0:   push   %rbp
+       1:   mov    %rsp,%rbp
+       4:   sub    $0x30,%rsp
+       b:   sub    $0x28,%rbp
+       f:   mov    %rbx,0x0(%rbp)
+      13:   mov    %r13,0x8(%rbp)
+      17:   mov    %r14,0x10(%rbp)
+      1b:   mov    %r15,0x18(%rbp)
+      1f:   xor    %eax,%eax
+      21:   mov    %rax,0x20(%rbp)
+      25:   xor    %esi,%esi
+    ; int key = 0;
+      27:   mov    %esi,-0x4(%rbp)
+    ; if (!arg->sock)
+      2a:   mov    0x8(%rdi),%rdi
+    ; if (!arg->sock)
+      2e:   cmp    $0x0,%rdi
+      32:   je     0x0000000000000070
+      34:   mov    %rbp,%rsi
+    ; counts = bpf_map_lookup_elem(&btf_map, &key);
+    [...]
+
+5.3 verifier log
+================
+
+The following is an example how line_info can help verifier failure debug.::
+
+       /* The code at tools/testing/selftests/bpf/test_xdp_noinline.c
+        * is modified as below.
+        */
+       data = (void *)(long)xdp->data;
+       data_end = (void *)(long)xdp->data_end;
+       /*
+       if (data + 4 > data_end)
+               return XDP_DROP;
+       */
+       *(u32 *)data = dst->dst;
+
+    $ bpftool prog load ./test_xdp_noinline.o /sys/fs/bpf/test_xdp_noinline type xdp
+        ; data = (void *)(long)xdp->data;
+        224: (79) r2 = *(u64 *)(r10 -112)
+        225: (61) r2 = *(u32 *)(r2 +0)
+        ; *(u32 *)data = dst->dst;
+        226: (63) *(u32 *)(r2 +0) = r1
+        invalid access to packet, off=0 size=4, R2(id=0,off=0,r=0)
+        R2 offset is outside of the packet
+
+6. BTF Generation
+*****************
+
+You need latest pahole
+
+  https://git.kernel.org/pub/scm/devel/pahole/pahole.git/
+
+or llvm (8.0 or later). The pahole acts as a dwarf2btf converter. It doesn't support .BTF.ext
+and btf BTF_KIND_FUNC type yet. For example,::
+
+      -bash-4.4$ cat t.c
+      struct t {
+        int a:2;
+        int b:3;
+        int c:2;
+      } g;
+      -bash-4.4$ gcc -c -O2 -g t.c
+      -bash-4.4$ pahole -JV t.o
+      File t.o:
+      [1] STRUCT t kind_flag=1 size=4 vlen=3
+              a type_id=2 bitfield_size=2 bits_offset=0
+              b type_id=2 bitfield_size=3 bits_offset=2
+              c type_id=2 bitfield_size=2 bits_offset=5
+      [2] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED
+
+The llvm is able to generate .BTF and .BTF.ext directly with -g for bpf target only.
+The assembly code (-S) is able to show the BTF encoding in assembly format.::
+
+    -bash-4.4$ cat t2.c
+    typedef int __int32;
+    struct t2 {
+      int a2;
+      int (*f2)(char q1, __int32 q2, ...);
+      int (*f3)();
+    } g2;
+    int main() { return 0; }
+    int test() { return 0; }
+    -bash-4.4$ clang -c -g -O2 -target bpf t2.c
+    -bash-4.4$ readelf -S t2.o
+      ......
+      [ 8] .BTF              PROGBITS         0000000000000000  00000247
+           000000000000016e  0000000000000000           0     0     1
+      [ 9] .BTF.ext          PROGBITS         0000000000000000  000003b5
+           0000000000000060  0000000000000000           0     0     1
+      [10] .rel.BTF.ext      REL              0000000000000000  000007e0
+           0000000000000040  0000000000000010          16     9     8
+      ......
+    -bash-4.4$ clang -S -g -O2 -target bpf t2.c
+    -bash-4.4$ cat t2.s
+      ......
+            .section        .BTF,"",@progbits
+            .short  60319                   # 0xeb9f
+            .byte   1
+            .byte   0
+            .long   24
+            .long   0
+            .long   220
+            .long   220
+            .long   122
+            .long   0                       # BTF_KIND_FUNC_PROTO(id = 1)
+            .long   218103808               # 0xd000000
+            .long   2
+            .long   83                      # BTF_KIND_INT(id = 2)
+            .long   16777216                # 0x1000000
+            .long   4
+            .long   16777248                # 0x1000020
+      ......
+            .byte   0                       # string offset=0
+            .ascii  ".text"                 # string offset=1
+            .byte   0
+            .ascii  "/home/yhs/tmp-pahole/t2.c" # string offset=7
+            .byte   0
+            .ascii  "int main() { return 0; }" # string offset=33
+            .byte   0
+            .ascii  "int test() { return 0; }" # string offset=58
+            .byte   0
+            .ascii  "int"                   # string offset=83
+      ......
+            .section        .BTF.ext,"",@progbits
+            .short  60319                   # 0xeb9f
+            .byte   1
+            .byte   0
+            .long   24
+            .long   0
+            .long   28
+            .long   28
+            .long   44
+            .long   8                       # FuncInfo
+            .long   1                       # FuncInfo section string offset=1
+            .long   2
+            .long   .Lfunc_begin0
+            .long   3
+            .long   .Lfunc_begin1
+            .long   5
+            .long   16                      # LineInfo
+            .long   1                       # LineInfo section string offset=1
+            .long   2
+            .long   .Ltmp0
+            .long   7
+            .long   33
+            .long   7182                    # Line 7 Col 14
+            .long   .Ltmp3
+            .long   7
+            .long   58
+            .long   8206                    # Line 8 Col 14
+
+7. Testing
+**********
+
+Kernel bpf selftest `test_btf.c` provides extensive set of BTF related tests.
diff --git a/Documentation/bpf/index.rst b/Documentation/bpf/index.rst
index 00a8450a602f..4e77932959cc 100644
--- a/Documentation/bpf/index.rst
+++ b/Documentation/bpf/index.rst
@@ -15,6 +15,13 @@ that goes into great technical depth about the BPF Architecture.
 The primary info for the bpf syscall is available in the `man-pages`_
 for `bpf(2)`_.
 
+BPF Type Format (BTF)
+=====================
+
+.. toctree::
+   :maxdepth: 1
+
+   btf
 
 
 Frequently asked questions (FAQ)
diff --git a/Documentation/networking/filter.txt b/Documentation/networking/filter.txt
index 2196b824e96c..01603bc2eff1 100644
--- a/Documentation/networking/filter.txt
+++ b/Documentation/networking/filter.txt
@@ -865,7 +865,7 @@ Three LSB bits store instruction class which is one of:
   BPF_STX   0x03          BPF_STX   0x03
   BPF_ALU   0x04          BPF_ALU   0x04
   BPF_JMP   0x05          BPF_JMP   0x05
-  BPF_RET   0x06          [ class 6 unused, for future if needed ]
+  BPF_RET   0x06          BPF_JMP32 0x06
   BPF_MISC  0x07          BPF_ALU64 0x07
 
 When BPF_CLASS(code) == BPF_ALU or BPF_JMP, 4th bit encodes source operand ...
@@ -902,9 +902,9 @@ If BPF_CLASS(code) == BPF_ALU or BPF_ALU64 [ in eBPF ], BPF_OP(code) is one of:
   BPF_ARSH  0xc0  /* eBPF only: sign extending shift right */
   BPF_END   0xd0  /* eBPF only: endianness conversion */
 
-If BPF_CLASS(code) == BPF_JMP, BPF_OP(code) is one of:
+If BPF_CLASS(code) == BPF_JMP or BPF_JMP32 [ in eBPF ], BPF_OP(code) is one of:
 
-  BPF_JA    0x00
+  BPF_JA    0x00  /* BPF_JMP only */
   BPF_JEQ   0x10
   BPF_JGT   0x20
   BPF_JGE   0x30
@@ -912,8 +912,8 @@ If BPF_CLASS(code) == BPF_JMP, BPF_OP(code) is one of:
   BPF_JNE   0x50  /* eBPF only: jump != */
   BPF_JSGT  0x60  /* eBPF only: signed '>' */
   BPF_JSGE  0x70  /* eBPF only: signed '>=' */
-  BPF_CALL  0x80  /* eBPF only: function call */
-  BPF_EXIT  0x90  /* eBPF only: function return */
+  BPF_CALL  0x80  /* eBPF BPF_JMP only: function call */
+  BPF_EXIT  0x90  /* eBPF BPF_JMP only: function return */
   BPF_JLT   0xa0  /* eBPF only: unsigned '<' */
   BPF_JLE   0xb0  /* eBPF only: unsigned '<=' */
   BPF_JSLT  0xc0  /* eBPF only: signed '<' */
@@ -936,8 +936,9 @@ Classic BPF wastes the whole BPF_RET class to represent a single 'ret'
 operation. Classic BPF_RET | BPF_K means copy imm32 into return register
 and perform function exit. eBPF is modeled to match CPU, so BPF_JMP | BPF_EXIT
 in eBPF means function exit only. The eBPF program needs to store return
-value into register R0 before doing a BPF_EXIT. Class 6 in eBPF is currently
-unused and reserved for future use.
+value into register R0 before doing a BPF_EXIT. Class 6 in eBPF is used as
+BPF_JMP32 to mean exactly the same operations as BPF_JMP, but with 32-bit wide
+operands for the comparisons instead.
 
 For load and store instructions the 8-bit 'code' field is divided as: