1. 03 May, 2018 3 commits
    • Björn Töpel's avatar
      xsk: add user memory registration support sockopt · c0c77d8f
      Björn Töpel authored
      In this commit the base structure of the AF_XDP address family is set
      up. Further, we introduce the abilty register a window of user memory
      to the kernel via the XDP_UMEM_REG setsockopt syscall. The memory
      window is viewed by an AF_XDP socket as a set of equally large
      frames. After a user memory registration all frames are "owned" by the
      user application, and not the kernel.
      
      v2: More robust checks on umem creation and unaccount on error.
          Call set_page_dirty_lock on cleanup.
          Simplified xdp_umem_reg.
      Co-authored-by: default avatarMagnus Karlsson <magnus.karlsson@intel.com>
      Signed-off-by: default avatarMagnus Karlsson <magnus.karlsson@intel.com>
      Signed-off-by: default avatarBjörn Töpel <bjorn.topel@intel.com>
      Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      c0c77d8f
    • Björn Töpel's avatar
      net: initial AF_XDP skeleton · 68e8b849
      Björn Töpel authored
      Buildable skeleton of AF_XDP without any functionality. Just what it
      takes to register a new address family.
      Signed-off-by: default avatarBjörn Töpel <bjorn.topel@intel.com>
      Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      68e8b849
    • Wang YanQing's avatar
      bpf, x86_32: add eBPF JIT compiler for ia32 · 03f5781b
      Wang YanQing authored
      The JIT compiler emits ia32 bit instructions. Currently, It supports eBPF
      only. Classic BPF is supported because of the conversion by BPF core.
      
      Almost all instructions from eBPF ISA supported except the following:
      BPF_ALU64 | BPF_DIV | BPF_K
      BPF_ALU64 | BPF_DIV | BPF_X
      BPF_ALU64 | BPF_MOD | BPF_K
      BPF_ALU64 | BPF_MOD | BPF_X
      BPF_STX | BPF_XADD | BPF_W
      BPF_STX | BPF_XADD | BPF_DW
      
      It doesn't support BPF_JMP|BPF_CALL with BPF_PSEUDO_CALL at the moment.
      
      IA32 has few general purpose registers, EAX|EDX|ECX|EBX|ESI|EDI. I use
      EAX|EDX|ECX|EBX as temporary registers to simulate instructions in eBPF
      ISA, and allocate ESI|EDI to BPF_REG_AX for constant blinding, all others
      eBPF registers, R0-R10, are simulated through scratch space on stack.
      
      The reasons behind the hardware registers allocation policy are:
      1:MUL need EAX:EDX, shift operation need ECX, so they aren't fit
        for general eBPF 64bit register simulation.
      2:We need at least 4 registers to simulate most eBPF ISA operations
        on registers operands instead of on register&memory operands.
      3:We need to put BPF_REG_AX on hardware registers, or constant blinding
        will degrade jit performance heavily.
      
      Tested on PC (Intel(R) Core(TM) i5-5200U CPU).
      Testing results on i5-5200U:
      1) test_bpf: Summary: 349 PASSED, 0 FAILED, [319/341 JIT'ed]
      2) test_progs: Summary: 83 PASSED, 0 FAILED.
      3) test_lpm: OK
      4) test_lru_map: OK
      5) test_verifier: Summary: 828 PASSED, 0 FAILED.
      
      Above tests are all done in following two conditions separately:
      1:bpf_jit_enable=1 and bpf_jit_harden=0
      2:bpf_jit_enable=1 and bpf_jit_harden=2
      
      Below are some numbers for this jit implementation:
      Note:
        I run test_progs in kselftest 100 times continuously for every condition,
        the numbers are in format: total/times=avg.
        The numbers that test_bpf reports show almost the same relation.
      
      a:jit_enable=0 and jit_harden=0            b:jit_enable=1 and jit_harden=0
        test_pkt_access:PASS:ipv4:15622/100=156    test_pkt_access:PASS:ipv4:10674/100=106
        test_pkt_access:PASS:ipv6:9130/100=91      test_pkt_access:PASS:ipv6:4855/100=48
        test_xdp:PASS:ipv4:240198/100=2401         test_xdp:PASS:ipv4:138912/100=1389
        test_xdp:PASS:ipv6:137326/100=1373         test_xdp:PASS:ipv6:68542/100=685
        test_l4lb:PASS:ipv4:61100/100=611          test_l4lb:PASS:ipv4:37302/100=373
        test_l4lb:PASS:ipv6:101000/100=1010        test_l4lb:PASS:ipv6:55030/100=550
      
      c:jit_enable=1 and jit_harden=2
        test_pkt_access:PASS:ipv4:10558/100=105
        test_pkt_access:PASS:ipv6:5092/100=50
        test_xdp:PASS:ipv4:131902/100=1319
        test_xdp:PASS:ipv6:77932/100=779
        test_l4lb:PASS:ipv4:38924/100=389
        test_l4lb:PASS:ipv6:57520/100=575
      
      The numbers show we get 30%~50% improvement.
      
      See Documentation/networking/filter.txt for more information.
      
      Changelog:
      
       Changes v5-v6:
       1:Add do {} while (0) to RETPOLINE_RAX_BPF_JIT for
         consistence reason.
       2:Clean up non-standard comments, reported by Daniel Borkmann.
       3:Fix a memory leak issue, repoted by Daniel Borkmann.
      
       Changes v4-v5:
       1:Delete is_on_stack, BPF_REG_AX is the only one
         on real hardware registers, so just check with
         it.
       2:Apply commit 1612a981 ("bpf, x64: fix JIT emission
         for dead code"), suggested by Daniel Borkmann.
      
       Changes v3-v4:
       1:Fix changelog in commit.
         I install llvm-6.0, then test_progs willn't report errors.
         I submit another patch:
         "bpf: fix misaligned access for BPF_PROG_TYPE_PERF_EVENT program type on x86_32 platform"
         to fix another problem, after that patch, test_verifier willn't report errors too.
       2:Fix clear r0[1] twice unnecessarily in *BPF_IND|BPF_ABS* simulation.
      
       Changes v2-v3:
       1:Move BPF_REG_AX to real hardware registers for performance reason.
       3:Using bpf_load_pointer instead of bpf_jit32.S, suggested by Daniel Borkmann.
       4:Delete partial codes in 1c2a088a, suggested by Daniel Borkmann.
       5:Some bug fixes and comments improvement.
      
       Changes v1-v2:
       1:Fix bug in emit_ia32_neg64.
       2:Fix bug in emit_ia32_arsh_r64.
       3:Delete filename in top level comment, suggested by Thomas Gleixner.
       4:Delete unnecessary boiler plate text, suggested by Thomas Gleixner.
       5:Rewrite some words in changelog.
       6:CodingSytle improvement and a little more comments.
      Signed-off-by: default avatarWang YanQing <udknight@gmail.com>
      Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      03f5781b
  2. 02 May, 2018 2 commits
    • Quentin Monnet's avatar
      bpf: relax constraints on formatting for eBPF helper documentation · 6f96674d
      Quentin Monnet authored
      The Python script used to parse and extract eBPF helpers documentation
      from include/uapi/linux/bpf.h expects a very specific formatting for the
      descriptions (single dot represents a space, '>' stands for a tab):
      
          /*
           ...
           *.int bpf_helper(list of arguments)
           *.>    Description
           *.>    >       Start of description
           *.>    >       Another line of description
           *.>    >       And yet another line of description
           *.>    Return
           *.>    >       0 on success, or a negative error in case of failure
           ...
           */
      
      This is too strict, and painful for developers who wants to add
      documentation for new helpers. Worse, it is extremely difficult to check
      that the formatting is correct during reviews. Change the format
      expected by the script and make it more flexible. The script now works
      whether or not the initial space (right after the star) is present, and
      accepts both tabs and white spaces (or a combination of both) for
      indenting description sections and contents.
      
      Concretely, something like the following would now be supported:
      
          /*
           ...
           *int bpf_helper(list of arguments)
           *......Description
           *.>    >       Start of description...
           *>     >       Another line of description
           *..............And yet another line of description
           *>     Return
           *.>    ........0 on success, or a negative error in case of failure
           ...
           */
      
      While at it, remove unnecessary carets from each regex used with match()
      in the script. They are redundant, as match() tries to match from the
      beginning of the string by default.
      
      v2: Remove unnecessary caret when a regex is used with match().
      Signed-off-by: default avatarQuentin Monnet <quentin.monnet@netronome.com>
      Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      6f96674d
    • Ingo Molnar's avatar
      x86/bpf: Clean up non-standard comments, to make the code more readable · a2c7a983
      Ingo Molnar authored
      So by chance I looked into x86 assembly in arch/x86/net/bpf_jit_comp.c and
      noticed the weird and inconsistent comment style it mistakenly learned from
      the networking code:
      
       /* Multi-line comment ...
        * ... looks like this.
        */
      
      Fix this to use the standard comment style specified in Documentation/CodingStyle
      and used in arch/x86/ as well:
      
       /*
        * Multi-line comment ...
        * ... looks like this.
        */
      
      Also, to quote Linus's ... more explicit views about this:
      
        http://article.gmane.org/gmane.linux.kernel.cryptoapi/21066
      
        > But no, the networking code picked *none* of the above sane formats.
        > Instead, it picked these two models that are just half-arsed
        > shit-for-brains:
        >
        >  (no)
        >      /* This is disgusting drug-induced
        >        * crap, and should die
        >        */
        >
        >   (no-no-no)
        >       /* This is also very nasty
        >        * and visually unbalanced */
        >
        > Please. The networking code actually has the *worst* possible comment
        > style. You can literally find that (no-no-no) style, which is just
        > really horribly disgusting and worse than the otherwise fairly similar
        > (d) in pretty much every way.
      
      Also improve the comments and some other details while at it:
      
       - Don't mix same-line and previous-line comment style on otherwise
         identical code patterns within the same function,
      
       - capitalize 'BPF' and x86 register names consistently,
      
       - capitalize sentences consistently,
      
       - instead of 'x64' use 'x86-64': x64 is a Microsoft specific term,
      
       - use more consistent punctuation,
      
       - use standard coding style in macros as well,
      
       - fix typos and a few other minor details.
      
      Consistent coding style is not optional, at least in arch/x86/.
      
      No change in functionality.
      
      ( In case this commit causes conflicts with pending development code
        I'll be glad to help resolve any conflicts! )
      Acked-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Borislav Petkov <bp@alien8.de>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: David S. Miller <davem@davemloft.net>
      Cc: Eric Dumazet <edumazet@google.com>
      Cc: Daniel Borkmann <daniel@iogearbox.net>
      Cc: Alexei Starovoitov <ast@fb.com>
      Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
      Cc: netdev@vger.kernel.org
      Cc: linux-kernel@vger.kernel.org
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      a2c7a983
  3. 01 May, 2018 1 commit
    • Quentin Monnet's avatar
      tools: bpftool: change time format for program 'loaded at:' information · a3fe1f6f
      Quentin Monnet authored
      To make eBPF program load time easier to parse from "bpftool prog"
      output for machines, change the time format used by the program. The
      format now differs for plain and JSON version:
      
      - Plain version uses a string formatted according to ISO 8601.
      - JSON uses the number of seconds since the Epoch, wich is less friendly
        for humans but even easier to process.
      
      Example output:
      
          # ./bpftool prog
          41298: xdp  tag a04f5eef06a7f555 dev foo
                  loaded_at 2018-04-18T17:19:47+0100  uid 0
                  xlated 16B  not jited  memlock 4096B
      
          # ./bpftool prog -p
          [{
                  "id": 41298,
                  "type": "xdp",
                  "tag": "a04f5eef06a7f555",
                  "gpl_compatible": false,
                  "dev": {
                      "ifindex": 14,
                      "ns_dev": 3,
                      "ns_inode": 4026531993,
                      "ifname": "foo"
                  },
                  "loaded_at": 1524068387,
                  "uid": 0,
                  "bytes_xlated": 16,
                  "jited": false,
                  "bytes_memlock": 4096
              }
          ]
      
      Previously, "Apr 18/17:19" would be used at both places.
      Suggested-by: default avatarAlexei Starovoitov <ast@kernel.org>
      Signed-off-by: default avatarQuentin Monnet <quentin.monnet@netronome.com>
      Acked-by: default avatarJakub Kicinski <jakub.kicinski@netronome.com>
      Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      a3fe1f6f
  4. 30 Apr, 2018 7 commits
  5. 29 Apr, 2018 15 commits
    • Teng Qin's avatar
      bpf: Allow bpf_current_task_under_cgroup in interrupt · 7ef37712
      Teng Qin authored
      Currently, the bpf_current_task_under_cgroup helper has a check where if
      the BPF program is running in_interrupt(), it will return -EINVAL. This
      prevents the helper to be used in many useful scenarios, particularly
      BPF programs attached to Perf Events.
      
      This commit removes the check. Tested a few NMI (Perf Event) and some
      softirq context, the helper returns the correct result.
      Signed-off-by: default avatarTeng Qin <qinteng@fb.com>
      Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      7ef37712
    • Alexei Starovoitov's avatar
      Merge branch 'fix-bpf-helpers-doc' · fcf85729
      Alexei Starovoitov authored
      Andrey Ignatov says:
      
      ====================
      BPF helpers documentation in UAPI refers to kernel ctx structures when it
      has to refer to user visible ones. Fix it.
      ====================
      Reviewed-by: default avatarQuentin Monnet <quentin.monnet@netronome.com>
      Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      fcf85729
    • Andrey Ignatov's avatar
      bpf: Sync bpf.h to tools/ · 96871b9f
      Andrey Ignatov authored
      The patch syncs bpf.h to tools/.
      Signed-off-by: default avatarAndrey Ignatov <rdna@fb.com>
      Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      96871b9f
    • Andrey Ignatov's avatar
      bpf: Fix helpers ctx struct types in uapi doc · a3ef8e9a
      Andrey Ignatov authored
      Helpers may operate on two types of ctx structures: user visible ones
      (e.g. `struct bpf_sock_ops`) when used in user programs, and kernel ones
      (e.g. `struct bpf_sock_ops_kern`) in kernel implementation.
      
      UAPI documentation must refer to only user visible structures.
      
      The patch replaces references to `_kern` structures in BPF helpers
      description by corresponding user visible structures.
      Signed-off-by: default avatarAndrey Ignatov <rdna@fb.com>
      Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      a3ef8e9a
    • Alexei Starovoitov's avatar
      Merge branch 'bpf_get_stack' · f60ad0a0
      Alexei Starovoitov authored
      Yonghong Song says:
      
      ====================
      Currently, stackmap and bpf_get_stackid helper are provided
      for bpf program to get the stack trace. This approach has
      a limitation though. If two stack traces have the same hash,
      only one will get stored in the stackmap table regardless of
      whether BPF_F_REUSE_STACKID is specified or not,
      so some stack traces may be missing from user perspective.
      
      This patch implements a new helper, bpf_get_stack, will
      send stack traces directly to bpf program. The bpf program
      is able to see all stack traces, and then can do in-kernel
      processing or send stack traces to user space through
      shared map or bpf_perf_event_output.
      
      Patches #1 and #2 implemented the core kernel support.
      Patch #3 removes two never-hit branches in verifier.
      Patches #4 and #5 are two verifier improves to make
      bpf programming easier. Patch #6 synced the new helper
      to tools headers. Patch #7 moved perf_event polling code
      and ksym lookup code from samples/bpf to
      tools/testing/selftests/bpf. Patch #8 added a verifier
      test in tools/bpf for new verifier change.
      Patches #9 and #10 added tests for raw tracepoint prog
      and tracepoint prog respectively.
      
      Changelogs:
        v8 -> v9:
          . make function perf_event_mmap (in trace_helpers.c) extern
            to decouple perf_event_mmap and perf_event_poller.
          . add jit enabled handling for kernel stack verification
            in Patch #9. Since we did not have a good way to
            verify jit enabled kernel stack, just return true if
            the kernel stack is not empty.
          . In path #9, using raw_syscalls/sys_enter instead of
            sched/sched_switch, removed calling cmd
            "task 1 dd if=/dev/zero of=/dev/null" which is left
            with dangling process after the program exited.
        v7 -> v8:
          . rebase on top of latest bpf-next
          . simplify BPF_ARSH dst_reg->smin_val/smax_value tracking
          . rewrite the description of bpf_get_stack() in uapi bpf.h
            based on new format.
        v6 -> v7:
          . do perf callchain buffer allocation inside the
            verifier. so if the prog->has_callchain_buf is set,
            it is guaranteed that the buffer has been allocated.
          . change condition "trace_nr <= skip" to "trace_nr < skip"
            so that for zero size buffer, return 0 instead of -EFAULT
        v5 -> v6:
          . after refining return register smax_value and umax_value
            for helpers bpf_get_stack and bpf_probe_read_str,
            bounds and var_off of the return register are further refined.
          . added missing commit message for tools header sync commit.
          . removed one unnecessary empty line.
        v4 -> v5:
          . relied on dst_reg->var_off to refine umin_val/umax_val
            in verifier handling BPF_ARSH value range tracking,
            suggested by Edward.
        v3 -> v4:
          . fixed a bug when meta ptr is set to NULL in check_func_arg.
          . introduced tnum_arshift and added detailed comments for
            the underlying implementation
          . avoided using VLA in tools/bpf test_progs.
        v2 -> v3:
          . used meta to track helper memory size argument
          . implemented range checking for ARSH in verifier
          . moved perf event polling and ksym related functions
            from samples/bpf to tools/bpf
          . added test to compare build id's between bpf_get_stackid
            and bpf_get_stack
        v1 -> v2:
          . fixed compilation error when CONFIG_PERF_EVENTS is not enabled
      ====================
      Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      f60ad0a0
    • Yonghong Song's avatar
      tools/bpf: add a test for bpf_get_stack with tracepoint prog · 79b45350
      Yonghong Song authored
      The test_stacktrace_map and test_stacktrace_build_id are
      enhanced to call bpf_get_stack in the helper to get the
      stack trace as well.  The stack traces from bpf_get_stack
      and bpf_get_stackid are compared to ensure that for the
      same stack as represented as the same hash, their ip addresses
      or build id's must be the same.
      Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
      Signed-off-by: default avatarYonghong Song <yhs@fb.com>
      Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      79b45350
    • Yonghong Song's avatar
      tools/bpf: add a test for bpf_get_stack with raw tracepoint prog · 173965fb
      Yonghong Song authored
      The test attached a raw_tracepoint program to raw_syscalls/sys_enter.
      It tested to get stack for user space, kernel space and user
      space with build_id request. It also tested to get user
      and kernel stack into the same buffer with back-to-back
      bpf_get_stack helper calls.
      
      If jit is not enabled, the user space application will check
      to ensure that the kernel function for raw_tracepoint
      ___bpf_prog_run is part of the stack.
      
      If jit is enabled, we did not have a reliable way to
      verify the kernel stack, so just assume the kernel stack
      is good when the kernel stack size is greater than 0.
      Signed-off-by: default avatarYonghong Song <yhs@fb.com>
      Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      173965fb
    • Yonghong Song's avatar
      tools/bpf: add a verifier test case for bpf_get_stack helper and ARSH · 2abe611c
      Yonghong Song authored
      The test_verifier already has a few ARSH test cases.
      This patch adds a new test case which takes advantage of newly
      improved verifier behavior for bpf_get_stack and ARSH.
      Signed-off-by: default avatarYonghong Song <yhs@fb.com>
      Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      2abe611c
    • Yonghong Song's avatar
      samples/bpf: move common-purpose trace functions to selftests · 28dbf861
      Yonghong Song authored
      There is no functionality change in this patch. The common-purpose
      trace functions, including perf_event polling and ksym lookup,
      are moved from trace_output_user.c and bpf_load.c to
      selftests/bpf/trace_helpers.c so that these function can
      be reused later in selftests.
      Acked-by: default avatarAlexei Starovoitov <ast@fb.com>
      Signed-off-by: default avatarYonghong Song <yhs@fb.com>
      Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      28dbf861
    • Yonghong Song's avatar
      tools/bpf: add bpf_get_stack helper to tools headers · de2ff05f
      Yonghong Song authored
      The tools header file bpf.h is synced with kernel uapi bpf.h.
      The new helper is also added to bpf_helpers.h.
      Signed-off-by: default avatarYonghong Song <yhs@fb.com>
      Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      de2ff05f
    • Yonghong Song's avatar
      bpf/verifier: improve register value range tracking with ARSH · 9cbe1f5a
      Yonghong Song authored
      When helpers like bpf_get_stack returns an int value
      and later on used for arithmetic computation, the LSH and ARSH
      operations are often required to get proper sign extension into
      64-bit. For example, without this patch:
          54: R0=inv(id=0,umax_value=800)
          54: (bf) r8 = r0
          55: R0=inv(id=0,umax_value=800) R8_w=inv(id=0,umax_value=800)
          55: (67) r8 <<= 32
          56: R8_w=inv(id=0,umax_value=3435973836800,var_off=(0x0; 0x3ff00000000))
          56: (c7) r8 s>>= 32
          57: R8=inv(id=0)
      With this patch:
          54: R0=inv(id=0,umax_value=800)
          54: (bf) r8 = r0
          55: R0=inv(id=0,umax_value=800) R8_w=inv(id=0,umax_value=800)
          55: (67) r8 <<= 32
          56: R8_w=inv(id=0,umax_value=3435973836800,var_off=(0x0; 0x3ff00000000))
          56: (c7) r8 s>>= 32
          57: R8=inv(id=0, umax_value=800,var_off=(0x0; 0x3ff))
      With better range of "R8", later on when "R8" is added to other register,
      e.g., a map pointer or scalar-value register, the better register
      range can be derived and verifier failure may be avoided.
      
      In our later example,
          ......
          usize = bpf_get_stack(ctx, raw_data, max_len, BPF_F_USER_STACK);
          if (usize < 0)
              return 0;
          ksize = bpf_get_stack(ctx, raw_data + usize, max_len - usize, 0);
          ......
      Without improving ARSH value range tracking, the register representing
      "max_len - usize" will have smin_value equal to S64_MIN and will be
      rejected by verifier.
      Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
      Signed-off-by: default avatarYonghong Song <yhs@fb.com>
      Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      9cbe1f5a
    • Yonghong Song's avatar
      bpf: remove never-hit branches in verifier adjust_scalar_min_max_vals · afbe1a5b
      Yonghong Song authored
      In verifier function adjust_scalar_min_max_vals,
      when src_known is false and the opcode is BPF_LSH/BPF_RSH,
      early return will happen in the function. So remove
      the branch in handling BPF_LSH/BPF_RSH when src_known is false.
      Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
      Signed-off-by: default avatarYonghong Song <yhs@fb.com>
      Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      afbe1a5b
    • Yonghong Song's avatar
      bpf/verifier: refine retval R0 state for bpf_get_stack helper · 849fa506
      Yonghong Song authored
      The special property of return values for helpers bpf_get_stack
      and bpf_probe_read_str are captured in verifier.
      Both helpers return a negative error code or
      a length, which is equal to or smaller than the buffer
      size argument. This additional information in the
      verifier can avoid the condition such as "retval > bufsize"
      in the bpf program. For example, for the code blow,
          usize = bpf_get_stack(ctx, raw_data, max_len, BPF_F_USER_STACK);
          if (usize < 0 || usize > max_len)
              return 0;
      The verifier may have the following errors:
          52: (85) call bpf_get_stack#65
           R0=map_value(id=0,off=0,ks=4,vs=1600,imm=0) R1_w=ctx(id=0,off=0,imm=0)
           R2_w=map_value(id=0,off=0,ks=4,vs=1600,imm=0) R3_w=inv800 R4_w=inv256
           R6=ctx(id=0,off=0,imm=0) R7=map_value(id=0,off=0,ks=4,vs=1600,imm=0)
           R9_w=inv800 R10=fp0,call_-1
          53: (bf) r8 = r0
          54: (bf) r1 = r8
          55: (67) r1 <<= 32
          56: (bf) r2 = r1
          57: (77) r2 >>= 32
          58: (25) if r2 > 0x31f goto pc+33
           R0=inv(id=0) R1=inv(id=0,smax_value=9223372032559808512,
                               umax_value=18446744069414584320,
                               var_off=(0x0; 0xffffffff00000000))
           R2=inv(id=0,umax_value=799,var_off=(0x0; 0x3ff))
           R6=ctx(id=0,off=0,imm=0) R7=map_value(id=0,off=0,ks=4,vs=1600,imm=0)
           R8=inv(id=0) R9=inv800 R10=fp0,call_-1
          59: (1f) r9 -= r8
          60: (c7) r1 s>>= 32
          61: (bf) r2 = r7
          62: (0f) r2 += r1
          math between map_value pointer and register with unbounded
          min value is not allowed
      The failure is due to llvm compiler optimization where register "r2",
      which is a copy of "r1", is tested for condition while later on "r1"
      is used for map_ptr operation. The verifier is not able to track such
      inst sequence effectively.
      
      Without the "usize > max_len" condition, there is no llvm optimization
      and the below generated code passed verifier:
          52: (85) call bpf_get_stack#65
           R0=map_value(id=0,off=0,ks=4,vs=1600,imm=0) R1_w=ctx(id=0,off=0,imm=0)
           R2_w=map_value(id=0,off=0,ks=4,vs=1600,imm=0) R3_w=inv800 R4_w=inv256
           R6=ctx(id=0,off=0,imm=0) R7=map_value(id=0,off=0,ks=4,vs=1600,imm=0)
           R9_w=inv800 R10=fp0,call_-1
          53: (b7) r1 = 0
          54: (bf) r8 = r0
          55: (67) r8 <<= 32
          56: (c7) r8 s>>= 32
          57: (6d) if r1 s> r8 goto pc+24
           R0=inv(id=0,umax_value=800,var_off=(0x0; 0x3ff))
           R1=inv0 R6=ctx(id=0,off=0,imm=0)
           R7=map_value(id=0,off=0,ks=4,vs=1600,imm=0)
           R8=inv(id=0,umax_value=800,var_off=(0x0; 0x3ff)) R9=inv800
           R10=fp0,call_-1
          58: (bf) r2 = r7
          59: (0f) r2 += r8
          60: (1f) r9 -= r8
          61: (bf) r1 = r6
      Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
      Signed-off-by: default avatarYonghong Song <yhs@fb.com>
      Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      849fa506
    • Yonghong Song's avatar
      bpf: add bpf_get_stack helper · c195651e
      Yonghong Song authored
      Currently, stackmap and bpf_get_stackid helper are provided
      for bpf program to get the stack trace. This approach has
      a limitation though. If two stack traces have the same hash,
      only one will get stored in the stackmap table,
      so some stack traces are missing from user perspective.
      
      This patch implements a new helper, bpf_get_stack, will
      send stack traces directly to bpf program. The bpf program
      is able to see all stack traces, and then can do in-kernel
      processing or send stack traces to user space through
      shared map or bpf_perf_event_output.
      Acked-by: default avatarAlexei Starovoitov <ast@fb.com>
      Signed-off-by: default avatarYonghong Song <yhs@fb.com>
      Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      c195651e
    • Yonghong Song's avatar
      bpf: change prototype for stack_map_get_build_id_offset · 5f412632
      Yonghong Song authored
      This patch didn't incur functionality change. The function prototype
      got changed so that the same function can be reused later.
      Signed-off-by: default avatarYonghong Song <yhs@fb.com>
      Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      5f412632
  6. 27 Apr, 2018 2 commits
    • Leo Yan's avatar
      bpf, doc: Update bpf_jit_enable limitation for CONFIG_BPF_JIT_ALWAYS_ON · 2c25fc9a
      Leo Yan authored
      When CONFIG_BPF_JIT_ALWAYS_ON is enabled, kernel has limitation for
      bpf_jit_enable, so it has fixed value 1 and we cannot set it to 2
      for JIT opcode dumping; this patch is to update the doc for it.
      Suggested-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      Signed-off-by: default avatarLeo Yan <leo.yan@linaro.org>
      Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      2c25fc9a
    • David S. Miller's avatar
      Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next · 79741a38
      David S. Miller authored
      Daniel Borkmann says:
      
      ====================
      pull-request: bpf-next 2018-04-27
      
      The following pull-request contains BPF updates for your *net-next* tree.
      
      The main changes are:
      
      1) Add extensive BPF helper description into include/uapi/linux/bpf.h
         and a new script bpf_helpers_doc.py which allows for generating a
         man page out of it. Thus, every helper in BPF now comes with proper
         function signature, detailed description and return code explanation,
         from Quentin.
      
      2) Migrate the BPF collect metadata tunnel tests from BPF samples over
         to the BPF selftests and further extend them with v6 vxlan, geneve
         and ipip tests, simplify the ipip tests, improve documentation and
         convert to bpf_ntoh*() / bpf_hton*() api, from William.
      
      3) Currently, helpers that expect ARG_PTR_TO_MAP_{KEY,VALUE} can only
         access stack and packet memory. Extend this to allow such helpers
         to also use map values, which enabled use cases where value from
         a first lookup can be directly used as a key for a second lookup,
         from Paul.
      
      4) Add a new helper bpf_skb_get_xfrm_state() for tc BPF programs in
         order to retrieve XFRM state information containing SPI, peer
         address and reqid values, from Eyal.
      
      5) Various optimizations in nfp driver's BPF JIT in order to turn ADD
         and SUB instructions with negative immediate into the opposite
         operation with a positive immediate such that nfp can better fit
         small immediates into instructions. Savings in instruction count
         up to 4% have been observed, from Jakub.
      
      6) Add the BPF prog's gpl_compatible flag to struct bpf_prog_info
         and add support for dumping this through bpftool, from Jiri.
      
      7) Move the BPF sockmap samples over into BPF selftests instead since
         sockmap was rather a series of tests than sample anyway and this way
         this can be run from automated bots, from John.
      
      8) Follow-up fix for bpf_adjust_tail() helper in order to make it work
         with generic XDP, from Nikita.
      
      9) Some follow-up cleanups to BTF, namely, removing unused defines from
         BTF uapi header and renaming 'name' struct btf_* members into name_off
         to make it more clear they are offsets into string section, from Martin.
      
      10) Remove test_sock_addr from TEST_GEN_PROGS in BPF selftests since
          not run directly but invoked from test_sock_addr.sh, from Yonghong.
      
      11) Remove redundant ret assignment in sample BPF loader, from Wang.
      
      12) Add couple of missing files to BPF selftest's gitignore, from Anders.
      
      There are two trivial merge conflicts while pulling:
      
        1) Remove samples/sockmap/Makefile since all sockmap tests have been
           moved to selftests.
        2) Add both hunks from tools/testing/selftests/bpf/.gitignore to the
           file since git should ignore all of them.
      ====================
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      79741a38
  7. 26 Apr, 2018 10 commits
    • Wang Sheng-Hui's avatar
      samples, bpf: remove redundant ret assignment in bpf_load_program() · c0885f61
      Wang Sheng-Hui authored
      2 redundant ret assignments removed:
      
      * 'ret = 1' before the logic 'if (data_maps)', and if any errors jump to
        label 'done'. No 'ret = 1' needed before the error jump.
      
      * After the '/* load programs */' part, if everything goes well, then
        the BPF code will be loaded and 'ret' set to 0 by load_and_attach().
        If something goes wrong, 'ret' set to none-O, the redundant 'ret = 0'
        after the for clause will make the error skipped.
      
        For example, if some BPF code cannot provide supported program types
        in ELF SEC("unknown"), the for clause will not call load_and_attach()
        to load the BPF code. 1 should be returned to callees instead of 0.
      Signed-off-by: default avatarWang Sheng-Hui <shhuiw@foxmail.com>
      Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      c0885f61
    • Daniel Borkmann's avatar
      Merge branch 'bpf-uapi-helper-doc' · a6712d45
      Daniel Borkmann authored
      Quentin Monnet says:
      
      ====================
      eBPF helper functions can be called from within eBPF programs to perform
      a variety of tasks that would be otherwise hard or impossible to do with
      eBPF itself. There is a growing number of such helper functions in the
      kernel, but documentation is scarce. The main user space header file
      does contain a short commented description of most helpers, but it is
      somewhat outdated and not complete. It is more a "cheat sheet" than a
      real documentation accessible to new eBPF developers.
      
      This commit attempts to improve the situation by replacing the existing
      overview for the helpers with a more developed description. Furthermore,
      a Python script is added to generate a manual page for eBPF helpers. The
      workflow is the following, and requires the rst2man utility:
      
          $ ./scripts/bpf_helpers_doc.py \
                  --filename include/uapi/linux/bpf.h > /tmp/bpf-helpers.rst
          $ rst2man /tmp/bpf-helpers.rst > /tmp/bpf-helpers.7
          $ man /tmp/bpf-helpers.7
      
      The objective is to keep all documentation related to the helpers in a
      single place, and to be able to generate from here a manual page that
      could be packaged in the man-pages repository and shipped with most
      distributions.
      
      Additionally, parsing the prototypes of the helper functions could
      hopefully be reused, with a different Printer object, to generate
      header files needed in some eBPF-related projects.
      
      Regarding the description of each helper, it comprises several items:
      
      - The function prototype.
      - A description of the function and of its arguments (except for a
        couple of cases, when there are no arguments and the return value
        makes the function usage really obvious).
      - A description of return values (if not void).
      
      Additional items such as the list of compatible eBPF program and map
      types for each helper, Linux kernel version that introduced the helper,
      GPL-only restriction, and commit hash could be added in the future, but
      it was decided on the mailing list to leave them aside for now.
      
      For several helpers, descriptions are inspired (at times, nearly copied)
      from the commit logs introducing them in the kernel--Many thanks to
      their respective authors! Some sentences were also adapted from comments
      from the reviews, thanks to the reviewers as well. Descriptions were
      completed as much as possible, the objective being to have something easily
      accessible even for people just starting with eBPF. There is probably a bit
      more work to do in this direction for some helpers.
      
      Some RST formatting is used in the descriptions (not in function
      prototypes, to keep them readable, but the Python script provided in
      order to generate the RST for the manual page does add formatting to
      prototypes, to produce something pretty) to get "bold" and "italics" in
      manual pages. Hopefully, the descriptions in bpf.h file remains
      perfectly readable. Note that the few trailing white spaces are
      intentional, removing them would break paragraphs for rst2man.
      
      The descriptions should ideally be updated each time someone adds a new
      helper, or updates the behaviour (new socket option supported, ...) or
      the interface (new flags available, ...) of existing ones.
      
      To ease the review process, the documentation has been split into several
      patches.
      
      v3 -> v4:
      - Add a patch (#9) for newly added BPF helpers.
      - Add a patch (#10) to update UAPI bpf.h version under tools/.
      - Use SPDX tag in Python script.
      - Several fixes on man page header and footer, and helpers documentation.
        Please refer to individual patches for details.
      
      RFC v2 -> PATCH v3:
      Several fixes on man page header and footer, and helpers documentation.
      Please refer to individual patches for details.
      
      RFC v1 -> RFC v2:
      - Remove "For" (compatible program and map types), "Since" (minimal
        Linux kernel version required), "GPL only" sections and commit hashes
        for the helpers.
      - Add comment on top of the description list to explain how this
        documentation is supposed to be processed.
      - Update Python script accordingly (remove the same sections, and remove
        paragraphs on program types and GPL restrictions from man page
        header).
      - Split series into several patches.
      ====================
      Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      Cc: linux-doc@vger.kernel.org
      Cc: linux-man@vger.kernel.org
      a6712d45
    • Quentin Monnet's avatar
      bpf: update bpf.h uapi header for tools · 9cde0c88
      Quentin Monnet authored
      Update tools/include/uapi/linux/bpf.h file in order to reflect the
      changes for BPF helper functions documentation introduced in previous
      commits.
      Signed-off-by: default avatarQuentin Monnet <quentin.monnet@netronome.com>
      Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      9cde0c88
    • Quentin Monnet's avatar
      bpf: add documentation for eBPF helpers (65-66) · 2d020dd7
      Quentin Monnet authored
      Add documentation for eBPF helper functions to bpf.h user header file.
      This documentation can be parsed with the Python script provided in
      another commit of the patch series, in order to provide a RST document
      that can later be converted into a man page.
      
      The objective is to make the documentation easily understandable and
      accessible to all eBPF developers, including beginners.
      
      This patch contains descriptions for the following helper functions:
      
      Helper from Nikita:
      - bpf_xdp_adjust_tail()
      
      Helper from Eyal:
      - bpf_skb_get_xfrm_state()
      
      v4:
      - New patch (helpers did not exist yet for previous versions).
      
      Cc: Nikita V. Shirokov <tehnerd@tehnerd.com>
      Cc: Eyal Birger <eyal.birger@gmail.com>
      Signed-off-by: default avatarQuentin Monnet <quentin.monnet@netronome.com>
      Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      2d020dd7
    • Quentin Monnet's avatar
      bpf: add documentation for eBPF helpers (58-64) · ab127040
      Quentin Monnet authored
      Add documentation for eBPF helper functions to bpf.h user header file.
      This documentation can be parsed with the Python script provided in
      another commit of the patch series, in order to provide a RST document
      that can later be converted into a man page.
      
      The objective is to make the documentation easily understandable and
      accessible to all eBPF developers, including beginners.
      
      This patch contains descriptions for the following helper functions, all
      written by John:
      
      - bpf_redirect_map()
      - bpf_sk_redirect_map()
      - bpf_sock_map_update()
      - bpf_msg_redirect_map()
      - bpf_msg_apply_bytes()
      - bpf_msg_cork_bytes()
      - bpf_msg_pull_data()
      
      v4:
      - bpf_redirect_map(): Fix typos: "XDP_ABORT" changed to "XDP_ABORTED",
        "his" to "this". Also add a paragraph on performance improvement over
        bpf_redirect() helper.
      
      v3:
      - bpf_sk_redirect_map(): Improve description of BPF_F_INGRESS flag.
      - bpf_msg_redirect_map(): Improve description of BPF_F_INGRESS flag.
      - bpf_redirect_map(): Fix note on CPU redirection, not fully implemented
        for generic XDP but supported on native XDP.
      - bpf_msg_pull_data(): Clarify comment about invalidated verifier
        checks.
      
      Cc: Jesper Dangaard Brouer <brouer@redhat.com>
      Cc: John Fastabend <john.fastabend@gmail.com>
      Signed-off-by: default avatarQuentin Monnet <quentin.monnet@netronome.com>
      Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      ab127040
    • Quentin Monnet's avatar
      bpf: add documentation for eBPF helpers (51-57) · 7aa79a86
      Quentin Monnet authored
      Add documentation for eBPF helper functions to bpf.h user header file.
      This documentation can be parsed with the Python script provided in
      another commit of the patch series, in order to provide a RST document
      that can later be converted into a man page.
      
      The objective is to make the documentation easily understandable and
      accessible to all eBPF developers, including beginners.
      
      This patch contains descriptions for the following helper functions:
      
      Helpers from Lawrence:
      - bpf_setsockopt()
      - bpf_getsockopt()
      - bpf_sock_ops_cb_flags_set()
      
      Helpers from Yonghong:
      - bpf_perf_event_read_value()
      - bpf_perf_prog_read_value()
      
      Helper from Josef:
      - bpf_override_return()
      
      Helper from Andrey:
      - bpf_bind()
      
      v4:
      - bpf_perf_event_read_value(): State that this helper should be
        preferred over bpf_perf_event_read().
      
      v3:
      - bpf_perf_event_read_value(): Fix time of selection for perf event type
        in description. Remove occurences of "cores" to avoid confusion with
        "CPU".
      - bpf_bind(): Remove last paragraph of description, which was off topic.
      
      Cc: Lawrence Brakmo <brakmo@fb.com>
      Cc: Yonghong Song <yhs@fb.com>
      Cc: Josef Bacik <jbacik@fb.com>
      Cc: Andrey Ignatov <rdna@fb.com>
      Signed-off-by: default avatarQuentin Monnet <quentin.monnet@netronome.com>
      Acked-by: default avatarYonghong Song <yhs@fb.com>
      [for bpf_perf_event_read_value(), bpf_perf_prog_read_value()]
      Acked-by: default avatarAndrey Ignatov <rdna@fb.com>
      [for bpf_bind()]
      Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      7aa79a86
    • Quentin Monnet's avatar
      bpf: add documentation for eBPF helpers (42-50) · c6b5fb86
      Quentin Monnet authored
      Add documentation for eBPF helper functions to bpf.h user header file.
      This documentation can be parsed with the Python script provided in
      another commit of the patch series, in order to provide a RST document
      that can later be converted into a man page.
      
      The objective is to make the documentation easily understandable and
      accessible to all eBPF developers, including beginners.
      
      This patch contains descriptions for the following helper functions:
      
      Helper from Kaixu:
      - bpf_perf_event_read()
      
      Helpers from Martin:
      - bpf_skb_under_cgroup()
      - bpf_xdp_adjust_head()
      
      Helpers from Sargun:
      - bpf_probe_write_user()
      - bpf_current_task_under_cgroup()
      
      Helper from Thomas:
      - bpf_skb_change_head()
      
      Helper from Gianluca:
      - bpf_probe_read_str()
      
      Helpers from Chenbo:
      - bpf_get_socket_cookie()
      - bpf_get_socket_uid()
      
      v4:
      - bpf_perf_event_read(): State that bpf_perf_event_read_value() should
        be preferred over this helper.
      - bpf_skb_change_head(): Clarify comment about invalidated verifier
        checks.
      - bpf_xdp_adjust_head(): Clarify comment about invalidated verifier
        checks.
      - bpf_probe_write_user(): Add that dst must be a valid user space
        address.
      - bpf_get_socket_cookie(): Improve description by making clearer that
        the cockie belongs to the socket, and state that it remains stable for
        the life of the socket.
      
      v3:
      - bpf_perf_event_read(): Fix time of selection for perf event type in
        description. Remove occurences of "cores" to avoid confusion with
        "CPU".
      
      Cc: Martin KaFai Lau <kafai@fb.com>
      Cc: Sargun Dhillon <sargun@sargun.me>
      Cc: Thomas Graf <tgraf@suug.ch>
      Cc: Gianluca Borello <g.borello@gmail.com>
      Cc: Chenbo Feng <fengc@google.com>
      Signed-off-by: default avatarQuentin Monnet <quentin.monnet@netronome.com>
      Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
      Acked-by: default avatarMartin KaFai Lau <kafai@fb.com>
      [for bpf_skb_under_cgroup(), bpf_xdp_adjust_head()]
      Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      c6b5fb86
    • Quentin Monnet's avatar
      bpf: add documentation for eBPF helpers (33-41) · fa15601a
      Quentin Monnet authored
      Add documentation for eBPF helper functions to bpf.h user header file.
      This documentation can be parsed with the Python script provided in
      another commit of the patch series, in order to provide a RST document
      that can later be converted into a man page.
      
      The objective is to make the documentation easily understandable and
      accessible to all eBPF developers, including beginners.
      
      This patch contains descriptions for the following helper functions, all
      written by Daniel:
      
      - bpf_get_hash_recalc()
      - bpf_skb_change_tail()
      - bpf_skb_pull_data()
      - bpf_csum_update()
      - bpf_set_hash_invalid()
      - bpf_get_numa_node_id()
      - bpf_set_hash()
      - bpf_skb_adjust_room()
      - bpf_xdp_adjust_meta()
      
      v4:
      - bpf_skb_change_tail(): Clarify comment about invalidated verifier
        checks.
      - bpf_skb_pull_data(): Clarify the motivation for using this helper or
        bpf_skb_load_bytes(), on non-linear buffers. Fix RST formatting for
        *skb*. Clarify comment about invalidated verifier checks.
      - bpf_csum_update(): Fix description of checksum (entire packet, not IP
        checksum). Fix a typo: "header" instead of "helper".
      - bpf_set_hash_invalid(): Mention bpf_get_hash_recalc().
      - bpf_get_numa_node_id(): State that the helper is not restricted to
        programs attached to sockets.
      - bpf_skb_adjust_room(): Clarify comment about invalidated verifier
        checks.
      - bpf_xdp_adjust_meta(): Clarify comment about invalidated verifier
        checks.
      
      Cc: Daniel Borkmann <daniel@iogearbox.net>
      Signed-off-by: default avatarQuentin Monnet <quentin.monnet@netronome.com>
      Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
      Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      fa15601a
    • Quentin Monnet's avatar
      bpf: add documentation for eBPF helpers (23-32) · 1fdd08be
      Quentin Monnet authored
      Add documentation for eBPF helper functions to bpf.h user header file.
      This documentation can be parsed with the Python script provided in
      another commit of the patch series, in order to provide a RST document
      that can later be converted into a man page.
      
      The objective is to make the documentation easily understandable and
      accessible to all eBPF developers, including beginners.
      
      This patch contains descriptions for the following helper functions, all
      written by Daniel:
      
      - bpf_get_prandom_u32()
      - bpf_get_smp_processor_id()
      - bpf_get_cgroup_classid()
      - bpf_get_route_realm()
      - bpf_skb_load_bytes()
      - bpf_csum_diff()
      - bpf_skb_get_tunnel_opt()
      - bpf_skb_set_tunnel_opt()
      - bpf_skb_change_proto()
      - bpf_skb_change_type()
      
      v4:
      - bpf_get_prandom_u32(): Warn that the prng is not cryptographically
        secure.
      - bpf_get_smp_processor_id(): Fix a typo (case).
      - bpf_get_cgroup_classid(): Clarify description. Add notes on the helper
        being limited to cgroup v1, and to egress path.
      - bpf_get_route_realm(): Add comparison with bpf_get_cgroup_classid().
        Add a note about usage with TC and advantage of clsact. Fix a typo in
        return value ("sdb" instead of "skb").
      - bpf_skb_load_bytes(): Make explicit loading large data loads it to the
        eBPF stack.
      - bpf_csum_diff(): Add a note on seed that can be cascaded. Link to
        bpf_l3|l4_csum_replace().
      - bpf_skb_get_tunnel_opt(): Add a note about usage with "collect
        metadata" mode, and example of this with Geneve.
      - bpf_skb_set_tunnel_opt(): Add a link to bpf_skb_get_tunnel_opt()
        description.
      - bpf_skb_change_proto(): Mention that the main use case is NAT64.
        Clarify comment about invalidated verifier checks.
      
      v3:
      - bpf_get_prandom_u32(): Fix helper name :(. Add description, including
        a note on the internal random state.
      - bpf_get_smp_processor_id(): Add description, including a note on the
        processor id remaining stable during program run.
      - bpf_get_cgroup_classid(): State that CONFIG_CGROUP_NET_CLASSID is
        required to use the helper. Add a reference to related documentation.
        State that placing a task in net_cls controller disables cgroup-bpf.
      - bpf_get_route_realm(): State that CONFIG_CGROUP_NET_CLASSID is
        required to use this helper.
      - bpf_skb_load_bytes(): Fix comment on current use cases for the helper.
      
      Cc: Daniel Borkmann <daniel@iogearbox.net>
      Signed-off-by: default avatarQuentin Monnet <quentin.monnet@netronome.com>
      Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
      Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      1fdd08be
    • Quentin Monnet's avatar
      bpf: add documentation for eBPF helpers (12-22) · c456dec4
      Quentin Monnet authored
      Add documentation for eBPF helper functions to bpf.h user header file.
      This documentation can be parsed with the Python script provided in
      another commit of the patch series, in order to provide a RST document
      that can later be converted into a man page.
      
      The objective is to make the documentation easily understandable and
      accessible to all eBPF developers, including beginners.
      
      This patch contains descriptions for the following helper functions, all
      written by Alexei:
      
      - bpf_get_current_pid_tgid()
      - bpf_get_current_uid_gid()
      - bpf_get_current_comm()
      - bpf_skb_vlan_push()
      - bpf_skb_vlan_pop()
      - bpf_skb_get_tunnel_key()
      - bpf_skb_set_tunnel_key()
      - bpf_redirect()
      - bpf_perf_event_output()
      - bpf_get_stackid()
      - bpf_get_current_task()
      
      v4:
      - bpf_redirect(): Fix typo: "XDP_ABORT" changed to "XDP_ABORTED". Add
        note on bpf_redirect_map() providing better performance. Replace "Save
        for" with "Except for".
      - bpf_skb_vlan_push(): Clarify comment about invalidated verifier
        checks.
      - bpf_skb_vlan_pop(): Clarify comment about invalidated verifier
        checks.
      - bpf_skb_get_tunnel_key(): Add notes on tunnel_id, "collect metadata"
        mode, and example tunneling protocols with which it can be used.
      - bpf_skb_set_tunnel_key(): Add a reference to the description of
        bpf_skb_get_tunnel_key().
      - bpf_perf_event_output(): Specify that, and for what purpose, the
        helper can be used with programs attached to TC and XDP.
      
      v3:
      - bpf_skb_get_tunnel_key(): Change and improve description and example.
      - bpf_redirect(): Improve description of BPF_F_INGRESS flag.
      - bpf_perf_event_output(): Fix first sentence of description. Delete
        wrong statement on context being evaluated as a struct pt_reg. Remove
        the long yet incomplete example.
      - bpf_get_stackid(): Add a note about PERF_MAX_STACK_DEPTH being
        configurable.
      
      Cc: Alexei Starovoitov <ast@kernel.org>
      Signed-off-by: default avatarQuentin Monnet <quentin.monnet@netronome.com>
      Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
      Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      c456dec4