This is a sample application for AF_XDP sockets. The application
supports three different modes of operation: rxdrop, txonly and l2fwd.

To show-case a simple round-robin load-balancing between a set of
sockets in an xskmap, set the RR_LB compile time define option to 1 in
"xdpsock.h".

v2: The entries variable was calculated twice in {umem,xq}_nb_avail.
Co-authored-by: NBjörn Töpel <bjorn.topel@intel.com>
Signed-off-by: NBjörn Töpel <bjorn.topel@intel.com>
Signed-off-by: NMagnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

In this commit, a new getsockopt is added: XDP_STATISTICS. This is
used to obtain stats from the sockets.

v2: getsockopt now returns size of stats structure.
Signed-off-by: NMagnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

Here, Tx support is added. The user fills the Tx queue with frames to
be sent by the kernel, and let's the kernel know using the sendmsg
syscall.
Signed-off-by: NMagnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

The new dev_direct_xmit will be used by AF_XDP in later commits.
Signed-off-by: NMagnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

Another setsockopt (XDP_TX_QUEUE) is added to let the process allocate
a queue, where the user process can pass frames to be transmitted by
the kernel.

The mmapping of the queue is done using the XDP_PGOFF_TX_QUEUE offset.
Signed-off-by: NMagnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

Here, we add another setsockopt for registered user memory (umem)
called XDP_UMEM_COMPLETION_QUEUE. Using this socket option, the
process can ask the kernel to allocate a queue (ring buffer) and also
mmap it (XDP_UMEM_PGOFF_COMPLETION_QUEUE) into the process.

The queue is used to explicitly pass ownership of umem frames from the
kernel to user process. This will be used by the TX path to tell user
space that a certain frame has been transmitted and user space can use
it for something else, if it wishes.
Signed-off-by: NMagnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

This commit wires up the xskmap to XDP_SKB layer.
Signed-off-by: NBjörn Töpel <bjorn.topel@intel.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

This commit wires up the xskmap to XDP_DRV layer.
Signed-off-by: NBjörn Töpel <bjorn.topel@intel.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

The xskmap is yet another BPF map, very much inspired by
dev/cpu/sockmap, and is a holder of AF_XDP sockets. A user application
adds AF_XDP sockets into the map, and by using the bpf_redirect_map
helper, an XDP program can redirect XDP frames to an AF_XDP socket.

Note that a socket that is bound to certain ifindex/queue index will
*only* accept XDP frames from that netdev/queue index. If an XDP
program tries to redirect from a netdev/queue index other than what
the socket is bound to, the frame will not be received on the socket.

A socket can reside in multiple maps.

v3: Fixed race and simplified code.
v2: Removed one indirection in map lookup.
Signed-off-by: NBjörn Töpel <bjorn.topel@intel.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

Here the actual receive functions of AF_XDP are implemented, that in a
later commit, will be called from the XDP layers.

There's one set of functions for the XDP_DRV side and another for
XDP_SKB (generic).

A new XDP API, xdp_return_buff, is also introduced.

Adding xdp_return_buff, which is analogous to xdp_return_frame, but
acts upon an struct xdp_buff. The API will be used by AF_XDP in future
commits.

Support for the poll syscall is also implemented.

v2: xskq_validate_id did not update cons_tail.
    The entries variable was calculated twice in xskq_nb_avail.
    Squashed xdp_return_buff commit.
Signed-off-by: NBjörn Töpel <bjorn.topel@intel.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

Here, the bind syscall is added. Binding an AF_XDP socket, means
associating the socket to an umem, a netdev and a queue index. This
can be done in two ways.

The first way, creating a "socket from scratch". Create the umem using
the XDP_UMEM_REG setsockopt and an associated fill queue with
XDP_UMEM_FILL_QUEUE. Create the Rx queue using the XDP_RX_QUEUE
setsockopt. Call bind passing ifindex and queue index ("channel" in
ethtool speak).

The second way to bind a socket, is simply skipping the
umem/netdev/queue index, and passing another already setup AF_XDP
socket. The new socket will then have the same umem/netdev/queue index
as the parent so it will share the same umem. You must also set the
flags field in the socket address to XDP_SHARED_UMEM.

v2: Use PTR_ERR instead of passing error variable explicitly.
Signed-off-by: NMagnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

Another setsockopt (XDP_RX_QUEUE) is added to let the process allocate
a queue, where the kernel can pass completed Rx frames from the kernel
to user process.

The mmapping of the queue is done using the XDP_PGOFF_RX_QUEUE offset.
Signed-off-by: NBjörn Töpel <bjorn.topel@intel.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

Here, we add another setsockopt for registered user memory (umem)
called XDP_UMEM_FILL_QUEUE. Using this socket option, the process can
ask the kernel to allocate a queue (ring buffer) and also mmap it
(XDP_UMEM_PGOFF_FILL_QUEUE) into the process.

The queue is used to explicitly pass ownership of umem frames from the
user process to the kernel. These frames will in a later patch be
filled in with Rx packet data by the kernel.

v2: Fixed potential crash in xsk_mmap.
Signed-off-by: NMagnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

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: NMagnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: NMagnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: NBjörn Töpel <bjorn.topel@intel.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

Buildable skeleton of AF_XDP without any functionality. Just what it
takes to register a new address family.
Signed-off-by: NBjörn Töpel <bjorn.topel@intel.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

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: NWang YanQing <udknight@gmail.com>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>

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: NQuentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>

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: NThomas 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: NIngo Molnar <mingo@kernel.org>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>

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: NAlexei Starovoitov <ast@kernel.org>
Signed-off-by: NQuentin Monnet <quentin.monnet@netronome.com>
Acked-by: NJakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

Bring the erspan uapi header file so BPF tunnel helpers can use it.

Fixes: 933a741e ("selftests/bpf: bpf tunnel test.")
Reported-by: NYonghong Song <yhs@fb.com>
Signed-off-by: NWilliam Tu <u9012063@gmail.com>
Acked-by: NYonghong Song <yhs@fb.com>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>

Quentin Monnet says:

====================
Here is a follow-up set for eBPF helper documentation, with two patches
to fix formatting issues:

- One to fix an error I introduced with the initial set for the doc.
- One for the newly added bpf_get_stack(), that is currently not parsed
  correctly with the Python script (function signature is fine, but
  description and return value appear as empty).

There is no change to text contents in this set.
====================
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>

Bring fixes for eBPF helper documentation formatting to bpf.h under
tools/ as well.
Signed-off-by: NQuentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>

Fix formatting (indent) for bpf_get_stack() helper documentation, so
that the doc is rendered correctly with the Python script.

Fixes: c195651e ("bpf: add bpf_get_stack helper")
Cc: Yonghong Song <yhs@fb.com>
Signed-off-by: NQuentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>

Some edits brought to the last iteration of BPF helper functions
documentation introduced an error with RST formatting. As a result, most
of one paragraph is rendered in bold text when only the name of a helper
should be. Fix it, and fix formatting of another function name in the
same paragraph.

Fixes: c6b5fb86 ("bpf: add documentation for eBPF helpers (42-50)")
Signed-off-by: NQuentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>

tracepoints to bpf core were added as a way to provide introspection
to bpf programs and maps, but after some time it became clear that
this approach is inadequate, so prog_id, map_id and corresponding
get_next_id, get_fd_by_id, get_info_by_fd, prog_query APIs were
introduced and fully adopted by bpftool and other applications.
The tracepoints in bpf core started to rot and causing syzbot warnings:
WARNING: CPU: 0 PID: 3008 at kernel/trace/trace_event_perf.c:274
Kernel panic - not syncing: panic_on_warn set ...
perf_trace_bpf_map_keyval+0x260/0xbd0 include/trace/events/bpf.h:228
trace_bpf_map_update_elem include/trace/events/bpf.h:274 [inline]
map_update_elem kernel/bpf/syscall.c:597 [inline]
SYSC_bpf kernel/bpf/syscall.c:1478 [inline]
Hence this patch deletes tracepoints in bpf core.
Reported-by: NEric Biggers <ebiggers3@gmail.com>
Reported-by: Nsyzbot <bot+a9dbb3c3e64b62536a4bc5ee7bbd4ca627566188@syzkaller.appspotmail.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Acked-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>

Commit d5a00528 ("syscalls/core, syscalls/x86: Rename
struct pt_regs-based sys_*() to __x64_sys_*()") renamed a lot
of syscall function sys_*() to __x64_sys_*().
This caused several kprobe based samples/bpf tests failing.

This patch fixed the problem in bpf_load.c.
For x86_64 architecture, function name __x64_sys_*() will be
first used for kprobe event creation. If the creation is successful,
it will be used. Otherwise, function name sys_*() will be used
for kprobe event creation.

Fixes: d5a00528 ("syscalls/core, syscalls/x86: Rename struct pt_regs-based sys_*() to __x64_sys_*()")
Signed-off-by: NYonghong Song <yhs@fb.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

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: NTeng Qin <qinteng@fb.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

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: NQuentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

The patch syncs bpf.h to tools/.
Signed-off-by: NAndrey Ignatov <rdna@fb.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

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: NAndrey Ignatov <rdna@fb.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

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: NAlexei Starovoitov <ast@kernel.org>

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: NAlexei Starovoitov <ast@kernel.org>
Signed-off-by: NYonghong Song <yhs@fb.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

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: NYonghong Song <yhs@fb.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

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: NYonghong Song <yhs@fb.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

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: NAlexei Starovoitov <ast@fb.com>
Signed-off-by: NYonghong Song <yhs@fb.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

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: NYonghong Song <yhs@fb.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

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: NAlexei Starovoitov <ast@kernel.org>
Signed-off-by: NYonghong Song <yhs@fb.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

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: NAlexei Starovoitov <ast@kernel.org>
Signed-off-by: NYonghong Song <yhs@fb.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

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: NAlexei Starovoitov <ast@kernel.org>
Signed-off-by: NYonghong Song <yhs@fb.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

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: NAlexei Starovoitov <ast@fb.com>
Signed-off-by: NYonghong Song <yhs@fb.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>