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  1. 21 Dec, 2017 3 commits
    • Alexei Starovoitov's avatar
      Merge branch 'bpftool-improvements-kallsymfix' · 74661776
      Alexei Starovoitov authored 
      Daniel Borkmann says:

====================
This work adds correlation of maps and calls into the bpftool
xlated dump in order to help debugging and introspection of
loaded BPF progs. First patch makes kallsyms work on subprogs
with bpf calls, and second implements the actual correlation.
Details and example output can be found in the 2nd patch.
====================
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      74661776
    • Daniel Borkmann's avatar
      bpf: allow for correlation of maps and helpers in dump · 7105e828
      Daniel Borkmann authored 
      Currently a dump of an xlated prog (post verifier stage) doesn't
correlate used helpers as well as maps. The prog info lists
involved map ids, however there's no correlation of where in the
program they are used as of today. Likewise, bpftool does not
correlate helper calls with the target functions.

The latter can be done w/o any kernel changes through kallsyms,
and also has the advantage that this works with inlined helpers
and BPF calls.

Example, via interpreter:

  # tc filter show dev foo ingress
  filter protocol all pref 49152 bpf chain 0
  filter protocol all pref 49152 bpf chain 0 handle 0x1 foo.o:[ingress] \
                      direct-action not_in_hw id 1 tag c74773051b364165   <-- prog id:1

  * Output before patch (calls/maps remain unclear):

  # bpftool prog dump xlated id 1             <-- dump prog id:1
   0: (b7) r1 = 2
   1: (63) *(u32 *)(r10 -4) = r1
   2: (bf) r2 = r10
   3: (07) r2 += -4
   4: (18) r1 = 0xffff95c47a8d4800
   6: (85) call unknown#73040
   7: (15) if r0 == 0x0 goto pc+18
   8: (bf) r2 = r10
   9: (07) r2 += -4
  10: (bf) r1 = r0
  11: (85) call unknown#73040
  12: (15) if r0 == 0x0 goto pc+23
  [...]

  * Output after patch:

  # bpftool prog dump xlated id 1
   0: (b7) r1 = 2
   1: (63) *(u32 *)(r10 -4) = r1
   2: (bf) r2 = r10
   3: (07) r2 += -4
   4: (18) r1 = map[id:2]                     <-- map id:2
   6: (85) call bpf_map_lookup_elem#73424     <-- helper call
   7: (15) if r0 == 0x0 goto pc+18
   8: (bf) r2 = r10
   9: (07) r2 += -4
  10: (bf) r1 = r0
  11: (85) call bpf_map_lookup_elem#73424
  12: (15) if r0 == 0x0 goto pc+23
  [...]

  # bpftool map show id 2                     <-- show/dump/etc map id:2
  2: hash_of_maps  flags 0x0
        key 4B  value 4B  max_entries 3  memlock 4096B

Example, JITed, same prog:

  # tc filter show dev foo ingress
  filter protocol all pref 49152 bpf chain 0
  filter protocol all pref 49152 bpf chain 0 handle 0x1 foo.o:[ingress] \
                  direct-action not_in_hw id 3 tag c74773051b364165 jited

  # bpftool prog show id 3
  3: sched_cls  tag c74773051b364165
        loaded_at Dec 19/13:48  uid 0
        xlated 384B  jited 257B  memlock 4096B  map_ids 2

  # bpftool prog dump xlated id 3
   0: (b7) r1 = 2
   1: (63) *(u32 *)(r10 -4) = r1
   2: (bf) r2 = r10
   3: (07) r2 += -4
   4: (18) r1 = map[id:2]                      <-- map id:2
   6: (85) call __htab_map_lookup_elem#77408   <-+ inlined rewrite
   7: (15) if r0 == 0x0 goto pc+2                |
   8: (07) r0 += 56                              |
   9: (79) r0 = *(u64 *)(r0 +0)                <-+
  10: (15) if r0 == 0x0 goto pc+24
  11: (bf) r2 = r10
  12: (07) r2 += -4
  [...]

Example, same prog, but kallsyms disabled (in that case we are
also not allowed to pass any relative offsets, etc, so prog
becomes pointer sanitized on dump):

  # sysctl kernel.kptr_restrict=2
  kernel.kptr_restrict = 2

  # bpftool prog dump xlated id 3
   0: (b7) r1 = 2
   1: (63) *(u32 *)(r10 -4) = r1
   2: (bf) r2 = r10
   3: (07) r2 += -4
   4: (18) r1 = map[id:2]
   6: (85) call bpf_unspec#0
   7: (15) if r0 == 0x0 goto pc+2
  [...]

Example, BPF calls via interpreter:

  # bpftool prog dump xlated id 1
   0: (85) call pc+2#__bpf_prog_run_args32
   1: (b7) r0 = 1
   2: (95) exit
   3: (b7) r0 = 2
   4: (95) exit

Example, BPF calls via JIT:

  # sysctl net.core.bpf_jit_enable=1
  net.core.bpf_jit_enable = 1
  # sysctl net.core.bpf_jit_kallsyms=1
  net.core.bpf_jit_kallsyms = 1

  # bpftool prog dump xlated id 1
   0: (85) call pc+2#bpf_prog_3b185187f1855c4c_F
   1: (b7) r0 = 1
   2: (95) exit
   3: (b7) r0 = 2
   4: (95) exit

And finally, an example for tail calls that is now working
as well wrt correlation:

  # bpftool prog dump xlated id 2
  [...]
  10: (b7) r2 = 8
  11: (85) call bpf_trace_printk#-41312
  12: (bf) r1 = r6
  13: (18) r2 = map[id:1]
  15: (b7) r3 = 0
  16: (85) call bpf_tail_call#12
  17: (b7) r1 = 42
  18: (6b) *(u16 *)(r6 +46) = r1
  19: (b7) r0 = 0
  20: (95) exit

  # bpftool map show id 1
  1: prog_array  flags 0x0
        key 4B  value 4B  max_entries 1  memlock 4096B
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      7105e828
    • Daniel Borkmann's avatar
      bpf: fix kallsyms handling for subprogs · 4f74d809
      Daniel Borkmann authored 
      Right now kallsyms handling is not working with JITed subprogs.
The reason is that when in 1c2a088a ("bpf: x64: add JIT support
for multi-function programs") in jit_subprogs() they are passed
to bpf_prog_kallsyms_add(), then their prog type is 0, which BPF
core will think it's a cBPF program as only cBPF programs have a
0 type. Thus, they need to inherit the type from the main prog.

Once that is fixed, they are indeed added to the BPF kallsyms
infra, but their tag is 0. Therefore, since intention is to add
them as bpf_prog_F_<tag>, we need to pass them to bpf_prog_calc_tag()
first. And once this is resolved, there is a use-after-free on
prog cleanup: we remove the kallsyms entry from the main prog,
later walk all subprogs and call bpf_jit_free() on them. However,
the kallsyms linkage was never released on them. Thus, do that
for all subprogs right in __bpf_prog_put() when refcount hits 0.

Fixes: 1c2a088a ("bpf: x64: add JIT support for multi-function programs")
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      4f74d809
  3. 20 Dec, 2017 1 commit
  5. 19 Dec, 2017 6 commits
  7. 18 Dec, 2017 25 commits
  9. 17 Dec, 2017 5 commits
    • Josef Bacik's avatar
      trace: reenable preemption if we modify the ip · 46df3d20
      Josef Bacik authored 
      Things got moved around between the original bpf_override_return patches
and the final version, and now the ftrace kprobe dispatcher assumes if
you modified the ip that you also enabled preemption.  Make a comment of
this and enable preemption, this fixes the lockdep splat that happened
when using this feature.

Fixes: 9802d865 ("bpf: add a bpf_override_function helper")
Signed-off-by: default avatarJosef Bacik <jbacik@fb.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      46df3d20
    • Jakub Kicinski's avatar
      nfp: set flags in the correct member of netdev_bpf · 4a29c0db
      Jakub Kicinski authored 
      netdev_bpf.flags is the input member for installing the program.
netdev_bpf.prog_flags is the output member for querying.  Set
the correct one on query.

Fixes: 92f0292b ("net: xdp: report flags program was installed with on query")
Signed-off-by: default avatarJakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: default avatarQuentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      4a29c0db
    • Jakub Kicinski's avatar
      libbpf: fix Makefile exit code if libelf not found · 21567ede
      Jakub Kicinski authored 
      /bin/sh's exit does not recognize -1 as a number, leading to
the following error message:

/bin/sh: 1: exit: Illegal number: -1

Use 1 as the exit code.
Signed-off-by: default avatarJakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: default avatarQuentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      21567ede
    • Daniel Borkmann's avatar
      Merge branch 'bpf-to-bpf-function-calls' · ef9fde06
      Daniel Borkmann authored 
      Alexei Starovoitov says:

====================
First of all huge thank you to Daniel, John, Jakub, Edward and others who
reviewed multiple iterations of this patch set over the last many months
and to Dave and others who gave critical feedback during netconf/netdev.

The patch is solid enough and we thought through numerous corner cases,
but it's not the end. More followups with code reorg and features to follow.

TLDR: Allow arbitrary function calls from bpf function to another bpf function.

Since the beginning of bpf all bpf programs were represented as a single function
and program authors were forced to use always_inline for all functions
in their C code. That was causing llvm to unnecessary inflate the code size
and forcing developers to move code to header files with little code reuse.

With a bit of additional complexity teach verifier to recognize
arbitrary function calls from one bpf function to another as long as
all of functions are presented to the verifier as a single bpf program.
Extended program layout:
..
r1 = ..    // arg1
r2 = ..    // arg2
call pc+1  // function call pc-relative
exit
.. = r1    // access arg1
.. = r2    // access arg2
..
call pc+20 // second level of function call
...

It allows for better optimized code and finally allows to introduce
the core bpf libraries that can be reused in different projects,
since programs are no longer limited by single elf file.
With function calls bpf can be compiled into multiple .o files.

This patch is the first step. It detects programs that contain
multiple functions and checks that calls between them are valid.
It splits the sequence of bpf instructions (one program) into a set
of bpf functions that call each other. Calls to only known
functions are allowed. Since all functions are presented to
the verifier at once conceptually it is 'static linking'.

Future plans:
- introduce BPF_PROG_TYPE_LIBRARY and allow a set of bpf functions
  to be loaded into the kernel that can be later linked to other
  programs with concrete program types. Aka 'dynamic linking'.

- introduce function pointer type and indirect calls to allow
  bpf functions call other dynamically loaded bpf functions while
  the caller bpf function is already executing. Aka 'runtime linking'.
  This will be more generic and more flexible alternative
  to bpf_tail_calls.

FAQ:
Q: Interpreter and JIT changes mean that new instruction is introduced ?
A: No. The call instruction technically stays the same. Now it can call
   both kernel helpers and other bpf functions.
   Calling convention stays the same as well.
   From uapi point of view the call insn got new 'relocation' BPF_PSEUDO_CALL
   similar to BPF_PSEUDO_MAP_FD 'relocation' of bpf_ldimm64 insn.

Q: What had to change on LLVM side?
A: Trivial LLVM patch to allow calls was applied to upcoming 6.0 release:
   https://reviews.llvm.org/rL318614
   with few bugfixes as well.
   Make sure to build the latest llvm to have bpf_call support.

More details in the patches.
====================
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      ef9fde06
    • Daniel Borkmann's avatar
      selftests/bpf: additional bpf_call tests · 28ab173e
      Daniel Borkmann authored 
      Add some additional checks for few more corner cases.
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      28ab173e
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