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  1. 18 Dec, 2017 24 commits
  3. 17 Dec, 2017 16 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
    • Alexei Starovoitov's avatar
      bpf: arm64: add JIT support for multi-function programs · db496944
      Alexei Starovoitov authored 
      similar to x64 add support for bpf-to-bpf calls.
When program has calls to in-kernel helpers the target call offset
is known at JIT time and arm64 architecture needs 2 passes.
With bpf-to-bpf calls the dynamically allocated function start
is unknown until all functions of the program are JITed.
Therefore (just like x64) arm64 JIT needs one extra pass over
the program to emit correct call offsets.

Implementation detail:
Avoid being too clever in 64-bit immediate moves and
always use 4 instructions (instead of 3-4 depending on the address)
to make sure only one extra pass is needed.
If some future optimization would make it worth while to optimize
'call 64-bit imm' further, the JIT would need to do 4 passes
over the program instead of 3 as in this patch.
For typical bpf program address the mov needs 3 or 4 insns,
so unconditional 4 insns to save extra pass is a worthy trade off
at this state of JIT.
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      db496944
    • Alexei Starovoitov's avatar
      bpf: x64: add JIT support for multi-function programs · 1c2a088a
      Alexei Starovoitov authored 
      Typical JIT does several passes over bpf instructions to
compute total size and relative offsets of jumps and calls.
With multitple bpf functions calling each other all relative calls
will have invalid offsets intially therefore we need to additional
last pass over the program to emit calls with correct offsets.
For example in case of three bpf functions:
main:
  call foo
  call bpf_map_lookup
  exit
foo:
  call bar
  exit
bar:
  exit

We will call bpf_int_jit_compile() indepedently for main(), foo() and bar()
x64 JIT typically does 4-5 passes to converge.
After these initial passes the image for these 3 functions
will be good except call targets, since start addresses of
foo() and bar() are unknown when we were JITing main()
(note that call bpf_map_lookup will be resolved properly
during initial passes).
Once start addresses of 3 functions are known we patch
call_insn->imm to point to right functions and call
bpf_int_jit_compile() again which needs only one pass.
Additional safety checks are done to make sure this
last pass doesn't produce image that is larger or smaller
than previous pass.

When constant blinding is on it's applied to all functions
at the first pass, since doing it once again at the last
pass can change size of the JITed code.

Tested on x64 and arm64 hw with JIT on/off, blinding on/off.
x64 jits bpf-to-bpf calls correctly while arm64 falls back to interpreter.
All other JITs that support normal BPF_CALL will behave the same way
since bpf-to-bpf call is equivalent to bpf-to-kernel call from
JITs point of view.
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      1c2a088a
    • Alexei Starovoitov's avatar
      bpf: fix net.core.bpf_jit_enable race · 60b58afc
      Alexei Starovoitov authored 
      global bpf_jit_enable variable is tested multiple times in JITs,
blinding and verifier core. The malicious root can try to toggle
it while loading the programs. This race condition was accounted
for and there should be no issues, but it's safer to avoid
this race condition.
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      60b58afc
    • Alexei Starovoitov's avatar
      bpf: add support for bpf_call to interpreter · 1ea47e01
      Alexei Starovoitov authored 
      though bpf_call is still the same call instruction and
calling convention 'bpf to bpf' and 'bpf to helper' is the same
the interpreter has to oparate on 'struct bpf_insn *'.
To distinguish these two cases add a kernel internal opcode and
mark call insns with it.
This opcode is seen by interpreter only. JITs will never see it.
Also add tiny bit of debug code to aid interpreter debugging.
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      1ea47e01
    • Alexei Starovoitov's avatar
      selftests/bpf: add xdp noinline test · b0b04fc4
      Alexei Starovoitov authored 
      add large semi-artificial XDP test with 18 functions to stress test
bpf call verification logic
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      b0b04fc4
    • Alexei Starovoitov's avatar
      selftests/bpf: add bpf_call test · 3bc35c63
      Alexei Starovoitov authored 
      strip always_inline from test_l4lb.c and compile it with -fno-inline
to let verifier go through 11 function with various function arguments
and return values
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      3bc35c63
    • Alexei Starovoitov's avatar
      libbpf: add support for bpf_call · 48cca7e4
      Alexei Starovoitov authored 
      - recognize relocation emitted by llvm
- since all regular function will be kept in .text section and llvm
  takes care of pc-relative offsets in bpf_call instruction
  simply copy all of .text to relevant program section while adjusting
  bpf_call instructions in program section to point to newly copied
  body of instructions from .text
- do so for all programs in the elf file
- set all programs types to the one passed to bpf_prog_load()

Note for elf files with multiple programs that use different
functions in .text section we need to do 'linker' style logic.
This work is still TBD
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      48cca7e4
    • Alexei Starovoitov's avatar
      selftests/bpf: add tests for stack_zero tracking · d98588ce
      Alexei Starovoitov authored 
      adjust two tests, since verifier got smarter
and add new one to test stack_zero logic
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      d98588ce
    • Alexei Starovoitov's avatar
      bpf: teach verifier to recognize zero initialized stack · cc2b14d5
      Alexei Starovoitov authored 
      programs with function calls are often passing various
pointers via stack. When all calls are inlined llvm
flattens stack accesses and optimizes away extra branches.
When functions are not inlined it becomes the job of
the verifier to recognize zero initialized stack to avoid
exploring paths that program will not take.
The following program would fail otherwise:

ptr = &buffer_on_stack;
*ptr = 0;
...
func_call(.., ptr, ...) {
  if (..)
    *ptr = bpf_map_lookup();
}
...
if (*ptr != 0) {
  // Access (*ptr)->field is valid.
  // Without stack_zero tracking such (*ptr)->field access
  // will be rejected
}

since stack slots are no longer uniform invalid | spill | misc
add liveness marking to all slots, but do it in 8 byte chunks.
So if nothing was read or written in [fp-16, fp-9] range
it will be marked as LIVE_NONE.
If any byte in that range was read, it will be marked LIVE_READ
and stacksafe() check will perform byte-by-byte verification.
If all bytes in the range were written the slot will be
marked as LIVE_WRITTEN.
This significantly speeds up state equality comparison
and reduces total number of states processed.

                    before   after
bpf_lb-DLB_L3.o       2051    2003
bpf_lb-DLB_L4.o       3287    3164
bpf_lb-DUNKNOWN.o     1080    1080
bpf_lxc-DDROP_ALL.o   24980   12361
bpf_lxc-DUNKNOWN.o    34308   16605
bpf_netdev.o          15404   10962
bpf_overlay.o         7191    6679
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      cc2b14d5
    • Alexei Starovoitov's avatar
      selftests/bpf: add verifier tests for bpf_call · a7ff3eca
      Alexei Starovoitov authored 
      Add extensive set of tests for bpf_call verification logic:

calls: basic sanity
calls: using r0 returned by callee
calls: callee is using r1
calls: callee using args1
calls: callee using wrong args2
calls: callee using two args
calls: callee changing pkt pointers
calls: two calls with args
calls: two calls with bad jump
calls: recursive call. test1
calls: recursive call. test2
calls: unreachable code
calls: invalid call
calls: jumping across function bodies. test1
calls: jumping across function bodies. test2
calls: call without exit
calls: call into middle of ld_imm64
calls: call into middle of other call
calls: two calls with bad fallthrough
calls: two calls with stack read
calls: two calls with stack write
calls: spill into caller stack frame
calls: two calls with stack write and void return
calls: ambiguous return value
calls: two calls that return map_value
calls: two calls that return map_value with bool condition
calls: two calls that return map_value with incorrect bool check
calls: two calls that receive map_value via arg=ptr_stack_of_caller. test1
calls: two calls that receive map_value via arg=ptr_stack_of_caller. test2
calls: two jumps that receive map_value via arg=ptr_stack_of_jumper. test3
calls: two calls that receive map_value_ptr_or_null via arg. test1
calls: two calls that receive map_value_ptr_or_null via arg. test2
calls: pkt_ptr spill into caller stack
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      a7ff3eca
    • Alexei Starovoitov's avatar
      bpf: introduce function calls (verification) · f4d7e40a
      Alexei Starovoitov authored 
      Allow arbitrary function calls from bpf function to another bpf function.

To recognize such set of bpf functions the verifier does:
1. runs control flow analysis to detect function boundaries
2. proceeds with verification of all functions starting from main(root) function
It recognizes that the stack of the caller can be accessed by the callee
(if the caller passed a pointer to its stack to the callee) and the callee
can store map_value and other pointers into the stack of the caller.
3. keeps track of the stack_depth of each function to make sure that total
stack depth is still less than 512 bytes
4. disallows pointers to the callee stack to be stored into the caller stack,
since they will be invalid as soon as the callee returns
5. to reuse all of the existing state_pruning logic each function call
is considered to be independent call from the verifier point of view.
The verifier pretends to inline all function calls it sees are being called.
It stores the callsite instruction index as part of the state to make sure
that two calls to the same callee from two different places in the caller
will be different from state pruning point of view
6. more safety checks are added to liveness analysis

Implementation details:
. struct bpf_verifier_state is now consists of all stack frames that
  led to this function
. struct bpf_func_state represent one stack frame. It consists of
  registers in the given frame and its stack
. propagate_liveness() logic had a premature optimization where
  mark_reg_read() and mark_stack_slot_read() were manually inlined
  with loop iterating over parents for each register or stack slot.
  Undo this optimization to reuse more complex mark_*_read() logic
. skip_callee() logic is not necessary from safety point of view,
  but without it mark_*_read() markings become too conservative,
  since after returning from the funciton call a read of r6-r9
  will incorrectly propagate the read marks into callee causing
  inefficient pruning later
. mark_*_read() logic is now aware of control flow which makes it
  more complex. In the future the plan is to rewrite liveness
  to be hierarchical. So that liveness can be done within
  basic block only and control flow will be responsible for
  propagation of liveness information along cfg and between calls.
. tail_calls and ld_abs insns are not allowed in the programs with
  bpf-to-bpf calls
. returning stack pointers to the caller or storing them into stack
  frame of the caller is not allowed

Testing:
. no difference in cilium processed_insn numbers
. large number of tests follows in next patches
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      f4d7e40a
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