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  1. 10 Mar, 2023 15 commits
  3. 09 Mar, 2023 13 commits
    • Lorenzo Bianconi's avatar
      selftests/bpf: Improve error logs in XDP compliance test tool · c1cd734c
      Lorenzo Bianconi authored 
      Improve some error logs reported in the XDP compliance test tool.
Signed-off-by: default avatarLorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/212fc5bd214ff706f6ef1acbe7272cf4d803ca9c.1678382940.git.lorenzo@kernel.org
      c1cd734c
    • Lorenzo Bianconi's avatar
      selftests/bpf: Use ifname instead of ifindex in XDP compliance test tool · 27a36bc3
      Lorenzo Bianconi authored 
      Rely on interface name instead of interface index in error messages or
logs from XDP compliance test tool.
Signed-off-by: default avatarLorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/7dc5a8ff56c252b1a7ae29b059d0b2b1543c8b5d.1678382940.git.lorenzo@kernel.org
      27a36bc3
    • Michael Weiß's avatar
      bpf: Fix a typo for BPF_F_ANY_ALIGNMENT in bpf.h · 5a70f4a6
      Michael Weiß authored 
      Fix s/BPF_PROF_LOAD/BPF_PROG_LOAD/ typo in the documentation comment
for BPF_F_ANY_ALIGNMENT in bpf.h.
Signed-off-by: default avatarMichael Weiß <michael.weiss@aisec.fraunhofer.de>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20230309133823.944097-1-michael.weiss@aisec.fraunhofer.de
      5a70f4a6
    • Martin KaFai Lau's avatar
      selftests/bpf: Fix flaky fib_lookup test · a6865576
      Martin KaFai Lau authored 
      There is a report that fib_lookup test is flaky when running in parallel.
A symptom of slowness or delay. An example:

Testing IPv6 stale neigh
set_lookup_params:PASS:inet_pton(IPV6_IFACE_ADDR) 0 nsec
test_fib_lookup:PASS:bpf_prog_test_run_opts 0 nsec
test_fib_lookup:FAIL:fib_lookup_ret unexpected fib_lookup_ret: actual 0 != expected 7
test_fib_lookup:FAIL:dmac not match unexpected dmac not match: actual 1 != expected 0
dmac expected 11:11:11:11:11:11 actual 00:00:00:00:00:00

[ Note that the "fib_lookup_ret unexpected fib_lookup_ret actual 0 ..."
  is reversed in terms of expected and actual value. Fixing in this
  patch also. ]

One possibility is the testing stale neigh entry was marked dead by the
gc (in neigh_periodic_work). The default gc_stale_time sysctl is 60s.
This patch increases it to 15 mins.

It also:

- fixes the reversed arg (actual vs expected) in one of the
  ASSERT_EQ test
- removes the nodad command arg when adding v4 neigh entry which
  currently has a warning.

Fixes: 168de023 ("selftests/bpf: Add bpf_fib_lookup test")
Reported-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarMartin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20230309060244.3242491-1-martin.lau@linux.dev
      a6865576
    • Alexei Starovoitov's avatar
      Merge branch 'BPF open-coded iterators' · 23e403b3
      Alexei Starovoitov authored 
      Andrii Nakryiko says:

====================

Add support for open-coded (aka inline) iterators in BPF world. This is a next
evolution of gradually allowing more powerful and less restrictive looping and
iteration capabilities to BPF programs.

We set up a framework for implementing all kinds of iterators (e.g., cgroup,
task, file, etc, iterators), but this patch set only implements numbers
iterator, which is used to implement ergonomic bpf_for() for-like construct
(see patches #4-#5). We also add bpf_for_each(), which is a generic
foreach-like construct that will work with any kind of open-coded iterator
implementation, as long as we stick with bpf_iter_<type>_{new,next,destroy}()
naming pattern (which we now enforce on the kernel side).

Patch #1 is preparatory refactoring for easier way to check for special kfunc
calls. Patch #2 is adding iterator kfunc registration and validation logic,
which is mostly independent from the rest of open-coded iterator logic, so is
separated out for easier reviewing.

The meat of verifier-side logic is in patch #3. Patch #4 implements numbers
iterator. I kept them separate to have clean reference for how to integrate
new iterator types (now even simpler to do than in v1 of this patch set).
Patch #5 adds bpf_for(), bpf_for_each(), and bpf_repeat() macros to
bpf_misc.h, and also adds yet another pyperf test variant, now with bpf_for()
loop. Patch #6 is verification tests, based on numbers iterator (as the only
available right now). Patch #7 actually tests runtime behavior of numbers
iterator.

Finally, with changes in v2, it's possible and trivial to implement custom
iterators completely in kernel modules, which we showcase and test by adding
a simple iterator returning same number a given number of times to
bpf_testmod. Patch #8 is where all this happens and is tested.

Most of the relevant details are in corresponding commit messages or code
comments.

v4->v5:
  - fixing missed inner for() in is_iter_reg_valid_uninit, and fixed return
    false (kernel test robot);
  - typo fixes and comment/commit description improvements throughout the
    patch set;
v3->v4:
  - remove unused variable from is_iter_reg_valid_init (kernel test robot);
v2->v3:
  - remove special kfunc leftovers for bpf_iter_num_{new,next,destroy};
  - add iters/testmod_seq* to DENYLIST.s390x, it doesn't support kfuncs in
    modules yet (CI);
v1->v2:
  - rebased on latest, dropping previously landed preparatory patches;
  - each iterator type now have its own `struct bpf_iter_<type>` which allows
    each iterator implementation to use exactly as much stack space as
    necessary, allowing to avoid runtime allocations (Alexei);
  - reworked how iterator kfuncs are defined, no verifier changes are required
    when adding new iterator type;
  - added bpf_testmod-based iterator implementation;
  - address the rest of feedback, comments, commit message adjustment, etc.

Cc: Tejun Heo <tj@kernel.org>
====================
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      23e403b3
    • Andrii Nakryiko's avatar
      selftests/bpf: implement and test custom testmod_seq iterator · 7e86a8c4
      Andrii Nakryiko authored 
      Implement a trivial iterator returning same specified integer value
N times as part of bpf_testmod kernel module. Add selftests to validate
everything works end to end.

We also reuse these tests as "verification-only" tests to validate that
kernel prints the state of custom kernel module-defined iterator correctly:

  fp-16=iter_testmod_seq(ref_id=1,state=drained,depth=0)

"testmod_seq" part is an iterator type, and is coming from module's BTF
data dynamically at runtime.
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230308184121.1165081-9-andrii@kernel.orgSigned-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      7e86a8c4
    • Andrii Nakryiko's avatar
      selftests/bpf: add number iterator tests · f59b1460
      Andrii Nakryiko authored 
      Add number iterator (bpf_iter_num_{new,next,destroy}()) tests,
validating the correct handling of various corner and common cases
*at runtime*.
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230308184121.1165081-8-andrii@kernel.orgSigned-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      f59b1460
    • Andrii Nakryiko's avatar
      selftests/bpf: add iterators tests · 57400dcc
      Andrii Nakryiko authored 
      Add various tests for open-coded iterators. Some of them excercise
various possible coding patterns in C, some go down to low-level
assembly for more control over various conditions, especially invalid
ones.

We also make use of bpf_for(), bpf_for_each(), bpf_repeat() macros in
some of these tests.
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230308184121.1165081-7-andrii@kernel.orgSigned-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      57400dcc
    • Andrii Nakryiko's avatar
      selftests/bpf: add bpf_for_each(), bpf_for(), and bpf_repeat() macros · 8c2b5e90
      Andrii Nakryiko authored 
      Add bpf_for_each(), bpf_for(), and bpf_repeat() macros that make writing
open-coded iterator-based loops much more convenient and natural. These
macros utilize cleanup attribute to ensure proper destruction of the
iterator and thanks to that manage to provide the ergonomics that is
very close to C language's for() construct. Typical loop would look like:

  int i;
  int arr[N];

  bpf_for(i, 0, N) {
      /* verifier will know that i >= 0 && i < N, so could be used to
       * directly access array elements with no extra checks
       */
       arr[i] = i;
  }

bpf_repeat() is very similar, but it doesn't expose iteration number and
is meant as a simple "repeat action N times" loop:

  bpf_repeat(N) { /* whatever, N times */ }

Note that `break` and `continue` statements inside the {} block work as
expected.

bpf_for_each() is a generalization over any kind of BPF open-coded
iterator allowing to use for-each-like approach instead of calling
low-level bpf_iter_<type>_{new,next,destroy}() APIs explicitly. E.g.:

  struct cgroup *cg;

  bpf_for_each(cgroup, cg, some, input, args) {
      /* do something with each cg */
  }

would call (not-yet-implemented) bpf_iter_cgroup_{new,next,destroy}()
functions to form a loop over cgroups, where `some, input, args` are
passed verbatim into constructor as

  bpf_iter_cgroup_new(&it, some, input, args).

As a first demonstration, add pyperf variant based on the bpf_for() loop.

Also clean up a few tests that either included bpf_misc.h header
unnecessarily from the user-space, which is unsupported, or included it
before any common types are defined (and thus leading to unnecessary
compilation warnings, potentially).
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230308184121.1165081-6-andrii@kernel.orgSigned-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      8c2b5e90
    • Andrii Nakryiko's avatar
      bpf: implement numbers iterator · 6018e1f4
      Andrii Nakryiko authored 
      Implement the first open-coded iterator type over a range of integers.

It's public API consists of:
  - bpf_iter_num_new() constructor, which accepts [start, end) range
    (that is, start is inclusive, end is exclusive).
  - bpf_iter_num_next() which will keep returning read-only pointer to int
    until the range is exhausted, at which point NULL will be returned.
    If bpf_iter_num_next() is kept calling after this, NULL will be
    persistently returned.
  - bpf_iter_num_destroy() destructor, which needs to be called at some
    point to clean up iterator state. BPF verifier enforces that iterator
    destructor is called at some point before BPF program exits.

Note that `start = end = X` is a valid combination to setup an empty
iterator. bpf_iter_num_new() will return 0 (success) for any such
combination.

If bpf_iter_num_new() detects invalid combination of input arguments, it
returns error, resets iterator state to, effectively, empty iterator, so
any subsequent call to bpf_iter_num_next() will keep returning NULL.

BPF verifier has no knowledge that returned integers are in the
[start, end) value range, as both `start` and `end` are not statically
known and enforced: they are runtime values.

While the implementation is pretty trivial, some care needs to be taken
to avoid overflows and underflows. Subsequent selftests will validate
correctness of [start, end) semantics, especially around extremes
(INT_MIN and INT_MAX).

Similarly to bpf_loop(), we enforce that no more than BPF_MAX_LOOPS can
be specified.

bpf_iter_num_{new,next,destroy}() is a logical evolution from bounded
BPF loops and bpf_loop() helper and is the basis for implementing
ergonomic BPF loops with no statically known or verified bounds.
Subsequent patches implement bpf_for() macro, demonstrating how this can
be wrapped into something that works and feels like a normal for() loop
in C language.
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230308184121.1165081-5-andrii@kernel.orgSigned-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      6018e1f4
    • Andrii Nakryiko's avatar
      bpf: add support for open-coded iterator loops · 06accc87
      Andrii Nakryiko authored 
      Teach verifier about the concept of the open-coded (or inline) iterators.

This patch adds generic iterator loop verification logic, new STACK_ITER
stack slot type to contain iterator state, and necessary kfunc plumbing
for iterator's constructor, destructor and next methods. Next patch
implements first specific iterator (numbers iterator for implementing
for() loop logic). Such split allows to have more focused commits for
verifier logic and separate commit that we could point later to
demonstrating  what does it take to add a new kind of iterator.

Each kind of iterator has its own associated struct bpf_iter_<type>,
where <type> denotes a specific type of iterator. struct bpf_iter_<type>
state is supposed to live on BPF program stack, so there will be no way
to change its size later on without breaking backwards compatibility, so
choose wisely! But given this struct is specific to a given <type> of
iterator, this allows a lot of flexibility: simple iterators could be
fine with just one stack slot (8 bytes), like numbers iterator in the
next patch, while some other more complicated iterators might need way
more to keep their iterator state. Either way, such design allows to
avoid runtime memory allocations, which otherwise would be necessary if
we fixed on-the-stack size and it turned out to be too small for a given
iterator implementation.

The way BPF verifier logic is implemented, there are no artificial
restrictions on a number of active iterators, it should work correctly
using multiple active iterators at the same time. This also means you
can have multiple nested iteration loops. struct bpf_iter_<type>
reference can be safely passed to subprograms as well.

General flow is easiest to demonstrate with a simple example using
number iterator implemented in next patch. Here's the simplest possible
loop:

  struct bpf_iter_num it;
  int *v;

  bpf_iter_num_new(&it, 2, 5);
  while ((v = bpf_iter_num_next(&it))) {
      bpf_printk("X = %d", *v);
  }
  bpf_iter_num_destroy(&it);

Above snippet should output "X = 2", "X = 3", "X = 4". Note that 5 is
exclusive and is not returned. This matches similar APIs (e.g., slices
in Go or Rust) that implement a range of elements, where end index is
non-inclusive.

In the above example, we see a trio of function:
  - constructor, bpf_iter_num_new(), which initializes iterator state
  (struct bpf_iter_num it) on the stack. If any of the input arguments
  are invalid, constructor should make sure to still initialize it such
  that subsequent bpf_iter_num_next() calls will return NULL. I.e., on
  error, return error and construct empty iterator.
  - next method, bpf_iter_num_next(), which accepts pointer to iterator
  state and produces an element. Next method should always return
  a pointer. The contract between BPF verifier is that next method will
  always eventually return NULL when elements are exhausted. Once NULL is
  returned, subsequent next calls should keep returning NULL. In the
  case of numbers iterator, bpf_iter_num_next() returns a pointer to an int
  (storage for this integer is inside the iterator state itself),
  which can be dereferenced after corresponding NULL check.
  - once done with the iterator, it's mandated that user cleans up its
  state with the call to destructor, bpf_iter_num_destroy() in this
  case. Destructor frees up any resources and marks stack space used by
  struct bpf_iter_num as usable for something else.

Any other iterator implementation will have to implement at least these
three methods. It is enforced that for any given type of iterator only
applicable constructor/destructor/next are callable. I.e., verifier
ensures you can't pass number iterator state into, say, cgroup
iterator's next method.

It is important to keep the naming pattern consistent to be able to
create generic macros to help with BPF iter usability. E.g., one
of the follow up patches adds generic bpf_for_each() macro to bpf_misc.h
in selftests, which allows to utilize iterator "trio" nicely without
having to code the above somewhat tedious loop explicitly every time.
This is enforced at kfunc registration point by one of the previous
patches in this series.

At the implementation level, iterator state tracking for verification
purposes is very similar to dynptr. We add STACK_ITER stack slot type,
reserve necessary number of slots, depending on
sizeof(struct bpf_iter_<type>), and keep track of necessary extra state
in the "main" slot, which is marked with non-zero ref_obj_id. Other
slots are also marked as STACK_ITER, but have zero ref_obj_id. This is
simpler than having a separate "is_first_slot" flag.

Another big distinction is that STACK_ITER is *always refcounted*, which
simplifies implementation without sacrificing usability. So no need for
extra "iter_id", no need to anticipate reuse of STACK_ITER slots for new
constructors, etc. Keeping it simple here.

As far as the verification logic goes, there are two extensive comments:
in process_iter_next_call() and iter_active_depths_differ() explaining
some important and sometimes subtle aspects. Please refer to them for
details.

But from 10,000-foot point of view, next methods are the points of
forking a verification state, which are conceptually similar to what
verifier is doing when validating conditional jump. We branch out at
a `call bpf_iter_<type>_next` instruction and simulate two outcomes:
NULL (iteration is done) and non-NULL (new element is returned). NULL is
simulated first and is supposed to reach exit without looping. After
that non-NULL case is validated and it either reaches exit (for trivial
examples with no real loop), or reaches another `call bpf_iter_<type>_next`
instruction with the state equivalent to already (partially) validated
one. State equivalency at that point means we technically are going to
be looping forever without "breaking out" out of established "state
envelope" (i.e., subsequent iterations don't add any new knowledge or
constraints to the verifier state, so running 1, 2, 10, or a million of
them doesn't matter). But taking into account the contract stating that
iterator next method *has to* return NULL eventually, we can conclude
that loop body is safe and will eventually terminate. Given we validated
logic outside of the loop (NULL case), and concluded that loop body is
safe (though potentially looping many times), verifier can claim safety
of the overall program logic.

The rest of the patch is necessary plumbing for state tracking, marking,
validation, and necessary further kfunc plumbing to allow implementing
iterator constructor, destructor, and next methods.
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230308184121.1165081-4-andrii@kernel.orgSigned-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      06accc87
    • Andrii Nakryiko's avatar
      bpf: add iterator kfuncs registration and validation logic · 215bf496
      Andrii Nakryiko authored 
      Add ability to register kfuncs that implement BPF open-coded iterator
contract and enforce naming and function proto convention. Enforcement
happens at the time of kfunc registration and significantly simplifies
the rest of iterators logic in the verifier.

More details follow in subsequent patches, but we enforce the following
conditions.

All kfuncs (constructor, next, destructor) have to be named consistenly
as bpf_iter_<type>_{new,next,destroy}(), respectively. <type> represents
iterator type, and iterator state should be represented as a matching
`struct bpf_iter_<type>` state type. Also, all iter kfuncs should have
a pointer to this `struct bpf_iter_<type>` as the very first argument.

Additionally:
  - Constructor, i.e., bpf_iter_<type>_new(), can have arbitrary extra
  number of arguments. Return type is not enforced either.
  - Next method, i.e., bpf_iter_<type>_next(), has to return a pointer
  type and should have exactly one argument: `struct bpf_iter_<type> *`
  (const/volatile/restrict and typedefs are ignored).
  - Destructor, i.e., bpf_iter_<type>_destroy(), should return void and
  should have exactly one argument, similar to the next method.
  - struct bpf_iter_<type> size is enforced to be positive and
  a multiple of 8 bytes (to fit stack slots correctly).

Such strictness and consistency allows to build generic helpers
abstracting important, but boilerplate, details to be able to use
open-coded iterators effectively and ergonomically (see bpf_for_each()
in subsequent patches). It also simplifies the verifier logic in some
places. At the same time, this doesn't hurt generality of possible
iterator implementations. Win-win.

Constructor kfunc is marked with a new KF_ITER_NEW flags, next method is
marked with KF_ITER_NEXT (and should also have KF_RET_NULL, of course),
while destructor kfunc is marked as KF_ITER_DESTROY.

Additionally, we add a trivial kfunc name validation: it should be
a valid non-NULL and non-empty string.
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230308184121.1165081-3-andrii@kernel.orgSigned-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      215bf496
    • Andrii Nakryiko's avatar
      bpf: factor out fetching basic kfunc metadata · 07236eab
      Andrii Nakryiko authored 
      Factor out logic to fetch basic kfunc metadata based on struct bpf_insn.
This is not exactly short or trivial code to just copy/paste and this
information is sometimes necessary in other parts of the verifier logic.
Subsequent patches will rely on this to determine if an instruction is
a kfunc call to iterator next method.

No functional changes intended, including that verbose() warning
behavior when kfunc is not allowed for a particular program type.
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230308184121.1165081-2-andrii@kernel.orgSigned-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      07236eab
  5. 08 Mar, 2023 12 commits
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