linux-stable.git/kernel/bpf/bpf_iter.c, branch linux-6.16.y

bpf: Make every prog keep a copy of ctx_arg_info

2025-02-18T02:47:27+00:00

Currently, ctx_arg_info is read-only in the view of the verifier since
it is shared among programs of the same attach type. Make each program
have their own copy of ctx_arg_info so that we can use it to store
program specific information.

In the next patch where we support acquiring a referenced kptr through a
struct_ops argument tagged with "__ref", ctx_arg_info->ref_obj_id will
be used to store the unique reference object id of the argument. This
avoids creating a requirement in the verifier that "__ref" tagged
arguments must be the first set of references acquired [0].

[0] https://lore.kernel.org/bpf/20241220195619.2022866-2-amery.hung@gmail.com/

Signed-off-by: Amery Hung 
Acked-by: Eduard Zingerman 
Acked-by: Martin KaFai Lau 
Link: https://lore.kernel.org/r/20250217190640.1748177-2-ameryhung@gmail.com
Signed-off-by: Alexei Starovoitov

[tree-wide] finally take no_llseek out

2024-09-27T15:18:43+00:00

no_llseek had been defined to NULL two years ago, in commit 868941b14441
("fs: remove no_llseek")

To quote that commit,

  At -rc1 we'll need do a mechanical removal of no_llseek -

  git grep -l -w no_llseek | grep -v porting.rst | while read i; do
	sed -i '/\/d' $i
  done

  would do it.

Unfortunately, that hadn't been done.  Linus, could you do that now, so
that we could finally put that thing to rest? All instances are of the
form
	.llseek = no_llseek,
so it's obviously safe.

Signed-off-by: Al Viro 
Signed-off-by: Linus Torvalds

bpf: move sleepable flag from bpf_prog_aux to bpf_prog

2024-03-11T23:41:25+00:00

prog->aux->sleepable is checked very frequently as part of (some) BPF
program run hot paths. So this extra aux indirection seems wasteful and
on busy systems might cause unnecessary memory cache misses.

Let's move sleepable flag into prog itself to eliminate unnecessary
pointer dereference.

Signed-off-by: Andrii Nakryiko 
Acked-by: Jiri Olsa 
Message-ID: <20240309004739.2961431-1-andrii@kernel.org>
Signed-off-by: Alexei Starovoitov

bpf: Add __bpf_kfunc_{start,end}_defs macros

2023-11-02T05:33:53+00:00

BPF kfuncs are meant to be called from BPF programs. Accordingly, most
kfuncs are not called from anywhere in the kernel, which the
-Wmissing-prototypes warning is unhappy about. We've peppered
__diag_ignore_all("-Wmissing-prototypes", ... everywhere kfuncs are
defined in the codebase to suppress this warning.

This patch adds two macros meant to bound one or many kfunc definitions.
All existing kfunc definitions which use these __diag calls to suppress
-Wmissing-prototypes are migrated to use the newly-introduced macros.
A new __diag_ignore_all - for "-Wmissing-declarations" - is added to the
__bpf_kfunc_start_defs macro based on feedback from Andrii on an earlier
version of this patch [0] and another recent mailing list thread [1].

In the future we might need to ignore different warnings or do other
kfunc-specific things. This change will make it easier to make such
modifications for all kfunc defs.

  [0]: https://lore.kernel.org/bpf/CAEf4BzaE5dRWtK6RPLnjTW-MW9sx9K3Fn6uwqCTChK2Dcb1Xig@mail.gmail.com/
  [1]: https://lore.kernel.org/bpf/ZT+2qCc%2FaXep0%2FLf@krava/

Signed-off-by: Dave Marchevsky 
Suggested-by: Andrii Nakryiko 
Acked-by: Andrii Nakryiko 
Cc: Jiri Olsa 
Acked-by: Jiri Olsa 
Acked-by: David Vernet 
Acked-by: Yafang Shao 
Link: https://lore.kernel.org/r/20231031215625.2343848-1-davemarchevsky@fb.com
Signed-off-by: Alexei Starovoitov

bpf: Don't explicitly emit BTF for struct btf_iter_num

2023-10-13T22:48:58+00:00

Commit 6018e1f407cc ("bpf: implement numbers iterator") added the
BTF_TYPE_EMIT line that this patch is modifying. The struct btf_iter_num
doesn't exist, so only a forward declaration is emitted in BTF:

  FWD 'btf_iter_num' fwd_kind=struct

That commit was probably hoping to ensure that struct bpf_iter_num is
emitted in vmlinux BTF. A previous version of this patch changed the
line to emit the correct type, but Yonghong confirmed that it would
definitely be emitted regardless in [0], so this patch simply removes
the line.

This isn't marked "Fixes" because the extraneous btf_iter_num FWD wasn't
causing any issues that I noticed, aside from mild confusion when I
looked through the code.

  [0]: https://lore.kernel.org/bpf/25d08207-43e6-36a8-5e0f-47a913d4cda5@linux.dev/

Signed-off-by: Dave Marchevsky 
Signed-off-by: Andrii Nakryiko 
Acked-by: Yonghong Song 
Acked-by: Andrii Nakryiko 
Link: https://lore.kernel.org/bpf/20231013204426.1074286-2-davemarchevsky@fb.com

bpf: implement numbers iterator

2023-03-09T00:19:51+00:00

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: Andrii Nakryiko 
Link: https://lore.kernel.org/r/20230308184121.1165081-5-andrii@kernel.org
Signed-off-by: Alexei Starovoitov

bpf: Initialize the bpf_run_ctx in bpf_iter_run_prog()

2022-08-19T00:06:13+00:00

The bpf-iter-prog for tcp and unix sk can do bpf_setsockopt()
which needs has_current_bpf_ctx() to decide if it is called by a
bpf prog.  This patch initializes the bpf_run_ctx in
bpf_iter_run_prog() for the has_current_bpf_ctx() to use.

Acked-by: Andrii Nakryiko 
Reviewed-by: Stanislav Fomichev 
Signed-off-by: Martin KaFai Lau 
Link: https://lore.kernel.org/r/20220817061751.4177657-1-kafai@fb.com
Signed-off-by: Alexei Starovoitov

Merge https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next

2022-08-18T03:29:36+00:00

Andrii Nakryiko says:

====================
bpf-next 2022-08-17

We've added 45 non-merge commits during the last 14 day(s) which contain
a total of 61 files changed, 986 insertions(+), 372 deletions(-).

The main changes are:

1) New bpf_ktime_get_tai_ns() BPF helper to access CLOCK_TAI, from Kurt
   Kanzenbach and Jesper Dangaard Brouer.

2) Few clean ups and improvements for libbpf 1.0, from Andrii Nakryiko.

3) Expose crash_kexec() as kfunc for BPF programs, from Artem Savkov.

4) Add ability to define sleepable-only kfuncs, from Benjamin Tissoires.

5) Teach libbpf's bpf_prog_load() and bpf_map_create() to gracefully handle
   unsupported names on old kernels, from Hangbin Liu.

6) Allow opting out from auto-attaching BPF programs by libbpf's BPF skeleton,
   from Hao Luo.

7) Relax libbpf's requirement for shared libs to be marked executable, from
   Henqgi Chen.

8) Improve bpf_iter internals handling of error returns, from Hao Luo.

9) Few accommodations in libbpf to support GCC-BPF quirks, from James Hilliard.

10) Fix BPF verifier logic around tracking dynptr ref_obj_id, from Joanne Koong.

11) bpftool improvements to handle full BPF program names better, from Manu
    Bretelle.

12) bpftool fixes around libcap use, from Quentin Monnet.

13) BPF map internals clean ups and improvements around memory allocations,
    from Yafang Shao.

14) Allow to use cgroup_get_from_file() on cgroupv1, allowing BPF cgroup
    iterator to work on cgroupv1, from Yosry Ahmed.

15) BPF verifier internal clean ups, from Dave Marchevsky and Joanne Koong.

16) Various fixes and clean ups for selftests/bpf and vmtest.sh, from Daniel
    Xu, Artem Savkov, Joanne Koong, Andrii Nakryiko, Shibin Koikkara Reeny.

* https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next: (45 commits)
  selftests/bpf: Few fixes for selftests/bpf built in release mode
  libbpf: Clean up deprecated and legacy aliases
  libbpf: Streamline bpf_attr and perf_event_attr initialization
  libbpf: Fix potential NULL dereference when parsing ELF
  selftests/bpf: Tests libbpf autoattach APIs
  libbpf: Allows disabling auto attach
  selftests/bpf: Fix attach point for non-x86 arches in test_progs/lsm
  libbpf: Making bpf_prog_load() ignore name if kernel doesn't support
  selftests/bpf: Update CI kconfig
  selftests/bpf: Add connmark read test
  selftests/bpf: Add existing connection bpf_*_ct_lookup() test
  bpftool: Clear errno after libcap's checks
  bpf: Clear up confusion in bpf_skb_adjust_room()'s documentation
  bpftool: Fix a typo in a comment
  libbpf: Add names for auxiliary maps
  bpf: Use bpf_map_area_alloc consistently on bpf map creation
  bpf: Make __GFP_NOWARN consistent in bpf map creation
  bpf: Use bpf_map_area_free instread of kvfree
  bpf: Remove unneeded memset in queue_stack_map creation
  libbpf: preserve errno across pr_warn/pr_info/pr_debug
  ...
====================

Link: https://lore.kernel.org/r/20220817215656.1180215-1-andrii@kernel.org
Signed-off-by: Jakub Kicinski

bpf: Only allow sleepable program for resched-able iterator

2022-08-10T17:12:48+00:00

When a sleepable program is attached to a hash map iterator, might_fault()
will report "BUG: sleeping function called from invalid context..." if
CONFIG_DEBUG_ATOMIC_SLEEP is enabled. The reason is that rcu_read_lock()
is held in bpf_hash_map_seq_next() and won't be released until all elements
are traversed or bpf_hash_map_seq_stop() is called.

Fixing it by reusing BPF_ITER_RESCHED to indicate that only non-sleepable
program is allowed for iterator without BPF_ITER_RESCHED. We can revise
bpf_iter_link_attach() later if there are other conditions which may
cause rcu_read_lock() or spin_lock() issues.

Signed-off-by: Hou Tao 
Acked-by: Yonghong Song 
Link: https://lore.kernel.org/r/20220810080538.1845898-7-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov

bpf, iter: Fix the condition on p when calling stop.

2022-08-09T16:12:00+00:00

In bpf_seq_read, seq->op->next() could return an ERR and jump to
the label stop. However, the existing code in stop does not handle
the case when p (returned from next()) is an ERR. Adds the handling
of ERR of p by converting p into an error and jumping to done.

Because all the current implementations do not have a case that
returns ERR from next(), so this patch doesn't have behavior changes
right now.

Acked-by: Yonghong Song 
Signed-off-by: Hao Luo 
Link: https://lore.kernel.org/r/20220805214821.1058337-4-haoluo@google.com
Signed-off-by: Alexei Starovoitov