linux-toradex.git/kernel/bpf/cpumask.c, branch v6.19

bpf: fix missing kdoc string fields in cpumask.c

2025-03-15T18:48:57+00:00

Some bpf_cpumask-related kfuncs have kdoc strings that are missing
return values. Add a the missing descriptions for the return values.

Reported-by: Alexei Starovoitov 
Signed-off-by: Emil Tsalapatis (Meta) 
Acked-by: Hou Tao 
Link: https://lore.kernel.org/r/20250309230427.26603-4-emil@etsalapatis.com
Signed-off-by: Alexei Starovoitov

bpf: add kfunc for populating cpumask bits

2025-03-15T18:48:57+00:00

Add a helper kfunc that sets the bitmap of a bpf_cpumask from BPF memory.

Signed-off-by: Emil Tsalapatis (Meta) 
Acked-by: Hou Tao 
Acked-by: Tejun Heo 
Link: https://lore.kernel.org/r/20250309230427.26603-2-emil@etsalapatis.com
Signed-off-by: Alexei Starovoitov

bpf: Remove migrate_{disable,enable} in bpf_cpumask_release()

2025-01-09T02:06:37+00:00

When BPF program invokes bpf_cpumask_release(), the migration must have
been disabled. When bpf_cpumask_release_dtor() invokes
bpf_cpumask_release(), the caller bpf_obj_free_fields() also has
disabled migration, therefore, it is OK to remove the unnecessary
migrate_{disable|enable} pair in bpf_cpumask_release().

Signed-off-by: Hou Tao 
Link: https://lore.kernel.org/r/20250108010728.207536-13-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov

bpf: Allow invoking kfuncs from BPF_PROG_TYPE_SYSCALL progs

2024-04-05T17:56:09+00:00

Currently, a set of core BPF kfuncs (e.g. bpf_task_*, bpf_cgroup_*,
bpf_cpumask_*, etc) cannot be invoked from BPF_PROG_TYPE_SYSCALL
programs. The whitelist approach taken for enabling kfuncs makes sense:
it not safe to call these kfuncs from every program type. For example,
it may not be safe to call bpf_task_acquire() in an fentry to
free_task().

BPF_PROG_TYPE_SYSCALL, on the other hand, is a perfectly safe program
type from which to invoke these kfuncs, as it's a very controlled
environment, and we should never be able to run into any of the typical
problems such as recursive invoations, acquiring references on freeing
kptrs, etc. Being able to invoke these kfuncs would be useful, as
BPF_PROG_TYPE_SYSCALL can be invoked with BPF_PROG_RUN, and would
therefore enable user space programs to synchronously call into BPF to
manipulate these kptrs.

This patch therefore enables invoking the aforementioned core kfuncs
from BPF_PROG_TYPE_SYSCALL progs.

Signed-off-by: David Vernet 
Signed-off-by: Andrii Nakryiko 
Acked-by: Andrii Nakryiko 
Acked-by: Yonghong Song 
Link: https://lore.kernel.org/bpf/20240405143041.632519-2-void@manifault.com

bpf: treewide: Annotate BPF kfuncs in BTF

2024-02-01T04:40:56+00:00

This commit marks kfuncs as such inside the .BTF_ids section. The upshot
of these annotations is that we'll be able to automatically generate
kfunc prototypes for downstream users. The process is as follows:

1. In source, use BTF_KFUNCS_START/END macro pair to mark kfuncs
2. During build, pahole injects into BTF a "bpf_kfunc" BTF_DECL_TAG for
   each function inside BTF_KFUNCS sets
3. At runtime, vmlinux or module BTF is made available in sysfs
4. At runtime, bpftool (or similar) can look at provided BTF and
   generate appropriate prototypes for functions with "bpf_kfunc" tag

To ensure future kfunc are similarly tagged, we now also return error
inside kfunc registration for untagged kfuncs. For vmlinux kfuncs,
we also WARN(), as initcall machinery does not handle errors.

Signed-off-by: Daniel Xu 
Acked-by: Benjamin Tissoires 
Link: https://lore.kernel.org/r/e55150ceecbf0a5d961e608941165c0bee7bc943.1706491398.git.dxu@dxuuu.xyz
Signed-off-by: Alexei Starovoitov

bpf: Fix dtor CFI

2023-12-16T00:25:55+00:00

Ensure the various dtor functions match their prototype and retain
their CFI signatures, since they don't have their address taken, they
are prone to not getting CFI, making them impossible to call
indirectly.

Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20231215092707.799451071@infradead.org
Signed-off-by: Alexei Starovoitov

bpf: Add bpf_cpumask_weight() kfunc

2023-12-10T05:37:33+00:00

It can be useful to query how many bits are set in a cpumask. For
example, if you want to perform special logic for the last remaining
core that's set in a mask. Let's therefore add a new
bpf_cpumask_weight() kfunc which checks how many bits are set in a mask.

Signed-off-by: David Vernet 
Acked-by: Yonghong Song 
Link: https://lore.kernel.org/r/20231207210843.168466-2-void@manifault.com
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: Convert bpf_cpumask to bpf_mem_cache_free_rcu.

2023-07-12T21:45:23+00:00

Convert bpf_cpumask to bpf_mem_cache_free_rcu.
Note that migrate_disable() in bpf_cpumask_release() is still necessary, since
bpf_cpumask_release() is a dtor. bpf_obj_free_fields() can be converted to do
migrate_disable() there in a follow up.

Signed-off-by: Alexei Starovoitov 
Signed-off-by: Daniel Borkmann 
Acked-by: David Vernet 
Link: https://lore.kernel.org/bpf/20230706033447.54696-14-alexei.starovoitov@gmail.com

bpf: Replace bpf_cpumask_any* with bpf_cpumask_any_distribute*

2023-06-12T22:09:11+00:00

We currently export the bpf_cpumask_any() and bpf_cpumask_any_and()
kfuncs. Intuitively, one would expect these to choose any CPU in the
cpumask, but what they actually do is alias to cpumask_first() and
cpmkas_first_and().

This is useless given that we already export bpf_cpumask_first() and
bpf_cpumask_first_and(), so this patch replaces them with kfuncs that
call cpumask_any_distribute() and cpumask_any_and_distribute(), which
actually choose any CPU from the cpumask (or the AND of two cpumasks for
the latter).

Signed-off-by: David Vernet 
Acked-by: Yonghong Song 
Link: https://lore.kernel.org/r/20230610035053.117605-3-void@manifault.com
Signed-off-by: Alexei Starovoitov