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>> >> bpf_for_each invokes the "callback_fn" nr_iterations number of times >> or until the callback_fn returns 1. >> >> A few things to please note: >> ~ The "u64 flags" parameter is currently unused but is included in >> case a future use case for it arises. >> ~ In the kernel-side implementation of bpf_for_each >> (kernel/bpf/bpf_iter.c), >> bpf_callback_t is used as the callback function cast. >> ~ A program can have nested bpf_for_each calls but the program must >> still adhere to the verifier constraint of its stack depth (the stack >> depth >> cannot exceed MAX_BPF_STACK)) >> ~ The next patch will include the tests and benchmark >> >> Signed-off-by: Joanne Koong >> --- >>   include/linux/bpf.h            |  1 + >>   include/uapi/linux/bpf.h       | 23 +++++++++++++++++++++++ >>   kernel/bpf/bpf_iter.c          | 32 ++++++++++++++++++++++++++++++++ >>   kernel/bpf/helpers.c           |  2 ++ >>   kernel/bpf/verifier.c          | 28 ++++++++++++++++++++++++++++ >>   tools/include/uapi/linux/bpf.h | 23 +++++++++++++++++++++++ >>   6 files changed, 109 insertions(+) >> >> diff --git a/include/linux/bpf.h b/include/linux/bpf.h >> index 6deebf8bf78f..d9b69a896c91 100644 >> --- a/include/linux/bpf.h >> +++ b/include/linux/bpf.h >> @@ -2107,6 +2107,7 @@ extern const struct bpf_func_proto >> bpf_get_socket_ptr_cookie_proto; >>   extern const struct bpf_func_proto bpf_task_storage_get_proto; >>   extern const struct bpf_func_proto bpf_task_storage_delete_proto; >>   extern const struct bpf_func_proto bpf_for_each_map_elem_proto; >> +extern const struct bpf_func_proto bpf_for_each_proto; >>   extern const struct bpf_func_proto bpf_btf_find_by_name_kind_proto; >>   extern const struct bpf_func_proto bpf_sk_setsockopt_proto; >>   extern const struct bpf_func_proto bpf_sk_getsockopt_proto; >> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h >> index bd0c9f0487f6..ea5098920ed2 100644 >> --- a/include/uapi/linux/bpf.h >> +++ b/include/uapi/linux/bpf.h >> @@ -4750,6 +4750,28 @@ union bpf_attr { >>    *        The number of traversed map elements for success, >> **-EINVAL** for >>    *        invalid **flags**. >>    * >> + * long bpf_for_each(u32 nr_iterations, void *callback_fn, void >> *callback_ctx, u64 flags) >> + *    Description >> + *        For **nr_iterations**, call **callback_fn** function with >> + *        **callback_ctx** as the context parameter. >> + *        The **callback_fn** should be a static function and >> + *        the **callback_ctx** should be a pointer to the stack. >> + *        The **flags** is used to control certain aspects of the >> helper. >> + *        Currently, the **flags** must be 0. >> + * >> + *        long (\*callback_fn)(u32 index, void \*ctx); >> + * >> + *        where **index** is the current index in the iteration. The >> index >> + *        is zero-indexed. >> + * >> + *        If **callback_fn** returns 0, the helper will continue to >> the next >> + *        iteration. If return value is 1, the helper will skip the >> rest of >> + *        the iterations and return. Other return values are not >> used now. >> + * >> + *    Return >> + *        The number of iterations performed, **-EINVAL** for >> invalid **flags** >> + *        or a null **callback_fn**. > > I think verifier enforced non-null callback_fn, right? > Yes, great point - I will remove the "or a null **callback_fn**" part. >> + * >>    * long bpf_snprintf(char *str, u32 str_size, const char *fmt, u64 >> *data, u32 data_len) >>    *    Description >>    *        Outputs a string into the **str** buffer of size >> **str_size** >> @@ -5105,6 +5127,7 @@ union bpf_attr { >>       FN(sock_from_file),        \ >>       FN(check_mtu),            \ >>       FN(for_each_map_elem),        \ >> +    FN(for_each),            \ > > Please put for_each helper at the end of list. Otherwise, it will > break uapi. > Gotcha. I will make this change for v2 and remember to do this in the future as well! >>       FN(snprintf),            \ >>       FN(sys_bpf),            \ >>       FN(btf_find_by_name_kind),    \ >> diff --git a/kernel/bpf/bpf_iter.c b/kernel/bpf/bpf_iter.c >> index b2ee45064e06..cb742c50898a 100644 >> --- a/kernel/bpf/bpf_iter.c >> +++ b/kernel/bpf/bpf_iter.c >> @@ -714,3 +714,35 @@ const struct bpf_func_proto >> bpf_for_each_map_elem_proto = { >>       .arg3_type    = ARG_PTR_TO_STACK_OR_NULL, >>       .arg4_type    = ARG_ANYTHING, >>   }; >> + > [...]