bpf: Add __bpf_kfunc_{start,end}_defs macros

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 <davemarchevsky@fb.com>
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Cc: Jiri Olsa <olsajiri@gmail.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: David Vernet <void@manifault.com>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Link: https://lore.kernel.org/r/20231031215625.2343848-1-davemarchevsky@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/Documentation/bpf/kfuncs.rst b/Documentation/bpf/kfuncs.rst
index 0d2647f..723408e 100644 (file)
--- a/Documentation/bpf/kfuncs.rst
+++ b/Documentation/bpf/kfuncs.rst
@@ -37,16 +37,14 @@ prototype in a header for the wrapper kfunc.
 An example is given below::
 
         /* Disables missing prototype warnings */
-        __diag_push();
-        __diag_ignore_all("-Wmissing-prototypes",
-                          "Global kfuncs as their definitions will be in BTF");
+        __bpf_kfunc_start_defs();
 
         __bpf_kfunc struct task_struct *bpf_find_get_task_by_vpid(pid_t nr)
         {
                 return find_get_task_by_vpid(nr);
         }
 
-        __diag_pop();
+        __bpf_kfunc_end_defs();
 
 A wrapper kfunc is often needed when we need to annotate parameters of the
 kfunc. Otherwise one may directly make the kfunc visible to the BPF program by

diff --git a/include/linux/btf.h b/include/linux/btf.h
index c2231c6..dc5ce96 100644 (file)
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -84,6 +84,15 @@
  */
 #define __bpf_kfunc __used noinline
 
+#define __bpf_kfunc_start_defs()                                              \
+       __diag_push();                                                         \
+       __diag_ignore_all("-Wmissing-declarations",                            \
+                         "Global kfuncs as their definitions will be in BTF");\
+       __diag_ignore_all("-Wmissing-prototypes",                              \
+                         "Global kfuncs as their definitions will be in BTF")
+
+#define __bpf_kfunc_end_defs() __diag_pop()
+
 /*
  * Return the name of the passed struct, if exists, or halt the build if for
  * example the structure gets renamed. In this way, developers have to revisit

diff --git a/kernel/bpf/bpf_iter.c b/kernel/bpf/bpf_iter.c
index 833faa0..0fae791 100644 (file)
--- a/kernel/bpf/bpf_iter.c
+++ b/kernel/bpf/bpf_iter.c
@@ -782,9 +782,7 @@ struct bpf_iter_num_kern {
        int end; /* final value, exclusive */
 } __aligned(8);
 
-__diag_push();
-__diag_ignore_all("-Wmissing-prototypes",
-                 "Global functions as their definitions will be in vmlinux BTF");
+__bpf_kfunc_start_defs();
 
 __bpf_kfunc int bpf_iter_num_new(struct bpf_iter_num *it, int start, int end)
 {
@@ -843,4 +841,4 @@ __bpf_kfunc void bpf_iter_num_destroy(struct bpf_iter_num *it)
        s->cur = s->end = 0;
 }
 
-__diag_pop();
+__bpf_kfunc_end_defs();

diff --git a/kernel/bpf/cgroup_iter.c b/kernel/bpf/cgroup_iter.c
index 209e513..d1b5c56 100644 (file)
--- a/kernel/bpf/cgroup_iter.c
+++ b/kernel/bpf/cgroup_iter.c
@@ -305,9 +305,7 @@ struct bpf_iter_css_kern {
        unsigned int flags;
 } __attribute__((aligned(8)));
 
-__diag_push();
-__diag_ignore_all("-Wmissing-prototypes",
-               "Global functions as their definitions will be in vmlinux BTF");
+__bpf_kfunc_start_defs();
 
 __bpf_kfunc int bpf_iter_css_new(struct bpf_iter_css *it,
                struct cgroup_subsys_state *start, unsigned int flags)
@@ -358,4 +356,4 @@ __bpf_kfunc void bpf_iter_css_destroy(struct bpf_iter_css *it)
 {
 }
 
-__diag_pop();
\ No newline at end of file
+__bpf_kfunc_end_defs();

diff --git a/kernel/bpf/cpumask.c b/kernel/bpf/cpumask.c
index 6983af8..e01c741 100644 (file)
--- a/kernel/bpf/cpumask.c
+++ b/kernel/bpf/cpumask.c
@@ -34,9 +34,7 @@ static bool cpu_valid(u32 cpu)
        return cpu < nr_cpu_ids;
 }
 
-__diag_push();
-__diag_ignore_all("-Wmissing-prototypes",
-                 "Global kfuncs as their definitions will be in BTF");
+__bpf_kfunc_start_defs();
 
 /**
  * bpf_cpumask_create() - Create a mutable BPF cpumask.
@@ -407,7 +405,7 @@ __bpf_kfunc u32 bpf_cpumask_any_and_distribute(const struct cpumask *src1,
        return cpumask_any_and_distribute(src1, src2);
 }
 
-__diag_pop();
+__bpf_kfunc_end_defs();
 
 BTF_SET8_START(cpumask_kfunc_btf_ids)
 BTF_ID_FLAGS(func, bpf_cpumask_create, KF_ACQUIRE | KF_RET_NULL)

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 95449ea..abe8210 100644 (file)
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1886,9 +1886,7 @@ void bpf_rb_root_free(const struct btf_field *field, void *rb_root,
        }
 }
 
-__diag_push();
-__diag_ignore_all("-Wmissing-prototypes",
-                 "Global functions as their definitions will be in vmlinux BTF");
+__bpf_kfunc_start_defs();
 
 __bpf_kfunc void *bpf_obj_new_impl(u64 local_type_id__k, void *meta__ign)
 {
@@ -2505,7 +2503,7 @@ __bpf_kfunc void bpf_throw(u64 cookie)
        WARN(1, "A call to BPF exception callback should never return\n");
 }
 
-__diag_pop();
+__bpf_kfunc_end_defs();
 
 BTF_SET8_START(generic_btf_ids)
 #ifdef CONFIG_KEXEC_CORE

diff --git a/kernel/bpf/map_iter.c b/kernel/bpf/map_iter.c
index 6fc9dae..6abd7c5 100644 (file)
--- a/kernel/bpf/map_iter.c
+++ b/kernel/bpf/map_iter.c
@@ -193,9 +193,7 @@ static int __init bpf_map_iter_init(void)
 
 late_initcall(bpf_map_iter_init);
 
-__diag_push();
-__diag_ignore_all("-Wmissing-prototypes",
-                 "Global functions as their definitions will be in vmlinux BTF");
+__bpf_kfunc_start_defs();
 
 __bpf_kfunc s64 bpf_map_sum_elem_count(const struct bpf_map *map)
 {
@@ -213,7 +211,7 @@ __bpf_kfunc s64 bpf_map_sum_elem_count(const struct bpf_map *map)
        return ret;
 }
 
-__diag_pop();
+__bpf_kfunc_end_defs();
 
 BTF_SET8_START(bpf_map_iter_kfunc_ids)
 BTF_ID_FLAGS(func, bpf_map_sum_elem_count, KF_TRUSTED_ARGS)

diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c
index 8967d1a..4e156dc 100644 (file)
--- a/kernel/bpf/task_iter.c
+++ b/kernel/bpf/task_iter.c
@@ -822,9 +822,7 @@ struct bpf_iter_task_vma_kern {
        struct bpf_iter_task_vma_kern_data *data;
 } __attribute__((aligned(8)));
 
-__diag_push();
-__diag_ignore_all("-Wmissing-prototypes",
-                 "Global functions as their definitions will be in vmlinux BTF");
+__bpf_kfunc_start_defs();
 
 __bpf_kfunc int bpf_iter_task_vma_new(struct bpf_iter_task_vma *it,
                                      struct task_struct *task, u64 addr)
@@ -890,7 +888,7 @@ __bpf_kfunc void bpf_iter_task_vma_destroy(struct bpf_iter_task_vma *it)
        }
 }
 
-__diag_pop();
+__bpf_kfunc_end_defs();
 
 #ifdef CONFIG_CGROUPS
 
@@ -902,9 +900,7 @@ struct bpf_iter_css_task_kern {
        struct css_task_iter *css_it;
 } __attribute__((aligned(8)));
 
-__diag_push();
-__diag_ignore_all("-Wmissing-prototypes",
-                 "Global functions as their definitions will be in vmlinux BTF");
+__bpf_kfunc_start_defs();
 
 __bpf_kfunc int bpf_iter_css_task_new(struct bpf_iter_css_task *it,
                struct cgroup_subsys_state *css, unsigned int flags)
@@ -950,7 +946,7 @@ __bpf_kfunc void bpf_iter_css_task_destroy(struct bpf_iter_css_task *it)
        bpf_mem_free(&bpf_global_ma, kit->css_it);
 }
 
-__diag_pop();
+__bpf_kfunc_end_defs();
 
 #endif /* CONFIG_CGROUPS */
 
@@ -973,9 +969,7 @@ enum {
        BPF_TASK_ITER_PROC_THREADS
 };
 
-__diag_push();
-__diag_ignore_all("-Wmissing-prototypes",
-                 "Global functions as their definitions will be in vmlinux BTF");
+__bpf_kfunc_start_defs();
 
 __bpf_kfunc int bpf_iter_task_new(struct bpf_iter_task *it,
                struct task_struct *task__nullable, unsigned int flags)
@@ -1045,7 +1039,7 @@ __bpf_kfunc void bpf_iter_task_destroy(struct bpf_iter_task *it)
 {
 }
 
-__diag_pop();
+__bpf_kfunc_end_defs();
 
 DEFINE_PER_CPU(struct mmap_unlock_irq_work, mmap_unlock_work);
 

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index df697c7..84e8a0f 100644 (file)
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1252,9 +1252,7 @@ static const struct bpf_func_proto bpf_get_func_arg_cnt_proto = {
 };
 
 #ifdef CONFIG_KEYS
-__diag_push();
-__diag_ignore_all("-Wmissing-prototypes",
-                 "kfuncs which will be used in BPF programs");
+__bpf_kfunc_start_defs();
 
 /**
  * bpf_lookup_user_key - lookup a key by its serial
@@ -1404,7 +1402,7 @@ __bpf_kfunc int bpf_verify_pkcs7_signature(struct bpf_dynptr_kern *data_ptr,
 }
 #endif /* CONFIG_SYSTEM_DATA_VERIFICATION */
 
-__diag_pop();
+__bpf_kfunc_end_defs();
 
 BTF_SET8_START(key_sig_kfunc_set)
 BTF_ID_FLAGS(func, bpf_lookup_user_key, KF_ACQUIRE | KF_RET_NULL | KF_SLEEPABLE)

diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index 0841f8d..c9fdcc5 100644 (file)
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -503,9 +503,8 @@ out:
  * architecture dependent calling conventions. 7+ can be supported in the
  * future.
  */
-__diag_push();
-__diag_ignore_all("-Wmissing-prototypes",
-                 "Global functions as their definitions will be in vmlinux BTF");
+__bpf_kfunc_start_defs();
+
 __bpf_kfunc int bpf_fentry_test1(int a)
 {
        return a + 1;
@@ -605,7 +604,7 @@ __bpf_kfunc void bpf_kfunc_call_memb_release(struct prog_test_member *p)
 {
 }
 
-__diag_pop();
+__bpf_kfunc_end_defs();
 
 BTF_SET8_START(bpf_test_modify_return_ids)
 BTF_ID_FLAGS(func, bpf_modify_return_test)

diff --git a/net/core/filter.c b/net/core/filter.c
index 21d7510..383f96b 100644 (file)
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -11767,9 +11767,7 @@ bpf_sk_base_func_proto(enum bpf_func_id func_id)
        return func;
 }
 
-__diag_push();
-__diag_ignore_all("-Wmissing-prototypes",
-                 "Global functions as their definitions will be in vmlinux BTF");
+__bpf_kfunc_start_defs();
 __bpf_kfunc int bpf_dynptr_from_skb(struct sk_buff *skb, u64 flags,
                                    struct bpf_dynptr_kern *ptr__uninit)
 {
@@ -11816,7 +11814,7 @@ __bpf_kfunc int bpf_sock_addr_set_sun_path(struct bpf_sock_addr_kern *sa_kern,
 
        return 0;
 }
-__diag_pop();
+__bpf_kfunc_end_defs();
 
 int bpf_dynptr_from_skb_rdonly(struct sk_buff *skb, u64 flags,
                               struct bpf_dynptr_kern *ptr__uninit)
@@ -11879,10 +11877,7 @@ static int __init bpf_kfunc_init(void)
 }
 late_initcall(bpf_kfunc_init);
 
-/* Disables missing prototype warnings */
-__diag_push();
-__diag_ignore_all("-Wmissing-prototypes",
-                 "Global functions as their definitions will be in vmlinux BTF");
+__bpf_kfunc_start_defs();
 
 /* bpf_sock_destroy: Destroy the given socket with ECONNABORTED error code.
  *
@@ -11916,7 +11911,7 @@ __bpf_kfunc int bpf_sock_destroy(struct sock_common *sock)
        return sk->sk_prot->diag_destroy(sk, ECONNABORTED);
 }
 
-__diag_pop()
+__bpf_kfunc_end_defs();
 
 BTF_SET8_START(bpf_sk_iter_kfunc_ids)
 BTF_ID_FLAGS(func, bpf_sock_destroy, KF_TRUSTED_ARGS)

diff --git a/net/core/xdp.c b/net/core/xdp.c
index df4789a..b6f1d6d 100644 (file)
--- a/net/core/xdp.c
+++ b/net/core/xdp.c
@@ -696,9 +696,7 @@ struct xdp_frame *xdpf_clone(struct xdp_frame *xdpf)
        return nxdpf;
 }
 
-__diag_push();
-__diag_ignore_all("-Wmissing-prototypes",
-                 "Global functions as their definitions will be in vmlinux BTF");
+__bpf_kfunc_start_defs();
 
 /**
  * bpf_xdp_metadata_rx_timestamp - Read XDP frame RX timestamp.
@@ -738,7 +736,7 @@ __bpf_kfunc int bpf_xdp_metadata_rx_hash(const struct xdp_md *ctx, u32 *hash,
        return -EOPNOTSUPP;
 }
 
-__diag_pop();
+__bpf_kfunc_end_defs();
 
 BTF_SET8_START(xdp_metadata_kfunc_ids)
 #define XDP_METADATA_KFUNC(_, __, name, ___) BTF_ID_FLAGS(func, name, KF_TRUSTED_ARGS)

diff --git a/net/ipv4/fou_bpf.c b/net/ipv4/fou_bpf.c
index 3760a14..4da03bf 100644 (file)
--- a/net/ipv4/fou_bpf.c
+++ b/net/ipv4/fou_bpf.c
@@ -22,9 +22,7 @@ enum bpf_fou_encap_type {
        FOU_BPF_ENCAP_GUE,
 };
 
-__diag_push();
-__diag_ignore_all("-Wmissing-prototypes",
-                 "Global functions as their definitions will be in BTF");
+__bpf_kfunc_start_defs();
 
 /* bpf_skb_set_fou_encap - Set FOU encap parameters
  *
@@ -100,7 +98,7 @@ __bpf_kfunc int bpf_skb_get_fou_encap(struct __sk_buff *skb_ctx,
        return 0;
 }
 
-__diag_pop()
+__bpf_kfunc_end_defs();
 
 BTF_SET8_START(fou_kfunc_set)
 BTF_ID_FLAGS(func, bpf_skb_set_fou_encap)

diff --git a/net/netfilter/nf_conntrack_bpf.c b/net/netfilter/nf_conntrack_bpf.c
index b21799d..475358e 100644 (file)
--- a/net/netfilter/nf_conntrack_bpf.c
+++ b/net/netfilter/nf_conntrack_bpf.c
@@ -230,9 +230,7 @@ static int _nf_conntrack_btf_struct_access(struct bpf_verifier_log *log,
        return 0;
 }
 
-__diag_push();
-__diag_ignore_all("-Wmissing-prototypes",
-                 "Global functions as their definitions will be in nf_conntrack BTF");
+__bpf_kfunc_start_defs();
 
 /* bpf_xdp_ct_alloc - Allocate a new CT entry
  *
@@ -467,7 +465,7 @@ __bpf_kfunc int bpf_ct_change_status(struct nf_conn *nfct, u32 status)
        return nf_ct_change_status_common(nfct, status);
 }
 
-__diag_pop()
+__bpf_kfunc_end_defs();
 
 BTF_SET8_START(nf_ct_kfunc_set)
 BTF_ID_FLAGS(func, bpf_xdp_ct_alloc, KF_ACQUIRE | KF_RET_NULL)

diff --git a/net/netfilter/nf_nat_bpf.c b/net/netfilter/nf_nat_bpf.c
index 141ee77..6e3b2f5 100644 (file)
--- a/net/netfilter/nf_nat_bpf.c
+++ b/net/netfilter/nf_nat_bpf.c
@@ -12,9 +12,7 @@
 #include <net/netfilter/nf_conntrack_core.h>
 #include <net/netfilter/nf_nat.h>
 
-__diag_push();
-__diag_ignore_all("-Wmissing-prototypes",
-                 "Global functions as their definitions will be in nf_nat BTF");
+__bpf_kfunc_start_defs();
 
 /* bpf_ct_set_nat_info - Set source or destination nat address
  *
@@ -54,7 +52,7 @@ __bpf_kfunc int bpf_ct_set_nat_info(struct nf_conn___init *nfct,
        return nf_nat_setup_info(ct, &range, manip) == NF_DROP ? -ENOMEM : 0;
 }
 
-__diag_pop()
+__bpf_kfunc_end_defs();
 
 BTF_SET8_START(nf_nat_kfunc_set)
 BTF_ID_FLAGS(func, bpf_ct_set_nat_info, KF_TRUSTED_ARGS)

diff --git a/net/xfrm/xfrm_interface_bpf.c b/net/xfrm/xfrm_interface_bpf.c
index d74f3fd..7d5e920 100644 (file)
--- a/net/xfrm/xfrm_interface_bpf.c
+++ b/net/xfrm/xfrm_interface_bpf.c
@@ -27,9 +27,7 @@ struct bpf_xfrm_info {
        int link;
 };
 
-__diag_push();
-__diag_ignore_all("-Wmissing-prototypes",
-                 "Global functions as their definitions will be in xfrm_interface BTF");
+__bpf_kfunc_start_defs();
 
 /* bpf_skb_get_xfrm_info - Get XFRM metadata
  *
@@ -93,7 +91,7 @@ __bpf_kfunc int bpf_skb_set_xfrm_info(struct __sk_buff *skb_ctx, const struct bp
        return 0;
 }
 
-__diag_pop()
+__bpf_kfunc_end_defs();
 
 BTF_SET8_START(xfrm_ifc_kfunc_set)
 BTF_ID_FLAGS(func, bpf_skb_get_xfrm_info)