bpf: Conditionally include dynptr copy kfuncs

Since commit a498ee7 ("bpf: Implement dynptr copy kfuncs"), if
CONFIG_BPF_EVENTS is not enabled, but BPF_SYSCALL and DEBUG_INFO_BTF are,
the build will break like so:

  BTFIDS  vmlinux.unstripped
WARN: resolve_btfids: unresolved symbol bpf_probe_read_user_str_dynptr
WARN: resolve_btfids: unresolved symbol bpf_probe_read_user_dynptr
WARN: resolve_btfids: unresolved symbol bpf_probe_read_kernel_str_dynptr
WARN: resolve_btfids: unresolved symbol bpf_probe_read_kernel_dynptr
WARN: resolve_btfids: unresolved symbol bpf_copy_from_user_task_str_dynptr
WARN: resolve_btfids: unresolved symbol bpf_copy_from_user_task_dynptr
WARN: resolve_btfids: unresolved symbol bpf_copy_from_user_str_dynptr
WARN: resolve_btfids: unresolved symbol bpf_copy_from_user_dynptr
make[2]: *** [scripts/Makefile.vmlinux:72: vmlinux.unstripped] Error 255
make[2]: *** Deleting file 'vmlinux.unstripped'
make[1]: *** [/repo/malin/upstream/linux/Makefile:1242: vmlinux] Error 2
make: *** [Makefile:248: __sub-make] Error 2

Guard these symbols with #ifdef CONFIG_BPF_EVENTS to resolve the problem.

Fixes: a498ee7 ("bpf: Implement dynptr copy kfuncs")
Reported-by: Yong Gu <[email protected]>
Acked-by: Mykyta Yatsenko <[email protected]>
Signed-off-by: Malin Jonsson <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Alexei Starovoitov <[email protected]>

Author: Malin Jonsson

kernel/bpf/helpers.c

@@ -4345,6 +4345,7 @@ BTF_ID_FLAGS(func, bpf_iter_kmem_cache_next, KF_ITER_NEXT | KF_RET_NULL | KF_SLE
 BTF_ID_FLAGS(func, bpf_iter_kmem_cache_destroy, KF_ITER_DESTROY | KF_SLEEPABLE)
 BTF_ID_FLAGS(func, bpf_local_irq_save)
 BTF_ID_FLAGS(func, bpf_local_irq_restore)
+#ifdef CONFIG_BPF_EVENTS
 BTF_ID_FLAGS(func, bpf_probe_read_user_dynptr)
 BTF_ID_FLAGS(func, bpf_probe_read_kernel_dynptr)
 BTF_ID_FLAGS(func, bpf_probe_read_user_str_dynptr)
@@ -4353,6 +4354,7 @@ BTF_ID_FLAGS(func, bpf_copy_from_user_dynptr, KF_SLEEPABLE)
 BTF_ID_FLAGS(func, bpf_copy_from_user_str_dynptr, KF_SLEEPABLE)
 BTF_ID_FLAGS(func, bpf_copy_from_user_task_dynptr, KF_SLEEPABLE | KF_TRUSTED_ARGS)
 BTF_ID_FLAGS(func, bpf_copy_from_user_task_str_dynptr, KF_SLEEPABLE | KF_TRUSTED_ARGS)
+#endif
 #ifdef CONFIG_DMA_SHARED_BUFFER
 BTF_ID_FLAGS(func, bpf_iter_dmabuf_new, KF_ITER_NEW | KF_SLEEPABLE)
 BTF_ID_FLAGS(func, bpf_iter_dmabuf_next, KF_ITER_NEXT | KF_RET_NULL | KF_SLEEPABLE)