On Tue, Oct 31, 2023 at 02:56:25PM -0700, Dave Marchevsky wrote: > Not all uses of __diag_ignore_all(...) in BPF-related code in order to > suppress warnings are wrapping kfunc definitions. Some "hook point" > definitions - small functions meant to be used as attach points for > fentry and similar BPF progs - need to suppress -Wmissing-declarations. > > We could use __bpf_kfunc_{start,end}_defs added in the previous patch in > such cases, but this might be confusing to someone unfamiliar with BPF > internals. Instead, this patch adds __bpf_hook_{start,end} macros, > currently having the same effect as __bpf_kfunc_{start,end}_defs, then > uses them to suppress warnings for two hook points in the kernel itself > and some bpf_testmod hook points as well. > > Signed-off-by: Dave Marchevsky <davemarchevsky@xxxxxx> > Cc: Yafang Shao <laoar.shao@xxxxxxxxx> Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx> jirka > --- > > This patch was added in v2 in response to convo on v1's thread. > > include/linux/btf.h | 2 ++ > kernel/cgroup/rstat.c | 9 +++------ > net/socket.c | 8 ++------ > tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c | 6 ++---- > 4 files changed, 9 insertions(+), 16 deletions(-) > > diff --git a/include/linux/btf.h b/include/linux/btf.h > index dc5ce962f600..59d404e22814 100644 > --- a/include/linux/btf.h > +++ b/include/linux/btf.h > @@ -92,6 +92,8 @@ > "Global kfuncs as their definitions will be in BTF") > > #define __bpf_kfunc_end_defs() __diag_pop() > +#define __bpf_hook_start() __bpf_kfunc_start_defs() > +#define __bpf_hook_end() __bpf_kfunc_end_defs() > > /* > * Return the name of the passed struct, if exists, or halt the build if for > diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c > index d80d7a608141..c0adb7254b45 100644 > --- a/kernel/cgroup/rstat.c > +++ b/kernel/cgroup/rstat.c > @@ -156,19 +156,16 @@ static struct cgroup *cgroup_rstat_cpu_pop_updated(struct cgroup *pos, > * optimize away the callsite. Therefore, __weak is needed to ensure that the > * call is still emitted, by telling the compiler that we don't know what the > * function might eventually be. > - * > - * __diag_* below are needed to dismiss the missing prototype warning. > */ > -__diag_push(); > -__diag_ignore_all("-Wmissing-prototypes", > - "kfuncs which will be used in BPF programs"); > + > +__bpf_hook_start(); > > __weak noinline void bpf_rstat_flush(struct cgroup *cgrp, > struct cgroup *parent, int cpu) > { > } > > -__diag_pop(); > +__bpf_hook_end(); > > /* see cgroup_rstat_flush() */ > static void cgroup_rstat_flush_locked(struct cgroup *cgrp) > diff --git a/net/socket.c b/net/socket.c > index c4a6f5532955..cd4d9ae2144f 100644 > --- a/net/socket.c > +++ b/net/socket.c > @@ -1685,20 +1685,16 @@ struct file *__sys_socket_file(int family, int type, int protocol) > * Therefore, __weak is needed to ensure that the call is still > * emitted, by telling the compiler that we don't know what the > * function might eventually be. > - * > - * __diag_* below are needed to dismiss the missing prototype warning. > */ > > -__diag_push(); > -__diag_ignore_all("-Wmissing-prototypes", > - "A fmod_ret entry point for BPF programs"); > +__bpf_hook_start(); > > __weak noinline int update_socket_protocol(int family, int type, int protocol) > { > return protocol; > } > > -__diag_pop(); > +__bpf_hook_end(); > > int __sys_socket(int family, int type, int protocol) > { > diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c > index a5e246f7b202..91907b321f91 100644 > --- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c > +++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c > @@ -39,9 +39,7 @@ struct bpf_testmod_struct_arg_4 { > int b; > }; > > -__diag_push(); > -__diag_ignore_all("-Wmissing-prototypes", > - "Global functions as their definitions will be in bpf_testmod.ko BTF"); > +__bpf_hook_start(); > > noinline int > bpf_testmod_test_struct_arg_1(struct bpf_testmod_struct_arg_2 a, int b, int c) { > @@ -335,7 +333,7 @@ noinline int bpf_fentry_shadow_test(int a) > } > EXPORT_SYMBOL_GPL(bpf_fentry_shadow_test); > > -__diag_pop(); > +__bpf_hook_end(); > > static struct bin_attribute bin_attr_bpf_testmod_file __ro_after_init = { > .attr = { .name = "bpf_testmod", .mode = 0666, }, > -- > 2.34.1 > >