From 391145ba2accc48b596f3d438af1a6255b62a555 Mon Sep 17 00:00:00 2001 From: Dave Marchevsky Date: Tue, 31 Oct 2023 14:56:24 -0700 Subject: 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 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 --- include/linux/btf.h | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'include') diff --git a/include/linux/btf.h b/include/linux/btf.h index c2231c64d60b..dc5ce962f600 100644 --- 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 -- cgit v1.2.3-70-g09d2 From 15fb6f2b6c4c3c129adc2412ae12ec15e60a6adb Mon Sep 17 00:00:00 2001 From: Dave Marchevsky Date: Tue, 31 Oct 2023 14:56:25 -0700 Subject: bpf: Add __bpf_hook_{start,end} macros 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 Cc: Yafang Shao Acked-by: Jiri Olsa Acked-by: Yafang Shao Link: https://lore.kernel.org/r/20231031215625.2343848-2-davemarchevsky@fb.com Signed-off-by: Alexei Starovoitov --- 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(-) (limited to 'include') 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 0d1c4e78fc7f..3379c64217a4 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, }, -- cgit v1.2.3-70-g09d2