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bpf: Add __bpf_hook_{start,end} macros

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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@fb.com>
Cc: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Link: https://lore.kernel.org/r/20231031215625.2343848-2-davemarchevsky@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Dave Marchevsky 2023-10-31 14:56:25 -07:00 committed by Alexei Starovoitov
parent 391145ba2a
commit 15fb6f2b6c
4 changed files with 9 additions and 16 deletions
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2
include/linux/btf.h
View File

@ -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

9
kernel/cgroup/rstat.c
View File

@ -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)

8
net/socket.c
View File

@ -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)
{

6
tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
View File

@ -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, },