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bpf: Use KF_FASTCALL to mark kfuncs supporting fastcall contract

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In order to allow pahole add btf_decl_tag("bpf_fastcall") for kfuncs
supporting bpf_fastcall, mark such functions with KF_FASTCALL in
id_set8 objects.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240916091712.2929279-4-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Eduard Zingerman
2024-09-16 02:17:11 -07:00
committed by Alexei Starovoitov
parent 4f647a780f
commit da7d71bcb0
3 changed files with 4 additions and 6 deletions
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1
include/linux/btf.h
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@@ -75,6 +75,7 @@
#define KF_ITER_NEXT (1 << 9) /* kfunc implements BPF iter next method */
#define KF_ITER_DESTROY (1 << 10) /* kfunc implements BPF iter destructor */
#define KF_RCU_PROTECTED (1 << 11) /* kfunc should be protected by rcu cs when they are invoked */
#define KF_FASTCALL (1 << 12) /* kfunc supports bpf_fastcall protocol */
/*
* Tag marking a kernel function as a kfunc. This is meant to minimize the

4
kernel/bpf/helpers.c
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@@ -3052,8 +3052,8 @@ BTF_ID(func, bpf_cgroup_release_dtor)
#endif
BTF_KFUNCS_START(common_btf_ids)
BTF_ID_FLAGS(func, bpf_cast_to_kern_ctx)
BTF_ID_FLAGS(func, bpf_rdonly_cast)
BTF_ID_FLAGS(func, bpf_cast_to_kern_ctx, KF_FASTCALL)
BTF_ID_FLAGS(func, bpf_rdonly_cast, KF_FASTCALL)
BTF_ID_FLAGS(func, bpf_rcu_read_lock)
BTF_ID_FLAGS(func, bpf_rcu_read_unlock)
BTF_ID_FLAGS(func, bpf_dynptr_slice, KF_RET_NULL)

5
kernel/bpf/verifier.c
View File

@@ -16176,10 +16176,7 @@ static u32 kfunc_fastcall_clobber_mask(struct bpf_kfunc_call_arg_meta *meta)
/* Same as verifier_inlines_helper_call() but for kfuncs, see comment above */
static bool is_fastcall_kfunc_call(struct bpf_kfunc_call_arg_meta *meta)
{
if (meta->btf == btf_vmlinux)
return meta->func_id == special_kfunc_list[KF_bpf_cast_to_kern_ctx] ||
meta->func_id == special_kfunc_list[KF_bpf_rdonly_cast];
return false;
return meta->kfunc_flags & KF_FASTCALL;
}
/* LLVM define a bpf_fastcall function attribute.