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From:   Peter Zijlstra <peterz@infradead.org>
To:     Alexei Starovoitov <alexei.starovoitov@gmail.com>
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Subject: Re: [PATCH v2 2/2] x86/cfi,bpf: Fix BPF JIT call
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On Fri, Dec 08, 2023 at 12:45:51PM -0800, Alexei Starovoitov wrote:

> I mean we don't need to store a pointer to a func in stubs.
> Can it be, roughly:
> 
> extern void bpf_tcp_ca_cong_avoid(struct sock *sk, u32 ack, u32 acked);
> KCFI_MACRO(hash_of_cong_avoid, bpf_tcp_ca_cong_avoid);
> u32 __array_of_kcfi_hash[] = {hash_of_cong_avoid, hash_of_set_state,...};
>       .bpf_ops_stubs = __array_of_kcfi_hash,

But then how do I index this array? The bpf_ops_stubs thing having the
same layout at the target struct made it easy and we could use 'moff'
for both.

That also remains working if someone adds a member to the struct or
moves some members around.