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Miller" , Hideaki YOSHIFUJI , David Ahern , Thomas Gleixner , Borislav Petkov , Dave Hansen , x86@kernel.org, hpa@zytor.com, Shuah Khan , Jakub Kicinski , Jesper Dangaard Brouer , Mark Rutland , Pasha Tatashin , Ard Biesheuvel , Daniel Kiss , Steven Price , Sudeep Holla , Marc Zyngier , Peter Collingbourne , Mark Brown , Delyan Kratunov , Kumar Kartikeya Dwivedi Subject: Re: [PATCH bpf-next v4 3/6] bpf: Move is_valid_bpf_tramp_flags() to the public trampoline code Message-ID: <20220517155349.4jk5oymnjvrasw2p@MacBook-Pro.local> References: <20220517071838.3366093-1-xukuohai@huawei.com> <20220517071838.3366093-4-xukuohai@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220517071838.3366093-4-xukuohai@huawei.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 17, 2022 at 03:18:35AM -0400, Xu Kuohai wrote: > > +static bool is_valid_bpf_tramp_flags(unsigned int flags) > +{ > + if ((flags & BPF_TRAMP_F_RESTORE_REGS) && > + (flags & BPF_TRAMP_F_SKIP_FRAME)) > + return false; > + > + /* BPF_TRAMP_F_RET_FENTRY_RET is only used by bpf_struct_ops, > + * and it must be used alone. > + */ > + if ((flags & BPF_TRAMP_F_RET_FENTRY_RET) && > + (flags & ~BPF_TRAMP_F_RET_FENTRY_RET)) > + return false; > + > + return true; > +} > + > +int bpf_prepare_trampoline(struct bpf_tramp_image *tr, void *image, > + void *image_end, const struct btf_func_model *m, > + u32 flags, struct bpf_tramp_links *tlinks, > + void *orig_call) > +{ > + if (!is_valid_bpf_tramp_flags(flags)) > + return -EINVAL; > + > + return arch_prepare_bpf_trampoline(tr, image, image_end, m, flags, > + tlinks, orig_call); > +} It's an overkill to introduce a new helper function just to validate flags that almost compile time constants. The flags are not user supplied. Please move /* BPF_TRAMP_F_RET_FENTRY_RET is only used by bpf_struct_ops ... */ comment to bpf_struct_ops.c right before it calls arch_prepare_bpf_trampoline() And add a comment to trampoline.c saying that BPF_TRAMP_F_RESTORE_REGS and BPF_TRAMP_F_SKIP_FRAME should not be set together. We could add a warn_on there or in arch code, but feels like overkill.