From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-17.6 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A5645C433F5 for ; Tue, 7 Sep 2021 11:13:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8244A610FF for ; Tue, 7 Sep 2021 11:13:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245614AbhIGLOz (ORCPT ); Tue, 7 Sep 2021 07:14:55 -0400 Received: from szxga01-in.huawei.com ([45.249.212.187]:19014 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245739AbhIGLOy (ORCPT ); Tue, 7 Sep 2021 07:14:54 -0400 Received: from dggemv703-chm.china.huawei.com (unknown [172.30.72.55]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4H3jGK1cJ0zbmB0; Tue, 7 Sep 2021 19:09:45 +0800 (CST) Received: from dggpeml500025.china.huawei.com (7.185.36.35) by dggemv703-chm.china.huawei.com (10.3.19.46) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.8; Tue, 7 Sep 2021 19:13:45 +0800 Received: from [10.174.176.117] (10.174.176.117) by dggpeml500025.china.huawei.com (7.185.36.35) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.8; Tue, 7 Sep 2021 19:13:44 +0800 Subject: Re: [PATCH bpf] bpf: handle return value of BPF_PROG_TYPE_STRUCT_OPS prog To: , Alexei Starovoitov , "Daniel Borkmann" , Andrii Nakryiko , CC: Martin KaFai Lau , KP Singh References: <20210901085344.3052333-1-houtao1@huawei.com> From: Hou Tao Message-ID: Date: Tue, 7 Sep 2021 19:13:44 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <20210901085344.3052333-1-houtao1@huawei.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Content-Language: en-US X-Originating-IP: [10.174.176.117] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggpeml500025.china.huawei.com (7.185.36.35) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org ping ? +cc netdev On 9/1/2021 4:53 PM, Hou Tao wrote: > Currently if a function ptr in struct_ops has a return value, its > caller will get a random return value from it, because the return > value of related BPF_PROG_TYPE_STRUCT_OPS prog is just dropped. > > So adding a new flag BPF_TRAMP_F_RET_FENTRY_RET to tell bpf trampoline > to save and return the return value of struct_ops prog if ret_size of > the function ptr is greater than 0. Also restricting the flag to be > used alone. > > Fixes: 85d33df357b6 ("bpf: Introduce BPF_MAP_TYPE_STRUCT_OPS") > Signed-off-by: Hou Tao > --- > arch/x86/net/bpf_jit_comp.c | 53 ++++++++++++++++++++++++++++--------- > include/linux/bpf.h | 2 ++ > kernel/bpf/bpf_struct_ops.c | 7 +++-- > 3 files changed, 47 insertions(+), 15 deletions(-) > > diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c > index 16d76f814e9b..47780844598a 100644 > --- a/arch/x86/net/bpf_jit_comp.c > +++ b/arch/x86/net/bpf_jit_comp.c > @@ -1744,7 +1744,7 @@ static void restore_regs(const struct btf_func_model *m, u8 **prog, int nr_args, > } > > static int invoke_bpf_prog(const struct btf_func_model *m, u8 **pprog, > - struct bpf_prog *p, int stack_size, bool mod_ret) > + struct bpf_prog *p, int stack_size, bool save_ret) > { > u8 *prog = *pprog; > u8 *jmp_insn; > @@ -1777,11 +1777,15 @@ static int invoke_bpf_prog(const struct btf_func_model *m, u8 **pprog, > if (emit_call(&prog, p->bpf_func, prog)) > return -EINVAL; > > - /* BPF_TRAMP_MODIFY_RETURN trampolines can modify the return > + /* > + * BPF_TRAMP_MODIFY_RETURN trampolines can modify the return > * of the previous call which is then passed on the stack to > * the next BPF program. > + * > + * BPF_TRAMP_FENTRY trampoline may need to return the return > + * value of BPF_PROG_TYPE_STRUCT_OPS prog. > */ > - if (mod_ret) > + if (save_ret) > emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -8); > > /* replace 2 nops with JE insn, since jmp target is known */ > @@ -1828,13 +1832,15 @@ static int emit_cond_near_jump(u8 **pprog, void *func, void *ip, u8 jmp_cond) > } > > static int invoke_bpf(const struct btf_func_model *m, u8 **pprog, > - struct bpf_tramp_progs *tp, int stack_size) > + struct bpf_tramp_progs *tp, int stack_size, > + bool save_ret) > { > int i; > u8 *prog = *pprog; > > for (i = 0; i < tp->nr_progs; i++) { > - if (invoke_bpf_prog(m, &prog, tp->progs[i], stack_size, false)) > + if (invoke_bpf_prog(m, &prog, tp->progs[i], stack_size, > + save_ret)) > return -EINVAL; > } > *pprog = prog; > @@ -1877,6 +1883,23 @@ static int invoke_bpf_mod_ret(const struct btf_func_model *m, u8 **pprog, > return 0; > } > > +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; > +} > + > /* Example: > * __be16 eth_type_trans(struct sk_buff *skb, struct net_device *dev); > * its 'struct btf_func_model' will be nr_args=2 > @@ -1949,17 +1972,19 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i > struct bpf_tramp_progs *fmod_ret = &tprogs[BPF_TRAMP_MODIFY_RETURN]; > u8 **branches = NULL; > u8 *prog; > + bool save_ret; > > /* x86-64 supports up to 6 arguments. 7+ can be added in the future */ > if (nr_args > 6) > return -ENOTSUPP; > > - if ((flags & BPF_TRAMP_F_RESTORE_REGS) && > - (flags & BPF_TRAMP_F_SKIP_FRAME)) > + if (!is_valid_bpf_tramp_flags(flags)) > return -EINVAL; > > - if (flags & BPF_TRAMP_F_CALL_ORIG) > - stack_size += 8; /* room for return value of orig_call */ > + /* room for return value of orig_call or fentry prog */ > + save_ret = flags & (BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_RET_FENTRY_RET); > + if (save_ret) > + stack_size += 8; > > if (flags & BPF_TRAMP_F_SKIP_FRAME) > /* skip patched call instruction and point orig_call to actual > @@ -1986,7 +2011,8 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i > } > > if (fentry->nr_progs) > - if (invoke_bpf(m, &prog, fentry, stack_size)) > + if (invoke_bpf(m, &prog, fentry, stack_size, > + flags & BPF_TRAMP_F_RET_FENTRY_RET)) > return -EINVAL; > > if (fmod_ret->nr_progs) { > @@ -2033,7 +2059,7 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i > } > > if (fexit->nr_progs) > - if (invoke_bpf(m, &prog, fexit, stack_size)) { > + if (invoke_bpf(m, &prog, fexit, stack_size, false)) { > ret = -EINVAL; > goto cleanup; > } > @@ -2053,9 +2079,10 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i > ret = -EINVAL; > goto cleanup; > } > - /* restore original return value back into RAX */ > - emit_ldx(&prog, BPF_DW, BPF_REG_0, BPF_REG_FP, -8); > } > + /* restore return value of orig_call or fentry prog back into RAX */ > + if (save_ret) > + emit_ldx(&prog, BPF_DW, BPF_REG_0, BPF_REG_FP, -8); > > EMIT1(0x5B); /* pop rbx */ > EMIT1(0xC9); /* leave */ > diff --git a/include/linux/bpf.h b/include/linux/bpf.h > index e8e2b0393ca9..85413eb368de 100644 > --- a/include/linux/bpf.h > +++ b/include/linux/bpf.h > @@ -553,6 +553,8 @@ struct btf_func_model { > * programs only. Should not be used with normal calls and indirect calls. > */ > #define BPF_TRAMP_F_SKIP_FRAME BIT(2) > +/* Return the return value of fentry prog. Only used by bpf_struct_ops. */ > +#define BPF_TRAMP_F_RET_FENTRY_RET BIT(3) > > /* Each call __bpf_prog_enter + call bpf_func + call __bpf_prog_exit is ~50 > * bytes on x86. Pick a number to fit into BPF_IMAGE_SIZE / 2 > diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c > index 70f6fd4fa305..2ce17447fb76 100644 > --- a/kernel/bpf/bpf_struct_ops.c > +++ b/kernel/bpf/bpf_struct_ops.c > @@ -367,6 +367,7 @@ static int bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key, > const struct btf_type *mtype, *ptype; > struct bpf_prog *prog; > u32 moff; > + u32 flags; > > moff = btf_member_bit_offset(t, member) / 8; > ptype = btf_type_resolve_ptr(btf_vmlinux, member->type, NULL); > @@ -430,10 +431,12 @@ static int bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key, > > tprogs[BPF_TRAMP_FENTRY].progs[0] = prog; > tprogs[BPF_TRAMP_FENTRY].nr_progs = 1; > + flags = st_ops->func_models[i].ret_size > 0 ? > + BPF_TRAMP_F_RET_FENTRY_RET : 0; > err = arch_prepare_bpf_trampoline(NULL, image, > st_map->image + PAGE_SIZE, > - &st_ops->func_models[i], 0, > - tprogs, NULL); > + &st_ops->func_models[i], > + flags, tprogs, NULL); > if (err < 0) > goto reset_unlock; >