From patchwork Sun Aug 28 02:54:48 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yonghong Song X-Patchwork-Id: 12957150 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 56DF8ECAAD1 for ; Sun, 28 Aug 2022 02:55:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231384AbiH1CzA (ORCPT ); Sat, 27 Aug 2022 22:55:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42390 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229493AbiH1Cy7 (ORCPT ); Sat, 27 Aug 2022 22:54:59 -0400 Received: from mx0b-00082601.pphosted.com (mx0b-00082601.pphosted.com [67.231.153.30]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CA3691A066 for ; Sat, 27 Aug 2022 19:54:56 -0700 (PDT) Received: from pps.filterd (m0148460.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.17.1.5/8.17.1.5) with ESMTP id 27S2mgUX028027 for ; Sat, 27 Aug 2022 19:54:55 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : content-type : content-transfer-encoding : mime-version; s=facebook; bh=aqB3dZzYC2Vdj1hM1Bkau3YY2gwUun68jY9QaP6Y+Oo=; b=bAZ7XdmLVl2MSRCHGrnMG8lH1v1G3Eq+mltQNPtb7PkrCX4HDuHjxffcOig5Ha6uwGqZ Of14FkU1PTCcMuSlArI5VTVj8XYz2KWEo0EMlg2z42jidLd6oNXDt2mOGILpWTzw3SXN vUcx5QPMn0SJqGXcnSTJhn86RyvtbkrCxNs= Received: from maileast.thefacebook.com ([163.114.130.16]) by mx0a-00082601.pphosted.com (PPS) with ESMTPS id 3j7gsytu4f-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Sat, 27 Aug 2022 19:54:55 -0700 Received: from twshared0823.18.frc3.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:83::7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Sat, 27 Aug 2022 19:54:54 -0700 Received: by devbig309.ftw3.facebook.com (Postfix, from userid 128203) id E65D8EA747F4; Sat, 27 Aug 2022 19:54:48 -0700 (PDT) From: Yonghong Song To: CC: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Subject: [PATCH bpf-next v3 2/7] bpf: x86: Support in-register struct arguments in trampoline programs Date: Sat, 27 Aug 2022 19:54:48 -0700 Message-ID: <20220828025448.143923-1-yhs@fb.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220828025438.142798-1-yhs@fb.com> References: <20220828025438.142798-1-yhs@fb.com> X-FB-Internal: Safe X-Proofpoint-ORIG-GUID: XOFW8TobFAnczEYoBb9eFVlB4tmS9DE_ X-Proofpoint-GUID: XOFW8TobFAnczEYoBb9eFVlB4tmS9DE_ X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.895,Hydra:6.0.517,FMLib:17.11.122.1 definitions=2022-08-27_10,2022-08-25_01,2022-06-22_01 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net In C, struct value can be passed as a function argument. For small structs, struct value may be passed in one or more registers. For trampoline based bpf programs, This would cause complication since one-to-one mapping between function argument and arch argument register is not valid any more. The latest llvm16 added bpf support to pass by values for struct up to 16 bytes ([1]). This is also true for x86_64 architecture where two registers will hold the struct value if the struct size is >8 and <= 16. This may not be true if one of struct member is 'double' type but in current linux source code we don't have such instance yet, so we assume all >8 && <= 16 struct holds two general purpose argument registers. Also change on-stack nr_args value to the number of registers holding the arguments. This will permit bpf_get_func_arg() helper to get all argument values. [1] https://reviews.llvm.org/D132144 Signed-off-by: Yonghong Song --- arch/x86/net/bpf_jit_comp.c | 68 +++++++++++++++++++++++++++---------- 1 file changed, 51 insertions(+), 17 deletions(-) diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index c1f6c1c51d99..ae89f4143eb4 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -1751,34 +1751,60 @@ st: if (is_imm8(insn->off)) static void save_regs(const struct btf_func_model *m, u8 **prog, int nr_args, int stack_size) { - int i; + int i, j, arg_size, nr_regs; /* Store function arguments to stack. * For a function that accepts two pointers the sequence will be: * mov QWORD PTR [rbp-0x10],rdi * mov QWORD PTR [rbp-0x8],rsi */ - for (i = 0; i < min(nr_args, 6); i++) - emit_stx(prog, bytes_to_bpf_size(m->arg_size[i]), - BPF_REG_FP, - i == 5 ? X86_REG_R9 : BPF_REG_1 + i, - -(stack_size - i * 8)); + for (i = 0, j = 0; i < min(nr_args, 6); i++) { + if (m->arg_flags[i] & BTF_FMODEL_STRUCT_ARG) { + nr_regs = (m->arg_size[i] + 7) / 8; + arg_size = 8; + } else { + nr_regs = 1; + arg_size = m->arg_size[i]; + } + + while (nr_regs) { + emit_stx(prog, bytes_to_bpf_size(arg_size), + BPF_REG_FP, + j == 5 ? X86_REG_R9 : BPF_REG_1 + j, + -(stack_size - j * 8)); + nr_regs--; + j++; + } + } } static void restore_regs(const struct btf_func_model *m, u8 **prog, int nr_args, int stack_size) { - int i; + int i, j, arg_size, nr_regs; /* Restore function arguments from stack. * For a function that accepts two pointers the sequence will be: * EMIT4(0x48, 0x8B, 0x7D, 0xF0); mov rdi,QWORD PTR [rbp-0x10] * EMIT4(0x48, 0x8B, 0x75, 0xF8); mov rsi,QWORD PTR [rbp-0x8] */ - for (i = 0; i < min(nr_args, 6); i++) - emit_ldx(prog, bytes_to_bpf_size(m->arg_size[i]), - i == 5 ? X86_REG_R9 : BPF_REG_1 + i, - BPF_REG_FP, - -(stack_size - i * 8)); + for (i = 0, j = 0; i < min(nr_args, 6); i++) { + if (m->arg_flags[i] & BTF_FMODEL_STRUCT_ARG) { + nr_regs = (m->arg_size[i] + 7) / 8; + arg_size = 8; + } else { + nr_regs = 1; + arg_size = m->arg_size[i]; + } + + while (nr_regs) { + emit_ldx(prog, bytes_to_bpf_size(arg_size), + j == 5 ? X86_REG_R9 : BPF_REG_1 + j, + BPF_REG_FP, + -(stack_size - j * 8)); + nr_regs--; + j++; + } + } } static int invoke_bpf_prog(const struct btf_func_model *m, u8 **pprog, @@ -2015,7 +2041,7 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i struct bpf_tramp_links *tlinks, void *orig_call) { - int ret, i, nr_args = m->nr_args; + int ret, i, nr_args = m->nr_args, extra_nregs = 0; int regs_off, ip_off, args_off, stack_size = nr_args * 8, run_ctx_off; struct bpf_tramp_links *fentry = &tlinks[BPF_TRAMP_FENTRY]; struct bpf_tramp_links *fexit = &tlinks[BPF_TRAMP_FEXIT]; @@ -2028,6 +2054,14 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i if (nr_args > 6) return -ENOTSUPP; + for (i = 0; i < MAX_BPF_FUNC_ARGS; i++) { + if (m->arg_flags[i] & BTF_FMODEL_STRUCT_ARG) + extra_nregs += (m->arg_size[i] + 7) / 8 - 1; + } + if (nr_args + extra_nregs > 6) + return -ENOTSUPP; + stack_size += extra_nregs * 8; + /* Generated trampoline stack layout: * * RBP + 8 [ return address ] @@ -2040,7 +2074,7 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i * [ ... ] * RBP - regs_off [ reg_arg1 ] program's ctx pointer * - * RBP - args_off [ args count ] always + * RBP - args_off [ arg regs count ] always * * RBP - ip_off [ traced function ] BPF_TRAMP_F_IP_ARG flag * @@ -2083,11 +2117,11 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i EMIT4(0x48, 0x83, 0xEC, stack_size); /* sub rsp, stack_size */ EMIT1(0x53); /* push rbx */ - /* Store number of arguments of the traced function: - * mov rax, nr_args + /* Store number of argument registers of the traced function: + * mov rax, nr_args + extra_nregs * mov QWORD PTR [rbp - args_off], rax */ - emit_mov_imm64(&prog, BPF_REG_0, 0, (u32) nr_args); + emit_mov_imm64(&prog, BPF_REG_0, 0, (u32) nr_args + extra_nregs); emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -args_off); if (flags & BPF_TRAMP_F_IP_ARG) {