From nobody Fri Sep 25 08:46:39 2026 Received: from mail-qt1-f180.google.com (mail-qt1-f180.google.com [209.85.160.180]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 88BEE3CFF5A for ; Tue, 15 Sep 2026 02:13:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.160.180 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789438441; cv=none; b=bofTn6BQ0YTg7B4GSINldrhFlZgC3HSZkzVTVYhfpLzXcP4d/tVqaV4DUAaZ23o30HZygCONjMdqnEEXj4Pn1kMZUCPD7i4ML8tWM8XFRZMJQMm3q8bpYS95tgitXcX18/IUzpZE3UbZMTkhOKORncVLp1WsGD6Kh5J1SlaEvAw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789438441; c=relaxed/simple; bh=324LLKjMUj0uq84jIXtS1OvEwpU5ICvJxiUe6G7wYnQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=SafgWDIK5Yk10j8pSUy3HxwClFBShmrUq/gMGxGHO9swHFVb9jJ+cGclUVYjWJ5meLNlosoA5jf62GL4YWLSUedAZ5CYZyyUR1OQ83m4lnzMBjeGG084rNlBdMascHn780hOeTb8QCrctPqbaHLmulqBbyhvXV5bEtKSwF2T654= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=oLuq42af; arc=none smtp.client-ip=209.85.160.180 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="oLuq42af" Received: by mail-qt1-f180.google.com with SMTP id d75a77b69052e-5306d609317so38519501cf.2 for ; Mon, 14 Sep 2026 19:13:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1789438438; x=1790043238; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=kFkEUPsV9vHfYTD+e29tDCYCEDdf/VhB1bccVZ3Vd14=; b=oLuq42afvMfqH95Gqyh+hnhHCbUIxHf/nyjyNyKG4diYxvbB/acdYFq8yCpHk3ixwy 5DkCHAnGSfpL4llOya5qG3pX3XZHzQ9OFUHovmaoP/9PONPNZxfYbmax33DvRgM0UCQ4 ttTv25l9OizJVbtJriOozQD0AdESEyotwQ6UdB2dwG7T8aaUDdSunwiSMGt/0OxRXsxo qh4UqQt1kCQ85J5pxHVL/ateystwP9V0kQAJ/IoGI3Yju/RWBRG5w1WUFTh2bJRzgM2W 6GOZoSIPXiTPoQrwRrYuqKE+RrzWVlxkeglsKe8BxVbpm58T2Z4waKZ3piryYlffQInW Cstg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1789438438; x=1790043238; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to:content-type; bh=kFkEUPsV9vHfYTD+e29tDCYCEDdf/VhB1bccVZ3Vd14=; b=Pnkf9WAuBAxJ1l71bqTOoTce/t09ocDgIMWEQgPDKNP/aJmxU6lKuws7DpwELsTQe7 GLHSjI106tpT4Qo2PmNbJqpy8Yn9cM9f4QiiareGNnjjdtp3geP5bPFAiD9PXHVMMV+A NI+FgTlmDojgxGTjrfNmVzbyKVhaCz0x/aBHK7VRuHgPEYgq534dyz9J6U3z0qwFMvGr 5zlrtxaIs2DzWaYhI7SBEwX2S5O9cJxPulYv+vGYfK9siSZ2IOimmYcDXPmLE14hCgw/ 6N2zyyhYEZbX3h1/y0h6WH2oZmx0kLEoyegBPAAok5MYhKdkAAagxTVYj8gHU2vRUvxT JmgA== X-Forwarded-Encrypted: i=1; AKwUvByTT3v9pWlVaq7eKuKOqfVxAheRGExg/a+9VWPOz78btpWMAEbOQM6kiHJHqOhiB90OyN5Vo9Wj1BYzZUs=@vger.kernel.org X-Gm-Message-State: AFuF++l6PvhTG8POwHn3iyLIJqC8SvjfKuXSrxVe28npwAGK5BcFbawC EMSmx7Sm1A3seWpbDoPlOb/K4XJqLlGv3fTA6N+BBm7D1f/yo8OrlTw/ X-Gm-Gg: AYBFou0CqQHIU/ZjCk0/4Lv7GrQODljQ/fcFH40rXQY/JUs++FhjiF0DY51E1cVOPdM bVOouBPJV9JPmPCYkLvBEQmEQHkEriv0Vi17jN7ij99rkpHMDxYROtmiRy5aod+W19l2ljNfhS9 KupXkXPZhA5JiiosFm6dp1XUO5SiFNoJb2QeHWo3gzjlrSnhR4yJN6hfMGRw8DJ1tEH/wPiFXxw ZfpRwASW9Pu0eI2ll6crd34V/5Lp6QDAftoEkXYlxZqEuwK3sGjZDmE6Uzt8cPI8QIuAuFDFTqI R7PGO/MwsWuze7pUweDtMzVJ35GLH4a5gWy4L02K0DbEr/b2k9z5xHTDEDDDBkZ1YwSZP1lcd6f IgZbz2J615VIkTz/a297Jax0gLsalMLZdWVjeS7vJjVoay3Eycr360IykN+SLv8zwcyU7VIJDja qVUd96ZQwgqmFDAbbA8nRkZuMOYkaNJfoCqpJGwGDXY3pGI2qZeZS/6QC1JadV/r0+rwmfO1lhz yg= X-Received: by 2002:a05:622b:10a:10b0:531:172f:79e8 with SMTP id d75a77b69052e-531172f7e58mr37466341cf.57.1789438438205; Mon, 14 Sep 2026 19:13:58 -0700 (PDT) Received: from Turin ([187.15.143.6]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-9120f47e800sm113147306d6.27.2026.09.14.19.13.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Sep 2026 19:13:57 -0700 (PDT) From: Nicholas Dudar To: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, memxor@gmail.com, udknight@gmail.com, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org Cc: martin.lau@linux.dev, song@kernel.org, yonghong.song@linux.dev, jolsa@kernel.org, emil@etsalapatis.com, ihor.solodrai@linux.dev, hpa@zytor.com, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, visitorckw@gmail.com Subject: [PATCH bpf-next 1/5] bpf, x86: Add support for BPF_MOVSX in the i386 JIT Date: Mon, 14 Sep 2026 22:13:34 -0400 Message-ID: <20260915021338.1520964-2-main.kalliope@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260915021338.1520964-1-main.kalliope@gmail.com> References: <20260915021338.1520964-1-main.kalliope@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The i386 JIT lowers register BPF_MOVSX as an ordinary move because do_jit() does not inspect insn->off. The generated code therefore copies the source instead of sign-extending the selected low bits. Context-access conversion can also introduce MOVSX while lowering signed loads, so rejecting BPF_MEMSX does not protect those paths. Stage the source low word in EAX and use the native byte and word sign-extension instructions. Derive the high word from the sign bit for ALU64 and retain verifier-managed zero extension for ALU32. Assisted-by: Codex:gpt-6 Signed-off-by: Nicholas Dudar --- arch/x86/net/bpf_jit_comp32.c | 51 +++++++++++++++++++++++++++++++++++ 1 file changed, 51 insertions(+) diff --git a/arch/x86/net/bpf_jit_comp32.c b/arch/x86/net/bpf_jit_comp32.c index 852baf2e4db4..9cbeabac4f27 100644 --- a/arch/x86/net/bpf_jit_comp32.c +++ b/arch/x86/net/bpf_jit_comp32.c @@ -266,6 +266,51 @@ static inline void emit_ia32_mov_r64(const bool is64, = const u8 dst[], emit_ia32_mov_i(dst_hi, 0, dstk, pprog); } =20 +/* dst =3D sign_extend(src, insn->off) */ +static inline void emit_ia32_movsx_r64(const struct bpf_insn *insn, u8 **p= prog, + const struct bpf_prog_aux *aux) +{ + const u8 *dst =3D bpf2ia32[insn->dst_reg]; + const u8 *src =3D bpf2ia32[insn->src_reg]; + bool dstk =3D insn->dst_reg !=3D BPF_REG_AX; + bool sstk =3D insn->src_reg !=3D BPF_REG_AX; + bool is64 =3D BPF_CLASS(insn->code) =3D=3D BPF_ALU64; + u8 *prog =3D *pprog; + int cnt =3D 0; + + if (sstk) + /* mov eax,dword ptr [ebp+off] */ + EMIT3(0x8B, add_2reg(0x40, IA32_EBP, IA32_EAX), + STACK_VAR(src_lo)); + else + /* mov eax,src_lo */ + EMIT2(0x89, add_2reg(0xC0, IA32_EAX, src_lo)); + + switch (insn->off) { + case 8: + /* movsx eax,al */ + EMIT3(0x0F, 0xBE, 0xC0); + break; + case 16: + /* movsx eax,ax */ + EMIT3(0x0F, 0xBF, 0xC0); + break; + case 32: + /* EAX already holds the low word; CDQ supplies the high word. */ + break; + } + + emit_ia32_mov_r(dst_lo, IA32_EAX, dstk, false, &prog); + if (is64) { + EMIT1(0x99); /* cdq */ + emit_ia32_mov_r(dst_hi, IA32_EDX, dstk, false, &prog); + } else if (!aux->verifier_zext) { + emit_ia32_mov_i(dst_hi, 0, dstk, &prog); + } + + *pprog =3D prog; +} + /* Sign extended move */ static inline void emit_ia32_mov_i64(const bool is64, const u8 dst[], const u32 val, bool dstk, u8 **pprog) @@ -1697,6 +1742,12 @@ static int do_jit(struct bpf_prog *bpf_prog, int *ad= drs, u8 *image, emit_ia32_mov_i(dst_hi, 0, dstk, &prog); break; } + if (insn->off =3D=3D 8 || insn->off =3D=3D 16 || + (is64 && insn->off =3D=3D 32)) { + emit_ia32_movsx_r64(insn, &prog, + bpf_prog->aux); + break; + } emit_ia32_mov_r64(is64, dst, src, dstk, sstk, &prog, bpf_prog->aux); break; From nobody Fri Sep 25 08:46:39 2026 Received: from mail-qv2-f12.google.com (mail-qv2-f12.google.com [74.125.230.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 27FE23CF1FF for ; Tue, 15 Sep 2026 02:14:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.230.140 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789438453; cv=none; b=L9yiZO8SX2yoIDhFCHKJCKCQL6KTt4Yg1oEXQp+dJF2YvBtl4MBeP0QHDCrnpNGsitWritXnL2yv6w2uov5qCvvni8xXjD0SL9eSrur9x5JNIGjboxHG8dB7DMs6CCOA2oaPCaWtUSk2oaZAuK3jRkYnSjHY0M9sJnJL7q8jxnQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789438453; c=relaxed/simple; bh=ZDux8IWKTR+nMiDaW8QlWTXplfoJrXXpLbQBsYiak+k=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=LrMAADDRaj1vx26yqgMF0moJcRg3PeOmvX4f2guA/0Dl6BfJMx7bkfuPykuJPVqn+cmMjLpMYLiQEfEGaxlEqyweZ01dI7uGpjgKCOrgmb/sHsvJAyab0/U0WHuFKsA5rzpF/YWOBN/BpDC3hcCKtb4oohI97KiuTKytSnYMx+M= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=MiOLVFo9; arc=none smtp.client-ip=74.125.230.140 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="MiOLVFo9" Received: by mail-qv2-f12.google.com with SMTP id 6a1803df08f44-9121fe38733so27115996d6.2 for ; Mon, 14 Sep 2026 19:14:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1789438450; x=1790043250; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=HuFmciVjVBaKzPczWLuz+SOkqXuntlpMYqQwvPavVgE=; b=MiOLVFo9jPrdk6TvdKflUMp7YIGRImk7AJMAqH+E5IWo7E9qPFjfMd6YdE9ytre+yB Vx2uP+Pel/KV9Lf5A4jMZHBJXbFjLySiG1wINdkxbyonHp7H1wwwVYM+2Oq0Jhev79Yb CjFNa+Jvlmd6l6uHZCgo3k4K9hOxttXRoMyYgBhz0uCtbXF+ky4xWLVWr2vpNzSp972b sQJCRTS3+6sxyf8ESAzayjrnugyyzr/qZTg3NaTul5VY2VqeMGqxoHhOGwklZGi8JfoM z8wG3UUfEOAM0d3QKsgmrnudZuVD4ig+V+PvD5j2nH3EdHGyoFzDIYWg78mDeQulfEv4 jZfQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1789438450; x=1790043250; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to:content-type; bh=HuFmciVjVBaKzPczWLuz+SOkqXuntlpMYqQwvPavVgE=; b=HpvRSix2+K/2kpvfUCnuINtVh64eEie6N2tIT/FKTLBTmn4E4RtrS+ULbpJR33jU6h ZXU/bj3qsb6BdJo7cVd0l+PgJ8nRKFJfA1pg7cJZvw/GNOGs08bax4rnewvv3P32t6tw /DQva/VshWlSjpqKphsuKbWAKTX9jHbC9n9tIK7gdBtyOo3sj1C000Z25xVSJVKuecry 9H15ARRT//Khe3m9s6O9C8V/bb4f84WkSVeT8rS2HpYGrWcjpOHA8WDBRsvH8O82lqSb xNMh0ahtyyImT+l0DuUy30M5Sp27/dUOlUrS51npHVdguOYGQSD1MhGOb0KkKV5AEL0S 8xmA== X-Forwarded-Encrypted: i=1; AKwUvBwtsmGSpYYxZJDDxdXnDgdyXezfp+tY1aOMnPIzpb8Wl/km514ApzPq3pz4C03NB7dI4+mTgHYZ1mUkDrI=@vger.kernel.org X-Gm-Message-State: AFuF++lS1Tg4L/e3Se7StIC5jL9s4eN/fw6GAYsZqe2uzNZ0ZpL3ioJc Byc05/KZLWEYqeIZiMPkYQkjk8sx+1nsp+aPb43k5n/gRhh8Dxl2Oo2x X-Gm-Gg: AYBFou2UMcA5Zn0nfJCdnmHe3yM5gqnXFEIeaxilgnMEsoRjSn8bjyI4DjoWD+SVpSd fIRbZUC1pGqJb6yz3dmdkhYA9TWiCz9wQdCs+BJrmEbwOLZP9txRYEvxneZJHMEwirXLC/YD1VX tOzo9VcJ0fu6sFgkhGwPETBe+hoB5eTQPm/eFoDAc1sCROxmAq1Vn4BNe5JDWOF3aOrL1wx387C OCg7hN6pDrCIQCOl75/435lYAgTA7DnLcpXBDQiw17p21nuqgou8N3CtYdLTanNJeM1IHrEPBYO Thuu4ywxmteCbXk7Zc+3G5mbDRoFMk31ChhB/h6Y5J09V+GeUaNmxeGHuXjSWZMDsV6NBd1dos1 oWQvybh9+q2+NpJuCyTpZoct40GpAqg0ZFPklfcsermLDxzMUd/PoM3Nf00HFPbM4y+nfJp9pG9 U3inm6esPGXP5eERiBmuH+32jDYYmW/3vrX34Cx2u8L+vphkmyUDcfTvh9hzQc26uD X-Received: by 2002:a05:6214:4289:b0:910:63b6:fc60 with SMTP id 6a1803df08f44-9122e4ec8f2mr115365286d6.11.1789438449826; Mon, 14 Sep 2026 19:14:09 -0700 (PDT) Received: from Turin ([187.15.143.6]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-9120f47e800sm113147306d6.27.2026.09.14.19.14.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Sep 2026 19:14:09 -0700 (PDT) From: Nicholas Dudar To: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, memxor@gmail.com, udknight@gmail.com, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org Cc: martin.lau@linux.dev, song@kernel.org, yonghong.song@linux.dev, jolsa@kernel.org, emil@etsalapatis.com, ihor.solodrai@linux.dev, hpa@zytor.com, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, visitorckw@gmail.com Subject: [PATCH bpf-next 2/5] bpf, x86: Extract the i386 JIT load emitter Date: Mon, 14 Sep 2026 22:13:35 -0400 Message-ID: <20260915021338.1520964-3-main.kalliope@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260915021338.1520964-1-main.kalliope@gmail.com> References: <20260915021338.1520964-1-main.kalliope@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Move ordinary LDX lowering into an instruction-owned helper. Keep address staging, displacement encoding and register-pair completion together, including verifier-managed zero extension for narrow loads. Use the helper for the existing BPF_MEM cases before adding signed loads. This separates the code movement from the MEMSX instruction handling. The emitted instructions are preserved. Assisted-by: Codex:gpt-6 Signed-off-by: Nicholas Dudar --- arch/x86/net/bpf_jit_comp32.c | 148 +++++++++++++++++++--------------- 1 file changed, 84 insertions(+), 64 deletions(-) diff --git a/arch/x86/net/bpf_jit_comp32.c b/arch/x86/net/bpf_jit_comp32.c index 9cbeabac4f27..6839c233cb73 100644 --- a/arch/x86/net/bpf_jit_comp32.c +++ b/arch/x86/net/bpf_jit_comp32.c @@ -1214,6 +1214,89 @@ static inline void emit_ia32_mul_i64(const u8 dst[],= const u32 val, *pprog =3D prog; } =20 +static void emit_ia32_ldx(const struct bpf_insn *insn, u8 **pprog, + const struct bpf_prog_aux *aux) +{ + const u8 *dst =3D bpf2ia32[insn->dst_reg]; + const u8 *src =3D bpf2ia32[insn->src_reg]; + bool dstk =3D insn->dst_reg !=3D BPF_REG_AX; + bool sstk =3D insn->src_reg !=3D BPF_REG_AX; + u8 *prog =3D *pprog; + int cnt =3D 0; + + /* Stage the address in EAX; dst may alias src. */ + if (sstk) + /* mov eax,dword ptr [ebp+off] */ + EMIT3(0x8B, add_2reg(0x40, IA32_EBP, IA32_EAX), + STACK_VAR(src_lo)); + else + /* mov eax,src_lo */ + EMIT2(0x8B, add_2reg(0xC0, src_lo, IA32_EAX)); + + switch (BPF_SIZE(insn->code)) { + case BPF_B: + /* movzx edx,byte ptr [eax+off] */ + EMIT2(0x0F, 0xB6); + break; + case BPF_H: + /* movzx edx,word ptr [eax+off] */ + EMIT2(0x0F, 0xB7); + break; + case BPF_W: + case BPF_DW: + /* mov edx,dword ptr [eax+off] */ + EMIT1(0x8B); + break; + } + + if (is_imm8(insn->off)) + EMIT2(add_2reg(0x40, IA32_EAX, IA32_EDX), insn->off); + else + EMIT1_off32(add_2reg(0x80, IA32_EAX, IA32_EDX), insn->off); + + if (dstk) + /* mov dword ptr [ebp+off],edx */ + EMIT3(0x89, add_2reg(0x40, IA32_EBP, IA32_EDX), + STACK_VAR(dst_lo)); + else + /* mov dst_lo,edx */ + EMIT2(0x89, add_2reg(0xC0, dst_lo, IA32_EDX)); + + switch (BPF_SIZE(insn->code)) { + case BPF_B: + case BPF_H: + case BPF_W: + if (aux->verifier_zext) + break; + if (dstk) { + /* mov dword ptr [ebp+off],0 */ + EMIT3(0xC7, add_1reg(0x40, IA32_EBP), + STACK_VAR(dst_hi)); + EMIT(0x0, 4); + } else { + /* xor dst_hi,dst_hi */ + EMIT2(0x33, add_2reg(0xC0, dst_hi, dst_hi)); + } + break; + case BPF_DW: + /* mov edx,dword ptr [eax+off+4] */ + EMIT2_off32(0x8B, add_2reg(0x80, IA32_EAX, IA32_EDX), + insn->off + 4); + if (dstk) + /* mov dword ptr [ebp+off],edx */ + EMIT3(0x89, add_2reg(0x40, IA32_EBP, IA32_EDX), + STACK_VAR(dst_hi)); + else + /* mov dst_hi,edx */ + EMIT2(0x89, add_2reg(0xC0, dst_hi, IA32_EDX)); + break; + default: + break; + } + + *pprog =3D prog; +} + static int bpf_size_to_x86_bytes(int bpf_size) { if (bpf_size =3D=3D BPF_W) @@ -2065,70 +2148,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *ad= drs, u8 *image, case BPF_LDX | BPF_MEM | BPF_H: case BPF_LDX | BPF_MEM | BPF_W: case BPF_LDX | BPF_MEM | BPF_DW: - if (sstk) - /* mov eax,dword ptr [ebp+off] */ - EMIT3(0x8B, add_2reg(0x40, IA32_EBP, IA32_EAX), - STACK_VAR(src_lo)); - else - /* mov eax,dword ptr [ebp+off] */ - EMIT2(0x8B, add_2reg(0xC0, src_lo, IA32_EAX)); - - switch (BPF_SIZE(code)) { - case BPF_B: - EMIT2(0x0F, 0xB6); break; - case BPF_H: - EMIT2(0x0F, 0xB7); break; - case BPF_W: - case BPF_DW: - EMIT(0x8B, 1); break; - } - - if (is_imm8(insn->off)) - EMIT2(add_2reg(0x40, IA32_EAX, IA32_EDX), - insn->off); - else - EMIT1_off32(add_2reg(0x80, IA32_EAX, IA32_EDX), - insn->off); - - if (dstk) - /* mov dword ptr [ebp+off],edx */ - EMIT3(0x89, add_2reg(0x40, IA32_EBP, IA32_EDX), - STACK_VAR(dst_lo)); - else - /* mov dst_lo,edx */ - EMIT2(0x89, add_2reg(0xC0, dst_lo, IA32_EDX)); - switch (BPF_SIZE(code)) { - case BPF_B: - case BPF_H: - case BPF_W: - if (bpf_prog->aux->verifier_zext) - break; - if (dstk) { - EMIT3(0xC7, add_1reg(0x40, IA32_EBP), - STACK_VAR(dst_hi)); - EMIT(0x0, 4); - } else { - /* xor dst_hi,dst_hi */ - EMIT2(0x33, - add_2reg(0xC0, dst_hi, dst_hi)); - } - break; - case BPF_DW: - EMIT2_off32(0x8B, - add_2reg(0x80, IA32_EAX, IA32_EDX), - insn->off + 4); - if (dstk) - EMIT3(0x89, - add_2reg(0x40, IA32_EBP, - IA32_EDX), - STACK_VAR(dst_hi)); - else - EMIT2(0x89, - add_2reg(0xC0, dst_hi, IA32_EDX)); - break; - default: - break; - } + emit_ia32_ldx(insn, &prog, bpf_prog->aux); break; /* call */ case BPF_JMP | BPF_CALL: From nobody Fri Sep 25 08:46:39 2026 Received: from mail-qv2-f12.google.com (mail-qv2-f12.google.com [74.125.230.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8071A3CF680 for ; Tue, 15 Sep 2026 02:14:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.230.140 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789438456; cv=none; b=SLgpB+JsTiNSHcrDSbTnuTl10HXUCdhDpMwm47gHhsStjMnRup4nkoUEEp4BFRLQrsB5sODOVS574CRLcsi4kBn/TGABM5+pGqoDjxyWPxWJYXjZWUCoVgZJaYZIoEaRn8VgZPPYRunYDmR/6cvbc6ulBvGQjV1oSbJiGIgcEA8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789438456; c=relaxed/simple; bh=TdqvwGyPTSdjX8dTecFU8bgsVtp8D+qt1YBdhE4JhsI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Z0h2AnBtFQ5wem1hTCghirRar4c+SyqsP++MAGumKL8uX3drK6S4zOWWD+m3I9qcFxdlNx5OUjRhqncOcYptcafgiNxzWpxPOnh3ajmwRUD4G5hDzJZJ0jQOVDG2Y1BtFbhZweVDA5J5BXbeihuWor8w1wYFF+wjep/bbkVWdN4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=iOXQJcnO; arc=none smtp.client-ip=74.125.230.140 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="iOXQJcnO" Received: by mail-qv2-f12.google.com with SMTP id 6a1803df08f44-91064d2d54fso34020746d6.0 for ; Mon, 14 Sep 2026 19:14:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1789438453; x=1790043253; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=U2Vegq3Ok1ZpjxSq9TiA3YgOUyAjEHN8flyn+dvT4jU=; b=iOXQJcnOj3ZYKBpYqoSVup3V6JBEb2k7+QNojlfaQBdzh81vzoxqjkHMRgYwjIxBBO zXF/PB4t6i3qR6RIm2ZelkkhktJ+oVB/JSdgH87rkUXhj/G1M1feiTBRiPAImDlEkVpA DmGrICof+9XlCgot3vai/rOZyvU1pMpMFeUSMNXwyMN+xRnGg5EYblfUoh0Zujxuas+z oGbYHqpj8lTXxDAoTuoCjNr32kKRY8O3tIVkr+uPt1cmeVQkX+TWPUakBQZrgi+mq18Z vAAM+Wkk+MCT+oPmA8bNIWb8NlDhzft7p66UCGbCSw9q8HaKVNrQ15OOYVYYqTCwyglE k//A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1789438453; x=1790043253; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to:content-type; bh=U2Vegq3Ok1ZpjxSq9TiA3YgOUyAjEHN8flyn+dvT4jU=; b=xz45syO+Z1HScG2m60+v1kXq9ioOnXMXk68qdeBrCoxo+OLPjVpbuZeBGbAsmhlUqL 6NQbRpobKvFyQTTDqtKoYLuNRcKmVkuXCnU8uFmlWILhWJ+1tV8S5N+cpi7xJg07vBaW 7Q0lIRslTO/WKkuJFnkmnUx1KiAx9Fu9ENI2gvlh3Sc83XTKfQTO5VPDUwqk6BjWMgrs mqRMHXiyVF6Vag0e8IkBeutiFOOcd57ZD+Gntm1iFMFPVs6RS12JHKsT2SN8l6rtmDYY 7ECMqSx+Y5rjef1sOen9myz6LGmvWcI1mUIRvXkyQfj8Adpjmb/O8o2tn3dDKfcowc+y PFEQ== X-Forwarded-Encrypted: i=1; AKwUvBwPmyc3Z78NXOPXVkQrAGHvWnobV8pXYJeZX2xwtBG/pZhj6hNK4DLf3iAyGdxN1EuE1L8iTzh7j3VSe6U=@vger.kernel.org X-Gm-Message-State: AFuF++mHOxYcIHxWJ7dF7wPpqRYX+GNWpqf19FM9SkwHXmGuNRn2DPt6 R2x52ZZD96DIIGETBLCtP880lNvK0U9C1z7eDeL00yHee/GBrmsDPyXq X-Gm-Gg: AYBFou1t6SN82eu4TgjRHmNu9dqFcCoTYB3FjsJ+sWtAwwOmdX1tlMEYGV+P2+NXWc8 aqxOqXnQavOGlK2IeV3R0/9NAxkyvCi7o5Tz9RA+SQSXHeOw7xstdazkGR67DTnE/ofFiip9wls RVQ9H5noVQjxmNGMfBbaPdpGyPlMRGcrNvM99KBGlzPYqqcuAOFoXr2DR/5JcGxJ1UJ8JYYCsoV 9WaMKTpN8OVb5x2Fe8205gWFFxMFWvCNAqIQkB/0xQRTZvvlOgJeSk1Zksdynanl+SiyhUapNPs rtFonenGt3MjJlJaLO0VVQ0bFKXAfVyVvhlxx2dxIe9K5FEaQqtxtS/dqWsx7bwWjKyZJedJy0P LHx6FlcmZkD4OI7kfprJSk/nxKz2JYDT10oztMu3HLDS/o4xXdunIcJmDK22IFVgxA4sllHYgw7 0iyvBB8llXm/dMgISnEdOOP4NEM4EeXci2lYjfr46uh7rJQSJVFCZ7+JbfkPEd/8q5 X-Received: by 2002:a05:6214:5f11:b0:912:bd1:49f5 with SMTP id 6a1803df08f44-9122e4e2154mr80192546d6.10.1789438453123; Mon, 14 Sep 2026 19:14:13 -0700 (PDT) Received: from Turin ([187.15.143.6]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-9120f47e800sm113147306d6.27.2026.09.14.19.14.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Sep 2026 19:14:12 -0700 (PDT) From: Nicholas Dudar To: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, memxor@gmail.com, udknight@gmail.com, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org Cc: martin.lau@linux.dev, song@kernel.org, yonghong.song@linux.dev, jolsa@kernel.org, emil@etsalapatis.com, ihor.solodrai@linux.dev, hpa@zytor.com, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, visitorckw@gmail.com Subject: [PATCH bpf-next 3/5] bpf, x86: Add BPF_MEMSX support to the i386 JIT Date: Mon, 14 Sep 2026 22:13:36 -0400 Message-ID: <20260915021338.1520964-4-main.kalliope@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260915021338.1520964-1-main.kalliope@gmail.com> References: <20260915021338.1520964-1-main.kalliope@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The i386 JIT rejects BPF_MEMSX byte, halfword and word loads. Use signed byte and halfword loads, then extend the loaded low word's sign into the upper word for all three MEMSX widths. MEMSX defines a 64-bit result, so complete both halves regardless of verifier_zext. Ordinary loads retain their existing zero-extension handling. Assisted-by: Codex:gpt-6 Signed-off-by: Nicholas Dudar --- arch/x86/net/bpf_jit_comp32.c | 71 ++++++++++++++++++++++------------- 1 file changed, 44 insertions(+), 27 deletions(-) diff --git a/arch/x86/net/bpf_jit_comp32.c b/arch/x86/net/bpf_jit_comp32.c index 6839c233cb73..bbe48b15850f 100644 --- a/arch/x86/net/bpf_jit_comp32.c +++ b/arch/x86/net/bpf_jit_comp32.c @@ -1221,6 +1221,7 @@ static void emit_ia32_ldx(const struct bpf_insn *insn= , u8 **pprog, const u8 *src =3D bpf2ia32[insn->src_reg]; bool dstk =3D insn->dst_reg !=3D BPF_REG_AX; bool sstk =3D insn->src_reg !=3D BPF_REG_AX; + bool sign =3D BPF_MODE(insn->code) =3D=3D BPF_MEMSX; u8 *prog =3D *pprog; int cnt =3D 0; =20 @@ -1235,12 +1236,12 @@ static void emit_ia32_ldx(const struct bpf_insn *in= sn, u8 **pprog, =20 switch (BPF_SIZE(insn->code)) { case BPF_B: - /* movzx edx,byte ptr [eax+off] */ - EMIT2(0x0F, 0xB6); + /* movsx/movzx edx,byte ptr [eax+off] */ + EMIT2(0x0F, sign ? 0xBE : 0xB6); break; case BPF_H: - /* movzx edx,word ptr [eax+off] */ - EMIT2(0x0F, 0xB7); + /* movsx/movzx edx,word ptr [eax+off] */ + EMIT2(0x0F, sign ? 0xBF : 0xB7); break; case BPF_W: case BPF_DW: @@ -1262,26 +1263,10 @@ static void emit_ia32_ldx(const struct bpf_insn *in= sn, u8 **pprog, /* mov dst_lo,edx */ EMIT2(0x89, add_2reg(0xC0, dst_lo, IA32_EDX)); =20 - switch (BPF_SIZE(insn->code)) { - case BPF_B: - case BPF_H: - case BPF_W: - if (aux->verifier_zext) - break; - if (dstk) { - /* mov dword ptr [ebp+off],0 */ - EMIT3(0xC7, add_1reg(0x40, IA32_EBP), - STACK_VAR(dst_hi)); - EMIT(0x0, 4); - } else { - /* xor dst_hi,dst_hi */ - EMIT2(0x33, add_2reg(0xC0, dst_hi, dst_hi)); - } - break; - case BPF_DW: - /* mov edx,dword ptr [eax+off+4] */ - EMIT2_off32(0x8B, add_2reg(0x80, IA32_EAX, IA32_EDX), - insn->off + 4); + /* MEMSX defines both halves, regardless of verifier_zext. */ + if (sign) { + /* sar edx,31 */ + EMIT3(0xC1, add_1reg(0xF8, IA32_EDX), 31); if (dstk) /* mov dword ptr [ebp+off],edx */ EMIT3(0x89, add_2reg(0x40, IA32_EBP, IA32_EDX), @@ -1289,9 +1274,38 @@ static void emit_ia32_ldx(const struct bpf_insn *ins= n, u8 **pprog, else /* mov dst_hi,edx */ EMIT2(0x89, add_2reg(0xC0, dst_hi, IA32_EDX)); - break; - default: - break; + } else { + switch (BPF_SIZE(insn->code)) { + case BPF_B: + case BPF_H: + case BPF_W: + if (aux->verifier_zext) + break; + if (dstk) { + /* mov dword ptr [ebp+off],0 */ + EMIT3(0xC7, add_1reg(0x40, IA32_EBP), + STACK_VAR(dst_hi)); + EMIT(0x0, 4); + } else { + /* xor dst_hi,dst_hi */ + EMIT2(0x33, add_2reg(0xC0, dst_hi, dst_hi)); + } + break; + case BPF_DW: + /* mov edx,dword ptr [eax+off+4] */ + EMIT2_off32(0x8B, add_2reg(0x80, IA32_EAX, IA32_EDX), + insn->off + 4); + if (dstk) + /* mov dword ptr [ebp+off],edx */ + EMIT3(0x89, add_2reg(0x40, IA32_EBP, IA32_EDX), + STACK_VAR(dst_hi)); + else + /* mov dst_hi,edx */ + EMIT2(0x89, add_2reg(0xC0, dst_hi, IA32_EDX)); + break; + default: + break; + } } =20 *pprog =3D prog; @@ -2148,6 +2162,9 @@ static int do_jit(struct bpf_prog *bpf_prog, int *add= rs, u8 *image, case BPF_LDX | BPF_MEM | BPF_H: case BPF_LDX | BPF_MEM | BPF_W: case BPF_LDX | BPF_MEM | BPF_DW: + case BPF_LDX | BPF_MEMSX | BPF_B: + case BPF_LDX | BPF_MEMSX | BPF_H: + case BPF_LDX | BPF_MEMSX | BPF_W: emit_ia32_ldx(insn, &prog, bpf_prog->aux); break; /* call */ From nobody Fri Sep 25 08:46:39 2026 Received: from mail-qk2-f13.google.com (mail-qk2-f13.google.com [74.125.230.205]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0DCCF3D16E6 for ; Tue, 15 Sep 2026 02:14:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.230.205 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789438459; cv=none; b=m3VSlwKdqri8K6Wn3aW0f+vV+r3e+bEG0D3jNf4i8WZCNf8M+3j96NEMnWyaVSXT0+1SltSYXS2R66y14Ru2swdIw+6cyHGkkfU/dkzRCvdS6NBtteeI9v+10wA+nGc1HSSLQCJmjmnICjdQqYlU17jXC49YRNimDQ27M/3cugc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789438459; c=relaxed/simple; bh=OMt5HhDiTDnWRUkq/1fc/fNuEDADUxzcUrOtLkkmOMU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=tLc0R6IZrPTySOzUt/ThqLeIOkI+miewL5qPxNSaOO847yIwhL7RVdL2WQWYMrg8oYkj/HqJp+uFtdCX1oB+xt773W89M+sckvysX3cVEfZRM/IUwvEOINo+cjULQbyaSCOzKzqxcnreCmZ/ig9nkzTG7+i5QUhFYHJ+4Tynnec= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=IgHA3j3a; arc=none smtp.client-ip=74.125.230.205 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="IgHA3j3a" Received: by mail-qk2-f13.google.com with SMTP id d75a77b69052e-530301ff353so27975891cf.2 for ; Mon, 14 Sep 2026 19:14:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1789438457; x=1790043257; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=kaYOd8zTfYAMpBFvUyf33rw4Yl3HKUzIa2TDVLlOUCY=; b=IgHA3j3aC/IdmxXs2gFnyLB2qjwzIPYYhyKypILSKuEjYjnYDr9FXyAgjVbsw84Nci yNPrOFKoJI4hKLbKL20qFHf3HOVq6O1QXdwdUAxI0uFtOOfaBaGMontckPVt7evL0opE s3B6hi9Ap7P4vmNcrBN1uON5glCqfBSZ5xudNpoc3nSj25YjxGzoAnKX0OChFOzgtNsL ceuK2GpEqUm/CbfWFUreVt3qH82NrtXODHTOPADR6xGq36MvX3bi3WzsBLWlcLsTNSUW uDxV6qeFjp4ZoxEmeS5JldNidpFTqjOCIahhlC0XH0OxJFA9Mgl/KWk2a8J/VLMFHFNG 0lvQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1789438457; x=1790043257; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to:content-type; bh=kaYOd8zTfYAMpBFvUyf33rw4Yl3HKUzIa2TDVLlOUCY=; b=WYQOTTwyyjbizqDtrkBcZ9edddSxx9JSr1V3WDaunHcPheXWcKHsFegMz9fuzfBlYv +s44lRSrB6jpcn08UwdRvJprA11H10hB/3J8RmiimJoJ2wCFXB5bZKHCQAux1uPtNYea OWBapnAejVuTqHh9qAj+Bxachc9nI6kowu3WnooJ9LipCjFuj8ifzohPi5r/9znyAawU 2/h5fmDp3RTElxNunIV3Y/pRaIZ+MlmF+7fvhLZstOLnVu6vbubGRrbtSHU79Z7QxbXc Aq7zN7T9zA/GdLCJZMZdIMno+PUnh3asnCtYuKMCoPLwRYDMZtcOcPTcgafnyQwg0Mf7 sgpA== X-Forwarded-Encrypted: i=1; AKwUvBwnBo4xJRMfLD7B8pevG2vvJpwoY6j0if9yOxopzUGxAcyGkCFoldtlaj8xS4UHwogJ3G56w5fEMIyUnm4=@vger.kernel.org X-Gm-Message-State: AFuF++l6FuodJqIKRRtthikxvo73rFHdwhV0a9kWpdAmIdXNbSQby+Ub CI93b0+FJc7p7nb77nBi+WEYKmPDJ7H3HhLWEgn8Zd2z558lz/jcJuQJ X-Gm-Gg: AYBFou3zwMt/wXeSytY2l/5FsS8wi5HgbNR5VdaXTWbrp5EUy+UYge4gFjaj60W698M QJStDdze9MAkjGk7MSj/flC22+8hVx/4oCxzgSTUUQaUI/iCpjm+mz9dSvY6GFzjC1YqInb1nVJ /KP8auT8mwSHL/HTbktes7u1EAgJ7vtS5ICa1UBNiWVKbyFMrkOE5m843PJpSjC/1l/IcrdRWie UGVhL4k0O3BGdAjjuXMNB+zC5QTZKLL3iyPzvEjah/18UkhXQmLiW4VK5RSrYM8z9m+ZfifX/iu TFZMxpIvIcHyQAg0M+N+/UvZ5AjR6whFcT2tReDqW8HhbPCiWAvXBQWSEosa6l8+cYYzVpkwKh0 EMZRICfbI0pEeAgQKeU4Zv/LghRNDXfBIgyqCLpRB3qoD3gK7c/H2nZgxfEOB8xEUrvZbz5HPMu TpupRabjlNHCuqFh/wqLUriLN1l3pyjrmZFaaApFyyTHqal6Xok1Z9Gh7b5LTIqtLH X-Received: by 2002:ac8:5908:0:b0:52f:bfb3:ed3d with SMTP id d75a77b69052e-5310cf40d5fmr77338011cf.25.1789438456707; Mon, 14 Sep 2026 19:14:16 -0700 (PDT) Received: from Turin ([187.15.143.6]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-9120f47e800sm113147306d6.27.2026.09.14.19.14.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Sep 2026 19:14:16 -0700 (PDT) From: Nicholas Dudar To: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, memxor@gmail.com, udknight@gmail.com, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org Cc: martin.lau@linux.dev, song@kernel.org, yonghong.song@linux.dev, jolsa@kernel.org, emil@etsalapatis.com, ihor.solodrai@linux.dev, hpa@zytor.com, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, visitorckw@gmail.com Subject: [PATCH bpf-next 4/5] bpf, x86: Add BPF_JMP32 | BPF_JA support to the i386 JIT Date: Mon, 14 Sep 2026 22:13:37 -0400 Message-ID: <20260915021338.1520964-5-main.kalliope@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260915021338.1520964-1-main.kalliope@gmail.com> References: <20260915021338.1520964-1-main.kalliope@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The i386 JIT rejects BPF_JMP32 | BPF_JA, which encodes its signed jump displacement in imm rather than the 16-bit off field. Select the displacement by instruction class and reuse the existing unconditional jump lowering, including its self-jump and no-op handling. The shared unconditional-jump path handles instruction zero separately: its start is the prologue boundary, which has no preceding entry in the instruction-end address map. Assisted-by: Codex:gpt-6 Signed-off-by: Nicholas Dudar --- arch/x86/net/bpf_jit_comp32.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/arch/x86/net/bpf_jit_comp32.c b/arch/x86/net/bpf_jit_comp32.c index bbe48b15850f..2d8a3a961e91 100644 --- a/arch/x86/net/bpf_jit_comp32.c +++ b/arch/x86/net/bpf_jit_comp32.c @@ -1821,6 +1821,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *add= rs, u8 *image, const u8 *src =3D bpf2ia32[insn->src_reg]; const u8 *r0 =3D bpf2ia32[BPF_REG_0]; s64 jmp_offset; + s32 ja_off; u8 jmp_cond; int ilen; u8 *func; @@ -2522,7 +2523,9 @@ emit_cond_jmp_signed: /* Check the condition for low = 32-bit comparison */ break; } case BPF_JMP | BPF_JA: - if (insn->off =3D=3D -1) + case BPF_JMP32 | BPF_JA: + ja_off =3D BPF_CLASS(code) =3D=3D BPF_JMP32 ? imm32 : insn->off; + if (ja_off =3D=3D -1) /* -1 jmp instructions will always jump * backwards two bytes. Explicitly handling * this case avoids wasting too many passes @@ -2530,8 +2533,10 @@ emit_cond_jmp_signed: /* Check the condition for low= 32-bit comparison */ * dead code. */ jmp_offset =3D -2; + else if (i + ja_off =3D=3D -1) + jmp_offset =3D PROLOGUE_SIZE - addrs[i]; else - jmp_offset =3D addrs[i + insn->off] - addrs[i]; + jmp_offset =3D addrs[i + ja_off] - addrs[i]; =20 if (!jmp_offset) /* Optimize out nop jumps */ From nobody Fri Sep 25 08:46:39 2026 Received: from mail-qk2-f13.google.com (mail-qk2-f13.google.com [74.125.230.205]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DD05C3D1CC3 for ; Tue, 15 Sep 2026 02:14:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.230.205 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789438464; cv=none; b=LcaxRSlQXuroqDb63Vn6Li9CwHTVGKsr8wpPnOfWpojLCJ4nJ3UkRX1mojlTsIjGCYafrJ/CM657AYqmZjkqilgnHnv+b9Ke2Qd1l5yuCij/on3f6n2q/PZo3xpr6DKrT2to0zwzPhdALLGUUnPNbtXTGvHT2JAw40d/a0SKtpI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789438464; c=relaxed/simple; bh=/1WQcwweXawSG/8olW4NCuVNsiyfQve4wAhgNUxL7p0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=SOVcVpoplX0mDOzxtsZ+A9nCNmICCFDD5bOC7qd6x35w7wA+L4CzuoiVYeC8HtExMDMP4+FGKYH7tQKQx9Mysc0nobJC7L+DEHL8pz4ZG9HlQVzTe0sJ/7h76WMw2fpUUpkrdGj7tG6DrJqinyV0whVE8yD0LsFLtYJb8SEdIgo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=UGP5zmmg; arc=none smtp.client-ip=74.125.230.205 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="UGP5zmmg" Received: by mail-qk2-f13.google.com with SMTP id af79cd13be357-939109f067fso342451785a.2 for ; Mon, 14 Sep 2026 19:14:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1789438461; x=1790043261; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=7XHejARW/GsAN6R6sQQvVB3X/bf7ngCNqKrc+swjfGM=; b=UGP5zmmg2vbhxLI+oOd3kxxhAQOgN8h7nuBtmyQxHqvGSeN6wRICO2m6+VccV3Wiod 6Wq+gfpDjk6iNfAmP6d1O1JmFTKIvmUbOucmkmNNSXyqQqkFHaFG96ZCMpyJYnxgcjGY Kl0rqv2H06RT5pmEdky4/eUgm9AV1/uLfBNypQEYoU/Cz1YRUTuwL2pHhT6HqFKCAQdz tPx0fCTMeZ7SfYkDpSm3+vKpTcKkglE6u7WzcGeZFQxmVkkNp5aUsvrmYXiMmogjRQ3I jfujHplAyzkbrwQmn1PIwcd/0HUW9VKZlzVxI5QrpbcImfmXylU0qgS1f21dhyP3eT38 hmag== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1789438461; x=1790043261; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to:content-type; bh=7XHejARW/GsAN6R6sQQvVB3X/bf7ngCNqKrc+swjfGM=; b=o6oyQeJt5/0UleEtry03bfogOeXI+HFLlbL0HUuWqYswr/SFdeAI9DqNsvLXNsepgu 7XhofrRyxtI87NzkAcUGBe/bmZ2HDT759aPlfTu42o4ww6n5fL7130U6I3VlnFhYDAZJ C6nXRMmMCe3fZTtXOhS1TzunaQeOcNNHORWRP3p3Col06BMf5FOa75IhnCN+vBNF0Vbg ApEvdhY4QWXp4xsCPaQ6bynkJeIVNRfxNNq5/8+YVYWnRhcX1AzDXYyw3HiZc0H7UopJ gNgkIL1yqjFh1FMdOVigJkurDCZVzHyaRCVu0PROvk5sW2+4AnkKDH5DL5h3nQDuk92E jgSg== X-Forwarded-Encrypted: i=1; AKwUvBwqOW3R/kuPkcr+iOVWDYauKHsnmtHxRGymu0uZ96h3UNHRaczcyV3wQ4GPoiWE6UH/v9F4KbU6xk6myQY=@vger.kernel.org X-Gm-Message-State: AFuF++mXIfgJQo5c6Y72V826Mv4YkaYXU5QCg+7hlruLuI2qljP7pfll nsAvqWQmvsD6W3IRCyjFAVPCQYecE030y4VBlKGa0W4SBLWJSJSSL0w3 X-Gm-Gg: AYBFou2/cnpjvaI3aYwFF+2KzP6hBPGf1EiVSdPliSDbXlnAmlDiFh83pIU21gMtFr7 wLIHpM/77pRJmceH8pudz+Ciot9ZXwLxtvGXuZZdmwND8g/M4WqdpHrucnh0QNYZQUxC7rGiHQT S7mGWa5ADPx9lIApdgXN0DcHDiep6d5gKhnerQK8GFt4ZxAXrR4ZePn2V/X2929dlKmt0FYksZa 4JMyykxuokrEJdKZ+R6apj/9lzJiPuejEnJ27v6k+7Fl1T9r87xVlbZY/3EeWUVKPe0gPugomFD 1jATcedVprFxLFJeQ6QBOjMk64cVPJX/y2IrqvGj8nrGza4j3XaeXNxTBMuFZYabNeM/p94pqIX +H+l2RA5Fuwst5zcfqRWU0oce5bdK/tIQgpCZf+Ws/ZOnGsf2TjnuYvA4weeINrQlLQwXxP6pvV 0flXFMOaNb71CgaPmt2g0700WIYrsXKR7LDN13WAYhSYlmJtAL3hbNZKXr5uCRMES3 X-Received: by 2002:a05:620a:6018:b0:92e:5d44:73fc with SMTP id af79cd13be357-93a297ac480mr768891385a.12.1789438461227; Mon, 14 Sep 2026 19:14:21 -0700 (PDT) Received: from Turin ([187.15.143.6]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-9120f47e800sm113147306d6.27.2026.09.14.19.14.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Sep 2026 19:14:20 -0700 (PDT) From: Nicholas Dudar To: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, memxor@gmail.com, udknight@gmail.com, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org Cc: martin.lau@linux.dev, song@kernel.org, yonghong.song@linux.dev, jolsa@kernel.org, emil@etsalapatis.com, ihor.solodrai@linux.dev, hpa@zytor.com, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, visitorckw@gmail.com Subject: [PATCH bpf-next 5/5] bpf, x86: Add unconditional byte swap to the i386 JIT Date: Mon, 14 Sep 2026 22:13:38 -0400 Message-ID: <20260915021338.1520964-6-main.kalliope@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260915021338.1520964-1-main.kalliope@gmail.com> References: <20260915021338.1520964-1-main.kalliope@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The i386 JIT rejects unconditional BPF byte-swap instructions, which use BPF_ALU64 | BPF_END. Route them through the existing big-endian conversion emitter. On little-endian i386, it provides the same 16-, 32- and 64-bit byte swaps. The verifier treats sub-64-bit BPF_END results as 32-bit definitions and inserts zero extension where the upper word is used. The emitter clears that word itself when verifier_zext is disabled. Assisted-by: Codex:gpt-6 Signed-off-by: Nicholas Dudar --- arch/x86/net/bpf_jit_comp32.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/x86/net/bpf_jit_comp32.c b/arch/x86/net/bpf_jit_comp32.c index 2d8a3a961e91..bdba05b72ef3 100644 --- a/arch/x86/net/bpf_jit_comp32.c +++ b/arch/x86/net/bpf_jit_comp32.c @@ -2037,6 +2037,8 @@ static int do_jit(struct bpf_prog *bpf_prog, int *add= rs, u8 *image, break; /* dst =3D htobe(dst) */ case BPF_ALU | BPF_END | BPF_FROM_BE: + /* dst =3D bswap(dst) */ + case BPF_ALU64 | BPF_END | BPF_FROM_LE: emit_ia32_to_be_r64(dst, imm32, dstk, &prog, bpf_prog->aux); break;