From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-188.mta1.migadu.com (out-188.mta1.migadu.com [95.215.58.188]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9D9BE271471 for ; Tue, 9 Jun 2026 04:15:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.188 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780978549; cv=none; b=A5z2bcQoCMyusSyMcsvesSwjdKXVpACQEK1iDAABeHIpoR5RbMMRoKBDihWDNV7rANT5sWP9EnL2P9EXLpMIg9gpa9N3P/JGBxlOf8Q/g28wvUm4uw1hr+QG3eJvmkdEi8kdlUFhQinyluOpDPo5YpL8tsIfjGbFW5xIdY22JkY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780978549; c=relaxed/simple; bh=dx7gFPht/W9l9YvdNWrRjXh3WMPbekq1t0fZlRS7OsI=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=reHbbPwaWijY8Mw6Y/J6YLchH5WbO96FVg26Nzy9czZCP3/bRGJhdPvVHJrDeWZ5dKos+yianMuZs0SqmcuEAINWoIshkwFqt8m6QiIA0yFvDsC4uqd36UxJCItrMFXpq36deowYWtSilNRIwtmfNlzjaaJAC0vILjRFIGWbAmY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=wA1yVL3I; arc=none smtp.client-ip=95.215.58.188 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="wA1yVL3I" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1780978545; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=E9K8DKQzuZY5lkKWGM48eNIzslFzSc/uOU/tK45gZds=; b=wA1yVL3IBn/vFFV+TZzzySp5wd839U2zorkWa78WxvpHMqQn3mPH4cArsvkkRP5y5mByoB zPB0ArtKJzrdERucUWstCPqEN791d5OMGUYLbrgQsnMMDEDYquQuKrbmO91y+5bfBFXIyx ERb9HTwSnoovnldwM0ZEP5n88lM0gyU= From: George Guo To: Huacai Chen , Tiezhu Yang , Hengqi Chen Cc: WANG Xuerui , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Kumar Kartikeya Dwivedi , Song Liu , Yonghong Song , Jiri Olsa , loongarch@lists.linux.dev, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, George Guo Subject: [PATCH v1 2/2] LoongArch: BPF: Add timed may_goto support Date: Tue, 9 Jun 2026 12:14:07 +0800 Message-Id: <20260609041407.122384-3-dongtai.guo@linux.dev> In-Reply-To: <20260609041407.122384-1-dongtai.guo@linux.dev> References: <20260609041407.122384-1-dongtai.guo@linux.dev> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT From: George Guo Implement arch_bpf_timed_may_goto() and advertise it through bpf_jit_supports_timed_may_goto() so the verifier lowers may_goto into the timed variant: instead of a fixed iteration counter, the loop is bounded by a wall-clock timeout maintained in a per-loop stack slot. arch_bpf_timed_may_goto() is called with a custom calling convention. The verifier passes the stack offset of the count/timestamp pair in BPF_REG_AX ($t0) and expects the updated count back in the same register, so the stub adds the offset to BPF_REG_FP ($s4), calls bpf_check_timed_may_goto(), and moves the result back into $t0 while preserving the BPF caller-saved registers R0 - R5. The JIT call path is updated to skip the usual 'BPF_REG_0 = C return value' move for this helper since its result is delivered in BPF_REG_AX instead. Signed-off-by: George Guo --- arch/loongarch/net/Makefile | 2 +- arch/loongarch/net/bpf_jit.c | 13 ++++++- arch/loongarch/net/bpf_timed_may_goto.S | 47 +++++++++++++++++++++++++ 3 files changed, 60 insertions(+), 2 deletions(-) create mode 100644 arch/loongarch/net/bpf_timed_may_goto.S diff --git a/arch/loongarch/net/Makefile b/arch/loongarch/net/Makefile index 1ec12a0c324a..8d9ddb48f9ea 100644 --- a/arch/loongarch/net/Makefile +++ b/arch/loongarch/net/Makefile @@ -4,4 +4,4 @@ # # Copyright (C) 2022 Loongson Technology Corporation Limited # -obj-$(CONFIG_BPF_JIT) += bpf_jit.o +obj-$(CONFIG_BPF_JIT) += bpf_jit.o bpf_timed_may_goto.o diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c index 20d5bf792108..794c0c37fa9c 100644 --- a/arch/loongarch/net/bpf_jit.c +++ b/arch/loongarch/net/bpf_jit.c @@ -1185,7 +1185,13 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, bool ext move_addr(ctx, t1, func_addr); emit_insn(ctx, jirl, LOONGARCH_GPR_RA, t1, 0); - if (insn->src_reg != BPF_PSEUDO_CALL) + /* + * Call to arch_bpf_timed_may_goto() uses a custom calling + * convention with the argument and return value in BPF_REG_AX, + * so skip moving the C return value into BPF_REG_0. + */ + if (insn->src_reg != BPF_PSEUDO_CALL && + func_addr != (u64)arch_bpf_timed_may_goto) move_reg(ctx, regmap[BPF_REG_0], LOONGARCH_GPR_A0); break; @@ -2376,6 +2382,11 @@ bool bpf_jit_supports_percpu_insn(void) return true; } +bool bpf_jit_supports_timed_may_goto(void) +{ + return true; +} + /* Indicate the JIT backend supports mixing bpf2bpf and tailcalls. */ bool bpf_jit_supports_subprog_tailcalls(void) { diff --git a/arch/loongarch/net/bpf_timed_may_goto.S b/arch/loongarch/net/bpf_timed_may_goto.S new file mode 100644 index 000000000000..aa86250a9c65 --- /dev/null +++ b/arch/loongarch/net/bpf_timed_may_goto.S @@ -0,0 +1,47 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Author: George Guo + * Copyright (C) 2026 KylinSoft Corporation. + */ + +#include +#include +#include +#include + +SYM_FUNC_START(arch_bpf_timed_may_goto) + addi.d sp, sp, -64 + st.d ra, sp, 0 + + /* Save BPF registers R0 - R5 (a5, a0 - a4) */ + st.d a5, sp, 8 + st.d a0, sp, 16 + st.d a1, sp, 24 + st.d a2, sp, 32 + st.d a3, sp, 40 + st.d a4, sp, 48 + + /* + * BPF_REG_AX (t0) holds the offset passed in by the verifier; add it + * to BPF_REG_FP (s4) to get the pointer to the count and timestamp, + * then pass it as the first argument in a0. + * + * The verifier emits a load using FP right before this call, so + * BPF_REG_FP (s4) is always set up by the JIT in this case. + */ + add.d a0, t0, s4 + bl bpf_check_timed_may_goto + /* BPF_REG_AX (t0) will be stored into count, so move the return value to it. */ + move t0, a0 + + ld.d ra, sp, 0 + ld.d a5, sp, 8 + ld.d a0, sp, 16 + ld.d a1, sp, 24 + ld.d a2, sp, 32 + ld.d a3, sp, 40 + ld.d a4, sp, 48 + addi.d sp, sp, 64 + + jr ra +SYM_FUNC_END(arch_bpf_timed_may_goto) -- 2.25.1