From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 A13E535959 for ; Sat, 9 Aug 2025 20:48:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754772525; cv=none; b=DgBaJ8qoOD+PlH99GXu2cjU/f4yb530Gglmn1PYOlGSJXLj67bH5KcptqCh5VYIDmQU6jufENRdGHDFvmVsLxIQW0iZ86QnH8afVVqUjmqPnZBPtaY8mt7sLLbV6NQwELi9FDQCPD7iwKqTp8QmdixIVhEs2Ien0/UVFUvOfmH0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754772525; c=relaxed/simple; bh=x++fkya3y4iz+zfBmAFQzoNDYSYedNeRFDUi4KfNSiQ=; h=From:To:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=INP3fDMqgrZS+7pg5rVta3Ry1Yl/QXgbovpxh4Ppok2Wgvn5GM4zWgpkeGeRFSvR+3Xo/n35CLhFAftwUlaKU+c6oG1g8gioUmf2qSZXzo5MLVoNyMT6G8NecSa8FH6zAUPDwWj520zS5M/89N7ESEQdQCQ0GWxyUpB0wTN2/AM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=mi62tTWK; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="mi62tTWK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C760BC4CEE7; Sat, 9 Aug 2025 20:48:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1754772525; bh=x++fkya3y4iz+zfBmAFQzoNDYSYedNeRFDUi4KfNSiQ=; h=From:To:Subject:Date:In-Reply-To:References:From; b=mi62tTWKiN/8U14rUF0L5JXkdeV+5kaZMxkF4tDiIbBJM3wMI9ibtOQecNOYnVw3p 2pgcDS4tc7Y/uN/0bu0Ao88pou00viAQxzAMwwm6dmCHN02qtHEsLbAX8JwhZItcuy evZ+SteTn90xAxLg27gu8IzIJ5NzdVgDDH16+ssnKSSGpW9tXEPqemIxMWBOan3eNl F99oqzHhJQDH9AYRbF1XnOg/eXWF2LpCHs2N0frI4q55ZTPeepEmzL4T1JKmlBdKJo dSKg8IoZYdQ5jvPBmAaFNjqChQ1tD2eqbSxnDBXD+emDUW1j9x9w81YQRZjuUfOvDn pTyACQYfodn+g== From: Puranjay Mohan To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Puranjay Mohan , Xu Kuohai , Catalin Marinas , Will Deacon , Mykola Lysenko , Kumar Kartikeya Dwivedi , bpf@vger.kernel.org Subject: [PATCH bpf-next v2 1/2] bpf, arm64: Add JIT support for timed may_goto Date: Sat, 9 Aug 2025 20:48:30 +0000 Message-ID: <20250809204833.44803-2-puranjay@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20250809204833.44803-1-puranjay@kernel.org> References: <20250809204833.44803-1-puranjay@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit When verifier sees a timed may_goto instruction, it emits a call to arch_bpf_timed_may_goto() with a stack offset in BPF_REG_AX (arm64 r9) and expects a count value to be returned in the same register. The verifier doesn't save or restore any registers before emitting this call. arch_bpf_timed_may_goto() should act as a trampoline to call bpf_check_timed_may_goto() with AAPCS64 calling convention. To support this custom calling convention, implement arch_bpf_timed_may_goto() in assembly and make sure BPF caller saved registers are saved and restored, call bpf_check_timed_may_goto with arm64 calling convention where first argument and return value both are in x0, then put the result back into BPF_REG_AX before returning. Signed-off-by: Puranjay Mohan --- arch/arm64/net/Makefile | 2 +- arch/arm64/net/bpf_jit_comp.c | 13 +++++++++- arch/arm64/net/bpf_timed_may_goto.S | 40 +++++++++++++++++++++++++++++ 3 files changed, 53 insertions(+), 2 deletions(-) create mode 100644 arch/arm64/net/bpf_timed_may_goto.S diff --git a/arch/arm64/net/Makefile b/arch/arm64/net/Makefile index 5c540efb7d9b9..3ae382bfca879 100644 --- a/arch/arm64/net/Makefile +++ b/arch/arm64/net/Makefile @@ -2,4 +2,4 @@ # # ARM64 networking code # -obj-$(CONFIG_BPF_JIT) += bpf_jit_comp.o +obj-$(CONFIG_BPF_JIT) += bpf_jit_comp.o bpf_timed_may_goto.o diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index 52ffe115a8c47..a98b8132479a7 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -1558,7 +1558,13 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, if (ret < 0) return ret; emit_call(func_addr, ctx); - emit(A64_MOV(1, r0, A64_R(0)), ctx); + /* + * Call to arch_bpf_timed_may_goto() is emitted by the + * verifier and called with custom calling convention with + * first argument and return value in BPF_REG_AX (x9). + */ + if (func_addr != (u64)arch_bpf_timed_may_goto) + emit(A64_MOV(1, r0, A64_R(0)), ctx); break; } /* tail call */ @@ -3038,6 +3044,11 @@ bool bpf_jit_bypass_spec_v4(void) return true; } +bool bpf_jit_supports_timed_may_goto(void) +{ + return true; +} + bool bpf_jit_inlines_helper_call(s32 imm) { switch (imm) { diff --git a/arch/arm64/net/bpf_timed_may_goto.S b/arch/arm64/net/bpf_timed_may_goto.S new file mode 100644 index 0000000000000..894cfcd7b2416 --- /dev/null +++ b/arch/arm64/net/bpf_timed_may_goto.S @@ -0,0 +1,40 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* Copyright (c) 2025 Puranjay Mohan */ + +#include + +SYM_FUNC_START(arch_bpf_timed_may_goto) + /* Allocate stack space and emit frame record */ + stp x29, x30, [sp, #-64]! + mov x29, sp + + /* Save BPF registers R0 - R5 (x7, x0-x4)*/ + stp x7, x0, [sp, #16] + stp x1, x2, [sp, #32] + stp x3, x4, [sp, #48] + + /* + * Stack depth was passed in BPF_REG_AX (x9), add it to the BPF_FP + * (x25) to get the pointer to count and timestamp and pass it as the + * first argument in x0. + * + * Before generating the call to arch_bpf_timed_may_goto, the verifier + * generates a load instruction using FP, i.e. REG_AX = *(u64 *)(FP - + * stack_off_cnt), so BPF_REG_FP (x25) is always set up by the arm64 + * jit in this case. + */ + add x0, x9, x25 + bl bpf_check_timed_may_goto + /* BPF_REG_AX(x9) will be stored into count, so move return value to it. */ + mov x9, x0 + + /* Restore BPF registers R0 - R5 (x7, x0-x4) */ + ldp x7, x0, [sp, #16] + ldp x1, x2, [sp, #32] + ldp x3, x4, [sp, #48] + + /* Restore FP and LR */ + ldp x29, x30, [sp], #64 + + ret +SYM_FUNC_END(arch_bpf_timed_may_goto) -- 2.47.3