From patchwork Wed Oct 4 12:07:06 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?b?QmrDtnJuIFTDtnBlbA==?= X-Patchwork-Id: 13408671 X-Patchwork-Delegate: bpf@iogearbox.net 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 809CC13AC5; Wed, 4 Oct 2023 12:07:24 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EE09AC433C9; Wed, 4 Oct 2023 12:07:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1696421244; bh=vLvgsGAj3vc8B6/nSYNfFLo6uk+g4NpV7dEmI8AKTYI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ffk7vBFT5mbKfpS4JsRj1/srW+OQBeawmaCbwedd64L5PBIXa35ukJio0aGa/79fP XDBl5Dqtggjo+cBwBIOgZTuARLyykM12k507R6ubzMvE42nQ2mkhwyn5J80OENEIO8 m3Ag+25W74eAEFvJu1mfdI0GdG/B/l7fx9eOkhl+fRhEy9EzutvfDB7IuH3+cAM2Dp rUGeixzlVrVfIeeL3wZ6TSW0xUq9zLGPiBBeXGSRM+tE98wA3fqllIR+Q+IQHDCZ7A tCqaAqP3sb47Cf8hd462KfH4XTV8ZZxs1LSp6O2MSpCWgVNURx7xWbhuHNyFOqRwej CJSmc1nrCsyhQ== From: =?utf-8?b?QmrDtnJuIFTDtnBlbA==?= To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , bpf@vger.kernel.org, netdev@vger.kernel.org, Pu Lehui Cc: =?utf-8?b?QmrDtnJuIFTDtnBlbA==?= , linux-kernel@vger.kernel.org, Luke Nelson , Xi Wang , linux-riscv@lists.infradead.org Subject: [PATCH bpf 2/2] riscv, bpf: Track both a0 (RISC-V ABI) and a5 (BPF) return values Date: Wed, 4 Oct 2023 14:07:06 +0200 Message-Id: <20231004120706.52848-3-bjorn@kernel.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20231004120706.52848-1-bjorn@kernel.org> References: <20231004120706.52848-1-bjorn@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net From: Björn Töpel The RISC-V BPF uses a5 for BPF return values, which are zero-extended, whereas the RISC-V ABI uses a0 which is sign-extended. In other words, a5 and a0 can differ, and are used in different context. The BPF trampoline are used for both BPF programs, and regular kernel functions. Make sure that the RISC-V BPF trampoline saves, and restores both a0 and a5. Fixes: 49b5e77ae3e2 ("riscv, bpf: Add bpf trampoline support for RV64") Signed-off-by: Björn Töpel --- arch/riscv/net/bpf_jit_comp64.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c index de4c9957d223..8581693e62d3 100644 --- a/arch/riscv/net/bpf_jit_comp64.c +++ b/arch/riscv/net/bpf_jit_comp64.c @@ -759,8 +759,10 @@ static int invoke_bpf_prog(struct bpf_tramp_link *l, int args_off, int retval_of if (ret) return ret; - if (save_ret) - emit_sd(RV_REG_FP, -retval_off, regmap[BPF_REG_0], ctx); + if (save_ret) { + emit_sd(RV_REG_FP, -retval_off, RV_REG_A0, ctx); + emit_sd(RV_REG_FP, -(retval_off - 8), regmap[BPF_REG_0], ctx); + } /* update branch with beqz */ if (ctx->insns) { @@ -853,7 +855,7 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, save_ret = flags & (BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_RET_FENTRY_RET); if (save_ret) { - stack_size += 8; + stack_size += 16; /* Save both A5 (BPF R0) and A0 */ retval_off = stack_size; } @@ -957,6 +959,7 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, if (ret) goto out; emit_sd(RV_REG_FP, -retval_off, RV_REG_A0, ctx); + emit_sd(RV_REG_FP, -(retval_off - 8), regmap[BPF_REG_0], ctx); im->ip_after_call = ctx->insns + ctx->ninsns; /* 2 nops reserved for auipc+jalr pair */ emit(rv_nop(), ctx); @@ -988,8 +991,10 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, if (flags & BPF_TRAMP_F_RESTORE_REGS) restore_args(nregs, args_off, ctx); - if (save_ret) + if (save_ret) { emit_ld(RV_REG_A0, -retval_off, RV_REG_FP, ctx); + emit_ld(regmap[BPF_REG_0], -(retval_off - 8), RV_REG_FP, ctx); + } emit_ld(RV_REG_S1, -sreg_off, RV_REG_FP, ctx);