From patchwork Wed Feb 1 10:04:25 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christophe Leroy X-Patchwork-Id: 13124011 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 E2A9AC636D3 for ; Wed, 1 Feb 2023 10:05:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231481AbjBAKFL (ORCPT ); Wed, 1 Feb 2023 05:05:11 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44050 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231318AbjBAKFJ (ORCPT ); Wed, 1 Feb 2023 05:05:09 -0500 Received: from pegase2.c-s.fr (pegase2.c-s.fr [93.17.235.10]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A796D611F9; Wed, 1 Feb 2023 02:05:03 -0800 (PST) Received: from localhost (mailhub3.si.c-s.fr [172.26.127.67]) by localhost (Postfix) with ESMTP id 4P6HbJ714zz9sgw; Wed, 1 Feb 2023 11:05:00 +0100 (CET) X-Virus-Scanned: amavisd-new at c-s.fr Received: from pegase2.c-s.fr ([172.26.127.65]) by localhost (pegase2.c-s.fr [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id OPigNB4XDnrD; Wed, 1 Feb 2023 11:05:00 +0100 (CET) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase2.c-s.fr (Postfix) with ESMTP id 4P6HbJ5k4vz9sgT; Wed, 1 Feb 2023 11:05:00 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id AF9228B781; Wed, 1 Feb 2023 11:05:00 +0100 (CET) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id uptZuZdrL9Dx; Wed, 1 Feb 2023 11:05:00 +0100 (CET) Received: from PO20335.IDSI0.si.c-s.fr (unknown [172.25.230.108]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 45B678B77E; Wed, 1 Feb 2023 11:05:00 +0100 (CET) Received: from PO20335.IDSI0.si.c-s.fr (localhost [127.0.0.1]) by PO20335.IDSI0.si.c-s.fr (8.17.1/8.16.1) with ESMTPS id 311A4qaH3908574 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Wed, 1 Feb 2023 11:04:52 +0100 Received: (from chleroy@localhost) by PO20335.IDSI0.si.c-s.fr (8.17.1/8.17.1/Submit) id 311A4p843908571; Wed, 1 Feb 2023 11:04:51 +0100 X-Authentication-Warning: PO20335.IDSI0.si.c-s.fr: chleroy set sender to christophe.leroy@csgroup.eu using -f From: Christophe Leroy To: Michael Ellerman , Nicholas Piggin , "Naveen N. Rao" Cc: Christophe Leroy , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, bpf@vger.kernel.org, Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa Subject: [PATCH v2 3/9] powerpc/bpf/32: Only set a stack frame when necessary Date: Wed, 1 Feb 2023 11:04:25 +0100 Message-Id: <62d7b654a3cfe73d998697cb29bbc5ffd89bfdb1.1675245773.git.christophe.leroy@csgroup.eu> X-Mailer: git-send-email 2.39.1 In-Reply-To: <4fd69ef7945518c3e27f96b95046a5c1468d35bf.1675245773.git.christophe.leroy@csgroup.eu> References: <4fd69ef7945518c3e27f96b95046a5c1468d35bf.1675245773.git.christophe.leroy@csgroup.eu> MIME-Version: 1.0 X-Developer-Signature: v=1; a=ed25519-sha256; t=1675245868; l=2645; s=20211009; h=from:subject:message-id; bh=qHcZ9FGfqBG0re943EgcCn633R4vXJj9AdzNzdKvRmY=; b=waf4d3d8pjTxKhrWc2MzLXSzMxuB3d+K0pFiBLocmR3YPFJLzyBc742CxVqkM+dzHiAGOzo9p6xN I6/+/CZ7CMNBjpOldGDNfGjbb1+OcqyIuQistADinJ7xhYvhcvOu X-Developer-Key: i=christophe.leroy@csgroup.eu; a=ed25519; pk=HIzTzUj91asvincQGOFx6+ZF5AoUuP9GdOtQChs7Mm0= Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net Until now a stack frame was set at all time due to the need to keep tail call counter in the stack. But since commit fa025537f584 ("powerpc/bpf/32: Fix Oops on tail call tests"), the tail call counter is passed via register r4. It is therefore not necessary anymore to have a stack frame for that. Just like PPC64, implement bpf_has_stack_frame() and only sets the frame when needed. The difference with PPC64 is that PPC32 doesn't have a redzone, so the stack is required as soon as non volatile registers are used or when tail call count is set up. Signed-off-by: Christophe Leroy --- arch/powerpc/net/bpf_jit_comp32.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/net/bpf_jit_comp32.c b/arch/powerpc/net/bpf_jit_comp32.c index 4e6caee9c98a..7f54d37bede6 100644 --- a/arch/powerpc/net/bpf_jit_comp32.c +++ b/arch/powerpc/net/bpf_jit_comp32.c @@ -79,6 +79,20 @@ static int bpf_jit_stack_offsetof(struct codegen_context *ctx, int reg) #define SEEN_NVREG_FULL_MASK 0x0003ffff /* Non volatile registers r14-r31 */ #define SEEN_NVREG_TEMP_MASK 0x00001e01 /* BPF_REG_5, BPF_REG_AX, TMP_REG */ +static inline bool bpf_has_stack_frame(struct codegen_context *ctx) +{ + /* + * We only need a stack frame if: + * - we call other functions (kernel helpers), or + * - we use non volatile registers, or + * - we use tail call counter + * - the bpf program uses its stack area + * The latter condition is deduced from the usage of BPF_REG_FP + */ + return ctx->seen & (SEEN_FUNC | SEEN_TAILCALL | SEEN_NVREG_FULL_MASK) || + bpf_is_seen_register(ctx, bpf_to_ppc(BPF_REG_FP)); +} + void bpf_jit_realloc_regs(struct codegen_context *ctx) { unsigned int nvreg_mask; @@ -121,7 +135,8 @@ void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx) #define BPF_TAILCALL_PROLOGUE_SIZE 4 - EMIT(PPC_RAW_STWU(_R1, _R1, -BPF_PPC_STACKFRAME(ctx))); + if (bpf_has_stack_frame(ctx)) + EMIT(PPC_RAW_STWU(_R1, _R1, -BPF_PPC_STACKFRAME(ctx))); if (ctx->seen & SEEN_TAILCALL) EMIT(PPC_RAW_STW(_R4, _R1, bpf_jit_stack_offsetof(ctx, BPF_PPC_TC))); @@ -174,7 +189,8 @@ static void bpf_jit_emit_common_epilogue(u32 *image, struct codegen_context *ctx EMIT(PPC_RAW_LWZ(_R0, _R1, BPF_PPC_STACKFRAME(ctx) + PPC_LR_STKOFF)); /* Tear down our stack frame */ - EMIT(PPC_RAW_ADDI(_R1, _R1, BPF_PPC_STACKFRAME(ctx))); + if (bpf_has_stack_frame(ctx)) + EMIT(PPC_RAW_ADDI(_R1, _R1, BPF_PPC_STACKFRAME(ctx))); if (ctx->seen & SEEN_FUNC) EMIT(PPC_RAW_MTLR(_R0));