From nobody Wed Dec 17 00:05:03 2025 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 BA4A2C4167B for ; Fri, 8 Dec 2023 16:35:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1574316AbjLHQfM (ORCPT ); Fri, 8 Dec 2023 11:35:12 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41292 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1574057AbjLHQfD (ORCPT ); Fri, 8 Dec 2023 11:35:03 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 73A1C19AA for ; Fri, 8 Dec 2023 08:35:08 -0800 (PST) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2CBEEC433C8; Fri, 8 Dec 2023 16:35:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1702053308; bh=SUBvtEn9z9UrSU17r7Cw0HAstRv+zJkI6nOLOYxgtBI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=dgZj87RJDMQntv41jgP4YNzanNPs+Fpah5vLvv/Fi7x0xv29OoS4clgN/qIAyR3jV hNHJeCEa/bbQa3tIPnXKAXv1XPy755Z5yFhAqz/ZNGNCeHC60vxB53+qo4cZ5ZDMGt 1bKvP6XKSFo//muVUOZZnkbmDgADqtIdir6Z1wlBqONgp6SxBcA0Fpg4TBCaa7JPoH DyIwjCw1N0hyzBtUCNEkS+BkeEJHcvJ2vMCyeg2HJIFUbmpLMN74veO6ZY9RsKKn+X WnLEVHuFTlAKZL/rOOjuiuX5Vaa7uEQymnLPerK8Spbtr8wV1Ef8GfvngNKvimkVO8 EumXuDYVXZszg== From: Naveen N Rao To: , Cc: Michael Ellerman , Nicholas Piggin , Christophe Leroy , "Aneesh Kumar K.V" , Steven Rostedt , Mark Rutland , Florent Revest , Masami Hiramatsu Subject: [RFC PATCH 2/9] powerpc/ftrace: Unify 32-bit and 64-bit ftrace entry code Date: Fri, 8 Dec 2023 22:00:41 +0530 Message-ID: X-Mailer: git-send-email 2.43.0 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" On 32-bit powerpc, gcc generates a three instruction sequence for function profiling: mflr r0 stw r0, 4(r1) bl _mcount On kernel boot, the call to _mcount() is nop-ed out, to be patched back in when ftrace is actually enabled. The 'stw' instruction therefore is not necessary unless ftrace is enabled. Nop it out during ftrace init. When ftrace is enabled, we want the 'stw' so that stack unwinding works properly. Perform the same within the ftrace handler, similar to 64-bit powerpc. For 64-bit powerpc, early versions of gcc used to emit a three instruction sequence for function profiling (with -mprofile-kernel) with a 'std' instruction to mimic the 'stw' above. Address that scenario also by nop-ing out the 'std' instruction during ftrace init. Signed-off-by: Naveen N Rao --- arch/powerpc/kernel/trace/ftrace.c | 6 ++++-- arch/powerpc/kernel/trace/ftrace_entry.S | 4 ++-- 2 files changed, 6 insertions(+), 4 deletions(-) diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace= /ftrace.c index 82010629cf88..2956196c98ff 100644 --- a/arch/powerpc/kernel/trace/ftrace.c +++ b/arch/powerpc/kernel/trace/ftrace.c @@ -229,13 +229,15 @@ int ftrace_init_nop(struct module *mod, struct dyn_ft= race *rec) /* Expected sequence: 'mflr r0', 'stw r0,4(r1)', 'bl _mcount' */ ret =3D ftrace_validate_inst(ip - 8, ppc_inst(PPC_RAW_MFLR(_R0))); if (!ret) - ret =3D ftrace_validate_inst(ip - 4, ppc_inst(PPC_RAW_STW(_R0, _R1, 4))= ); + ret =3D ftrace_modify_code(ip - 4, ppc_inst(PPC_RAW_STW(_R0, _R1, 4)), + ppc_inst(PPC_RAW_NOP())); } else if (IS_ENABLED(CONFIG_MPROFILE_KERNEL)) { /* Expected sequence: 'mflr r0', ['std r0,16(r1)'], 'bl _mcount' */ ret =3D ftrace_read_inst(ip - 4, &old); if (!ret && !ppc_inst_equal(old, ppc_inst(PPC_RAW_MFLR(_R0)))) { ret =3D ftrace_validate_inst(ip - 8, ppc_inst(PPC_RAW_MFLR(_R0))); - ret |=3D ftrace_validate_inst(ip - 4, ppc_inst(PPC_RAW_STD(_R0, _R1, 16= ))); + ret |=3D ftrace_modify_code(ip - 4, ppc_inst(PPC_RAW_STD(_R0, _R1, 16)), + ppc_inst(PPC_RAW_NOP())); } } else { return -EINVAL; diff --git a/arch/powerpc/kernel/trace/ftrace_entry.S b/arch/powerpc/kernel= /trace/ftrace_entry.S index 40677416d7b2..17d1ed3d0b40 100644 --- a/arch/powerpc/kernel/trace/ftrace_entry.S +++ b/arch/powerpc/kernel/trace/ftrace_entry.S @@ -33,6 +33,8 @@ * and then arrange for the ftrace function to be called. */ .macro ftrace_regs_entry allregs + /* Save the original return address in A's stack frame */ + PPC_STL r0, LRSAVE(r1) /* Create a minimal stack frame for representing B */ PPC_STLU r1, -STACK_FRAME_MIN_SIZE(r1) =20 @@ -44,8 +46,6 @@ SAVE_GPRS(3, 10, r1) =20 #ifdef CONFIG_PPC64 - /* Save the original return address in A's stack frame */ - std r0, LRSAVE+SWITCH_FRAME_SIZE+STACK_FRAME_MIN_SIZE(r1) /* Ok to continue? */ lbz r3, PACA_FTRACE_ENABLED(r13) cmpdi r3, 0 --=20 2.43.0