From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, NICE_REPLY_A,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C88FAC433E1 for ; Tue, 14 Jul 2020 11:38:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9F1F62220C for ; Tue, 14 Jul 2020 11:38:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594726685; bh=kUD21ULp1F6LxK9iRvXydVm0jMPaqgfdFZqqqqj45AA=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=BTEa4wN318u4TK8X4QTb40msGqlW2db8QHC0jEyaEyxGWARaQpO4vfxOQVTP0X2gr risFKRYdeLVb/OKCupkbIEhqPtUWfNwwUzzdZwp5dZ/dfbKcPk8rn0jWzksilcQDMH 6CW6Lu7lfe0GKdAq3G5lONsAgkT9GsWTq1ZA5W+c= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727932AbgGNLiE (ORCPT ); Tue, 14 Jul 2020 07:38:04 -0400 Received: from mail.kernel.org ([198.145.29.99]:52604 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725905AbgGNLiD (ORCPT ); Tue, 14 Jul 2020 07:38:03 -0400 Received: from devnote2 (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2FCAE22201; Tue, 14 Jul 2020 11:37:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594726682; bh=kUD21ULp1F6LxK9iRvXydVm0jMPaqgfdFZqqqqj45AA=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=hXvHMXDhFllsXLpP26SE2A0JEWT4xoE5vZovA9jiqsYSlOJ/jsakD7FwkEJ6vfzRL E+VNZjokxgr9tUDX/N373fRRAKOlSy35KikdpyR3rRemHs8gz1wK4zUTkM6SnudxZ1 o7BscwhdydZ64k5EkUtIbPhZ06595wyiw4Z9scig= Date: Tue, 14 Jul 2020 20:37:57 +0900 From: Masami Hiramatsu To: guoren@kernel.org Cc: palmerdabbelt@google.com, paul.walmsley@sifive.com, oleg@redhat.com, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, anup@brainfault.org, linux-csky@vger.kernel.org, greentime.hu@sifive.com, zong.li@sifive.com, me@packi.ch, bjorn.topel@gmail.com, Guo Ren , Pekka Enberg Subject: Re: [PATCH v3 6/7] riscv: Add KPROBES_ON_FTRACE supported Message-Id: <20200714203757.512ce7fb5fa61a88b1dbb2f3@kernel.org> In-Reply-To: <1594683562-68149-7-git-send-email-guoren@kernel.org> References: <1594683562-68149-1-git-send-email-guoren@kernel.org> <1594683562-68149-7-git-send-email-guoren@kernel.org> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 13 Jul 2020 23:39:21 +0000 guoren@kernel.org wrote: > From: Guo Ren > > This patch adds support for kprobes on ftrace call sites to avoids > much of the overhead with regular kprobes. Try it with simple > steps: > > 1. Get _do_fork ftrace call site. > Dump of assembler code for function _do_fork: > 0xffffffe00020af64 <+0>: addi sp,sp,-128 > 0xffffffe00020af66 <+2>: sd s0,112(sp) > 0xffffffe00020af68 <+4>: sd ra,120(sp) > 0xffffffe00020af6a <+6>: addi s0,sp,128 > 0xffffffe00020af6c <+8>: sd s1,104(sp) > 0xffffffe00020af6e <+10>: sd s2,96(sp) > 0xffffffe00020af70 <+12>: sd s3,88(sp) > 0xffffffe00020af72 <+14>: sd s4,80(sp) > 0xffffffe00020af74 <+16>: sd s5,72(sp) > 0xffffffe00020af76 <+18>: sd s6,64(sp) > 0xffffffe00020af78 <+20>: sd s7,56(sp) > 0xffffffe00020af7a <+22>: mv s4,a0 > 0xffffffe00020af7c <+24>: mv a0,ra > 0xffffffe00020af7e <+26>: nop <<<<<<<< here! > 0xffffffe00020af82 <+30>: nop > 0xffffffe00020af86 <+34>: ld s3,0(s4) > > 2. Set _do_fork+26 as the kprobe. > echo 'p:myprobe _do_fork+26 dfd=%a0 filename=%a1 flags=%a2 mode=+4($stack)' > /sys/kernel/debug/tracing/kprobe_events > echo 1 > /sys/kernel/debug/tracing/events/kprobes/enable > cat /sys/kernel/debug/tracing/trace > tracer: nop > > entries-in-buffer/entries-written: 3/3 #P:1 > > _-----=> irqs-off > / _----=> need-resched > | / _---=> hardirq/softirq > || / _--=> preempt-depth > ||| / delay > TASK-PID CPU# |||| TIMESTAMP FUNCTION > | | | |||| | | > sh-87 [000] .... 551.557031: myprobe: (_do_fork+0x1a/0x2e6) dfd=0xffffffe00020af7e filename=0xffffffe00020b34e flags=0xffffffe00101e7c0 mode=0x20af86ffffffe0 > > cat /sys/kernel/debug/kprobes/list > ffffffe00020af7e k _do_fork+0x1a [FTRACE] > ^^^^^^ Hmm, this seems fentry is not supported on RISC-V yet. But anyway, it will be useful for users (if they can find the offset). Reviewed-by: Masami Hiramatsu Thank you, > > Signed-off-by: Guo Ren > Cc: Masami Hiramatsu > Cc: Palmer Dabbelt > Cc: Paul Walmsley > Cc: Björn Töpel > Cc: Zong Li > Cc: Pekka Enberg > --- > arch/riscv/Kconfig | 1 + > arch/riscv/kernel/probes/Makefile | 1 + > arch/riscv/kernel/probes/ftrace.c | 52 +++++++++++++++++++++++++++++++++++++++ > 3 files changed, 54 insertions(+) > create mode 100644 arch/riscv/kernel/probes/ftrace.c > > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig > index a41b785..0e9f5eb 100644 > --- a/arch/riscv/Kconfig > +++ b/arch/riscv/Kconfig > @@ -60,6 +60,7 @@ config RISCV > select HAVE_FUTEX_CMPXCHG if FUTEX > select HAVE_GENERIC_VDSO if MMU && 64BIT > select HAVE_KPROBES > + select HAVE_KPROBES_ON_FTRACE > select HAVE_KRETPROBES > select HAVE_PCI > select HAVE_PERF_EVENTS > diff --git a/arch/riscv/kernel/probes/Makefile b/arch/riscv/kernel/probes/Makefile > index cb62991..7f0840d 100644 > --- a/arch/riscv/kernel/probes/Makefile > +++ b/arch/riscv/kernel/probes/Makefile > @@ -1,5 +1,6 @@ > # SPDX-License-Identifier: GPL-2.0 > obj-$(CONFIG_KPROBES) += kprobes.o decode-insn.o simulate-insn.o > obj-$(CONFIG_KPROBES) += kprobes_trampoline.o > +obj-$(CONFIG_KPROBES_ON_FTRACE) += ftrace.o > obj-$(CONFIG_UPROBES) += uprobes.o decode-insn.o simulate-insn.o > CFLAGS_REMOVE_simulate-insn.o = $(CC_FLAGS_FTRACE) > diff --git a/arch/riscv/kernel/probes/ftrace.c b/arch/riscv/kernel/probes/ftrace.c > new file mode 100644 > index 00000000..e0fe58a > --- /dev/null > +++ b/arch/riscv/kernel/probes/ftrace.c > @@ -0,0 +1,52 @@ > +// SPDX-License-Identifier: GPL-2.0 > + > +#include > + > +/* Ftrace callback handler for kprobes -- called under preepmt disabed */ > +void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, > + struct ftrace_ops *ops, struct pt_regs *regs) > +{ > + struct kprobe *p; > + struct kprobe_ctlblk *kcb; > + > + p = get_kprobe((kprobe_opcode_t *)ip); > + if (unlikely(!p) || kprobe_disabled(p)) > + return; > + > + kcb = get_kprobe_ctlblk(); > + if (kprobe_running()) { > + kprobes_inc_nmissed_count(p); > + } else { > + unsigned long orig_ip = instruction_pointer(regs); > + instruction_pointer_set(regs, ip); > + > + __this_cpu_write(current_kprobe, p); > + kcb->kprobe_status = KPROBE_HIT_ACTIVE; > + if (!p->pre_handler || !p->pre_handler(p, regs)) { > + /* > + * Emulate singlestep (and also recover regs->pc) > + * as if there is a nop > + */ > + instruction_pointer_set(regs, > + (unsigned long)p->addr + MCOUNT_INSN_SIZE); > + if (unlikely(p->post_handler)) { > + kcb->kprobe_status = KPROBE_HIT_SSDONE; > + p->post_handler(p, regs, 0); > + } > + instruction_pointer_set(regs, orig_ip); > + } > + > + /* > + * If pre_handler returns !0, it changes regs->pc. We have to > + * skip emulating post_handler. > + */ > + __this_cpu_write(current_kprobe, NULL); > + } > +} > +NOKPROBE_SYMBOL(kprobe_ftrace_handler); > + > +int arch_prepare_kprobe_ftrace(struct kprobe *p) > +{ > + p->ainsn.api.insn = NULL; > + return 0; > +} > -- > 2.7.4 > -- Masami Hiramatsu