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=-13.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 3A42BC433FB for ; Mon, 13 Jul 2020 23:40:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 136AB214DB for ; Mon, 13 Jul 2020 23:40:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594683619; bh=gfiBNxjR3Ije6ZlghFkYiWaABdRxamBVhDTguxNo3ww=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=m18Qken09woQMGXbi/hSkG2Cio98rL1/60yABeKItbMh871hgSewU5VLClb9C9TSL FiRbzY1o8U9DjXQllT56lkzJ1Odf97l/zW7roEcqhGhkaUoOdqjPymwqe+pepH8d57 g5UcW3860PSU9lMM458o4rhSvRz3iqsMk0qYGG40= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727024AbgGMXkP (ORCPT ); Mon, 13 Jul 2020 19:40:15 -0400 Received: from mail.kernel.org ([198.145.29.99]:51880 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726918AbgGMXkK (ORCPT ); Mon, 13 Jul 2020 19:40:10 -0400 Received: from localhost.localdomain (unknown [89.208.247.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 3DD4221534; Mon, 13 Jul 2020 23:40:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594683610; bh=gfiBNxjR3Ije6ZlghFkYiWaABdRxamBVhDTguxNo3ww=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=WWInZ+X9msP3OXY3dt9mRDT/KbF6UgYWTCgpOR8YK9KD5bXO0/uANpfP3fEBqGOo3 1ubDB+NekKQP/wJWbI5NFwQZ00GwFTqtBTahVO6c5QrjLQEMt9AZTQ1rbKh2Rwe2zL 0dE4bsMxX8jE5W1erjGw/YYM3ii8rBeYchtVeMPc= From: guoren@kernel.org To: palmerdabbelt@google.com, paul.walmsley@sifive.com, mhiramat@kernel.org, oleg@redhat.com Cc: 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, guoren@kernel.org, me@packi.ch, bjorn.topel@gmail.com, Guo Ren , Pekka Enberg Subject: [PATCH v3 6/7] riscv: Add KPROBES_ON_FTRACE supported Date: Mon, 13 Jul 2020 23:39:21 +0000 Message-Id: <1594683562-68149-7-git-send-email-guoren@kernel.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1594683562-68149-1-git-send-email-guoren@kernel.org> References: <1594683562-68149-1-git-send-email-guoren@kernel.org> 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 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($stack)' > /sys/kernel/debug/tracing/kprobe_events echo 1 > /sys/kernel/debug/tracing/events/kprobes/enable cat /sys/kernel/debug/tracing/trace tracer: nop entries-in-buffer/entries-written: 3/3 #P:1 _-----=> irqs-off / _----=> need-resched | / _---=> hardirq/softirq || / _--=> preempt-depth ||| / delay TASK-PID CPU# |||| TIMESTAMP FUNCTION | | | |||| | | sh-87 [000] .... 551.557031: myprobe: (_do_fork+0x1a/0x2e6) dfd=0xffffffe00020af7e filename=0xffffffe00020b34e flags=0xffffffe00101e7c0 mode=0x20af86ffffffe0 cat /sys/kernel/debug/kprobes/list ffffffe00020af7e k _do_fork+0x1a [FTRACE] ^^^^^^ Signed-off-by: Guo Ren Cc: Masami Hiramatsu Cc: Palmer Dabbelt Cc: Paul Walmsley Cc: Björn Töpel Cc: Zong Li Cc: Pekka Enberg --- arch/riscv/Kconfig | 1 + arch/riscv/kernel/probes/Makefile | 1 + arch/riscv/kernel/probes/ftrace.c | 52 +++++++++++++++++++++++++++++++++++++++ 3 files changed, 54 insertions(+) create mode 100644 arch/riscv/kernel/probes/ftrace.c diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index a41b785..0e9f5eb 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -60,6 +60,7 @@ config RISCV select HAVE_FUTEX_CMPXCHG if FUTEX select HAVE_GENERIC_VDSO if MMU && 64BIT select HAVE_KPROBES + select HAVE_KPROBES_ON_FTRACE select HAVE_KRETPROBES select HAVE_PCI select HAVE_PERF_EVENTS diff --git a/arch/riscv/kernel/probes/Makefile b/arch/riscv/kernel/probes/Makefile index cb62991..7f0840d 100644 --- a/arch/riscv/kernel/probes/Makefile +++ b/arch/riscv/kernel/probes/Makefile @@ -1,5 +1,6 @@ # SPDX-License-Identifier: GPL-2.0 obj-$(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