Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757583AbaFSOTL (ORCPT ); Thu, 19 Jun 2014 10:19:11 -0400 Received: from mx1.redhat.com ([209.132.183.28]:65186 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756031AbaFSOTJ (ORCPT ); Thu, 19 Jun 2014 10:19:09 -0400 Date: Thu, 19 Jun 2014 09:18:57 -0500 From: Josh Poimboeuf To: Masami Hiramatsu Cc: Steven Rostedt , Ingo Molnar , Namhyung Kim , Linux Kernel Mailing List , Ananth N Mavinakayanahalli , "systemtap@sources.redhat.com" Subject: Re: [PATCH -tip v2 0/3] ftrace, kprobes: Introduce IPMODIFY flag for ftrace_ops to detect conflicts Message-ID: <20140619141857.GA17328@treble.hsd1.ky.comcast.net> References: <20140617110436.15167.7179.stgit@kbuild-fedora.novalocal> <20140619020831.GA21146@treble.redhat.com> <53A26F23.1050702@hitachi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <53A26F23.1050702@hitachi.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 19, 2014 at 02:03:31PM +0900, Masami Hiramatsu wrote: > (2014/06/19 11:08), Josh Poimboeuf wrote: > > On Tue, Jun 17, 2014 at 11:04:36AM +0000, Masami Hiramatsu wrote: > >> Hi, > >> > >> Here is the version 2 of the series of patches which introduces > >> IPMODIFY flag for ftrace_ops to detect conflicts of ftrace users > >> who can modify regs->ip in their handler. > >> In this version, I fixed some bugs in previous version and > >> added a patch which made kprobe itself free from IPMODIFY > >> except for jprobe. > > > > Hi Masami, > > > > This seems better, but I still saw a few issues. I'm not sure if the > > issues are specific to stap or kprobes. For the following issues I used > > this command to set a kprobe: > > > > stap -v -e 'probe kernel.function("meminfo_proc_show") {printf("meminfo_proc_show called\n");}' > > > > With patches 1-2, when I used stap to kprobe the function after it was > > already kpatched, stap didn't return an error and instead acted like it > > succeeded (though the probe didn't work): > > > > $ sudo stap -v -e 'probe kernel.function("meminfo_proc_show") {printf("meminfo_proc_show called\n");}' > > Pass 1: parsed user script and 112 library script(s) using 221516virt/41612res/6028shr/36228data kb, in 130usr/0sys/132real ms. > > Pass 2: analyzed script: 1 probe(s), 0 function(s), 0 embed(s), 0 global(s) using 255840virt/77132res/7132shr/70552data kb, in 510usr/20sys/577real ms. > > Pass 3: translated to C into "/tmp/stap3Qunba/stap_2690192fea570fb7bba78c7ed7fa1e0d_898_src.c" using 255840virt/77392res/7392shr/70552data kb, in 10usr/0sys/4real ms. > > Pass 4: compiled C into "stap_2690192fea570fb7bba78c7ed7fa1e0d_898.ko" in 5020usr/640sys/7105real ms. > > Pass 5: starting run. > > (no error) > > Yeah, I guess you can see some warning messages in dmesg (by > arm_kprobe) at this point. Ah, you're right: Jun 19 08:03:10 treble kernel: ------------[ cut here ]------------ Jun 19 08:03:10 treble kernel: WARNING: CPU: 1 PID: 17991 at kernel/kprobes.c:953 arm_kprobe+0xa7/0xe0() Jun 19 08:03:10 treble kernel: Failed to init kprobe-ftrace (-16) Jun 19 08:03:10 treble kernel: Modules linked in: stap_1faf9cc0ccf85c0d203c74ab6f604b_17991(OE) ...defra Jun 19 08:03:10 treble kernel: videobuf2_vmalloc serio_raw microcode sdhci_pci bluetooth videobuf2_m... Jun 19 08:03:10 treble kernel: CPU: 1 PID: 17991 Comm: stapio Tainted: G U W OE 3.15.0+ #1 Jun 19 08:03:10 treble kernel: Hardware name: LENOVO 2356BH8/2356BH8, BIOS G7ET63WW (2.05 ) 11/12/2012 Jun 19 08:03:10 treble kernel: 0000000000000000 000000009023f19e ffff8803dcce7d80 ffffffff816f31fd Jun 19 08:03:10 treble kernel: ffff8803dcce7dc8 ffff8803dcce7db8 ffffffff8108914d ffffffffa08248e0 Jun 19 08:03:10 treble kernel: ffffffffa08248f0 0000000000000000 0000000000000000 0000000000000000 Jun 19 08:03:10 treble kernel: Call Trace: Jun 19 08:03:10 treble kernel: [] dump_stack+0x45/0x56 Jun 19 08:03:10 treble kernel: [] warn_slowpath_common+0x7d/0xa0 Jun 19 08:03:10 treble kernel: [] warn_slowpath_fmt+0x5c/0x80 Jun 19 08:03:10 treble kernel: [] arm_kprobe+0xa7/0xe0 Jun 19 08:03:10 treble kernel: [] register_kprobe+0x557/0x5d0 Jun 19 08:03:10 treble kernel: [] ? meminfo_proc_open+0x30/0x30 Jun 19 08:03:10 treble kernel: [] _stp_ctl_write_cmd+0x8d5/0x930 [stap_1faf9c...7991] Jun 19 08:03:10 treble kernel: [] vfs_write+0xba/0x1e0 Jun 19 08:03:10 treble kernel: [] SyS_write+0x55/0xd0 Jun 19 08:03:10 treble kernel: [] system_call_fastpath+0x16/0x1b Jun 19 08:03:10 treble kernel: ---[ end trace 19615ed55413a30d ]--- Why not change arm_kprobe() to return an error? > > > > > With all 3 patches, I expected kprobes and kpatch to be able to ftrace > > the same function. But when I tried to kpatch the function after it was > > kprobed, I got the following oops in stap: > > > > [ 455.842797] BUG: unable to handle kernel NULL pointer dereference at 0000000000000020 > > [ 455.843388] IP: [] _stp_module_notifier+0x1e/0x320 [stap_2690192fea570fb7bba78c7ed7fa1e_20189] > > Hmm, since this happens in _stp_module_notifier() which is a code in systemtap, > I guess it's a systemtap problem. > > Could you test it with kprobe-tracer as below? > > # (do something kpatch related activation) > # echo p meminfo_proc_show > /sys/kernel/debug/tracing/kprobe_events > # echo 1 > /sys/kernel/debug/tracing/events/kprobe/enable That worked, thanks. > > Thank you, > > > [ 455.844011] PGD 33f898067 PUD 422083067 PMD 0 > > [ 455.844638] Oops: 0000 [#1] SMP > > [ 455.845255] Modules linked in: kpatch(OE+) stap_2690192fea570fb7bba78c7ed7fa1e_20189(OE) rfcomm ipt_MASQUERADE fuse ccm xt_CHECKSUM tun ip6t_rpfilter ip6t_REJECT xt_conntrack ebtable_nat ebtable_broute bridge stp llc ebtable_filter ebtables ip6table_nat nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6table_mangle ip6table_security ip6table_raw ip6table_filter ip6_tables iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_mangle iptable_security iptable_raw bnep arc4 iwldvm mac80211 iTCO_wdt snd_hda_codec_hdmi iTCO_vendor_support x86_pkg_temp_thermal snd_hda_codec_realtek coretemp iwlwifi snd_hda_codec_generic kvm_intel snd_hda_intel kvm uvcvideo snd_hda_controller cfg80211 snd_hda_codec btusb videobuf2_vmalloc bluetooth videobuf2_memops snd_hwdep snd_seq nfsd videobuf2_core > > [ 455.848272] v4l2_common videodev snd_seq_device e1000e microcode snd_pcm sdhci_pci media joydev sdhci serio_raw i2c_i801 pcspkr mmc_core thinkpad_acpi mei_me snd_timer auth_rpcgss mei snd lpc_ich ptp mfd_core shpchp nfs_acl lockd pps_core wmi tpm_tis soundcore tpm rfkill sunrpc dm_crypt i915 i2c_algo_bit drm_kms_helper drm crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel i2c_core video > > [ 455.850887] CPU: 3 PID: 19857 Comm: insmod Tainted: G W OE 3.16.0-rc1+ #2 > > [ 455.851768] Hardware name: LENOVO 2356BH8/2356BH8, BIOS G7ET63WW (2.05 ) 11/12/2012 > > [ 455.852638] task: ffff880095d65460 ti: ffff88039d1d4000 task.ti: ffff88039d1d4000 > > [ 455.853456] RIP: 0010:[] [] _stp_module_notifier+0x1e/0x320 [stap_2690192fea570fb7bba78c7ed7fa1e_20189] > > [ 455.854335] RSP: 0018:ffff88039d1d7ce0 EFLAGS: 00010246 > > [ 455.855212] RAX: ffffffffa0837f50 RBX: 0000000000000000 RCX: 00000000ffffffff > > [ 455.856109] RDX: ffffffffa08400e0 RSI: 0000000000000001 RDI: ffffffffa0837f50 > > [ 455.856986] RBP: ffff88039d1d7d00 R08: 0000000000000000 R09: 0000000000000000 > > [ 455.857880] R10: 0000000000000001 R11: ffffc9001aed2d8f R12: ffffffff81c593e0 > > [ 455.858761] R13: 0000000000000001 R14: ffffffffa08400e0 R15: 0000000000000000 > > [ 455.859640] FS: 00007feac5f10740(0000) GS:ffff88043e2c0000(0000) knlGS:0000000000000000 > > [ 455.860523] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > [ 455.861403] CR2: 0000000000000020 CR3: 00000004224e7000 CR4: 00000000001407e0 > > [ 455.862309] Stack: > > [ 455.863236] 00000000fffffffd ffffffff81c593e0 0000000000000001 ffffffffa08400e0 > > [ 455.864163] ffff88039d1d7d38 ffffffff810b45bc ffffffff81c557c0 0000000000000000 > > [ 455.865103] 0000000000000001 ffffffffa08400e0 00000000ffffffff ffff88039d1d7d78 > > [ 455.866067] Call Trace: > > [ 455.867100] [] notifier_call_chain+0x4c/0x70 > > [ 455.868202] [] __blocking_notifier_call_chain+0x4d/0x70 > > [ 455.869155] [] blocking_notifier_call_chain+0x16/0x20 > > [ 455.870111] [] load_module+0x1aac/0x25f0 > > [ 455.871067] [] ? kernel_read+0x50/0x80 > > [ 455.872022] [] SyS_finit_module+0xa6/0xd0 > > [ 455.872982] [] system_call_fastpath+0x16/0x1b > > [ 455.873941] Code: 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 55 48 83 fe 01 48 89 e5 41 56 49 89 d6 41 55 41 54 53 48 8b 9a d0 01 00 00 <8b> 43 20 0f 84 59 01 00 00 48 85 f6 75 44 85 c0 74 4a 83 e8 01 > > [ 455.876073] RIP [] _stp_module_notifier+0x1e/0x320 [stap_2690192fea570fb7bba78c7ed7fa1e_20189] > > [ 455.877146] RSP > > [ 455.878243] CR2: 0000000000000020 > > [ 455.883707] ---[ end trace 388d9e62d4390d42 ]--- > > > > > -- > Masami HIRAMATSU > Software Platform Research Dept. Linux Technology Research Center > Hitachi, Ltd., Yokohama Research Laboratory > E-mail: masami.hiramatsu.pt@hitachi.com > > -- Josh -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/