Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756482AbaJXMyO (ORCPT ); Fri, 24 Oct 2014 08:54:14 -0400 Received: from mx1.redhat.com ([209.132.183.28]:42501 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756225AbaJXMyL (ORCPT ); Fri, 24 Oct 2014 08:54:11 -0400 From: Prarit Bhargava To: linux-kernel@vger.kernel.org Cc: Prarit Bhargava , Jonathan Corbet , Andrew Morton , Rusty Russell , "H. Peter Anvin" , Andi Kleen , Masami Hiramatsu , Fabian Frederick , vgoyal@redhat.com, isimatu.yasuaki@jp.fujitsu.com, linux-doc@vger.kernel.org, kexec@lists.infradead.org, linux-api@vger.kernel.org Subject: [PATCH V4] kernel, add bug_on_warn Date: Fri, 24 Oct 2014 08:53:27 -0400 Message-Id: <1414155207-29839-1-git-send-email-prarit@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There have been several times where I have had to rebuild a kernel to cause a panic when hitting a WARN() in the code in order to get a crash dump from a system. Sometimes this is easy to do, other times (such as in the case of a remote admin) it is not trivial to send new images to the user. A much easier method would be a switch to change the WARN() over to a BUG(). This makes debugging easier in that I can now test the actual image the WARN() was seen on and I do not have to engage in remote debugging. This patch adds a bug_on_warn kernel parameter and /proc/sys/kernel/bug_on_warn calls BUG() in the warn_slowpath_common() path. The function will still print out the location of the warning. An example of the bug_on_warn output: The first line below is from the WARN_ON() to output the WARN_ON()'s location. After that the new BUG() call is displayed. WARNING: CPU: 27 PID: 3204 at /home/rhel7/redhat/debug/dummy-module/dummy-module.c:25 init_dummy+0x28/0x30 [dummy_module]() bug_on_warn set, calling BUG()... ------------[ cut here ]------------ kernel BUG at kernel/panic.c:434! invalid opcode: 0000 [#1] SMP Modules linked in: dummy_module(OE+) sg nfsv3 rpcsec_gss_krb5 nfsv4 dns_resolver nfs fscache cfg80211 rfkill x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel kvm crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel igb iTCO_wdt aesni_intel iTCO_vendor_support lrw gf128mul sb_edac ptp edac_core glue_helper lpc_ich ioatdma pcspkr ablk_helper pps_core i2c_i801 mfd_core cryptd dca shpchp ipmi_si wmi ipmi_msghandler acpi_cpufreq nfsd auth_rpcgss nfs_acl lockd grace sunrpc xfs libcrc32c sr_mod cdrom sd_mod mgag200 syscopyarea sysfillrect sysimgblt i2c_algo_bit drm_kms_helper isci ttm drm libsas ahci libahci scsi_transport_sas libata i2c_core dm_mirror dm_region_hash dm_log dm_mod CPU: 27 PID: 3204 Comm: insmod Tainted: G OE 3.17.0+ #19 Hardware name: Intel Corporation S2600CP/S2600CP, BIOS RMLSDP.86I.00.29.D696.1311111329 11/11/2013 task: ffff880034e75160 ti: ffff8807fc5ac000 task.ti: ffff8807fc5ac000 RIP: 0010:[] [] warn_slowpath_common+0xc1/0xd0 RSP: 0018:ffff8807fc5afc68 EFLAGS: 00010246 RAX: 0000000000000021 RBX: ffff8807fc5afcb0 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffff88081efee5f8 RDI: ffff88081efee5f8 RBP: ffff8807fc5afc98 R08: 0000000000000096 R09: 0000000000000000 R10: 0000000000000711 R11: ffff8807fc5af93e R12: ffffffffa0424070 R13: 0000000000000019 R14: ffffffffa0423068 R15: 0000000000000009 FS: 00007f2d4b034740(0000) GS:ffff88081efe0000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f2d4a99f3c0 CR3: 00000007fd88b000 CR4: 00000000001407e0 Stack: ffff8807fc5afcb8 ffffffff8199f020 ffff88080e396160 0000000000000000 ffffffffa0423040 ffffffffa0425000 ffff8807fc5afd08 ffffffff81076be5 0000000000000008 ffffffffa0424053 ffff880700000018 ffff8807fc5afd18 Call Trace: [] ? dummy_greetings+0x40/0x40 [dummy_module] [] warn_slowpath_fmt+0x55/0x70 [] init_dummy+0x28/0x30 [dummy_module] [] do_one_initcall+0xd4/0x210 [] ? __vunmap+0xc2/0x110 [] load_module+0x16a9/0x1b30 [] ? store_uevent+0x70/0x70 [] ? copy_module_from_fd.isra.44+0x129/0x180 [] SyS_finit_module+0xa6/0xd0 [] system_call_fastpath+0x12/0x17 Code: c4 08 5b 41 5c 41 5d 41 5e 41 5f 5d c3 48 c7 c7 20 42 8a 81 31 c0 e8 fc 80 5e 00 eb 80 48 c7 c7 78 42 8a 81 31 c0 e8 ec 80 5e 00 <0f> 0b 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 55 RIP [] warn_slowpath_common+0xc1/0xd0 RSP ---[ end trace 428218934a12088b ]--- Successfully tested by me. Cc: Jonathan Corbet Cc: Andrew Morton Cc: Rusty Russell Cc: "H. Peter Anvin" Cc: Andi Kleen Cc: Masami Hiramatsu Cc: Fabian Frederick Cc: vgoyal@redhat.com Cc: isimatu.yasuaki@jp.fujitsu.com Cc: linux-doc@vger.kernel.org Cc: kexec@lists.infradead.org Cc: linux-api@vger.kernel.org Signed-off-by: Prarit Bhargava [v2]: add /proc/sys/kernel/bug_on_warn, additional documentation, modify !slowpath cases [v3]: use proc_dointvec_minmax() in sysctl handler [v4]: remove !slowpath cases, and add __read_mostly --- Documentation/kdump/kdump.txt | 7 +++++++ Documentation/kernel-parameters.txt | 3 +++ Documentation/sysctl/kernel.txt | 12 ++++++++++++ include/linux/kernel.h | 1 + include/uapi/linux/sysctl.h | 1 + kernel/panic.c | 21 ++++++++++++++++++++- kernel/sysctl.c | 9 +++++++++ kernel/sysctl_binary.c | 1 + 8 files changed, 54 insertions(+), 1 deletion(-) diff --git a/Documentation/kdump/kdump.txt b/Documentation/kdump/kdump.txt index 6c0b9f2..a04ed72 100644 --- a/Documentation/kdump/kdump.txt +++ b/Documentation/kdump/kdump.txt @@ -471,6 +471,13 @@ format. Crash is available on Dave Anderson's site at the following URL: http://people.redhat.com/~anderson/ +Trigger Kdump on WARN() +======================= + +The kernel parameter, bug_on_warn, calls BUG() in all WARN() paths. This +will cause a kdump to occur at the BUG() call. In cases where a user +wants to specify this during runtime, /proc/sys/kernel/bug_on_warn can be +set to 1 to achieve the same behaviour. Contact ======= diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 74339c5..aa1d319 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -553,6 +553,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted. bttv.pll= See Documentation/video4linux/bttv/Insmod-options bttv.tuner= + bug_on_warn BUG() instead of WARN(). Useful to cause kdump + on a WARN(). + bulk_remove=off [PPC] This parameter disables the use of the pSeries firmware feature for flushing multiple hpte entries at a time. diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt index 57baff5..dcadcdc 100644 --- a/Documentation/sysctl/kernel.txt +++ b/Documentation/sysctl/kernel.txt @@ -23,6 +23,7 @@ show up in /proc/sys/kernel: - auto_msgmni - bootloader_type [ X86 only ] - bootloader_version [ X86 only ] +- bug_on_warn - callhome [ S390 only ] - cap_last_cap - core_pattern @@ -152,6 +153,17 @@ Documentation/x86/boot.txt for additional information. ============================================================== +bug_on_warn: + +Calls BUG() in the WARN() path when set to 1. This is useful to avoid +a kernel rebuild when attempting to kdump at the location of a WARN(). + +0: only WARN(), default behaviour. + +1: call BUG() after printing out WARN() location. + +============================================================== + callhome: Controls the kernel's callhome behavior in case of a kernel panic. diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 3d770f55..fc28bff 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -423,6 +423,7 @@ extern int panic_on_oops; extern int panic_on_unrecovered_nmi; extern int panic_on_io_nmi; extern int sysctl_panic_on_stackoverflow; +extern int bug_on_warn; /* * Only to be used by arch init code. If the user over-wrote the default * CONFIG_PANIC_TIMEOUT, honor it. diff --git a/include/uapi/linux/sysctl.h b/include/uapi/linux/sysctl.h index 43aaba1..2ba0a58 100644 --- a/include/uapi/linux/sysctl.h +++ b/include/uapi/linux/sysctl.h @@ -153,6 +153,7 @@ enum KERN_MAX_LOCK_DEPTH=74, /* int: rtmutex's maximum lock depth */ KERN_NMI_WATCHDOG=75, /* int: enable/disable nmi watchdog */ KERN_PANIC_ON_NMI=76, /* int: whether we will panic on an unrecovered */ + KERN_BUG_ON_WARN=77, /* int: call BUG() in WARN() functions */ }; diff --git a/kernel/panic.c b/kernel/panic.c index d09dc5c..740d9ff 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -33,6 +33,7 @@ static int pause_on_oops; static int pause_on_oops_flag; static DEFINE_SPINLOCK(pause_on_oops_lock); static bool crash_kexec_post_notifiers; +int bug_on_warn __read_mostly; int panic_timeout = CONFIG_PANIC_TIMEOUT; EXPORT_SYMBOL_GPL(panic_timeout); @@ -420,13 +421,24 @@ static void warn_slowpath_common(const char *file, int line, void *caller, { disable_trace_on_warning(); - pr_warn("------------[ cut here ]------------\n"); + if (!bug_on_warn) + pr_warn("------------[ cut here ]------------\n"); pr_warn("WARNING: CPU: %d PID: %d at %s:%d %pS()\n", raw_smp_processor_id(), current->pid, file, line, caller); if (args) vprintk(args->fmt, args->args); + if (bug_on_warn) { + pr_warn("bug_on_warn set, calling BUG()...\n"); + /* + * A flood of WARN()s may occur. Prevent further WARN()s + * from panicking the system. + */ + bug_on_warn = 0; + BUG(); + } + print_modules(); dump_stack(); print_oops_end_marker(); @@ -501,3 +513,10 @@ static int __init oops_setup(char *s) return 0; } early_param("oops", oops_setup); + +static int __init bug_on_warn_setup(char *s) +{ + bug_on_warn = 1; + return 0; +} +early_param("bug_on_warn", bug_on_warn_setup); diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 4aada6d..818cd31 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -1103,6 +1103,15 @@ static struct ctl_table kern_table[] = { .proc_handler = proc_dointvec, }, #endif + { + .procname = "bug_on_warn", + .data = &bug_on_warn, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec_minmax, + .extra1 = &zero, + .extra2 = &one, + }, { } }; diff --git a/kernel/sysctl_binary.c b/kernel/sysctl_binary.c index 9a4f750..28376bf 100644 --- a/kernel/sysctl_binary.c +++ b/kernel/sysctl_binary.c @@ -137,6 +137,7 @@ static const struct bin_table bin_kern_table[] = { { CTL_INT, KERN_COMPAT_LOG, "compat-log" }, { CTL_INT, KERN_MAX_LOCK_DEPTH, "max_lock_depth" }, { CTL_INT, KERN_PANIC_ON_NMI, "panic_on_unrecovered_nmi" }, + { CTL_INT, KERN_BUG_ON_WARN, "bug_on_warn" }, {} }; -- 1.7.9.3 -- 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/