lkml.org 
[lkml]   [2014]   [Oct]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH V4] kernel, add bug_on_warn
    (2014/10/24 21:53), Prarit Bhargava wrote:
    > 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:[<ffffffff81076b81>] [<ffffffff81076b81>] 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:
    > [<ffffffffa0423040>] ? dummy_greetings+0x40/0x40 [dummy_module]
    > [<ffffffff81076be5>] warn_slowpath_fmt+0x55/0x70
    > [<ffffffffa0423068>] init_dummy+0x28/0x30 [dummy_module]
    > [<ffffffff81002144>] do_one_initcall+0xd4/0x210
    > [<ffffffff811b52c2>] ? __vunmap+0xc2/0x110
    > [<ffffffff810f8889>] load_module+0x16a9/0x1b30
    > [<ffffffff810f3d30>] ? store_uevent+0x70/0x70
    > [<ffffffff810f49b9>] ? copy_module_from_fd.isra.44+0x129/0x180
    > [<ffffffff810f8ec6>] SyS_finit_module+0xa6/0xd0
    > [<ffffffff8166ce29>] 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 [<ffffffff81076b81>] warn_slowpath_common+0xc1/0xd0
    > RSP <ffff8807fc5afc68>
    > ---[ end trace 428218934a12088b ]---
    >
    > Successfully tested by me.
    >
    > Cc: Jonathan Corbet <corbet@lwn.net>
    > Cc: Andrew Morton <akpm@linux-foundation.org>
    > Cc: Rusty Russell <rusty@rustcorp.com.au>
    > Cc: "H. Peter Anvin" <hpa@zytor.com>
    > Cc: Andi Kleen <ak@linux.intel.com>
    > Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
    > Cc: Fabian Frederick <fabf@skynet.be>
    > 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 <prarit@redhat.com>
    >
    > [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
    > ---

    Looks good to me.
    Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>

    Thanks,
    Yasuaki Ishimatsu


    > 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" },
    > {}
    > };
    >
    >




    \
     
     \ /
      Last update: 2014-10-28 01:21    [W:3.575 / U:0.232 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site