Linux has by no means suffered from the notorious BSoD, quick for blue display of dying, the title given to the dreaded “one thing went terribly flawed” message related to a Home windows system crash.
Microsoft has tried many issues through the years to shake that nickname “BSoD”, together with altering the background color used when crash messages seem, including a super-sized sad-face emoticon to make the message really feel extra compassionate, displaying QR codes that you may snap along with your cellphone that will help you diagnose the issue, and never filling the display with a technobabble record of kernel code objects that simply occurred to be loaded on the time.
(These crash dump lists usually led to anti-virus and threat-prevention software program being blamed for each system crash, just because their names tended to present up at or close to the highest of the record of loaded modules – not as a result of that they had something to do with the crash, however as a result of they often loaded early on and simply occurred to be on the high of the record, thus making a handy scaepgoat.)
Even higher, “BSoD” is not the on a regular basis, throwaway pejorative time period that it was once, as a result of Home windows crashes so much much less usually than it used to.
We’re not suggesting that Home windows by no means crashes, or imlying that it’s now magically bug-free; merely noting that you just typically don’t want the phrase BSoD as usually as you used to.
Linux crash notifications
In fact, Linux has by no means had BSoDs, not even again when Home windows appeared to have them on a regular basis, however that’s not as a result of Linux by no means crashes, or is magically bug-free.
It’s merely that Linux does’t BSoD (sure, the time period can be utilized as an intransitive verb, as in “my laptop computer BSoDded half approach via an e-mail”), as a result of – in a pleasant understatment – it suffers an oops, or if the oops is extreme sufficient that the system can’t reliably keep up even with degraded efficiency, it panics.
(It’s additionally attainable to configure a Linux kernel in order that an oops all the time get “promoted” to a panic, for environments the place safety concerns make it higher to have a system that shuts down abruptly, albeit with some knowledge not getting saved in time, than a system that results in an unsure state that might result in knowledge leakage or knowledge corruption.)
An oops usually produces console output one thing like this (we’ve offered supply code under if you wish to discover oopses and panics for your self):
[12710.153112] oops init (stage = 1)
[12710.153115] triggering oops through BUG()
[12710.153127] ------------[ cut here ]------------
[12710.153128] kernel BUG at /dwelling/duck/Articles/linuxoops/oops.c:17!
[12710.153132] invalid opcode: 0000 [#1] PREEMPT SMP PTI
[12710.153748] CPU: 0 PID: 5531 Comm: insmod . . .
[12710.154322] {Hardware} title: XXXX
[12710.154940] RIP: 0010:oopsinit+0x3a/0xfc0 [oops]
[12710.155548] Code: . . . . .
[12710.156191] RSP: . . . EFLAGS: . . .
[12710.156849] RAX: . . . RBX: . . . RCX: . . .
[12710.157513] RDX: . . . RSI: . . . RDI: . . .
[12710.158171] RBP: . . . R08: . . . R09: . . .
[12710.158826] R10: . . . R11: . . . R12: . . .
[12710.159483] R13: . . . R14: . . . R15: . . .
[12710.160143] FS: . . . GS: . . . knlGS: . . .
. . . . .
[12710.163474] Name Hint:
[12710.164129]
[12710.164779] do_one_initcall+0x56/0x230
[12710.165424] do_init_module+0x4a/0x210
[12710.166050] __do_sys_finit_module+0x9e/0xf0
[12710.166711] do_syscall_64+0x37/0x90
[12710.167320] entry_SYSCALL_64_after_hwframe+0x72/0xdc
[12710.167958] RIP: 0033:0x7f6c28b15e39
[12710.168578] Code: . . . . .
[. . . . .
[12710.173349]
[12710.174032] Modules linked in: . . . . .
[12710.180294] ---[ end trace 0000000000000000 ]---
Sadly, when kernel model 6.2.3 got here out on the finish of final week, two tiny modifications rapidly proved to be problematic, with customers reporting kernel oopses when managing disk storage.
Kernel 6.1.16 was apparently topic to the identical modifications, and thus susceptible to the identical oopsiness.
For instance, plugging in an detachable drive and mounting it labored high-quality, however unmounting the drive once you’d completed with it may trigger an oops.
Though an oops doesn’t instantly freeze the entire pc, kernel-level code crashes when umounting disk storage are worrisone sufficient {that a} well-informed person would in all probability wish to shut down as quickly as attainable, in case of ongoing hassle resulting in knowledge corruption…
…however some customers reported that the oops prevented what’s identified within the jargon as an orderly shutdown, requiring forcibly biking the ability, by holding down the ability button for a number of seconds, or quickly slicing the mains provide to a server.
The excellent news is that kernels 6.2.4 and 6.1.17 have been instantly launched over the weekend to roll again the issues.
Given the rate of Linux kernel releases, these updates have already been adopted by 6.2.5 and 6.1.18, which have been themselves up to date (immediately, 2023-03-13) by 6.2.6 and 6.1.19.
What to do?
If you’re utilizing a 6.x-version Linux kernel and also you aren’t already bang up-to-date, be sure you don’t set up 6.2.3 or 6.1.16 alongside the best way.
In case you’ve already obtained a type of variations (we had 6.2.3 for a few days and have been unable to impress a driver crash, presumably as a result of our kernel configuration shielded us inadvertently from triggering the bug), contemplate updating as quickly as you’ll be able to…
…as a result of even if you happen to haven’t suffered any disk-volume-based hassle thus far, chances are you’ll be immune by success, however by upgrading your kernel once more you’ll change into immune by design.
EXPLORING OOPS AND PANIC EVENTS ON YOUR OWN
You will want a kernel constructed from supply code that’s already put in in your check pc.
Create a listing, let’s name it /check/oops, and save this supply code as oops.c:
#embrace <linux/kernel.h>
#embrace <linux/module.h>
#embrace <linux/moduleparam.h>
#embrace <linux/init.h>
MODULE_LICENSE("GPL");
static int stage = 0;
module_param(stage,int,0660);
static int oopsinit(void) {
printk("oops init (stage = %d)n",stage);
// stage: 0->simply load; 1->oops; 2->panic
swap (stage) {
case 1:
printk("triggering oops through BUG()n");
BUG();
break;
case 2:
printk("forcing a full-on panic()n");
panic("oops module");
break;
}
return 0;
}
static void oopsexit(void) {
printk("oops exitn");
}
module_init(oopsinit);
module_exit(oopsexit);
Create a file in the identical listing known as Kbuild to manage the construct parameters, like this:
EXTRA_CFLAGS = -Wall -g obj-m = oops.o
Then construct the module as proven under.
The -C possibility tells make the place to start out on the lookout for Makefiles, thus pointing the construct course of on the proper kernel supply code tree, and the M= setting tells make the place to seek out the precise module code to construct on this event.
You could present the complete, absolute path for M=, so don’t attempt to save typing by utilizing ./ (the present listing strikes round in the course of the construct course of):
/check/oops$ make -C /the place/you/constructed/the/kernel M=/check/oops CC [M] /dwelling/duck/Articles/linuxoops/oops.o MODPOST /dwelling/duck/Articles/linuxoops/Module.symvers CC [M] /dwelling/duck/Articles/linuxoops/oops.mod.o LD [M] /dwelling/duck/Articles/linuxoops/oops.ko
You may load and unload the brand new oops.ko kernel module with the parameter stage=0 simply to test that it really works.
Look in dmesg for a log of the init and exit calls:
/check/oops# insmod oops.ko stage=0 /check/oops# rmmod oops /check/oops# dmesg . . . [12690.998373] oops: loading out-of-tree module taints kernel. [12690.999113] oops init (stage = 0) [12704.198814] oops exit
To impress an oops (recoverable) or a panic (will dangle your pc), use stage=1 or stage=2 respectively.
Don’t neglect to save lots of all of your work earlier than triggering both situation (you will want to reboot afterwards), and don’t do that on another person’s pc with out formal permission.
