| scoopex | i have a problem with a deadlocked kernel driver. in former times (on s390x) i used "crash" to attach a debugger to the kernel and to get a backtrace of the blocked syscall. what can i use in a similar way. i installed "crash" on 16.04 system and it seems to be the thing i am searching for, but i have not managed to attach to the running kernel ("crash /boot/vmlinux-4.10.0-33-generic | 07:55 |
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| scoopex | /boot/System.map-4.10.0-33-generic") any hints? | 07:55 |
| smb | scoopex, not sure but you might have more luck by picking the source (package) of crash from zesty and re-compile it for xenial | 08:13 |
| smb | oh wait... to attach to the running kernel you would not use the files from /boot | 08:16 |
| smb | scoopex, you need a vmlinuz from a ddeb (http://ddebs.ubuntu.com/pool/main/l/linux/). That is what crash is referring to as namelist. The other argument is optionally a memory dump or (if not given, it will try to attach to /dev/kmem (only works as root) | 08:25 |
| scoopex | smb: i used https://github.com/torvalds/linux/blob/master/scripts/extract-vmlinux to get a uncompressed kernel image. as i remember it was possible to add a System.map to have the positions of functions available to crash | 08:34 |
| scoopex | i perfomed a "strace -f -o /tmp/foo crash /boot/vmlinux-4.10.0-33-generic" and there is no access to "kmem" only a failing access to "/dev/crash" | 08:38 |
| smb | scoopex, normally it is enough to use the (unstripped) vmlinux from the ddeb but newer kernels often add things which crash might not (yet) have catched up with | 08:40 |
| scoopex | there is no /dev/kmem and not /dev/crash on my system.... | 08:41 |
| smb | it uses /proc/kcore then, but again not sure the xenial crash can handle 4.10 kernels in all situations (kaslr causes a lot of pain) | 08:51 |
| scoopex | smb: but i also see no attempt in stracte to use or open /proc/kcore | 09:11 |
| scoopex | hmm, how do you inspect the behavior of kernel threads in a running system? are the alternatives? | 09:24 |
| scoopex | automated crashdumps of standard kernels would also have the same problem, right? | 09:25 |
| smb | scoopex, the dump files created by kdump-tools were working from what I remember | 09:26 |
| scoopex | but "crash" also has a option "--kaslr auto | 09:27 |
| smb | it has but that does not really seem to work well | 09:28 |
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| kees | sforshee: hi! you around? | 21:59 |
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