Messages in this thread | | | Subject | Re: BUG: unable to handle kernel paging request from pty_write [was: Linux 4.4.2] | From | Jiri Slaby <> | Date | Thu, 25 Feb 2016 22:32:26 +0100 |
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On 02/25/2016, 09:51 PM, Linus Torvalds wrote: > Jiri, can you check your try_to_wake_up() disassembly for some > indirect "jmp" instructions?
Nope, there is none.
I will reply to all your questions tomorrow.
Just quickly, as I have to go (and don't want you to duplicate efforts) the kernel which was used can be obtained here: https://build.opensuse.org/package/binaries/openSUSE:Factory:Staging:I/kernel-default?repository=standard
The issue is very weird, indeed, this is what I noted to our bugzilla: The stack trace ends in call of try_to_wake_up. Then, there it has to be some of the indirect calls:
callq *0x40(%rax) p->sched_class->select_task_rq from select_task_rq
RAX is 0x00000000bb37e180, barely can be read with offset 0x40
callq *0xd85656(%rip) # ffffffff81e2aba0 <smp_ops+0x20> smp_ops.smp_send_reschedule from ttwu_queue_remote
Which hardly can be it, given smp_ops is static.
So it has to be some other "call *" from a nested function :(.
Interestingly, RBP contains address inside try_to_wake_up -- ffffffff810a535a (dunno why) which is: ffffffff810a5355: e8 66 a0 ff ff callq ffffffff8109f3c0 <ttwu_stat> ffffffff810a535a: e9 9d fe ff ff jmpq ffffffff810a51fc <try_to_wake_up+0x3c>
ttwu_stat does in the begginning: mov $0x16e80,%r14
which is what we actually still have in r14 when it crashes. The first ttwu_stat's "if" has to go through the true branch (otherwise r14 would be overwritten).
Another note: we die when jmp/calling to 0xffff88023fd40000. RSI=RDI=0xffff88023fdd6e80. RSI-RIP is 0x96e80, which is R14 + 0x80000. Coincidence?
thanks, -- js suse labs
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