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SubjectRe: [Problem] kernel hangs at boot (bisected 892d208bcf)
Date
Hi Catalin,

Catalin Marinas <catalin.marinas@arm.com> writes:

> Hi Dirk,
>
> On Wed, Jan 18, 2012 at 07:32:59PM +0000, Dirk Gouders wrote:
>> I am not sure if you are the correct person to contact,
>
> I am for kmemleak :) but I'm not sure it's kmemleak's fault here.
>
>> but
>> I noticed a regression in Linus' master branch and bisected this to
>> commit 892d208bcf
>> "Merge tag 'kmemleak' of git://git.kernel.org/pub/scm/linux/kernel/git/cmarinas/linux".
> ...
>> Freeing unused kernel memory: 608k freed
>> kernel tried to execute NX-protected page - exploit attempt? (uid: 0)
>> BUG: unable to handle kernel paging request at ffffffff818b232b
>> IP: [<ffffffff818b232b>] kmemleak_late_init+0x8a/0x8a
>> PGD 17ed067 PUD 17f1063 PMD 3c6a9063 PTE 80000000018b2163
>> Oops: 0011 [#1] SMP
>> CPU 1
>> Modules linked in:
>>
>> Pid: 1, comm: swapper/0 Not tainted 3.2.0-09104-gccb19d2 #4 Bochs Bochs
>> RIP: 0010:[<ffffffff818b232b>] [<ffffffff818b232b>] kmemleak_late_init+0x8a/0x8a
>> RSP: 0018:ffff88003fd03e58 EFLAGS: 00010282
>> RAX: 0000000000000001 RBX: ffff88003dbd2600 RCX: 0000000000000000
>> RDX: 0000000000000000 RSI: ffff88003dbd2600 RDI: 0000000000000002
>> RBP: ffff88003e015488 R08: ffff88003fd0d5c0 R09: ffff88003fd122e0
>> R10: 0000000000000400 R11: ffffffff81572da5 R12: ffffea0000f6f480
>> R13: ffffffff810aa687 R14: 0000000000000000 R15: ffff88003e31dbc8
>> FS: 0000000000000000(0000) GS:ffff88003fd00000(0000) knlGS:0000000000000000
>> CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
>> CR2: ffffffff818b232b CR3: 00000000017eb000 CR4: 00000000000006e0
>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
>> Process swapper/0 (pid: 1, threadinfo ffff88003e272000, task ffff88003e278000)
>> Stack:
>> ffffffff810fed11 ffff88003dbd2680 ffff88003fd0d830 ffffffff81805980
>> ffff88003d48dd00 ffff88003fd0d860 ffffffff810aa687 ffff88003e2ad420
>> 0000000a3e2ad820 ffff88003e272000 ffff88003e278000 ffff88003fd03eb0
>> Call Trace:
>> <IRQ>
>> [<ffffffff810fed11>] ? kmem_cache_free+0x4f/0xd9
>> [<ffffffff810aa687>] ? __rcu_process_callbacks+0x1bf/0x2e2
>> [<ffffffff810aa7f4>] ? rcu_process_callbacks+0x4a/0x95
>> [<ffffffff8105cc1a>] ? __do_softirq+0xb6/0x171
>> [<ffffffff8155a58c>] ? call_softirq+0x1c/0x30
>> [<ffffffff81032d85>] ? do_softirq+0x31/0x68
>> [<ffffffff8105ce7f>] ? irq_exit+0x44/0x9e
>> [<ffffffff81047fd9>] ? smp_apic_timer_interrupt+0x85/0x95
>> [<ffffffff818d1000>] ? free_area_init_node+0x21f/0x2fb
>> [<ffffffff81559c4b>] ? apic_timer_interrupt+0x6b/0x70
>> <EOI>
>> [<ffffffff818d1000>] ? free_area_init_node+0x21f/0x2fb
>> [<ffffffff818d14b0>] ? __next_free_mem_range_rev+0x57/0x11e
>> [<ffffffff8104d31b>] ? free_init_pages+0xea/0x110
>> [<ffffffff810001c0>] ? init_post+0xe/0xbb
>> [<ffffffff81895b93>] ? kernel_init+0x10f/0x113
>> [<ffffffff8155a494>] ? kernel_thread_helper+0x4/0x10
>> [<ffffffff81895a84>] ? start_kernel+0x319/0x319
>> [<ffffffff8155a490>] ? gs_change+0xb/0xb
>> Code: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc <cc> cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc
>> RIP [<ffffffff818b232b>] kmemleak_late_init+0x8a/0x8a
>> RSP <ffff88003fd03e58>
>> CR2: ffffffff818b232b
>
> I don't really see how kmemleak could cause such error (or any of the
> recent changes I have made). It looks like some of the code in the
> .init.text section is not executable.
>
> If you still have the vmlinux around, could you please run:
>
> addr2line -i -f -e vmlinux ffffffff818b232b
>
> The code shown shown in the oops message is also a bit weird (all 0xcc).
> Maybe you could do an objdump -d in that area, see if it looks like sane
> asm code.

I'll attach the information you asked for.
I mentioned that while bisecting there was another commit that gave me
hangs on boot. This was when about six candidates were left and I will
re-bisect with treating that commit bad and see where I get then.

Best regards,

Dirk

------------------------------------------------------------------------

$ addr2line -i -f -e vmlinux ffffffff818b232b
log_early
kmemleak.c:0

And here the requested part of objdump (maybe obvious: I searched for
the cc pattern as well but did not find any):

ffffffff818b232b <log_early>:
ffffffff818b232b: 55 push %rbp
ffffffff818b232c: 53 push %rbx
ffffffff818b232d: 48 83 ec 08 sub $0x8,%rsp
ffffffff818b2331: 8b 05 1d 32 13 00 mov 0x13321d(%rip),%eax # ffffffff819e5554 <kmemleak_error>
ffffffff818b2337: 85 c0 test %eax,%eax
ffffffff818b2339: 74 08 je ffffffff818b2343 <log_early+0x18>
ffffffff818b233b: ff 05 6f 2f 03 00 incl 0x32f6f(%rip) # ffffffff818e52b0 <crt_early_log>
ffffffff818b2341: eb 5c jmp ffffffff818b239f <log_early+0x74>
ffffffff818b2343: 81 3d 63 2f 03 00 8f cmpl $0x18f,0x32f63(%rip) # ffffffff818e52b0 <crt_early_log>
ffffffff818b234a: 01 00 00
ffffffff818b234d: 76 0b jbe ffffffff818b235a <log_early+0x2f>
ffffffff818b234f: 48 83 c4 08 add $0x8,%rsp
ffffffff818b2353: 5b pop %rbx
ffffffff818b2354: 5d pop %rbp
ffffffff818b2355: e9 68 0d 85 ff jmpq ffffffff811030c2 <kmemleak_disable>
ffffffff818b235a: 9c pushfq
ffffffff818b235b: 5d pop %rbp
ffffffff818b235c: fa cli
ffffffff818b235d: 48 63 1d 4c 2f 03 00 movslq 0x32f4c(%rip),%rbx # ffffffff818e52b0 <crt_early_log>


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