Re: [Xen-devel] crash in trace.c with large extra_data

[George Dunlap <George.Dunlap@xxxxxxxxxxxxx>]

The general idea is that callers of trace_var() *shouldn't* be calling
with extra_words > TRACE_EXTRA_MAX.  It's an assert so that it breaks
on debug builds, allowing programmers to fix the mistake (obviously
mine in this case), but not on production builds.

I suppose it could be changed into a warning of some kind instead.

 -George

On Mon, Jul 11, 2011 at 3:02 PM, Olaf Hering <olaf@xxxxxxxxx> wrote:
>
> I just ran into the crash below, and I wonder why the ASSERT in
> __trace_var() is there anyway? Shouldnt the value of extra_word just
> be truncated to TRACE_EXTRA_MAX without crashing the hypervisor??
>
> Olaf
>
>
> (XEN) Assertion 'extra_word <= TRACE_EXTRA_MAX' failed at trace.c:687
> (XEN) Debugging connection not set up.
> (XEN) ----[ Xen-4.2.23658-20110711.092126  x86_64  debug=y  Not tainted ]----
> (XEN) CPU:    1
> (XEN) RIP:    e008:[<ffff82c480128783>] __trace_var+0x4d/0x3b8
> (XEN) RFLAGS: 0000000000010006   CONTEXT: hypervisor
> (XEN) rax: 0000000000000000   rbx: ffff83083ffbfcc8   rcx: ffff83083ffbfc58
> (XEN) rdx: 0000000000000028   rsi: 0000000000000001   rdi: 0000000000802006
> (XEN) rbp: ffff83083ffbfc48   rsp: ffff83083ffbfbe8   r8:  0000000000000000
> (XEN) r9:  0000000000000000   r10: 0000000000000000   r11: ffffffff801b5760
> (XEN) r12: 000000000000000a   r13: 0000000000802006   r14: 0000000000000001
> (XEN) r15: ffff83083ffbfc58   cr0: 000000008005003b   cr4: 00000000000026f0
> (XEN) cr3: 000000084ea89000   cr2: ffff882f64213db0
> (XEN) ds: 0000   es: 0000   fs: 0000   gs: 0000   ss: 0000   cs: e008
> (XEN) Xen stack trace from rsp=ffff83083ffbfbe8:
> (XEN)    ffff82c480127959 0000000000000086 0000000000000000 ffff83083ffbfd10
> (XEN)    01ff82c4802d7f80 0000000000028004 ffff832da72db000 ffff83083ffbfcc8
> (XEN)    0000000000000022 0000000000000002 0000000000000068 ffff830839c02090
> (XEN)    ffff83083ffbfc88 ffff82c480162172 0000002200000068 0000000020000000
> (XEN)    0000000000000000 0000000000000000 0000000000000000 ffff82c4803063e8
> (XEN)    ffff83083ffbfd18 ffff82c4801631ae ffff82c480128a9b ffff82c480306360
> (XEN)    ffff82c480306360 ffff83083ffbfcc8 0000001d00000098 ffff83083ffbfdf8
> (XEN)    0000000020000000 0000000000000000 0000000000000000 0000000000000000
> (XEN)    0000000000000002 0000000000000068 0000000000000002 ffff83083ffbfdf8
> (XEN)    ffff830839806880 0000000000000000 ffff83083ffbfd88 ffff82c48015d813
> (XEN)    ffff832da72db000 ffff830839c02090 ffff832daaea3000 0000000000000246
> (XEN)    ffff83083ffe06e0 ffff83083ffbfd60 ffff82c480122a11 ffff830839806880
> (XEN)    ffff830843621390 ffff8308398068e0 ffff83083ffbff18 0000000000000000
> (XEN)    ffff83083ffbfde8 ffff82c480160708 ffff830839c02090 000000000000000c
> (XEN)    000000000020f101 0000000000000018 ffff83083ffbfe68 ffff830839806880
> (XEN)    0000000000000068 ffff8308398068e0 ffff83083ffbff18 0000000000000000
> (XEN)    ffff83083ffbfe38 ffff82c480162938 0000000020000000 0000000000000000
> (XEN)    0000000000000000 0000000000000000 ffff83083ffbff18 ffff830839806880
> (XEN)    0000000000000068 0000000000000068 ffff83083ffbfe58 ffff82c4801629a7
> (XEN)    0000000000000068 0000000000006800 ffff83083ffbfe88 ffff82c48015d969
> (XEN) Xen call trace:
> (XEN)    [<ffff82c480128783>] __trace_var+0x4d/0x3b8
> (XEN)    [<ffff82c480162172>] trace_irq_mask+0x49/0x4b
> (XEN)    [<ffff82c4801631ae>] __assign_irq_vector+0x241/0x374
> (XEN)    [<ffff82c48015d813>] set_desc_affinity+0x5d/0xd4
> (XEN)    [<ffff82c480160708>] set_msi_affinity+0x44/0x1c1
> (XEN)    [<ffff82c480162938>] move_masked_irq+0x9c/0xcd
> (XEN)    [<ffff82c4801629a7>] move_native_irq+0x3e/0x53
> (XEN)    [<ffff82c48015d969>] ack_msi_irq+0x2c/0x6e
> (XEN)    [<ffff82c4801622e3>] do_IRQ+0x16f/0x66d
> (XEN)
> (XEN)
> (XEN) ****************************************
> (XEN) Panic on CPU 1:
> (XEN) Assertion 'extra_word <= TRACE_EXTRA_MAX' failed at trace.c:687
> (XEN) ****************************************
> (XEN)
> (XEN) Reboot in five seconds...
> (XEN) Debugging connection not set up.
>
>
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>

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