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    SubjectRe: [BUG] perf and kmemcheck : fatal combination
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    Le mardi 26 avril 2011 à 14:56 +0200, Eric Dumazet a écrit :
    > Le mardi 26 avril 2011 à 14:33 +0200, Peter Zijlstra a écrit :
    > > On Tue, 2011-04-26 at 14:27 +0200, Eric Dumazet wrote:
    > > > Thats far from trivial, maybe because we dont have NOTRACK api for
    > > > percpu allocations ?
    > >
    > > We can't use per-cpu allocations from NMI context because of the same
    > > problem, per-cpu uses vmalloc and vmalloc needs faults. Hence that
    > > shouldn't be a problem.
    > >
    > > It looks like you covered most of it though, the buffer and the
    > > callchain stuff, aside from that it should only use some static data.
    > >
    > > Pekka, what does kmemcheck do for .data and .bss things?
    >
    > Hmm, maybe I have a problem because of the WARN_ON in kmemcheck and my
    > boot had "log_buf_len=32M", so kmemcheck was called again
    >
    >
    > I am now trying to remve the line 634 from
    > arch/x86/mm/kmemcheck/kmemcheck.c

    Yes, its making some progress

    [ 328.696312] BUG: unable to handle kernel
    [ 328.697078] kernel tried to execute NX-protected page - exploit attempt? (uid: 0)
    [ 328.698284] BUG: unable to handle kernel paging request at ffff88011fc07b58
    [ 328.699569] IP: [<ffff88011fc07968>] 0xffff88011fc07967
    [ 328.700488] PGD 1a94063 PUD 11f6f9067 PMD 11f7f8067 PTE 800000011fc07163
    [ 328.702327] Oops: 0011 [#1] PREEMPT SMP
    [ 328.703693] last sysfs file: /sys/devices/system/cpu/online
    [ 328.704361] CPU 0
    [ 328.704777] Modules linked in: nfsd lockd auth_rpcgss sunrpc tg3 libphy sg [last unloaded: x_tables]
    [ 328.708693]
    [ 328.709075] Pid: 4019, comm: perf Not tainted 2.6.39-rc4-00369-g23cf772-dirty #562 HP ProLiant BL460c G6
    [ 328.710581] RIP: 3c4c:[<ffff88011fc07968>] [<ffff88011fc07968>] 0xffff88011fc07967
    [ 328.711692] RSP: 0000:ffff88011b3cbfd8 EFLAGS: ffff88011fc0793c
    [ 328.712388] RAX: ffff88011b3ca000 RBX: ffff88011fc07ff8 RCX: ffff88011fc07158
    [ 328.713180] RDX: ffff88011fc03fc0 RSI: ffff88011fc00000 RDI: ffff88011fc07158
    [ 328.713959] RBP: ffff88011fc07888 R08: ffffffff81601680 R09: ffff880114278400
    [ 328.714738] R10: ffffffff81004ed3 R11: ffff88011fc078d8 R12: ffffffff8105eb99
    [ 328.715516] R13: ffff88011fc07888 R14: 0000000000000018 R15: ffff880112638238
    [ 328.716294] FS: 0000000000000000(0000) GS:ffff88011fc00000(0063) knlGS:00000000f77176c0


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