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    Subject[13/16] [PATCH 2/3] oprofile, x86: Fix nmi-unsafe callgraph support
    2.6.32-longterm review patch.  If anyone has any objections, please let me know.

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

    From: Robert Richter <robert.richter@amd.com>

    commit a0e3e70243f5b270bc3eca718f0a9fa5e6b8262e upstream.

    Backport for stable kernel v2.6.32.y to v2.6.36.y.

    Current oprofile's x86 callgraph support may trigger page faults
    throwing the BUG_ON(in_nmi()) message below. This patch fixes this by
    using the same nmi-safe copy-from-user code as in perf.

    ------------[ cut here ]------------
    kernel BUG at .../arch/x86/kernel/traps.c:436!
    invalid opcode: 0000 [#1] SMP
    last sysfs file: /sys/devices/pci0000:00/0000:00:0a.0/0000:07:00.0/0000:08:04.0/net/eth0/broadcast
    CPU 5
    Modules linked in:

    Pid: 8611, comm: opcontrol Not tainted 2.6.39-00007-gfe47ae7 #1 Advanced Micro Device Anaheim/Anaheim
    RIP: 0010:[<ffffffff813e8e35>] [<ffffffff813e8e35>] do_nmi+0x22/0x1ee
    RSP: 0000:ffff88042fd47f28 EFLAGS: 00010002
    RAX: ffff88042c0a7fd8 RBX: 0000000000000001 RCX: 00000000c0000101
    RDX: 00000000ffff8804 RSI: ffffffffffffffff RDI: ffff88042fd47f58
    RBP: ffff88042fd47f48 R08: 0000000000000004 R09: 0000000000001484
    R10: 0000000000000001 R11: 0000000000000000 R12: ffff88042fd47f58
    R13: 0000000000000000 R14: ffff88042fd47d98 R15: 0000000000000020
    FS: 00007fca25e56700(0000) GS:ffff88042fd40000(0000) knlGS:0000000000000000
    CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: 0000000000000074 CR3: 000000042d28b000 CR4: 00000000000006e0
    DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
    Process opcontrol (pid: 8611, threadinfo ffff88042c0a6000, task ffff88042c532310)
    Stack:
    0000000000000000 0000000000000001 ffff88042c0a7fd8 0000000000000000
    ffff88042fd47de8 ffffffff813e897a 0000000000000020 ffff88042fd47d98
    0000000000000000 ffff88042c0a7fd8 ffff88042fd47de8 0000000000000074
    Call Trace:
    <NMI>
    [<ffffffff813e897a>] nmi+0x1a/0x20
    [<ffffffff813f08ab>] ? bad_to_user+0x25/0x771
    <<EOE>>
    Code: ff 59 5b 41 5c 41 5d c9 c3 55 65 48 8b 04 25 88 b5 00 00 48 89 e5 41 55 41 54 49 89 fc 53 48 83 ec 08 f6 80 47 e0 ff ff 04 74 04 <0f> 0b eb fe 81 80 44 e0 ff ff 00 00 01 04 65 ff 04 25 c4 0f 01
    RIP [<ffffffff813e8e35>] do_nmi+0x22/0x1ee
    RSP <ffff88042fd47f28>
    ---[ end trace ed6752185092104b ]---
    Kernel panic - not syncing: Fatal exception in interrupt
    Pid: 8611, comm: opcontrol Tainted: G D 2.6.39-00007-gfe47ae7 #1
    Call Trace:
    <NMI> [<ffffffff813e5e0a>] panic+0x8c/0x188
    [<ffffffff813e915c>] oops_end+0x81/0x8e
    [<ffffffff8100403d>] die+0x55/0x5e
    [<ffffffff813e8c45>] do_trap+0x11c/0x12b
    [<ffffffff810023c8>] do_invalid_op+0x91/0x9a
    [<ffffffff813e8e35>] ? do_nmi+0x22/0x1ee
    [<ffffffff8131e6fa>] ? oprofile_add_sample+0x83/0x95
    [<ffffffff81321670>] ? op_amd_check_ctrs+0x4f/0x2cf
    [<ffffffff813ee4d5>] invalid_op+0x15/0x20
    [<ffffffff813e8e35>] ? do_nmi+0x22/0x1ee
    [<ffffffff813e8e7a>] ? do_nmi+0x67/0x1ee
    [<ffffffff813e897a>] nmi+0x1a/0x20
    [<ffffffff813f08ab>] ? bad_to_user+0x25/0x771
    <<EOE>>

    Cc: John Lumby <johnlumby@hotmail.com>
    Cc: Maynard Johnson <maynardj@us.ibm.com>
    Signed-off-by: Robert Richter <robert.richter@amd.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
    ---
    arch/x86/oprofile/backtrace.c | 46 ++++++++++++++++++++++++++++++++++++++----
    1 file changed, 42 insertions(+), 4 deletions(-)

    --- a/arch/x86/oprofile/backtrace.c
    +++ b/arch/x86/oprofile/backtrace.c
    @@ -11,6 +11,8 @@
    #include <linux/oprofile.h>
    #include <linux/sched.h>
    #include <linux/mm.h>
    +#include <linux/highmem.h>
    +
    #include <asm/ptrace.h>
    #include <asm/uaccess.h>
    #include <asm/stacktrace.h>
    @@ -47,6 +49,42 @@ static struct stacktrace_ops backtrace_o
    .address = backtrace_address,
    };

    +/* from arch/x86/kernel/cpu/perf_event.c: */
    +
    +/*
    + * best effort, GUP based copy_from_user() that assumes IRQ or NMI context
    + */
    +static unsigned long
    +copy_from_user_nmi(void *to, const void __user *from, unsigned long n)
    +{
    + unsigned long offset, addr = (unsigned long)from;
    + unsigned long size, len = 0;
    + struct page *page;
    + void *map;
    + int ret;
    +
    + do {
    + ret = __get_user_pages_fast(addr, 1, 0, &page);
    + if (!ret)
    + break;
    +
    + offset = addr & (PAGE_SIZE - 1);
    + size = min(PAGE_SIZE - offset, n - len);
    +
    + map = kmap_atomic(page, KM_USER0);
    + memcpy(to, map+offset, size);
    + kunmap_atomic(map, KM_USER0);
    + put_page(page);
    +
    + len += size;
    + to += size;
    + addr += size;
    +
    + } while (len < n);
    +
    + return len;
    +}
    +
    struct frame_head {
    struct frame_head *bp;
    unsigned long ret;
    @@ -54,12 +92,12 @@ struct frame_head {

    static struct frame_head *dump_user_backtrace(struct frame_head *head)
    {
    + /* Also check accessibility of one struct frame_head beyond: */
    struct frame_head bufhead[2];
    + unsigned long bytes;

    - /* Also check accessibility of one struct frame_head beyond */
    - if (!access_ok(VERIFY_READ, head, sizeof(bufhead)))
    - return NULL;
    - if (__copy_from_user_inatomic(bufhead, head, sizeof(bufhead)))
    + bytes = copy_from_user_nmi(bufhead, head, sizeof(bufhead));
    + if (bytes != sizeof(bufhead))
    return NULL;

    oprofile_add_trace(bufhead[0].ret);



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