1. 28 Jan, 2013 2 commits
    • Steven Rostedt's avatar
      ftrace: Be first to run code modification on modules · 1085a877
      Steven Rostedt authored
      commit c1bf08ac upstream.
      
      If some other kernel subsystem has a module notifier, and adds a kprobe
      to a ftrace mcount point (now that kprobes work on ftrace points),
      when the ftrace notifier runs it will fail and disable ftrace, as well
      as kprobes that are attached to ftrace points.
      
      Here's the error:
      
       WARNING: at kernel/trace/ftrace.c:1618 ftrace_bug+0x239/0x280()
       Hardware name: Bochs
       Modules linked in: fat(+) stap_56d28a51b3fe546293ca0700b10bcb29__8059(F) nfsv4 auth_rpcgss nfs dns_resolver fscache xt_nat iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack lockd sunrpc ppdev parport_pc parport microcode virtio_net i2c_piix4 drm_kms_helper ttm drm i2c_core [last unloaded: bid_shared]
       Pid: 8068, comm: modprobe Tainted: GF            3.7.0-0.rc8.git0.1.fc19.x86_64 #1
       Call Trace:
        [<ffffffff8105e70f>] warn_slowpath_common+0x7f/0xc0
        [<ffffffff81134106>] ? __probe_kernel_read+0x46/0x70
        [<ffffffffa0180000>] ? 0xffffffffa017ffff
        [<ffffffffa0180000>] ? 0xffffffffa017ffff
        [<ffffffff8105e76a>] warn_slowpath_null+0x1a/0x20
        [<ffffffff810fd189>] ftrace_bug+0x239/0x280
        [<ffffffff810fd626>] ftrace_process_locs+0x376/0x520
        [<ffffffff810fefb7>] ftrace_module_notify+0x47/0x50
        [<ffffffff8163912d>] notifier_call_chain+0x4d/0x70
        [<ffffffff810882f8>] __blocking_notifier_call_chain+0x58/0x80
        [<ffffffff81088336>] blocking_notifier_call_chain+0x16/0x20
        [<ffffffff810c2a23>] sys_init_module+0x73/0x220
        [<ffffffff8163d719>] system_call_fastpath+0x16/0x1b
       ---[ end trace 9ef46351e53bbf80 ]---
       ftrace failed to modify [<ffffffffa0180000>] init_once+0x0/0x20 [fat]
        actual: cc:bb:d2:4b:e1
      
      A kprobe was added to the init_once() function in the fat module on load.
      But this happened before ftrace could have touched the code. As ftrace
      didn't run yet, the kprobe system had no idea it was a ftrace point and
      simply added a breakpoint to the code (0xcc in the cc:bb:d2:4b:e1).
      
      Then when ftrace went to modify the location from a call to mcount/fentry
      into a nop, it didn't see a call op, but instead it saw the breakpoint op
      and not knowing what to do with it, ftrace shut itself down.
      
      The solution is to simply give the ftrace module notifier the max priority.
      This should have been done regardless, as the core code ftrace modification
      also happens very early on in boot up. This makes the module modification
      closer to core modification.
      
      Link: http://lkml.kernel.org/r/20130107140333.593683061@goodmis.orgAcked-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
      Reported-by: default avatarFrank Ch. Eigler <fche@redhat.com>
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      1085a877
    • Chris Wilson's avatar
      drm/i915: Invalidate the relocation presumed_offsets along the slow path · 4a0bc177
      Chris Wilson authored
      commit 262b6d36 upstream.
      
      In the slow path, we are forced to copy the relocations prior to
      acquiring the struct mutex in order to handle pagefaults. We forgo
      copying the new offsets back into the relocation entries in order to
      prevent a recursive locking bug should we trigger a pagefault whilst
      holding the mutex for the reservations of the execbuffer. Therefore, we
      need to reset the presumed_offsets just in case the objects are rebound
      back into their old locations after relocating for this exexbuffer - if
      that were to happen we would assume the relocations were valid and leave
      the actual pointers to the kernels dangling, instant hang.
      
      Fixes regression from commit bcf50e27
      Author: Chris Wilson <chris@chris-wilson.co.uk>
      Date:   Sun Nov 21 22:07:12 2010 +0000
      
          drm/i915: Handle pagefaults in execbuffer user relocations
      
      Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=55984Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
      Cc: Daniel Vetter <daniel.vetter@fwll.ch>
      Signed-off-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
      4a0bc177
  2. 21 Jan, 2013 17 commits
  3. 17 Jan, 2013 21 commits