[RFC PATCH v4 0/6] uprobes: return probe implementation

[Anton Arapov <anton@redhat.com>]

Hello,

  RFC v4 uretprobes implementation. I'd be grateful for review.
  /* Oleg, this one is more quirky than previous, don't beat me. */

  These patches extending uprobes by enabling tools, such as perf(trace_event),
set a breakpoint on probed function's return address.

v4:
 - get rid of area->rp_trampoline_vaddr as it always the same as ->vaddr
 - preallocate slot, as the first one in xol_add_vma()
 - cleanup ->return_uprobes list in uprobe_free_utask(), because the
   task can exit from inside the ret-probe'd function(s).
 - in find_active_uprobe(): Once we inserted "int3" we must ensure that
   handle_swbp() will be called even if this uprobe goes away. We have
   the reference but it only protects uprobe itself, it can't protect
   agains delete_uprobe().
   IOW, we must ensure that uprobe_pre_sstep_notifier() can't return 0.
 - check, whether utask is not NULL in handle_uretprobe()
   ? do we want a printk() for this case?
 - minor handle_uretprobe() fixups

v3 changes:
  - removed uretprobe_bypass logic, it will be better to send it as
    independent patch
  - unified xol_get_trampoline_slot() and xol_get_insn_slot()
  - protected uprobe with refcounter in prepare_uretprobe()
  - uprobe_register() routine fails now, if neither consumer is set
  - enclosed implementation into 1/6, 6/6 patches -ENOSYS bits

v2 changes:
  - introduced rp_handler(), get rid of return_consumers
  - get rid of uretprobe_[un]register()
  - introduced arch_uretprobe_get_sp()
  - removed uprobe_task->doomed, kill task immediately
  - fix arch_uretprobe_hijack_return_addr()'s returns
  - address the v1 minor issues

integrated patchset:
  http://github.com/arapov/linux-aa/commits/uretprobes_v3

previous implementations:
  RFCv3: https://lkml.org/lkml/2013/2/28/148
  RFCv2: https://lkml.org/lkml/2013/1/9/157
  RFCv1: https://lkml.org/lkml/2012/12/21/133

thanks,
Anton

Anton Arapov (6):
  uretprobes: preparation patch
  uretprobes/x86: hijack return address
  uretprobes: generalize xol_get_insn_slot()
  uretprobes: return probe entry, prepare uretprobe
  uretprobes: invoke return probe handlers
  uretprobes: implemented, thus remove -ENOSYS

 arch/x86/include/asm/uprobes.h |   6 ++
 arch/x86/kernel/uprobes.c      |  29 +++++++++
 include/linux/uprobes.h        |   5 ++
 kernel/events/uprobes.c        | 134 ++++++++++++++++++++++++++++++++++++++---
 4 files changed, 166 insertions(+), 8 deletions(-)

-- 
1.8.1.2