Now that PPC64 has no-execute support, here is a second try to fix the
single step out of line during kprobe execution.  Kprobes on x86_64 already
solved this problem by allocating an executable page and using it as the
scratch area for stepping out of line.  Reuse that.
Signed-off-by: NAnanth N Mavinakayanahalli <ananth@in.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

The current Kprobes when patching the original instruction with the break
instruction tries to retain the original qualifying predicate(qp), however
for cmp.crel.ctype where ctype == unc, which is a special instruction
always needs to be executed irrespective of qp.  Hence, if the instruction
we are patching is of this type, then we should not copy the original qp to
the break instruction, this is because we always want the break fault to
happen so that we can emulate the instruction.

This patch is based on the feedback given by David Mosberger
Signed-off-by: NAnil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

A cleanup of the ia64 kprobes implementation such that all of the bundle
manipulation logic is concentrated in arch_prepare_kprobe().

With the current design for kprobes, the arch specific code only has a
chance to return failure inside the arch_prepare_kprobe() function.

This patch moves all of the work that was happening in arch_copy_kprobe()
and most of the work that was happening in arch_arm_kprobe() into
arch_prepare_kprobe().  By doing this we can add further robustness checks
in arch_arm_kprobe() and refuse to insert kprobes that will cause problems.
Signed-off-by: NRusty Lynch <Rusty.lynch@intel.com>
Signed-off-by: NAnil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This patch is required to support kprobe on branch/call instructions.
Signed-off-by: NAnil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This patch adds IA64 architecture specific JProbes support on top of Kprobes
Signed-off-by: NAnil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: NRusty Lynch <Rusty.lynch@intel.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This is an IA64 arch specific handling of Kprobes
Signed-off-by: NAnil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: NRusty Lynch <Rusty.lynch@intel.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This patch adds function-return probes to kprobes for the i386
architecture.  This enables you to establish a handler to be run when a
function returns.

1. API

Two new functions are added to kprobes:

	int register_kretprobe(struct kretprobe *rp);
	void unregister_kretprobe(struct kretprobe *rp);

2. Registration and unregistration

2.1 Register

  To register a function-return probe, the user populates the following
  fields in a kretprobe object and calls register_kretprobe() with the
  kretprobe address as an argument:

  kp.addr - the function's address

  handler - this function is run after the ret instruction executes, but
  before control returns to the return address in the caller.

  maxactive - The maximum number of instances of the probed function that
  can be active concurrently.  For example, if the function is non-
  recursive and is called with a spinlock or mutex held, maxactive = 1
  should be enough.  If the function is non-recursive and can never
  relinquish the CPU (e.g., via a semaphore or preemption), NR_CPUS should
  be enough.  maxactive is used to determine how many kretprobe_instance
  objects to allocate for this particular probed function.  If maxactive <=
  0, it is set to a default value (if CONFIG_PREEMPT maxactive=max(10, 2 *
  NR_CPUS) else maxactive=NR_CPUS)

  For example:

    struct kretprobe rp;
    rp.kp.addr = /* entrypoint address */
    rp.handler = /*return probe handler */
    rp.maxactive = /* e.g., 1 or NR_CPUS or 0, see the above explanation */
    register_kretprobe(&rp);

  The following field may also be of interest:

  nmissed - Initialized to zero when the function-return probe is
  registered, and incremented every time the probed function is entered but
  there is no kretprobe_instance object available for establishing the
  function-return probe (i.e., because maxactive was set too low).

2.2 Unregister

  To unregiter a function-return probe, the user calls
  unregister_kretprobe() with the same kretprobe object as registered
  previously.  If a probed function is running when the return probe is
  unregistered, the function will return as expected, but the handler won't
  be run.

3. Limitations

3.1 This patch supports only the i386 architecture, but patches for
    x86_64 and ppc64 are anticipated soon.

3.2 Return probes operates by replacing the return address in the stack
    (or in a known register, such as the lr register for ppc).  This may
    cause __builtin_return_address(0), when invoked from the return-probed
    function, to return the address of the return-probes trampoline.

3.3 This implementation uses the "Multiprobes at an address" feature in
    2.6.12-rc3-mm3.

3.4 Due to a limitation in multi-probes, you cannot currently establish
    a return probe and a jprobe on the same function.  A patch to remove
    this limitation is being tested.

This feature is required by SystemTap (http://sourceware.org/systemtap),
and reflects ideas contributed by several SystemTap developers, including
Will Cohen and Ananth Mavinakayanahalli.
Signed-off-by: NHien Nguyen <hien@us.ibm.com>
Signed-off-by: NPrasanna S Panchamukhi <prasanna@in.ibm.com>
Signed-off-by: NFrederik Deweerdt <frederik.deweerdt@laposte.net>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!