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kernel-ark/include/linux/kprobes.h
Rusty Lynch 802eae7c80 [PATCH] Return probe redesign: architecture independent changes 
The following is the second version of the function return probe patches
I sent out earlier this week.  Changes since my last submission include:

* Fix in ppc64 code removing an unneeded call to re-enable preemption
* Fix a build problem in ia64 when kprobes was turned off
* Added another BUG_ON check to each of the architecture trampoline
  handlers

My initial patch description ==>

 From my experiences with adding return probes to x86_64 and ia64, and the
feedback on LKML to those patches, I think we can simplify the design
for return probes.

The following patch tweaks the original design such that:

* Instead of storing the stack address in the return probe instance, the
  task pointer is stored.  This gives us all we need in order to:
    - find the correct return probe instance when we enter the trampoline
      (even if we are recursing)
    - find all left-over return probe instances when the task is going away

  This has the side effect of simplifying the implementation since more
  work can be done in kernel/kprobes.c since architecture specific knowledge
  of the stack layout is no longer required.  Specifically, we no longer have:
	- arch_get_kprobe_task()
	- arch_kprobe_flush_task()
	- get_rp_inst_tsk()
	- get_rp_inst()
	- trampoline_post_handler() <see next bullet>

* Instead of splitting the return probe handling and cleanup logic across
  the pre and post trampoline handlers, all the work is pushed into the
  pre function (trampoline_probe_handler), and then we skip single stepping
  the original function.  In this case the original instruction to be single
  stepped was just a NOP, and we can do without the extra interruption.

The new flow of events to having a return probe handler execute when a target
function exits is:

* At system initialization time, a kprobe is inserted at the beginning of
  kretprobe_trampoline.  kernel/kprobes.c use to handle this on it's own,
  but ia64 needed to do this a little differently (i.e. a function pointer
  is really a pointer to a structure containing the instruction pointer and
  a global pointer), so I added the notion of arch_init(), so that
  kernel/kprobes.c:init_kprobes() now allows architecture specific
  initialization by calling arch_init() before exiting.  Each architecture
  now registers a kprobe on it's own trampoline function.

* register_kretprobe() will insert a kprobe at the beginning of the targeted
  function with the kprobe pre_handler set to arch_prepare_kretprobe
  (still no change)

* When the target function is entered, the kprobe is fired, calling
  arch_prepare_kretprobe (still no change)

* In arch_prepare_kretprobe() we try to get a free instance and if one is
  available then we fill out the instance with a pointer to the return probe,
  the original return address, and a pointer to the task structure (instead
  of the stack address.)  Just like before we change the return address
  to the trampoline function and mark the instance as used.

  If multiple return probes are registered for a given target function,
  then arch_prepare_kretprobe() will get called multiple times for the same
  task (since our kprobe implementation is able to handle multiple kprobes
  at the same address.)  Past the first call to arch_prepare_kretprobe,
  we end up with the original address stored in the return probe instance
  pointing to our trampoline function. (This is a significant difference
  from the original arch_prepare_kretprobe design.)

* Target function executes like normal and then returns to kretprobe_trampoline.

* kprobe inserted on the first instruction of kretprobe_trampoline is fired
  and calls trampoline_probe_handler() (no change here)

* trampoline_probe_handler() consumes each of the instances associated with
  the current task by calling the registered handler function and marking
  the instance as unused until an instance is found that has a return address
  different then the trampoline function.

  (change similar to my previous ia64 RFC)

* If the task is killed with some left-over return probe instances (meaning
  that a target function was entered, but never returned), then we just
  free any instances associated with the task.  (Not much different other
  then we can handle this without calling architecture specific functions.)

  There is a known problem that this patch does not yet solve where
  registering a return probe flush_old_exec or flush_thread will put us
  in a bad state.  Most likely the best way to handle this is to not allow
  registering return probes on these two functions.

  (Significant change)

This patch series applies to the 2.6.12-rc6-mm1 kernel, and provides:
  * kernel/kprobes.c changes
  * i386 patch of existing return probes implementation
  * x86_64 patch of existing return probe implementation
  * ia64 implementation
  * ppc64 implementation (provided by Ananth)

This patch implements the architecture independant changes for a reworking
of the kprobes based function return probes design. Changes include:

  * Removing functions for querying a return probe instance off a stack address
  * Removing the stack_addr field from the kretprobe_instance definition,
    and adding a task pointer
  * Adding architecture specific initialization via arch_init()
  * Removing extern definitions for the architecture trampoline functions
    (this isn't needed anymore since the architecture handles the
     initialization of the kprobe in the return probe trampoline function.)

Signed-off-by: Rusty Lynch <rusty.lynch@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-27 15:23:52 -07:00

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#ifndef _LINUX_KPROBES_H
#define _LINUX_KPROBES_H
/*
* Kernel Probes (KProbes)
* include/linux/kprobes.h
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* Copyright (C) IBM Corporation, 2002, 2004
*
* 2002-Oct Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
* Probes initial implementation ( includes suggestions from
* Rusty Russell).
* 2004-July Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
* interface to access function arguments.
* 2005-May Hien Nguyen <hien@us.ibm.com> and Jim Keniston
* <jkenisto@us.ibm.com> and Prasanna S Panchamukhi
* <prasanna@in.ibm.com> added function-return probes.
*/
#include <linux/config.h>
#include <linux/list.h>
#include <linux/notifier.h>
#include <linux/smp.h>
#include <asm/kprobes.h>
/* kprobe_status settings */
#define KPROBE_HIT_ACTIVE 0x00000001
#define KPROBE_HIT_SS 0x00000002
#define KPROBE_REENTER 0x00000004
#define KPROBE_HIT_SSDONE 0x00000008
struct kprobe;
struct pt_regs;
struct kretprobe;
struct kretprobe_instance;
typedef int (*kprobe_pre_handler_t) (struct kprobe *, struct pt_regs *);
typedef int (*kprobe_break_handler_t) (struct kprobe *, struct pt_regs *);
typedef void (*kprobe_post_handler_t) (struct kprobe *, struct pt_regs *,
unsigned long flags);
typedef int (*kprobe_fault_handler_t) (struct kprobe *, struct pt_regs *,
int trapnr);
typedef int (*kretprobe_handler_t) (struct kretprobe_instance *,
struct pt_regs *);
struct kprobe {
struct hlist_node hlist;
/* list of kprobes for multi-handler support */
struct list_head list;
/*count the number of times this probe was temporarily disarmed */
unsigned long nmissed;
/* location of the probe point */
kprobe_opcode_t *addr;
/* Called before addr is executed. */
kprobe_pre_handler_t pre_handler;
/* Called after addr is executed, unless... */
kprobe_post_handler_t post_handler;
/* ... called if executing addr causes a fault (eg. page fault).
* Return 1 if it handled fault, otherwise kernel will see it. */
kprobe_fault_handler_t fault_handler;
/* ... called if breakpoint trap occurs in probe handler.
* Return 1 if it handled break, otherwise kernel will see it. */
kprobe_break_handler_t break_handler;
/* Saved opcode (which has been replaced with breakpoint) */
kprobe_opcode_t opcode;
/* copy of the original instruction */
struct arch_specific_insn ainsn;
};
/*
* Special probe type that uses setjmp-longjmp type tricks to resume
* execution at a specified entry with a matching prototype corresponding
* to the probed function - a trick to enable arguments to become
* accessible seamlessly by probe handling logic.
* Note:
* Because of the way compilers allocate stack space for local variables
* etc upfront, regardless of sub-scopes within a function, this mirroring
* principle currently works only for probes placed on function entry points.
*/
struct jprobe {
struct kprobe kp;
kprobe_opcode_t *entry; /* probe handling code to jump to */
};
#ifdef ARCH_SUPPORTS_KRETPROBES
extern void arch_prepare_kretprobe(struct kretprobe *rp, struct pt_regs *regs);
#else /* ARCH_SUPPORTS_KRETPROBES */
static inline void arch_prepare_kretprobe(struct kretprobe *rp,
struct pt_regs *regs)
{
}
#endif /* ARCH_SUPPORTS_KRETPROBES */
/*
* Function-return probe -
* Note:
* User needs to provide a handler function, and initialize maxactive.
* maxactive - The maximum number of instances of the probed function that
* can be active concurrently.
* nmissed - tracks the number of times the probed function's return was
* ignored, due to maxactive being too low.
*
*/
struct kretprobe {
struct kprobe kp;
kretprobe_handler_t handler;
int maxactive;
int nmissed;
struct hlist_head free_instances;
struct hlist_head used_instances;
};
struct kretprobe_instance {
struct hlist_node uflist; /* either on free list or used list */
struct hlist_node hlist;
struct kretprobe *rp;
kprobe_opcode_t *ret_addr;
struct task_struct *task;
};
#ifdef CONFIG_KPROBES
/* Locks kprobe: irq must be disabled */
void lock_kprobes(void);
void unlock_kprobes(void);
/* kprobe running now on this CPU? */
static inline int kprobe_running(void)
{
extern unsigned int kprobe_cpu;
return kprobe_cpu == smp_processor_id();
}
extern int arch_prepare_kprobe(struct kprobe *p);
extern void arch_copy_kprobe(struct kprobe *p);
extern void arch_arm_kprobe(struct kprobe *p);
extern void arch_disarm_kprobe(struct kprobe *p);
extern void arch_remove_kprobe(struct kprobe *p);
extern int arch_init(void);
extern void show_registers(struct pt_regs *regs);
extern kprobe_opcode_t *get_insn_slot(void);
extern void free_insn_slot(kprobe_opcode_t *slot);
/* Get the kprobe at this addr (if any). Must have called lock_kprobes */
struct kprobe *get_kprobe(void *addr);
struct hlist_head * kretprobe_inst_table_head(struct task_struct *tsk);
int register_kprobe(struct kprobe *p);
void unregister_kprobe(struct kprobe *p);
int setjmp_pre_handler(struct kprobe *, struct pt_regs *);
int longjmp_break_handler(struct kprobe *, struct pt_regs *);
int register_jprobe(struct jprobe *p);
void unregister_jprobe(struct jprobe *p);
void jprobe_return(void);
int register_kretprobe(struct kretprobe *rp);
void unregister_kretprobe(struct kretprobe *rp);
struct kretprobe_instance *get_free_rp_inst(struct kretprobe *rp);
void add_rp_inst(struct kretprobe_instance *ri);
void kprobe_flush_task(struct task_struct *tk);
void recycle_rp_inst(struct kretprobe_instance *ri);
#else /* CONFIG_KPROBES */
static inline int kprobe_running(void)
{
return 0;
}
static inline int register_kprobe(struct kprobe *p)
{
return -ENOSYS;
}
static inline void unregister_kprobe(struct kprobe *p)
{
}
static inline int register_jprobe(struct jprobe *p)
{
return -ENOSYS;
}
static inline void unregister_jprobe(struct jprobe *p)
{
}
static inline void jprobe_return(void)
{
}
static inline int register_kretprobe(struct kretprobe *rp)
{
return -ENOSYS;
}
static inline void unregister_kretprobe(struct kretprobe *rp)
{
}
static inline void kprobe_flush_task(struct task_struct *tk)
{
}
#endif /* CONFIG_KPROBES */
#endif /* _LINUX_KPROBES_H */
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