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/*
* Jprobe specific operations
*
* 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) Intel Corporation, 2005
*
* 2005-May Rusty Lynch <rusty.lynch@intel.com> and Anil S Keshavamurthy
* <anil.s.keshavamurthy@intel.com> initial implementation
*
* Jprobes (a.k.a. "jump probes" which is built on-top of kprobes) allow a
* probe to be inserted into the beginning of a function call. The fundamental
* difference between a jprobe and a kprobe is the jprobe handler is executed
* in the same context as the target function, while the kprobe handlers
* are executed in interrupt context.
*
* For jprobes we initially gain control by placing a break point in the
* first instruction of the targeted function. When we catch that specific
* break, we:
* * set the return address to our jprobe_inst_return() function
* * jump to the jprobe handler function
*
* Since we fixed up the return address, the jprobe handler will return to our
* jprobe_inst_return() function, giving us control again. At this point we
* are back in the parents frame marker, so we do yet another call to our
* jprobe_break() function to fix up the frame marker as it would normally
* exist in the target function.
*
* Our jprobe_return function then transfers control back to kprobes.c by
* executing a break instruction using one of our reserved numbers. When we
* catch that break in kprobes.c, we continue like we do for a normal kprobe
* by single stepping the emulated instruction, and then returning execution
* to the correct location.
*/
#include <asm/asmmacro.h>
/*
* void jprobe_break(void)
*/
ENTRY(jprobe_break)
break.m 0x80300
END(jprobe_break)
/*
* void jprobe_inst_return(void)
*/
GLOBAL_ENTRY(jprobe_inst_return)
br.call.sptk.many b0=jprobe_break
END(jprobe_inst_return)
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