1/*
2 * Jprobe specific operations
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
17 *
18 * Copyright (C) Intel Corporation, 2005
19 *
20 * 2005-May     Rusty Lynch <rusty.lynch@intel.com> and Anil S Keshavamurthy
21 *              <anil.s.keshavamurthy@intel.com> initial implementation
22 *
23 * Jprobes (a.k.a. "jump probes" which is built on-top of kprobes) allow a
24 * probe to be inserted into the beginning of a function call.  The fundamental
25 * difference between a jprobe and a kprobe is the jprobe handler is executed
26 * in the same context as the target function, while the kprobe handlers
27 * are executed in interrupt context.
28 *
29 * For jprobes we initially gain control by placing a break point in the
30 * first instruction of the targeted function.  When we catch that specific
31 * break, we:
32 *        * set the return address to our jprobe_inst_return() function
33 *        * jump to the jprobe handler function
34 *
35 * Since we fixed up the return address, the jprobe handler will return to our
36 * jprobe_inst_return() function, giving us control again.  At this point we
37 * are back in the parents frame marker, so we do yet another call to our
38 * jprobe_break() function to fix up the frame marker as it would normally
39 * exist in the target function.
40 *
41 * Our jprobe_return function then transfers control back to kprobes.c by
42 * executing a break instruction using one of our reserved numbers.  When we
43 * catch that break in kprobes.c, we continue like we do for a normal kprobe
44 * by single stepping the emulated instruction, and then returning execution
45 * to the correct location.
46 */
47#include <asm/asmmacro.h>
48#include <asm/break.h>
49
50	/*
51	 * void jprobe_break(void)
52	 */
53	.section .kprobes.text, "ax"
54ENTRY(jprobe_break)
55	break.m __IA64_BREAK_JPROBE
56END(jprobe_break)
57
58	/*
59	 * void jprobe_inst_return(void)
60	 */
61GLOBAL_ENTRY(jprobe_inst_return)
62	br.call.sptk.many b0=jprobe_break
63END(jprobe_inst_return)
64
65GLOBAL_ENTRY(invalidate_stacked_regs)
66	movl r16=invalidate_restore_cfm
67	;;
68	mov b6=r16
69	;;
70	br.ret.sptk.many b6
71	;;
72invalidate_restore_cfm:
73	mov r16=ar.rsc
74	;;
75	mov ar.rsc=r0
76	;;
77	loadrs
78	;;
79	mov ar.rsc=r16
80	;;
81	br.cond.sptk.many rp
82END(invalidate_stacked_regs)
83
84GLOBAL_ENTRY(flush_register_stack)
85	// flush dirty regs to backing store (must be first in insn group)
86	flushrs
87	;;
88	br.ret.sptk.many rp
89END(flush_register_stack)
90
91