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