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authorAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
committerAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
commit57f0f512b273f60d52568b8c6b77e17f5636edc0 (patch)
tree5e910f0e82173f4ef4f51111366a3f1299037a7b /arch/ia64/kernel/jprobes.S
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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>
+#include <asm/break.h>
+
+ /*
+ * void jprobe_break(void)
+ */
+ .section .kprobes.text, "ax"
+ENTRY(jprobe_break)
+ break.m __IA64_BREAK_JPROBE
+END(jprobe_break)
+
+ /*
+ * void jprobe_inst_return(void)
+ */
+GLOBAL_ENTRY(jprobe_inst_return)
+ br.call.sptk.many b0=jprobe_break
+END(jprobe_inst_return)
+
+GLOBAL_ENTRY(invalidate_stacked_regs)
+ movl r16=invalidate_restore_cfm
+ ;;
+ mov b6=r16
+ ;;
+ br.ret.sptk.many b6
+ ;;
+invalidate_restore_cfm:
+ mov r16=ar.rsc
+ ;;
+ mov ar.rsc=r0
+ ;;
+ loadrs
+ ;;
+ mov ar.rsc=r16
+ ;;
+ br.cond.sptk.many rp
+END(invalidate_stacked_regs)
+
+GLOBAL_ENTRY(flush_register_stack)
+ // flush dirty regs to backing store (must be first in insn group)
+ flushrs
+ ;;
+ br.ret.sptk.many rp
+END(flush_register_stack)
+