1 files changed, 290 insertions, 0 deletions
diff --git a/arch/ppc64/kernel/kprobes.c b/arch/ppc64/kernel/kprobes.c
new file mode 100644
index 000000000000..103daaf73573
--- /dev/null
+++ b/arch/ppc64/kernel/kprobes.c
@@ -0,0 +1,290 @@
+/*
+ *  Kernel Probes (KProbes)
+ *  arch/ppc64/kernel/kprobes.c
+ *
+ * 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 contributions from
+ *		Rusty Russell).
+ * 2004-July	Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
+ *		interface to access function arguments.
+ * 2004-Nov	Ananth N Mavinakayanahalli <ananth@in.ibm.com> kprobes port
+ *		for PPC64
+ */
+
+#include <linux/config.h>
+#include <linux/kprobes.h>
+#include <linux/ptrace.h>
+#include <linux/spinlock.h>
+#include <linux/preempt.h>
+#include <asm/kdebug.h>
+#include <asm/sstep.h>
+
+/* kprobe_status settings */
+#define KPROBE_HIT_ACTIVE	0x00000001
+#define KPROBE_HIT_SS		0x00000002
+
+static struct kprobe *current_kprobe;
+static unsigned long kprobe_status, kprobe_saved_msr;
+static struct pt_regs jprobe_saved_regs;
+
+int arch_prepare_kprobe(struct kprobe *p)
+{
+	kprobe_opcode_t insn = *p->addr;
+
+	if (IS_MTMSRD(insn) || IS_RFID(insn))
+		/* cannot put bp on RFID/MTMSRD */
+		return 1;
+	return 0;
+}
+
+void arch_copy_kprobe(struct kprobe *p)
+{
+	memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
+}
+
+void arch_remove_kprobe(struct kprobe *p)
+{
+}
+
+static inline void disarm_kprobe(struct kprobe *p, struct pt_regs *regs)
+{
+	*p->addr = p->opcode;
+	regs->nip = (unsigned long)p->addr;
+}
+
+static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
+{
+	regs->msr |= MSR_SE;
+	/*single step inline if it a breakpoint instruction*/
+	if (p->opcode == BREAKPOINT_INSTRUCTION)
+		regs->nip = (unsigned long)p->addr;
+	else
+		regs->nip = (unsigned long)&p->ainsn.insn;
+}
+
+static inline int kprobe_handler(struct pt_regs *regs)
+{
+	struct kprobe *p;
+	int ret = 0;
+	unsigned int *addr = (unsigned int *)regs->nip;
+
+	/* Check we're not actually recursing */
+	if (kprobe_running()) {
+		/* We *are* holding lock here, so this is safe.
+		   Disarm the probe we just hit, and ignore it. */
+		p = get_kprobe(addr);
+		if (p) {
+			if (kprobe_status == KPROBE_HIT_SS) {
+				regs->msr &= ~MSR_SE;
+				regs->msr |= kprobe_saved_msr;
+				unlock_kprobes();
+				goto no_kprobe;
+			}
+			disarm_kprobe(p, regs);
+			ret = 1;
+		} else {
+			p = current_kprobe;
+			if (p->break_handler && p->break_handler(p, regs)) {
+				goto ss_probe;
+			}
+		}
+		/* If it's not ours, can't be delete race, (we hold lock). */
+		goto no_kprobe;
+	}
+
+	lock_kprobes();
+	p = get_kprobe(addr);
+	if (!p) {
+		unlock_kprobes();
+		if (*addr != BREAKPOINT_INSTRUCTION) {
+			/*
+			 * PowerPC has multiple variants of the "trap"
+			 * instruction. If the current instruction is a
+			 * trap variant, it could belong to someone else
+			 */
+			kprobe_opcode_t cur_insn = *addr;
+			if (IS_TW(cur_insn) || IS_TD(cur_insn) ||
+					IS_TWI(cur_insn) || IS_TDI(cur_insn))
+		       		goto no_kprobe;
+			/*
+			 * The breakpoint instruction was removed right
+			 * after we hit it.  Another cpu has removed
+			 * either a probepoint or a debugger breakpoint
+			 * at this address.  In either case, no further
+			 * handling of this interrupt is appropriate.
+			 */
+			ret = 1;
+		}
+		/* Not one of ours: let kernel handle it */
+		goto no_kprobe;
+	}
+
+	kprobe_status = KPROBE_HIT_ACTIVE;
+	current_kprobe = p;
+	kprobe_saved_msr = regs->msr;
+	if (p->pre_handler && p->pre_handler(p, regs))
+		/* handler has already set things up, so skip ss setup */
+		return 1;
+
+ss_probe:
+	prepare_singlestep(p, regs);
+	kprobe_status = KPROBE_HIT_SS;
+	/*
+	 * This preempt_disable() matches the preempt_enable_no_resched()
+	 * in post_kprobe_handler().
+	 */
+	preempt_disable();
+	return 1;
+
+no_kprobe:
+	return ret;
+}
+
+/*
+ * Called after single-stepping.  p->addr is the address of the
+ * instruction whose first byte has been replaced by the "breakpoint"
+ * instruction.  To avoid the SMP problems that can occur when we
+ * temporarily put back the original opcode to single-step, we
+ * single-stepped a copy of the instruction.  The address of this
+ * copy is p->ainsn.insn.
+ */
+static void resume_execution(struct kprobe *p, struct pt_regs *regs)
+{
+	int ret;
+
+	regs->nip = (unsigned long)p->addr;
+	ret = emulate_step(regs, p->ainsn.insn[0]);
+	if (ret == 0)
+		regs->nip = (unsigned long)p->addr + 4;
+
+	regs->msr &= ~MSR_SE;
+}
+
+static inline int post_kprobe_handler(struct pt_regs *regs)
+{
+	if (!kprobe_running())
+		return 0;
+
+	if (current_kprobe->post_handler)
+		current_kprobe->post_handler(current_kprobe, regs, 0);
+
+	resume_execution(current_kprobe, regs);
+	regs->msr |= kprobe_saved_msr;
+
+	unlock_kprobes();
+	preempt_enable_no_resched();
+
+	/*
+	 * if somebody else is singlestepping across a probe point, msr
+	 * will have SE set, in which case, continue the remaining processing
+	 * of do_debug, as if this is not a probe hit.
+	 */
+	if (regs->msr & MSR_SE)
+		return 0;
+
+	return 1;
+}
+
+/* Interrupts disabled, kprobe_lock held. */
+static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
+{
+	if (current_kprobe->fault_handler
+	    && current_kprobe->fault_handler(current_kprobe, regs, trapnr))
+		return 1;
+
+	if (kprobe_status & KPROBE_HIT_SS) {
+		resume_execution(current_kprobe, regs);
+		regs->msr |= kprobe_saved_msr;
+
+		unlock_kprobes();
+		preempt_enable_no_resched();
+	}
+	return 0;
+}
+
+/*
+ * Wrapper routine to for handling exceptions.
+ */
+int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val,
+			     void *data)
+{
+	struct die_args *args = (struct die_args *)data;
+	int ret = NOTIFY_DONE;
+
+	/*
+	 * Interrupts are not disabled here.  We need to disable
+	 * preemption, because kprobe_running() uses smp_processor_id().
+	 */
+	preempt_disable();
+	switch (val) {
+	case DIE_IABR_MATCH:
+	case DIE_DABR_MATCH:
+	case DIE_BPT:
+		if (kprobe_handler(args->regs))
+			ret = NOTIFY_STOP;
+		break;
+	case DIE_SSTEP:
+		if (post_kprobe_handler(args->regs))
+			ret = NOTIFY_STOP;
+		break;
+	case DIE_GPF:
+	case DIE_PAGE_FAULT:
+		if (kprobe_running() &&
+		    kprobe_fault_handler(args->regs, args->trapnr))
+			ret = NOTIFY_STOP;
+		break;
+	default:
+		break;
+	}
+	preempt_enable();
+	return ret;
+}
+
+int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
+{
+	struct jprobe *jp = container_of(p, struct jprobe, kp);
+
+	memcpy(&jprobe_saved_regs, regs, sizeof(struct pt_regs));
+
+	/* setup return addr to the jprobe handler routine */
+	regs->nip = (unsigned long)(((func_descr_t *)jp->entry)->entry);
+	regs->gpr[2] = (unsigned long)(((func_descr_t *)jp->entry)->toc);
+
+	return 1;
+}
+
+void jprobe_return(void)
+{
+	asm volatile("trap" ::: "memory");
+}
+
+void jprobe_return_end(void)
+{
+};
+
+int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
+{
+	/*
+	 * FIXME - we should ideally be validating that we got here 'cos
+	 * of the "trap" in jprobe_return() above, before restoring the
+	 * saved regs...
+	 */
+	memcpy(regs, &jprobe_saved_regs, sizeof(struct pt_regs));
+	return 1;
+}