Re: [PATCH v4 2/2] powerpc: Uprobes port to powerpc

Index: linux-tip-16aug/arch/powerpc/include/asm/uprobes.h
===================================================================

--- /dev/null
+++ linux-tip-16aug/arch/powerpc/include/asm/uprobes.h

@@ -0,0 +1,58 @@
+#ifndef _ASM_UPROBES_H
+#define _ASM_UPROBES_H
+/*
+ * User-space Probes (UProbes) for powerpc
+ *
+ * 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, 2007-2012

+#define MAX_UINSN_BYTES			4
+#define UPROBE_XOL_SLOT_BYTES		(MAX_UINSN_BYTES)
+
+#define UPROBE_SWBP_INSN		0x7fe00008

+#define UPROBE_SWBP_INSN_SIZE		4 /* swbp insn size in bytes */
+
+#define IS_TW(instr)		(((instr) & 0xfc0007fe) == 0x7c000008)
+#define IS_TD(instr)		(((instr) & 0xfc0007fe) == 0x7c000088)
+#define IS_TDI(instr)		(((instr) & 0xfc000000) == 0x08000000)
+#define IS_TWI(instr)		(((instr) & 0xfc000000) == 0x0c000000)
+
+#define is_trap(instr)	(IS_TW(instr) || IS_TD(instr) || \
+			IS_TWI(instr) || IS_TDI(instr))

+struct arch_uprobe {
+	u8	insn[MAX_UINSN_BYTES];
+};

Index: linux-tip-16aug/arch/powerpc/kernel/signal.c
===================================================================

--- linux-tip-16aug.orig/arch/powerpc/kernel/signal.c
+++ linux-tip-16aug/arch/powerpc/kernel/signal.c

@@ -11,6 +11,7 @@
 
 #include <linux/tracehook.h>
 #include <linux/signal.h>
+#include <linux/uprobes.h>
 #include <linux/key.h>
 #include <asm/hw_breakpoint.h>
 #include <asm/uaccess.h>

@@ -157,6 +158,11 @@ static int do_signal(struct pt_regs *reg
 
 void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags)
 {
+	if (thread_info_flags & _TIF_UPROBE) {
+		clear_thread_flag(TIF_UPROBE);
+		uprobe_notify_resume(regs);
+	}

 	if (thread_info_flags & _TIF_SIGPENDING)
 		do_signal(regs);
 
Index: linux-tip-16aug/arch/powerpc/kernel/uprobes.c
===================================================================

--- /dev/null
+++ linux-tip-16aug/arch/powerpc/kernel/uprobes.c

@@ -0,0 +1,180 @@
+/*
+ * User-space Probes (UProbes) for powerpc
+ *
+ * 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, 2007-2012
+ *
+ * Adapted from the x86 port by Ananth N Mavinakayanahalli <ananth@in.ibm.com>
+ */
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/ptrace.h>
+#include <linux/uprobes.h>
+#include <linux/uaccess.h>
+#include <linux/kdebug.h>
+
+#include <asm/sstep.h>
+
+#define UPROBE_TRAP_NR	UINT_MAX

+ * @mm: the probed address space.
+ * @arch_uprobe: the probepoint information.
+ * @addr: vaddr to probe.
+ * Return 0 on success or a -ve number on error.
+ */
+int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long addr)
+{
+	unsigned int insn;
+
+	if (addr & 0x03)
+		return -EINVAL;
+
+	memcpy(&insn, auprobe->insn, MAX_UINSN_BYTES);

+/*
+ * arch_uprobe_pre_xol - prepare to execute out of line.
+ * @auprobe: the probepoint information.
+ * @regs: reflects the saved user state of current task.
+ */
+int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+	struct arch_uprobe_task *autask = &current->utask->autask;
+
+	autask->saved_trap_nr = current->thread.trap_nr;
+	current->thread.trap_nr = UPROBE_TRAP_NR;
+	regs->nip = current->utask->xol_vaddr;
+	return 0;
+}
+
+/**
+ * uprobe_get_swbp_addr - compute address of swbp given post-swbp regs
+ * @regs: Reflects the saved state of the task after it has hit a breakpoint
+ * instruction.
+ * Return the address of the breakpoint instruction.
+ */
+unsigned long uprobe_get_swbp_addr(struct pt_regs *regs)
+{
+	return instruction_pointer(regs);
+}

+/*
+ * If xol insn itself traps and generates a signal (SIGILL/SIGSEGV/etc),
+ * then detect the case where a singlestepped instruction jumps back to its
+ * own address. It is assumed that anything like do_page_fault/do_trap/etc
+ * sets thread.trap_nr != -1.
+ *
+ * arch_uprobe_pre_xol/arch_uprobe_post_xol save/restore thread.trap_nr,
+ * arch_uprobe_xol_was_trapped() simply checks that ->trap_nr is not equal to
+ * UPROBE_TRAP_NR == -1 set by arch_uprobe_pre_xol().
+ */
+bool arch_uprobe_xol_was_trapped(struct task_struct *t)
+{
+	if (t->thread.trap_nr != UPROBE_TRAP_NR)
+		return true;
+
+	return false;
+}
+
+/*
+ * Called after single-stepping. 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.
+ *
+ * This function prepares to resume execution after the single-step.
+ */
+int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+	struct uprobe_task *utask = current->utask;
+
+	WARN_ON_ONCE(current->thread.trap_nr != UPROBE_TRAP_NR);
+
+	current->thread.trap_nr = utask->autask.saved_trap_nr;
+
+	/*
+	 * On powerpc, except for loads and stores, most instructions
+	 * including ones that alter code flow (branches, calls, returns)
+	 * are emulated in the kernel. We get here only if the emulation
+	 * support doesn't exist and have to fix-up the next instruction
+	 * to be executed.
+	 */
+	regs->nip = utask->vaddr + MAX_UINSN_BYTES;
+	return 0;
+}
+
+/* callback routine for handling exceptions. */
+int arch_uprobe_exception_notify(struct notifier_block *self, unsigned long val, void *data)
+{
+	struct die_args *args = data;
+	struct pt_regs *regs = args->regs;
+
+	/* We are only interested in userspace traps */
+	if (regs && !user_mode(regs))
+		return NOTIFY_DONE;

+	switch (val) {
+	case DIE_BPT:
+		if (uprobe_pre_sstep_notifier(regs))
+			return NOTIFY_STOP;
+		break;
+	case DIE_SSTEP:
+		if (uprobe_post_sstep_notifier(regs))
+			return NOTIFY_STOP;
+	default:
+		break;
+	}
+	return NOTIFY_DONE;
+}
+
+/*
+ * This function gets called when XOL instruction either gets trapped or
+ * the thread has a fatal signal, so reset the instruction pointer to its
+ * probed address.
+ */
+void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+	struct uprobe_task *utask = current->utask;
+
+	current->thread.trap_nr = utask->autask.saved_trap_nr;
+	instruction_pointer_set(regs, utask->vaddr);
+}
+
+/*
+ * See if the instruction can be emulated.
+ * Returns true if instruction was emulated, false otherwise.
+ */
+bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+	int ret;
+	unsigned int insn;
+
+	memcpy(&insn, auprobe->insn, MAX_UINSN_BYTES);

+
+	/*
+	 * emulate_step() returns 1 if the insn was successfully emulated.
+	 * For all other cases, we need to single-step in hardware.
+	 */
+	ret = emulate_step(regs, insn);
+	if (ret > 0)
+		return true;