ARC: kprobes support

Origin port done by Rajeshwar Ranga
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Cc: Rajeshwar Ranga <rajeshwar.ranga@gmail.com>

arch/arc/Kconfig

@@ -24,6 +24,8 @@ config ARC
 	select GENERIC_SMP_IDLE_THREAD
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_GENERIC_HARDIRQS
+	select HAVE_KPROBES
+	select HAVE_KRETPROBES
 	select HAVE_MEMBLOCK
 	select HAVE_MOD_ARCH_SPECIFIC if ARC_DW2_UNWIND
 	select HAVE_OPROFILE

arch/arc/include/asm/kprobes.h

+/*
+ * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef _ARC_KPROBES_H
+#define _ARC_KPROBES_H
+
+#ifdef CONFIG_KPROBES
+
+typedef u16 kprobe_opcode_t;
+
+#define UNIMP_S_INSTRUCTION 0x79e0
+#define TRAP_S_2_INSTRUCTION 0x785e
+
+#define MAX_INSN_SIZE   8
+#define MAX_STACK_SIZE  64
+
+struct arch_specific_insn {
+	int is_short;
+	kprobe_opcode_t *t1_addr, *t2_addr;
+	kprobe_opcode_t t1_opcode, t2_opcode;
+};
+
+#define flush_insn_slot(p)  do {  } while (0)
+
+#define kretprobe_blacklist_size    0
+
+struct kprobe;
+
+void arch_remove_kprobe(struct kprobe *p);
+
+int kprobe_exceptions_notify(struct notifier_block *self,
+			     unsigned long val, void *data);
+
+struct prev_kprobe {
+	struct kprobe *kp;
+	unsigned long status;
+};
+
+struct kprobe_ctlblk {
+	unsigned int kprobe_status;
+	struct pt_regs jprobe_saved_regs;
+	char jprobes_stack[MAX_STACK_SIZE];
+	struct prev_kprobe prev_kprobe;
+};
+
+int kprobe_fault_handler(struct pt_regs *regs, unsigned long cause);
+void kretprobe_trampoline(void);
+void trap_is_kprobe(unsigned long cause, unsigned long address,
+			   struct pt_regs *regs);
+#else
+static void trap_is_kprobe(unsigned long cause, unsigned long address,
+			   struct pt_regs *regs)
+{
+}
+#endif
+
+#endif

arch/arc/include/asm/ptrace.h

@@ -111,6 +111,11 @@ struct callee_regs {
 	(struct pt_regs *)(pg_start + THREAD_SIZE - 4) - 1;	\
 })
 
+static inline long regs_return_value(struct pt_regs *regs)
+{
+	return regs->r0;
+}
+
 #endif /* !__ASSEMBLY__ */
 
 #define orig_r8_IS_SCALL		0x0001

arch/arc/kernel/Makefile

@@ -15,6 +15,7 @@ obj-y	+= devtree.o
 obj-$(CONFIG_MODULES)			+= arcksyms.o module.o
 obj-$(CONFIG_SMP) 			+= smp.o
 obj-$(CONFIG_ARC_DW2_UNWIND)		+= unwind.o
+obj-$(CONFIG_KPROBES)      		+= kprobes.o
 
 obj-$(CONFIG_ARC_FPU_SAVE_RESTORE)	+= fpu.o
 CFLAGS_fpu.o   += -mdpfp

arch/arc/kernel/disasm.c

@@ -497,9 +497,8 @@ void __kprobes set_reg(int reg, long val, struct pt_regs *regs,
  * @pc +2/4/6 (ARCompact ISA allows free intermixing of 16/32 bit insns).
  *
  * If @pc is a branch
- * 	-@tgt_if_br is set to branch target.
- * 	-If branch has delay slot, @next_pc updated with actual next PC.
- *
+ *	-@tgt_if_br is set to branch target.
+ *	-If branch has delay slot, @next_pc updated with actual next PC.
  */
 int __kprobes disasm_next_pc(unsigned long pc, struct pt_regs *regs,
 			     struct callee_regs *cregs,

arch/arc/kernel/traps.c

@@ -15,6 +15,7 @@
 #include <linux/uaccess.h>
 #include <asm/ptrace.h>
 #include <asm/setup.h>
+#include <asm/kprobes.h>
 
 void __init trap_init(void)
 {
@@ -90,6 +91,7 @@ void do_machine_check_fault(unsigned long cause, unsigned long address,
 	die("Machine Check Exception", regs, address, cause);
 }
 
+
 /*
  * Entry point for traps induced by ARCompact TRAP_S <n> insn
  * This is same family as TRAP0/SWI insn (use the same vector).
@@ -109,6 +111,10 @@ void do_non_swi_trap(unsigned long cause, unsigned long address,
 		trap_is_brkpt(cause, address, regs);
 		break;
 
+	case 2:
+		trap_is_kprobe(param, address, regs);
+		break;
+
 	default:
 		break;
 	}
@@ -116,10 +122,17 @@ void do_non_swi_trap(unsigned long cause, unsigned long address,
 
 /*
  * Entry point for Instruction Error Exception
+ *  -For a corner case, ARC kprobes implementation resorts to using
+ *   this exception, hence the check
  */
 void do_insterror_or_kprobe(unsigned long cause,
 				       unsigned long address,
 				       struct pt_regs *regs)
 {
+	/* Check if this exception is caused by kprobes */
+	if (notify_die(DIE_IERR, "kprobe_ierr", regs, address,
+		       cause, SIGILL) == NOTIFY_STOP)
+		return;
+
 	insterror_is_error(cause, address, regs);
 }