arm64: Exception handling

The patch contains the exception entry code (kernel/entry.S), pt_regs
structure and related accessors, undefined instruction trapping and
stack tracing.

AArch64 Linux kernel (including kernel threads) runs in EL1 mode using
the SP1 stack. The vectors don't have a fixed address, only alignment
(2^11) requirements.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>

arch/arm64/include/asm/ptrace.h

+/*
+ * Based on arch/arm/include/asm/ptrace.h
+ *
+ * Copyright (C) 1996-2003 Russell King
+ * Copyright (C) 2012 ARM Ltd.
+ *
+ * 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.
+ *
+ * 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, see <http://www.gnu.org/licenses/>.
+ */
+#ifndef __ASM_PTRACE_H
+#define __ASM_PTRACE_H
+
+#include <linux/types.h>
+
+#include <asm/hwcap.h>
+
+#define PTRACE_GETREGS		12
+#define PTRACE_SETREGS		13
+#define PTRACE_GETFPSIMDREGS	14
+#define PTRACE_SETFPSIMDREGS	15
+/* PTRACE_ATTACH is 16 */
+/* PTRACE_DETACH is 17 */
+#define PTRACE_GET_THREAD_AREA	22
+#define PTRACE_SET_SYSCALL	23
+#define PTRACE_GETHBPREGS	29
+#define PTRACE_SETHBPREGS	30
+
+/* AArch32-specific ptrace requests */
+#define COMPAT_PTRACE_GETVFPREGS	27
+#define COMPAT_PTRACE_SETVFPREGS	28
+
+/*
+ * PSR bits
+ */
+#define PSR_MODE_EL0t	0x00000000
+#define PSR_MODE_EL1t	0x00000004
+#define PSR_MODE_EL1h	0x00000005
+#define PSR_MODE_EL2t	0x00000008
+#define PSR_MODE_EL2h	0x00000009
+#define PSR_MODE_EL3t	0x0000000c
+#define PSR_MODE_EL3h	0x0000000d
+#define PSR_MODE_MASK	0x0000000f
+
+/* AArch32 CPSR bits */
+#define PSR_MODE32_BIT		0x00000010
+#define COMPAT_PSR_MODE_USR	0x00000010
+#define COMPAT_PSR_T_BIT	0x00000020
+#define COMPAT_PSR_IT_MASK	0x0600fc00	/* If-Then execution state mask */
+
+/* AArch64 SPSR bits */
+#define PSR_F_BIT	0x00000040
+#define PSR_I_BIT	0x00000080
+#define PSR_A_BIT	0x00000100
+#define PSR_D_BIT	0x00000200
+#define PSR_Q_BIT	0x08000000
+#define PSR_V_BIT	0x10000000
+#define PSR_C_BIT	0x20000000
+#define PSR_Z_BIT	0x40000000
+#define PSR_N_BIT	0x80000000
+
+/*
+ * Groups of PSR bits
+ */
+#define PSR_f		0xff000000	/* Flags		*/
+#define PSR_s		0x00ff0000	/* Status		*/
+#define PSR_x		0x0000ff00	/* Extension		*/
+#define PSR_c		0x000000ff	/* Control		*/
+
+/*
+ * These are 'magic' values for PTRACE_PEEKUSR that return info about where a
+ * process is located in memory.
+ */
+#define PT_TEXT_ADDR		0x10000
+#define PT_DATA_ADDR		0x10004
+#define PT_TEXT_END_ADDR	0x10008
+
+#ifndef __ASSEMBLY__
+
+/*
+ * User structures for general purpose, floating point and debug registers.
+ */
+struct user_pt_regs {
+	__u64		regs[31];
+	__u64		sp;
+	__u64		pc;
+	__u64		pstate;
+};
+
+struct user_fpsimd_state {
+	__uint128_t	vregs[32];
+	__u32		fpsr;
+	__u32		fpcr;
+};
+
+struct user_hwdebug_state {
+	__u32		dbg_info;
+	struct {
+		__u64	addr;
+		__u32	ctrl;
+	}		dbg_regs[16];
+};
+
+#ifdef __KERNEL__
+
+/* sizeof(struct user) for AArch32 */
+#define COMPAT_USER_SZ	296
+/* AArch32 uses x13 as the stack pointer... */
+#define compat_sp	regs[13]
+/* ... and x14 as the link register. */
+#define compat_lr	regs[14]
+
+/*
+ * This struct defines the way the registers are stored on the stack during an
+ * exception. Note that sizeof(struct pt_regs) has to be a multiple of 16 (for
+ * stack alignment). struct user_pt_regs must form a prefix of struct pt_regs.
+ */
+struct pt_regs {
+	union {
+		struct user_pt_regs user_regs;
+		struct {
+			u64 regs[31];
+			u64 sp;
+			u64 pc;
+			u64 pstate;
+		};
+	};
+	u64 orig_x0;
+	u64 syscallno;
+};
+
+#define arch_has_single_step()	(1)
+
+#ifdef CONFIG_COMPAT
+#define compat_thumb_mode(regs) \
+	(((regs)->pstate & COMPAT_PSR_T_BIT))
+#else
+#define compat_thumb_mode(regs) (0)
+#endif
+
+#define user_mode(regs)	\
+	(((regs)->pstate & PSR_MODE_MASK) == PSR_MODE_EL0t)
+
+#define compat_user_mode(regs)	\
+	(((regs)->pstate & (PSR_MODE32_BIT | PSR_MODE_MASK)) == \
+	 (PSR_MODE32_BIT | PSR_MODE_EL0t))
+
+#define processor_mode(regs) \
+	((regs)->pstate & PSR_MODE_MASK)
+
+#define interrupts_enabled(regs) \
+	(!((regs)->pstate & PSR_I_BIT))
+
+#define fast_interrupts_enabled(regs) \
+	(!((regs)->pstate & PSR_F_BIT))
+
+#define user_stack_pointer(regs) \
+	((regs)->sp)
+
+/*
+ * Are the current registers suitable for user mode? (used to maintain
+ * security in signal handlers)
+ */
+static inline int valid_user_regs(struct user_pt_regs *regs)
+{
+	if (user_mode(regs) && (regs->pstate & PSR_I_BIT) == 0) {
+		regs->pstate &= ~(PSR_F_BIT | PSR_A_BIT);
+
+		/* The T bit is reserved for AArch64 */
+		if (!(regs->pstate & PSR_MODE32_BIT))
+			regs->pstate &= ~COMPAT_PSR_T_BIT;
+
+		return 1;
+	}
+
+	/*
+	 * Force PSR to something logical...
+	 */
+	regs->pstate &= PSR_f | PSR_s | (PSR_x & ~PSR_A_BIT) | \
+			COMPAT_PSR_T_BIT | PSR_MODE32_BIT;
+
+	if (!(regs->pstate & PSR_MODE32_BIT)) {
+		regs->pstate &= ~COMPAT_PSR_T_BIT;
+		regs->pstate |= PSR_MODE_EL0t;
+	}
+
+	return 0;
+}
+
+#define instruction_pointer(regs)	(regs)->pc
+
+#ifdef CONFIG_SMP
+extern unsigned long profile_pc(struct pt_regs *regs);
+#else
+#define profile_pc(regs) instruction_pointer(regs)
+#endif
+
+extern int aarch32_break_trap(struct pt_regs *regs);
+
+#endif /* __KERNEL__ */
+
+#endif /* __ASSEMBLY__ */
+
+#endif

arch/arm64/include/asm/stacktrace.h

+/*
+ * Copyright (C) 2012 ARM Ltd.
+ *
+ * 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.
+ *
+ * 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, see <http://www.gnu.org/licenses/>.
+ */
+#ifndef __ASM_STACKTRACE_H
+#define __ASM_STACKTRACE_H
+
+struct stackframe {
+	unsigned long fp;
+	unsigned long sp;
+	unsigned long pc;
+};
+
+extern int unwind_frame(struct stackframe *frame);
+extern void walk_stackframe(struct stackframe *frame,
+			    int (*fn)(struct stackframe *, void *), void *data);
+
+#endif	/* __ASM_STACKTRACE_H */

arch/arm64/include/asm/traps.h

+/*
+ * Based on arch/arm/include/asm/traps.h
+ *
+ * Copyright (C) 2012 ARM Ltd.
+ *
+ * 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.
+ *
+ * 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, see <http://www.gnu.org/licenses/>.
+ */
+#ifndef __ASM_TRAP_H
+#define __ASM_TRAP_H
+
+static inline int in_exception_text(unsigned long ptr)
+{
+	extern char __exception_text_start[];
+	extern char __exception_text_end[];
+
+	return ptr >= (unsigned long)&__exception_text_start &&
+	       ptr < (unsigned long)&__exception_text_end;
+}
+
+#endif

arch/arm64/kernel/stacktrace.c

+/*
+ * Stack tracing support
+ *
+ * Copyright (C) 2012 ARM Ltd.
+ *
+ * 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.
+ *
+ * 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, see <http://www.gnu.org/licenses/>.
+ */
+#include <linux/kernel.h>
+#include <linux/export.h>
+#include <linux/sched.h>
+#include <linux/stacktrace.h>
+
+#include <asm/stacktrace.h>
+
+/*
+ * AArch64 PCS assigns the frame pointer to x29.
+ *
+ * A simple function prologue looks like this:
+ * 	sub	sp, sp, #0x10
+ *   	stp	x29, x30, [sp]
+ *	mov	x29, sp
+ *
+ * A simple function epilogue looks like this:
+ *	mov	sp, x29
+ *	ldp	x29, x30, [sp]
+ *	add	sp, sp, #0x10
+ */
+int unwind_frame(struct stackframe *frame)
+{
+	unsigned long high, low;
+	unsigned long fp = frame->fp;
+
+	low  = frame->sp;
+	high = ALIGN(low, THREAD_SIZE);
+
+	if (fp < low || fp > high || fp & 0xf)
+		return -EINVAL;
+
+	frame->sp = fp + 0x10;
+	frame->fp = *(unsigned long *)(fp);
+	frame->pc = *(unsigned long *)(fp + 8);
+
+	return 0;
+}
+
+void notrace walk_stackframe(struct stackframe *frame,
+		     int (*fn)(struct stackframe *, void *), void *data)
+{
+	while (1) {
+		int ret;
+
+		if (fn(frame, data))
+			break;
+		ret = unwind_frame(frame);
+		if (ret < 0)
+			break;
+	}
+}
+EXPORT_SYMBOL(walk_stackframe);
+
+#ifdef CONFIG_STACKTRACE
+struct stack_trace_data {
+	struct stack_trace *trace;
+	unsigned int no_sched_functions;
+	unsigned int skip;
+};
+
+static int save_trace(struct stackframe *frame, void *d)
+{
+	struct stack_trace_data *data = d;
+	struct stack_trace *trace = data->trace;
+	unsigned long addr = frame->pc;
+
+	if (data->no_sched_functions && in_sched_functions(addr))
+		return 0;
+	if (data->skip) {
+		data->skip--;
+		return 0;
+	}
+
+	trace->entries[trace->nr_entries++] = addr;
+
+	return trace->nr_entries >= trace->max_entries;
+}
+
+void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
+{
+	struct stack_trace_data data;
+	struct stackframe frame;
+
+	data.trace = trace;
+	data.skip = trace->skip;
+
+	if (tsk != current) {
+		data.no_sched_functions = 1;
+		frame.fp = thread_saved_fp(tsk);
+		frame.sp = thread_saved_sp(tsk);
+		frame.pc = thread_saved_pc(tsk);
+	} else {
+		register unsigned long current_sp asm("sp");
+		data.no_sched_functions = 0;
+		frame.fp = (unsigned long)__builtin_frame_address(0);
+		frame.sp = current_sp;
+		frame.pc = (unsigned long)save_stack_trace_tsk;
+	}
+
+	walk_stackframe(&frame, save_trace, &data);
+	if (trace->nr_entries < trace->max_entries)
+		trace->entries[trace->nr_entries++] = ULONG_MAX;
+}
+
+void save_stack_trace(struct stack_trace *trace)
+{
+	save_stack_trace_tsk(current, trace);
+}
+EXPORT_SYMBOL_GPL(save_stack_trace);
+#endif

arch/arm64/kernel/traps.c

+/*
+ * Based on arch/arm/kernel/traps.c
+ *
+ * Copyright (C) 1995-2009 Russell King
+ * Copyright (C) 2012 ARM Ltd.
+ *
+ * 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.
+ *
+ * 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, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/signal.h>
+#include <linux/personality.h>
+#include <linux/kallsyms.h>
+#include <linux/spinlock.h>
+#include <linux/uaccess.h>
+#include <linux/hardirq.h>
+#include <linux/kdebug.h>
+#include <linux/module.h>
+#include <linux/kexec.h>
+#include <linux/delay.h>
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/syscalls.h>
+
+#include <asm/atomic.h>
+#include <asm/traps.h>
+#include <asm/stacktrace.h>
+#include <asm/exception.h>
+#include <asm/system_misc.h>
+
+static const char *handler[]= {
+	"Synchronous Abort",
+	"IRQ",
+	"FIQ",
+	"Error"
+};
+
+int show_unhandled_signals = 1;
+
+/*
+ * Dump out the contents of some memory nicely...
+ */
+static void dump_mem(const char *lvl, const char *str, unsigned long bottom,
+		     unsigned long top)
+{
+	unsigned long first;
+	mm_segment_t fs;
+	int i;
+
+	/*
+	 * We need to switch to kernel mode so that we can use __get_user
+	 * to safely read from kernel space.  Note that we now dump the
+	 * code first, just in case the backtrace kills us.
+	 */
+	fs = get_fs();
+	set_fs(KERNEL_DS);
+
+	printk("%s%s(0x%016lx to 0x%016lx)\n", lvl, str, bottom, top);
+
+	for (first = bottom & ~31; first < top; first += 32) {
+		unsigned long p;
+		char str[sizeof(" 12345678") * 8 + 1];
+
+		memset(str, ' ', sizeof(str));
+		str[sizeof(str) - 1] = '\0';
+
+		for (p = first, i = 0; i < 8 && p < top; i++, p += 4) {
+			if (p >= bottom && p < top) {
+				unsigned int val;
+				if (__get_user(val, (unsigned int *)p) == 0)
+					sprintf(str + i * 9, " %08x", val);
+				else
+					sprintf(str + i * 9, " ????????");
+			}
+		}
+		printk("%s%04lx:%s\n", lvl, first & 0xffff, str);
+	}
+
+	set_fs(fs);
+}
+
+static void dump_backtrace_entry(unsigned long where, unsigned long stack)
+{
+	print_ip_sym(where);
+	if (in_exception_text(where))
+		dump_mem("", "Exception stack", stack,
+			 stack + sizeof(struct pt_regs));
+}
+
+static void dump_instr(const char *lvl, struct pt_regs *regs)
+{
+	unsigned long addr = instruction_pointer(regs);
+	mm_segment_t fs;
+	char str[sizeof("00000000 ") * 5 + 2 + 1], *p = str;
+	int i;
+
+	/*
+	 * We need to switch to kernel mode so that we can use __get_user
+	 * to safely read from kernel space.  Note that we now dump the
+	 * code first, just in case the backtrace kills us.
+	 */
+	fs = get_fs();
+	set_fs(KERNEL_DS);
+
+	for (i = -4; i < 1; i++) {
+		unsigned int val, bad;
+
+		bad = __get_user(val, &((u32 *)addr)[i]);
+
+		if (!bad)
+			p += sprintf(p, i == 0 ? "(%08x) " : "%08x ", val);
+		else {
+			p += sprintf(p, "bad PC value");
+			break;
+		}
+	}
+	printk("%sCode: %s\n", lvl, str);
+
+	set_fs(fs);
+}
+
+static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
+{
+	struct stackframe frame;
+	const register unsigned long current_sp asm ("sp");
+
+	pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
+
+	if (!tsk)
+		tsk = current;
+
+	if (regs) {
+		frame.fp = regs->regs[29];
+		frame.sp = regs->sp;
+		frame.pc = regs->pc;
+	} else if (tsk == current) {
+		frame.fp = (unsigned long)__builtin_frame_address(0);
+		frame.sp = current_sp;
+		frame.pc = (unsigned long)dump_backtrace;
+	} else {
+		/*
+		 * task blocked in __switch_to
+		 */
+		frame.fp = thread_saved_fp(tsk);
+		frame.sp = thread_saved_sp(tsk);
+		frame.pc = thread_saved_pc(tsk);
+	}
+
+	printk("Call trace:\n");
+	while (1) {
+		unsigned long where = frame.pc;
+		int ret;
+
+		ret = unwind_frame(&frame);
+		if (ret < 0)
+			break;
+		dump_backtrace_entry(where, frame.sp);
+	}
+}
+
+void dump_stack(void)
+{
+	dump_backtrace(NULL, NULL);
+}
+
+EXPORT_SYMBOL(dump_stack);
+
+void show_stack(struct task_struct *tsk, unsigned long *sp)
+{
+	dump_backtrace(NULL, tsk);
+	barrier();
+}
+
+#ifdef CONFIG_PREEMPT
+#define S_PREEMPT " PREEMPT"
+#else
+#define S_PREEMPT ""
+#endif
+#ifdef CONFIG_SMP
+#define S_SMP " SMP"
+#else
+#define S_SMP ""
+#endif
+
+static int __die(const char *str, int err, struct thread_info *thread,
+		 struct pt_regs *regs)
+{
+	struct task_struct *tsk = thread->task;
+	static int die_counter;
+	int ret;
+
+	pr_emerg("Internal error: %s: %x [#%d]" S_PREEMPT S_SMP "\n",
+		 str, err, ++die_counter);
+
+	/* trap and error numbers are mostly meaningless on ARM */
+	ret = notify_die(DIE_OOPS, str, regs, err, 0, SIGSEGV);
+	if (ret == NOTIFY_STOP)
+		return ret;
+
+	print_modules();
+	__show_regs(regs);
+	pr_emerg("Process %.*s (pid: %d, stack limit = 0x%p)\n",
+		 TASK_COMM_LEN, tsk->comm, task_pid_nr(tsk), thread + 1);
+
+	if (!user_mode(regs) || in_interrupt()) {
+		dump_mem(KERN_EMERG, "Stack: ", regs->sp,
+			 THREAD_SIZE + (unsigned long)task_stack_page(tsk));
+		dump_backtrace(regs, tsk);
+		dump_instr(KERN_EMERG, regs);
+	}
+
+	return ret;
+}
+
+static DEFINE_RAW_SPINLOCK(die_lock);
+
+/*
+ * This function is protected against re-entrancy.
+ */
+void die(const char *str, struct pt_regs *regs, int err)
+{
+	struct thread_info *thread = current_thread_info();
+	int ret;
+
+	oops_enter();
+
+	raw_spin_lock_irq(&die_lock);
+	console_verbose();
+	bust_spinlocks(1);
+	ret = __die(str, err, thread, regs);
+
+	if (regs && kexec_should_crash(thread->task))
+		crash_kexec(regs);
+
+	bust_spinlocks(0);
+	add_taint(TAINT_DIE);
+	raw_spin_unlock_irq(&die_lock);
+	oops_exit();
+
+	if (in_interrupt())
+		panic("Fatal exception in interrupt");
+	if (panic_on_oops)
+		panic("Fatal exception");
+	if (ret != NOTIFY_STOP)
+		do_exit(SIGSEGV);
+}
+
+void arm64_notify_die(const char *str, struct pt_regs *regs,
+		      struct siginfo *info, int err)
+{
+	if (user_mode(regs))
+		force_sig_info(info->si_signo, info, current);
+	else
+		die(str, regs, err);
+}
+
+asmlinkage void __exception do_undefinstr(struct pt_regs *regs)
+{
+	siginfo_t info;
+	void __user *pc = (void __user *)instruction_pointer(regs);
+
+#ifdef CONFIG_COMPAT
+	/* check for AArch32 breakpoint instructions */
+	if (compat_user_mode(regs) && aarch32_break_trap(regs) == 0)
+		return;
+#endif
+
+	if (show_unhandled_signals) {
+		pr_info("%s[%d]: undefined instruction: pc=%p\n",
+			current->comm, task_pid_nr(current), pc);
+		dump_instr(KERN_INFO, regs);
+	}
+
+	info.si_signo = SIGILL;
+	info.si_errno = 0;
+	info.si_code  = ILL_ILLOPC;
+	info.si_addr  = pc;
+
+	arm64_notify_die("Oops - undefined instruction", regs, &info, 0);
+}
+
+long compat_arm_syscall(struct pt_regs *regs);
+
+asmlinkage long do_ni_syscall(struct pt_regs *regs)
+{
+#ifdef CONFIG_COMPAT
+	long ret;
+	if (is_compat_task()) {
+		ret = compat_arm_syscall(regs);
+		if (ret != -ENOSYS)
+			return ret;
+	}
+#endif
+
+	if (show_unhandled_signals) {
+		pr_info("%s[%d]: syscall %d\n", current->comm,
+			task_pid_nr(current), (int)regs->syscallno);
+		dump_instr("", regs);
+		if (user_mode(regs))
+			__show_regs(regs);
+	}
+
+	return sys_ni_syscall();
+}
+
+/*
+ * bad_mode handles the impossible case in the exception vector.
+ */
+asmlinkage void bad_mode(struct pt_regs *regs, int reason, unsigned int esr)
+{
+	console_verbose();
+
+	pr_crit("Bad mode in %s handler detected, code 0x%08x\n",
+		handler[reason], esr);
+
+	die("Oops - bad mode", regs, 0);
+	local_irq_disable();
+	panic("bad mode");
+}
+
+void __pte_error(const char *file, int line, unsigned long val)
+{
+	printk("%s:%d: bad pte %016lx.\n", file, line, val);
+}
+
+void __pmd_error(const char *file, int line, unsigned long val)
+{
+	printk("%s:%d: bad pmd %016lx.\n", file, line, val);
+}
+
+void __pgd_error(const char *file, int line, unsigned long val)
+{
+	printk("%s:%d: bad pgd %016lx.\n", file, line, val);
+}
+
+void __init trap_init(void)
+{
+	return;
+}