traps.c

linux-2.6.15.6

/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * arch/sh64/kernel/traps.c
 *
 * Copyright (C) 2000, 2001  Paolo Alberelli
 * Copyright (C) 2003, 2004  Paul Mundt
 * Copyright (C) 2003, 2004  Richard Curnow
 *
 */

/*
 * 'Traps.c' handles hardware traps and faults after we have saved some
 * state in 'entry.S'.
 */
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/ptrace.h>
#include <linux/timer.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/spinlock.h>
#include <linux/kallsyms.h>
#include <linux/interrupt.h>
#include <linux/sysctl.h>
#include <linux/module.h>

#include <asm/system.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <asm/atomic.h>
#include <asm/processor.h>
#include <asm/pgtable.h>

#undef DEBUG_EXCEPTION
#ifdef DEBUG_EXCEPTION
/* implemented in ../lib/dbg.c */
extern void show_excp_regs(char *fname, int trapnr, int signr,
			   struct pt_regs *regs);
#else
#define show_excp_regs(a, b, c, d)
#endif

static void do_unhandled_exception(int trapnr, int signr, char *str, char *fn_name,
		unsigned long error_code, struct pt_regs *regs, struct task_struct *tsk);

#define DO_ERROR(trapnr, signr, str, name, tsk) \
asmlinkage void do_##name(unsigned long error_code, struct pt_regs *regs) \
{ \
	do_unhandled_exception(trapnr, signr, str, __stringify(name), error_code, regs, current); \
}

spinlock_t die_lock;

void die(const char * str, struct pt_regs * regs, long err)
{
	console_verbose();
	spin_lock_irq(&die_lock);
	printk("%s: %lx\n", str, (err & 0xffffff));
	show_regs(regs);
	spin_unlock_irq(&die_lock);
	do_exit(SIGSEGV);
}

static inline void die_if_kernel(const char * str, struct pt_regs * regs, long err)
{
	if (!user_mode(regs))
		die(str, regs, err);
}

static void die_if_no_fixup(const char * str, struct pt_regs * regs, long err)
{
	if (!user_mode(regs)) {
		const struct exception_table_entry *fixup;
		fixup = search_exception_tables(regs->pc);
		if (fixup) {
			regs->pc = fixup->fixup;
			return;
		}
		die(str, regs, err);
	}
}

DO_ERROR(13, SIGILL,  "illegal slot instruction", illegal_slot_inst, current)
DO_ERROR(87, SIGSEGV, "address error (exec)", address_error_exec, current)


/* Implement misaligned load/store handling for kernel (and optionally for user
   mode too).  Limitation : only SHmedia mode code is handled - there is no
   handling at all for misaligned accesses occurring in SHcompact code yet. */

static int misaligned_fixup(struct pt_regs *regs);

asmlinkage void do_address_error_load(unsigned long error_code, struct pt_regs *regs)
{
	if (misaligned_fixup(regs) < 0) {
		do_unhandled_exception(7, SIGSEGV, "address error(load)",
				"do_address_error_load",
				error_code, regs, current);
	}
	return;
}

asmlinkage void do_address_error_store(unsigned long error_code, struct pt_regs *regs)
{
	if (misaligned_fixup(regs) < 0) {
		do_unhandled_exception(8, SIGSEGV, "address error(store)",
				"do_address_error_store",
				error_code, regs, current);
	}
	return;
}

#if defined(CONFIG_SH64_ID2815_WORKAROUND)

#define OPCODE_INVALID      0
#define OPCODE_USER_VALID   1
#define OPCODE_PRIV_VALID   2

/* getcon/putcon - requires checking which control register is referenced. */
#define OPCODE_CTRL_REG     3

/* Table of valid opcodes for SHmedia mode.
   Form a 10-bit value by concatenating the major/minor opcodes i.e.
   opcode[31:26,20:16].  The 6 MSBs of this value index into the following
   array.  The 4 LSBs select the bit-pair in the entry (bits 1:0 correspond to
   LSBs==4'b0000 etc). */
static unsigned long shmedia_opcode_table[64] = {
	0x55554044,0x54445055,0x15141514,0x14541414,0x00000000,0x10001000,0x01110055,0x04050015,
	0x00000444,0xc0000000,0x44545515,0x40405555,0x55550015,0x10005555,0x55555505,0x04050000,
	0x00000555,0x00000404,0x00040445,0x15151414,0x00000000,0x00000000,0x00000000,0x00000000,
	0x00000055,0x40404444,0x00000404,0xc0009495,0x00000000,0x00000000,0x00000000,0x00000000,
	0x55555555,0x55555555,0x55555555,0x55555555,0x55555555,0x55555555,0x55555555,0x55555555,
	0x55555555,0x55555555,0x55555555,0x55555555,0x55555555,0x55555555,0x55555555,0x55555555,
	0x80005050,0x04005055,0x55555555,0x55555555,0x55555555,0x55555555,0x55555555,0x55555555,
	0x81055554,0x00000404,0x55555555,0x55555555,0x00000000,0x00000000,0x00000000,0x00000000
};

void do_reserved_inst(unsigned long error_code, struct pt_regs *regs)
{
	/* Workaround SH5-101 cut2 silicon defect #2815 :
	   in some situations, inter-mode branches from SHcompact -> SHmedia
	   which should take ITLBMISS or EXECPROT exceptions at the target
	   falsely take RESINST at the target instead. */

	unsigned long opcode = 0x6ff4fff0; /* guaranteed reserved opcode */
	unsigned long pc, aligned_pc;
	int get_user_error;
	int trapnr = 12;
	int signr = SIGILL;
	char *exception_name = "reserved_instruction";

	pc = regs->pc;
	if ((pc & 3) == 1) {
		/* SHmedia : check for defect.  This requires executable vmas
		   to be readable too. */
		aligned_pc = pc & ~3;
		if (!access_ok(VERIFY_READ, aligned_pc, sizeof(unsigned long))) {
			get_user_error = -EFAULT;
		} else {
			get_user_error = __get_user(opcode, (unsigned long *)aligned_pc);
		}
		if (get_user_error >= 0) {
			unsigned long index, shift;
			unsigned long major, minor, combined;
			unsigned long reserved_field;
			reserved_field = opcode & 0xf; /* These bits are currently reserved as zero in all valid opcodes */
			major = (opcode >> 26) & 0x3f;
			minor = (opcode >> 16) & 0xf;
			combined = (major << 4) | minor;
			index = major;
			shift = minor << 1;
			if (reserved_field == 0) {
				int opcode_state = (shmedia_opcode_table[index] >> shift) & 0x3;
				switch (opcode_state) {
					case OPCODE_INVALID:
						/* Trap. */
						break;
					case OPCODE_USER_VALID:
						/* Restart the instruction : the branch to the instruction will now be from an RTE
						   not from SHcompact so the silicon defect won't be triggered. */
						return;
					case OPCODE_PRIV_VALID:
						if (!user_mode(regs)) {
							/* Should only ever get here if a module has
							   SHcompact code inside it.  If so, the same fix up is needed. */
							return; /* same reason */
						}
						/* Otherwise, user mode trying to execute a privileged instruction -
						   fall through to trap. */
						break;
					case OPCODE_CTRL_REG:
						/* If in privileged mode, return as above. */
						if (!user_mode(regs)) return;
						/* In user mode ... */
						if (combined == 0x9f) { /* GETCON */
							unsigned long regno = (opcode >> 20) & 0x3f;
							if (regno >= 62) {
								return;
							}
							/* Otherwise, reserved or privileged control register, => trap */
						} else if (combined == 0x1bf) { /* PUTCON */
							unsigned long regno = (opcode >> 4) & 0x3f;
							if (regno >= 62) {
								return;
							}
							/* Otherwise, reserved or privileged control register, => trap */
						} else {
							/* Trap */
						}
						break;
					default:
						/* Fall through to trap. */
						break;
				}
			}
			/* fall through to normal resinst processing */
		} else {
			/* Error trying to read opcode.  This typically means a
			   real fault, not a RESINST any more.  So change the
			   codes. */
			trapnr = 87;
			exception_name = "address error (exec)";
			signr = SIGSEGV;
		}
	}

	do_unhandled_exception(trapnr, signr, exception_name, "do_reserved_inst", error_code, regs, current);
}

#else /* CONFIG_SH64_ID2815_WORKAROUND */

/* If the workaround isn't needed, this is just a straightforward reserved
   instruction */
DO_ERROR(12, SIGILL,  "reserved instruction", reserved_inst, current)

#endif /* CONFIG_SH64_ID2815_WORKAROUND */


#include <asm/system.h>

/* Called with interrupts disabled */
asmlinkage void do_exception_error(unsigned long ex, struct pt_regs *regs)
{
	PLS();
	show_excp_regs(__FUNCTION__, -1, -1, regs);
	die_if_kernel("exception", regs, ex);
}

int do_unknown_trapa(unsigned long scId, struct pt_regs *regs)
{
	/* Syscall debug */
        printk("System call ID error: [0x1#args:8 #syscall:16  0x%lx]\n", scId);

	die_if_kernel("unknown trapa", regs, scId);

	return -ENOSYS;
}

void show_stack(struct task_struct *tsk, unsigned long *sp)
{
#ifdef CONFIG_KALLSYMS
	extern void sh64_unwind(struct pt_regs *regs);
	struct pt_regs *regs;

	regs = tsk ? tsk->thread.kregs : NULL;

	sh64_unwind(regs);
#else
	printk(KERN_ERR "Can't backtrace on sh64 without CONFIG_KALLSYMS\n");
#endif
}

void show_task(unsigned long *sp)
{
	show_stack(NULL, sp);
}

void dump_stack(void)
{
	show_task(NULL);
}
/* Needed by any user of WARN_ON in view of the defn in include/asm-sh/bug.h */
EXPORT_SYMBOL(dump_stack);

static void do_unhandled_exception(int trapnr, int signr, char *str, char *fn_name,
		unsigned long error_code, struct pt_regs *regs, struct task_struct *tsk)
{
	show_excp_regs(fn_name, trapnr, signr, regs);
	tsk->thread.error_code = error_code;
	tsk->thread.trap_no = trapnr;

	if (user_mode(regs))
		force_sig(signr, tsk);

	die_if_no_fixup(str, regs, error_code);
}

static int read_opcode(unsigned long long pc, unsigned long *result_opcode, int from_user_mode)
{
	int get_user_error;
	unsigned long aligned_pc;
	unsigned long opcode;

	if ((pc & 3) == 1) {
		/* SHmedia */
		aligned_pc = pc & ~3;
		if (from_user_mode) {
			if (!access_ok(VERIFY_READ, aligned_pc, sizeof(unsigned long))) {
				get_user_error = -EFAULT;
			} else {
				get_user_error = __get_user(opcode, (unsigned long *)aligned_pc);
				*result_opcode = opcode;
			}
			return get_user_error;
		} else {
			/* If the fault was in the kernel, we can either read
			 * this directly, or if not, we fault.
			*/
			*result_opcode = *(unsigned long *) aligned_pc;
			return 0;
		}
	} else if ((pc & 1) == 0) {
		/* SHcompact */
		/* TODO : provide handling for this.  We don't really support
		   user-mode SHcompact yet, and for a kernel fault, this would
		   have to come from a module built for SHcompact.  */
		return -EFAULT;
	} else {
		/* misaligned */
		return -EFAULT;
	}
}

static int address_is_sign_extended(__u64 a)
{
	__u64 b;
#if (NEFF == 32)
	b = (__u64)(__s64)(__s32)(a & 0xffffffffUL);
	return (b == a) ? 1 : 0;
#else
#error "Sign extend check only works for NEFF==32"
#endif
}

static int generate_and_check_address(struct pt_regs *regs,
				      __u32 opcode,
				      int displacement_not_indexed,
				      int width_shift,
				      __u64 *address)
{
	/* return -1 for fault, 0 for OK */

	__u64 base_address, addr;
	int basereg;

	basereg = (opcode >> 20) & 0x3f;
	base_address = regs->regs[basereg];
	if (displacement_not_indexed) {
		__s64 displacement;
		displacement = (opcode >> 10) & 0x3ff;
		displacement = ((displacement << 54) >> 54); /* sign extend */
		addr = (__u64)((__s64)base_address + (displacement << width_shift));
	} else {
		__u64 offset;
		int offsetreg;
		offsetreg = (opcode >> 10) & 0x3f;
		offset = regs->regs[offsetreg];
		addr = base_address + offset;
	}

	/* Check sign extended */
	if (!address_is_sign_extended(addr)) {
		return -1;
	}

#if defined(CONFIG_SH64_USER_MISALIGNED_FIXUP)
	/* Check accessible.  For misaligned access in the kernel, assume the
	   address is always accessible (and if not, just fault when the
	   load/store gets done.) */
	if (user_mode(regs)) {
		if (addr >= TASK_SIZE) {
			return -1;
		}
		/* Do access_ok check later - it depends on whether it's a load or a store. */
	}
#endif

	*address = addr;
	return 0;
}

/* Default value as for sh */
#if defined(CONFIG_SH64_USER_MISALIGNED_FIXUP)
static int user_mode_unaligned_fixup_count = 10;
static int user_mode_unaligned_fixup_enable = 1;
#endif

static int kernel_mode_unaligned_fixup_count = 32;

static void misaligned_kernel_word_load(__u64 address, int do_sign_extend, __u64 *result)
{
	unsigned short x;
	unsigned char *p, *q;
	p = (unsigned char *) (int) address;
	q = (unsigned char *) &x;
	q[0] = p[0];
	q[1] = p[1];

	if (do_sign_extend) {
		*result = (__u64)(__s64) *(short *) &x;
	} else {
		*result = (__u64) x;
	}
}

static void misaligned_kernel_word_store(__u64 address, __u64 value)
{
	unsigned short x;
	unsigned char *p, *q;
	p = (unsigned char *) (int) address;
	q = (unsigned char *) &x;

	x = (__u16) value;
	p[0] = q[0];
	p[1] = q[1];
}

static int misaligned_load(struct pt_regs *regs,
			   __u32 opcode,
			   int displacement_not_indexed,
			   int width_shift,
			   int do_sign_extend)
{
	/* Return -1 for a fault, 0 for OK */
	int error;
	int destreg;
	__u64 address;

	error = generate_and_check_address(regs, opcode,
			displacement_not_indexed, width_shift, &address);
	if (error < 0) {
		return error;
	}

	destreg = (opcode >> 4) & 0x3f;
#if defined(CONFIG_SH64_USER_MISALIGNED_FIXUP)
	if (user_mode(regs)) {
		__u64 buffer;

		if (!access_ok(VERIFY_READ, (unsigned long) address, 1UL<<width_shift)) {
			return -1;
		}

		if (__copy_user(&buffer, (const void *)(int)address, (1 << width_shift)) > 0) {
			return -1; /* fault */
		}
		switch (width_shift) {
		case 1:
			if (do_sign_extend) {
				regs->regs[destreg] = (__u64)(__s64) *(__s16 *) &buffer;
			} else {
				regs->regs[destreg] = (__u64) *(__u16 *) &buffer;
			}
			break;
		case 2:
			regs->regs[destreg] = (__u64)(__s64) *(__s32 *) &buffer;
			break;
		case 3:
			regs->regs[destreg] = buffer;
			break;
		default:
			printk("Unexpected width_shift %d in misaligned_load, PC=%08lx\n",
				width_shift, (unsigned long) regs->pc);