kernel/unwind.c - android_kernel_oneplus_msm8996 - Gitiles

 /*
  * Copyright (C) 2002-2006 Novell, Inc.
  *	Jan Beulich <jbeulich@novell.com>
  * This code is released under version 2 of the GNU GPL.
  *
  * A simple API for unwinding kernel stacks.  This is used for
  * debugging and error reporting purposes.  The kernel doesn't need
  * full-blown stack unwinding with all the bells and whistles, so there
  * is not much point in implementing the full Dwarf2 unwind API.
  */

 #include <linux/unwind.h>
 #include <linux/module.h>
 #include <linux/delay.h>
 #include <linux/stop_machine.h>
 #include <asm/sections.h>
 #include <asm/uaccess.h>
 #include <asm/unaligned.h>

 extern char __start_unwind[], __end_unwind[];

 #define MAX_STACK_DEPTH 8

 #define EXTRA_INFO(f) { \
 		BUILD_BUG_ON_ZERO(offsetof(struct unwind_frame_info, f) \
 		                  % FIELD_SIZEOF(struct unwind_frame_info, f)) \
 		+ offsetof(struct unwind_frame_info, f) \
 		  / FIELD_SIZEOF(struct unwind_frame_info, f), \
 		FIELD_SIZEOF(struct unwind_frame_info, f) \
 	}
 #define PTREGS_INFO(f) EXTRA_INFO(regs.f)

 static const struct {
 	unsigned offs:BITS_PER_LONG / 2;
 	unsigned width:BITS_PER_LONG / 2;
 } reg_info[] = {
 	UNW_REGISTER_INFO
 };

 #undef PTREGS_INFO
 #undef EXTRA_INFO

 #ifndef REG_INVALID
 #define REG_INVALID(r) (reg_info[r].width == 0)
 #endif

 #define DW_CFA_nop                          0x00
 #define DW_CFA_set_loc                      0x01
 #define DW_CFA_advance_loc1                 0x02
 #define DW_CFA_advance_loc2                 0x03
 #define DW_CFA_advance_loc4                 0x04
 #define DW_CFA_offset_extended              0x05
 #define DW_CFA_restore_extended             0x06
 #define DW_CFA_undefined                    0x07
 #define DW_CFA_same_value                   0x08
 #define DW_CFA_register                     0x09
 #define DW_CFA_remember_state               0x0a
 #define DW_CFA_restore_state                0x0b
 #define DW_CFA_def_cfa                      0x0c
 #define DW_CFA_def_cfa_register             0x0d
 #define DW_CFA_def_cfa_offset               0x0e
 #define DW_CFA_def_cfa_expression           0x0f
 #define DW_CFA_expression                   0x10
 #define DW_CFA_offset_extended_sf           0x11
 #define DW_CFA_def_cfa_sf                   0x12
 #define DW_CFA_def_cfa_offset_sf            0x13
 #define DW_CFA_val_offset                   0x14
 #define DW_CFA_val_offset_sf                0x15
 #define DW_CFA_val_expression               0x16
 #define DW_CFA_lo_user                      0x1c
 #define DW_CFA_GNU_window_save              0x2d
 #define DW_CFA_GNU_args_size                0x2e
 #define DW_CFA_GNU_negative_offset_extended 0x2f
 #define DW_CFA_hi_user                      0x3f

 #define DW_EH_PE_FORM     0x07
 #define DW_EH_PE_native   0x00
 #define DW_EH_PE_leb128   0x01
 #define DW_EH_PE_data2    0x02
 #define DW_EH_PE_data4    0x03
 #define DW_EH_PE_data8    0x04
 #define DW_EH_PE_signed   0x08
 #define DW_EH_PE_ADJUST   0x70
 #define DW_EH_PE_abs      0x00
 #define DW_EH_PE_pcrel    0x10
 #define DW_EH_PE_textrel  0x20
 #define DW_EH_PE_datarel  0x30
 #define DW_EH_PE_funcrel  0x40
 #define DW_EH_PE_aligned  0x50
 #define DW_EH_PE_indirect 0x80
 #define DW_EH_PE_omit     0xff

 typedef unsigned long uleb128_t;
 typedef   signed long sleb128_t;

 static struct unwind_table {
 	struct {
 		unsigned long pc;
 		unsigned long range;
 	} core, init;
 	const void *address;
 	unsigned long size;
 	struct unwind_table *link;
 	const char *name;
 } root_table, *last_table;

 struct unwind_item {
 	enum item_location {
 		Nowhere,
 		Memory,
 		Register,
 		Value
 	} where;
 	uleb128_t value;
 };

 struct unwind_state {
 	uleb128_t loc, org;
 	const u8 *cieStart, *cieEnd;
 	uleb128_t codeAlign;
 	sleb128_t dataAlign;
 	struct cfa {
 		uleb128_t reg, offs;
 	} cfa;
 	struct unwind_item regs[ARRAY_SIZE(reg_info)];
 	unsigned stackDepth:8;
 	unsigned version:8;
 	const u8 *label;
 	const u8 *stack[MAX_STACK_DEPTH];
 };

 static const struct cfa badCFA = { ARRAY_SIZE(reg_info), 1 };

 static struct unwind_table *find_table(unsigned long pc)
 {
 	struct unwind_table *table;

 	for (table = &root_table; table; table = table->link)
 		if ((pc >= table->core.pc
 		     && pc < table->core.pc + table->core.range)
 		    || (pc >= table->init.pc
 		        && pc < table->init.pc + table->init.range))
 			break;

 	return table;
 }

 static void init_unwind_table(struct unwind_table *table,
                               const char *name,
                               const void *core_start,
                               unsigned long core_size,
                               const void *init_start,
                               unsigned long init_size,
                               const void *table_start,
                               unsigned long table_size)
 {
 	table->core.pc = (unsigned long)core_start;
 	table->core.range = core_size;
 	table->init.pc = (unsigned long)init_start;
 	table->init.range = init_size;
 	table->address = table_start;
 	table->size = table_size;
 	table->link = NULL;
 	table->name = name;
 }

 void __init unwind_init(void)
 {
 	init_unwind_table(&root_table, "kernel",
 	                  _text, _end - _text,
 	                  NULL, 0,
 	                  __start_unwind, __end_unwind - __start_unwind);
 }

 #ifdef CONFIG_MODULES

 /* Must be called with module_mutex held. */
 void *unwind_add_table(struct module *module,
                        const void *table_start,
                        unsigned long table_size)
 {
 	struct unwind_table *table;

 	if (table_size <= 0)
 		return NULL;

 	table = kmalloc(sizeof(*table), GFP_KERNEL);
 	if (!table)
 		return NULL;

 	init_unwind_table(table, module->name,
 	                  module->module_core, module->core_size,
 	                  module->module_init, module->init_size,
 	                  table_start, table_size);

 	if (last_table)
 		last_table->link = table;
 	else
 		root_table.link = table;
 	last_table = table;

 	return table;
 }

 struct unlink_table_info
 {
 	struct unwind_table *table;
 	int init_only;
 };

 static int unlink_table(void *arg)
 {
 	struct unlink_table_info *info = arg;
 	struct unwind_table *table = info->table, *prev;

 	for (prev = &root_table; prev->link && prev->link != table; prev = prev->link)
 		;

 	if (prev->link) {
 		if (info->init_only) {
 			table->init.pc = 0;
 			table->init.range = 0;
 			info->table = NULL;
 		} else {
 			prev->link = table->link;
 			if (!prev->link)
 				last_table = prev;
 		}
 	} else
 		info->table = NULL;

 	return 0;
 }

 /* Must be called with module_mutex held. */
 void unwind_remove_table(void *handle, int init_only)
 {
 	struct unwind_table *table = handle;
 	struct unlink_table_info info;

 	if (!table || table == &root_table)
 		return;

 	if (init_only && table == last_table) {
 		table->init.pc = 0;
 		table->init.range = 0;
 		return;
 	}

 	info.table = table;
 	info.init_only = init_only;
 	stop_machine_run(unlink_table, &info, NR_CPUS);

 	if (info.table)
 		kfree(table);
 }

 #endif /* CONFIG_MODULES */

 static uleb128_t get_uleb128(const u8 **pcur, const u8 *end)
 {
 	const u8 *cur = *pcur;
 	uleb128_t value;
 	unsigned shift;

 	for (shift = 0, value = 0; cur < end; shift += 7) {
 		if (shift + 7 > 8 * sizeof(value)
 		    && (*cur & 0x7fU) >= (1U << (8 * sizeof(value) - shift))) {
 			cur = end + 1;
 			break;
 		}
 		value |= (uleb128_t)(*cur & 0x7f) << shift;
 		if (!(*cur++ & 0x80))
 			break;
 	}
 	*pcur = cur;

 	return value;
 }

 static sleb128_t get_sleb128(const u8 **pcur, const u8 *end)
 {
 	const u8 *cur = *pcur;
 	sleb128_t value;
 	unsigned shift;

 	for (shift = 0, value = 0; cur < end; shift += 7) {
 		if (shift + 7 > 8 * sizeof(value)
 		    && (*cur & 0x7fU) >= (1U << (8 * sizeof(value) - shift))) {
 			cur = end + 1;
 			break;
 		}
 		value |= (sleb128_t)(*cur & 0x7f) << shift;
 		if (!(*cur & 0x80)) {
 			value |= -(*cur++ & 0x40) << shift;
 			break;
 		}
 	}
 	*pcur = cur;

 	return value;
 }

 static unsigned long read_pointer(const u8 **pLoc,
                                   const void *end,
                                   signed ptrType)
 {
 	unsigned long value = 0;
 	union {
 		const u8 *p8;
 		const u16 *p16u;
 		const s16 *p16s;
 		const u32 *p32u;
 		const s32 *p32s;
 		const unsigned long *pul;
 	} ptr;

 	if (ptrType < 0 || ptrType == DW_EH_PE_omit)
 		return 0;
 	ptr.p8 = *pLoc;
 	switch(ptrType & DW_EH_PE_FORM) {
 	case DW_EH_PE_data2:
 		if (end < (const void *)(ptr.p16u + 1))
 			return 0;
 		if(ptrType & DW_EH_PE_signed)
 			value = get_unaligned(ptr.p16s++);
 		else
 			value = get_unaligned(ptr.p16u++);
 		break;
 	case DW_EH_PE_data4:
 #ifdef CONFIG_64BIT
 		if (end < (const void *)(ptr.p32u + 1))
 			return 0;
 		if(ptrType & DW_EH_PE_signed)
 			value = get_unaligned(ptr.p32s++);
 		else
 			value = get_unaligned(ptr.p32u++);
 		break;
 	case DW_EH_PE_data8:
 		BUILD_BUG_ON(sizeof(u64) != sizeof(value));
 #else
 		BUILD_BUG_ON(sizeof(u32) != sizeof(value));
 #endif
 	case DW_EH_PE_native:
 		if (end < (const void *)(ptr.pul + 1))
 			return 0;
 		value = get_unaligned(ptr.pul++);
 		break;
 	case DW_EH_PE_leb128:
 		BUILD_BUG_ON(sizeof(uleb128_t) > sizeof(value));
 		value = ptrType & DW_EH_PE_signed
 		        ? get_sleb128(&ptr.p8, end)
 		        : get_uleb128(&ptr.p8, end);
 		if ((const void *)ptr.p8 > end)
 			return 0;
 		break;
 	default:
 		return 0;
 	}
 	switch(ptrType & DW_EH_PE_ADJUST) {
 	case DW_EH_PE_abs:
 		break;
 	case DW_EH_PE_pcrel:
 		value += (unsigned long)*pLoc;
 		break;
 	default:
 		return 0;
 	}
 	if ((ptrType & DW_EH_PE_indirect)
 	    && __get_user(value, (unsigned long *)value))
 		return 0;
 	*pLoc = ptr.p8;

 	return value;
 }

 static signed fde_pointer_type(const u32 *cie)
 {
 	const u8 *ptr = (const u8 *)(cie + 2);
 	unsigned version = *ptr;

 	if (version != 1)
 		return -1; /* unsupported */
 	if (*++ptr) {
 		const char *aug;
 		const u8 *end = (const u8 *)(cie + 1) + *cie;
 		uleb128_t len;

 		/* check if augmentation size is first (and thus present) */
 		if (*ptr != 'z')
 			return -1;
 		/* check if augmentation string is nul-terminated */
 		if ((ptr = memchr(aug = (const void *)ptr, 0, end - ptr)) == NULL)
 			return -1;
 		++ptr; /* skip terminator */
 		get_uleb128(&ptr, end); /* skip code alignment */
 		get_sleb128(&ptr, end); /* skip data alignment */
 		/* skip return address column */
 		version <= 1 ? (void)++ptr : (void)get_uleb128(&ptr, end);
 		len = get_uleb128(&ptr, end); /* augmentation length */
 		if (ptr + len < ptr || ptr + len > end)
 			return -1;
 		end = ptr + len;
 		while (*++aug) {
 			if (ptr >= end)
 				return -1;
 			switch(*aug) {
 			case 'L':
 				++ptr;
 				break;
 			case 'P': {
 					signed ptrType = *ptr++;

 					if (!read_pointer(&ptr, end, ptrType) || ptr > end)
 						return -1;
 				}
 				break;
 			case 'R':
 				return *ptr;
 			default:
 				return -1;
 			}
 		}
 	}
 	return DW_EH_PE_native|DW_EH_PE_abs;
 }

 static int advance_loc(unsigned long delta, struct unwind_state *state)
 {
 	state->loc += delta * state->codeAlign;

 	return delta > 0;
 }

 static void set_rule(uleb128_t reg,
                      enum item_location where,
                      uleb128_t value,
                      struct unwind_state *state)
 {
 	if (reg < ARRAY_SIZE(state->regs)) {
 		state->regs[reg].where = where;
 		state->regs[reg].value = value;
 	}
 }

 static int processCFI(const u8 *start,
                       const u8 *end,
                       unsigned long targetLoc,
                       signed ptrType,
                       struct unwind_state *state)
 {
 	union {
 		const u8 *p8;
 		const u16 *p16;
 		const u32 *p32;
 	} ptr;
 	int result = 1;

 	if (start != state->cieStart) {
 		state->loc = state->org;
 		result = processCFI(state->cieStart, state->cieEnd, 0, ptrType, state);
 		if (targetLoc == 0 && state->label == NULL)
 			return result;
 	}
 	for (ptr.p8 = start; result && ptr.p8 < end; ) {
 		switch(*ptr.p8 >> 6) {
 			uleb128_t value;

 		case 0:
 			switch(*ptr.p8++) {
 			case DW_CFA_nop:
 				break;
 			case DW_CFA_set_loc:
 				if ((state->loc = read_pointer(&ptr.p8, end, ptrType)) == 0)
 					result = 0;
 				break;
 			case DW_CFA_advance_loc1:
 				result = ptr.p8 < end && advance_loc(*ptr.p8++, state);
 				break;
 			case DW_CFA_advance_loc2:
 				result = ptr.p8 <= end + 2
 				         && advance_loc(*ptr.p16++, state);
 				break;
 			case DW_CFA_advance_loc4:
 				result = ptr.p8 <= end + 4
 				         && advance_loc(*ptr.p32++, state);
 				break;
 			case DW_CFA_offset_extended:
 				value = get_uleb128(&ptr.p8, end);
 				set_rule(value, Memory, get_uleb128(&ptr.p8, end), state);
 				break;
 			case DW_CFA_val_offset:
 				value = get_uleb128(&ptr.p8, end);
 				set_rule(value, Value, get_uleb128(&ptr.p8, end), state);
 				break;
 			case DW_CFA_offset_extended_sf:
 				value = get_uleb128(&ptr.p8, end);
 				set_rule(value, Memory, get_sleb128(&ptr.p8, end), state);
 				break;
 			case DW_CFA_val_offset_sf:
 				value = get_uleb128(&ptr.p8, end);
 				set_rule(value, Value, get_sleb128(&ptr.p8, end), state);
 				break;
 			case DW_CFA_restore_extended:
 			case DW_CFA_undefined:
 			case DW_CFA_same_value:
 				set_rule(get_uleb128(&ptr.p8, end), Nowhere, 0, state);
 				break;
 			case DW_CFA_register:
 				value = get_uleb128(&ptr.p8, end);
 				set_rule(value,
 				         Register,
 				         get_uleb128(&ptr.p8, end), state);
 				break;
 			case DW_CFA_remember_state:
 				if (ptr.p8 == state->label) {
 					state->label = NULL;
 					return 1;
 				}
 				if (state->stackDepth >= MAX_STACK_DEPTH)
 					return 0;
 				state->stack[state->stackDepth++] = ptr.p8;
 				break;
 			case DW_CFA_restore_state:
 				if (state->stackDepth) {
 					const uleb128_t loc = state->loc;
 					const u8 *label = state->label;

 					state->label = state->stack[state->stackDepth - 1];
 					memcpy(&state->cfa, &badCFA, sizeof(state->cfa));
 					memset(state->regs, 0, sizeof(state->regs));
 					state->stackDepth = 0;
 					result = processCFI(start, end, 0, ptrType, state);
 					state->loc = loc;
 					state->label = label;
 				} else
 					return 0;
 				break;
 			case DW_CFA_def_cfa:
 				state->cfa.reg = get_uleb128(&ptr.p8, end);
 				/*nobreak*/
 			case DW_CFA_def_cfa_offset:
 				state->cfa.offs = get_uleb128(&ptr.p8, end);
 				break;
 			case DW_CFA_def_cfa_sf:
 				state->cfa.reg = get_uleb128(&ptr.p8, end);
 				/*nobreak*/
 			case DW_CFA_def_cfa_offset_sf:
 				state->cfa.offs = get_sleb128(&ptr.p8, end)
 				                  * state->dataAlign;
 				break;
 			case DW_CFA_def_cfa_register:
 				state->cfa.reg = get_uleb128(&ptr.p8, end);
 				break;
 			/*todo case DW_CFA_def_cfa_expression: */
 			/*todo case DW_CFA_expression: */
 			/*todo case DW_CFA_val_expression: */
 			case DW_CFA_GNU_args_size:
 				get_uleb128(&ptr.p8, end);
 				break;
 			case DW_CFA_GNU_negative_offset_extended:
 				value = get_uleb128(&ptr.p8, end);
 				set_rule(value,
 				         Memory,
 				         (uleb128_t)0 - get_uleb128(&ptr.p8, end), state);
 				break;
 			case DW_CFA_GNU_window_save:
 			default:
 				result = 0;
 				break;
 			}
 			break;
 		case 1:
 			result = advance_loc(*ptr.p8++ & 0x3f, state);
 			break;
 		case 2:
 			value = *ptr.p8++ & 0x3f;
 			set_rule(value, Memory, get_uleb128(&ptr.p8, end), state);
 			break;
 		case 3:
 			set_rule(*ptr.p8++ & 0x3f, Nowhere, 0, state);
 			break;
 		}
 		if (ptr.p8 > end)
 			result = 0;
 		if (result && targetLoc != 0 && targetLoc < state->loc)
 			return 1;
 	}

 	return result
 	   && ptr.p8 == end
 	   && (targetLoc == 0
 	    || (/*todo While in theory this should apply, gcc in practice omits
 	          everything past the function prolog, and hence the location
 	          never reaches the end of the function.
 	        targetLoc < state->loc &&*/ state->label == NULL));
 }

 /* Unwind to previous to frame.  Returns 0 if successful, negative
  * number in case of an error. */
 int unwind(struct unwind_frame_info *frame)
 {
 #define FRAME_REG(r, t) (((t *)frame)[reg_info[r].offs])
 	const u32 *fde = NULL, *cie = NULL;
 	const u8 *ptr = NULL, *end = NULL;
 	unsigned long startLoc = 0, endLoc = 0, cfa;
 	unsigned i;
 	signed ptrType = -1;
 	uleb128_t retAddrReg = 0;
 	struct unwind_table *table;
 	struct unwind_state state;

 	if (UNW_PC(frame) == 0)
 		return -EINVAL;
 	if ((table = find_table(UNW_PC(frame))) != NULL
 	    && !(table->size & (sizeof(*fde) - 1))) {
 		unsigned long tableSize = table->size;

 		for (fde = table->address;
 		     tableSize > sizeof(*fde) && tableSize - sizeof(*fde) >= *fde;
 		     tableSize -= sizeof(*fde) + *fde,
 		     fde += 1 + *fde / sizeof(*fde)) {
 			if (!*fde || (*fde & (sizeof(*fde) - 1)))
 				break;
 			if (!fde[1])
 				continue; /* this is a CIE */
 			if ((fde[1] & (sizeof(*fde) - 1))
 			    || fde[1] > (unsigned long)(fde + 1)
 			                - (unsigned long)table->address)
 				continue; /* this is not a valid FDE */
 			cie = fde + 1 - fde[1] / sizeof(*fde);
 			if (*cie <= sizeof(*cie) + 4
 			    || *cie >= fde[1] - sizeof(*fde)
 			    || (*cie & (sizeof(*cie) - 1))
 			    || cie[1]
 			    || (ptrType = fde_pointer_type(cie)) < 0) {
 				cie = NULL; /* this is not a (valid) CIE */
 				continue;
 			}
 			ptr = (const u8 *)(fde + 2);
 			startLoc = read_pointer(&ptr,
 			                        (const u8 *)(fde + 1) + *fde,
 			                        ptrType);
 			endLoc = startLoc
 			         + read_pointer(&ptr,
 			                        (const u8 *)(fde + 1) + *fde,
 			                        ptrType & DW_EH_PE_indirect
 			                        ? ptrType
 			                        : ptrType & (DW_EH_PE_FORM|DW_EH_PE_signed));
 			if (UNW_PC(frame) >= startLoc && UNW_PC(frame) < endLoc)
 				break;
 			cie = NULL;
 		}
 	}
 	if (cie != NULL) {
 		memset(&state, 0, sizeof(state));
 		state.cieEnd = ptr; /* keep here temporarily */
 		ptr = (const u8 *)(cie + 2);
 		end = (const u8 *)(cie + 1) + *cie;
 		if ((state.version = *ptr) != 1)
 			cie = NULL; /* unsupported version */
 		else if (*++ptr) {
 			/* check if augmentation size is first (and thus present) */
 			if (*ptr == 'z') {
 				/* check for ignorable (or already handled)
 				 * nul-terminated augmentation string */
 				while (++ptr < end && *ptr)
 					if (strchr("LPR", *ptr) == NULL)
 						break;
 			}
 			if (ptr >= end || *ptr)
 				cie = NULL;
 		}
 		++ptr;
 	}
 	if (cie != NULL) {
 		/* get code aligment factor */
 		state.codeAlign = get_uleb128(&ptr, end);
 		/* get data aligment factor */
 		state.dataAlign = get_sleb128(&ptr, end);
 		if (state.codeAlign == 0 || state.dataAlign == 0 || ptr >= end)
 			cie = NULL;
 		else {
 			retAddrReg = state.version <= 1 ? *ptr++ : get_uleb128(&ptr, end);
 			/* skip augmentation */
 			if (((const char *)(cie + 2))[1] == 'z')
 				ptr += get_uleb128(&ptr, end);
 			if (ptr > end
 			   || retAddrReg >= ARRAY_SIZE(reg_info)
 			   || REG_INVALID(retAddrReg)
 			   || reg_info[retAddrReg].width != sizeof(unsigned long))
 				cie = NULL;
 		}
 	}
 	if (cie != NULL) {
 		state.cieStart = ptr;
 		ptr = state.cieEnd;
 		state.cieEnd = end;
 		end = (const u8 *)(fde + 1) + *fde;
 		/* skip augmentation */
 		if (((const char *)(cie + 2))[1] == 'z') {
 			uleb128_t augSize = get_uleb128(&ptr, end);

 			if ((ptr += augSize) > end)
 				fde = NULL;
 		}
 	}
 	if (cie == NULL || fde == NULL) {
 #ifdef CONFIG_FRAME_POINTER
 		unsigned long top, bottom;
 #endif

 #ifdef CONFIG_FRAME_POINTER
 		top = STACK_TOP(frame->task);
 		bottom = STACK_BOTTOM(frame->task);
 # if FRAME_RETADDR_OFFSET < 0
 		if (UNW_SP(frame) < top
 		    && UNW_FP(frame) <= UNW_SP(frame)
 		    && bottom < UNW_FP(frame)
 # else
 		if (UNW_SP(frame) > top
 		    && UNW_FP(frame) >= UNW_SP(frame)
 		    && bottom > UNW_FP(frame)
 # endif
 		   && !((UNW_SP(frame) | UNW_FP(frame))
 		        & (sizeof(unsigned long) - 1))) {
 			unsigned long link;

 			if (!__get_user(link,
 			                (unsigned long *)(UNW_FP(frame)
 			                                  + FRAME_LINK_OFFSET))
 # if FRAME_RETADDR_OFFSET < 0
 			   && link > bottom && link < UNW_FP(frame)
 # else
 			   && link > UNW_FP(frame) && link < bottom
 # endif
 			   && !(link & (sizeof(link) - 1))
 			   && !__get_user(UNW_PC(frame),
 			                  (unsigned long *)(UNW_FP(frame)
 			                                    + FRAME_RETADDR_OFFSET))) {
 				UNW_SP(frame) = UNW_FP(frame) + FRAME_RETADDR_OFFSET
 # if FRAME_RETADDR_OFFSET < 0
 					-
 # else
 					+
 # endif
 					  sizeof(UNW_PC(frame));
 				UNW_FP(frame) = link;
 				return 0;
 			}
 		}
 #endif
 		return -ENXIO;
 	}
 	state.org = startLoc;
 	memcpy(&state.cfa, &badCFA, sizeof(state.cfa));
 	/* process instructions */
 	if (!processCFI(ptr, end, UNW_PC(frame), ptrType, &state)
 	   || state.loc > endLoc
 	   || state.regs[retAddrReg].where == Nowhere
 	   || state.cfa.reg >= ARRAY_SIZE(reg_info)
 	   || reg_info[state.cfa.reg].width != sizeof(unsigned long)
 	   || state.cfa.offs % sizeof(unsigned long))
 		return -EIO;
 	/* update frame */
 	cfa = FRAME_REG(state.cfa.reg, unsigned long) + state.cfa.offs;
 	startLoc = min((unsigned long)UNW_SP(frame), cfa);
 	endLoc = max((unsigned long)UNW_SP(frame), cfa);
 	if (STACK_LIMIT(startLoc) != STACK_LIMIT(endLoc)) {
 		startLoc = min(STACK_LIMIT(cfa), cfa);
 		endLoc = max(STACK_LIMIT(cfa), cfa);
 	}
 #ifndef CONFIG_64BIT
 # define CASES CASE(8); CASE(16); CASE(32)
 #else
 # define CASES CASE(8); CASE(16); CASE(32); CASE(64)
 #endif
 	for (i = 0; i < ARRAY_SIZE(state.regs); ++i) {
 		if (REG_INVALID(i)) {
 			if (state.regs[i].where == Nowhere)
 				continue;
 			return -EIO;
 		}
 		switch(state.regs[i].where) {
 		default:
 			break;
 		case Register:
 			if (state.regs[i].value >= ARRAY_SIZE(reg_info)
 			   || REG_INVALID(state.regs[i].value)
 			   || reg_info[i].width > reg_info[state.regs[i].value].width)
 				return -EIO;
 			switch(reg_info[state.regs[i].value].width) {
 #define CASE(n) \
 			case sizeof(u##n): \
 				state.regs[i].value = FRAME_REG(state.regs[i].value, \
 				                                const u##n); \
 				break
 			CASES;
 #undef CASE
 			default:
 				return -EIO;
 			}
 			break;
 		}
 	}
 	for (i = 0; i < ARRAY_SIZE(state.regs); ++i) {
 		if (REG_INVALID(i))
 			continue;
 		switch(state.regs[i].where) {
 		case Nowhere:
 			if (reg_info[i].width != sizeof(UNW_SP(frame))
 			   || &FRAME_REG(i, __typeof__(UNW_SP(frame)))
 			      != &UNW_SP(frame))
 				continue;
 			UNW_SP(frame) = cfa;
 			break;
 		case Register:
 			switch(reg_info[i].width) {
 #define CASE(n) case sizeof(u##n): \
 				FRAME_REG(i, u##n) = state.regs[i].value; \
 				break
 			CASES;
 #undef CASE
 			default:
 				return -EIO;
 			}
 			break;
 		case Value:
 			if (reg_info[i].width != sizeof(unsigned long))
 				return -EIO;
 			FRAME_REG(i, unsigned long) = cfa + state.regs[i].value
 			                                    * state.dataAlign;
 			break;
 		case Memory: {
 				unsigned long addr = cfa + state.regs[i].value
 				                           * state.dataAlign;

 				if ((state.regs[i].value * state.dataAlign)
 				    % sizeof(unsigned long)
 				    || addr < startLoc
 				    || addr + sizeof(unsigned long) < addr
 				    || addr + sizeof(unsigned long) > endLoc)
 					return -EIO;
 				switch(reg_info[i].width) {
 #define CASE(n)     case sizeof(u##n): \
 					__get_user(FRAME_REG(i, u##n), (u##n *)addr); \
 					break
 				CASES;
 #undef CASE
 				default:
 					return -EIO;
 				}
 			}
 			break;
 		}
 	}

 	return 0;
 #undef CASES
 #undef FRAME_REG
 }
 EXPORT_SYMBOL(unwind);

 int unwind_init_frame_info(struct unwind_frame_info *info,
                            struct task_struct *tsk,
                            /*const*/ struct pt_regs *regs)
 {
 	info->task = tsk;
 	arch_unw_init_frame_info(info, regs);

 	return 0;
 }
 EXPORT_SYMBOL(unwind_init_frame_info);

 /*
  * Prepare to unwind a blocked task.
  */
 int unwind_init_blocked(struct unwind_frame_info *info,
                         struct task_struct *tsk)
 {
 	info->task = tsk;
 	arch_unw_init_blocked(info);

 	return 0;
 }
 EXPORT_SYMBOL(unwind_init_blocked);

 /*
  * Prepare to unwind the currently running thread.
  */
 int unwind_init_running(struct unwind_frame_info *info,
                         asmlinkage int (*callback)(struct unwind_frame_info *,
                                                    void *arg),
                         void *arg)
 {
 	info->task = current;

 	return arch_unwind_init_running(info, callback, arg);
 }
 EXPORT_SYMBOL(unwind_init_running);

 /*
  * Unwind until the return pointer is in user-land (or until an error
  * occurs).  Returns 0 if successful, negative number in case of
  * error.
  */
 int unwind_to_user(struct unwind_frame_info *info)
 {
 	while (!arch_unw_user_mode(info)) {
 		int err = unwind(info);

 		if (err < 0)
 			return err;
 	}

 	return 0;
 }
 EXPORT_SYMBOL(unwind_to_user);
	/*
	* Copyright (C) 2002-2006 Novell, Inc.
	* Jan Beulich <jbeulich@novell.com>
	* This code is released under version 2 of the GNU GPL.
	*
	* A simple API for unwinding kernel stacks. This is used for
	* debugging and error reporting purposes. The kernel doesn't need
	* full-blown stack unwinding with all the bells and whistles, so there
	* is not much point in implementing the full Dwarf2 unwind API.
	*/

	#include <linux/unwind.h>
	#include <linux/module.h>
	#include <linux/delay.h>
	#include <linux/stop_machine.h>
	#include <asm/sections.h>
	#include <asm/uaccess.h>
	#include <asm/unaligned.h>

	extern char __start_unwind[], __end_unwind[];

	#define MAX_STACK_DEPTH 8

	#define EXTRA_INFO(f) { \
	BUILD_BUG_ON_ZERO(offsetof(struct unwind_frame_info, f) \
	% FIELD_SIZEOF(struct unwind_frame_info, f)) \
	+ offsetof(struct unwind_frame_info, f) \
	/ FIELD_SIZEOF(struct unwind_frame_info, f), \
	FIELD_SIZEOF(struct unwind_frame_info, f) \
	}
	#define PTREGS_INFO(f) EXTRA_INFO(regs.f)

	static const struct {
	unsigned offs:BITS_PER_LONG / 2;
	unsigned width:BITS_PER_LONG / 2;
	} reg_info[] = {
	UNW_REGISTER_INFO
	};

	#undef PTREGS_INFO
	#undef EXTRA_INFO

	#ifndef REG_INVALID
	#define REG_INVALID(r) (reg_info[r].width == 0)
	#endif

	#define DW_CFA_nop 0x00
	#define DW_CFA_set_loc 0x01
	#define DW_CFA_advance_loc1 0x02
	#define DW_CFA_advance_loc2 0x03
	#define DW_CFA_advance_loc4 0x04
	#define DW_CFA_offset_extended 0x05
	#define DW_CFA_restore_extended 0x06
	#define DW_CFA_undefined 0x07
	#define DW_CFA_same_value 0x08
	#define DW_CFA_register 0x09
	#define DW_CFA_remember_state 0x0a
	#define DW_CFA_restore_state 0x0b
	#define DW_CFA_def_cfa 0x0c
	#define DW_CFA_def_cfa_register 0x0d
	#define DW_CFA_def_cfa_offset 0x0e
	#define DW_CFA_def_cfa_expression 0x0f
	#define DW_CFA_expression 0x10
	#define DW_CFA_offset_extended_sf 0x11
	#define DW_CFA_def_cfa_sf 0x12
	#define DW_CFA_def_cfa_offset_sf 0x13
	#define DW_CFA_val_offset 0x14
	#define DW_CFA_val_offset_sf 0x15
	#define DW_CFA_val_expression 0x16
	#define DW_CFA_lo_user 0x1c
	#define DW_CFA_GNU_window_save 0x2d
	#define DW_CFA_GNU_args_size 0x2e
	#define DW_CFA_GNU_negative_offset_extended 0x2f
	#define DW_CFA_hi_user 0x3f

	#define DW_EH_PE_FORM 0x07
	#define DW_EH_PE_native 0x00
	#define DW_EH_PE_leb128 0x01
	#define DW_EH_PE_data2 0x02
	#define DW_EH_PE_data4 0x03
	#define DW_EH_PE_data8 0x04
	#define DW_EH_PE_signed 0x08
	#define DW_EH_PE_ADJUST 0x70
	#define DW_EH_PE_abs 0x00
	#define DW_EH_PE_pcrel 0x10
	#define DW_EH_PE_textrel 0x20
	#define DW_EH_PE_datarel 0x30
	#define DW_EH_PE_funcrel 0x40
	#define DW_EH_PE_aligned 0x50
	#define DW_EH_PE_indirect 0x80
	#define DW_EH_PE_omit 0xff

	typedef unsigned long uleb128_t;
	typedef signed long sleb128_t;

	static struct unwind_table {
	struct {
	unsigned long pc;
	unsigned long range;
	} core, init;
	const void *address;
	unsigned long size;
	struct unwind_table *link;
	const char *name;
	} root_table, *last_table;

	struct unwind_item {
	enum item_location {
	Nowhere,
	Memory,
	Register,
	Value
	} where;
	uleb128_t value;
	};

	struct unwind_state {
	uleb128_t loc, org;
	const u8 cieStart, cieEnd;
	uleb128_t codeAlign;
	sleb128_t dataAlign;
	struct cfa {
	uleb128_t reg, offs;
	} cfa;
	struct unwind_item regs[ARRAY_SIZE(reg_info)];
	unsigned stackDepth:8;
	unsigned version:8;
	const u8 *label;
	const u8 *stack[MAX_STACK_DEPTH];
	};

	static const struct cfa badCFA = { ARRAY_SIZE(reg_info), 1 };

	static struct unwind_table *find_table(unsigned long pc)
	{
	struct unwind_table *table;

	for (table = &root_table; table; table = table->link)
	if ((pc >= table->core.pc
	&& pc < table->core.pc + table->core.range)
	\|\| (pc >= table->init.pc
	&& pc < table->init.pc + table->init.range))
	break;

	return table;
	}

	static void init_unwind_table(struct unwind_table *table,
	const char *name,
	const void *core_start,
	unsigned long core_size,
	const void *init_start,
	unsigned long init_size,
	const void *table_start,
	unsigned long table_size)
	{
	table->core.pc = (unsigned long)core_start;
	table->core.range = core_size;
	table->init.pc = (unsigned long)init_start;
	table->init.range = init_size;
	table->address = table_start;
	table->size = table_size;
	table->link = NULL;
	table->name = name;
	}

	void __init unwind_init(void)
	{
	init_unwind_table(&root_table, "kernel",
	_text, _end - _text,
	NULL, 0,
	__start_unwind, __end_unwind - __start_unwind);
	}

	#ifdef CONFIG_MODULES

	/* Must be called with module_mutex held. */
	void unwind_add_table(struct module module,
	const void *table_start,
	unsigned long table_size)
	{
	struct unwind_table *table;

	if (table_size <= 0)
	return NULL;

	table = kmalloc(sizeof(*table), GFP_KERNEL);
	if (!table)
	return NULL;

	init_unwind_table(table, module->name,
	module->module_core, module->core_size,
	module->module_init, module->init_size,
	table_start, table_size);

	if (last_table)
	last_table->link = table;
	else
	root_table.link = table;
	last_table = table;

	return table;
	}

	struct unlink_table_info
	{
	struct unwind_table *table;
	int init_only;
	};

	static int unlink_table(void *arg)
	{
	struct unlink_table_info *info = arg;
	struct unwind_table table = info->table, prev;

	for (prev = &root_table; prev->link && prev->link != table; prev = prev->link)
	;

	if (prev->link) {
	if (info->init_only) {
	table->init.pc = 0;
	table->init.range = 0;
	info->table = NULL;
	} else {
	prev->link = table->link;
	if (!prev->link)
	last_table = prev;
	}
	} else
	info->table = NULL;

	return 0;
	}

	/* Must be called with module_mutex held. */
	void unwind_remove_table(void *handle, int init_only)
	{
	struct unwind_table *table = handle;
	struct unlink_table_info info;

	if (!table \|\| table == &root_table)
	return;

	if (init_only && table == last_table) {
	table->init.pc = 0;
	table->init.range = 0;
	return;
	}

	info.table = table;
	info.init_only = init_only;
	stop_machine_run(unlink_table, &info, NR_CPUS);

	if (info.table)
	kfree(table);
	}

	#endif /* CONFIG_MODULES */

	static uleb128_t get_uleb128(const u8 *pcur, const u8 end)
	{
	const u8 cur = pcur;
	uleb128_t value;
	unsigned shift;

	for (shift = 0, value = 0; cur < end; shift += 7) {
	if (shift + 7 > 8 * sizeof(value)
	&& (cur & 0x7fU) >= (1U << (8 sizeof(value) - shift))) {
	cur = end + 1;
	break;
	}
	value \|= (uleb128_t)(*cur & 0x7f) << shift;
	if (!(*cur++ & 0x80))
	break;
	}
	*pcur = cur;

	return value;
	}

	static sleb128_t get_sleb128(const u8 *pcur, const u8 end)
	{
	const u8 cur = pcur;
	sleb128_t value;
	unsigned shift;

	for (shift = 0, value = 0; cur < end; shift += 7) {
	if (shift + 7 > 8 * sizeof(value)
	&& (cur & 0x7fU) >= (1U << (8 sizeof(value) - shift))) {
	cur = end + 1;
	break;
	}
	value \|= (sleb128_t)(*cur & 0x7f) << shift;
	if (!(*cur & 0x80)) {
	value \|= -(*cur++ & 0x40) << shift;
	break;
	}
	}
	*pcur = cur;

	return value;
	}

	static unsigned long read_pointer(const u8 **pLoc,
	const void *end,
	signed ptrType)
	{
	unsigned long value = 0;
	union {
	const u8 *p8;
	const u16 *p16u;
	const s16 *p16s;
	const u32 *p32u;
	const s32 *p32s;
	const unsigned long *pul;
	} ptr;

	if (ptrType < 0 \|\| ptrType == DW_EH_PE_omit)
	return 0;
	ptr.p8 = *pLoc;
	switch(ptrType & DW_EH_PE_FORM) {
	case DW_EH_PE_data2:
	if (end < (const void *)(ptr.p16u + 1))
	return 0;
	if(ptrType & DW_EH_PE_signed)
	value = get_unaligned(ptr.p16s++);
	else
	value = get_unaligned(ptr.p16u++);
	break;
	case DW_EH_PE_data4:
	#ifdef CONFIG_64BIT
	if (end < (const void *)(ptr.p32u + 1))
	return 0;
	if(ptrType & DW_EH_PE_signed)
	value = get_unaligned(ptr.p32s++);
	else
	value = get_unaligned(ptr.p32u++);
	break;
	case DW_EH_PE_data8:
	BUILD_BUG_ON(sizeof(u64) != sizeof(value));
	#else
	BUILD_BUG_ON(sizeof(u32) != sizeof(value));
	#endif
	case DW_EH_PE_native:
	if (end < (const void *)(ptr.pul + 1))
	return 0;
	value = get_unaligned(ptr.pul++);
	break;
	case DW_EH_PE_leb128:
	BUILD_BUG_ON(sizeof(uleb128_t) > sizeof(value));
	value = ptrType & DW_EH_PE_signed
	? get_sleb128(&ptr.p8, end)
	: get_uleb128(&ptr.p8, end);
	if ((const void *)ptr.p8 > end)
	return 0;
	break;
	default:
	return 0;
	}
	switch(ptrType & DW_EH_PE_ADJUST) {
	case DW_EH_PE_abs:
	break;
	case DW_EH_PE_pcrel:
	value += (unsigned long)*pLoc;
	break;
	default:
	return 0;
	}
	if ((ptrType & DW_EH_PE_indirect)
	&& __get_user(value, (unsigned long *)value))
	return 0;
	*pLoc = ptr.p8;

	return value;
	}

	static signed fde_pointer_type(const u32 *cie)
	{
	const u8 ptr = (const u8 )(cie + 2);
	unsigned version = *ptr;

	if (version != 1)
	return -1; /* unsupported */
	if (*++ptr) {
	const char *aug;
	const u8 end = (const u8 )(cie + 1) + *cie;
	uleb128_t len;

	/* check if augmentation size is first (and thus present) */
	if (*ptr != 'z')
	return -1;
	/* check if augmentation string is nul-terminated */
	if ((ptr = memchr(aug = (const void *)ptr, 0, end - ptr)) == NULL)
	return -1;
	++ptr; /* skip terminator */
	get_uleb128(&ptr, end); /* skip code alignment */
	get_sleb128(&ptr, end); /* skip data alignment */
	/* skip return address column */
	version <= 1 ? (void)++ptr : (void)get_uleb128(&ptr, end);
	len = get_uleb128(&ptr, end); /* augmentation length */
	if (ptr + len < ptr \|\| ptr + len > end)
	return -1;
	end = ptr + len;
	while (*++aug) {
	if (ptr >= end)
	return -1;
	switch(*aug) {
	case 'L':
	++ptr;
	break;
	case 'P': {
	signed ptrType = *ptr++;

	if (!read_pointer(&ptr, end, ptrType) \|\| ptr > end)
	return -1;
	}
	break;
	case 'R':
	return *ptr;
	default:
	return -1;
	}
	}
	}
	return DW_EH_PE_native\|DW_EH_PE_abs;
	}

	static int advance_loc(unsigned long delta, struct unwind_state *state)
	{
	state->loc += delta * state->codeAlign;

	return delta > 0;
	}

	static void set_rule(uleb128_t reg,
	enum item_location where,
	uleb128_t value,
	struct unwind_state *state)
	{
	if (reg < ARRAY_SIZE(state->regs)) {
	state->regs[reg].where = where;
	state->regs[reg].value = value;
	}
	}

	static int processCFI(const u8 *start,
	const u8 *end,
	unsigned long targetLoc,
	signed ptrType,
	struct unwind_state *state)
	{
	union {
	const u8 *p8;
	const u16 *p16;
	const u32 *p32;
	} ptr;
	int result = 1;

	if (start != state->cieStart) {
	state->loc = state->org;
	result = processCFI(state->cieStart, state->cieEnd, 0, ptrType, state);
	if (targetLoc == 0 && state->label == NULL)
	return result;
	}
	for (ptr.p8 = start; result && ptr.p8 < end; ) {
	switch(*ptr.p8 >> 6) {
	uleb128_t value;

	case 0:
	switch(*ptr.p8++) {
	case DW_CFA_nop:
	break;
	case DW_CFA_set_loc:
	if ((state->loc = read_pointer(&ptr.p8, end, ptrType)) == 0)
	result = 0;
	break;
	case DW_CFA_advance_loc1:
	result = ptr.p8 < end && advance_loc(*ptr.p8++, state);
	break;
	case DW_CFA_advance_loc2:
	result = ptr.p8 <= end + 2
	&& advance_loc(*ptr.p16++, state);
	break;
	case DW_CFA_advance_loc4:
	result = ptr.p8 <= end + 4
	&& advance_loc(*ptr.p32++, state);
	break;
	case DW_CFA_offset_extended:
	value = get_uleb128(&ptr.p8, end);
	set_rule(value, Memory, get_uleb128(&ptr.p8, end), state);
	break;
	case DW_CFA_val_offset:
	value = get_uleb128(&ptr.p8, end);
	set_rule(value, Value, get_uleb128(&ptr.p8, end), state);
	break;
	case DW_CFA_offset_extended_sf:
	value = get_uleb128(&ptr.p8, end);
	set_rule(value, Memory, get_sleb128(&ptr.p8, end), state);
	break;
	case DW_CFA_val_offset_sf:
	value = get_uleb128(&ptr.p8, end);
	set_rule(value, Value, get_sleb128(&ptr.p8, end), state);
	break;
	case DW_CFA_restore_extended:
	case DW_CFA_undefined:
	case DW_CFA_same_value:
	set_rule(get_uleb128(&ptr.p8, end), Nowhere, 0, state);
	break;
	case DW_CFA_register:
	value = get_uleb128(&ptr.p8, end);
	set_rule(value,
	Register,
	get_uleb128(&ptr.p8, end), state);
	break;
	case DW_CFA_remember_state:
	if (ptr.p8 == state->label) {
	state->label = NULL;
	return 1;
	}
	if (state->stackDepth >= MAX_STACK_DEPTH)
	return 0;
	state->stack[state->stackDepth++] = ptr.p8;
	break;
	case DW_CFA_restore_state:
	if (state->stackDepth) {
	const uleb128_t loc = state->loc;
	const u8 *label = state->label;

	state->label = state->stack[state->stackDepth - 1];
	memcpy(&state->cfa, &badCFA, sizeof(state->cfa));
	memset(state->regs, 0, sizeof(state->regs));
	state->stackDepth = 0;
	result = processCFI(start, end, 0, ptrType, state);
	state->loc = loc;
	state->label = label;
	} else
	return 0;
	break;
	case DW_CFA_def_cfa:
	state->cfa.reg = get_uleb128(&ptr.p8, end);
	/nobreak/
	case DW_CFA_def_cfa_offset:
	state->cfa.offs = get_uleb128(&ptr.p8, end);
	break;
	case DW_CFA_def_cfa_sf:
	state->cfa.reg = get_uleb128(&ptr.p8, end);
	/nobreak/
	case DW_CFA_def_cfa_offset_sf:
	state->cfa.offs = get_sleb128(&ptr.p8, end)
	* state->dataAlign;
	break;
	case DW_CFA_def_cfa_register:
	state->cfa.reg = get_uleb128(&ptr.p8, end);
	break;
	/todo case DW_CFA_def_cfa_expression: /
	/todo case DW_CFA_expression: /
	/todo case DW_CFA_val_expression: /
	case DW_CFA_GNU_args_size:
	get_uleb128(&ptr.p8, end);
	break;
	case DW_CFA_GNU_negative_offset_extended:
	value = get_uleb128(&ptr.p8, end);
	set_rule(value,
	Memory,
	(uleb128_t)0 - get_uleb128(&ptr.p8, end), state);
	break;
	case DW_CFA_GNU_window_save:
	default:
	result = 0;
	break;
	}
	break;
	case 1:
	result = advance_loc(*ptr.p8++ & 0x3f, state);
	break;
	case 2:
	value = *ptr.p8++ & 0x3f;
	set_rule(value, Memory, get_uleb128(&ptr.p8, end), state);
	break;
	case 3:
	set_rule(*ptr.p8++ & 0x3f, Nowhere, 0, state);
	break;
	}
	if (ptr.p8 > end)
	result = 0;
	if (result && targetLoc != 0 && targetLoc < state->loc)
	return 1;
	}

	return result
	&& ptr.p8 == end
	&& (targetLoc == 0
	\|\| (/*todo While in theory this should apply, gcc in practice omits
	everything past the function prolog, and hence the location
	never reaches the end of the function.
	targetLoc < state->loc &&*/ state->label == NULL));
	}

	/* Unwind to previous to frame. Returns 0 if successful, negative
	* number in case of an error. */
	int unwind(struct unwind_frame_info *frame)
	{
	#define FRAME_REG(r, t) (((t *)frame)[reg_info[r].offs])
	const u32 fde = NULL, cie = NULL;
	const u8 ptr = NULL, end = NULL;
	unsigned long startLoc = 0, endLoc = 0, cfa;
	unsigned i;
	signed ptrType = -1;
	uleb128_t retAddrReg = 0;
	struct unwind_table *table;
	struct unwind_state state;

	if (UNW_PC(frame) == 0)
	return -EINVAL;
	if ((table = find_table(UNW_PC(frame))) != NULL
	&& !(table->size & (sizeof(*fde) - 1))) {
	unsigned long tableSize = table->size;

	for (fde = table->address;
	tableSize > sizeof(fde) && tableSize - sizeof(fde) >= *fde;
	tableSize -= sizeof(fde) + fde,
	fde += 1 + fde / sizeof(fde)) {
	if (!fde \|\| (fde & (sizeof(*fde) - 1)))
	break;
	if (!fde[1])
	continue; /* this is a CIE */
	if ((fde[1] & (sizeof(*fde) - 1))
	\|\| fde[1] > (unsigned long)(fde + 1)
	- (unsigned long)table->address)
	continue; /* this is not a valid FDE */
	cie = fde + 1 - fde[1] / sizeof(*fde);
	if (cie <= sizeof(cie) + 4
	\|\| cie >= fde[1] - sizeof(fde)
	\|\| (cie & (sizeof(cie) - 1))
	\|\| cie[1]
	\|\| (ptrType = fde_pointer_type(cie)) < 0) {
	cie = NULL; /* this is not a (valid) CIE */
	continue;
	}
	ptr = (const u8 *)(fde + 2);
	startLoc = read_pointer(&ptr,
	(const u8 )(fde + 1) + fde,
	ptrType);
	endLoc = startLoc
	+ read_pointer(&ptr,
	(const u8 )(fde + 1) + fde,
	ptrType & DW_EH_PE_indirect
	? ptrType
	: ptrType & (DW_EH_PE_FORM\|DW_EH_PE_signed));
	if (UNW_PC(frame) >= startLoc && UNW_PC(frame) < endLoc)
	break;
	cie = NULL;
	}
	}
	if (cie != NULL) {
	memset(&state, 0, sizeof(state));
	state.cieEnd = ptr; /* keep here temporarily */
	ptr = (const u8 *)(cie + 2);
	end = (const u8 )(cie + 1) + cie;
	if ((state.version = *ptr) != 1)
	cie = NULL; /* unsupported version */
	else if (*++ptr) {
	/* check if augmentation size is first (and thus present) */
	if (*ptr == 'z') {
	/* check for ignorable (or already handled)
	* nul-terminated augmentation string */
	while (++ptr < end && *ptr)
	if (strchr("LPR", *ptr) == NULL)
	break;
	}
	if (ptr >= end \|\| *ptr)
	cie = NULL;
	}
	++ptr;
	}
	if (cie != NULL) {
	/* get code aligment factor */
	state.codeAlign = get_uleb128(&ptr, end);
	/* get data aligment factor */
	state.dataAlign = get_sleb128(&ptr, end);
	if (state.codeAlign == 0 \|\| state.dataAlign == 0 \|\| ptr >= end)
	cie = NULL;
	else {
	retAddrReg = state.version <= 1 ? *ptr++ : get_uleb128(&ptr, end);
	/* skip augmentation */
	if (((const char *)(cie + 2))[1] == 'z')
	ptr += get_uleb128(&ptr, end);
	if (ptr > end
	\|\| retAddrReg >= ARRAY_SIZE(reg_info)
	\|\| REG_INVALID(retAddrReg)
	\|\| reg_info[retAddrReg].width != sizeof(unsigned long))
	cie = NULL;
	}
	}
	if (cie != NULL) {
	state.cieStart = ptr;
	ptr = state.cieEnd;
	state.cieEnd = end;
	end = (const u8 )(fde + 1) + fde;
	/* skip augmentation */
	if (((const char *)(cie + 2))[1] == 'z') {
	uleb128_t augSize = get_uleb128(&ptr, end);

	if ((ptr += augSize) > end)
	fde = NULL;
	}
	}
	if (cie == NULL \|\| fde == NULL) {
	#ifdef CONFIG_FRAME_POINTER
	unsigned long top, bottom;
	#endif

	#ifdef CONFIG_FRAME_POINTER
	top = STACK_TOP(frame->task);
	bottom = STACK_BOTTOM(frame->task);
	# if FRAME_RETADDR_OFFSET < 0
	if (UNW_SP(frame) < top
	&& UNW_FP(frame) <= UNW_SP(frame)
	&& bottom < UNW_FP(frame)
	# else
	if (UNW_SP(frame) > top
	&& UNW_FP(frame) >= UNW_SP(frame)
	&& bottom > UNW_FP(frame)
	# endif
	&& !((UNW_SP(frame) \| UNW_FP(frame))
	& (sizeof(unsigned long) - 1))) {
	unsigned long link;

	if (!__get_user(link,
	(unsigned long *)(UNW_FP(frame)
	+ FRAME_LINK_OFFSET))
	# if FRAME_RETADDR_OFFSET < 0
	&& link > bottom && link < UNW_FP(frame)
	# else
	&& link > UNW_FP(frame) && link < bottom
	# endif
	&& !(link & (sizeof(link) - 1))
	&& !__get_user(UNW_PC(frame),
	(unsigned long *)(UNW_FP(frame)
	+ FRAME_RETADDR_OFFSET))) {
	UNW_SP(frame) = UNW_FP(frame) + FRAME_RETADDR_OFFSET
	# if FRAME_RETADDR_OFFSET < 0
	-
	# else
	+
	# endif
	sizeof(UNW_PC(frame));
	UNW_FP(frame) = link;
	return 0;
	}
	}
	#endif
	return -ENXIO;
	}
	state.org = startLoc;
	memcpy(&state.cfa, &badCFA, sizeof(state.cfa));
	/* process instructions */
	if (!processCFI(ptr, end, UNW_PC(frame), ptrType, &state)
	\|\| state.loc > endLoc
	\|\| state.regs[retAddrReg].where == Nowhere
	\|\| state.cfa.reg >= ARRAY_SIZE(reg_info)
	\|\| reg_info[state.cfa.reg].width != sizeof(unsigned long)
	\|\| state.cfa.offs % sizeof(unsigned long))
	return -EIO;
	/* update frame */
	cfa = FRAME_REG(state.cfa.reg, unsigned long) + state.cfa.offs;
	startLoc = min((unsigned long)UNW_SP(frame), cfa);
	endLoc = max((unsigned long)UNW_SP(frame), cfa);
	if (STACK_LIMIT(startLoc) != STACK_LIMIT(endLoc)) {
	startLoc = min(STACK_LIMIT(cfa), cfa);
	endLoc = max(STACK_LIMIT(cfa), cfa);
	}
	#ifndef CONFIG_64BIT
	# define CASES CASE(8); CASE(16); CASE(32)
	#else
	# define CASES CASE(8); CASE(16); CASE(32); CASE(64)
	#endif
	for (i = 0; i < ARRAY_SIZE(state.regs); ++i) {
	if (REG_INVALID(i)) {
	if (state.regs[i].where == Nowhere)
	continue;
	return -EIO;
	}
	switch(state.regs[i].where) {
	default:
	break;
	case Register:
	if (state.regs[i].value >= ARRAY_SIZE(reg_info)
	\|\| REG_INVALID(state.regs[i].value)
	\|\| reg_info[i].width > reg_info[state.regs[i].value].width)
	return -EIO;
	switch(reg_info[state.regs[i].value].width) {
	#define CASE(n) \
	case sizeof(u##n): \
	state.regs[i].value = FRAME_REG(state.regs[i].value, \
	const u##n); \
	break
	CASES;
	#undef CASE
	default:
	return -EIO;
	}
	break;
	}
	}
	for (i = 0; i < ARRAY_SIZE(state.regs); ++i) {
	if (REG_INVALID(i))
	continue;
	switch(state.regs[i].where) {
	case Nowhere:
	if (reg_info[i].width != sizeof(UNW_SP(frame))
	\|\| &FRAME_REG(i, __typeof__(UNW_SP(frame)))
	!= &UNW_SP(frame))
	continue;
	UNW_SP(frame) = cfa;
	break;
	case Register:
	switch(reg_info[i].width) {
	#define CASE(n) case sizeof(u##n): \
	FRAME_REG(i, u##n) = state.regs[i].value; \
	break
	CASES;
	#undef CASE
	default:
	return -EIO;
	}
	break;
	case Value:
	if (reg_info[i].width != sizeof(unsigned long))
	return -EIO;
	FRAME_REG(i, unsigned long) = cfa + state.regs[i].value
	* state.dataAlign;
	break;
	case Memory: {
	unsigned long addr = cfa + state.regs[i].value
	* state.dataAlign;

	if ((state.regs[i].value * state.dataAlign)
	% sizeof(unsigned long)
	\|\| addr < startLoc
	\|\| addr + sizeof(unsigned long) < addr
	\|\| addr + sizeof(unsigned long) > endLoc)
	return -EIO;
	switch(reg_info[i].width) {
	#define CASE(n) case sizeof(u##n): \
	__get_user(FRAME_REG(i, u##n), (u##n *)addr); \
	break
	CASES;
	#undef CASE
	default:
	return -EIO;
	}
	}
	break;
	}
	}

	return 0;
	#undef CASES
	#undef FRAME_REG
	}
	EXPORT_SYMBOL(unwind);

	int unwind_init_frame_info(struct unwind_frame_info *info,
	struct task_struct *tsk,
	/const/ struct pt_regs *regs)
	{
	info->task = tsk;
	arch_unw_init_frame_info(info, regs);

	return 0;
	}
	EXPORT_SYMBOL(unwind_init_frame_info);

	/*
	* Prepare to unwind a blocked task.
	*/
	int unwind_init_blocked(struct unwind_frame_info *info,
	struct task_struct *tsk)
	{
	info->task = tsk;
	arch_unw_init_blocked(info);

	return 0;
	}
	EXPORT_SYMBOL(unwind_init_blocked);

	/*
	* Prepare to unwind the currently running thread.
	*/
	int unwind_init_running(struct unwind_frame_info *info,
	asmlinkage int (callback)(struct unwind_frame_info ,
	void *arg),
	void *arg)
	{
	info->task = current;

	return arch_unwind_init_running(info, callback, arg);
	}
	EXPORT_SYMBOL(unwind_init_running);

	/*
	* Unwind until the return pointer is in user-land (or until an error
	* occurs). Returns 0 if successful, negative number in case of
	* error.
	*/
	int unwind_to_user(struct unwind_frame_info *info)
	{
	while (!arch_unw_user_mode(info)) {
	int err = unwind(info);

	if (err < 0)
	return err;
	}

	return 0;
	}
	EXPORT_SYMBOL(unwind_to_user);