arch/x86/kernel/unwind_orc.c - arm/linux - Git at Google

 #include <linux/module.h>
 #include <linux/sort.h>
 #include <asm/ptrace.h>
 #include <asm/stacktrace.h>
 #include <asm/unwind.h>
 #include <asm/orc_types.h>
 #include <asm/orc_lookup.h>
 #include <asm/sections.h>

 #define orc_warn(fmt, ...) \
 	printk_deferred_once(KERN_WARNING pr_fmt("WARNING: " fmt), ##__VA_ARGS__)

 extern int __start_orc_unwind_ip[];
 extern int __stop_orc_unwind_ip[];
 extern struct orc_entry __start_orc_unwind[];
 extern struct orc_entry __stop_orc_unwind[];

 static DEFINE_MUTEX(sort_mutex);
 int *cur_orc_ip_table = __start_orc_unwind_ip;
 struct orc_entry *cur_orc_table = __start_orc_unwind;

 unsigned int lookup_num_blocks;
 bool orc_init;

 static inline unsigned long orc_ip(const int *ip)
 {
 	return (unsigned long)ip + *ip;
 }

 static struct orc_entry *__orc_find(int *ip_table, struct orc_entry *u_table,
 				    unsigned int num_entries, unsigned long ip)
 {
 	int *first = ip_table;
 	int *last = ip_table + num_entries - 1;
 	int *mid = first, *found = first;

 	if (!num_entries)
 		return NULL;

 	/*
 	 * Do a binary range search to find the rightmost duplicate of a given
 	 * starting address.  Some entries are section terminators which are
 	 * "weak" entries for ensuring there are no gaps.  They should be
 	 * ignored when they conflict with a real entry.
 	 */
 	while (first <= last) {
 		mid = first + ((last - first) / 2);

 		if (orc_ip(mid) <= ip) {
 			found = mid;
 			first = mid + 1;
 		} else
 			last = mid - 1;
 	}

 	return u_table + (found - ip_table);
 }

 #ifdef CONFIG_MODULES
 static struct orc_entry *orc_module_find(unsigned long ip)
 {
 	struct module *mod;

 	mod = __module_address(ip);
 	if (!mod || !mod->arch.orc_unwind || !mod->arch.orc_unwind_ip)
 		return NULL;
 	return __orc_find(mod->arch.orc_unwind_ip, mod->arch.orc_unwind,
 			  mod->arch.num_orcs, ip);
 }
 #else
 static struct orc_entry *orc_module_find(unsigned long ip)
 {
 	return NULL;
 }
 #endif

 static struct orc_entry *orc_find(unsigned long ip)
 {
 	if (!orc_init)
 		return NULL;

 	/* For non-init vmlinux addresses, use the fast lookup table: */
 	if (ip >= LOOKUP_START_IP && ip < LOOKUP_STOP_IP) {
 		unsigned int idx, start, stop;

 		idx = (ip - LOOKUP_START_IP) / LOOKUP_BLOCK_SIZE;

 		if (unlikely((idx >= lookup_num_blocks-1))) {
 			orc_warn("WARNING: bad lookup idx: idx=%u num=%u ip=%lx\n",
 				 idx, lookup_num_blocks, ip);
 			return NULL;
 		}

 		start = orc_lookup[idx];
 		stop = orc_lookup[idx + 1] + 1;

 		if (unlikely((__start_orc_unwind + start >= __stop_orc_unwind) ||
 			     (__start_orc_unwind + stop > __stop_orc_unwind))) {
 			orc_warn("WARNING: bad lookup value: idx=%u num=%u start=%u stop=%u ip=%lx\n",
 				 idx, lookup_num_blocks, start, stop, ip);
 			return NULL;
 		}

 		return __orc_find(__start_orc_unwind_ip + start,
 				  __start_orc_unwind + start, stop - start, ip);
 	}

 	/* vmlinux .init slow lookup: */
 	if (ip >= (unsigned long)_sinittext && ip < (unsigned long)_einittext)
 		return __orc_find(__start_orc_unwind_ip, __start_orc_unwind,
 				  __stop_orc_unwind_ip - __start_orc_unwind_ip, ip);

 	/* Module lookup: */
 	return orc_module_find(ip);
 }

 static void orc_sort_swap(void *_a, void *_b, int size)
 {
 	struct orc_entry *orc_a, *orc_b;
 	struct orc_entry orc_tmp;
 	int *a = _a, *b = _b, tmp;
 	int delta = _b - _a;

 	/* Swap the .orc_unwind_ip entries: */
 	tmp = *a;
 	*a = *b + delta;
 	*b = tmp - delta;

 	/* Swap the corresponding .orc_unwind entries: */
 	orc_a = cur_orc_table + (a - cur_orc_ip_table);
 	orc_b = cur_orc_table + (b - cur_orc_ip_table);
 	orc_tmp = *orc_a;
 	*orc_a = *orc_b;
 	*orc_b = orc_tmp;
 }

 static int orc_sort_cmp(const void *_a, const void *_b)
 {
 	struct orc_entry *orc_a;
 	const int *a = _a, *b = _b;
 	unsigned long a_val = orc_ip(a);
 	unsigned long b_val = orc_ip(b);

 	if (a_val > b_val)
 		return 1;
 	if (a_val < b_val)
 		return -1;

 	/*
 	 * The "weak" section terminator entries need to always be on the left
 	 * to ensure the lookup code skips them in favor of real entries.
 	 * These terminator entries exist to handle any gaps created by
 	 * whitelisted .o files which didn't get objtool generation.
 	 */
 	orc_a = cur_orc_table + (a - cur_orc_ip_table);
 	return orc_a->sp_reg == ORC_REG_UNDEFINED ? -1 : 1;
 }

 #ifdef CONFIG_MODULES
 void unwind_module_init(struct module *mod, void *_orc_ip, size_t orc_ip_size,
 			void *_orc, size_t orc_size)
 {
 	int *orc_ip = _orc_ip;
 	struct orc_entry *orc = _orc;
 	unsigned int num_entries = orc_ip_size / sizeof(int);

 	WARN_ON_ONCE(orc_ip_size % sizeof(int) != 0 ||
 		     orc_size % sizeof(*orc) != 0 ||
 		     num_entries != orc_size / sizeof(*orc));

 	/*
 	 * The 'cur_orc_*' globals allow the orc_sort_swap() callback to
 	 * associate an .orc_unwind_ip table entry with its corresponding
 	 * .orc_unwind entry so they can both be swapped.
 	 */
 	mutex_lock(&sort_mutex);
 	cur_orc_ip_table = orc_ip;
 	cur_orc_table = orc;
 	sort(orc_ip, num_entries, sizeof(int), orc_sort_cmp, orc_sort_swap);
 	mutex_unlock(&sort_mutex);

 	mod->arch.orc_unwind_ip = orc_ip;
 	mod->arch.orc_unwind = orc;
 	mod->arch.num_orcs = num_entries;
 }
 #endif

 void __init unwind_init(void)
 {
 	size_t orc_ip_size = (void *)__stop_orc_unwind_ip - (void *)__start_orc_unwind_ip;
 	size_t orc_size = (void *)__stop_orc_unwind - (void *)__start_orc_unwind;
 	size_t num_entries = orc_ip_size / sizeof(int);
 	struct orc_entry *orc;
 	int i;

 	if (!num_entries || orc_ip_size % sizeof(int) != 0 ||
 	    orc_size % sizeof(struct orc_entry) != 0 ||
 	    num_entries != orc_size / sizeof(struct orc_entry)) {
 		orc_warn("WARNING: Bad or missing .orc_unwind table.  Disabling unwinder.\n");
 		return;
 	}

 	/* Sort the .orc_unwind and .orc_unwind_ip tables: */
 	sort(__start_orc_unwind_ip, num_entries, sizeof(int), orc_sort_cmp,
 	     orc_sort_swap);

 	/* Initialize the fast lookup table: */
 	lookup_num_blocks = orc_lookup_end - orc_lookup;
 	for (i = 0; i < lookup_num_blocks-1; i++) {
 		orc = __orc_find(__start_orc_unwind_ip, __start_orc_unwind,
 				 num_entries,
 				 LOOKUP_START_IP + (LOOKUP_BLOCK_SIZE * i));
 		if (!orc) {
 			orc_warn("WARNING: Corrupt .orc_unwind table.  Disabling unwinder.\n");
 			return;
 		}

 		orc_lookup[i] = orc - __start_orc_unwind;
 	}

 	/* Initialize the ending block: */
 	orc = __orc_find(__start_orc_unwind_ip, __start_orc_unwind, num_entries,
 			 LOOKUP_STOP_IP);
 	if (!orc) {
 		orc_warn("WARNING: Corrupt .orc_unwind table.  Disabling unwinder.\n");
 		return;
 	}
 	orc_lookup[lookup_num_blocks-1] = orc - __start_orc_unwind;

 	orc_init = true;
 }

 unsigned long unwind_get_return_address(struct unwind_state *state)
 {
 	if (unwind_done(state))
 		return 0;

 	return __kernel_text_address(state->ip) ? state->ip : 0;
 }
 EXPORT_SYMBOL_GPL(unwind_get_return_address);

 unsigned long *unwind_get_return_address_ptr(struct unwind_state *state)
 {
 	if (unwind_done(state))
 		return NULL;

 	if (state->regs)
 		return &state->regs->ip;

 	if (state->sp)
 		return (unsigned long *)state->sp - 1;

 	return NULL;
 }

 static bool stack_access_ok(struct unwind_state *state, unsigned long addr,
 			    size_t len)
 {
 	struct stack_info *info = &state->stack_info;

 	/*
 	 * If the address isn't on the current stack, switch to the next one.
 	 *
 	 * We may have to traverse multiple stacks to deal with the possibility
 	 * that info->next_sp could point to an empty stack and the address
 	 * could be on a subsequent stack.
 	 */
 	while (!on_stack(info, (void *)addr, len))
 		if (get_stack_info(info->next_sp, state->task, info,
 				   &state->stack_mask))
 			return false;

 	return true;
 }

 static bool deref_stack_reg(struct unwind_state *state, unsigned long addr,
 			    unsigned long *val)
 {
 	if (!stack_access_ok(state, addr, sizeof(long)))
 		return false;

 	*val = READ_ONCE_TASK_STACK(state->task, *(unsigned long *)addr);
 	return true;
 }

 #define REGS_SIZE (sizeof(struct pt_regs))
 #define SP_OFFSET (offsetof(struct pt_regs, sp))
 #define IRET_REGS_SIZE (REGS_SIZE - offsetof(struct pt_regs, ip))
 #define IRET_SP_OFFSET (SP_OFFSET - offsetof(struct pt_regs, ip))

 static bool deref_stack_regs(struct unwind_state *state, unsigned long addr,
 			     unsigned long *ip, unsigned long *sp, bool full)
 {
 	size_t regs_size = full ? REGS_SIZE : IRET_REGS_SIZE;
 	size_t sp_offset = full ? SP_OFFSET : IRET_SP_OFFSET;
 	struct pt_regs *regs = (struct pt_regs *)(addr + regs_size - REGS_SIZE);

 	if (IS_ENABLED(CONFIG_X86_64)) {
 		if (!stack_access_ok(state, addr, regs_size))
 			return false;

 		*ip = regs->ip;
 		*sp = regs->sp;

 		return true;
 	}

 	if (!stack_access_ok(state, addr, sp_offset))
 		return false;

 	*ip = regs->ip;

 	if (user_mode(regs)) {
 		if (!stack_access_ok(state, addr + sp_offset,
 				     REGS_SIZE - SP_OFFSET))
 			return false;

 		*sp = regs->sp;
 	} else
 		*sp = (unsigned long)&regs->sp;

 	return true;
 }

 bool unwind_next_frame(struct unwind_state *state)
 {
 	unsigned long ip_p, sp, orig_ip, prev_sp = state->sp;
 	enum stack_type prev_type = state->stack_info.type;
 	struct orc_entry *orc;
 	struct pt_regs *ptregs;
 	bool indirect = false;

 	if (unwind_done(state))
 		return false;

 	/* Don't let modules unload while we're reading their ORC data. */
 	preempt_disable();

 	/* Have we reached the end? */
 	if (state->regs && user_mode(state->regs))
 		goto done;

 	/*
 	 * Find the orc_entry associated with the text address.
 	 *
 	 * Decrement call return addresses by one so they work for sibling
 	 * calls and calls to noreturn functions.
 	 */
 	orc = orc_find(state->signal ? state->ip : state->ip - 1);
 	if (!orc || orc->sp_reg == ORC_REG_UNDEFINED)
 		goto done;
 	orig_ip = state->ip;

 	/* Find the previous frame's stack: */
 	switch (orc->sp_reg) {
 	case ORC_REG_SP:
 		sp = state->sp + orc->sp_offset;
 		break;

 	case ORC_REG_BP:
 		sp = state->bp + orc->sp_offset;
 		break;

 	case ORC_REG_SP_INDIRECT:
 		sp = state->sp + orc->sp_offset;
 		indirect = true;
 		break;

 	case ORC_REG_BP_INDIRECT:
 		sp = state->bp + orc->sp_offset;
 		indirect = true;
 		break;

 	case ORC_REG_R10:
 		if (!state->regs || !state->full_regs) {
 			orc_warn("missing regs for base reg R10 at ip %p\n",
 				 (void *)state->ip);
 			goto done;
 		}
 		sp = state->regs->r10;
 		break;

 	case ORC_REG_R13:
 		if (!state->regs || !state->full_regs) {
 			orc_warn("missing regs for base reg R13 at ip %p\n",
 				 (void *)state->ip);
 			goto done;
 		}
 		sp = state->regs->r13;
 		break;

 	case ORC_REG_DI:
 		if (!state->regs || !state->full_regs) {
 			orc_warn("missing regs for base reg DI at ip %p\n",
 				 (void *)state->ip);
 			goto done;
 		}
 		sp = state->regs->di;
 		break;

 	case ORC_REG_DX:
 		if (!state->regs || !state->full_regs) {
 			orc_warn("missing regs for base reg DX at ip %p\n",
 				 (void *)state->ip);
 			goto done;
 		}
 		sp = state->regs->dx;
 		break;

 	default:
 		orc_warn("unknown SP base reg %d for ip %p\n",
 			 orc->sp_reg, (void *)state->ip);
 		goto done;
 	}

 	if (indirect) {
 		if (!deref_stack_reg(state, sp, &sp))
 			goto done;
 	}

 	/* Find IP, SP and possibly regs: */
 	switch (orc->type) {
 	case ORC_TYPE_CALL:
 		ip_p = sp - sizeof(long);

 		if (!deref_stack_reg(state, ip_p, &state->ip))
 			goto done;

 		state->ip = ftrace_graph_ret_addr(state->task, &state->graph_idx,
 						  state->ip, (void *)ip_p);

 		state->sp = sp;
 		state->regs = NULL;
 		state->signal = false;
 		break;

 	case ORC_TYPE_REGS:
 		if (!deref_stack_regs(state, sp, &state->ip, &state->sp, true)) {
 			orc_warn("can't dereference registers at %p for ip %p\n",
 				 (void *)sp, (void *)orig_ip);
 			goto done;
 		}

 		state->regs = (struct pt_regs *)sp;
 		state->full_regs = true;
 		state->signal = true;
 		break;

 	case ORC_TYPE_REGS_IRET:
 		if (!deref_stack_regs(state, sp, &state->ip, &state->sp, false)) {
 			orc_warn("can't dereference iret registers at %p for ip %p\n",
 				 (void *)sp, (void *)orig_ip);
 			goto done;
 		}

 		ptregs = container_of((void *)sp, struct pt_regs, ip);
 		if ((unsigned long)ptregs >= prev_sp &&
 		    on_stack(&state->stack_info, ptregs, REGS_SIZE)) {
 			state->regs = ptregs;
 			state->full_regs = false;
 		} else
 			state->regs = NULL;

 		state->signal = true;
 		break;

 	default:
 		orc_warn("unknown .orc_unwind entry type %d\n", orc->type);
 		break;
 	}

 	/* Find BP: */
 	switch (orc->bp_reg) {
 	case ORC_REG_UNDEFINED:
 		if (state->regs && state->full_regs)
 			state->bp = state->regs->bp;
 		break;

 	case ORC_REG_PREV_SP:
 		if (!deref_stack_reg(state, sp + orc->bp_offset, &state->bp))
 			goto done;
 		break;

 	case ORC_REG_BP:
 		if (!deref_stack_reg(state, state->bp + orc->bp_offset, &state->bp))
 			goto done;
 		break;

 	default:
 		orc_warn("unknown BP base reg %d for ip %p\n",
 			 orc->bp_reg, (void *)orig_ip);
 		goto done;
 	}

 	/* Prevent a recursive loop due to bad ORC data: */
 	if (state->stack_info.type == prev_type &&
 	    on_stack(&state->stack_info, (void *)state->sp, sizeof(long)) &&
 	    state->sp <= prev_sp) {
 		orc_warn("stack going in the wrong direction? ip=%p\n",
 			 (void *)orig_ip);
 		goto done;
 	}

 	preempt_enable();
 	return true;

 done:
 	preempt_enable();
 	state->stack_info.type = STACK_TYPE_UNKNOWN;
 	return false;
 }
 EXPORT_SYMBOL_GPL(unwind_next_frame);

 void __unwind_start(struct unwind_state *state, struct task_struct *task,
 		    struct pt_regs *regs, unsigned long *first_frame)
 {
 	memset(state, 0, sizeof(*state));
 	state->task = task;

 	/*
 	 * Refuse to unwind the stack of a task while it's executing on another
 	 * CPU.  This check is racy, but that's ok: the unwinder has other
 	 * checks to prevent it from going off the rails.
 	 */
 	if (task_on_another_cpu(task))
 		goto done;

 	if (regs) {
 		if (user_mode(regs))
 			goto done;

 		state->ip = regs->ip;
 		state->sp = kernel_stack_pointer(regs);
 		state->bp = regs->bp;
 		state->regs = regs;
 		state->full_regs = true;
 		state->signal = true;

 	} else if (task == current) {
 		asm volatile("lea (%%rip), %0\n\t"
 			     "mov %%rsp, %1\n\t"
 			     "mov %%rbp, %2\n\t"
 			     : "=r" (state->ip), "=r" (state->sp),
 			       "=r" (state->bp));

 	} else {
 		struct inactive_task_frame *frame = (void *)task->thread.sp;

 		state->sp = task->thread.sp;
 		state->bp = READ_ONCE_NOCHECK(frame->bp);
 		state->ip = READ_ONCE_NOCHECK(frame->ret_addr);
 	}

 	if (get_stack_info((unsigned long *)state->sp, state->task,
 			   &state->stack_info, &state->stack_mask))
 		return;

 	/*
 	 * The caller can provide the address of the first frame directly
 	 * (first_frame) or indirectly (regs->sp) to indicate which stack frame
 	 * to start unwinding at.  Skip ahead until we reach it.
 	 */

 	/* When starting from regs, skip the regs frame: */
 	if (regs) {
 		unwind_next_frame(state);
 		return;
 	}

 	/* Otherwise, skip ahead to the user-specified starting frame: */
 	while (!unwind_done(state) &&
 	       (!on_stack(&state->stack_info, first_frame, sizeof(long)) ||
 			state->sp <= (unsigned long)first_frame))
 		unwind_next_frame(state);

 	return;

 done:
 	state->stack_info.type = STACK_TYPE_UNKNOWN;
 	return;
 }
 EXPORT_SYMBOL_GPL(__unwind_start);
	#include <linux/module.h>
	#include <linux/sort.h>
	#include <asm/ptrace.h>
	#include <asm/stacktrace.h>
	#include <asm/unwind.h>
	#include <asm/orc_types.h>
	#include <asm/orc_lookup.h>
	#include <asm/sections.h>

	#define orc_warn(fmt, ...) \
	printk_deferred_once(KERN_WARNING pr_fmt("WARNING: " fmt), ##__VA_ARGS__)

	extern int __start_orc_unwind_ip[];
	extern int __stop_orc_unwind_ip[];
	extern struct orc_entry __start_orc_unwind[];
	extern struct orc_entry __stop_orc_unwind[];

	static DEFINE_MUTEX(sort_mutex);
	int *cur_orc_ip_table = __start_orc_unwind_ip;
	struct orc_entry *cur_orc_table = __start_orc_unwind;

	unsigned int lookup_num_blocks;
	bool orc_init;

	static inline unsigned long orc_ip(const int *ip)
	{
	return (unsigned long)ip + *ip;
	}

	static struct orc_entry __orc_find(int ip_table, struct orc_entry *u_table,
	unsigned int num_entries, unsigned long ip)
	{
	int *first = ip_table;
	int *last = ip_table + num_entries - 1;
	int mid = first, found = first;

	if (!num_entries)
	return NULL;

	/*
	* Do a binary range search to find the rightmost duplicate of a given
	* starting address. Some entries are section terminators which are
	* "weak" entries for ensuring there are no gaps. They should be
	* ignored when they conflict with a real entry.
	*/
	while (first <= last) {
	mid = first + ((last - first) / 2);

	if (orc_ip(mid) <= ip) {
	found = mid;
	first = mid + 1;
	} else
	last = mid - 1;
	}

	return u_table + (found - ip_table);
	}

	#ifdef CONFIG_MODULES
	static struct orc_entry *orc_module_find(unsigned long ip)
	{
	struct module *mod;

	mod = __module_address(ip);
	if (!mod \|\| !mod->arch.orc_unwind \|\| !mod->arch.orc_unwind_ip)
	return NULL;
	return __orc_find(mod->arch.orc_unwind_ip, mod->arch.orc_unwind,
	mod->arch.num_orcs, ip);
	}
	#else
	static struct orc_entry *orc_module_find(unsigned long ip)
	{
	return NULL;
	}
	#endif

	static struct orc_entry *orc_find(unsigned long ip)
	{
	if (!orc_init)
	return NULL;

	/* For non-init vmlinux addresses, use the fast lookup table: */
	if (ip >= LOOKUP_START_IP && ip < LOOKUP_STOP_IP) {
	unsigned int idx, start, stop;

	idx = (ip - LOOKUP_START_IP) / LOOKUP_BLOCK_SIZE;

	if (unlikely((idx >= lookup_num_blocks-1))) {
	orc_warn("WARNING: bad lookup idx: idx=%u num=%u ip=%lx\n",
	idx, lookup_num_blocks, ip);
	return NULL;
	}

	start = orc_lookup[idx];
	stop = orc_lookup[idx + 1] + 1;

	if (unlikely((__start_orc_unwind + start >= __stop_orc_unwind) \|\|
	(__start_orc_unwind + stop > __stop_orc_unwind))) {
	orc_warn("WARNING: bad lookup value: idx=%u num=%u start=%u stop=%u ip=%lx\n",
	idx, lookup_num_blocks, start, stop, ip);
	return NULL;
	}

	return __orc_find(__start_orc_unwind_ip + start,
	__start_orc_unwind + start, stop - start, ip);
	}

	/* vmlinux .init slow lookup: */
	if (ip >= (unsigned long)_sinittext && ip < (unsigned long)_einittext)
	return __orc_find(__start_orc_unwind_ip, __start_orc_unwind,
	__stop_orc_unwind_ip - __start_orc_unwind_ip, ip);

	/* Module lookup: */
	return orc_module_find(ip);
	}

	static void orc_sort_swap(void _a, void _b, int size)
	{
	struct orc_entry orc_a, orc_b;
	struct orc_entry orc_tmp;
	int a = _a, b = _b, tmp;
	int delta = _b - _a;

	/* Swap the .orc_unwind_ip entries: */
	tmp = *a;
	a = b + delta;
	*b = tmp - delta;

	/* Swap the corresponding .orc_unwind entries: */
	orc_a = cur_orc_table + (a - cur_orc_ip_table);
	orc_b = cur_orc_table + (b - cur_orc_ip_table);
	orc_tmp = *orc_a;
	orc_a = orc_b;
	*orc_b = orc_tmp;
	}

	static int orc_sort_cmp(const void _a, const void _b)
	{
	struct orc_entry *orc_a;
	const int a = _a, b = _b;
	unsigned long a_val = orc_ip(a);
	unsigned long b_val = orc_ip(b);

	if (a_val > b_val)
	return 1;
	if (a_val < b_val)
	return -1;

	/*
	* The "weak" section terminator entries need to always be on the left
	* to ensure the lookup code skips them in favor of real entries.
	* These terminator entries exist to handle any gaps created by
	* whitelisted .o files which didn't get objtool generation.
	*/
	orc_a = cur_orc_table + (a - cur_orc_ip_table);
	return orc_a->sp_reg == ORC_REG_UNDEFINED ? -1 : 1;
	}

	#ifdef CONFIG_MODULES
	void unwind_module_init(struct module mod, void _orc_ip, size_t orc_ip_size,
	void *_orc, size_t orc_size)
	{
	int *orc_ip = _orc_ip;
	struct orc_entry *orc = _orc;
	unsigned int num_entries = orc_ip_size / sizeof(int);

	WARN_ON_ONCE(orc_ip_size % sizeof(int) != 0 \|\|
	orc_size % sizeof(*orc) != 0 \|\|
	num_entries != orc_size / sizeof(*orc));

	/*
	* The 'cur_orc_*' globals allow the orc_sort_swap() callback to
	* associate an .orc_unwind_ip table entry with its corresponding
	* .orc_unwind entry so they can both be swapped.
	*/
	mutex_lock(&sort_mutex);
	cur_orc_ip_table = orc_ip;
	cur_orc_table = orc;
	sort(orc_ip, num_entries, sizeof(int), orc_sort_cmp, orc_sort_swap);
	mutex_unlock(&sort_mutex);

	mod->arch.orc_unwind_ip = orc_ip;
	mod->arch.orc_unwind = orc;
	mod->arch.num_orcs = num_entries;
	}
	#endif

	void __init unwind_init(void)
	{
	size_t orc_ip_size = (void )__stop_orc_unwind_ip - (void )__start_orc_unwind_ip;
	size_t orc_size = (void )__stop_orc_unwind - (void )__start_orc_unwind;
	size_t num_entries = orc_ip_size / sizeof(int);
	struct orc_entry *orc;
	int i;

	if (!num_entries \|\| orc_ip_size % sizeof(int) != 0 \|\|
	orc_size % sizeof(struct orc_entry) != 0 \|\|
	num_entries != orc_size / sizeof(struct orc_entry)) {
	orc_warn("WARNING: Bad or missing .orc_unwind table. Disabling unwinder.\n");
	return;
	}

	/* Sort the .orc_unwind and .orc_unwind_ip tables: */
	sort(__start_orc_unwind_ip, num_entries, sizeof(int), orc_sort_cmp,
	orc_sort_swap);

	/* Initialize the fast lookup table: */
	lookup_num_blocks = orc_lookup_end - orc_lookup;
	for (i = 0; i < lookup_num_blocks-1; i++) {
	orc = __orc_find(__start_orc_unwind_ip, __start_orc_unwind,
	num_entries,
	LOOKUP_START_IP + (LOOKUP_BLOCK_SIZE * i));
	if (!orc) {
	orc_warn("WARNING: Corrupt .orc_unwind table. Disabling unwinder.\n");
	return;
	}

	orc_lookup[i] = orc - __start_orc_unwind;
	}

	/* Initialize the ending block: */
	orc = __orc_find(__start_orc_unwind_ip, __start_orc_unwind, num_entries,
	LOOKUP_STOP_IP);
	if (!orc) {
	orc_warn("WARNING: Corrupt .orc_unwind table. Disabling unwinder.\n");
	return;
	}
	orc_lookup[lookup_num_blocks-1] = orc - __start_orc_unwind;

	orc_init = true;
	}

	unsigned long unwind_get_return_address(struct unwind_state *state)
	{
	if (unwind_done(state))
	return 0;

	return __kernel_text_address(state->ip) ? state->ip : 0;
	}
	EXPORT_SYMBOL_GPL(unwind_get_return_address);

	unsigned long unwind_get_return_address_ptr(struct unwind_state state)
	{
	if (unwind_done(state))
	return NULL;

	if (state->regs)
	return &state->regs->ip;

	if (state->sp)
	return (unsigned long *)state->sp - 1;

	return NULL;
	}

	static bool stack_access_ok(struct unwind_state *state, unsigned long addr,
	size_t len)
	{
	struct stack_info *info = &state->stack_info;

	/*
	* If the address isn't on the current stack, switch to the next one.
	*
	* We may have to traverse multiple stacks to deal with the possibility
	* that info->next_sp could point to an empty stack and the address
	* could be on a subsequent stack.
	*/
	while (!on_stack(info, (void *)addr, len))
	if (get_stack_info(info->next_sp, state->task, info,
	&state->stack_mask))
	return false;

	return true;
	}

	static bool deref_stack_reg(struct unwind_state *state, unsigned long addr,
	unsigned long *val)
	{
	if (!stack_access_ok(state, addr, sizeof(long)))
	return false;

	val = READ_ONCE_TASK_STACK(state->task, (unsigned long *)addr);
	return true;
	}

	#define REGS_SIZE (sizeof(struct pt_regs))
	#define SP_OFFSET (offsetof(struct pt_regs, sp))
	#define IRET_REGS_SIZE (REGS_SIZE - offsetof(struct pt_regs, ip))
	#define IRET_SP_OFFSET (SP_OFFSET - offsetof(struct pt_regs, ip))

	static bool deref_stack_regs(struct unwind_state *state, unsigned long addr,
	unsigned long ip, unsigned long sp, bool full)
	{
	size_t regs_size = full ? REGS_SIZE : IRET_REGS_SIZE;
	size_t sp_offset = full ? SP_OFFSET : IRET_SP_OFFSET;
	struct pt_regs regs = (struct pt_regs )(addr + regs_size - REGS_SIZE);

	if (IS_ENABLED(CONFIG_X86_64)) {
	if (!stack_access_ok(state, addr, regs_size))
	return false;

	*ip = regs->ip;
	*sp = regs->sp;

	return true;
	}

	if (!stack_access_ok(state, addr, sp_offset))
	return false;

	*ip = regs->ip;

	if (user_mode(regs)) {
	if (!stack_access_ok(state, addr + sp_offset,
	REGS_SIZE - SP_OFFSET))
	return false;

	*sp = regs->sp;
	} else
	*sp = (unsigned long)&regs->sp;

	return true;
	}

	bool unwind_next_frame(struct unwind_state *state)
	{
	unsigned long ip_p, sp, orig_ip, prev_sp = state->sp;
	enum stack_type prev_type = state->stack_info.type;
	struct orc_entry *orc;
	struct pt_regs *ptregs;
	bool indirect = false;

	if (unwind_done(state))
	return false;

	/* Don't let modules unload while we're reading their ORC data. */
	preempt_disable();

	/* Have we reached the end? */
	if (state->regs && user_mode(state->regs))
	goto done;

	/*
	* Find the orc_entry associated with the text address.
	*
	* Decrement call return addresses by one so they work for sibling
	* calls and calls to noreturn functions.
	*/
	orc = orc_find(state->signal ? state->ip : state->ip - 1);
	if (!orc \|\| orc->sp_reg == ORC_REG_UNDEFINED)
	goto done;
	orig_ip = state->ip;

	/* Find the previous frame's stack: */
	switch (orc->sp_reg) {
	case ORC_REG_SP:
	sp = state->sp + orc->sp_offset;
	break;

	case ORC_REG_BP:
	sp = state->bp + orc->sp_offset;
	break;

	case ORC_REG_SP_INDIRECT:
	sp = state->sp + orc->sp_offset;
	indirect = true;
	break;

	case ORC_REG_BP_INDIRECT:
	sp = state->bp + orc->sp_offset;
	indirect = true;
	break;

	case ORC_REG_R10:
	if (!state->regs \|\| !state->full_regs) {
	orc_warn("missing regs for base reg R10 at ip %p\n",
	(void *)state->ip);
	goto done;
	}
	sp = state->regs->r10;
	break;

	case ORC_REG_R13:
	if (!state->regs \|\| !state->full_regs) {
	orc_warn("missing regs for base reg R13 at ip %p\n",
	(void *)state->ip);
	goto done;
	}
	sp = state->regs->r13;
	break;

	case ORC_REG_DI:
	if (!state->regs \|\| !state->full_regs) {
	orc_warn("missing regs for base reg DI at ip %p\n",
	(void *)state->ip);
	goto done;
	}
	sp = state->regs->di;
	break;

	case ORC_REG_DX:
	if (!state->regs \|\| !state->full_regs) {
	orc_warn("missing regs for base reg DX at ip %p\n",
	(void *)state->ip);
	goto done;
	}
	sp = state->regs->dx;
	break;

	default:
	orc_warn("unknown SP base reg %d for ip %p\n",
	orc->sp_reg, (void *)state->ip);
	goto done;
	}

	if (indirect) {
	if (!deref_stack_reg(state, sp, &sp))
	goto done;
	}

	/* Find IP, SP and possibly regs: */
	switch (orc->type) {
	case ORC_TYPE_CALL:
	ip_p = sp - sizeof(long);

	if (!deref_stack_reg(state, ip_p, &state->ip))
	goto done;

	state->ip = ftrace_graph_ret_addr(state->task, &state->graph_idx,
	state->ip, (void *)ip_p);

	state->sp = sp;
	state->regs = NULL;
	state->signal = false;
	break;

	case ORC_TYPE_REGS:
	if (!deref_stack_regs(state, sp, &state->ip, &state->sp, true)) {
	orc_warn("can't dereference registers at %p for ip %p\n",
	(void )sp, (void )orig_ip);
	goto done;
	}

	state->regs = (struct pt_regs *)sp;
	state->full_regs = true;
	state->signal = true;
	break;

	case ORC_TYPE_REGS_IRET:
	if (!deref_stack_regs(state, sp, &state->ip, &state->sp, false)) {
	orc_warn("can't dereference iret registers at %p for ip %p\n",
	(void )sp, (void )orig_ip);
	goto done;
	}

	ptregs = container_of((void *)sp, struct pt_regs, ip);
	if ((unsigned long)ptregs >= prev_sp &&
	on_stack(&state->stack_info, ptregs, REGS_SIZE)) {
	state->regs = ptregs;
	state->full_regs = false;
	} else
	state->regs = NULL;

	state->signal = true;
	break;

	default:
	orc_warn("unknown .orc_unwind entry type %d\n", orc->type);
	break;
	}

	/* Find BP: */
	switch (orc->bp_reg) {
	case ORC_REG_UNDEFINED:
	if (state->regs && state->full_regs)
	state->bp = state->regs->bp;
	break;

	case ORC_REG_PREV_SP:
	if (!deref_stack_reg(state, sp + orc->bp_offset, &state->bp))
	goto done;
	break;

	case ORC_REG_BP:
	if (!deref_stack_reg(state, state->bp + orc->bp_offset, &state->bp))
	goto done;
	break;

	default:
	orc_warn("unknown BP base reg %d for ip %p\n",
	orc->bp_reg, (void *)orig_ip);
	goto done;
	}

	/* Prevent a recursive loop due to bad ORC data: */
	if (state->stack_info.type == prev_type &&
	on_stack(&state->stack_info, (void *)state->sp, sizeof(long)) &&
	state->sp <= prev_sp) {
	orc_warn("stack going in the wrong direction? ip=%p\n",
	(void *)orig_ip);
	goto done;
	}

	preempt_enable();
	return true;

	done:
	preempt_enable();
	state->stack_info.type = STACK_TYPE_UNKNOWN;
	return false;
	}
	EXPORT_SYMBOL_GPL(unwind_next_frame);

	void __unwind_start(struct unwind_state state, struct task_struct task,
	struct pt_regs regs, unsigned long first_frame)
	{
	memset(state, 0, sizeof(*state));
	state->task = task;

	/*
	* Refuse to unwind the stack of a task while it's executing on another
	* CPU. This check is racy, but that's ok: the unwinder has other
	* checks to prevent it from going off the rails.
	*/
	if (task_on_another_cpu(task))
	goto done;

	if (regs) {
	if (user_mode(regs))
	goto done;

	state->ip = regs->ip;
	state->sp = kernel_stack_pointer(regs);
	state->bp = regs->bp;
	state->regs = regs;
	state->full_regs = true;
	state->signal = true;

	} else if (task == current) {
	asm volatile("lea (%%rip), %0\n\t"
	"mov %%rsp, %1\n\t"
	"mov %%rbp, %2\n\t"
	: "=r" (state->ip), "=r" (state->sp),
	"=r" (state->bp));

	} else {
	struct inactive_task_frame frame = (void )task->thread.sp;

	state->sp = task->thread.sp;
	state->bp = READ_ONCE_NOCHECK(frame->bp);
	state->ip = READ_ONCE_NOCHECK(frame->ret_addr);
	}

	if (get_stack_info((unsigned long *)state->sp, state->task,
	&state->stack_info, &state->stack_mask))
	return;

	/*
	* The caller can provide the address of the first frame directly
	* (first_frame) or indirectly (regs->sp) to indicate which stack frame
	* to start unwinding at. Skip ahead until we reach it.
	*/

	/* When starting from regs, skip the regs frame: */
	if (regs) {
	unwind_next_frame(state);
	return;
	}

	/* Otherwise, skip ahead to the user-specified starting frame: */
	while (!unwind_done(state) &&
	(!on_stack(&state->stack_info, first_frame, sizeof(long)) \|\|
	state->sp <= (unsigned long)first_frame))
	unwind_next_frame(state);

	return;

	done:
	state->stack_info.type = STACK_TYPE_UNKNOWN;
	return;
	}
	EXPORT_SYMBOL_GPL(__unwind_start);