[linux-2.6-block.git] / arch / x86 / kernel / unwind_frame.c

#include <linux/sched.h>
#include <linux/sched/task.h>
#include <linux/sched/task_stack.h>
#include <linux/interrupt.h>
#include <asm/sections.h>
#include <asm/ptrace.h>
#include <asm/bitops.h>
#include <asm/stacktrace.h>
#include <asm/unwind.h>

#define FRAME_HEADER_SIZE (sizeof(long) * 2)

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;

	return state->regs ? &state->regs->ip : state->bp + 1;
}

static void unwind_dump(struct unwind_state *state)
{
	static bool dumped_before = false;
	bool prev_zero, zero = false;
	unsigned long word, *sp;
	struct stack_info stack_info = {0};
	unsigned long visit_mask = 0;

	if (dumped_before)
		return;

	dumped_before = true;

	printk_deferred("unwind stack type:%d next_sp:%p mask:0x%lx graph_idx:%d\n",
			state->stack_info.type, state->stack_info.next_sp,
			state->stack_mask, state->graph_idx);

	for (sp = PTR_ALIGN(state->orig_sp, sizeof(long)); sp;
	     sp = PTR_ALIGN(stack_info.next_sp, sizeof(long))) {
		if (get_stack_info(sp, state->task, &stack_info, &visit_mask))
			break;

		for (; sp < stack_info.end; sp++) {

			word = READ_ONCE_NOCHECK(*sp);

			prev_zero = zero;
			zero = word == 0;

			if (zero) {
				if (!prev_zero)
					printk_deferred("%p: %0*x ...\n",
							sp, BITS_PER_LONG/4, 0);
				continue;
			}

			printk_deferred("%p: %0*lx (%pB)\n",
					sp, BITS_PER_LONG/4, word, (void *)word);
		}
	}
}

static size_t regs_size(struct pt_regs *regs)
{
	/* x86_32 regs from kernel mode are two words shorter: */
	if (IS_ENABLED(CONFIG_X86_32) && !user_mode(regs))
		return sizeof(*regs) - 2*sizeof(long);

	return sizeof(*regs);
}

static bool in_entry_code(unsigned long ip)
{
	char *addr = (char *)ip;

	if (addr >= __entry_text_start && addr < __entry_text_end)
		return true;

	if (addr >= __irqentry_text_start && addr < __irqentry_text_end)
		return true;

	return false;
}

static inline unsigned long *last_frame(struct unwind_state *state)
{
	return (unsigned long *)task_pt_regs(state->task) - 2;
}

static bool is_last_frame(struct unwind_state *state)
{
	return state->bp == last_frame(state);
}

#ifdef CONFIG_X86_32
#define GCC_REALIGN_WORDS 3
#else
#define GCC_REALIGN_WORDS 1
#endif

static inline unsigned long *last_aligned_frame(struct unwind_state *state)
{
	return last_frame(state) - GCC_REALIGN_WORDS;
}

static bool is_last_aligned_frame(struct unwind_state *state)
{
	unsigned long *last_bp = last_frame(state);
	unsigned long *aligned_bp = last_aligned_frame(state);

	/*
	 * GCC can occasionally decide to realign the stack pointer and change
	 * the offset of the stack frame in the prologue of a function called
	 * by head/entry code.  Examples:
	 *
	 * <start_secondary>:
	 *      push   %edi
	 *      lea    0x8(%esp),%edi
	 *      and    $0xfffffff8,%esp
	 *      pushl  -0x4(%edi)
	 *      push   %ebp
	 *      mov    %esp,%ebp
	 *
	 * <x86_64_start_kernel>:
	 *      lea    0x8(%rsp),%r10
	 *      and    $0xfffffffffffffff0,%rsp
	 *      pushq  -0x8(%r10)
	 *      push   %rbp
	 *      mov    %rsp,%rbp
	 *
	 * After aligning the stack, it pushes a duplicate copy of the return
	 * address before pushing the frame pointer.
	 */
	return (state->bp == aligned_bp && *(aligned_bp + 1) == *(last_bp + 1));
}

static bool is_last_ftrace_frame(struct unwind_state *state)
{
	unsigned long *last_bp = last_frame(state);
	unsigned long *last_ftrace_bp = last_bp - 3;

	/*
	 * When unwinding from an ftrace handler of a function called by entry
	 * code, the stack layout of the last frame is:
	 *
	 *   bp
	 *   parent ret addr
	 *   bp
	 *   function ret addr
	 *   parent ret addr
	 *   pt_regs
	 *   -----------------
	 */
	return (state->bp == last_ftrace_bp &&
		*state->bp == *(state->bp + 2) &&
		*(state->bp + 1) == *(state->bp + 4));
}

static bool is_last_task_frame(struct unwind_state *state)
{
	return is_last_frame(state) || is_last_aligned_frame(state) ||
	       is_last_ftrace_frame(state);
}

/*
 * This determines if the frame pointer actually contains an encoded pointer to
 * pt_regs on the stack.  See ENCODE_FRAME_POINTER.
 */
#ifdef CONFIG_X86_64
static struct pt_regs *decode_frame_pointer(unsigned long *bp)
{
	unsigned long regs = (unsigned long)bp;

	if (!(regs & 0x1))
		return NULL;

	return (struct pt_regs *)(regs & ~0x1);
}
#else
static struct pt_regs *decode_frame_pointer(unsigned long *bp)
{
	unsigned long regs = (unsigned long)bp;

	if (regs & 0x80000000)
		return NULL;

	return (struct pt_regs *)(regs | 0x80000000);
}
#endif

#ifdef CONFIG_X86_32
#define KERNEL_REGS_SIZE (sizeof(struct pt_regs) - 2*sizeof(long))
#else
#define KERNEL_REGS_SIZE (sizeof(struct pt_regs))
#endif

static bool update_stack_state(struct unwind_state *state,
			       unsigned long *next_bp)
{
	struct stack_info *info = &state->stack_info;
	enum stack_type prev_type = info->type;
	struct pt_regs *regs;
	unsigned long *frame, *prev_frame_end, *addr_p, addr;
	size_t len;

	if (state->regs)
		prev_frame_end = (void *)state->regs + regs_size(state->regs);
	else
		prev_frame_end = (void *)state->bp + FRAME_HEADER_SIZE;

	/* Is the next frame pointer an encoded pointer to pt_regs? */
	regs = decode_frame_pointer(next_bp);
	if (regs) {
		frame = (unsigned long *)regs;
		len = KERNEL_REGS_SIZE;
		state->got_irq = true;
	} else {
		frame = next_bp;
		len = FRAME_HEADER_SIZE;
	}

	/*
	 * If the next bp 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 next bp
	 * could be on a subsequent stack.
	 */
	while (!on_stack(info, frame, len))
		if (get_stack_info(info->next_sp, state->task, info,
				   &state->stack_mask))
			return false;

	/* Make sure it only unwinds up and doesn't overlap the prev frame: */
	if (state->orig_sp && state->stack_info.type == prev_type &&
	    frame < prev_frame_end)
		return false;

	/*
	 * On 32-bit with user mode regs, make sure the last two regs are safe
	 * to access:
	 */
	if (IS_ENABLED(CONFIG_X86_32) && regs && user_mode(regs) &&
	    !on_stack(info, frame, len + 2*sizeof(long)))
		return false;

	/* Move state to the next frame: */
	if (regs) {
		state->regs = regs;
		state->bp = NULL;
	} else {
		state->bp = next_bp;
		state->regs = NULL;
	}

	/* Save the return address: */
	if (state->regs && user_mode(state->regs))
		state->ip = 0;
	else {
		addr_p = unwind_get_return_address_ptr(state);
		addr = READ_ONCE_TASK_STACK(state->task, *addr_p);
		state->ip = ftrace_graph_ret_addr(state->task, &state->graph_idx,
						  addr, addr_p);
	}

	/* Save the original stack pointer for unwind_dump(): */
	if (!state->orig_sp)
		state->orig_sp = frame;

	return true;
}

bool unwind_next_frame(struct unwind_state *state)
{
	struct pt_regs *regs;
	unsigned long *next_bp;

	if (unwind_done(state))
		return false;

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

	if (is_last_task_frame(state)) {
		regs = task_pt_regs(state->task);

		/*
		 * kthreads (other than the boot CPU's idle thread) have some
		 * partial regs at the end of their stack which were placed
		 * there by copy_thread_tls().  But the regs don't have any
		 * useful information, so we can skip them.
		 *
		 * This user_mode() check is slightly broader than a PF_KTHREAD
		 * check because it also catches the awkward situation where a
		 * newly forked kthread transitions into a user task by calling
		 * do_execve(), which eventually clears PF_KTHREAD.
		 */
		if (!user_mode(regs))
			goto the_end;

		/*
		 * We're almost at the end, but not quite: there's still the
		 * syscall regs frame.  Entry code doesn't encode the regs
		 * pointer for syscalls, so we have to set it manually.
		 */
		state->regs = regs;
		state->bp = NULL;
		state->ip = 0;
		return true;
	}

	/* Get the next frame pointer: */
	if (state->regs)
		next_bp = (unsigned long *)state->regs->bp;
	else
		next_bp = (unsigned long *)READ_ONCE_TASK_STACK(state->task, *state->bp);

	/* Move to the next frame if it's safe: */
	if (!update_stack_state(state, next_bp))
		goto bad_address;

	return true;

bad_address:
	state->error = true;

	/*
	 * When unwinding a non-current task, the task might actually be
	 * running on another CPU, in which case it could be modifying its
	 * stack while we're reading it.  This is generally not a problem and
	 * can be ignored as long as the caller understands that unwinding
	 * another task will not always succeed.
	 */
	if (state->task != current)
		goto the_end;

	/*
	 * Don't warn if the unwinder got lost due to an interrupt in entry
	 * code or in the C handler before the first frame pointer got set up:
	 */
	if (state->got_irq && in_entry_code(state->ip))
		goto the_end;
	if (state->regs &&
	    state->regs->sp >= (unsigned long)last_aligned_frame(state) &&
	    state->regs->sp < (unsigned long)task_pt_regs(state->task))
		goto the_end;

	/*
	 * There are some known frame pointer issues on 32-bit.  Disable
	 * unwinder warnings on 32-bit until it gets objtool support.
	 */
	if (IS_ENABLED(CONFIG_X86_32))
		goto the_end;

	if (state->regs) {
		printk_deferred_once(KERN_WARNING
			"WARNING: kernel stack regs at %p in %s:%d has bad 'bp' value %p\n",
			state->regs, state->task->comm,
			state->task->pid, next_bp);
		unwind_dump(state);
	} else {
		printk_deferred_once(KERN_WARNING
			"WARNING: kernel stack frame pointer at %p in %s:%d has bad value %p\n",
			state->bp, state->task->comm,
			state->task->pid, next_bp);
		unwind_dump(state);
	}
the_end:
	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)
{
	unsigned long *bp;

	memset(state, 0, sizeof(*state));
	state->task = task;
	state->got_irq = (regs);

	/* Don't even attempt to start from user mode regs: */
	if (regs && user_mode(regs)) {
		state->stack_info.type = STACK_TYPE_UNKNOWN;
		return;
	}

	bp = get_frame_pointer(task, regs);

	/* Initialize stack info and make sure the frame data is accessible: */
	get_stack_info(bp, state->task, &state->stack_info,
		       &state->stack_mask);
	update_stack_state(state, bp);

	/*
	 * 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.
	 */
	while (!unwind_done(state) &&
	       (!on_stack(&state->stack_info, first_frame, sizeof(long)) ||
			state->bp < first_frame))
		unwind_next_frame(state);
}
EXPORT_SYMBOL_GPL(__unwind_start);
Commit	Line	Data
7c7900f8	1	#include <linux/sched.h>
29930025	2	#include <linux/sched/task.h>
68db0cf1	3	#include <linux/sched/task_stack.h>
a8b7a923 JP	4	#include <linux/interrupt.h>
a8b7a923 JP	5	#include <asm/sections.h>
7c7900f8 JP	6	#include <asm/ptrace.h>
	7	#include <asm/bitops.h>
	8	#include <asm/stacktrace.h>
	9	#include <asm/unwind.h>
	10
	11	#define FRAME_HEADER_SIZE (sizeof(long) * 2)
	12
ee9f8fce JP	13	unsigned long unwind_get_return_address(struct unwind_state *state)
	14	{
	15	if (unwind_done(state))
	16	return 0;
	17
	18	return __kernel_text_address(state->ip) ? state->ip : 0;
	19	}
	20	EXPORT_SYMBOL_GPL(unwind_get_return_address);
	21
	22	unsigned long unwind_get_return_address_ptr(struct unwind_state state)
	23	{
	24	if (unwind_done(state))
	25	return NULL;
	26
	27	return state->regs ? &state->regs->ip : state->bp + 1;
	28	}
84936118	29
aa4f8534	30	static void unwind_dump(struct unwind_state *state)
8b5e99f0 JP	31	{
	32	static bool dumped_before = false;
	33	bool prev_zero, zero = false;
aa4f8534	34	unsigned long word, *sp;
262fa734 JP	35	struct stack_info stack_info = {0};
262fa734 JP	36	unsigned long visit_mask = 0;
8b5e99f0 JP	37
	38	if (dumped_before)
	39	return;
	40
	41	dumped_before = true;
	42
4ea3d741	43	printk_deferred("unwind stack type:%d next_sp:%p mask:0x%lx graph_idx:%d\n",
8b5e99f0 JP	44	state->stack_info.type, state->stack_info.next_sp,
	45	state->stack_mask, state->graph_idx);
	46
99bd28a4 JP	47	for (sp = PTR_ALIGN(state->orig_sp, sizeof(long)); sp;
99bd28a4 JP	48	sp = PTR_ALIGN(stack_info.next_sp, sizeof(long))) {
262fa734 JP	49	if (get_stack_info(sp, state->task, &stack_info, &visit_mask))
262fa734 JP	50	break;
8b5e99f0	51
262fa734	52	for (; sp < stack_info.end; sp++) {
8b5e99f0	53
262fa734 JP	54	word = READ_ONCE_NOCHECK(*sp);
	55
	56	prev_zero = zero;
	57	zero = word == 0;
8b5e99f0	58
262fa734 JP	59	if (zero) {
	60	if (!prev_zero)
	61	printk_deferred("%p: %0*x ...\n",
	62	sp, BITS_PER_LONG/4, 0);
	63	continue;
	64	}
	65
	66	printk_deferred("%p: %0*lx (%pB)\n",
	67	sp, BITS_PER_LONG/4, word, (void *)word);
	68	}
8b5e99f0 JP	69	}
	70	}
	71
24d86f59 JP	72	static size_t regs_size(struct pt_regs *regs)
	73	{
	74	/* x86_32 regs from kernel mode are two words shorter: */
	75	if (IS_ENABLED(CONFIG_X86_32) && !user_mode(regs))
	76	return sizeof(regs) - 2sizeof(long);
	77
	78	return sizeof(*regs);
	79	}
	80
a8b7a923 JP	81	static bool in_entry_code(unsigned long ip)
	82	{
	83	char addr = (char )ip;
	84
	85	if (addr >= __entry_text_start && addr < __entry_text_end)
	86	return true;
	87
a8b7a923 JP	88	if (addr >= __irqentry_text_start && addr < __irqentry_text_end)
a8b7a923 JP	89	return true;
a8b7a923 JP	90
	91	return false;
	92	}
	93
b0d50c7b JP	94	static inline unsigned long last_frame(struct unwind_state state)
	95	{
	96	return (unsigned long *)task_pt_regs(state->task) - 2;
	97	}
	98
519fb5c3 JP	99	static bool is_last_frame(struct unwind_state *state)
	100	{
	101	return state->bp == last_frame(state);
	102	}
	103
87a6b297 JP	104	#ifdef CONFIG_X86_32
	105	#define GCC_REALIGN_WORDS 3
	106	#else
	107	#define GCC_REALIGN_WORDS 1
	108	#endif
	109
b0d50c7b JP	110	static inline unsigned long last_aligned_frame(struct unwind_state state)
	111	{
	112	return last_frame(state) - GCC_REALIGN_WORDS;
	113	}
	114
519fb5c3	115	static bool is_last_aligned_frame(struct unwind_state *state)
acb4608a	116	{
b0d50c7b JP	117	unsigned long *last_bp = last_frame(state);
b0d50c7b JP	118	unsigned long *aligned_bp = last_aligned_frame(state);
acb4608a	119
8023e0e2	120	/*
519fb5c3 JP	121	* GCC can occasionally decide to realign the stack pointer and change
	122	* the offset of the stack frame in the prologue of a function called
	123	* by head/entry code. Examples:
87a6b297 JP	124	*
	125	* <start_secondary>:
	126	* push %edi
	127	* lea 0x8(%esp),%edi
	128	* and $0xfffffff8,%esp
	129	* pushl -0x4(%edi)
	130	* push %ebp
	131	* mov %esp,%ebp
	132	*
	133	* <x86_64_start_kernel>:
	134	* lea 0x8(%rsp),%r10
	135	* and $0xfffffffffffffff0,%rsp
	136	* pushq -0x8(%r10)
	137	* push %rbp
	138	* mov %rsp,%rbp
	139	*
519fb5c3 JP	140	* After aligning the stack, it pushes a duplicate copy of the return
	141	* address before pushing the frame pointer.
	142	*/
	143	return (state->bp == aligned_bp && (aligned_bp + 1) == (last_bp + 1));
	144	}
	145
	146	static bool is_last_ftrace_frame(struct unwind_state *state)
	147	{
	148	unsigned long *last_bp = last_frame(state);
	149	unsigned long *last_ftrace_bp = last_bp - 3;
	150
	151	/*
	152	* When unwinding from an ftrace handler of a function called by entry
	153	* code, the stack layout of the last frame is:
	154	*
	155	* bp
	156	* parent ret addr
	157	* bp
	158	* function ret addr
	159	* parent ret addr
	160	* pt_regs
	161	* -----------------
8023e0e2	162	*/
519fb5c3 JP	163	return (state->bp == last_ftrace_bp &&
	164	state->bp == (state->bp + 2) &&
	165	(state->bp + 1) == (state->bp + 4));
	166	}
	167
	168	static bool is_last_task_frame(struct unwind_state *state)
	169	{
	170	return is_last_frame(state) \|\| is_last_aligned_frame(state) \|\|
	171	is_last_ftrace_frame(state);
acb4608a JP	172	}
acb4608a JP	173
946c1911 JP	174	/*
	175	* This determines if the frame pointer actually contains an encoded pointer to
	176	* pt_regs on the stack. See ENCODE_FRAME_POINTER.
	177	*/
5c99b692	178	#ifdef CONFIG_X86_64
946c1911 JP	179	static struct pt_regs decode_frame_pointer(unsigned long bp)
	180	{
	181	unsigned long regs = (unsigned long)bp;
	182
	183	if (!(regs & 0x1))
	184	return NULL;
	185
	186	return (struct pt_regs *)(regs & ~0x1);
	187	}
5c99b692 JP	188	#else
	189	static struct pt_regs decode_frame_pointer(unsigned long bp)
	190	{
	191	unsigned long regs = (unsigned long)bp;
	192
	193	if (regs & 0x80000000)
	194	return NULL;
	195
	196	return (struct pt_regs *)(regs \| 0x80000000);
	197	}
	198	#endif
946c1911	199
62dd86ac JP	200	#ifdef CONFIG_X86_32
	201	#define KERNEL_REGS_SIZE (sizeof(struct pt_regs) - 2*sizeof(long))
	202	#else
	203	#define KERNEL_REGS_SIZE (sizeof(struct pt_regs))
	204	#endif
	205
5ed8d8bb JP	206	static bool update_stack_state(struct unwind_state *state,
5ed8d8bb JP	207	unsigned long *next_bp)
7c7900f8 JP	208	{
7c7900f8 JP	209	struct stack_info *info = &state->stack_info;
5ed8d8bb JP	210	enum stack_type prev_type = info->type;
5ed8d8bb JP	211	struct pt_regs *regs;
6bcdf9d5	212	unsigned long frame, prev_frame_end, *addr_p, addr;
5ed8d8bb JP	213	size_t len;
	214
	215	if (state->regs)
	216	prev_frame_end = (void *)state->regs + regs_size(state->regs);
	217	else
	218	prev_frame_end = (void *)state->bp + FRAME_HEADER_SIZE;
	219
	220	/* Is the next frame pointer an encoded pointer to pt_regs? */
	221	regs = decode_frame_pointer(next_bp);
	222	if (regs) {
	223	frame = (unsigned long *)regs;
62dd86ac	224	len = KERNEL_REGS_SIZE;
a8b7a923	225	state->got_irq = true;
5ed8d8bb JP	226	} else {
	227	frame = next_bp;
	228	len = FRAME_HEADER_SIZE;
	229	}
7c7900f8 JP	230
7c7900f8 JP	231	/*
5ed8d8bb	232	* If the next bp isn't on the current stack, switch to the next one.
7c7900f8 JP	233	*
7c7900f8 JP	234	* We may have to traverse multiple stacks to deal with the possibility
5ed8d8bb JP	235	* that info->next_sp could point to an empty stack and the next bp
5ed8d8bb JP	236	* could be on a subsequent stack.
7c7900f8	237	*/
5ed8d8bb	238	while (!on_stack(info, frame, len))
7c7900f8 JP	239	if (get_stack_info(info->next_sp, state->task, info,
	240	&state->stack_mask))
	241	return false;
	242
5ed8d8bb JP	243	/* Make sure it only unwinds up and doesn't overlap the prev frame: */
	244	if (state->orig_sp && state->stack_info.type == prev_type &&
	245	frame < prev_frame_end)
	246	return false;
	247
62dd86ac JP	248	/*
	249	* On 32-bit with user mode regs, make sure the last two regs are safe
	250	* to access:
	251	*/
	252	if (IS_ENABLED(CONFIG_X86_32) && regs && user_mode(regs) &&
	253	!on_stack(info, frame, len + 2*sizeof(long)))
	254	return false;
	255
5ed8d8bb JP	256	/* Move state to the next frame: */
	257	if (regs) {
	258	state->regs = regs;
	259	state->bp = NULL;
	260	} else {
	261	state->bp = next_bp;
	262	state->regs = NULL;
	263	}
	264
6bcdf9d5 JP	265	/* Save the return address: */
	266	if (state->regs && user_mode(state->regs))
	267	state->ip = 0;
	268	else {
	269	addr_p = unwind_get_return_address_ptr(state);
	270	addr = READ_ONCE_TASK_STACK(state->task, *addr_p);
	271	state->ip = ftrace_graph_ret_addr(state->task, &state->graph_idx,
	272	addr, addr_p);
	273	}
	274
5ed8d8bb	275	/* Save the original stack pointer for unwind_dump(): */
262fa734	276	if (!state->orig_sp)
5ed8d8bb	277	state->orig_sp = frame;
8b5e99f0	278
7c7900f8 JP	279	return true;
	280	}
	281
	282	bool unwind_next_frame(struct unwind_state *state)
	283	{
946c1911	284	struct pt_regs *regs;
5ed8d8bb	285	unsigned long *next_bp;
7c7900f8 JP	286
	287	if (unwind_done(state))
	288	return false;
	289
5ed8d8bb	290	/* Have we reached the end? */
946c1911 JP	291	if (state->regs && user_mode(state->regs))
	292	goto the_end;
	293
acb4608a JP	294	if (is_last_task_frame(state)) {
	295	regs = task_pt_regs(state->task);
	296
	297	/*
	298	* kthreads (other than the boot CPU's idle thread) have some
	299	* partial regs at the end of their stack which were placed
	300	* there by copy_thread_tls(). But the regs don't have any
	301	* useful information, so we can skip them.
	302	*
	303	* This user_mode() check is slightly broader than a PF_KTHREAD
	304	* check because it also catches the awkward situation where a
	305	* newly forked kthread transitions into a user task by calling
	306	* do_execve(), which eventually clears PF_KTHREAD.
	307	*/
	308	if (!user_mode(regs))
	309	goto the_end;
	310
	311	/*
	312	* We're almost at the end, but not quite: there's still the
	313	* syscall regs frame. Entry code doesn't encode the regs
	314	* pointer for syscalls, so we have to set it manually.
	315	*/
	316	state->regs = regs;
	317	state->bp = NULL;
6bcdf9d5	318	state->ip = 0;
acb4608a JP	319	return true;
	320	}
	321
5ed8d8bb	322	/* Get the next frame pointer: */
946c1911 JP	323	if (state->regs)
	324	next_bp = (unsigned long *)state->regs->bp;
	325	else
5ed8d8bb	326	next_bp = (unsigned long )READ_ONCE_TASK_STACK(state->task, state->bp);
946c1911	327
5ed8d8bb	328	/* Move to the next frame if it's safe: */
a8b7a923	329	if (!update_stack_state(state, next_bp))
c32c47c6	330	goto bad_address;
c32c47c6	331
7c7900f8	332	return true;
946c1911	333
c32c47c6	334	bad_address:
af085d90 JP	335	state->error = true;
af085d90 JP	336
900742d8 JP	337	/*
	338	* When unwinding a non-current task, the task might actually be
	339	* running on another CPU, in which case it could be modifying its
	340	* stack while we're reading it. This is generally not a problem and
	341	* can be ignored as long as the caller understands that unwinding
	342	* another task will not always succeed.
	343	*/
	344	if (state->task != current)
	345	goto the_end;
	346
a8b7a923 JP	347	/*
a8b7a923 JP	348	* Don't warn if the unwinder got lost due to an interrupt in entry
b0d50c7b	349	* code or in the C handler before the first frame pointer got set up:
a8b7a923 JP	350	*/
	351	if (state->got_irq && in_entry_code(state->ip))
	352	goto the_end;
b0d50c7b JP	353	if (state->regs &&
	354	state->regs->sp >= (unsigned long)last_aligned_frame(state) &&
	355	state->regs->sp < (unsigned long)task_pt_regs(state->task))
	356	goto the_end;
a8b7a923	357
d4a2d031 JP	358	/*
	359	* There are some known frame pointer issues on 32-bit. Disable
	360	* unwinder warnings on 32-bit until it gets objtool support.
	361	*/
	362	if (IS_ENABLED(CONFIG_X86_32))
	363	goto the_end;
	364
24d86f59 JP	365	if (state->regs) {
	366	printk_deferred_once(KERN_WARNING
	367	"WARNING: kernel stack regs at %p in %s:%d has bad 'bp' value %p\n",
	368	state->regs, state->task->comm,
5ed8d8bb	369	state->task->pid, next_bp);
aa4f8534	370	unwind_dump(state);
24d86f59 JP	371	} else {
	372	printk_deferred_once(KERN_WARNING
	373	"WARNING: kernel stack frame pointer at %p in %s:%d has bad value %p\n",
	374	state->bp, state->task->comm,
5ed8d8bb	375	state->task->pid, next_bp);
aa4f8534	376	unwind_dump(state);
24d86f59	377	}
946c1911 JP	378	the_end:
	379	state->stack_info.type = STACK_TYPE_UNKNOWN;
	380	return false;
7c7900f8 JP	381	}
	382	EXPORT_SYMBOL_GPL(unwind_next_frame);
	383
	384	void __unwind_start(struct unwind_state state, struct task_struct task,
	385	struct pt_regs regs, unsigned long first_frame)
	386	{
5ed8d8bb	387	unsigned long *bp;
946c1911	388
7c7900f8 JP	389	memset(state, 0, sizeof(*state));
7c7900f8 JP	390	state->task = task;
a8b7a923	391	state->got_irq = (regs);
7c7900f8	392
5ed8d8bb	393	/* Don't even attempt to start from user mode regs: */
7c7900f8 JP	394	if (regs && user_mode(regs)) {
	395	state->stack_info.type = STACK_TYPE_UNKNOWN;
	396	return;
	397	}
	398
946c1911	399	bp = get_frame_pointer(task, regs);
7c7900f8	400
5ed8d8bb JP	401	/* Initialize stack info and make sure the frame data is accessible: */
5ed8d8bb JP	402	get_stack_info(bp, state->task, &state->stack_info,
7c7900f8	403	&state->stack_mask);
5ed8d8bb	404	update_stack_state(state, bp);
7c7900f8 JP	405
	406	/*
	407	* The caller can provide the address of the first frame directly
	408	* (first_frame) or indirectly (regs->sp) to indicate which stack frame
	409	* to start unwinding at. Skip ahead until we reach it.
	410	*/
	411	while (!unwind_done(state) &&
	412	(!on_stack(&state->stack_info, first_frame, sizeof(long)) \|\|
	413	state->bp < first_frame))
	414	unwind_next_frame(state);
	415	}
	416	EXPORT_SYMBOL_GPL(__unwind_start);