[thirdparty/linux.git] / arch / x86 / kernel / unwind_frame.c

// SPDX-License-Identifier: GPL-2.0-only
#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 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

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 + sizeof(*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 = sizeof(*regs);
		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;

	/* 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->next_bp) {
		next_bp = state->next_bp;
		state->next_bp = NULL;
	} else 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->task != current)
		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);

	/*
	 * If we crash with IP==0, the last successfully executed instruction
	 * was probably an indirect function call with a NULL function pointer.
	 * That means that SP points into the middle of an incomplete frame:
	 * *SP is a return pointer, and *(SP-sizeof(unsigned long)) is where we
	 * would have written a frame pointer if we hadn't crashed.
	 * Pretend that the frame is complete and that BP points to it, but save
	 * the real BP so that we can use it when looking for the next frame.
	 */
	if (regs && regs->ip == 0 && (unsigned long *)regs->sp >= first_frame) {
		state->next_bp = bp;
		bp = ((unsigned long *)regs->sp) - 1;
	}

	/* 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->next_bp == NULL && state->bp < first_frame)))
		unwind_next_frame(state);
}
EXPORT_SYMBOL_GPL(__unwind_start);
Commit	Line	Data
457c8996	1	// SPDX-License-Identifier: GPL-2.0-only
7c7900f8	2	#include <linux/sched.h>
29930025	3	#include <linux/sched/task.h>
68db0cf1	4	#include <linux/sched/task_stack.h>
a8b7a923 JP	5	#include <linux/interrupt.h>
a8b7a923 JP	6	#include <asm/sections.h>
7c7900f8 JP	7	#include <asm/ptrace.h>
	8	#include <asm/bitops.h>
	9	#include <asm/stacktrace.h>
	10	#include <asm/unwind.h>
	11
	12	#define FRAME_HEADER_SIZE (sizeof(long) * 2)
	13
ee9f8fce JP	14	unsigned long unwind_get_return_address(struct unwind_state *state)
	15	{
	16	if (unwind_done(state))
	17	return 0;
	18
	19	return __kernel_text_address(state->ip) ? state->ip : 0;
	20	}
	21	EXPORT_SYMBOL_GPL(unwind_get_return_address);
	22
	23	unsigned long unwind_get_return_address_ptr(struct unwind_state state)
	24	{
	25	if (unwind_done(state))
	26	return NULL;
	27
	28	return state->regs ? &state->regs->ip : state->bp + 1;
	29	}
84936118	30
aa4f8534	31	static void unwind_dump(struct unwind_state *state)
8b5e99f0 JP	32	{
	33	static bool dumped_before = false;
	34	bool prev_zero, zero = false;
aa4f8534	35	unsigned long word, *sp;
262fa734 JP	36	struct stack_info stack_info = {0};
262fa734 JP	37	unsigned long visit_mask = 0;
8b5e99f0 JP	38
	39	if (dumped_before)
	40	return;
	41
	42	dumped_before = true;
	43
4ea3d741	44	printk_deferred("unwind stack type:%d next_sp:%p mask:0x%lx graph_idx:%d\n",
8b5e99f0 JP	45	state->stack_info.type, state->stack_info.next_sp,
	46	state->stack_mask, state->graph_idx);
	47
99bd28a4 JP	48	for (sp = PTR_ALIGN(state->orig_sp, sizeof(long)); sp;
99bd28a4 JP	49	sp = PTR_ALIGN(stack_info.next_sp, sizeof(long))) {
262fa734 JP	50	if (get_stack_info(sp, state->task, &stack_info, &visit_mask))
262fa734 JP	51	break;
8b5e99f0	52
262fa734	53	for (; sp < stack_info.end; sp++) {
8b5e99f0	54
262fa734 JP	55	word = READ_ONCE_NOCHECK(*sp);
	56
	57	prev_zero = zero;
	58	zero = word == 0;
8b5e99f0	59
262fa734 JP	60	if (zero) {
	61	if (!prev_zero)
	62	printk_deferred("%p: %0*x ...\n",
	63	sp, BITS_PER_LONG/4, 0);
	64	continue;
	65	}
	66
	67	printk_deferred("%p: %0*lx (%pB)\n",
	68	sp, BITS_PER_LONG/4, word, (void *)word);
	69	}
8b5e99f0 JP	70	}
	71	}
	72
a8b7a923 JP	73	static bool in_entry_code(unsigned long ip)
	74	{
	75	char addr = (char )ip;
	76
	77	if (addr >= __entry_text_start && addr < __entry_text_end)
	78	return true;
	79
a8b7a923 JP	80	if (addr >= __irqentry_text_start && addr < __irqentry_text_end)
a8b7a923 JP	81	return true;
a8b7a923 JP	82
	83	return false;
	84	}
	85
b0d50c7b JP	86	static inline unsigned long last_frame(struct unwind_state state)
	87	{
	88	return (unsigned long *)task_pt_regs(state->task) - 2;
	89	}
	90
519fb5c3 JP	91	static bool is_last_frame(struct unwind_state *state)
	92	{
	93	return state->bp == last_frame(state);
	94	}
	95
87a6b297 JP	96	#ifdef CONFIG_X86_32
	97	#define GCC_REALIGN_WORDS 3
	98	#else
	99	#define GCC_REALIGN_WORDS 1
	100	#endif
	101
b0d50c7b JP	102	static inline unsigned long last_aligned_frame(struct unwind_state state)
	103	{
	104	return last_frame(state) - GCC_REALIGN_WORDS;
	105	}
	106
519fb5c3	107	static bool is_last_aligned_frame(struct unwind_state *state)
acb4608a	108	{
b0d50c7b JP	109	unsigned long *last_bp = last_frame(state);
b0d50c7b JP	110	unsigned long *aligned_bp = last_aligned_frame(state);
acb4608a	111
8023e0e2	112	/*
519fb5c3 JP	113	* GCC can occasionally decide to realign the stack pointer and change
	114	* the offset of the stack frame in the prologue of a function called
	115	* by head/entry code. Examples:
87a6b297 JP	116	*
	117	* <start_secondary>:
	118	* push %edi
	119	* lea 0x8(%esp),%edi
	120	* and $0xfffffff8,%esp
	121	* pushl -0x4(%edi)
	122	* push %ebp
	123	* mov %esp,%ebp
	124	*
	125	* <x86_64_start_kernel>:
	126	* lea 0x8(%rsp),%r10
	127	* and $0xfffffffffffffff0,%rsp
	128	* pushq -0x8(%r10)
	129	* push %rbp
	130	* mov %rsp,%rbp
	131	*
519fb5c3 JP	132	* After aligning the stack, it pushes a duplicate copy of the return
	133	* address before pushing the frame pointer.
	134	*/
	135	return (state->bp == aligned_bp && (aligned_bp + 1) == (last_bp + 1));
	136	}
	137
	138	static bool is_last_ftrace_frame(struct unwind_state *state)
	139	{
	140	unsigned long *last_bp = last_frame(state);
	141	unsigned long *last_ftrace_bp = last_bp - 3;
	142
	143	/*
	144	* When unwinding from an ftrace handler of a function called by entry
	145	* code, the stack layout of the last frame is:
	146	*
	147	* bp
	148	* parent ret addr
	149	* bp
	150	* function ret addr
	151	* parent ret addr
	152	* pt_regs
	153	* -----------------
8023e0e2	154	*/
519fb5c3 JP	155	return (state->bp == last_ftrace_bp &&
	156	state->bp == (state->bp + 2) &&
	157	(state->bp + 1) == (state->bp + 4));
	158	}
	159
	160	static bool is_last_task_frame(struct unwind_state *state)
	161	{
	162	return is_last_frame(state) \|\| is_last_aligned_frame(state) \|\|
	163	is_last_ftrace_frame(state);
acb4608a JP	164	}
acb4608a JP	165
946c1911 JP	166	/*
	167	* This determines if the frame pointer actually contains an encoded pointer to
	168	* pt_regs on the stack. See ENCODE_FRAME_POINTER.
	169	*/
5c99b692	170	#ifdef CONFIG_X86_64
946c1911 JP	171	static struct pt_regs decode_frame_pointer(unsigned long bp)
	172	{
	173	unsigned long regs = (unsigned long)bp;
	174
	175	if (!(regs & 0x1))
	176	return NULL;
	177
	178	return (struct pt_regs *)(regs & ~0x1);
	179	}
5c99b692 JP	180	#else
	181	static struct pt_regs decode_frame_pointer(unsigned long bp)
	182	{
	183	unsigned long regs = (unsigned long)bp;
	184
	185	if (regs & 0x80000000)
	186	return NULL;
	187
	188	return (struct pt_regs *)(regs \| 0x80000000);
	189	}
	190	#endif
946c1911	191
5ed8d8bb JP	192	static bool update_stack_state(struct unwind_state *state,
5ed8d8bb JP	193	unsigned long *next_bp)
7c7900f8 JP	194	{
7c7900f8 JP	195	struct stack_info *info = &state->stack_info;
5ed8d8bb JP	196	enum stack_type prev_type = info->type;
5ed8d8bb JP	197	struct pt_regs *regs;
6bcdf9d5	198	unsigned long frame, prev_frame_end, *addr_p, addr;
5ed8d8bb JP	199	size_t len;
	200
	201	if (state->regs)
3c88c692	202	prev_frame_end = (void )state->regs + sizeof(state->regs);
5ed8d8bb JP	203	else
	204	prev_frame_end = (void *)state->bp + FRAME_HEADER_SIZE;
	205
	206	/* Is the next frame pointer an encoded pointer to pt_regs? */
	207	regs = decode_frame_pointer(next_bp);
	208	if (regs) {
	209	frame = (unsigned long *)regs;
3c88c692	210	len = sizeof(*regs);
a8b7a923	211	state->got_irq = true;
5ed8d8bb JP	212	} else {
	213	frame = next_bp;
	214	len = FRAME_HEADER_SIZE;
	215	}
7c7900f8 JP	216
7c7900f8 JP	217	/*
5ed8d8bb	218	* If the next bp isn't on the current stack, switch to the next one.
7c7900f8 JP	219	*
7c7900f8 JP	220	* We may have to traverse multiple stacks to deal with the possibility
5ed8d8bb JP	221	* that info->next_sp could point to an empty stack and the next bp
5ed8d8bb JP	222	* could be on a subsequent stack.
7c7900f8	223	*/
5ed8d8bb	224	while (!on_stack(info, frame, len))
7c7900f8 JP	225	if (get_stack_info(info->next_sp, state->task, info,
	226	&state->stack_mask))
	227	return false;
	228
5ed8d8bb JP	229	/* Make sure it only unwinds up and doesn't overlap the prev frame: */
	230	if (state->orig_sp && state->stack_info.type == prev_type &&
	231	frame < prev_frame_end)
	232	return false;
	233
	234	/* Move state to the next frame: */
	235	if (regs) {
	236	state->regs = regs;
	237	state->bp = NULL;
	238	} else {
	239	state->bp = next_bp;
	240	state->regs = NULL;
	241	}
	242
6bcdf9d5 JP	243	/* Save the return address: */
	244	if (state->regs && user_mode(state->regs))
	245	state->ip = 0;
	246	else {
	247	addr_p = unwind_get_return_address_ptr(state);
	248	addr = READ_ONCE_TASK_STACK(state->task, *addr_p);
	249	state->ip = ftrace_graph_ret_addr(state->task, &state->graph_idx,
	250	addr, addr_p);
	251	}
	252
5ed8d8bb	253	/* Save the original stack pointer for unwind_dump(): */
262fa734	254	if (!state->orig_sp)
5ed8d8bb	255	state->orig_sp = frame;
8b5e99f0	256
7c7900f8 JP	257	return true;
	258	}
	259
	260	bool unwind_next_frame(struct unwind_state *state)
	261	{
946c1911	262	struct pt_regs *regs;
5ed8d8bb	263	unsigned long *next_bp;
7c7900f8 JP	264
	265	if (unwind_done(state))
	266	return false;
	267
5ed8d8bb	268	/* Have we reached the end? */
946c1911 JP	269	if (state->regs && user_mode(state->regs))
	270	goto the_end;
	271
acb4608a JP	272	if (is_last_task_frame(state)) {
	273	regs = task_pt_regs(state->task);
	274
	275	/*
	276	* kthreads (other than the boot CPU's idle thread) have some
	277	* partial regs at the end of their stack which were placed
	278	* there by copy_thread_tls(). But the regs don't have any
	279	* useful information, so we can skip them.
	280	*
	281	* This user_mode() check is slightly broader than a PF_KTHREAD
	282	* check because it also catches the awkward situation where a
	283	* newly forked kthread transitions into a user task by calling
	284	* do_execve(), which eventually clears PF_KTHREAD.
	285	*/
	286	if (!user_mode(regs))
	287	goto the_end;
	288
	289	/*
	290	* We're almost at the end, but not quite: there's still the
	291	* syscall regs frame. Entry code doesn't encode the regs
	292	* pointer for syscalls, so we have to set it manually.
	293	*/
	294	state->regs = regs;
	295	state->bp = NULL;
6bcdf9d5	296	state->ip = 0;
acb4608a JP	297	return true;
	298	}
	299
5ed8d8bb	300	/* Get the next frame pointer: */
f4f34e1b JH	301	if (state->next_bp) {
	302	next_bp = state->next_bp;
	303	state->next_bp = NULL;
	304	} else if (state->regs) {
946c1911	305	next_bp = (unsigned long *)state->regs->bp;
f4f34e1b	306	} else {
5ed8d8bb	307	next_bp = (unsigned long )READ_ONCE_TASK_STACK(state->task, state->bp);
f4f34e1b	308	}
946c1911	309
5ed8d8bb	310	/* Move to the next frame if it's safe: */
a8b7a923	311	if (!update_stack_state(state, next_bp))
c32c47c6	312	goto bad_address;
c32c47c6	313
7c7900f8	314	return true;
946c1911	315
c32c47c6	316	bad_address:
af085d90 JP	317	state->error = true;
af085d90 JP	318
900742d8 JP	319	/*
	320	* When unwinding a non-current task, the task might actually be
	321	* running on another CPU, in which case it could be modifying its
	322	* stack while we're reading it. This is generally not a problem and
	323	* can be ignored as long as the caller understands that unwinding
	324	* another task will not always succeed.
	325	*/
	326	if (state->task != current)
	327	goto the_end;
	328
a8b7a923 JP	329	/*
a8b7a923 JP	330	* Don't warn if the unwinder got lost due to an interrupt in entry
b0d50c7b	331	* code or in the C handler before the first frame pointer got set up:
a8b7a923 JP	332	*/
	333	if (state->got_irq && in_entry_code(state->ip))
	334	goto the_end;
b0d50c7b JP	335	if (state->regs &&
	336	state->regs->sp >= (unsigned long)last_aligned_frame(state) &&
	337	state->regs->sp < (unsigned long)task_pt_regs(state->task))
	338	goto the_end;
a8b7a923	339
d4a2d031 JP	340	/*
	341	* There are some known frame pointer issues on 32-bit. Disable
	342	* unwinder warnings on 32-bit until it gets objtool support.
	343	*/
	344	if (IS_ENABLED(CONFIG_X86_32))
	345	goto the_end;
	346
b08418b5 JP	347	if (state->task != current)
	348	goto the_end;
	349
24d86f59 JP	350	if (state->regs) {
	351	printk_deferred_once(KERN_WARNING
	352	"WARNING: kernel stack regs at %p in %s:%d has bad 'bp' value %p\n",
	353	state->regs, state->task->comm,
5ed8d8bb	354	state->task->pid, next_bp);
aa4f8534	355	unwind_dump(state);
24d86f59 JP	356	} else {
	357	printk_deferred_once(KERN_WARNING
	358	"WARNING: kernel stack frame pointer at %p in %s:%d has bad value %p\n",
	359	state->bp, state->task->comm,
5ed8d8bb	360	state->task->pid, next_bp);
aa4f8534	361	unwind_dump(state);
24d86f59	362	}
946c1911 JP	363	the_end:
	364	state->stack_info.type = STACK_TYPE_UNKNOWN;
	365	return false;
7c7900f8 JP	366	}
	367	EXPORT_SYMBOL_GPL(unwind_next_frame);
	368
	369	void __unwind_start(struct unwind_state state, struct task_struct task,
	370	struct pt_regs regs, unsigned long first_frame)
	371	{
5ed8d8bb	372	unsigned long *bp;
946c1911	373
7c7900f8 JP	374	memset(state, 0, sizeof(*state));
7c7900f8 JP	375	state->task = task;
a8b7a923	376	state->got_irq = (regs);
7c7900f8	377
5ed8d8bb	378	/* Don't even attempt to start from user mode regs: */
7c7900f8 JP	379	if (regs && user_mode(regs)) {
	380	state->stack_info.type = STACK_TYPE_UNKNOWN;
	381	return;
	382	}
	383
946c1911	384	bp = get_frame_pointer(task, regs);
7c7900f8	385
f4f34e1b JH	386	/*
	387	* If we crash with IP==0, the last successfully executed instruction
	388	* was probably an indirect function call with a NULL function pointer.
	389	* That means that SP points into the middle of an incomplete frame:
	390	* SP is a return pointer, and (SP-sizeof(unsigned long)) is where we
	391	* would have written a frame pointer if we hadn't crashed.
	392	* Pretend that the frame is complete and that BP points to it, but save
	393	* the real BP so that we can use it when looking for the next frame.
	394	*/
3c88c692	395	if (regs && regs->ip == 0 && (unsigned long *)regs->sp >= first_frame) {
f4f34e1b	396	state->next_bp = bp;
3c88c692	397	bp = ((unsigned long *)regs->sp) - 1;
f4f34e1b JH	398	}
f4f34e1b JH	399
5ed8d8bb JP	400	/* Initialize stack info and make sure the frame data is accessible: */
5ed8d8bb JP	401	get_stack_info(bp, state->task, &state->stack_info,
7c7900f8	402	&state->stack_mask);
5ed8d8bb	403	update_stack_state(state, bp);
7c7900f8 JP	404
	405	/*
	406	* The caller can provide the address of the first frame directly
	407	* (first_frame) or indirectly (regs->sp) to indicate which stack frame
	408	* to start unwinding at. Skip ahead until we reach it.
	409	*/
	410	while (!unwind_done(state) &&
	411	(!on_stack(&state->stack_info, first_frame, sizeof(long)) \|\|
f4f34e1b	412	(state->next_bp == NULL && state->bp < first_frame)))
7c7900f8 JP	413	unwind_next_frame(state);
	414	}
	415	EXPORT_SYMBOL_GPL(__unwind_start);