1// SPDX-License-Identifier: GPL-2.0-only
  2#include <linux/sched.h>
  3#include <linux/sched/task.h>
  4#include <linux/sched/task_stack.h>
  5#include <linux/interrupt.h>
  6#include <asm/sections.h>
  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
 14unsigned 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}
 21EXPORT_SYMBOL_GPL(unwind_get_return_address);
 22
 23unsigned 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}
 30
 31static void unwind_dump(struct unwind_state *state)
 32{
 33	static bool dumped_before = false;
 34	bool prev_zero, zero = false;
 35	unsigned long word, *sp;
 36	struct stack_info stack_info = {0};
 37	unsigned long visit_mask = 0;
 38
 39	if (dumped_before)
 40		return;
 41
 42	dumped_before = true;
 43
 44	printk_deferred("unwind stack type:%d next_sp:%p mask:0x%lx graph_idx:%d\n",
 45			state->stack_info.type, state->stack_info.next_sp,
 46			state->stack_mask, state->graph_idx);
 47
 48	for (sp = PTR_ALIGN(state->orig_sp, sizeof(long)); sp;
 49	     sp = PTR_ALIGN(stack_info.next_sp, sizeof(long))) {
 50		if (get_stack_info(sp, state->task, &stack_info, &visit_mask))
 51			break;
 52
 53		for (; sp < stack_info.end; sp++) {
 54
 55			word = READ_ONCE_NOCHECK(*sp);
 56
 57			prev_zero = zero;
 58			zero = word == 0;
 59
 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		}
 70	}
 71}
 72
 
 
 
 
 
 
 
 
 
 73static bool in_entry_code(unsigned long ip)
 74{
 75	char *addr = (char *)ip;
 76
 77	return addr >= __entry_text_start && addr < __entry_text_end;
 
 
 
 
 
 
 78}
 79
 80static inline unsigned long *last_frame(struct unwind_state *state)
 81{
 82	return (unsigned long *)task_pt_regs(state->task) - 2;
 83}
 84
 85static bool is_last_frame(struct unwind_state *state)
 86{
 87	return state->bp == last_frame(state);
 88}
 89
 90#ifdef CONFIG_X86_32
 91#define GCC_REALIGN_WORDS 3
 92#else
 93#define GCC_REALIGN_WORDS 1
 94#endif
 95
 96static inline unsigned long *last_aligned_frame(struct unwind_state *state)
 97{
 98	return last_frame(state) - GCC_REALIGN_WORDS;
 99}
100
101static bool is_last_aligned_frame(struct unwind_state *state)
102{
103	unsigned long *last_bp = last_frame(state);
104	unsigned long *aligned_bp = last_aligned_frame(state);
105
106	/*
107	 * GCC can occasionally decide to realign the stack pointer and change
108	 * the offset of the stack frame in the prologue of a function called
109	 * by head/entry code.  Examples:
110	 *
111	 * <start_secondary>:
112	 *      push   %edi
113	 *      lea    0x8(%esp),%edi
114	 *      and    $0xfffffff8,%esp
115	 *      pushl  -0x4(%edi)
116	 *      push   %ebp
117	 *      mov    %esp,%ebp
118	 *
119	 * <x86_64_start_kernel>:
120	 *      lea    0x8(%rsp),%r10
121	 *      and    $0xfffffffffffffff0,%rsp
122	 *      pushq  -0x8(%r10)
123	 *      push   %rbp
124	 *      mov    %rsp,%rbp
125	 *
126	 * After aligning the stack, it pushes a duplicate copy of the return
127	 * address before pushing the frame pointer.
128	 */
129	return (state->bp == aligned_bp && *(aligned_bp + 1) == *(last_bp + 1));
130}
131
132static bool is_last_ftrace_frame(struct unwind_state *state)
133{
134	unsigned long *last_bp = last_frame(state);
135	unsigned long *last_ftrace_bp = last_bp - 3;
136
137	/*
138	 * When unwinding from an ftrace handler of a function called by entry
139	 * code, the stack layout of the last frame is:
140	 *
141	 *   bp
142	 *   parent ret addr
143	 *   bp
144	 *   function ret addr
145	 *   parent ret addr
146	 *   pt_regs
147	 *   -----------------
148	 */
149	return (state->bp == last_ftrace_bp &&
150		*state->bp == *(state->bp + 2) &&
151		*(state->bp + 1) == *(state->bp + 4));
152}
153
154static bool is_last_task_frame(struct unwind_state *state)
155{
156	return is_last_frame(state) || is_last_aligned_frame(state) ||
157	       is_last_ftrace_frame(state);
158}
159
160/*
161 * This determines if the frame pointer actually contains an encoded pointer to
162 * pt_regs on the stack.  See ENCODE_FRAME_POINTER.
163 */
164#ifdef CONFIG_X86_64
165static struct pt_regs *decode_frame_pointer(unsigned long *bp)
166{
167	unsigned long regs = (unsigned long)bp;
168
169	if (!(regs & 0x1))
170		return NULL;
171
172	return (struct pt_regs *)(regs & ~0x1);
173}
174#else
175static struct pt_regs *decode_frame_pointer(unsigned long *bp)
176{
177	unsigned long regs = (unsigned long)bp;
178
179	if (regs & 0x80000000)
180		return NULL;
181
182	return (struct pt_regs *)(regs | 0x80000000);
183}
184#endif
185
186/*
187 * While walking the stack, KMSAN may stomp on stale locals from other
188 * functions that were marked as uninitialized upon function exit, and
189 * now hold the call frame information for the current function (e.g. the frame
190 * pointer). Because KMSAN does not specifically mark call frames as
191 * initialized, false positive reports are possible. To prevent such reports,
192 * we mark the functions scanning the stack (here and below) with
193 * __no_kmsan_checks.
194 */
195__no_kmsan_checks
196static bool update_stack_state(struct unwind_state *state,
197			       unsigned long *next_bp)
198{
199	struct stack_info *info = &state->stack_info;
200	enum stack_type prev_type = info->type;
201	struct pt_regs *regs;
202	unsigned long *frame, *prev_frame_end, *addr_p, addr;
203	size_t len;
204
205	if (state->regs)
206		prev_frame_end = (void *)state->regs + sizeof(*state->regs);
207	else
208		prev_frame_end = (void *)state->bp + FRAME_HEADER_SIZE;
209
210	/* Is the next frame pointer an encoded pointer to pt_regs? */
211	regs = decode_frame_pointer(next_bp);
212	if (regs) {
213		frame = (unsigned long *)regs;
214		len = sizeof(*regs);
215		state->got_irq = true;
216	} else {
217		frame = next_bp;
218		len = FRAME_HEADER_SIZE;
219	}
220
221	/*
222	 * If the next bp isn't on the current stack, switch to the next one.
223	 *
224	 * We may have to traverse multiple stacks to deal with the possibility
225	 * that info->next_sp could point to an empty stack and the next bp
226	 * could be on a subsequent stack.
227	 */
228	while (!on_stack(info, frame, len))
229		if (get_stack_info(info->next_sp, state->task, info,
230				   &state->stack_mask))
231			return false;
232
233	/* Make sure it only unwinds up and doesn't overlap the prev frame: */
234	if (state->orig_sp && state->stack_info.type == prev_type &&
235	    frame < prev_frame_end)
236		return false;
237
 
 
 
 
 
 
 
 
238	/* Move state to the next frame: */
239	if (regs) {
240		state->regs = regs;
241		state->bp = NULL;
242	} else {
243		state->bp = next_bp;
244		state->regs = NULL;
245	}
246
247	/* Save the return address: */
248	if (state->regs && user_mode(state->regs))
249		state->ip = 0;
250	else {
251		addr_p = unwind_get_return_address_ptr(state);
252		addr = READ_ONCE_TASK_STACK(state->task, *addr_p);
253		state->ip = unwind_recover_ret_addr(state, addr, addr_p);
 
254	}
255
256	/* Save the original stack pointer for unwind_dump(): */
257	if (!state->orig_sp)
258		state->orig_sp = frame;
259
260	return true;
261}
262
263__no_kmsan_checks
264bool unwind_next_frame(struct unwind_state *state)
265{
266	struct pt_regs *regs;
267	unsigned long *next_bp;
268
269	if (unwind_done(state))
270		return false;
271
272	/* Have we reached the end? */
273	if (state->regs && user_mode(state->regs))
274		goto the_end;
275
276	if (is_last_task_frame(state)) {
277		regs = task_pt_regs(state->task);
278
279		/*
280		 * kthreads (other than the boot CPU's idle thread) have some
281		 * partial regs at the end of their stack which were placed
282		 * there by copy_thread().  But the regs don't have any
283		 * useful information, so we can skip them.
284		 *
285		 * This user_mode() check is slightly broader than a PF_KTHREAD
286		 * check because it also catches the awkward situation where a
287		 * newly forked kthread transitions into a user task by calling
288		 * kernel_execve(), which eventually clears PF_KTHREAD.
289		 */
290		if (!user_mode(regs))
291			goto the_end;
292
293		/*
294		 * We're almost at the end, but not quite: there's still the
295		 * syscall regs frame.  Entry code doesn't encode the regs
296		 * pointer for syscalls, so we have to set it manually.
297		 */
298		state->regs = regs;
299		state->bp = NULL;
300		state->ip = 0;
301		return true;
302	}
303
304	/* Get the next frame pointer: */
305	if (state->next_bp) {
306		next_bp = state->next_bp;
307		state->next_bp = NULL;
308	} else if (state->regs) {
309		next_bp = (unsigned long *)state->regs->bp;
310	} else {
311		next_bp = (unsigned long *)READ_ONCE_TASK_STACK(state->task, *state->bp);
312	}
313
314	/* Move to the next frame if it's safe: */
315	if (!update_stack_state(state, next_bp))
316		goto bad_address;
317
318	return true;
319
320bad_address:
321	state->error = true;
322
323	/*
324	 * When unwinding a non-current task, the task might actually be
325	 * running on another CPU, in which case it could be modifying its
326	 * stack while we're reading it.  This is generally not a problem and
327	 * can be ignored as long as the caller understands that unwinding
328	 * another task will not always succeed.
329	 */
330	if (state->task != current)
331		goto the_end;
332
333	/*
334	 * Don't warn if the unwinder got lost due to an interrupt in entry
335	 * code or in the C handler before the first frame pointer got set up:
336	 */
337	if (state->got_irq && in_entry_code(state->ip))
338		goto the_end;
339	if (state->regs &&
340	    state->regs->sp >= (unsigned long)last_aligned_frame(state) &&
341	    state->regs->sp < (unsigned long)task_pt_regs(state->task))
342		goto the_end;
343
344	/*
345	 * There are some known frame pointer issues on 32-bit.  Disable
346	 * unwinder warnings on 32-bit until it gets objtool support.
347	 */
348	if (IS_ENABLED(CONFIG_X86_32))
349		goto the_end;
350
351	if (state->task != current)
352		goto the_end;
353
354	if (state->regs) {
355		printk_deferred_once(KERN_WARNING
356			"WARNING: kernel stack regs at %p in %s:%d has bad 'bp' value %p\n",
357			state->regs, state->task->comm,
358			state->task->pid, next_bp);
359		unwind_dump(state);
360	} else {
361		printk_deferred_once(KERN_WARNING
362			"WARNING: kernel stack frame pointer at %p in %s:%d has bad value %p\n",
363			state->bp, state->task->comm,
364			state->task->pid, next_bp);
365		unwind_dump(state);
366	}
367the_end:
368	state->stack_info.type = STACK_TYPE_UNKNOWN;
369	return false;
370}
371EXPORT_SYMBOL_GPL(unwind_next_frame);
372
373void __unwind_start(struct unwind_state *state, struct task_struct *task,
374		    struct pt_regs *regs, unsigned long *first_frame)
375{
376	unsigned long *bp;
377
378	memset(state, 0, sizeof(*state));
379	state->task = task;
380	state->got_irq = (regs);
381
382	/* Don't even attempt to start from user mode regs: */
383	if (regs && user_mode(regs)) {
384		state->stack_info.type = STACK_TYPE_UNKNOWN;
385		return;
386	}
387
388	bp = get_frame_pointer(task, regs);
389
390	/*
391	 * If we crash with IP==0, the last successfully executed instruction
392	 * was probably an indirect function call with a NULL function pointer.
393	 * That means that SP points into the middle of an incomplete frame:
394	 * *SP is a return pointer, and *(SP-sizeof(unsigned long)) is where we
395	 * would have written a frame pointer if we hadn't crashed.
396	 * Pretend that the frame is complete and that BP points to it, but save
397	 * the real BP so that we can use it when looking for the next frame.
398	 */
399	if (regs && regs->ip == 0 && (unsigned long *)regs->sp >= first_frame) {
400		state->next_bp = bp;
401		bp = ((unsigned long *)regs->sp) - 1;
402	}
403
404	/* Initialize stack info and make sure the frame data is accessible: */
405	get_stack_info(bp, state->task, &state->stack_info,
406		       &state->stack_mask);
407	update_stack_state(state, bp);
408
409	/*
410	 * The caller can provide the address of the first frame directly
411	 * (first_frame) or indirectly (regs->sp) to indicate which stack frame
412	 * to start unwinding at.  Skip ahead until we reach it.
413	 */
414	while (!unwind_done(state) &&
415	       (!on_stack(&state->stack_info, first_frame, sizeof(long)) ||
416			(state->next_bp == NULL && state->bp < first_frame)))
417		unwind_next_frame(state);
418}
419EXPORT_SYMBOL_GPL(__unwind_start);

 
  1#include <linux/sched.h>
  2#include <linux/sched/task.h>
  3#include <linux/sched/task_stack.h>
  4#include <linux/interrupt.h>
  5#include <asm/sections.h>
  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
 13unsigned 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}
 20EXPORT_SYMBOL_GPL(unwind_get_return_address);
 21
 22unsigned 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}
 29
 30static void unwind_dump(struct unwind_state *state)
 31{
 32	static bool dumped_before = false;
 33	bool prev_zero, zero = false;
 34	unsigned long word, *sp;
 35	struct stack_info stack_info = {0};
 36	unsigned long visit_mask = 0;
 37
 38	if (dumped_before)
 39		return;
 40
 41	dumped_before = true;
 42
 43	printk_deferred("unwind stack type:%d next_sp:%p mask:0x%lx graph_idx:%d\n",
 44			state->stack_info.type, state->stack_info.next_sp,
 45			state->stack_mask, state->graph_idx);
 46
 47	for (sp = PTR_ALIGN(state->orig_sp, sizeof(long)); sp;
 48	     sp = PTR_ALIGN(stack_info.next_sp, sizeof(long))) {
 49		if (get_stack_info(sp, state->task, &stack_info, &visit_mask))
 50			break;
 51
 52		for (; sp < stack_info.end; sp++) {
 53
 54			word = READ_ONCE_NOCHECK(*sp);
 55
 56			prev_zero = zero;
 57			zero = word == 0;
 58
 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		}
 69	}
 70}
 71
 72static 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) - 2*sizeof(long);
 77
 78	return sizeof(*regs);
 79}
 80
 81static 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
 88	if (addr >= __irqentry_text_start && addr < __irqentry_text_end)
 89		return true;
 90
 91	return false;
 92}
 93
 94static inline unsigned long *last_frame(struct unwind_state *state)
 95{
 96	return (unsigned long *)task_pt_regs(state->task) - 2;
 97}
 98
 99static bool is_last_frame(struct unwind_state *state)
100{
101	return state->bp == last_frame(state);
102}
103
104#ifdef CONFIG_X86_32
105#define GCC_REALIGN_WORDS 3
106#else
107#define GCC_REALIGN_WORDS 1
108#endif
109
110static inline unsigned long *last_aligned_frame(struct unwind_state *state)
111{
112	return last_frame(state) - GCC_REALIGN_WORDS;
113}
114
115static bool is_last_aligned_frame(struct unwind_state *state)
116{
117	unsigned long *last_bp = last_frame(state);
118	unsigned long *aligned_bp = last_aligned_frame(state);
119
120	/*
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:
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	 *
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
146static 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	 *   -----------------
162	 */
163	return (state->bp == last_ftrace_bp &&
164		*state->bp == *(state->bp + 2) &&
165		*(state->bp + 1) == *(state->bp + 4));
166}
167
168static 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);
172}
173
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 */
178#ifdef CONFIG_X86_64
179static 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}
188#else
189static 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
199
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
 
 
 
 
206static bool update_stack_state(struct unwind_state *state,
207			       unsigned long *next_bp)
208{
209	struct stack_info *info = &state->stack_info;
210	enum stack_type prev_type = info->type;
211	struct pt_regs *regs;
212	unsigned long *frame, *prev_frame_end, *addr_p, addr;
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;
224		len = KERNEL_REGS_SIZE;
225		state->got_irq = true;
226	} else {
227		frame = next_bp;
228		len = FRAME_HEADER_SIZE;
229	}
230
231	/*
232	 * If the next bp isn't on the current stack, switch to the next one.
233	 *
234	 * We may have to traverse multiple stacks to deal with the possibility
235	 * that info->next_sp could point to an empty stack and the next bp
236	 * could be on a subsequent stack.
237	 */
238	while (!on_stack(info, frame, len))
239		if (get_stack_info(info->next_sp, state->task, info,
240				   &state->stack_mask))
241			return false;
242
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
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
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
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
275	/* Save the original stack pointer for unwind_dump(): */
276	if (!state->orig_sp)
277		state->orig_sp = frame;
278
279	return true;
280}
281
 
282bool unwind_next_frame(struct unwind_state *state)
283{
284	struct pt_regs *regs;
285	unsigned long *next_bp;
286
287	if (unwind_done(state))
288		return false;
289
290	/* Have we reached the end? */
291	if (state->regs && user_mode(state->regs))
292		goto the_end;
293
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;
318		state->ip = 0;
319		return true;
320	}
321
322	/* Get the next frame pointer: */
323	if (state->regs)
 
 
 
324		next_bp = (unsigned long *)state->regs->bp;
325	else
326		next_bp = (unsigned long *)READ_ONCE_TASK_STACK(state->task, *state->bp);
 
327
328	/* Move to the next frame if it's safe: */
329	if (!update_stack_state(state, next_bp))
330		goto bad_address;
331
332	return true;
333
334bad_address:
335	state->error = true;
336
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
347	/*
348	 * Don't warn if the unwinder got lost due to an interrupt in entry
349	 * code or in the C handler before the first frame pointer got set up:
350	 */
351	if (state->got_irq && in_entry_code(state->ip))
352		goto the_end;
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;
357
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
 
 
 
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,
369			state->task->pid, next_bp);
370		unwind_dump(state);
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,
375			state->task->pid, next_bp);
376		unwind_dump(state);
377	}
378the_end:
379	state->stack_info.type = STACK_TYPE_UNKNOWN;
380	return false;
381}
382EXPORT_SYMBOL_GPL(unwind_next_frame);
383
384void __unwind_start(struct unwind_state *state, struct task_struct *task,
385		    struct pt_regs *regs, unsigned long *first_frame)
386{
387	unsigned long *bp;
388
389	memset(state, 0, sizeof(*state));
390	state->task = task;
391	state->got_irq = (regs);
392
393	/* Don't even attempt to start from user mode regs: */
394	if (regs && user_mode(regs)) {
395		state->stack_info.type = STACK_TYPE_UNKNOWN;
396		return;
397	}
398
399	bp = get_frame_pointer(task, regs);
400
 
 
 
 
 
 
 
 
 
 
 
 
 
 
401	/* Initialize stack info and make sure the frame data is accessible: */
402	get_stack_info(bp, state->task, &state->stack_info,
403		       &state->stack_mask);
404	update_stack_state(state, bp);
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}
416EXPORT_SYMBOL_GPL(__unwind_start);