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>
12 #define FRAME_HEADER_SIZE (sizeof(long) * 2)
14 unsigned long unwind_get_return_address(struct unwind_state
*state
)
16 if (unwind_done(state
))
19 return __kernel_text_address(state
->ip
) ? state
->ip
: 0;
21 EXPORT_SYMBOL_GPL(unwind_get_return_address
);
23 unsigned long *unwind_get_return_address_ptr(struct unwind_state
*state
)
25 if (unwind_done(state
))
28 return state
->regs
? &state
->regs
->ip
: state
->bp
+ 1;
31 static void unwind_dump(struct unwind_state
*state
)
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;
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
);
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
))
53 for (; sp
< stack_info
.end
; sp
++) {
55 word
= READ_ONCE_NOCHECK(*sp
);
62 printk_deferred("%p: %0*x ...\n",
63 sp
, BITS_PER_LONG
/4, 0);
67 printk_deferred("%p: %0*lx (%pB)\n",
68 sp
, BITS_PER_LONG
/4, word
, (void *)word
);
73 static bool in_entry_code(unsigned long ip
)
75 char *addr
= (char *)ip
;
77 if (addr
>= __entry_text_start
&& addr
< __entry_text_end
)
80 if (addr
>= __irqentry_text_start
&& addr
< __irqentry_text_end
)
86 static inline unsigned long *last_frame(struct unwind_state
*state
)
88 return (unsigned long *)task_pt_regs(state
->task
) - 2;
91 static bool is_last_frame(struct unwind_state
*state
)
93 return state
->bp
== last_frame(state
);
97 #define GCC_REALIGN_WORDS 3
99 #define GCC_REALIGN_WORDS 1
102 static inline unsigned long *last_aligned_frame(struct unwind_state
*state
)
104 return last_frame(state
) - GCC_REALIGN_WORDS
;
107 static bool is_last_aligned_frame(struct unwind_state
*state
)
109 unsigned long *last_bp
= last_frame(state
);
110 unsigned long *aligned_bp
= last_aligned_frame(state
);
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:
120 * and $0xfffffff8,%esp
125 * <x86_64_start_kernel>:
127 * and $0xfffffffffffffff0,%rsp
132 * After aligning the stack, it pushes a duplicate copy of the return
133 * address before pushing the frame pointer.
135 return (state
->bp
== aligned_bp
&& *(aligned_bp
+ 1) == *(last_bp
+ 1));
138 static bool is_last_ftrace_frame(struct unwind_state
*state
)
140 unsigned long *last_bp
= last_frame(state
);
141 unsigned long *last_ftrace_bp
= last_bp
- 3;
144 * When unwinding from an ftrace handler of a function called by entry
145 * code, the stack layout of the last frame is:
155 return (state
->bp
== last_ftrace_bp
&&
156 *state
->bp
== *(state
->bp
+ 2) &&
157 *(state
->bp
+ 1) == *(state
->bp
+ 4));
160 static bool is_last_task_frame(struct unwind_state
*state
)
162 return is_last_frame(state
) || is_last_aligned_frame(state
) ||
163 is_last_ftrace_frame(state
);
167 * This determines if the frame pointer actually contains an encoded pointer to
168 * pt_regs on the stack. See ENCODE_FRAME_POINTER.
171 static struct pt_regs
*decode_frame_pointer(unsigned long *bp
)
173 unsigned long regs
= (unsigned long)bp
;
178 return (struct pt_regs
*)(regs
& ~0x1);
181 static struct pt_regs
*decode_frame_pointer(unsigned long *bp
)
183 unsigned long regs
= (unsigned long)bp
;
185 if (regs
& 0x80000000)
188 return (struct pt_regs
*)(regs
| 0x80000000);
192 static bool update_stack_state(struct unwind_state
*state
,
193 unsigned long *next_bp
)
195 struct stack_info
*info
= &state
->stack_info
;
196 enum stack_type prev_type
= info
->type
;
197 struct pt_regs
*regs
;
198 unsigned long *frame
, *prev_frame_end
, *addr_p
, addr
;
202 prev_frame_end
= (void *)state
->regs
+ sizeof(*state
->regs
);
204 prev_frame_end
= (void *)state
->bp
+ FRAME_HEADER_SIZE
;
206 /* Is the next frame pointer an encoded pointer to pt_regs? */
207 regs
= decode_frame_pointer(next_bp
);
209 frame
= (unsigned long *)regs
;
211 state
->got_irq
= true;
214 len
= FRAME_HEADER_SIZE
;
218 * If the next bp isn't on the current stack, switch to the next one.
220 * We may have to traverse multiple stacks to deal with the possibility
221 * that info->next_sp could point to an empty stack and the next bp
222 * could be on a subsequent stack.
224 while (!on_stack(info
, frame
, len
))
225 if (get_stack_info(info
->next_sp
, state
->task
, info
,
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
)
234 /* Move state to the next frame: */
243 /* Save the return address: */
244 if (state
->regs
&& user_mode(state
->regs
))
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
,
253 /* Save the original stack pointer for unwind_dump(): */
255 state
->orig_sp
= frame
;
260 bool unwind_next_frame(struct unwind_state
*state
)
262 struct pt_regs
*regs
;
263 unsigned long *next_bp
;
265 if (unwind_done(state
))
268 /* Have we reached the end? */
269 if (state
->regs
&& user_mode(state
->regs
))
272 if (is_last_task_frame(state
)) {
273 regs
= task_pt_regs(state
->task
);
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.
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.
286 if (!user_mode(regs
))
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.
300 /* Get the next frame pointer: */
301 if (state
->next_bp
) {
302 next_bp
= state
->next_bp
;
303 state
->next_bp
= NULL
;
304 } else if (state
->regs
) {
305 next_bp
= (unsigned long *)state
->regs
->bp
;
307 next_bp
= (unsigned long *)READ_ONCE_TASK_STACK(state
->task
, *state
->bp
);
310 /* Move to the next frame if it's safe: */
311 if (!update_stack_state(state
, next_bp
))
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.
326 if (state
->task
!= current
)
330 * Don't warn if the unwinder got lost due to an interrupt in entry
331 * code or in the C handler before the first frame pointer got set up:
333 if (state
->got_irq
&& in_entry_code(state
->ip
))
336 state
->regs
->sp
>= (unsigned long)last_aligned_frame(state
) &&
337 state
->regs
->sp
< (unsigned long)task_pt_regs(state
->task
))
341 * There are some known frame pointer issues on 32-bit. Disable
342 * unwinder warnings on 32-bit until it gets objtool support.
344 if (IS_ENABLED(CONFIG_X86_32
))
347 if (state
->task
!= current
)
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
,
354 state
->task
->pid
, next_bp
);
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
,
360 state
->task
->pid
, next_bp
);
364 state
->stack_info
.type
= STACK_TYPE_UNKNOWN
;
367 EXPORT_SYMBOL_GPL(unwind_next_frame
);
369 void __unwind_start(struct unwind_state
*state
, struct task_struct
*task
,
370 struct pt_regs
*regs
, unsigned long *first_frame
)
374 memset(state
, 0, sizeof(*state
));
376 state
->got_irq
= (regs
);
378 /* Don't even attempt to start from user mode regs: */
379 if (regs
&& user_mode(regs
)) {
380 state
->stack_info
.type
= STACK_TYPE_UNKNOWN
;
384 bp
= get_frame_pointer(task
, regs
);
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.
395 if (regs
&& regs
->ip
== 0 && (unsigned long *)regs
->sp
>= first_frame
) {
397 bp
= ((unsigned long *)regs
->sp
) - 1;
400 /* Initialize stack info and make sure the frame data is accessible: */
401 get_stack_info(bp
, state
->task
, &state
->stack_info
,
403 update_stack_state(state
, bp
);
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.
410 while (!unwind_done(state
) &&
411 (!on_stack(&state
->stack_info
, first_frame
, sizeof(long)) ||
412 (state
->next_bp
== NULL
&& state
->bp
< first_frame
)))
413 unwind_next_frame(state
);
415 EXPORT_SYMBOL_GPL(__unwind_start
);