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>
11 #define FRAME_HEADER_SIZE (sizeof(long) * 2)
14 * This disables KASAN checking when reading a value from another task's stack,
15 * since the other task could be running on another CPU and could have poisoned
16 * the stack in the meantime.
18 #define READ_ONCE_TASK_STACK(task, x) \
21 if (task == current) \
24 val = READ_ONCE_NOCHECK(x); \
28 static void unwind_dump(struct unwind_state
*state
)
30 static bool dumped_before
= false;
31 bool prev_zero
, zero
= false;
32 unsigned long word
, *sp
;
33 struct stack_info stack_info
= {0};
34 unsigned long visit_mask
= 0;
41 printk_deferred("unwind stack type:%d next_sp:%p mask:0x%lx graph_idx:%d\n",
42 state
->stack_info
.type
, state
->stack_info
.next_sp
,
43 state
->stack_mask
, state
->graph_idx
);
45 for (sp
= state
->orig_sp
; sp
; sp
= PTR_ALIGN(stack_info
.next_sp
, sizeof(long))) {
46 if (get_stack_info(sp
, state
->task
, &stack_info
, &visit_mask
))
49 for (; sp
< stack_info
.end
; sp
++) {
51 word
= READ_ONCE_NOCHECK(*sp
);
58 printk_deferred("%p: %0*x ...\n",
59 sp
, BITS_PER_LONG
/4, 0);
63 printk_deferred("%p: %0*lx (%pB)\n",
64 sp
, BITS_PER_LONG
/4, word
, (void *)word
);
69 unsigned long unwind_get_return_address(struct unwind_state
*state
)
71 if (unwind_done(state
))
74 return __kernel_text_address(state
->ip
) ? state
->ip
: 0;
76 EXPORT_SYMBOL_GPL(unwind_get_return_address
);
78 static size_t regs_size(struct pt_regs
*regs
)
80 /* x86_32 regs from kernel mode are two words shorter: */
81 if (IS_ENABLED(CONFIG_X86_32
) && !user_mode(regs
))
82 return sizeof(*regs
) - 2*sizeof(long);
87 static bool in_entry_code(unsigned long ip
)
89 char *addr
= (char *)ip
;
91 if (addr
>= __entry_text_start
&& addr
< __entry_text_end
)
94 #if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN)
95 if (addr
>= __irqentry_text_start
&& addr
< __irqentry_text_end
)
102 static inline unsigned long *last_frame(struct unwind_state
*state
)
104 return (unsigned long *)task_pt_regs(state
->task
) - 2;
107 static bool is_last_frame(struct unwind_state
*state
)
109 return state
->bp
== last_frame(state
);
113 #define GCC_REALIGN_WORDS 3
115 #define GCC_REALIGN_WORDS 1
118 static inline unsigned long *last_aligned_frame(struct unwind_state
*state
)
120 return last_frame(state
) - GCC_REALIGN_WORDS
;
123 static bool is_last_aligned_frame(struct unwind_state
*state
)
125 unsigned long *last_bp
= last_frame(state
);
126 unsigned long *aligned_bp
= last_aligned_frame(state
);
129 * GCC can occasionally decide to realign the stack pointer and change
130 * the offset of the stack frame in the prologue of a function called
131 * by head/entry code. Examples:
136 * and $0xfffffff8,%esp
141 * <x86_64_start_kernel>:
143 * and $0xfffffffffffffff0,%rsp
148 * After aligning the stack, it pushes a duplicate copy of the return
149 * address before pushing the frame pointer.
151 return (state
->bp
== aligned_bp
&& *(aligned_bp
+ 1) == *(last_bp
+ 1));
154 static bool is_last_ftrace_frame(struct unwind_state
*state
)
156 unsigned long *last_bp
= last_frame(state
);
157 unsigned long *last_ftrace_bp
= last_bp
- 3;
160 * When unwinding from an ftrace handler of a function called by entry
161 * code, the stack layout of the last frame is:
171 return (state
->bp
== last_ftrace_bp
&&
172 *state
->bp
== *(state
->bp
+ 2) &&
173 *(state
->bp
+ 1) == *(state
->bp
+ 4));
176 static bool is_last_task_frame(struct unwind_state
*state
)
178 return is_last_frame(state
) || is_last_aligned_frame(state
) ||
179 is_last_ftrace_frame(state
);
183 * This determines if the frame pointer actually contains an encoded pointer to
184 * pt_regs on the stack. See ENCODE_FRAME_POINTER.
186 static struct pt_regs
*decode_frame_pointer(unsigned long *bp
)
188 unsigned long regs
= (unsigned long)bp
;
193 return (struct pt_regs
*)(regs
& ~0x1);
196 static bool update_stack_state(struct unwind_state
*state
,
197 unsigned long *next_bp
)
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
;
206 prev_frame_end
= (void *)state
->regs
+ regs_size(state
->regs
);
208 prev_frame_end
= (void *)state
->bp
+ FRAME_HEADER_SIZE
;
210 /* Is the next frame pointer an encoded pointer to pt_regs? */
211 regs
= decode_frame_pointer(next_bp
);
213 frame
= (unsigned long *)regs
;
214 len
= regs_size(regs
);
215 state
->got_irq
= true;
218 len
= FRAME_HEADER_SIZE
;
222 * If the next bp isn't on the current stack, switch to the next one.
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.
228 while (!on_stack(info
, frame
, len
))
229 if (get_stack_info(info
->next_sp
, state
->task
, info
,
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
)
238 /* Move state to the next frame: */
247 /* Save the return address: */
248 if (state
->regs
&& user_mode(state
->regs
))
251 addr_p
= unwind_get_return_address_ptr(state
);
252 addr
= READ_ONCE_TASK_STACK(state
->task
, *addr_p
);
253 state
->ip
= ftrace_graph_ret_addr(state
->task
, &state
->graph_idx
,
257 /* Save the original stack pointer for unwind_dump(): */
259 state
->orig_sp
= frame
;
264 bool unwind_next_frame(struct unwind_state
*state
)
266 struct pt_regs
*regs
;
267 unsigned long *next_bp
;
269 if (unwind_done(state
))
272 /* Have we reached the end? */
273 if (state
->regs
&& user_mode(state
->regs
))
276 if (is_last_task_frame(state
)) {
277 regs
= task_pt_regs(state
->task
);
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_tls(). But the regs don't have any
283 * useful information, so we can skip them.
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 * do_execve(), which eventually clears PF_KTHREAD.
290 if (!user_mode(regs
))
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.
304 /* Get the next frame pointer: */
306 next_bp
= (unsigned long *)state
->regs
->bp
;
308 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 printk_deferred_once(KERN_WARNING
342 "WARNING: kernel stack regs at %p in %s:%d has bad 'bp' value %p\n",
343 state
->regs
, state
->task
->comm
,
344 state
->task
->pid
, next_bp
);
347 printk_deferred_once(KERN_WARNING
348 "WARNING: kernel stack frame pointer at %p in %s:%d has bad value %p\n",
349 state
->bp
, state
->task
->comm
,
350 state
->task
->pid
, next_bp
);
354 state
->stack_info
.type
= STACK_TYPE_UNKNOWN
;
357 EXPORT_SYMBOL_GPL(unwind_next_frame
);
359 void __unwind_start(struct unwind_state
*state
, struct task_struct
*task
,
360 struct pt_regs
*regs
, unsigned long *first_frame
)
364 memset(state
, 0, sizeof(*state
));
366 state
->got_irq
= (regs
);
368 /* Don't even attempt to start from user mode regs: */
369 if (regs
&& user_mode(regs
)) {
370 state
->stack_info
.type
= STACK_TYPE_UNKNOWN
;
374 bp
= get_frame_pointer(task
, regs
);
376 /* Initialize stack info and make sure the frame data is accessible: */
377 get_stack_info(bp
, state
->task
, &state
->stack_info
,
379 update_stack_state(state
, bp
);
382 * The caller can provide the address of the first frame directly
383 * (first_frame) or indirectly (regs->sp) to indicate which stack frame
384 * to start unwinding at. Skip ahead until we reach it.
386 while (!unwind_done(state
) &&
387 (!on_stack(&state
->stack_info
, first_frame
, sizeof(long)) ||
388 state
->bp
< first_frame
))
389 unwind_next_frame(state
);
391 EXPORT_SYMBOL_GPL(__unwind_start
);