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)
13 unsigned long unwind_get_return_address(struct unwind_state *state)
15 if (unwind_done(state))
18 return __kernel_text_address(state->ip) ? state->ip : 0;
20 EXPORT_SYMBOL_GPL(unwind_get_return_address);
22 unsigned long *unwind_get_return_address_ptr(struct unwind_state *state)
24 if (unwind_done(state))
27 return state->regs ? &state->regs->ip : state->bp + 1;
30 static void unwind_dump(struct unwind_state *state)
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;
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);
47 for (sp = state->orig_sp; sp; sp = PTR_ALIGN(stack_info.next_sp, sizeof(long))) {
48 if (get_stack_info(sp, state->task, &stack_info, &visit_mask))
51 for (; sp < stack_info.end; sp++) {
53 word = READ_ONCE_NOCHECK(*sp);
60 printk_deferred("%p: %0*x ...\n",
61 sp, BITS_PER_LONG/4, 0);
65 printk_deferred("%p: %0*lx (%pB)\n",
66 sp, BITS_PER_LONG/4, word, (void *)word);
71 static size_t regs_size(struct pt_regs *regs)
73 /* x86_32 regs from kernel mode are two words shorter: */
74 if (IS_ENABLED(CONFIG_X86_32) && !user_mode(regs))
75 return sizeof(*regs) - 2*sizeof(long);
80 static bool in_entry_code(unsigned long ip)
82 char *addr = (char *)ip;
84 if (addr >= __entry_text_start && addr < __entry_text_end)
87 if (addr >= __irqentry_text_start && addr < __irqentry_text_end)
93 static inline unsigned long *last_frame(struct unwind_state *state)
95 return (unsigned long *)task_pt_regs(state->task) - 2;
98 static bool is_last_frame(struct unwind_state *state)
100 return state->bp == last_frame(state);
104 #define GCC_REALIGN_WORDS 3
106 #define GCC_REALIGN_WORDS 1
109 static inline unsigned long *last_aligned_frame(struct unwind_state *state)
111 return last_frame(state) - GCC_REALIGN_WORDS;
114 static bool is_last_aligned_frame(struct unwind_state *state)
116 unsigned long *last_bp = last_frame(state);
117 unsigned long *aligned_bp = last_aligned_frame(state);
120 * GCC can occasionally decide to realign the stack pointer and change
121 * the offset of the stack frame in the prologue of a function called
122 * by head/entry code. Examples:
127 * and $0xfffffff8,%esp
132 * <x86_64_start_kernel>:
134 * and $0xfffffffffffffff0,%rsp
139 * After aligning the stack, it pushes a duplicate copy of the return
140 * address before pushing the frame pointer.
142 return (state->bp == aligned_bp && *(aligned_bp + 1) == *(last_bp + 1));
145 static bool is_last_ftrace_frame(struct unwind_state *state)
147 unsigned long *last_bp = last_frame(state);
148 unsigned long *last_ftrace_bp = last_bp - 3;
151 * When unwinding from an ftrace handler of a function called by entry
152 * code, the stack layout of the last frame is:
162 return (state->bp == last_ftrace_bp &&
163 *state->bp == *(state->bp + 2) &&
164 *(state->bp + 1) == *(state->bp + 4));
167 static bool is_last_task_frame(struct unwind_state *state)
169 return is_last_frame(state) || is_last_aligned_frame(state) ||
170 is_last_ftrace_frame(state);
174 * This determines if the frame pointer actually contains an encoded pointer to
175 * pt_regs on the stack. See ENCODE_FRAME_POINTER.
177 static struct pt_regs *decode_frame_pointer(unsigned long *bp)
179 unsigned long regs = (unsigned long)bp;
184 return (struct pt_regs *)(regs & ~0x1);
187 static bool update_stack_state(struct unwind_state *state,
188 unsigned long *next_bp)
190 struct stack_info *info = &state->stack_info;
191 enum stack_type prev_type = info->type;
192 struct pt_regs *regs;
193 unsigned long *frame, *prev_frame_end, *addr_p, addr;
197 prev_frame_end = (void *)state->regs + regs_size(state->regs);
199 prev_frame_end = (void *)state->bp + FRAME_HEADER_SIZE;
201 /* Is the next frame pointer an encoded pointer to pt_regs? */
202 regs = decode_frame_pointer(next_bp);
204 frame = (unsigned long *)regs;
205 len = regs_size(regs);
206 state->got_irq = true;
209 len = FRAME_HEADER_SIZE;
213 * If the next bp isn't on the current stack, switch to the next one.
215 * We may have to traverse multiple stacks to deal with the possibility
216 * that info->next_sp could point to an empty stack and the next bp
217 * could be on a subsequent stack.
219 while (!on_stack(info, frame, len))
220 if (get_stack_info(info->next_sp, state->task, info,
224 /* Make sure it only unwinds up and doesn't overlap the prev frame: */
225 if (state->orig_sp && state->stack_info.type == prev_type &&
226 frame < prev_frame_end)
229 /* Move state to the next frame: */
238 /* Save the return address: */
239 if (state->regs && user_mode(state->regs))
242 addr_p = unwind_get_return_address_ptr(state);
243 addr = READ_ONCE_TASK_STACK(state->task, *addr_p);
244 state->ip = ftrace_graph_ret_addr(state->task, &state->graph_idx,
248 /* Save the original stack pointer for unwind_dump(): */
250 state->orig_sp = frame;
255 bool unwind_next_frame(struct unwind_state *state)
257 struct pt_regs *regs;
258 unsigned long *next_bp;
260 if (unwind_done(state))
263 /* Have we reached the end? */
264 if (state->regs && user_mode(state->regs))
267 if (is_last_task_frame(state)) {
268 regs = task_pt_regs(state->task);
271 * kthreads (other than the boot CPU's idle thread) have some
272 * partial regs at the end of their stack which were placed
273 * there by copy_thread_tls(). But the regs don't have any
274 * useful information, so we can skip them.
276 * This user_mode() check is slightly broader than a PF_KTHREAD
277 * check because it also catches the awkward situation where a
278 * newly forked kthread transitions into a user task by calling
279 * do_execve(), which eventually clears PF_KTHREAD.
281 if (!user_mode(regs))
285 * We're almost at the end, but not quite: there's still the
286 * syscall regs frame. Entry code doesn't encode the regs
287 * pointer for syscalls, so we have to set it manually.
295 /* Get the next frame pointer: */
297 next_bp = (unsigned long *)state->regs->bp;
299 next_bp = (unsigned long *)READ_ONCE_TASK_STACK(state->task, *state->bp);
301 /* Move to the next frame if it's safe: */
302 if (!update_stack_state(state, next_bp))
311 * When unwinding a non-current task, the task might actually be
312 * running on another CPU, in which case it could be modifying its
313 * stack while we're reading it. This is generally not a problem and
314 * can be ignored as long as the caller understands that unwinding
315 * another task will not always succeed.
317 if (state->task != current)
321 * Don't warn if the unwinder got lost due to an interrupt in entry
322 * code or in the C handler before the first frame pointer got set up:
324 if (state->got_irq && in_entry_code(state->ip))
327 state->regs->sp >= (unsigned long)last_aligned_frame(state) &&
328 state->regs->sp < (unsigned long)task_pt_regs(state->task))
332 printk_deferred_once(KERN_WARNING
333 "WARNING: kernel stack regs at %p in %s:%d has bad 'bp' value %p\n",
334 state->regs, state->task->comm,
335 state->task->pid, next_bp);
338 printk_deferred_once(KERN_WARNING
339 "WARNING: kernel stack frame pointer at %p in %s:%d has bad value %p\n",
340 state->bp, state->task->comm,
341 state->task->pid, next_bp);
345 state->stack_info.type = STACK_TYPE_UNKNOWN;
348 EXPORT_SYMBOL_GPL(unwind_next_frame);
350 void __unwind_start(struct unwind_state *state, struct task_struct *task,
351 struct pt_regs *regs, unsigned long *first_frame)
355 memset(state, 0, sizeof(*state));
357 state->got_irq = (regs);
359 /* Don't even attempt to start from user mode regs: */
360 if (regs && user_mode(regs)) {
361 state->stack_info.type = STACK_TYPE_UNKNOWN;
365 bp = get_frame_pointer(task, regs);
367 /* Initialize stack info and make sure the frame data is accessible: */
368 get_stack_info(bp, state->task, &state->stack_info,
370 update_stack_state(state, bp);
373 * The caller can provide the address of the first frame directly
374 * (first_frame) or indirectly (regs->sp) to indicate which stack frame
375 * to start unwinding at. Skip ahead until we reach it.
377 while (!unwind_done(state) &&
378 (!on_stack(&state->stack_info, first_frame, sizeof(long)) ||
379 state->bp < first_frame))
380 unwind_next_frame(state);
382 EXPORT_SYMBOL_GPL(__unwind_start);