1 // SPDX-License-Identifier: GPL-2.0-only
2 #include <linux/module.h>
3 #include <linux/sort.h>
4 #include <asm/ptrace.h>
5 #include <asm/stacktrace.h>
6 #include <asm/unwind.h>
7 #include <asm/orc_types.h>
8 #include <asm/orc_lookup.h>
10 #define orc_warn(fmt, ...) \
11 printk_deferred_once(KERN_WARNING "WARNING: " fmt, ##__VA_ARGS__)
13 #define orc_warn_current(args...) \
15 if (state->task == current) \
19 extern int __start_orc_unwind_ip[];
20 extern int __stop_orc_unwind_ip[];
21 extern struct orc_entry __start_orc_unwind[];
22 extern struct orc_entry __stop_orc_unwind[];
24 static bool orc_init __ro_after_init;
25 static unsigned int lookup_num_blocks __ro_after_init;
27 static DEFINE_MUTEX(sort_mutex);
28 static int *cur_orc_ip_table = __start_orc_unwind_ip;
29 static struct orc_entry *cur_orc_table = __start_orc_unwind;
31 static inline unsigned long orc_ip(const int *ip)
33 return (unsigned long)ip + *ip;
36 static struct orc_entry *__orc_find(int *ip_table, struct orc_entry *u_table,
37 unsigned int num_entries, unsigned long ip)
39 int *first = ip_table;
40 int *last = ip_table + num_entries - 1;
41 int *mid = first, *found = first;
47 * Do a binary range search to find the rightmost duplicate of a given
48 * starting address. Some entries are section terminators which are
49 * "weak" entries for ensuring there are no gaps. They should be
50 * ignored when they conflict with a real entry.
52 while (first <= last) {
53 mid = first + ((last - first) / 2);
55 if (orc_ip(mid) <= ip) {
62 return u_table + (found - ip_table);
66 static struct orc_entry *orc_module_find(unsigned long ip)
70 mod = __module_address(ip);
71 if (!mod || !mod->arch.orc_unwind || !mod->arch.orc_unwind_ip)
73 return __orc_find(mod->arch.orc_unwind_ip, mod->arch.orc_unwind,
74 mod->arch.num_orcs, ip);
77 static struct orc_entry *orc_module_find(unsigned long ip)
83 #ifdef CONFIG_DYNAMIC_FTRACE
84 static struct orc_entry *orc_find(unsigned long ip);
87 * Ftrace dynamic trampolines do not have orc entries of their own.
88 * But they are copies of the ftrace entries that are static and
89 * defined in ftrace_*.S, which do have orc entries.
91 * If the unwinder comes across a ftrace trampoline, then find the
92 * ftrace function that was used to create it, and use that ftrace
93 * function's orc entry, as the placement of the return code in
94 * the stack will be identical.
96 static struct orc_entry *orc_ftrace_find(unsigned long ip)
98 struct ftrace_ops *ops;
101 ops = ftrace_ops_trampoline(ip);
105 if (ops->flags & FTRACE_OPS_FL_SAVE_REGS)
106 caller = (unsigned long)ftrace_regs_call;
108 caller = (unsigned long)ftrace_call;
110 /* Prevent unlikely recursion */
114 return orc_find(caller);
117 static struct orc_entry *orc_ftrace_find(unsigned long ip)
124 * If we crash with IP==0, the last successfully executed instruction
125 * was probably an indirect function call with a NULL function pointer,
126 * and we don't have unwind information for NULL.
127 * This hardcoded ORC entry for IP==0 allows us to unwind from a NULL function
128 * pointer into its parent and then continue normally from there.
130 static struct orc_entry null_orc_entry = {
131 .sp_offset = sizeof(long),
132 .sp_reg = ORC_REG_SP,
133 .bp_reg = ORC_REG_UNDEFINED,
134 .type = ORC_TYPE_CALL
137 /* Fake frame pointer entry -- used as a fallback for generated code */
138 static struct orc_entry orc_fp_entry = {
139 .type = ORC_TYPE_CALL,
140 .sp_reg = ORC_REG_BP,
142 .bp_reg = ORC_REG_PREV_SP,
147 static struct orc_entry *orc_find(unsigned long ip)
149 static struct orc_entry *orc;
155 return &null_orc_entry;
157 /* For non-init vmlinux addresses, use the fast lookup table: */
158 if (ip >= LOOKUP_START_IP && ip < LOOKUP_STOP_IP) {
159 unsigned int idx, start, stop;
161 idx = (ip - LOOKUP_START_IP) / LOOKUP_BLOCK_SIZE;
163 if (unlikely((idx >= lookup_num_blocks-1))) {
164 orc_warn("WARNING: bad lookup idx: idx=%u num=%u ip=%pB\n",
165 idx, lookup_num_blocks, (void *)ip);
169 start = orc_lookup[idx];
170 stop = orc_lookup[idx + 1] + 1;
172 if (unlikely((__start_orc_unwind + start >= __stop_orc_unwind) ||
173 (__start_orc_unwind + stop > __stop_orc_unwind))) {
174 orc_warn("WARNING: bad lookup value: idx=%u num=%u start=%u stop=%u ip=%pB\n",
175 idx, lookup_num_blocks, start, stop, (void *)ip);
179 return __orc_find(__start_orc_unwind_ip + start,
180 __start_orc_unwind + start, stop - start, ip);
183 /* vmlinux .init slow lookup: */
184 if (init_kernel_text(ip))
185 return __orc_find(__start_orc_unwind_ip, __start_orc_unwind,
186 __stop_orc_unwind_ip - __start_orc_unwind_ip, ip);
189 orc = orc_module_find(ip);
193 return orc_ftrace_find(ip);
196 #ifdef CONFIG_MODULES
198 static void orc_sort_swap(void *_a, void *_b, int size)
200 struct orc_entry *orc_a, *orc_b;
201 struct orc_entry orc_tmp;
202 int *a = _a, *b = _b, tmp;
205 /* Swap the .orc_unwind_ip entries: */
210 /* Swap the corresponding .orc_unwind entries: */
211 orc_a = cur_orc_table + (a - cur_orc_ip_table);
212 orc_b = cur_orc_table + (b - cur_orc_ip_table);
218 static int orc_sort_cmp(const void *_a, const void *_b)
220 struct orc_entry *orc_a;
221 const int *a = _a, *b = _b;
222 unsigned long a_val = orc_ip(a);
223 unsigned long b_val = orc_ip(b);
231 * The "weak" section terminator entries need to always be on the left
232 * to ensure the lookup code skips them in favor of real entries.
233 * These terminator entries exist to handle any gaps created by
234 * whitelisted .o files which didn't get objtool generation.
236 orc_a = cur_orc_table + (a - cur_orc_ip_table);
237 return orc_a->sp_reg == ORC_REG_UNDEFINED && !orc_a->end ? -1 : 1;
240 void unwind_module_init(struct module *mod, void *_orc_ip, size_t orc_ip_size,
241 void *_orc, size_t orc_size)
243 int *orc_ip = _orc_ip;
244 struct orc_entry *orc = _orc;
245 unsigned int num_entries = orc_ip_size / sizeof(int);
247 WARN_ON_ONCE(orc_ip_size % sizeof(int) != 0 ||
248 orc_size % sizeof(*orc) != 0 ||
249 num_entries != orc_size / sizeof(*orc));
252 * The 'cur_orc_*' globals allow the orc_sort_swap() callback to
253 * associate an .orc_unwind_ip table entry with its corresponding
254 * .orc_unwind entry so they can both be swapped.
256 mutex_lock(&sort_mutex);
257 cur_orc_ip_table = orc_ip;
259 sort(orc_ip, num_entries, sizeof(int), orc_sort_cmp, orc_sort_swap);
260 mutex_unlock(&sort_mutex);
262 mod->arch.orc_unwind_ip = orc_ip;
263 mod->arch.orc_unwind = orc;
264 mod->arch.num_orcs = num_entries;
268 void __init unwind_init(void)
270 size_t orc_ip_size = (void *)__stop_orc_unwind_ip - (void *)__start_orc_unwind_ip;
271 size_t orc_size = (void *)__stop_orc_unwind - (void *)__start_orc_unwind;
272 size_t num_entries = orc_ip_size / sizeof(int);
273 struct orc_entry *orc;
276 if (!num_entries || orc_ip_size % sizeof(int) != 0 ||
277 orc_size % sizeof(struct orc_entry) != 0 ||
278 num_entries != orc_size / sizeof(struct orc_entry)) {
279 orc_warn("WARNING: Bad or missing .orc_unwind table. Disabling unwinder.\n");
284 * Note, the orc_unwind and orc_unwind_ip tables were already
285 * sorted at build time via the 'sorttable' tool.
286 * It's ready for binary search straight away, no need to sort it.
289 /* Initialize the fast lookup table: */
290 lookup_num_blocks = orc_lookup_end - orc_lookup;
291 for (i = 0; i < lookup_num_blocks-1; i++) {
292 orc = __orc_find(__start_orc_unwind_ip, __start_orc_unwind,
294 LOOKUP_START_IP + (LOOKUP_BLOCK_SIZE * i));
296 orc_warn("WARNING: Corrupt .orc_unwind table. Disabling unwinder.\n");
300 orc_lookup[i] = orc - __start_orc_unwind;
303 /* Initialize the ending block: */
304 orc = __orc_find(__start_orc_unwind_ip, __start_orc_unwind, num_entries,
307 orc_warn("WARNING: Corrupt .orc_unwind table. Disabling unwinder.\n");
310 orc_lookup[lookup_num_blocks-1] = orc - __start_orc_unwind;
315 unsigned long unwind_get_return_address(struct unwind_state *state)
317 if (unwind_done(state))
320 return __kernel_text_address(state->ip) ? state->ip : 0;
322 EXPORT_SYMBOL_GPL(unwind_get_return_address);
324 unsigned long *unwind_get_return_address_ptr(struct unwind_state *state)
326 if (unwind_done(state))
330 return &state->regs->ip;
333 return (unsigned long *)state->sp - 1;
338 static bool stack_access_ok(struct unwind_state *state, unsigned long _addr,
341 struct stack_info *info = &state->stack_info;
342 void *addr = (void *)_addr;
344 if (!on_stack(info, addr, len) &&
345 (get_stack_info(addr, state->task, info, &state->stack_mask)))
351 static bool deref_stack_reg(struct unwind_state *state, unsigned long addr,
354 if (!stack_access_ok(state, addr, sizeof(long)))
357 *val = READ_ONCE_NOCHECK(*(unsigned long *)addr);
361 static bool deref_stack_regs(struct unwind_state *state, unsigned long addr,
362 unsigned long *ip, unsigned long *sp)
364 struct pt_regs *regs = (struct pt_regs *)addr;
366 /* x86-32 support will be more complicated due to the ®s->sp hack */
367 BUILD_BUG_ON(IS_ENABLED(CONFIG_X86_32));
369 if (!stack_access_ok(state, addr, sizeof(struct pt_regs)))
377 static bool deref_stack_iret_regs(struct unwind_state *state, unsigned long addr,
378 unsigned long *ip, unsigned long *sp)
380 struct pt_regs *regs = (void *)addr - IRET_FRAME_OFFSET;
382 if (!stack_access_ok(state, addr, IRET_FRAME_SIZE))
390 bool unwind_next_frame(struct unwind_state *state)
392 unsigned long ip_p, sp, orig_ip = state->ip, prev_sp = state->sp;
393 enum stack_type prev_type = state->stack_info.type;
394 struct orc_entry *orc;
395 bool indirect = false;
397 if (unwind_done(state))
400 /* Don't let modules unload while we're reading their ORC data. */
403 /* End-of-stack check for user tasks: */
404 if (state->regs && user_mode(state->regs))
408 * Find the orc_entry associated with the text address.
410 * Decrement call return addresses by one so they work for sibling
411 * calls and calls to noreturn functions.
413 orc = orc_find(state->signal ? state->ip : state->ip - 1);
416 * As a fallback, try to assume this code uses a frame pointer.
417 * This is useful for generated code, like BPF, which ORC
418 * doesn't know about. This is just a guess, so the rest of
419 * the unwind is no longer considered reliable.
425 /* End-of-stack check for kernel threads: */
426 if (orc->sp_reg == ORC_REG_UNDEFINED) {
433 /* Find the previous frame's stack: */
434 switch (orc->sp_reg) {
436 sp = state->sp + orc->sp_offset;
440 sp = state->bp + orc->sp_offset;
443 case ORC_REG_SP_INDIRECT:
444 sp = state->sp + orc->sp_offset;
448 case ORC_REG_BP_INDIRECT:
449 sp = state->bp + orc->sp_offset;
454 if (!state->regs || !state->full_regs) {
455 orc_warn_current("missing R10 value at %pB\n",
459 sp = state->regs->r10;
463 if (!state->regs || !state->full_regs) {
464 orc_warn_current("missing R13 value at %pB\n",
468 sp = state->regs->r13;
472 if (!state->regs || !state->full_regs) {
473 orc_warn_current("missing RDI value at %pB\n",
477 sp = state->regs->di;
481 if (!state->regs || !state->full_regs) {
482 orc_warn_current("missing DX value at %pB\n",
486 sp = state->regs->dx;
490 orc_warn("unknown SP base reg %d at %pB\n",
491 orc->sp_reg, (void *)state->ip);
496 if (!deref_stack_reg(state, sp, &sp))
500 /* Find IP, SP and possibly regs: */
503 ip_p = sp - sizeof(long);
505 if (!deref_stack_reg(state, ip_p, &state->ip))
508 state->ip = ftrace_graph_ret_addr(state->task, &state->graph_idx,
509 state->ip, (void *)ip_p);
513 state->signal = false;
517 if (!deref_stack_regs(state, sp, &state->ip, &state->sp)) {
518 orc_warn_current("can't access registers at %pB\n",
523 state->regs = (struct pt_regs *)sp;
524 state->full_regs = true;
525 state->signal = true;
528 case ORC_TYPE_REGS_IRET:
529 if (!deref_stack_iret_regs(state, sp, &state->ip, &state->sp)) {
530 orc_warn_current("can't access iret registers at %pB\n",
535 state->regs = (void *)sp - IRET_FRAME_OFFSET;
536 state->full_regs = false;
537 state->signal = true;
541 orc_warn("unknown .orc_unwind entry type %d at %pB\n",
542 orc->type, (void *)orig_ip);
547 switch (orc->bp_reg) {
548 case ORC_REG_UNDEFINED:
549 if (state->regs && state->full_regs)
550 state->bp = state->regs->bp;
553 case ORC_REG_PREV_SP:
554 if (!deref_stack_reg(state, sp + orc->bp_offset, &state->bp))
559 if (!deref_stack_reg(state, state->bp + orc->bp_offset, &state->bp))
564 orc_warn("unknown BP base reg %d for ip %pB\n",
565 orc->bp_reg, (void *)orig_ip);
569 /* Prevent a recursive loop due to bad ORC data: */
570 if (state->stack_info.type == prev_type &&
571 on_stack(&state->stack_info, (void *)state->sp, sizeof(long)) &&
572 state->sp <= prev_sp) {
573 orc_warn_current("stack going in the wrong direction? at %pB\n",
586 state->stack_info.type = STACK_TYPE_UNKNOWN;
589 EXPORT_SYMBOL_GPL(unwind_next_frame);
591 void __unwind_start(struct unwind_state *state, struct task_struct *task,
592 struct pt_regs *regs, unsigned long *first_frame)
594 memset(state, 0, sizeof(*state));
598 * Refuse to unwind the stack of a task while it's executing on another
599 * CPU. This check is racy, but that's ok: the unwinder has other
600 * checks to prevent it from going off the rails.
602 if (task_on_another_cpu(task))
609 state->ip = regs->ip;
610 state->sp = regs->sp;
611 state->bp = regs->bp;
613 state->full_regs = true;
614 state->signal = true;
616 } else if (task == current) {
617 asm volatile("lea (%%rip), %0\n\t"
620 : "=r" (state->ip), "=r" (state->sp),
624 struct inactive_task_frame *frame = (void *)task->thread.sp;
626 state->sp = task->thread.sp;
627 state->bp = READ_ONCE_NOCHECK(frame->bp);
628 state->ip = READ_ONCE_NOCHECK(frame->ret_addr);
631 if (get_stack_info((unsigned long *)state->sp, state->task,
632 &state->stack_info, &state->stack_mask)) {
634 * We weren't on a valid stack. It's possible that
635 * we overflowed a valid stack into a guard page.
636 * See if the next page up is valid so that we can
637 * generate some kind of backtrace if this happens.
639 void *next_page = (void *)PAGE_ALIGN((unsigned long)state->sp);
640 if (get_stack_info(next_page, state->task, &state->stack_info,
646 * The caller can provide the address of the first frame directly
647 * (first_frame) or indirectly (regs->sp) to indicate which stack frame
648 * to start unwinding at. Skip ahead until we reach it.
651 /* When starting from regs, skip the regs frame: */
653 unwind_next_frame(state);
657 /* Otherwise, skip ahead to the user-specified starting frame: */
658 while (!unwind_done(state) &&
659 (!on_stack(&state->stack_info, first_frame, sizeof(long)) ||
660 state->sp < (unsigned long)first_frame))
661 unwind_next_frame(state);
666 state->stack_info.type = STACK_TYPE_UNKNOWN;
669 EXPORT_SYMBOL_GPL(__unwind_start);