1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Stack tracing support
4 *
5 * Copyright (C) 2012 ARM Ltd.
6 */
7#include <linux/kernel.h>
8#include <linux/efi.h>
9#include <linux/export.h>
10#include <linux/filter.h>
11#include <linux/ftrace.h>
12#include <linux/kprobes.h>
13#include <linux/sched.h>
14#include <linux/sched/debug.h>
15#include <linux/sched/task_stack.h>
16#include <linux/stacktrace.h>
17
18#include <asm/efi.h>
19#include <asm/irq.h>
20#include <asm/stack_pointer.h>
21#include <asm/stacktrace.h>
22
23/*
24 * Kernel unwind state
25 *
26 * @common: Common unwind state.
27 * @task: The task being unwound.
28 * @kr_cur: When KRETPROBES is selected, holds the kretprobe instance
29 * associated with the most recently encountered replacement lr
30 * value.
31 */
32struct kunwind_state {
33 struct unwind_state common;
34 struct task_struct *task;
35#ifdef CONFIG_KRETPROBES
36 struct llist_node *kr_cur;
37#endif
38};
39
40static __always_inline void
41kunwind_init(struct kunwind_state *state,
42 struct task_struct *task)
43{
44 unwind_init_common(&state->common);
45 state->task = task;
46}
47
48/*
49 * Start an unwind from a pt_regs.
50 *
51 * The unwind will begin at the PC within the regs.
52 *
53 * The regs must be on a stack currently owned by the calling task.
54 */
55static __always_inline void
56kunwind_init_from_regs(struct kunwind_state *state,
57 struct pt_regs *regs)
58{
59 kunwind_init(state, current);
60
61 state->common.fp = regs->regs[29];
62 state->common.pc = regs->pc;
63}
64
65/*
66 * Start an unwind from a caller.
67 *
68 * The unwind will begin at the caller of whichever function this is inlined
69 * into.
70 *
71 * The function which invokes this must be noinline.
72 */
73static __always_inline void
74kunwind_init_from_caller(struct kunwind_state *state)
75{
76 kunwind_init(state, current);
77
78 state->common.fp = (unsigned long)__builtin_frame_address(1);
79 state->common.pc = (unsigned long)__builtin_return_address(0);
80}
81
82/*
83 * Start an unwind from a blocked task.
84 *
85 * The unwind will begin at the blocked tasks saved PC (i.e. the caller of
86 * cpu_switch_to()).
87 *
88 * The caller should ensure the task is blocked in cpu_switch_to() for the
89 * duration of the unwind, or the unwind will be bogus. It is never valid to
90 * call this for the current task.
91 */
92static __always_inline void
93kunwind_init_from_task(struct kunwind_state *state,
94 struct task_struct *task)
95{
96 kunwind_init(state, task);
97
98 state->common.fp = thread_saved_fp(task);
99 state->common.pc = thread_saved_pc(task);
100}
101
102static __always_inline int
103kunwind_recover_return_address(struct kunwind_state *state)
104{
105#ifdef CONFIG_FUNCTION_GRAPH_TRACER
106 if (state->task->ret_stack &&
107 (state->common.pc == (unsigned long)return_to_handler)) {
108 unsigned long orig_pc;
109 orig_pc = ftrace_graph_ret_addr(task: state->task, NULL,
110 ret: state->common.pc,
111 retp: (void *)state->common.fp);
112 if (WARN_ON_ONCE(state->common.pc == orig_pc))
113 return -EINVAL;
114 state->common.pc = orig_pc;
115 }
116#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
117
118#ifdef CONFIG_KRETPROBES
119 if (is_kretprobe_trampoline(addr: state->common.pc)) {
120 unsigned long orig_pc;
121 orig_pc = kretprobe_find_ret_addr(tsk: state->task,
122 fp: (void *)state->common.fp,
123 cur: &state->kr_cur);
124 state->common.pc = orig_pc;
125 }
126#endif /* CONFIG_KRETPROBES */
127
128 return 0;
129}
130
131/*
132 * Unwind from one frame record (A) to the next frame record (B).
133 *
134 * We terminate early if the location of B indicates a malformed chain of frame
135 * records (e.g. a cycle), determined based on the location and fp value of A
136 * and the location (but not the fp value) of B.
137 */
138static __always_inline int
139kunwind_next(struct kunwind_state *state)
140{
141 struct task_struct *tsk = state->task;
142 unsigned long fp = state->common.fp;
143 int err;
144
145 /* Final frame; nothing to unwind */
146 if (fp == (unsigned long)task_pt_regs(tsk)->stackframe)
147 return -ENOENT;
148
149 err = unwind_next_frame_record(&state->common);
150 if (err)
151 return err;
152
153 state->common.pc = ptrauth_strip_kernel_insn_pac(state->common.pc);
154
155 return kunwind_recover_return_address(state);
156}
157
158typedef bool (*kunwind_consume_fn)(const struct kunwind_state *state, void *cookie);
159
160static __always_inline void
161do_kunwind(struct kunwind_state *state, kunwind_consume_fn consume_state,
162 void *cookie)
163{
164 if (kunwind_recover_return_address(state))
165 return;
166
167 while (1) {
168 int ret;
169
170 if (!consume_state(state, cookie))
171 break;
172 ret = kunwind_next(state);
173 if (ret < 0)
174 break;
175 }
176}
177
178/*
179 * Per-cpu stacks are only accessible when unwinding the current task in a
180 * non-preemptible context.
181 */
182#define STACKINFO_CPU(name) \
183 ({ \
184 ((task == current) && !preemptible()) \
185 ? stackinfo_get_##name() \
186 : stackinfo_get_unknown(); \
187 })
188
189/*
190 * SDEI stacks are only accessible when unwinding the current task in an NMI
191 * context.
192 */
193#define STACKINFO_SDEI(name) \
194 ({ \
195 ((task == current) && in_nmi()) \
196 ? stackinfo_get_sdei_##name() \
197 : stackinfo_get_unknown(); \
198 })
199
200#define STACKINFO_EFI \
201 ({ \
202 ((task == current) && current_in_efi()) \
203 ? stackinfo_get_efi() \
204 : stackinfo_get_unknown(); \
205 })
206
207static __always_inline void
208kunwind_stack_walk(kunwind_consume_fn consume_state,
209 void *cookie, struct task_struct *task,
210 struct pt_regs *regs)
211{
212 struct stack_info stacks[] = {
213 stackinfo_get_task(task),
214 STACKINFO_CPU(irq),
215#if defined(CONFIG_VMAP_STACK)
216 STACKINFO_CPU(overflow),
217#endif
218#if defined(CONFIG_VMAP_STACK) && defined(CONFIG_ARM_SDE_INTERFACE)
219 STACKINFO_SDEI(normal),
220 STACKINFO_SDEI(critical),
221#endif
222#ifdef CONFIG_EFI
223 STACKINFO_EFI,
224#endif
225 };
226 struct kunwind_state state = {
227 .common = {
228 .stacks = stacks,
229 .nr_stacks = ARRAY_SIZE(stacks),
230 },
231 };
232
233 if (regs) {
234 if (task != current)
235 return;
236 kunwind_init_from_regs(state: &state, regs);
237 } else if (task == current) {
238 kunwind_init_from_caller(state: &state);
239 } else {
240 kunwind_init_from_task(state: &state, task);
241 }
242
243 do_kunwind(state: &state, consume_state, cookie);
244}
245
246struct kunwind_consume_entry_data {
247 stack_trace_consume_fn consume_entry;
248 void *cookie;
249};
250
251static __always_inline bool
252arch_kunwind_consume_entry(const struct kunwind_state *state, void *cookie)
253{
254 struct kunwind_consume_entry_data *data = cookie;
255 return data->consume_entry(data->cookie, state->common.pc);
256}
257
258noinline noinstr void arch_stack_walk(stack_trace_consume_fn consume_entry,
259 void *cookie, struct task_struct *task,
260 struct pt_regs *regs)
261{
262 struct kunwind_consume_entry_data data = {
263 .consume_entry = consume_entry,
264 .cookie = cookie,
265 };
266
267 kunwind_stack_walk(consume_state: arch_kunwind_consume_entry, cookie: &data, task, regs);
268}
269
270struct bpf_unwind_consume_entry_data {
271 bool (*consume_entry)(void *cookie, u64 ip, u64 sp, u64 fp);
272 void *cookie;
273};
274
275static bool
276arch_bpf_unwind_consume_entry(const struct kunwind_state *state, void *cookie)
277{
278 struct bpf_unwind_consume_entry_data *data = cookie;
279
280 return data->consume_entry(data->cookie, state->common.pc, 0,
281 state->common.fp);
282}
283
284noinline noinstr void arch_bpf_stack_walk(bool (*consume_entry)(void *cookie, u64 ip, u64 sp,
285 u64 fp), void *cookie)
286{
287 struct bpf_unwind_consume_entry_data data = {
288 .consume_entry = consume_entry,
289 .cookie = cookie,
290 };
291
292 kunwind_stack_walk(consume_state: arch_bpf_unwind_consume_entry, cookie: &data, current, NULL);
293}
294
295static bool dump_backtrace_entry(void *arg, unsigned long where)
296{
297 char *loglvl = arg;
298 printk("%s %pSb\n", loglvl, (void *)where);
299 return true;
300}
301
302void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,
303 const char *loglvl)
304{
305 pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
306
307 if (regs && user_mode(regs))
308 return;
309
310 if (!tsk)
311 tsk = current;
312
313 if (!try_get_task_stack(tsk))
314 return;
315
316 printk("%sCall trace:\n", loglvl);
317 arch_stack_walk(consume_entry: dump_backtrace_entry, cookie: (void *)loglvl, task: tsk, regs);
318
319 put_task_stack(tsk);
320}
321
322void show_stack(struct task_struct *tsk, unsigned long *sp, const char *loglvl)
323{
324 dump_backtrace(NULL, tsk, loglvl);
325 barrier();
326}
327

source code of linux/arch/arm64/kernel/stacktrace.c