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1/*
2 * Stack tracing support
3 *
4 * Copyright (C) 2012 ARM Ltd.
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program. If not, see <http://www.gnu.org/licenses/>.
17 */
18#include <linux/kernel.h>
19#include <linux/export.h>
20#include <linux/ftrace.h>
21#include <linux/sched.h>
22#include <linux/sched/debug.h>
23#include <linux/sched/task_stack.h>
24#include <linux/stacktrace.h>
25
26#include <asm/irq.h>
27#include <asm/stack_pointer.h>
28#include <asm/stacktrace.h>
29
30/*
31 * AArch64 PCS assigns the frame pointer to x29.
32 *
33 * A simple function prologue looks like this:
34 * sub sp, sp, #0x10
35 * stp x29, x30, [sp]
36 * mov x29, sp
37 *
38 * A simple function epilogue looks like this:
39 * mov sp, x29
40 * ldp x29, x30, [sp]
41 * add sp, sp, #0x10
42 */
43int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
44{
45 unsigned long fp = frame->fp;
46
47 if (fp & 0xf)
48 return -EINVAL;
49
50 if (!tsk)
51 tsk = current;
52
53 if (!on_accessible_stack(tsk, fp))
54 return -EINVAL;
55
56 frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));
57 frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8));
58
59#ifdef CONFIG_FUNCTION_GRAPH_TRACER
60 if (tsk->ret_stack &&
61 (frame->pc == (unsigned long)return_to_handler)) {
62 if (WARN_ON_ONCE(frame->graph == -1))
63 return -EINVAL;
64 if (frame->graph < -1)
65 frame->graph += FTRACE_NOTRACE_DEPTH;
66
67 /*
68 * This is a case where function graph tracer has
69 * modified a return address (LR) in a stack frame
70 * to hook a function return.
71 * So replace it to an original value.
72 */
73 frame->pc = tsk->ret_stack[frame->graph--].ret;
74 }
75#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
76
77 /*
78 * Frames created upon entry from EL0 have NULL FP and PC values, so
79 * don't bother reporting these. Frames created by __noreturn functions
80 * might have a valid FP even if PC is bogus, so only terminate where
81 * both are NULL.
82 */
83 if (!frame->fp && !frame->pc)
84 return -EINVAL;
85
86 return 0;
87}
88
89void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
90 int (*fn)(struct stackframe *, void *), void *data)
91{
92 while (1) {
93 int ret;
94
95 if (fn(frame, data))
96 break;
97 ret = unwind_frame(tsk, frame);
98 if (ret < 0)
99 break;
100 }
101}
102
103#ifdef CONFIG_STACKTRACE
104struct stack_trace_data {
105 struct stack_trace *trace;
106 unsigned int no_sched_functions;
107 unsigned int skip;
108};
109
110static int save_trace(struct stackframe *frame, void *d)
111{
112 struct stack_trace_data *data = d;
113 struct stack_trace *trace = data->trace;
114 unsigned long addr = frame->pc;
115
116 if (data->no_sched_functions && in_sched_functions(addr))
117 return 0;
118 if (data->skip) {
119 data->skip--;
120 return 0;
121 }
122
123 trace->entries[trace->nr_entries++] = addr;
124
125 return trace->nr_entries >= trace->max_entries;
126}
127
128void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
129{
130 struct stack_trace_data data;
131 struct stackframe frame;
132
133 data.trace = trace;
134 data.skip = trace->skip;
135 data.no_sched_functions = 0;
136
137 frame.fp = regs->regs[29];
138 frame.pc = regs->pc;
139#ifdef CONFIG_FUNCTION_GRAPH_TRACER
140 frame.graph = current->curr_ret_stack;
141#endif
142
143 walk_stackframe(current, &frame, save_trace, &data);
144 if (trace->nr_entries < trace->max_entries)
145 trace->entries[trace->nr_entries++] = ULONG_MAX;
146}
147
148static noinline void __save_stack_trace(struct task_struct *tsk,
149 struct stack_trace *trace, unsigned int nosched)
150{
151 struct stack_trace_data data;
152 struct stackframe frame;
153
154 if (!try_get_task_stack(tsk))
155 return;
156
157 data.trace = trace;
158 data.skip = trace->skip;
159 data.no_sched_functions = nosched;
160
161 if (tsk != current) {
162 frame.fp = thread_saved_fp(tsk);
163 frame.pc = thread_saved_pc(tsk);
164 } else {
165 /* We don't want this function nor the caller */
166 data.skip += 2;
167 frame.fp = (unsigned long)__builtin_frame_address(0);
168 frame.pc = (unsigned long)__save_stack_trace;
169 }
170#ifdef CONFIG_FUNCTION_GRAPH_TRACER
171 frame.graph = tsk->curr_ret_stack;
172#endif
173
174 walk_stackframe(tsk, &frame, save_trace, &data);
175 if (trace->nr_entries < trace->max_entries)
176 trace->entries[trace->nr_entries++] = ULONG_MAX;
177
178 put_task_stack(tsk);
179}
180EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
181
182void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
183{
184 __save_stack_trace(tsk, trace, 1);
185}
186
187void save_stack_trace(struct stack_trace *trace)
188{
189 __save_stack_trace(current, trace, 0);
190}
191
192EXPORT_SYMBOL_GPL(save_stack_trace);
193#endif
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/export.h>
9#include <linux/ftrace.h>
10#include <linux/kprobes.h>
11#include <linux/sched.h>
12#include <linux/sched/debug.h>
13#include <linux/sched/task_stack.h>
14#include <linux/stacktrace.h>
15
16#include <asm/irq.h>
17#include <asm/pointer_auth.h>
18#include <asm/stack_pointer.h>
19#include <asm/stacktrace.h>
20
21/*
22 * AArch64 PCS assigns the frame pointer to x29.
23 *
24 * A simple function prologue looks like this:
25 * sub sp, sp, #0x10
26 * stp x29, x30, [sp]
27 * mov x29, sp
28 *
29 * A simple function epilogue looks like this:
30 * mov sp, x29
31 * ldp x29, x30, [sp]
32 * add sp, sp, #0x10
33 */
34
35/*
36 * Unwind from one frame record (A) to the next frame record (B).
37 *
38 * We terminate early if the location of B indicates a malformed chain of frame
39 * records (e.g. a cycle), determined based on the location and fp value of A
40 * and the location (but not the fp value) of B.
41 */
42int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
43{
44 unsigned long fp = frame->fp;
45 struct stack_info info;
46
47 if (fp & 0xf)
48 return -EINVAL;
49
50 if (!tsk)
51 tsk = current;
52
53 if (!on_accessible_stack(tsk, fp, &info))
54 return -EINVAL;
55
56 if (test_bit(info.type, frame->stacks_done))
57 return -EINVAL;
58
59 /*
60 * As stacks grow downward, any valid record on the same stack must be
61 * at a strictly higher address than the prior record.
62 *
63 * Stacks can nest in several valid orders, e.g.
64 *
65 * TASK -> IRQ -> OVERFLOW -> SDEI_NORMAL
66 * TASK -> SDEI_NORMAL -> SDEI_CRITICAL -> OVERFLOW
67 *
68 * ... but the nesting itself is strict. Once we transition from one
69 * stack to another, it's never valid to unwind back to that first
70 * stack.
71 */
72 if (info.type == frame->prev_type) {
73 if (fp <= frame->prev_fp)
74 return -EINVAL;
75 } else {
76 set_bit(frame->prev_type, frame->stacks_done);
77 }
78
79 /*
80 * Record this frame record's values and location. The prev_fp and
81 * prev_type are only meaningful to the next unwind_frame() invocation.
82 */
83 frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));
84 frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8));
85 frame->prev_fp = fp;
86 frame->prev_type = info.type;
87
88#ifdef CONFIG_FUNCTION_GRAPH_TRACER
89 if (tsk->ret_stack &&
90 (ptrauth_strip_insn_pac(frame->pc) == (unsigned long)return_to_handler)) {
91 struct ftrace_ret_stack *ret_stack;
92 /*
93 * This is a case where function graph tracer has
94 * modified a return address (LR) in a stack frame
95 * to hook a function return.
96 * So replace it to an original value.
97 */
98 ret_stack = ftrace_graph_get_ret_stack(tsk, frame->graph++);
99 if (WARN_ON_ONCE(!ret_stack))
100 return -EINVAL;
101 frame->pc = ret_stack->ret;
102 }
103#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
104
105 frame->pc = ptrauth_strip_insn_pac(frame->pc);
106
107 /*
108 * Frames created upon entry from EL0 have NULL FP and PC values, so
109 * don't bother reporting these. Frames created by __noreturn functions
110 * might have a valid FP even if PC is bogus, so only terminate where
111 * both are NULL.
112 */
113 if (!frame->fp && !frame->pc)
114 return -EINVAL;
115
116 return 0;
117}
118NOKPROBE_SYMBOL(unwind_frame);
119
120void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
121 int (*fn)(struct stackframe *, void *), void *data)
122{
123 while (1) {
124 int ret;
125
126 if (fn(frame, data))
127 break;
128 ret = unwind_frame(tsk, frame);
129 if (ret < 0)
130 break;
131 }
132}
133NOKPROBE_SYMBOL(walk_stackframe);
134
135#ifdef CONFIG_STACKTRACE
136struct stack_trace_data {
137 struct stack_trace *trace;
138 unsigned int no_sched_functions;
139 unsigned int skip;
140};
141
142static int save_trace(struct stackframe *frame, void *d)
143{
144 struct stack_trace_data *data = d;
145 struct stack_trace *trace = data->trace;
146 unsigned long addr = frame->pc;
147
148 if (data->no_sched_functions && in_sched_functions(addr))
149 return 0;
150 if (data->skip) {
151 data->skip--;
152 return 0;
153 }
154
155 trace->entries[trace->nr_entries++] = addr;
156
157 return trace->nr_entries >= trace->max_entries;
158}
159
160void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
161{
162 struct stack_trace_data data;
163 struct stackframe frame;
164
165 data.trace = trace;
166 data.skip = trace->skip;
167 data.no_sched_functions = 0;
168
169 start_backtrace(&frame, regs->regs[29], regs->pc);
170 walk_stackframe(current, &frame, save_trace, &data);
171}
172EXPORT_SYMBOL_GPL(save_stack_trace_regs);
173
174static noinline void __save_stack_trace(struct task_struct *tsk,
175 struct stack_trace *trace, unsigned int nosched)
176{
177 struct stack_trace_data data;
178 struct stackframe frame;
179
180 if (!try_get_task_stack(tsk))
181 return;
182
183 data.trace = trace;
184 data.skip = trace->skip;
185 data.no_sched_functions = nosched;
186
187 if (tsk != current) {
188 start_backtrace(&frame, thread_saved_fp(tsk),
189 thread_saved_pc(tsk));
190 } else {
191 /* We don't want this function nor the caller */
192 data.skip += 2;
193 start_backtrace(&frame,
194 (unsigned long)__builtin_frame_address(0),
195 (unsigned long)__save_stack_trace);
196 }
197
198 walk_stackframe(tsk, &frame, save_trace, &data);
199
200 put_task_stack(tsk);
201}
202
203void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
204{
205 __save_stack_trace(tsk, trace, 1);
206}
207EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
208
209void save_stack_trace(struct stack_trace *trace)
210{
211 __save_stack_trace(current, trace, 0);
212}
213
214EXPORT_SYMBOL_GPL(save_stack_trace);
215#endif