xref: /openbmc/linux/kernel/debug/kdb/kdb_bt.c (revision fdcdc4c5)
1 /*
2  * Kernel Debugger Architecture Independent Stack Traceback
3  *
4  * This file is subject to the terms and conditions of the GNU General Public
5  * License.  See the file "COPYING" in the main directory of this archive
6  * for more details.
7  *
8  * Copyright (c) 1999-2004 Silicon Graphics, Inc.  All Rights Reserved.
9  * Copyright (c) 2009 Wind River Systems, Inc.  All Rights Reserved.
10  */
11 
12 #include <linux/ctype.h>
13 #include <linux/string.h>
14 #include <linux/kernel.h>
15 #include <linux/sched/signal.h>
16 #include <linux/sched/debug.h>
17 #include <linux/kdb.h>
18 #include <linux/nmi.h>
19 #include "kdb_private.h"
20 
21 
kdb_show_stack(struct task_struct * p,void * addr)22 static void kdb_show_stack(struct task_struct *p, void *addr)
23 {
24 	kdb_trap_printk++;
25 
26 	if (!addr && kdb_task_has_cpu(p)) {
27 		int old_lvl = console_loglevel;
28 
29 		console_loglevel = CONSOLE_LOGLEVEL_MOTORMOUTH;
30 		kdb_dump_stack_on_cpu(kdb_process_cpu(p));
31 		console_loglevel = old_lvl;
32 	} else {
33 		show_stack(p, addr, KERN_EMERG);
34 	}
35 
36 	kdb_trap_printk--;
37 }
38 
39 /*
40  * kdb_bt
41  *
42  *	This function implements the 'bt' command.  Print a stack
43  *	traceback.
44  *
45  *	bt [<address-expression>]	(addr-exp is for alternate stacks)
46  *	btp <pid>			Kernel stack for <pid>
47  *	btt <address-expression>	Kernel stack for task structure at
48  *					<address-expression>
49  *	bta [state_chars>|A]		All useful processes, optionally
50  *					filtered by state
51  *	btc [<cpu>]			The current process on one cpu,
52  *					default is all cpus
53  *
54  *	bt <address-expression> refers to a address on the stack, that location
55  *	is assumed to contain a return address.
56  *
57  *	btt <address-expression> refers to the address of a struct task.
58  *
59  * Inputs:
60  *	argc	argument count
61  *	argv	argument vector
62  * Outputs:
63  *	None.
64  * Returns:
65  *	zero for success, a kdb diagnostic if error
66  * Locking:
67  *	none.
68  * Remarks:
69  *	Backtrack works best when the code uses frame pointers.  But even
70  *	without frame pointers we should get a reasonable trace.
71  *
72  *	mds comes in handy when examining the stack to do a manual traceback or
73  *	to get a starting point for bt <address-expression>.
74  */
75 
76 static int
kdb_bt1(struct task_struct * p,const char * mask,bool btaprompt)77 kdb_bt1(struct task_struct *p, const char *mask, bool btaprompt)
78 {
79 	char ch;
80 
81 	if (kdb_getarea(ch, (unsigned long)p) ||
82 	    kdb_getarea(ch, (unsigned long)(p+1)-1))
83 		return KDB_BADADDR;
84 	if (!kdb_task_state(p, mask))
85 		return 0;
86 	kdb_printf("Stack traceback for pid %d\n", p->pid);
87 	kdb_ps1(p);
88 	kdb_show_stack(p, NULL);
89 	if (btaprompt) {
90 		kdb_printf("Enter <q> to end, <cr> or <space> to continue:");
91 		do {
92 			ch = kdb_getchar();
93 		} while (!strchr("\r\n q", ch));
94 		kdb_printf("\n");
95 
96 		/* reset the pager */
97 		kdb_nextline = 1;
98 
99 		if (ch == 'q')
100 			return 1;
101 	}
102 	touch_nmi_watchdog();
103 	return 0;
104 }
105 
106 static void
kdb_bt_cpu(unsigned long cpu)107 kdb_bt_cpu(unsigned long cpu)
108 {
109 	struct task_struct *kdb_tsk;
110 
111 	if (cpu >= num_possible_cpus() || !cpu_online(cpu)) {
112 		kdb_printf("WARNING: no process for cpu %ld\n", cpu);
113 		return;
114 	}
115 
116 	/* If a CPU failed to round up we could be here */
117 	kdb_tsk = KDB_TSK(cpu);
118 	if (!kdb_tsk) {
119 		kdb_printf("WARNING: no task for cpu %ld\n", cpu);
120 		return;
121 	}
122 
123 	kdb_bt1(kdb_tsk, "A", false);
124 }
125 
126 int
kdb_bt(int argc,const char ** argv)127 kdb_bt(int argc, const char **argv)
128 {
129 	int diag;
130 	int btaprompt = 1;
131 	int nextarg;
132 	unsigned long addr;
133 	long offset;
134 
135 	/* Prompt after each proc in bta */
136 	kdbgetintenv("BTAPROMPT", &btaprompt);
137 
138 	if (strcmp(argv[0], "bta") == 0) {
139 		struct task_struct *g, *p;
140 		unsigned long cpu;
141 		const char *mask = argc ? argv[1] : kdbgetenv("PS");
142 
143 		if (argc == 0)
144 			kdb_ps_suppressed();
145 		/* Run the active tasks first */
146 		for_each_online_cpu(cpu) {
147 			p = kdb_curr_task(cpu);
148 			if (kdb_bt1(p, mask, btaprompt))
149 				return 0;
150 		}
151 		/* Now the inactive tasks */
152 		for_each_process_thread(g, p) {
153 			if (KDB_FLAG(CMD_INTERRUPT))
154 				return 0;
155 			if (task_curr(p))
156 				continue;
157 			if (kdb_bt1(p, mask, btaprompt))
158 				return 0;
159 		}
160 	} else if (strcmp(argv[0], "btp") == 0) {
161 		struct task_struct *p;
162 		unsigned long pid;
163 		if (argc != 1)
164 			return KDB_ARGCOUNT;
165 		diag = kdbgetularg((char *)argv[1], &pid);
166 		if (diag)
167 			return diag;
168 		p = find_task_by_pid_ns(pid, &init_pid_ns);
169 		if (p)
170 			return kdb_bt1(p, "A", false);
171 		kdb_printf("No process with pid == %ld found\n", pid);
172 		return 0;
173 	} else if (strcmp(argv[0], "btt") == 0) {
174 		if (argc != 1)
175 			return KDB_ARGCOUNT;
176 		diag = kdbgetularg((char *)argv[1], &addr);
177 		if (diag)
178 			return diag;
179 		return kdb_bt1((struct task_struct *)addr, "A", false);
180 	} else if (strcmp(argv[0], "btc") == 0) {
181 		unsigned long cpu = ~0;
182 		if (argc > 1)
183 			return KDB_ARGCOUNT;
184 		if (argc == 1) {
185 			diag = kdbgetularg((char *)argv[1], &cpu);
186 			if (diag)
187 				return diag;
188 		}
189 		if (cpu != ~0) {
190 			kdb_bt_cpu(cpu);
191 		} else {
192 			/*
193 			 * Recursive use of kdb_parse, do not use argv after
194 			 * this point.
195 			 */
196 			argv = NULL;
197 			kdb_printf("btc: cpu status: ");
198 			kdb_parse("cpu\n");
199 			for_each_online_cpu(cpu) {
200 				kdb_bt_cpu(cpu);
201 				touch_nmi_watchdog();
202 			}
203 		}
204 		return 0;
205 	} else {
206 		if (argc) {
207 			nextarg = 1;
208 			diag = kdbgetaddrarg(argc, argv, &nextarg, &addr,
209 					     &offset, NULL);
210 			if (diag)
211 				return diag;
212 			kdb_show_stack(kdb_current_task, (void *)addr);
213 			return 0;
214 		} else {
215 			return kdb_bt1(kdb_current_task, "A", false);
216 		}
217 	}
218 
219 	/* NOTREACHED */
220 	return 0;
221 }
222