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
22static 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
76static int
77kdb_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
106static void
107kdb_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
126int
127kdb_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