1 /*
2  * Created by: Jason Wessel <jason.wessel@windriver.com>
3  *
4  * Copyright (c) 2009 Wind River Systems, Inc.  All Rights Reserved.
5  *
6  * This file is licensed under the terms of the GNU General Public
7  * License version 2. This program is licensed "as is" without any
8  * warranty of any kind, whether express or implied.
9  */
10 
11 #include <linux/kgdb.h>
12 #include <linux/kdb.h>
13 #include <linux/kdebug.h>
14 #include <linux/export.h>
15 #include <linux/hardirq.h>
16 #include "kdb_private.h"
17 #include "../debug_core.h"
18 
19 /*
20  * KDB interface to KGDB internals
21  */
22 get_char_func kdb_poll_funcs[] = {
23 	dbg_io_get_char,
24 	NULL,
25 	NULL,
26 	NULL,
27 	NULL,
28 	NULL,
29 };
30 EXPORT_SYMBOL_GPL(kdb_poll_funcs);
31 
32 int kdb_poll_idx = 1;
33 EXPORT_SYMBOL_GPL(kdb_poll_idx);
34 
35 static struct kgdb_state *kdb_ks;
36 
kdb_common_init_state(struct kgdb_state * ks)37 int kdb_common_init_state(struct kgdb_state *ks)
38 {
39 	kdb_initial_cpu = atomic_read(&kgdb_active);
40 	kdb_current_task = kgdb_info[ks->cpu].task;
41 	kdb_current_regs = kgdb_info[ks->cpu].debuggerinfo;
42 	return 0;
43 }
44 
kdb_common_deinit_state(void)45 int kdb_common_deinit_state(void)
46 {
47 	kdb_initial_cpu = -1;
48 	kdb_current_task = NULL;
49 	kdb_current_regs = NULL;
50 	return 0;
51 }
52 
kdb_stub(struct kgdb_state * ks)53 int kdb_stub(struct kgdb_state *ks)
54 {
55 	int error = 0;
56 	kdb_bp_t *bp;
57 	unsigned long addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
58 	kdb_reason_t reason = KDB_REASON_OOPS;
59 	kdb_dbtrap_t db_result = KDB_DB_NOBPT;
60 	int i;
61 
62 	kdb_ks = ks;
63 	if (KDB_STATE(REENTRY)) {
64 		reason = KDB_REASON_SWITCH;
65 		KDB_STATE_CLEAR(REENTRY);
66 		addr = instruction_pointer(ks->linux_regs);
67 	}
68 	ks->pass_exception = 0;
69 	if (atomic_read(&kgdb_setting_breakpoint))
70 		reason = KDB_REASON_KEYBOARD;
71 
72 	if (ks->err_code == KDB_REASON_SYSTEM_NMI && ks->signo == SIGTRAP)
73 		reason = KDB_REASON_SYSTEM_NMI;
74 
75 	else if (in_nmi())
76 		reason = KDB_REASON_NMI;
77 
78 	for (i = 0, bp = kdb_breakpoints; i < KDB_MAXBPT; i++, bp++) {
79 		if ((bp->bp_enabled) && (bp->bp_addr == addr)) {
80 			reason = KDB_REASON_BREAK;
81 			db_result = KDB_DB_BPT;
82 			if (addr != instruction_pointer(ks->linux_regs))
83 				kgdb_arch_set_pc(ks->linux_regs, addr);
84 			break;
85 		}
86 	}
87 	if (reason == KDB_REASON_BREAK || reason == KDB_REASON_SWITCH) {
88 		for (i = 0, bp = kdb_breakpoints; i < KDB_MAXBPT; i++, bp++) {
89 			if (bp->bp_free)
90 				continue;
91 			if (bp->bp_addr == addr) {
92 				bp->bp_delay = 1;
93 				bp->bp_delayed = 1;
94 	/*
95 	 * SSBPT is set when the kernel debugger must single step a
96 	 * task in order to re-establish an instruction breakpoint
97 	 * which uses the instruction replacement mechanism.  It is
98 	 * cleared by any action that removes the need to single-step
99 	 * the breakpoint.
100 	 */
101 				reason = KDB_REASON_BREAK;
102 				db_result = KDB_DB_BPT;
103 				KDB_STATE_SET(SSBPT);
104 				break;
105 			}
106 		}
107 	}
108 
109 	if (reason != KDB_REASON_BREAK && ks->ex_vector == 0 &&
110 		ks->signo == SIGTRAP) {
111 		reason = KDB_REASON_SSTEP;
112 		db_result = KDB_DB_BPT;
113 	}
114 	/* Set initial kdb state variables */
115 	KDB_STATE_CLEAR(KGDB_TRANS);
116 	kdb_common_init_state(ks);
117 	/* Remove any breakpoints as needed by kdb and clear single step */
118 	kdb_bp_remove();
119 	KDB_STATE_CLEAR(DOING_SS);
120 	KDB_STATE_SET(PAGER);
121 	if (ks->err_code == DIE_OOPS || reason == KDB_REASON_OOPS) {
122 		ks->pass_exception = 1;
123 		KDB_FLAG_SET(CATASTROPHIC);
124 	}
125 	/* set CATASTROPHIC if the system contains unresponsive processors */
126 	for_each_online_cpu(i)
127 		if (!kgdb_info[i].enter_kgdb)
128 			KDB_FLAG_SET(CATASTROPHIC);
129 	if (KDB_STATE(SSBPT) && reason == KDB_REASON_SSTEP) {
130 		KDB_STATE_CLEAR(SSBPT);
131 		KDB_STATE_CLEAR(DOING_SS);
132 	} else {
133 		/* Start kdb main loop */
134 		error = kdb_main_loop(KDB_REASON_ENTER, reason,
135 				      ks->err_code, db_result, ks->linux_regs);
136 	}
137 	/*
138 	 * Upon exit from the kdb main loop setup break points and restart
139 	 * the system based on the requested continue state
140 	 */
141 	kdb_common_deinit_state();
142 	KDB_STATE_CLEAR(PAGER);
143 	if (error == KDB_CMD_KGDB) {
144 		if (KDB_STATE(DOING_KGDB))
145 			KDB_STATE_CLEAR(DOING_KGDB);
146 		return DBG_PASS_EVENT;
147 	}
148 	kdb_bp_install(ks->linux_regs);
149 	/* Set the exit state to a single step or a continue */
150 	if (KDB_STATE(DOING_SS))
151 		gdbstub_state(ks, "s");
152 	else
153 		gdbstub_state(ks, "c");
154 
155 	KDB_FLAG_CLEAR(CATASTROPHIC);
156 
157 	/* Invoke arch specific exception handling prior to system resume */
158 	kgdb_info[ks->cpu].ret_state = gdbstub_state(ks, "e");
159 	if (ks->pass_exception)
160 		kgdb_info[ks->cpu].ret_state = 1;
161 	if (error == KDB_CMD_CPU) {
162 		KDB_STATE_SET(REENTRY);
163 		/*
164 		 * Force clear the single step bit because kdb emulates this
165 		 * differently vs the gdbstub
166 		 */
167 		kgdb_single_step = 0;
168 		return DBG_SWITCH_CPU_EVENT;
169 	}
170 	return kgdb_info[ks->cpu].ret_state;
171 }
172 
kdb_gdb_state_pass(char * buf)173 void kdb_gdb_state_pass(char *buf)
174 {
175 	gdbstub_state(kdb_ks, buf);
176 }
177