xref: /openbmc/linux/arch/arc/kernel/kgdb.c (revision 58d9ceb7)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * kgdb support for ARC
4  *
5  * Copyright (C) 2012 Synopsys, Inc. (www.synopsys.com)
6  */
7 
8 #include <linux/kgdb.h>
9 #include <linux/sched.h>
10 #include <linux/sched/task_stack.h>
11 #include <asm/disasm.h>
12 #include <asm/cacheflush.h>
13 
to_gdb_regs(unsigned long * gdb_regs,struct pt_regs * kernel_regs,struct callee_regs * cregs)14 static void to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *kernel_regs,
15 			struct callee_regs *cregs)
16 {
17 	int regno;
18 
19 	for (regno = 0; regno <= 26; regno++)
20 		gdb_regs[_R0 + regno] = get_reg(regno, kernel_regs, cregs);
21 
22 	for (regno = 27; regno < GDB_MAX_REGS; regno++)
23 		gdb_regs[regno] = 0;
24 
25 	gdb_regs[_FP]		= kernel_regs->fp;
26 	gdb_regs[__SP]		= kernel_regs->sp;
27 	gdb_regs[_BLINK]	= kernel_regs->blink;
28 	gdb_regs[_RET]		= kernel_regs->ret;
29 	gdb_regs[_STATUS32]	= kernel_regs->status32;
30 	gdb_regs[_LP_COUNT]	= kernel_regs->lp_count;
31 	gdb_regs[_LP_END]	= kernel_regs->lp_end;
32 	gdb_regs[_LP_START]	= kernel_regs->lp_start;
33 	gdb_regs[_BTA]		= kernel_regs->bta;
34 	gdb_regs[_STOP_PC]	= kernel_regs->ret;
35 }
36 
from_gdb_regs(unsigned long * gdb_regs,struct pt_regs * kernel_regs,struct callee_regs * cregs)37 static void from_gdb_regs(unsigned long *gdb_regs, struct pt_regs *kernel_regs,
38 			struct callee_regs *cregs)
39 {
40 	int regno;
41 
42 	for (regno = 0; regno <= 26; regno++)
43 		set_reg(regno, gdb_regs[regno + _R0], kernel_regs, cregs);
44 
45 	kernel_regs->fp		= gdb_regs[_FP];
46 	kernel_regs->sp		= gdb_regs[__SP];
47 	kernel_regs->blink	= gdb_regs[_BLINK];
48 	kernel_regs->ret	= gdb_regs[_RET];
49 	kernel_regs->status32	= gdb_regs[_STATUS32];
50 	kernel_regs->lp_count	= gdb_regs[_LP_COUNT];
51 	kernel_regs->lp_end	= gdb_regs[_LP_END];
52 	kernel_regs->lp_start	= gdb_regs[_LP_START];
53 	kernel_regs->bta	= gdb_regs[_BTA];
54 }
55 
56 
pt_regs_to_gdb_regs(unsigned long * gdb_regs,struct pt_regs * kernel_regs)57 void pt_regs_to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *kernel_regs)
58 {
59 	to_gdb_regs(gdb_regs, kernel_regs, (struct callee_regs *)
60 		current->thread.callee_reg);
61 }
62 
gdb_regs_to_pt_regs(unsigned long * gdb_regs,struct pt_regs * kernel_regs)63 void gdb_regs_to_pt_regs(unsigned long *gdb_regs, struct pt_regs *kernel_regs)
64 {
65 	from_gdb_regs(gdb_regs, kernel_regs, (struct callee_regs *)
66 		current->thread.callee_reg);
67 }
68 
sleeping_thread_to_gdb_regs(unsigned long * gdb_regs,struct task_struct * task)69 void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs,
70 				 struct task_struct *task)
71 {
72 	if (task)
73 		to_gdb_regs(gdb_regs, task_pt_regs(task),
74 			(struct callee_regs *) task->thread.callee_reg);
75 }
76 
77 struct single_step_data_t {
78 	uint16_t opcode[2];
79 	unsigned long address[2];
80 	int is_branch;
81 	int armed;
82 } single_step_data;
83 
undo_single_step(struct pt_regs * regs)84 static void undo_single_step(struct pt_regs *regs)
85 {
86 	if (single_step_data.armed) {
87 		int i;
88 
89 		for (i = 0; i < (single_step_data.is_branch ? 2 : 1); i++) {
90 			memcpy((void *) single_step_data.address[i],
91 				&single_step_data.opcode[i],
92 				BREAK_INSTR_SIZE);
93 
94 			flush_icache_range(single_step_data.address[i],
95 				single_step_data.address[i] +
96 				BREAK_INSTR_SIZE);
97 		}
98 		single_step_data.armed = 0;
99 	}
100 }
101 
place_trap(unsigned long address,void * save)102 static void place_trap(unsigned long address, void *save)
103 {
104 	memcpy(save, (void *) address, BREAK_INSTR_SIZE);
105 	memcpy((void *) address, &arch_kgdb_ops.gdb_bpt_instr,
106 		BREAK_INSTR_SIZE);
107 	flush_icache_range(address, address + BREAK_INSTR_SIZE);
108 }
109 
do_single_step(struct pt_regs * regs)110 static void do_single_step(struct pt_regs *regs)
111 {
112 	single_step_data.is_branch = disasm_next_pc((unsigned long)
113 		regs->ret, regs, (struct callee_regs *)
114 		current->thread.callee_reg,
115 		&single_step_data.address[0],
116 		&single_step_data.address[1]);
117 
118 	place_trap(single_step_data.address[0], &single_step_data.opcode[0]);
119 
120 	if (single_step_data.is_branch) {
121 		place_trap(single_step_data.address[1],
122 			&single_step_data.opcode[1]);
123 	}
124 
125 	single_step_data.armed++;
126 }
127 
kgdb_arch_handle_exception(int e_vector,int signo,int err_code,char * remcomInBuffer,char * remcomOutBuffer,struct pt_regs * regs)128 int kgdb_arch_handle_exception(int e_vector, int signo, int err_code,
129 			       char *remcomInBuffer, char *remcomOutBuffer,
130 			       struct pt_regs *regs)
131 {
132 	unsigned long addr;
133 	char *ptr;
134 
135 	undo_single_step(regs);
136 
137 	switch (remcomInBuffer[0]) {
138 	case 's':
139 	case 'c':
140 		ptr = &remcomInBuffer[1];
141 		if (kgdb_hex2long(&ptr, &addr))
142 			regs->ret = addr;
143 		fallthrough;
144 
145 	case 'D':
146 	case 'k':
147 		atomic_set(&kgdb_cpu_doing_single_step, -1);
148 
149 		if (remcomInBuffer[0] == 's') {
150 			do_single_step(regs);
151 			atomic_set(&kgdb_cpu_doing_single_step,
152 				   smp_processor_id());
153 		}
154 
155 		return 0;
156 	}
157 	return -1;
158 }
159 
kgdb_arch_init(void)160 int kgdb_arch_init(void)
161 {
162 	single_step_data.armed = 0;
163 	return 0;
164 }
165 
kgdb_trap(struct pt_regs * regs)166 void kgdb_trap(struct pt_regs *regs)
167 {
168 	/* trap_s 3 is used for breakpoints that overwrite existing
169 	 * instructions, while trap_s 4 is used for compiled breakpoints.
170 	 *
171 	 * with trap_s 3 breakpoints the original instruction needs to be
172 	 * restored and continuation needs to start at the location of the
173 	 * breakpoint.
174 	 *
175 	 * with trap_s 4 (compiled) breakpoints, continuation needs to
176 	 * start after the breakpoint.
177 	 */
178 	if (regs->ecr.param == 3)
179 		instruction_pointer(regs) -= BREAK_INSTR_SIZE;
180 
181 	kgdb_handle_exception(1, SIGTRAP, 0, regs);
182 }
183 
kgdb_arch_exit(void)184 void kgdb_arch_exit(void)
185 {
186 }
187 
kgdb_arch_set_pc(struct pt_regs * regs,unsigned long ip)188 void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long ip)
189 {
190 	instruction_pointer(regs) = ip;
191 }
192 
kgdb_call_nmi_hook(void * ignored)193 void kgdb_call_nmi_hook(void *ignored)
194 {
195 	/* Default implementation passes get_irq_regs() but we don't */
196 	kgdb_nmicallback(raw_smp_processor_id(), NULL);
197 }
198 
199 const struct kgdb_arch arch_kgdb_ops = {
200 	/* breakpoint instruction: TRAP_S 0x3 */
201 #ifdef CONFIG_CPU_BIG_ENDIAN
202 	.gdb_bpt_instr		= {0x78, 0x7e},
203 #else
204 	.gdb_bpt_instr		= {0x7e, 0x78},
205 #endif
206 };
207