1/*
  2 * kgdb support for ARC
  3 *
  4 * Copyright (C) 2012 Synopsys, Inc. (www.synopsys.com)
  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
 11#include <linux/kgdb.h>
 12#include <linux/sched.h>
 13#include <linux/sched/task_stack.h>
 14#include <asm/disasm.h>
 15#include <asm/cacheflush.h>
 16
 17static void to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *kernel_regs,
 18			struct callee_regs *cregs)
 19{
 20	int regno;
 21
 22	for (regno = 0; regno <= 26; regno++)
 23		gdb_regs[_R0 + regno] = get_reg(regno, kernel_regs, cregs);
 24
 25	for (regno = 27; regno < GDB_MAX_REGS; regno++)
 26		gdb_regs[regno] = 0;
 27
 28	gdb_regs[_FP]		= kernel_regs->fp;
 29	gdb_regs[__SP]		= kernel_regs->sp;
 30	gdb_regs[_BLINK]	= kernel_regs->blink;
 31	gdb_regs[_RET]		= kernel_regs->ret;
 32	gdb_regs[_STATUS32]	= kernel_regs->status32;
 33	gdb_regs[_LP_COUNT]	= kernel_regs->lp_count;
 34	gdb_regs[_LP_END]	= kernel_regs->lp_end;
 35	gdb_regs[_LP_START]	= kernel_regs->lp_start;
 36	gdb_regs[_BTA]		= kernel_regs->bta;
 37	gdb_regs[_STOP_PC]	= kernel_regs->ret;
 38}
 39
 40static void from_gdb_regs(unsigned long *gdb_regs, struct pt_regs *kernel_regs,
 41			struct callee_regs *cregs)
 42{
 43	int regno;
 44
 45	for (regno = 0; regno <= 26; regno++)
 46		set_reg(regno, gdb_regs[regno + _R0], kernel_regs, cregs);
 47
 48	kernel_regs->fp		= gdb_regs[_FP];
 49	kernel_regs->sp		= gdb_regs[__SP];
 50	kernel_regs->blink	= gdb_regs[_BLINK];
 51	kernel_regs->ret	= gdb_regs[_RET];
 52	kernel_regs->status32	= gdb_regs[_STATUS32];
 53	kernel_regs->lp_count	= gdb_regs[_LP_COUNT];
 54	kernel_regs->lp_end	= gdb_regs[_LP_END];
 55	kernel_regs->lp_start	= gdb_regs[_LP_START];
 56	kernel_regs->bta	= gdb_regs[_BTA];
 57}
 58
 59
 60void pt_regs_to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *kernel_regs)
 61{
 62	to_gdb_regs(gdb_regs, kernel_regs, (struct callee_regs *)
 63		current->thread.callee_reg);
 64}
 65
 66void gdb_regs_to_pt_regs(unsigned long *gdb_regs, struct pt_regs *kernel_regs)
 67{
 68	from_gdb_regs(gdb_regs, kernel_regs, (struct callee_regs *)
 69		current->thread.callee_reg);
 70}
 71
 72void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs,
 73				 struct task_struct *task)
 74{
 75	if (task)
 76		to_gdb_regs(gdb_regs, task_pt_regs(task),
 77			(struct callee_regs *) task->thread.callee_reg);
 78}
 79
 80struct single_step_data_t {
 81	uint16_t opcode[2];
 82	unsigned long address[2];
 83	int is_branch;
 84	int armed;
 85} single_step_data;
 86
 87static void undo_single_step(struct pt_regs *regs)
 88{
 89	if (single_step_data.armed) {
 90		int i;
 91
 92		for (i = 0; i < (single_step_data.is_branch ? 2 : 1); i++) {
 93			memcpy((void *) single_step_data.address[i],
 94				&single_step_data.opcode[i],
 95				BREAK_INSTR_SIZE);
 96
 97			flush_icache_range(single_step_data.address[i],
 98				single_step_data.address[i] +
 99				BREAK_INSTR_SIZE);
100		}
101		single_step_data.armed = 0;
102	}
103}
104
105static void place_trap(unsigned long address, void *save)
106{
107	memcpy(save, (void *) address, BREAK_INSTR_SIZE);
108	memcpy((void *) address, &arch_kgdb_ops.gdb_bpt_instr,
109		BREAK_INSTR_SIZE);
110	flush_icache_range(address, address + BREAK_INSTR_SIZE);
111}
112
113static void do_single_step(struct pt_regs *regs)
114{
115	single_step_data.is_branch = disasm_next_pc((unsigned long)
116		regs->ret, regs, (struct callee_regs *)
117		current->thread.callee_reg,
118		&single_step_data.address[0],
119		&single_step_data.address[1]);
120
121	place_trap(single_step_data.address[0], &single_step_data.opcode[0]);
122
123	if (single_step_data.is_branch) {
124		place_trap(single_step_data.address[1],
125			&single_step_data.opcode[1]);
126	}
127
128	single_step_data.armed++;
129}
130
131int kgdb_arch_handle_exception(int e_vector, int signo, int err_code,
132			       char *remcomInBuffer, char *remcomOutBuffer,
133			       struct pt_regs *regs)
134{
135	unsigned long addr;
136	char *ptr;
137
138	undo_single_step(regs);
139
140	switch (remcomInBuffer[0]) {
141	case 's':
142	case 'c':
143		ptr = &remcomInBuffer[1];
144		if (kgdb_hex2long(&ptr, &addr))
145			regs->ret = addr;
146
147	case 'D':
148	case 'k':
149		atomic_set(&kgdb_cpu_doing_single_step, -1);
150
151		if (remcomInBuffer[0] == 's') {
152			do_single_step(regs);
153			atomic_set(&kgdb_cpu_doing_single_step,
154				   smp_processor_id());
155		}
156
157		return 0;
158	}
159	return -1;
160}
161
162int kgdb_arch_init(void)
163{
164	single_step_data.armed = 0;
165	return 0;
166}
167
168void kgdb_trap(struct pt_regs *regs)
169{
170	/* trap_s 3 is used for breakpoints that overwrite existing
171	 * instructions, while trap_s 4 is used for compiled breakpoints.
172	 *
173	 * with trap_s 3 breakpoints the original instruction needs to be
174	 * restored and continuation needs to start at the location of the
175	 * breakpoint.
176	 *
177	 * with trap_s 4 (compiled) breakpoints, continuation needs to
178	 * start after the breakpoint.
179	 */
180	if (regs->ecr_param == 3)
181		instruction_pointer(regs) -= BREAK_INSTR_SIZE;
182
183	kgdb_handle_exception(1, SIGTRAP, 0, regs);
184}
185
186void kgdb_arch_exit(void)
187{
188}
189
190void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long ip)
191{
192	instruction_pointer(regs) = ip;
193}
194
195static void kgdb_call_nmi_hook(void *ignored)
196{
197	kgdb_nmicallback(raw_smp_processor_id(), NULL);
198}
199
200void kgdb_roundup_cpus(unsigned long flags)
201{
202	local_irq_enable();
203	smp_call_function(kgdb_call_nmi_hook, NULL, 0);
204	local_irq_disable();
205}
206
207struct kgdb_arch arch_kgdb_ops = {
208	/* breakpoint instruction: TRAP_S 0x3 */
209#ifdef CONFIG_CPU_BIG_ENDIAN
210	.gdb_bpt_instr		= {0x78, 0x7e},
211#else
212	.gdb_bpt_instr		= {0x7e, 0x78},
213#endif
214};