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
 14static 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
 37static 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
 57void 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
 63void 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
 69void 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
 77struct 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
 84static 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
102static 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
110static 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
128int 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
160int kgdb_arch_init(void)
161{
162	single_step_data.armed = 0;
163	return 0;
164}
165
166void 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
184void kgdb_arch_exit(void)
185{
186}
187
188void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long ip)
189{
190	instruction_pointer(regs) = ip;
191}
192
193void 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
199const 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};