1/*
2 * Ftrace support for Microblaze.
3 *
4 * Copyright (C) 2009 Michal Simek <monstr@monstr.eu>
5 * Copyright (C) 2009 PetaLogix
6 *
7 * Based on MIPS and PowerPC ftrace code
8 *
9 * This file is subject to the terms and conditions of the GNU General Public
10 * License. See the file "COPYING" in the main directory of this archive
11 * for more details.
12 */
13
14#include <asm/cacheflush.h>
15#include <linux/ftrace.h>
16
17#ifdef CONFIG_FUNCTION_GRAPH_TRACER
18/*
19 * Hook the return address and push it in the stack of return addrs
20 * in current thread info.
21 */
22void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
23{
24	unsigned long old;
25	int faulted, err;
26	struct ftrace_graph_ent trace;
27	unsigned long return_hooker = (unsigned long)
28				&return_to_handler;
29
30	if (unlikely(ftrace_graph_is_dead()))
31		return;
32
33	if (unlikely(atomic_read(&current->tracing_graph_pause)))
34		return;
35
36	/*
37	 * Protect against fault, even if it shouldn't
38	 * happen. This tool is too much intrusive to
39	 * ignore such a protection.
40	 */
41	asm volatile("	1:	lwi	%0, %2, 0;"		\
42			"2:	swi	%3, %2, 0;"		\
43			"	addik	%1, r0, 0;"		\
44			"3:"					\
45			"	.section .fixup, \"ax\";"	\
46			"4:	brid	3b;"			\
47			"	addik	%1, r0, 1;"		\
48			"	.previous;"			\
49			"	.section __ex_table,\"a\";"	\
50			"	.word	1b,4b;"			\
51			"	.word	2b,4b;"			\
52			"	.previous;"			\
53			: "=&r" (old), "=r" (faulted)
54			: "r" (parent), "r" (return_hooker)
55	);
56
57	flush_dcache_range((u32)parent, (u32)parent + 4);
58	flush_icache_range((u32)parent, (u32)parent + 4);
59
60	if (unlikely(faulted)) {
61		ftrace_graph_stop();
62		WARN_ON(1);
63		return;
64	}
65
66	err = ftrace_push_return_trace(old, self_addr, &trace.depth, 0);
67	if (err == -EBUSY) {
68		*parent = old;
69		return;
70	}
71
72	trace.func = self_addr;
73	/* Only trace if the calling function expects to */
74	if (!ftrace_graph_entry(&trace)) {
75		current->curr_ret_stack--;
76		*parent = old;
77	}
78}
79#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
80
81#ifdef CONFIG_DYNAMIC_FTRACE
82/* save value to addr - it is save to do it in asm */
83static int ftrace_modify_code(unsigned long addr, unsigned int value)
84{
85	int faulted = 0;
86
87	__asm__ __volatile__("	1:	swi	%2, %1, 0;"		\
88				"	addik	%0, r0, 0;"		\
89				"2:"					\
90				"	.section .fixup, \"ax\";"	\
91				"3:	brid	2b;"			\
92				"	addik	%0, r0, 1;"		\
93				"	.previous;"			\
94				"	.section __ex_table,\"a\";"	\
95				"	.word	1b,3b;"			\
96				"	.previous;"			\
97				: "=r" (faulted)
98				: "r" (addr), "r" (value)
99	);
100
101	if (unlikely(faulted))
102		return -EFAULT;
103
104	flush_dcache_range(addr, addr + 4);
105	flush_icache_range(addr, addr + 4);
106
107	return 0;
108}
109
110#define MICROBLAZE_NOP 0x80000000
111#define MICROBLAZE_BRI 0xb800000C
112
113static unsigned int recorded; /* if save was or not */
114static unsigned int imm; /* saving whole imm instruction */
115
116/* There are two approaches howto solve ftrace_make nop function - look below */
117#undef USE_FTRACE_NOP
118
119#ifdef USE_FTRACE_NOP
120static unsigned int bralid; /* saving whole bralid instruction */
121#endif
122
123int ftrace_make_nop(struct module *mod,
124			struct dyn_ftrace *rec, unsigned long addr)
125{
126	/* we have this part of code which we are working with
127	 * b000c000        imm     -16384
128	 * b9fc8e30        bralid  r15, -29136     // c0008e30 <_mcount>
129	 * 80000000        or      r0, r0, r0
130	 *
131	 * The first solution (!USE_FTRACE_NOP-could be called branch solution)
132	 * b000c000        bri	12 (0xC - jump to any other instruction)
133	 * b9fc8e30        bralid  r15, -29136     // c0008e30 <_mcount>
134	 * 80000000        or      r0, r0, r0
135	 * any other instruction
136	 *
137	 * The second solution (USE_FTRACE_NOP) - no jump just nops
138	 * 80000000        or      r0, r0, r0
139	 * 80000000        or      r0, r0, r0
140	 * 80000000        or      r0, r0, r0
141	 */
142	int ret = 0;
143
144	if (recorded == 0) {
145		recorded = 1;
146		imm = *(unsigned int *)rec->ip;
147		pr_debug("%s: imm:0x%x\n", __func__, imm);
148#ifdef USE_FTRACE_NOP
149		bralid = *(unsigned int *)(rec->ip + 4);
150		pr_debug("%s: bralid 0x%x\n", __func__, bralid);
151#endif /* USE_FTRACE_NOP */
152	}
153
154#ifdef USE_FTRACE_NOP
155	ret = ftrace_modify_code(rec->ip, MICROBLAZE_NOP);
156	ret += ftrace_modify_code(rec->ip + 4, MICROBLAZE_NOP);
157#else /* USE_FTRACE_NOP */
158	ret = ftrace_modify_code(rec->ip, MICROBLAZE_BRI);
159#endif /* USE_FTRACE_NOP */
160	return ret;
161}
162
163/* I believe that first is called ftrace_make_nop before this function */
164int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
165{
166	int ret;
167	pr_debug("%s: addr:0x%x, rec->ip: 0x%x, imm:0x%x\n",
168		__func__, (unsigned int)addr, (unsigned int)rec->ip, imm);
169	ret = ftrace_modify_code(rec->ip, imm);
170#ifdef USE_FTRACE_NOP
171	pr_debug("%s: bralid:0x%x\n", __func__, bralid);
172	ret += ftrace_modify_code(rec->ip + 4, bralid);
173#endif /* USE_FTRACE_NOP */
174	return ret;
175}
176
177int __init ftrace_dyn_arch_init(void)
178{
179	return 0;
180}
181
182int ftrace_update_ftrace_func(ftrace_func_t func)
183{
184	unsigned long ip = (unsigned long)(&ftrace_call);
185	unsigned int upper = (unsigned int)func;
186	unsigned int lower = (unsigned int)func;
187	int ret = 0;
188
189	/* create proper saving to ftrace_call poll */
190	upper = 0xb0000000 + (upper >> 16); /* imm func_upper */
191	lower = 0x32800000 + (lower & 0xFFFF); /* addik r20, r0, func_lower */
192
193	pr_debug("%s: func=0x%x, ip=0x%x, upper=0x%x, lower=0x%x\n",
194		__func__, (unsigned int)func, (unsigned int)ip, upper, lower);
195
196	/* save upper and lower code */
197	ret = ftrace_modify_code(ip, upper);
198	ret += ftrace_modify_code(ip + 4, lower);
199
200	/* We just need to replace the rtsd r15, 8 with NOP */
201	ret += ftrace_modify_code((unsigned long)&ftrace_caller,
202				  MICROBLAZE_NOP);
203
204	return ret;
205}
206
207#ifdef CONFIG_FUNCTION_GRAPH_TRACER
208unsigned int old_jump; /* saving place for jump instruction */
209
210int ftrace_enable_ftrace_graph_caller(void)
211{
212	unsigned int ret;
213	unsigned long ip = (unsigned long)(&ftrace_call_graph);
214
215	old_jump = *(unsigned int *)ip; /* save jump over instruction */
216	ret = ftrace_modify_code(ip, MICROBLAZE_NOP);
217
218	pr_debug("%s: Replace instruction: 0x%x\n", __func__, old_jump);
219	return ret;
220}
221
222int ftrace_disable_ftrace_graph_caller(void)
223{
224	unsigned int ret;
225	unsigned long ip = (unsigned long)(&ftrace_call_graph);
226
227	ret = ftrace_modify_code(ip, old_jump);
228
229	pr_debug("%s\n", __func__);
230	return ret;
231}
232#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
233#endif /* CONFIG_DYNAMIC_FTRACE */
234