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  */
prepare_ftrace_return(unsigned long * parent,unsigned long self_addr)22 void 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(atomic_read(&current->tracing_graph_pause)))
31 		return;
32 
33 	/*
34 	 * Protect against fault, even if it shouldn't
35 	 * happen. This tool is too much intrusive to
36 	 * ignore such a protection.
37 	 */
38 	asm volatile("	1:	lwi	%0, %2, 0;		\
39 			2:	swi	%3, %2, 0;		\
40 				addik	%1, r0, 0;		\
41 			3:					\
42 				.section .fixup, \"ax\";	\
43 			4:	brid	3b;			\
44 				addik	%1, r0, 1;		\
45 				.previous;			\
46 				.section __ex_table,\"a\";	\
47 				.word	1b,4b;			\
48 				.word	2b,4b;			\
49 				.previous;"			\
50 			: "=&r" (old), "=r" (faulted)
51 			: "r" (parent), "r" (return_hooker)
52 	);
53 
54 	flush_dcache_range((u32)parent, (u32)parent + 4);
55 	flush_icache_range((u32)parent, (u32)parent + 4);
56 
57 	if (unlikely(faulted)) {
58 		ftrace_graph_stop();
59 		WARN_ON(1);
60 		return;
61 	}
62 
63 	err = ftrace_push_return_trace(old, self_addr, &trace.depth, 0);
64 	if (err == -EBUSY) {
65 		*parent = old;
66 		return;
67 	}
68 
69 	trace.func = self_addr;
70 	/* Only trace if the calling function expects to */
71 	if (!ftrace_graph_entry(&trace)) {
72 		current->curr_ret_stack--;
73 		*parent = old;
74 	}
75 }
76 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
77 
78 #ifdef CONFIG_DYNAMIC_FTRACE
79 /* save value to addr - it is save to do it in asm */
ftrace_modify_code(unsigned long addr,unsigned int value)80 static int ftrace_modify_code(unsigned long addr, unsigned int value)
81 {
82 	int faulted = 0;
83 
84 	__asm__ __volatile__("	1:	swi	%2, %1, 0;		\
85 					addik	%0, r0, 0;		\
86 				2:					\
87 					.section .fixup, \"ax\";	\
88 				3:	brid	2b;			\
89 					addik	%0, r0, 1;		\
90 					.previous;			\
91 					.section __ex_table,\"a\";	\
92 					.word	1b,3b;			\
93 					.previous;"			\
94 				: "=r" (faulted)
95 				: "r" (addr), "r" (value)
96 	);
97 
98 	if (unlikely(faulted))
99 		return -EFAULT;
100 
101 	flush_dcache_range(addr, addr + 4);
102 	flush_icache_range(addr, addr + 4);
103 
104 	return 0;
105 }
106 
107 #define MICROBLAZE_NOP 0x80000000
108 #define MICROBLAZE_BRI 0xb800000C
109 
110 static unsigned int recorded; /* if save was or not */
111 static unsigned int imm; /* saving whole imm instruction */
112 
113 /* There are two approaches howto solve ftrace_make nop function - look below */
114 #undef USE_FTRACE_NOP
115 
116 #ifdef USE_FTRACE_NOP
117 static unsigned int bralid; /* saving whole bralid instruction */
118 #endif
119 
ftrace_make_nop(struct module * mod,struct dyn_ftrace * rec,unsigned long addr)120 int ftrace_make_nop(struct module *mod,
121 			struct dyn_ftrace *rec, unsigned long addr)
122 {
123 	/* we have this part of code which we are working with
124 	 * b000c000        imm     -16384
125 	 * b9fc8e30        bralid  r15, -29136     // c0008e30 <_mcount>
126 	 * 80000000        or      r0, r0, r0
127 	 *
128 	 * The first solution (!USE_FTRACE_NOP-could be called branch solution)
129 	 * b000c000        bri	12 (0xC - jump to any other instruction)
130 	 * b9fc8e30        bralid  r15, -29136     // c0008e30 <_mcount>
131 	 * 80000000        or      r0, r0, r0
132 	 * any other instruction
133 	 *
134 	 * The second solution (USE_FTRACE_NOP) - no jump just nops
135 	 * 80000000        or      r0, r0, r0
136 	 * 80000000        or      r0, r0, r0
137 	 * 80000000        or      r0, r0, r0
138 	 */
139 	int ret = 0;
140 
141 	if (recorded == 0) {
142 		recorded = 1;
143 		imm = *(unsigned int *)rec->ip;
144 		pr_debug("%s: imm:0x%x\n", __func__, imm);
145 #ifdef USE_FTRACE_NOP
146 		bralid = *(unsigned int *)(rec->ip + 4);
147 		pr_debug("%s: bralid 0x%x\n", __func__, bralid);
148 #endif /* USE_FTRACE_NOP */
149 	}
150 
151 #ifdef USE_FTRACE_NOP
152 	ret = ftrace_modify_code(rec->ip, MICROBLAZE_NOP);
153 	ret += ftrace_modify_code(rec->ip + 4, MICROBLAZE_NOP);
154 #else /* USE_FTRACE_NOP */
155 	ret = ftrace_modify_code(rec->ip, MICROBLAZE_BRI);
156 #endif /* USE_FTRACE_NOP */
157 	return ret;
158 }
159 
160 /* I believe that first is called ftrace_make_nop before this function */
ftrace_make_call(struct dyn_ftrace * rec,unsigned long addr)161 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
162 {
163 	int ret;
164 	pr_debug("%s: addr:0x%x, rec->ip: 0x%x, imm:0x%x\n",
165 		__func__, (unsigned int)addr, (unsigned int)rec->ip, imm);
166 	ret = ftrace_modify_code(rec->ip, imm);
167 #ifdef USE_FTRACE_NOP
168 	pr_debug("%s: bralid:0x%x\n", __func__, bralid);
169 	ret += ftrace_modify_code(rec->ip + 4, bralid);
170 #endif /* USE_FTRACE_NOP */
171 	return ret;
172 }
173 
ftrace_dyn_arch_init(void * data)174 int __init ftrace_dyn_arch_init(void *data)
175 {
176 	/* The return code is retured via data */
177 	*(unsigned long *)data = 0;
178 
179 	return 0;
180 }
181 
ftrace_update_ftrace_func(ftrace_func_t func)182 int 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
208 unsigned int old_jump; /* saving place for jump instruction */
209 
ftrace_enable_ftrace_graph_caller(void)210 int 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 
ftrace_disable_ftrace_graph_caller(void)222 int 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