xref: /openbmc/linux/arch/microblaze/kernel/ftrace.c (revision 6644c654)
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;
26 	unsigned long return_hooker = (unsigned long)
27 				&return_to_handler;
28 
29 	if (unlikely(ftrace_graph_is_dead()))
30 		return;
31 
32 	if (unlikely(atomic_read(&current->tracing_graph_pause)))
33 		return;
34 
35 	/*
36 	 * Protect against fault, even if it shouldn't
37 	 * happen. This tool is too much intrusive to
38 	 * ignore such a protection.
39 	 */
40 	asm volatile("	1:	lwi	%0, %2, 0;"		\
41 			"2:	swi	%3, %2, 0;"		\
42 			"	addik	%1, r0, 0;"		\
43 			"3:"					\
44 			"	.section .fixup, \"ax\";"	\
45 			"4:	brid	3b;"			\
46 			"	addik	%1, r0, 1;"		\
47 			"	.previous;"			\
48 			"	.section __ex_table,\"a\";"	\
49 			"	.word	1b,4b;"			\
50 			"	.word	2b,4b;"			\
51 			"	.previous;"			\
52 			: "=&r" (old), "=r" (faulted)
53 			: "r" (parent), "r" (return_hooker)
54 	);
55 
56 	flush_dcache_range((u32)parent, (u32)parent + 4);
57 	flush_icache_range((u32)parent, (u32)parent + 4);
58 
59 	if (unlikely(faulted)) {
60 		ftrace_graph_stop();
61 		WARN_ON(1);
62 		return;
63 	}
64 
65 	if (function_graph_enter(old, self_addr, 0, NULL))
66 		*parent = old;
67 }
68 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
69 
70 #ifdef CONFIG_DYNAMIC_FTRACE
71 /* save value to addr - it is save to do it in asm */
ftrace_modify_code(unsigned long addr,unsigned int value)72 static int ftrace_modify_code(unsigned long addr, unsigned int value)
73 {
74 	int faulted = 0;
75 
76 	__asm__ __volatile__("	1:	swi	%2, %1, 0;"		\
77 				"	addik	%0, r0, 0;"		\
78 				"2:"					\
79 				"	.section .fixup, \"ax\";"	\
80 				"3:	brid	2b;"			\
81 				"	addik	%0, r0, 1;"		\
82 				"	.previous;"			\
83 				"	.section __ex_table,\"a\";"	\
84 				"	.word	1b,3b;"			\
85 				"	.previous;"			\
86 				: "=r" (faulted)
87 				: "r" (addr), "r" (value)
88 	);
89 
90 	if (unlikely(faulted))
91 		return -EFAULT;
92 
93 	flush_dcache_range(addr, addr + 4);
94 	flush_icache_range(addr, addr + 4);
95 
96 	return 0;
97 }
98 
99 #define MICROBLAZE_NOP 0x80000000
100 #define MICROBLAZE_BRI 0xb800000C
101 
102 static unsigned int recorded; /* if save was or not */
103 static unsigned int imm; /* saving whole imm instruction */
104 
105 /* There are two approaches howto solve ftrace_make nop function - look below */
106 #undef USE_FTRACE_NOP
107 
108 #ifdef USE_FTRACE_NOP
109 static unsigned int bralid; /* saving whole bralid instruction */
110 #endif
111 
ftrace_make_nop(struct module * mod,struct dyn_ftrace * rec,unsigned long addr)112 int ftrace_make_nop(struct module *mod,
113 			struct dyn_ftrace *rec, unsigned long addr)
114 {
115 	/* we have this part of code which we are working with
116 	 * b000c000        imm     -16384
117 	 * b9fc8e30        bralid  r15, -29136     // c0008e30 <_mcount>
118 	 * 80000000        or      r0, r0, r0
119 	 *
120 	 * The first solution (!USE_FTRACE_NOP-could be called branch solution)
121 	 * b000c000        bri	12 (0xC - jump to any other instruction)
122 	 * b9fc8e30        bralid  r15, -29136     // c0008e30 <_mcount>
123 	 * 80000000        or      r0, r0, r0
124 	 * any other instruction
125 	 *
126 	 * The second solution (USE_FTRACE_NOP) - no jump just nops
127 	 * 80000000        or      r0, r0, r0
128 	 * 80000000        or      r0, r0, r0
129 	 * 80000000        or      r0, r0, r0
130 	 */
131 	int ret = 0;
132 
133 	if (recorded == 0) {
134 		recorded = 1;
135 		imm = *(unsigned int *)rec->ip;
136 		pr_debug("%s: imm:0x%x\n", __func__, imm);
137 #ifdef USE_FTRACE_NOP
138 		bralid = *(unsigned int *)(rec->ip + 4);
139 		pr_debug("%s: bralid 0x%x\n", __func__, bralid);
140 #endif /* USE_FTRACE_NOP */
141 	}
142 
143 #ifdef USE_FTRACE_NOP
144 	ret = ftrace_modify_code(rec->ip, MICROBLAZE_NOP);
145 	ret += ftrace_modify_code(rec->ip + 4, MICROBLAZE_NOP);
146 #else /* USE_FTRACE_NOP */
147 	ret = ftrace_modify_code(rec->ip, MICROBLAZE_BRI);
148 #endif /* USE_FTRACE_NOP */
149 	return ret;
150 }
151 
152 /* I believe that first is called ftrace_make_nop before this function */
ftrace_make_call(struct dyn_ftrace * rec,unsigned long addr)153 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
154 {
155 	int ret;
156 	pr_debug("%s: addr:0x%x, rec->ip: 0x%x, imm:0x%x\n",
157 		__func__, (unsigned int)addr, (unsigned int)rec->ip, imm);
158 	ret = ftrace_modify_code(rec->ip, imm);
159 #ifdef USE_FTRACE_NOP
160 	pr_debug("%s: bralid:0x%x\n", __func__, bralid);
161 	ret += ftrace_modify_code(rec->ip + 4, bralid);
162 #endif /* USE_FTRACE_NOP */
163 	return ret;
164 }
165 
ftrace_update_ftrace_func(ftrace_func_t func)166 int ftrace_update_ftrace_func(ftrace_func_t func)
167 {
168 	unsigned long ip = (unsigned long)(&ftrace_call);
169 	unsigned int upper = (unsigned int)func;
170 	unsigned int lower = (unsigned int)func;
171 	int ret = 0;
172 
173 	/* create proper saving to ftrace_call poll */
174 	upper = 0xb0000000 + (upper >> 16); /* imm func_upper */
175 	lower = 0x32800000 + (lower & 0xFFFF); /* addik r20, r0, func_lower */
176 
177 	pr_debug("%s: func=0x%x, ip=0x%x, upper=0x%x, lower=0x%x\n",
178 		__func__, (unsigned int)func, (unsigned int)ip, upper, lower);
179 
180 	/* save upper and lower code */
181 	ret = ftrace_modify_code(ip, upper);
182 	ret += ftrace_modify_code(ip + 4, lower);
183 
184 	/* We just need to replace the rtsd r15, 8 with NOP */
185 	ret += ftrace_modify_code((unsigned long)&ftrace_caller,
186 				  MICROBLAZE_NOP);
187 
188 	return ret;
189 }
190 
191 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
192 unsigned int old_jump; /* saving place for jump instruction */
193 
ftrace_enable_ftrace_graph_caller(void)194 int ftrace_enable_ftrace_graph_caller(void)
195 {
196 	unsigned int ret;
197 	unsigned long ip = (unsigned long)(&ftrace_call_graph);
198 
199 	old_jump = *(unsigned int *)ip; /* save jump over instruction */
200 	ret = ftrace_modify_code(ip, MICROBLAZE_NOP);
201 
202 	pr_debug("%s: Replace instruction: 0x%x\n", __func__, old_jump);
203 	return ret;
204 }
205 
ftrace_disable_ftrace_graph_caller(void)206 int ftrace_disable_ftrace_graph_caller(void)
207 {
208 	unsigned int ret;
209 	unsigned long ip = (unsigned long)(&ftrace_call_graph);
210 
211 	ret = ftrace_modify_code(ip, old_jump);
212 
213 	pr_debug("%s\n", __func__);
214 	return ret;
215 }
216 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
217 #endif /* CONFIG_DYNAMIC_FTRACE */
218