microblaze: Fix ftrace
[pandora-kernel.git] / arch / microblaze / kernel / ftrace.c
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  */
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 */
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
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 */
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
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
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
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
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 */