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Linux/arch/microblaze/kernel/ftrace.c

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  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(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, NULL);
 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 */
 83 static 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 
113 static unsigned int recorded; /* if save was or not */
114 static 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
120 static unsigned int bralid; /* saving whole bralid instruction */
121 #endif
122 
123 int 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 */
164 int 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 
177 int __init ftrace_dyn_arch_init(void)
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 */
234 

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