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         if (unlikely(faulted)) {
  55                 ftrace_graph_stop();
  56                 WARN_ON(1);
  57                 return;
  58         }
  59
  60         err = ftrace_push_return_trace(old, self_addr, &trace.depth, 0);
  61         if (err == -EBUSY) {
  62                 *parent = old;
  63                 return;
  64         }
  65
  66         trace.func = self_addr;
  67         /* Only trace if the calling function expects to */
  68         if (!ftrace_graph_entry(&trace)) {
  69                 current->curr_ret_stack--;
  70                 *parent = old;
  71         }
  72 }
  73 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
  74
  75 #ifdef CONFIG_DYNAMIC_FTRACE
  76 /* save value to addr - it is save to do it in asm */
  77 static int ftrace_modify_code(unsigned long addr, unsigned int value)
  78 {
  79         int faulted = 0;
  80
  81         __asm__ __volatile__("  1:      swi     %2, %1, 0;              \
  82                                         addik   %0, r0, 0;              \
  83                                 2:                                      \
  84                                         .section .fixup, \"ax\";        \
  85                                 3:      brid    2b;                     \
  86                                         addik   %0, r0, 1;              \
  87                                         .previous;                      \
  88                                         .section __ex_table,\"a\";      \
  89                                         .word   1b,3b;                  \
  90                                         .previous;"                     \
  91                                 : "=r" (faulted)
  92                                 : "r" (addr), "r" (value)
  93         );
  94
  95         if (unlikely(faulted))
  96                 return -EFAULT;
  97
  98         return 0;
  99 }
 100
 101 #define MICROBLAZE_NOP 0x80000000
 102 #define MICROBLAZE_BRI 0xb800000C
 103
 104 static unsigned int recorded; /* if save was or not */
 105 static unsigned int imm; /* saving whole imm instruction */
 106
 107 /* There are two approaches howto solve ftrace_make nop function - look below */
 108 #undef USE_FTRACE_NOP
 109
 110 #ifdef USE_FTRACE_NOP
 111 static unsigned int bralid; /* saving whole bralid instruction */
 112 #endif
 113
 114 int ftrace_make_nop(struct module *mod,
 115                         struct dyn_ftrace *rec, unsigned long addr)
 116 {
 117         /* we have this part of code which we are working with
 118          * b000c000        imm     -16384
 119          * b9fc8e30        bralid  r15, -29136     // c0008e30 <_mcount>
 120          * 80000000        or      r0, r0, r0
 121          *
 122          * The first solution (!USE_FTRACE_NOP-could be called branch solution)
 123          * b000c000        bri  12 (0xC - jump to any other instruction)
 124          * b9fc8e30        bralid  r15, -29136     // c0008e30 <_mcount>
 125          * 80000000        or      r0, r0, r0
 126          * any other instruction
 127          *
 128          * The second solution (USE_FTRACE_NOP) - no jump just nops
 129          * 80000000        or      r0, r0, r0
 130          * 80000000        or      r0, r0, r0
 131          * 80000000        or      r0, r0, r0
 132          */
 133         int ret = 0;
 134
 135         if (recorded == 0) {
 136                 recorded = 1;
 137                 imm = *(unsigned int *)rec->ip;
 138                 pr_debug("%s: imm:0x%x\n", __func__, imm);
 139 #ifdef USE_FTRACE_NOP
 140                 bralid = *(unsigned int *)(rec->ip + 4);
 141                 pr_debug("%s: bralid 0x%x\n", __func__, bralid);
 142 #endif /* USE_FTRACE_NOP */
 143         }
 144
 145 #ifdef USE_FTRACE_NOP
 146         ret = ftrace_modify_code(rec->ip, MICROBLAZE_NOP);
 147         ret += ftrace_modify_code(rec->ip + 4, MICROBLAZE_NOP);
 148 #else /* USE_FTRACE_NOP */
 149         ret = ftrace_modify_code(rec->ip, MICROBLAZE_BRI);
 150 #endif /* USE_FTRACE_NOP */
 151         return ret;
 152 }
 153
 154 /* I believe that first is called ftrace_make_nop before this function */
 155 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 156 {
 157         int ret;
 158         pr_debug("%s: addr:0x%x, rec->ip: 0x%x, imm:0x%x\n",
 159                 __func__, (unsigned int)addr, (unsigned int)rec->ip, imm);
 160         ret = ftrace_modify_code(rec->ip, imm);
 161 #ifdef USE_FTRACE_NOP
 162         pr_debug("%s: bralid:0x%x\n", __func__, bralid);
 163         ret += ftrace_modify_code(rec->ip + 4, bralid);
 164 #endif /* USE_FTRACE_NOP */
 165         return ret;
 166 }
 167
 168 int __init ftrace_dyn_arch_init(void *data)
 169 {
 170         /* The return code is retured via data */
 171         *(unsigned long *)data = 0;
 172
 173         return 0;
 174 }
 175
 176 int ftrace_update_ftrace_func(ftrace_func_t func)
 177 {
 178         unsigned long ip = (unsigned long)(&ftrace_call);
 179         unsigned int upper = (unsigned int)func;
 180         unsigned int lower = (unsigned int)func;
 181         int ret = 0;
 182
 183         /* create proper saving to ftrace_call poll */
 184         upper = 0xb0000000 + (upper >> 16); /* imm func_upper */
 185         lower = 0x32800000 + (lower & 0xFFFF); /* addik r20, r0, func_lower */
 186
 187         pr_debug("%s: func=0x%x, ip=0x%x, upper=0x%x, lower=0x%x\n",
 188                 __func__, (unsigned int)func, (unsigned int)ip, upper, lower);
 189
 190         /* save upper and lower code */
 191         ret = ftrace_modify_code(ip, upper);
 192         ret += ftrace_modify_code(ip + 4, lower);
 193
 194         /* We just need to replace the rtsd r15, 8 with NOP */
 195         ret += ftrace_modify_code((unsigned long)&ftrace_caller,
 196                                   MICROBLAZE_NOP);
 197
 198         /* All changes are done - lets do caches consistent */
 199         flush_icache();
 200         return ret;
 201 }
 202
 203 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 204 unsigned int old_jump; /* saving place for jump instruction */
 205
 206 int ftrace_enable_ftrace_graph_caller(void)
 207 {
 208         unsigned int ret;
 209         unsigned long ip = (unsigned long)(&ftrace_call_graph);
 210
 211         old_jump = *(unsigned int *)ip; /* save jump over instruction */
 212         ret = ftrace_modify_code(ip, MICROBLAZE_NOP);
 213         flush_icache();
 214
 215         pr_debug("%s: Replace instruction: 0x%x\n", __func__, old_jump);
 216         return ret;
 217 }
 218
 219 int ftrace_disable_ftrace_graph_caller(void)
 220 {
 221         unsigned int ret;
 222         unsigned long ip = (unsigned long)(&ftrace_call_graph);
 223
 224         ret = ftrace_modify_code(ip, old_jump);
 225         flush_icache();
 226
 227         pr_debug("%s\n", __func__);
 228         return ret;
 229 }
 230 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
 231 #endif /* CONFIG_DYNAMIC_FTRACE */