arch/microblaze/kernel/ftrace.c

   1 /*
   2  * Ftrace support for Microblaze.
   3  *
   4  * Copyright (C) 2009 Michal Simek <[email protected]>
   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 */