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)
 175 {
 176         return 0;
 177 }
 178
 179 int ftrace_update_ftrace_func(ftrace_func_t func)
 180 {
 181         unsigned long ip = (unsigned long)(&ftrace_call);
 182         unsigned int upper = (unsigned int)func;
 183         unsigned int lower = (unsigned int)func;
 184         int ret = 0;
 185
 186         /* create proper saving to ftrace_call poll */
 187         upper = 0xb0000000 + (upper >> 16); /* imm func_upper */
 188         lower = 0x32800000 + (lower & 0xFFFF); /* addik r20, r0, func_lower */
 189
 190         pr_debug("%s: func=0x%x, ip=0x%x, upper=0x%x, lower=0x%x\n",
 191                 __func__, (unsigned int)func, (unsigned int)ip, upper, lower);
 192
 193         /* save upper and lower code */
 194         ret = ftrace_modify_code(ip, upper);
 195         ret += ftrace_modify_code(ip + 4, lower);
 196
 197         /* We just need to replace the rtsd r15, 8 with NOP */
 198         ret += ftrace_modify_code((unsigned long)&ftrace_caller,
 199                                   MICROBLAZE_NOP);
 200
 201         return ret;
 202 }
 203
 204 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 205 unsigned int old_jump; /* saving place for jump instruction */
 206
 207 int ftrace_enable_ftrace_graph_caller(void)
 208 {
 209         unsigned int ret;
 210         unsigned long ip = (unsigned long)(&ftrace_call_graph);
 211
 212         old_jump = *(unsigned int *)ip; /* save jump over instruction */
 213         ret = ftrace_modify_code(ip, MICROBLAZE_NOP);
 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
 226         pr_debug("%s\n", __func__);
 227         return ret;
 228 }
 229 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
 230 #endif /* CONFIG_DYNAMIC_FTRACE */