release/src-rt-6.x.4708/linux/linux-2.6.36/arch/mips/kernel/ftrace.c

   1 /*
   2  * Code for replacing ftrace calls with jumps.
   3  *
   4  * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
   5  * Copyright (C) 2009, 2010 DSLab, Lanzhou University, China
   6  * Author: Wu Zhangjin <wuzhangjin@gmail.com>
   7  *
   8  * Thanks goes to Steven Rostedt for writing the original x86 version.
   9  */
  10
  11 #include <linux/uaccess.h>
  12 #include <linux/init.h>
  13 #include <linux/ftrace.h>
  14
  15 #include <asm/asm.h>
  16 #include <asm/asm-offsets.h>
  17 #include <asm/cacheflush.h>
  18 #include <asm/uasm.h>
  19
  20
  21 static inline int in_module(unsigned long ip)
  22 {
  23         return ip & 0x40000000;
  24 }
  25
  26 #ifdef CONFIG_DYNAMIC_FTRACE
  27
  28 #define JAL 0x0c000000          /* jump & link: ip --> ra, jump to target */
  29 #define ADDR_MASK 0x03ffffff    /*  op_code|addr : 31...26|25 ....0 */
  30 #define JUMP_RANGE_MASK ((1UL << 28) - 1)
  31
  32 #define INSN_B_1F_4 0x10000004  /* b 1f; offset = 4 */
  33 #define INSN_B_1F_5 0x10000005  /* b 1f; offset = 5 */
  34 #define INSN_NOP 0x00000000     /* nop */
  35 #define INSN_JAL(addr)  \
  36         ((unsigned int)(JAL | (((addr) >> 2) & ADDR_MASK)))
  37
  38 static unsigned int insn_jal_ftrace_caller __read_mostly;
  39 static unsigned int insn_lui_v1_hi16_mcount __read_mostly;
  40 static unsigned int insn_j_ftrace_graph_caller __maybe_unused __read_mostly;
  41
  42 static inline void ftrace_dyn_arch_init_insns(void)
  43 {
  44         u32 *buf;
  45         unsigned int v1;
  46
  47         /* lui v1, hi16_mcount */
  48         v1 = 3;
  49         buf = (u32 *)&insn_lui_v1_hi16_mcount;
  50         UASM_i_LA_mostly(&buf, v1, MCOUNT_ADDR);
  51
  52         /* jal (ftrace_caller + 8), jump over the first two instruction */
  53         buf = (u32 *)&insn_jal_ftrace_caller;
  54         uasm_i_jal(&buf, (FTRACE_ADDR + 8) & JUMP_RANGE_MASK);
  55
  56 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
  57         /* j ftrace_graph_caller */
  58         buf = (u32 *)&insn_j_ftrace_graph_caller;
  59         uasm_i_j(&buf, (unsigned long)ftrace_graph_caller & JUMP_RANGE_MASK);
  60 #endif
  61 }
  62
  63 static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
  64 {
  65         int faulted;
  66
  67         /* *(unsigned int *)ip = new_code; */
  68         safe_store_code(new_code, ip, faulted);
  69
  70         if (unlikely(faulted))
  71                 return -EFAULT;
  72
  73         flush_icache_range(ip, ip + 8);
  74
  75         return 0;
  76 }
  77
  78 int ftrace_make_nop(struct module *mod,
  79                     struct dyn_ftrace *rec, unsigned long addr)
  80 {
  81         unsigned int new;
  82         unsigned long ip = rec->ip;
  83
  84         /*
  85          * We have compiled module with -mlong-calls, but compiled the kernel
  86          * without it, we need to cope with them respectively.
  87          */
  88         if (in_module(ip)) {
  89 #if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT)
  90                 /*
  91                  * lui v1, hi_16bit_of_mcount        --> b 1f (0x10000005)
  92                  * addiu v1, v1, low_16bit_of_mcount
  93                  * move at, ra
  94                  * move $12, ra_address
  95                  * jalr v1
  96                  *  sub sp, sp, 8
  97                  *                                  1: offset = 5 instructions
  98                  */
  99                 new = INSN_B_1F_5;
 100 #else
 101                 /*
 102                  * lui v1, hi_16bit_of_mcount        --> b 1f (0x10000004)
 103                  * addiu v1, v1, low_16bit_of_mcount
 104                  * move at, ra
 105                  * jalr v1
 106                  *  nop | move $12, ra_address | sub sp, sp, 8
 107                  *                                  1: offset = 4 instructions
 108                  */
 109                 new = INSN_B_1F_4;
 110 #endif
 111         } else {
 112                 /*
 113                  * move at, ra
 114                  * jal _mcount          --> nop
 115                  */
 116                 new = INSN_NOP;
 117         }
 118         return ftrace_modify_code(ip, new);
 119 }
 120
 121 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 122 {
 123         unsigned int new;
 124         unsigned long ip = rec->ip;
 125
 126         /* ip, module: 0xc0000000, kernel: 0x80000000 */
 127         new = in_module(ip) ? insn_lui_v1_hi16_mcount : insn_jal_ftrace_caller;
 128
 129         return ftrace_modify_code(ip, new);
 130 }
 131
 132 #define FTRACE_CALL_IP ((unsigned long)(&ftrace_call))
 133
 134 int ftrace_update_ftrace_func(ftrace_func_t func)
 135 {
 136         unsigned int new;
 137
 138         new = INSN_JAL((unsigned long)func);
 139
 140         return ftrace_modify_code(FTRACE_CALL_IP, new);
 141 }
 142
 143 int __init ftrace_dyn_arch_init(void *data)
 144 {
 145         /* Encode the instructions when booting */
 146         ftrace_dyn_arch_init_insns();
 147
 148         /* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */
 149         ftrace_modify_code(MCOUNT_ADDR, INSN_NOP);
 150
 151         /* The return code is retured via data */
 152         *(unsigned long *)data = 0;
 153
 154         return 0;
 155 }
 156 #endif  /* CONFIG_DYNAMIC_FTRACE */
 157
 158 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 159
 160 #ifdef CONFIG_DYNAMIC_FTRACE
 161
 162 extern void ftrace_graph_call(void);
 163 #define FTRACE_GRAPH_CALL_IP    ((unsigned long)(&ftrace_graph_call))
 164
 165 int ftrace_enable_ftrace_graph_caller(void)
 166 {
 167         return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
 168                         insn_j_ftrace_graph_caller);
 169 }
 170
 171 int ftrace_disable_ftrace_graph_caller(void)
 172 {
 173         return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP);
 174 }
 175
 176 #endif  /* CONFIG_DYNAMIC_FTRACE */
 177
 178 #ifndef KBUILD_MCOUNT_RA_ADDRESS
 179
 180 #define S_RA_SP (0xafbf << 16)  /* s{d,w} ra, offset(sp) */
 181 #define S_R_SP  (0xafb0 << 16)  /* s{d,w} R, offset(sp) */
 182 #define OFFSET_MASK     0xffff  /* stack offset range: 0 ~ PT_SIZE */
 183
 184 unsigned long ftrace_get_parent_addr(unsigned long self_addr,
 185                                      unsigned long parent,
 186                                      unsigned long parent_addr,
 187                                      unsigned long fp)
 188 {
 189         unsigned long sp, ip, ra;
 190         unsigned int code;
 191         int faulted;
 192
 193         /*
 194          * For module, move the ip from calling site of mcount to the
 195          * instruction "lui v1, hi_16bit_of_mcount"(offset is 20), but for
 196          * kernel, move to the instruction "move ra, at"(offset is 12)
 197          */
 198         ip = self_addr - (in_module(self_addr) ? 20 : 12);
 199
 200         /*
 201          * search the text until finding the non-store instruction or "s{d,w}
 202          * ra, offset(sp)" instruction
 203          */
 204         do {
 205                 ip -= 4;
 206
 207                 /* get the code at "ip": code = *(unsigned int *)ip; */
 208                 safe_load_code(code, ip, faulted);
 209
 210                 if (unlikely(faulted))
 211                         return 0;
 212                 /*
 213                  * If we hit the non-store instruction before finding where the
 214                  * ra is stored, then this is a leaf function and it does not
 215                  * store the ra on the stack
 216                  */
 217                 if ((code & S_R_SP) != S_R_SP)
 218                         return parent_addr;
 219
 220         } while (((code & S_RA_SP) != S_RA_SP));
 221
 222         sp = fp + (code & OFFSET_MASK);
 223
 224         /* ra = *(unsigned long *)sp; */
 225         safe_load_stack(ra, sp, faulted);
 226         if (unlikely(faulted))
 227                 return 0;
 228
 229         if (ra == parent)
 230                 return sp;
 231         return 0;
 232 }
 233
 234 #endif  /* !KBUILD_MCOUNT_RA_ADDRESS */
 235
 236 /*
 237  * Hook the return address and push it in the stack of return addrs
 238  * in current thread info.
 239  */
 240 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
 241                            unsigned long fp)
 242 {
 243         unsigned long old;
 244         struct ftrace_graph_ent trace;
 245         unsigned long return_hooker = (unsigned long)
 246             &return_to_handler;
 247         int faulted;
 248
 249         if (unlikely(atomic_read(&current->tracing_graph_pause)))
 250                 return;
 251
 252         /*
 253          * "parent" is the stack address saved the return address of the caller
 254          * of _mcount.
 255          *
 256          * if the gcc < 4.5, a leaf function does not save the return address
 257          * in the stack address, so, we "emulate" one in _mcount's stack space,
 258          * and hijack it directly, but for a non-leaf function, it save the
 259          * return address to the its own stack space, we can not hijack it
 260          * directly, but need to find the real stack address,
 261          * ftrace_get_parent_addr() does it!
 262          *
 263          * if gcc>= 4.5, with the new -mmcount-ra-address option, for a
 264          * non-leaf function, the location of the return address will be saved
 265          * to $12 for us, and for a leaf function, only put a zero into $12. we
 266          * do it in ftrace_graph_caller of mcount.S.
 267          */
 268
 269         /* old = *parent; */
 270         safe_load_stack(old, parent, faulted);
 271         if (unlikely(faulted))
 272                 goto out;
 273 #ifndef KBUILD_MCOUNT_RA_ADDRESS
 274         parent = (unsigned long *)ftrace_get_parent_addr(self_addr, old,
 275                         (unsigned long)parent, fp);
 276         /*
 277          * If fails when getting the stack address of the non-leaf function's
 278          * ra, stop function graph tracer and return
 279          */
 280         if (parent == 0)
 281                 goto out;
 282 #endif
 283         /* *parent = return_hooker; */
 284         safe_store_stack(return_hooker, parent, faulted);
 285         if (unlikely(faulted))
 286                 goto out;
 287
 288         if (ftrace_push_return_trace(old, self_addr, &trace.depth, fp) ==
 289             -EBUSY) {
 290                 *parent = old;
 291                 return;
 292         }
 293
 294         trace.func = self_addr;
 295
 296         /* Only trace if the calling function expects to */
 297         if (!ftrace_graph_entry(&trace)) {
 298                 current->curr_ret_stack--;
 299                 *parent = old;
 300         }
 301         return;
 302 out:
 303         ftrace_graph_stop();
 304         WARN_ON(1);
 305 }
 306 #endif  /* CONFIG_FUNCTION_GRAPH_TRACER */