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 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/cacheflush.h>
  16 #include <asm/asm.h>
  17 #include <asm/asm-offsets.h>
  18
  19 #ifdef CONFIG_DYNAMIC_FTRACE
  20
  21 #define JAL 0x0c000000          /* jump & link: ip --> ra, jump to target */
  22 #define ADDR_MASK 0x03ffffff    /*  op_code|addr : 31...26|25 ....0 */
  23 #define jump_insn_encode(op_code, addr) \
  24         ((unsigned int)((op_code) | (((addr) >> 2) & ADDR_MASK)))
  25
  26 #define INSN_B_1F_4 0x10000004  /* b 1f; offset = 4 */
  27 #define INSN_B_1F_5 0x10000005  /* b 1f; offset = 5 */
  28 #define INSN_NOP 0x00000000     /* nop */
  29 #define INSN_JAL(addr)  jump_insn_encode(JAL, addr)
  30
  31 static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
  32 {
  33         int faulted;
  34
  35         /* *(unsigned int *)ip = new_code; */
  36         safe_store_code(new_code, ip, faulted);
  37
  38         if (unlikely(faulted))
  39                 return -EFAULT;
  40
  41         flush_icache_range(ip, ip + 8);
  42
  43         return 0;
  44 }
  45
  46 static int lui_v1;
  47 static int jal_mcount;
  48
  49 int ftrace_make_nop(struct module *mod,
  50                     struct dyn_ftrace *rec, unsigned long addr)
  51 {
  52         unsigned int new;
  53         int faulted;
  54         unsigned long ip = rec->ip;
  55
  56         /* We have compiled module with -mlong-calls, but compiled the kernel
  57          * without it, we need to cope with them respectively. */
  58         if (ip & 0x40000000) {
  59                 /* record it for ftrace_make_call */
  60                 if (lui_v1 == 0) {
  61                         /* lui_v1 = *(unsigned int *)ip; */
  62                         safe_load_code(lui_v1, ip, faulted);
  63
  64                         if (unlikely(faulted))
  65                                 return -EFAULT;
  66                 }
  67
  68 #if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT)
  69                 /* lui v1, hi_16bit_of_mcount        --> b 1f (0x10000005)
  70                  * addiu v1, v1, low_16bit_of_mcount
  71                  * move at, ra
  72                  * move $12, ra_address
  73                  * jalr v1
  74                  *  sub sp, sp, 8
  75                  *                                  1: offset = 5 instructions
  76                  */
  77                 new = INSN_B_1F_5;
  78 #else
  79                 /* lui v1, hi_16bit_of_mcount        --> b 1f (0x10000004)
  80                  * addiu v1, v1, low_16bit_of_mcount
  81                  * move at, ra
  82                  * jalr v1
  83                  *  nop | move $12, ra_address | sub sp, sp, 8
  84                  *                                  1: offset = 4 instructions
  85                  */
  86                 new = INSN_B_1F_4;
  87 #endif
  88         } else {
  89                 /* record/calculate it for ftrace_make_call */
  90                 if (jal_mcount == 0) {
  91                         /* We can record it directly like this:
  92                          *     jal_mcount = *(unsigned int *)ip;
  93                          * Herein, jump over the first two nop instructions */
  94                         jal_mcount = INSN_JAL(MCOUNT_ADDR + 8);
  95                 }
  96
  97                 /* move at, ra
  98                  * jalr v1              --> nop
  99                  */
 100                 new = INSN_NOP;
 101         }
 102         return ftrace_modify_code(ip, new);
 103 }
 104
 105 static int modified;    /* initialized as 0 by default */
 106
 107 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 108 {
 109         unsigned int new;
 110         unsigned long ip = rec->ip;
 111
 112         /* We just need to remove the "b ftrace_stub" at the fist time! */
 113         if (modified == 0) {
 114                 modified = 1;
 115                 ftrace_modify_code(addr, INSN_NOP);
 116         }
 117         /* ip, module: 0xc0000000, kernel: 0x80000000 */
 118         new = (ip & 0x40000000) ? lui_v1 : jal_mcount;
 119
 120         return ftrace_modify_code(ip, new);
 121 }
 122
 123 #define FTRACE_CALL_IP ((unsigned long)(&ftrace_call))
 124
 125 int ftrace_update_ftrace_func(ftrace_func_t func)
 126 {
 127         unsigned int new;
 128
 129         new = INSN_JAL((unsigned long)func);
 130
 131         return ftrace_modify_code(FTRACE_CALL_IP, new);
 132 }
 133
 134 int __init ftrace_dyn_arch_init(void *data)
 135 {
 136         /* The return code is retured via data */
 137         *(unsigned long *)data = 0;
 138
 139         return 0;
 140 }
 141 #endif                          /* CONFIG_DYNAMIC_FTRACE */
 142
 143 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 144
 145 #ifdef CONFIG_DYNAMIC_FTRACE
 146
 147 extern void ftrace_graph_call(void);
 148 #define JMP     0x08000000      /* jump to target directly */
 149 #define CALL_FTRACE_GRAPH_CALLER \
 150         jump_insn_encode(JMP, (unsigned long)(&ftrace_graph_caller))
 151 #define FTRACE_GRAPH_CALL_IP    ((unsigned long)(&ftrace_graph_call))
 152
 153 int ftrace_enable_ftrace_graph_caller(void)
 154 {
 155         return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
 156                                   CALL_FTRACE_GRAPH_CALLER);
 157 }
 158
 159 int ftrace_disable_ftrace_graph_caller(void)
 160 {
 161         return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP);
 162 }
 163
 164 #endif                          /* !CONFIG_DYNAMIC_FTRACE */
 165
 166 #ifndef KBUILD_MCOUNT_RA_ADDRESS
 167 #define S_RA_SP (0xafbf << 16)  /* s{d,w} ra, offset(sp) */
 168 #define S_R_SP  (0xafb0 << 16)  /* s{d,w} R, offset(sp) */
 169 #define OFFSET_MASK     0xffff  /* stack offset range: 0 ~ PT_SIZE */
 170
 171 unsigned long ftrace_get_parent_addr(unsigned long self_addr,
 172                                      unsigned long parent,
 173                                      unsigned long parent_addr,
 174                                      unsigned long fp)
 175 {
 176         unsigned long sp, ip, ra;
 177         unsigned int code;
 178         int faulted;
 179
 180         /* in module or kernel? */
 181         if (self_addr & 0x40000000) {
 182                 /* module: move to the instruction "lui v1, HI_16BIT_OF_MCOUNT" */
 183                 ip = self_addr - 20;
 184         } else {
 185                 /* kernel: move to the instruction "move ra, at" */
 186                 ip = self_addr - 12;
 187         }
 188
 189         /* search the text until finding the non-store instruction or "s{d,w}
 190          * ra, offset(sp)" instruction */
 191         do {
 192                 ip -= 4;
 193
 194                 /* get the code at "ip": code = *(unsigned int *)ip; */
 195                 safe_load_code(code, ip, faulted);
 196
 197                 if (unlikely(faulted))
 198                         return 0;
 199
 200                 /* If we hit the non-store instruction before finding where the
 201                  * ra is stored, then this is a leaf function and it does not
 202                  * store the ra on the stack. */
 203                 if ((code & S_R_SP) != S_R_SP)
 204                         return parent_addr;
 205
 206         } while (((code & S_RA_SP) != S_RA_SP));
 207
 208         sp = fp + (code & OFFSET_MASK);
 209
 210         /* ra = *(unsigned long *)sp; */
 211         safe_load_stack(ra, sp, faulted);
 212         if (unlikely(faulted))
 213                 return 0;
 214
 215         if (ra == parent)
 216                 return sp;
 217         return 0;
 218 }
 219
 220 #endif
 221
 222 /*
 223  * Hook the return address and push it in the stack of return addrs
 224  * in current thread info.
 225  */
 226 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
 227                            unsigned long fp)
 228 {
 229         unsigned long old;
 230         struct ftrace_graph_ent trace;
 231         unsigned long return_hooker = (unsigned long)
 232             &return_to_handler;
 233         int faulted;
 234
 235         if (unlikely(atomic_read(&current->tracing_graph_pause)))
 236                 return;
 237
 238         /* "parent" is the stack address saved the return address of the caller
 239          * of _mcount.
 240          *
 241          * if the gcc < 4.5, a leaf function does not save the return address
 242          * in the stack address, so, we "emulate" one in _mcount's stack space,
 243          * and hijack it directly, but for a non-leaf function, it save the
 244          * return address to the its own stack space, we can not hijack it
 245          * directly, but need to find the real stack address,
 246          * ftrace_get_parent_addr() does it!
 247          *
 248          * if gcc>= 4.5, with the new -mmcount-ra-address option, for a
 249          * non-leaf function, the location of the return address will be saved
 250          * to $12 for us, and for a leaf function, only put a zero into $12. we
 251          * do it in ftrace_graph_caller of mcount.S.
 252          */
 253
 254         /* old = *parent; */
 255         safe_load_stack(old, parent, faulted);
 256         if (unlikely(faulted))
 257                 goto out;
 258 #ifndef KBUILD_MCOUNT_RA_ADDRESS
 259         parent = (unsigned long *)ftrace_get_parent_addr(self_addr, old,
 260                                                          (unsigned long)parent,
 261                                                          fp);
 262         /* If fails when getting the stack address of the non-leaf function's
 263          * ra, stop function graph tracer and return */
 264         if (parent == 0)
 265                 goto out;
 266 #endif
 267         /* *parent = return_hooker; */
 268         safe_store_stack(return_hooker, parent, faulted);
 269         if (unlikely(faulted))
 270                 goto out;
 271
 272         if (ftrace_push_return_trace(old, self_addr, &trace.depth, fp) ==
 273             -EBUSY) {
 274                 *parent = old;
 275                 return;
 276         }
 277
 278         trace.func = self_addr;
 279
 280         /* Only trace if the calling function expects to */
 281         if (!ftrace_graph_entry(&trace)) {
 282                 current->curr_ret_stack--;
 283                 *parent = old;
 284         }
 285         return;
 286 out:
 287         ftrace_graph_stop();
 288         WARN_ON(1);
 289 }
 290 #endif                          /* CONFIG_FUNCTION_GRAPH_TRACER */