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