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 <wuzj@lemote.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                 /* lui v1, hi_16bit_of_mcount        --> b 1f (0x10000004)
  66                  * addiu v1, v1, low_16bit_of_mcount
  67                  * move at, ra
  68                  * jalr v1
  69                  * nop
  70                  *                                   1f: (ip + 12)
  71                  */
  72                 new = 0x10000004;
  73         } else {
  74                 /* record/calculate it for ftrace_make_call */
  75                 if (jal_mcount == 0) {
  76                         /* We can record it directly like this:
  77                          *     jal_mcount = *(unsigned int *)ip;
  78                          * Herein, jump over the first two nop instructions */
  79                         jal_mcount = jump_insn_encode(JAL, (MCOUNT_ADDR + 8));
  80                 }
  81
  82                 /* move at, ra
  83                  * jalr v1              --> nop
  84                  */
  85                 new = ftrace_nop;
  86         }
  87         return ftrace_modify_code(ip, new);
  88 }
  89
  90 static int modified;    /* initialized as 0 by default */
  91
  92 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
  93 {
  94         unsigned int new;
  95         unsigned long ip = rec->ip;
  96
  97         /* We just need to remove the "b ftrace_stub" at the fist time! */
  98         if (modified == 0) {
  99                 modified = 1;
 100                 ftrace_modify_code(addr, ftrace_nop);
 101         }
 102         /* ip, module: 0xc0000000, kernel: 0x80000000 */
 103         new = (ip & 0x40000000) ? lui_v1 : jal_mcount;
 104
 105         return ftrace_modify_code(ip, new);
 106 }
 107
 108 #define FTRACE_CALL_IP ((unsigned long)(&ftrace_call))
 109
 110 int ftrace_update_ftrace_func(ftrace_func_t func)
 111 {
 112         unsigned int new;
 113
 114         new = jump_insn_encode(JAL, (unsigned long)func);
 115
 116         return ftrace_modify_code(FTRACE_CALL_IP, new);
 117 }
 118
 119 int __init ftrace_dyn_arch_init(void *data)
 120 {
 121         /* The return code is retured via data */
 122         *(unsigned long *)data = 0;
 123
 124         return 0;
 125 }
 126 #endif                          /* CONFIG_DYNAMIC_FTRACE */
 127
 128 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 129
 130 #ifdef CONFIG_DYNAMIC_FTRACE
 131
 132 extern void ftrace_graph_call(void);
 133 #define JMP     0x08000000      /* jump to target directly */
 134 #define CALL_FTRACE_GRAPH_CALLER \
 135         jump_insn_encode(JMP, (unsigned long)(&ftrace_graph_caller))
 136 #define FTRACE_GRAPH_CALL_IP    ((unsigned long)(&ftrace_graph_call))
 137
 138 int ftrace_enable_ftrace_graph_caller(void)
 139 {
 140         return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
 141                                   CALL_FTRACE_GRAPH_CALLER);
 142 }
 143
 144 int ftrace_disable_ftrace_graph_caller(void)
 145 {
 146         return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, ftrace_nop);
 147 }
 148
 149 #endif                          /* !CONFIG_DYNAMIC_FTRACE */
 150
 151 #ifndef KBUILD_MCOUNT_RA_ADDRESS
 152 #define S_RA_SP (0xafbf << 16)  /* s{d,w} ra, offset(sp) */
 153 #define S_R_SP  (0xafb0 << 16)  /* s{d,w} R, offset(sp) */
 154 #define OFFSET_MASK     0xffff  /* stack offset range: 0 ~ PT_SIZE */
 155
 156 unsigned long ftrace_get_parent_addr(unsigned long self_addr,
 157                                      unsigned long parent,
 158                                      unsigned long parent_addr,
 159                                      unsigned long fp)
 160 {
 161         unsigned long sp, ip, ra;
 162         unsigned int code;
 163         int faulted;
 164
 165         /* in module or kernel? */
 166         if (self_addr & 0x40000000) {
 167                 /* module: move to the instruction "lui v1, HI_16BIT_OF_MCOUNT" */
 168                 ip = self_addr - 20;
 169         } else {
 170                 /* kernel: move to the instruction "move ra, at" */
 171                 ip = self_addr - 12;
 172         }
 173
 174         /* search the text until finding the non-store instruction or "s{d,w}
 175          * ra, offset(sp)" instruction */
 176         do {
 177                 ip -= 4;
 178
 179                 /* get the code at "ip": code = *(unsigned int *)ip; */
 180                 safe_load_code(code, ip, faulted);
 181
 182                 if (unlikely(faulted))
 183                         return 0;
 184
 185                 /* If we hit the non-store instruction before finding where the
 186                  * ra is stored, then this is a leaf function and it does not
 187                  * store the ra on the stack. */
 188                 if ((code & S_R_SP) != S_R_SP)
 189                         return parent_addr;
 190
 191         } while (((code & S_RA_SP) != S_RA_SP));
 192
 193         sp = fp + (code & OFFSET_MASK);
 194
 195         /* ra = *(unsigned long *)sp; */
 196         safe_load_stack(ra, sp, faulted);
 197         if (unlikely(faulted))
 198                 return 0;
 199
 200         if (ra == parent)
 201                 return sp;
 202         return 0;
 203 }
 204
 205 #endif
 206
 207 /*
 208  * Hook the return address and push it in the stack of return addrs
 209  * in current thread info.
 210  */
 211 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
 212                            unsigned long fp)
 213 {
 214         unsigned long old;
 215         struct ftrace_graph_ent trace;
 216         unsigned long return_hooker = (unsigned long)
 217             &return_to_handler;
 218         int faulted;
 219
 220         if (unlikely(atomic_read(&current->tracing_graph_pause)))
 221                 return;
 222
 223         /* "parent" is the stack address saved the return address of the caller
 224          * of _mcount.
 225          *
 226          * if the gcc < 4.5, a leaf function does not save the return address
 227          * in the stack address, so, we "emulate" one in _mcount's stack space,
 228          * and hijack it directly, but for a non-leaf function, it save the
 229          * return address to the its own stack space, we can not hijack it
 230          * directly, but need to find the real stack address,
 231          * ftrace_get_parent_addr() does it!
 232          *
 233          * if gcc>= 4.5, with the new -mmcount-ra-address option, for a
 234          * non-leaf function, the location of the return address will be saved
 235          * to $12 for us, and for a leaf function, only put a zero into $12. we
 236          * do it in ftrace_graph_caller of mcount.S.
 237          */
 238
 239         /* old = *parent; */
 240         safe_load_stack(old, parent, faulted);
 241         if (unlikely(faulted))
 242                 goto out;
 243 #ifndef KBUILD_MCOUNT_RA_ADDRESS
 244         parent = (unsigned long *)ftrace_get_parent_addr(self_addr, old,
 245                                                          (unsigned long)parent,
 246                                                          fp);
 247         /* If fails when getting the stack address of the non-leaf function's
 248          * ra, stop function graph tracer and return */
 249         if (parent == 0)
 250                 goto out;
 251 #endif
 252         /* *parent = return_hooker; */
 253         safe_store_stack(return_hooker, parent, faulted);
 254         if (unlikely(faulted))
 255                 goto out;
 256
 257         if (ftrace_push_return_trace(old, self_addr, &trace.depth, fp) ==
 258             -EBUSY) {
 259                 *parent = old;
 260                 return;
 261         }
 262
 263         trace.func = self_addr;
 264
 265         /* Only trace if the calling function expects to */
 266         if (!ftrace_graph_entry(&trace)) {
 267                 current->curr_ret_stack--;
 268                 *parent = old;
 269         }
 270         return;
 271 out:
 272         ftrace_graph_stop();
 273         WARN_ON(1);
 274 }
 275 #endif                          /* CONFIG_FUNCTION_GRAPH_TRACER */