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