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  * If the Instruction Pointer is in module space (0xc0000000), return true;
  22  * otherwise, it is in kernel space (0x80000000), return false.
  23  *
  24  * FIXME: This will not work when the kernel space and module space are the
  25  * same. If they are the same, we need to modify scripts/recordmcount.pl,
  26  * ftrace_make_nop/call() and the other related parts to ensure the
  27  * enabling/disabling of the calling site to _mcount is right for both kernel
  28  * and module.
  29  */
  30
  31 static inline int in_module(unsigned long ip)
  32 {
  33         return ip & 0x40000000;
  34 }
  35
  36 #ifdef CONFIG_DYNAMIC_FTRACE
  37
  38 #define JAL 0x0c000000          /* jump & link: ip --> ra, jump to target */
  39 #define ADDR_MASK 0x03ffffff    /*  op_code|addr : 31...26|25 ....0 */
  40
  41 #define INSN_B_1F_4 0x10000004  /* b 1f; offset = 4 */
  42 #define INSN_B_1F_5 0x10000005  /* b 1f; offset = 5 */
  43 #define INSN_NOP 0x00000000     /* nop */
  44 #define INSN_JAL(addr)  \
  45         ((unsigned int)(JAL | (((addr) >> 2) & ADDR_MASK)))
  46
  47 static unsigned int insn_jal_ftrace_caller __read_mostly;
  48 static unsigned int insn_lui_v1_hi16_mcount __read_mostly;
  49 static unsigned int insn_j_ftrace_graph_caller __maybe_unused __read_mostly;
  50
  51 static inline void ftrace_dyn_arch_init_insns(void)
  52 {
  53         u32 *buf;
  54         unsigned int v1;
  55
  56         /* lui v1, hi16_mcount */
  57         v1 = 3;
  58         buf = (u32 *)&insn_lui_v1_hi16_mcount;
  59         UASM_i_LA_mostly(&buf, v1, MCOUNT_ADDR);
  60
  61         /* jal (ftrace_caller + 8), jump over the first two instruction */
  62         buf = (u32 *)&insn_jal_ftrace_caller;
  63         uasm_i_jal(&buf, (FTRACE_ADDR + 8));
  64
  65 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
  66         /* j ftrace_graph_caller */
  67         buf = (u32 *)&insn_j_ftrace_graph_caller;
  68         uasm_i_j(&buf, (unsigned long)ftrace_graph_caller);
  69 #endif
  70 }
  71
  72 static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
  73 {
  74         int faulted;
  75
  76         /* *(unsigned int *)ip = new_code; */
  77         safe_store_code(new_code, ip, faulted);
  78
  79         if (unlikely(faulted))
  80                 return -EFAULT;
  81
  82         flush_icache_range(ip, ip + 8);
  83
  84         return 0;
  85 }
  86
  87 int ftrace_make_nop(struct module *mod,
  88                     struct dyn_ftrace *rec, unsigned long addr)
  89 {
  90         unsigned int new;
  91         unsigned long ip = rec->ip;
  92
  93         /*
  94          * We have compiled module with -mlong-calls, but compiled the kernel
  95          * without it, we need to cope with them respectively.
  96          */
  97         if (in_module(ip)) {
  98 #if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT)
  99                 /*
 100                  * lui v1, hi_16bit_of_mcount        --> b 1f (0x10000005)
 101                  * addiu v1, v1, low_16bit_of_mcount
 102                  * move at, ra
 103                  * move $12, ra_address
 104                  * jalr v1
 105                  *  sub sp, sp, 8
 106                  *                                  1: offset = 5 instructions
 107                  */
 108                 new = INSN_B_1F_5;
 109 #else
 110                 /*
 111                  * lui v1, hi_16bit_of_mcount        --> b 1f (0x10000004)
 112                  * addiu v1, v1, low_16bit_of_mcount
 113                  * move at, ra
 114                  * jalr v1
 115                  *  nop | move $12, ra_address | sub sp, sp, 8
 116                  *                                  1: offset = 4 instructions
 117                  */
 118                 new = INSN_B_1F_4;
 119 #endif
 120         } else {
 121                 /*
 122                  * move at, ra
 123                  * jal _mcount          --> nop
 124                  */
 125                 new = INSN_NOP;
 126         }
 127         return ftrace_modify_code(ip, new);
 128 }
 129
 130 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 131 {
 132         unsigned int new;
 133         unsigned long ip = rec->ip;
 134
 135         /* ip, module: 0xc0000000, kernel: 0x80000000 */
 136         new = in_module(ip) ? insn_lui_v1_hi16_mcount : insn_jal_ftrace_caller;
 137
 138         return ftrace_modify_code(ip, new);
 139 }
 140
 141 #define FTRACE_CALL_IP ((unsigned long)(&ftrace_call))
 142
 143 int ftrace_update_ftrace_func(ftrace_func_t func)
 144 {
 145         unsigned int new;
 146
 147         new = INSN_JAL((unsigned long)func);
 148
 149         return ftrace_modify_code(FTRACE_CALL_IP, new);
 150 }
 151
 152 int __init ftrace_dyn_arch_init(void *data)
 153 {
 154         /* Encode the instructions when booting */
 155         ftrace_dyn_arch_init_insns();
 156
 157         /* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */
 158         ftrace_modify_code(MCOUNT_ADDR, INSN_NOP);
 159
 160         /* The return code is retured via data */
 161         *(unsigned long *)data = 0;
 162
 163         return 0;
 164 }
 165 #endif  /* CONFIG_DYNAMIC_FTRACE */
 166
 167 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 168
 169 #ifdef CONFIG_DYNAMIC_FTRACE
 170
 171 extern void ftrace_graph_call(void);
 172 #define FTRACE_GRAPH_CALL_IP    ((unsigned long)(&ftrace_graph_call))
 173
 174 int ftrace_enable_ftrace_graph_caller(void)
 175 {
 176         return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
 177                         insn_j_ftrace_graph_caller);
 178 }
 179
 180 int ftrace_disable_ftrace_graph_caller(void)
 181 {
 182         return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP);
 183 }
 184
 185 #endif  /* CONFIG_DYNAMIC_FTRACE */
 186
 187 #ifndef KBUILD_MCOUNT_RA_ADDRESS
 188
 189 #define S_RA_SP (0xafbf << 16)  /* s{d,w} ra, offset(sp) */
 190 #define S_R_SP  (0xafb0 << 16)  /* s{d,w} R, offset(sp) */
 191 #define OFFSET_MASK     0xffff  /* stack offset range: 0 ~ PT_SIZE */
 192
 193 unsigned long ftrace_get_parent_addr(unsigned long self_addr,
 194                                      unsigned long parent,
 195                                      unsigned long parent_addr,
 196                                      unsigned long fp)
 197 {
 198         unsigned long sp, ip, ra;
 199         unsigned int code;
 200         int faulted;
 201
 202         /*
 203          * For module, move the ip from calling site of mcount to the
 204          * instruction "lui v1, hi_16bit_of_mcount"(offset is 20), but for
 205          * kernel, move to the instruction "move ra, at"(offset is 12)
 206          */
 207         ip = self_addr - (in_module(self_addr) ? 20 : 12);
 208
 209         /*
 210          * search the text until finding the non-store instruction or "s{d,w}
 211          * ra, offset(sp)" instruction
 212          */
 213         do {
 214                 ip -= 4;
 215
 216                 /* get the code at "ip": code = *(unsigned int *)ip; */
 217                 safe_load_code(code, ip, faulted);
 218
 219                 if (unlikely(faulted))
 220                         return 0;
 221                 /*
 222                  * If we hit the non-store instruction before finding where the
 223                  * ra is stored, then this is a leaf function and it does not
 224                  * store the ra on the stack
 225                  */
 226                 if ((code & S_R_SP) != S_R_SP)
 227                         return parent_addr;
 228
 229         } while (((code & S_RA_SP) != S_RA_SP));
 230
 231         sp = fp + (code & OFFSET_MASK);
 232
 233         /* ra = *(unsigned long *)sp; */
 234         safe_load_stack(ra, sp, faulted);
 235         if (unlikely(faulted))
 236                 return 0;
 237
 238         if (ra == parent)
 239                 return sp;
 240         return 0;
 241 }
 242
 243 #endif  /* !KBUILD_MCOUNT_RA_ADDRESS */
 244
 245 /*
 246  * Hook the return address and push it in the stack of return addrs
 247  * in current thread info.
 248  */
 249 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
 250                            unsigned long fp)
 251 {
 252         unsigned long old;
 253         struct ftrace_graph_ent trace;
 254         unsigned long return_hooker = (unsigned long)
 255             &return_to_handler;
 256         int faulted;
 257
 258         if (unlikely(atomic_read(&current->tracing_graph_pause)))
 259                 return;
 260
 261         /*
 262          * "parent" is the stack address saved the return address of the caller
 263          * of _mcount.
 264          *
 265          * if the gcc < 4.5, a leaf function does not save the return address
 266          * in the stack address, so, we "emulate" one in _mcount's stack space,
 267          * and hijack it directly, but for a non-leaf function, it save the
 268          * return address to the its own stack space, we can not hijack it
 269          * directly, but need to find the real stack address,
 270          * ftrace_get_parent_addr() does it!
 271          *
 272          * if gcc>= 4.5, with the new -mmcount-ra-address option, for a
 273          * non-leaf function, the location of the return address will be saved
 274          * to $12 for us, and for a leaf function, only put a zero into $12. we
 275          * do it in ftrace_graph_caller of mcount.S.
 276          */
 277
 278         /* old = *parent; */
 279         safe_load_stack(old, parent, faulted);
 280         if (unlikely(faulted))
 281                 goto out;
 282 #ifndef KBUILD_MCOUNT_RA_ADDRESS
 283         parent = (unsigned long *)ftrace_get_parent_addr(self_addr, old,
 284                         (unsigned long)parent, fp);
 285         /*
 286          * If fails when getting the stack address of the non-leaf function's
 287          * ra, stop function graph tracer and return
 288          */
 289         if (parent == 0)
 290                 goto out;
 291 #endif
 292         /* *parent = return_hooker; */
 293         safe_store_stack(return_hooker, parent, faulted);
 294         if (unlikely(faulted))
 295                 goto out;
 296
 297         if (ftrace_push_return_trace(old, self_addr, &trace.depth, fp) ==
 298             -EBUSY) {
 299                 *parent = old;
 300                 return;
 301         }
 302
 303         trace.func = self_addr;
 304
 305         /* Only trace if the calling function expects to */
 306         if (!ftrace_graph_entry(&trace)) {
 307                 current->curr_ret_stack--;
 308                 *parent = old;
 309         }
 310         return;
 311 out:
 312         ftrace_graph_stop();
 313         WARN_ON(1);
 314 }
 315 #endif  /* CONFIG_FUNCTION_GRAPH_TRACER */