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 #include <linux/syscalls.h>
  15
  16 #include <asm/asm.h>
  17 #include <asm/asm-offsets.h>
  18 #include <asm/cacheflush.h>
  19 #include <asm/syscall.h>
  20 #include <asm/uasm.h>
  21 #include <asm/unistd.h>
  22
  23 #include <asm-generic/sections.h>
  24
  25 #if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT)
  26 #define MCOUNT_OFFSET_INSNS 5
  27 #else
  28 #define MCOUNT_OFFSET_INSNS 4
  29 #endif
  30
  31 #ifdef CONFIG_DYNAMIC_FTRACE
  32
  33 /* Arch override because MIPS doesn't need to run this from stop_machine() */
  34 void arch_ftrace_update_code(int command)
  35 {
  36         ftrace_modify_all_code(command);
  37 }
  38
  39 #endif
  40
  41 /*
  42  * Check if the address is in kernel space
  43  *
  44  * Clone core_kernel_text() from kernel/extable.c, but doesn't call
  45  * init_kernel_text() for Ftrace doesn't trace functions in init sections.
  46  */
  47 static inline int in_kernel_space(unsigned long ip)
  48 {
  49         if (ip >= (unsigned long)_stext &&
  50             ip <= (unsigned long)_etext)
  51                 return 1;
  52         return 0;
  53 }
  54
  55 #ifdef CONFIG_DYNAMIC_FTRACE
  56
  57 #define JAL 0x0c000000          /* jump & link: ip --> ra, jump to target */
  58 #define ADDR_MASK 0x03ffffff    /*  op_code|addr : 31...26|25 ....0 */
  59 #define JUMP_RANGE_MASK ((1UL << 28) - 1)
  60
  61 #define INSN_NOP 0x00000000     /* nop */
  62 #define INSN_JAL(addr)  \
  63         ((unsigned int)(JAL | (((addr) >> 2) & ADDR_MASK)))
  64
  65 static unsigned int insn_jal_ftrace_caller __read_mostly;
  66 static unsigned int insn_la_mcount[2] __read_mostly;
  67 static unsigned int insn_j_ftrace_graph_caller __maybe_unused __read_mostly;
  68
  69 static inline void ftrace_dyn_arch_init_insns(void)
  70 {
  71         u32 *buf;
  72         unsigned int v1;
  73
  74         /* la v1, _mcount */
  75         v1 = 3;
  76         buf = (u32 *)&insn_la_mcount[0];
  77         UASM_i_LA(&buf, v1, MCOUNT_ADDR);
  78
  79         /* jal (ftrace_caller + 8), jump over the first two instruction */
  80         buf = (u32 *)&insn_jal_ftrace_caller;
  81         uasm_i_jal(&buf, (FTRACE_ADDR + 8) & JUMP_RANGE_MASK);
  82
  83 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
  84         /* j ftrace_graph_caller */
  85         buf = (u32 *)&insn_j_ftrace_graph_caller;
  86         uasm_i_j(&buf, (unsigned long)ftrace_graph_caller & JUMP_RANGE_MASK);
  87 #endif
  88 }
  89
  90 static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
  91 {
  92         int faulted;
  93         mm_segment_t old_fs;
  94
  95         /* *(unsigned int *)ip = new_code; */
  96         safe_store_code(new_code, ip, faulted);
  97
  98         if (unlikely(faulted))
  99                 return -EFAULT;
 100
 101         old_fs = get_fs();
 102         set_fs(get_ds());
 103         flush_icache_range(ip, ip + 8);
 104         set_fs(old_fs);
 105
 106         return 0;
 107 }
 108
 109 #ifndef CONFIG_64BIT
 110 static int ftrace_modify_code_2(unsigned long ip, unsigned int new_code1,
 111                                 unsigned int new_code2)
 112 {
 113         int faulted;
 114         mm_segment_t old_fs;
 115
 116         safe_store_code(new_code1, ip, faulted);
 117         if (unlikely(faulted))
 118                 return -EFAULT;
 119
 120         ip += 4;
 121         safe_store_code(new_code2, ip, faulted);
 122         if (unlikely(faulted))
 123                 return -EFAULT;
 124
 125         ip -= 4;
 126         old_fs = get_fs();
 127         set_fs(get_ds());
 128         flush_icache_range(ip, ip + 8);
 129         set_fs(old_fs);
 130
 131         return 0;
 132 }
 133
 134 static int ftrace_modify_code_2r(unsigned long ip, unsigned int new_code1,
 135                                  unsigned int new_code2)
 136 {
 137         int faulted;
 138         mm_segment_t old_fs;
 139
 140         ip += 4;
 141         safe_store_code(new_code2, ip, faulted);
 142         if (unlikely(faulted))
 143                 return -EFAULT;
 144
 145         ip -= 4;
 146         safe_store_code(new_code1, ip, faulted);
 147         if (unlikely(faulted))
 148                 return -EFAULT;
 149
 150         old_fs = get_fs();
 151         set_fs(get_ds());
 152         flush_icache_range(ip, ip + 8);
 153         set_fs(old_fs);
 154
 155         return 0;
 156 }
 157 #endif
 158
 159 /*
 160  * The details about the calling site of mcount on MIPS
 161  *
 162  * 1. For kernel:
 163  *
 164  * move at, ra
 165  * jal _mcount          --> nop
 166  *  sub sp, sp, 8       --> nop  (CONFIG_32BIT)
 167  *
 168  * 2. For modules:
 169  *
 170  * 2.1 For KBUILD_MCOUNT_RA_ADDRESS and CONFIG_32BIT
 171  *
 172  * lui v1, hi_16bit_of_mcount        --> b 1f (0x10000005)
 173  * addiu v1, v1, low_16bit_of_mcount --> nop  (CONFIG_32BIT)
 174  * move at, ra
 175  * move $12, ra_address
 176  * jalr v1
 177  *  sub sp, sp, 8
 178  *                                  1: offset = 5 instructions
 179  * 2.2 For the Other situations
 180  *
 181  * lui v1, hi_16bit_of_mcount        --> b 1f (0x10000004)
 182  * addiu v1, v1, low_16bit_of_mcount --> nop  (CONFIG_32BIT)
 183  * move at, ra
 184  * jalr v1
 185  *  nop | move $12, ra_address | sub sp, sp, 8
 186  *                                  1: offset = 4 instructions
 187  */
 188
 189 #define INSN_B_1F (0x10000000 | MCOUNT_OFFSET_INSNS)
 190
 191 int ftrace_make_nop(struct module *mod,
 192                     struct dyn_ftrace *rec, unsigned long addr)
 193 {
 194         unsigned int new;
 195         unsigned long ip = rec->ip;
 196
 197         /*
 198          * If ip is in kernel space, no long call, otherwise, long call is
 199          * needed.
 200          */
 201         new = in_kernel_space(ip) ? INSN_NOP : INSN_B_1F;
 202 #ifdef CONFIG_64BIT
 203         return ftrace_modify_code(ip, new);
 204 #else
 205         /*
 206          * On 32 bit MIPS platforms, gcc adds a stack adjust
 207          * instruction in the delay slot after the branch to
 208          * mcount and expects mcount to restore the sp on return.
 209          * This is based on a legacy API and does nothing but
 210          * waste instructions so it's being removed at runtime.
 211          */
 212         return ftrace_modify_code_2(ip, new, INSN_NOP);
 213 #endif
 214 }
 215
 216 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 217 {
 218         unsigned int new;
 219         unsigned long ip = rec->ip;
 220
 221         new = in_kernel_space(ip) ? insn_jal_ftrace_caller : insn_la_mcount[0];
 222
 223 #ifdef CONFIG_64BIT
 224         return ftrace_modify_code(ip, new);
 225 #else
 226         return ftrace_modify_code_2r(ip, new, in_kernel_space(ip) ?
 227                                                 INSN_NOP : insn_la_mcount[1]);
 228 #endif
 229 }
 230
 231 #define FTRACE_CALL_IP ((unsigned long)(&ftrace_call))
 232
 233 int ftrace_update_ftrace_func(ftrace_func_t func)
 234 {
 235         unsigned int new;
 236
 237         new = INSN_JAL((unsigned long)func);
 238
 239         return ftrace_modify_code(FTRACE_CALL_IP, new);
 240 }
 241
 242 int __init ftrace_dyn_arch_init(void)
 243 {
 244         /* Encode the instructions when booting */
 245         ftrace_dyn_arch_init_insns();
 246
 247         /* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */
 248         ftrace_modify_code(MCOUNT_ADDR, INSN_NOP);
 249
 250         return 0;
 251 }
 252 #endif  /* CONFIG_DYNAMIC_FTRACE */
 253
 254 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 255
 256 #ifdef CONFIG_DYNAMIC_FTRACE
 257
 258 extern void ftrace_graph_call(void);
 259 #define FTRACE_GRAPH_CALL_IP    ((unsigned long)(&ftrace_graph_call))
 260
 261 int ftrace_enable_ftrace_graph_caller(void)
 262 {
 263         return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
 264                         insn_j_ftrace_graph_caller);
 265 }
 266
 267 int ftrace_disable_ftrace_graph_caller(void)
 268 {
 269         return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP);
 270 }
 271
 272 #endif  /* CONFIG_DYNAMIC_FTRACE */
 273
 274 #ifndef KBUILD_MCOUNT_RA_ADDRESS
 275
 276 #define S_RA_SP (0xafbf << 16)  /* s{d,w} ra, offset(sp) */
 277 #define S_R_SP  (0xafb0 << 16)  /* s{d,w} R, offset(sp) */
 278 #define OFFSET_MASK     0xffff  /* stack offset range: 0 ~ PT_SIZE */
 279
 280 unsigned long ftrace_get_parent_ra_addr(unsigned long self_ra, unsigned long
 281                 old_parent_ra, unsigned long parent_ra_addr, unsigned long fp)
 282 {
 283         unsigned long sp, ip, tmp;
 284         unsigned int code;
 285         int faulted;
 286
 287         /*
 288          * For module, move the ip from the return address after the
 289          * instruction "lui v1, hi_16bit_of_mcount"(offset is 24), but for
 290          * kernel, move after the instruction "move ra, at"(offset is 16)
 291          */
 292         ip = self_ra - (in_kernel_space(self_ra) ? 16 : 24);
 293
 294         /*
 295          * search the text until finding the non-store instruction or "s{d,w}
 296          * ra, offset(sp)" instruction
 297          */
 298         do {
 299                 /* get the code at "ip": code = *(unsigned int *)ip; */
 300                 safe_load_code(code, ip, faulted);
 301
 302                 if (unlikely(faulted))
 303                         return 0;
 304                 /*
 305                  * If we hit the non-store instruction before finding where the
 306                  * ra is stored, then this is a leaf function and it does not
 307                  * store the ra on the stack
 308                  */
 309                 if ((code & S_R_SP) != S_R_SP)
 310                         return parent_ra_addr;
 311
 312                 /* Move to the next instruction */
 313                 ip -= 4;
 314         } while ((code & S_RA_SP) != S_RA_SP);
 315
 316         sp = fp + (code & OFFSET_MASK);
 317
 318         /* tmp = *(unsigned long *)sp; */
 319         safe_load_stack(tmp, sp, faulted);
 320         if (unlikely(faulted))
 321                 return 0;
 322
 323         if (tmp == old_parent_ra)
 324                 return sp;
 325         return 0;
 326 }
 327
 328 #endif  /* !KBUILD_MCOUNT_RA_ADDRESS */
 329
 330 /*
 331  * Hook the return address and push it in the stack of return addrs
 332  * in current thread info.
 333  */
 334 void prepare_ftrace_return(unsigned long *parent_ra_addr, unsigned long self_ra,
 335                            unsigned long fp)
 336 {
 337         unsigned long old_parent_ra;
 338         struct ftrace_graph_ent trace;
 339         unsigned long return_hooker = (unsigned long)
 340             &return_to_handler;
 341         int faulted, insns;
 342
 343         if (unlikely(ftrace_graph_is_dead()))
 344                 return;
 345
 346         if (unlikely(atomic_read(&current->tracing_graph_pause)))
 347                 return;
 348
 349         /*
 350          * "parent_ra_addr" is the stack address saved the return address of
 351          * the caller of _mcount.
 352          *
 353          * if the gcc < 4.5, a leaf function does not save the return address
 354          * in the stack address, so, we "emulate" one in _mcount's stack space,
 355          * and hijack it directly, but for a non-leaf function, it save the
 356          * return address to the its own stack space, we can not hijack it
 357          * directly, but need to find the real stack address,
 358          * ftrace_get_parent_addr() does it!
 359          *
 360          * if gcc>= 4.5, with the new -mmcount-ra-address option, for a
 361          * non-leaf function, the location of the return address will be saved
 362          * to $12 for us, and for a leaf function, only put a zero into $12. we
 363          * do it in ftrace_graph_caller of mcount.S.
 364          */
 365
 366         /* old_parent_ra = *parent_ra_addr; */
 367         safe_load_stack(old_parent_ra, parent_ra_addr, faulted);
 368         if (unlikely(faulted))
 369                 goto out;
 370 #ifndef KBUILD_MCOUNT_RA_ADDRESS
 371         parent_ra_addr = (unsigned long *)ftrace_get_parent_ra_addr(self_ra,
 372                         old_parent_ra, (unsigned long)parent_ra_addr, fp);
 373         /*
 374          * If fails when getting the stack address of the non-leaf function's
 375          * ra, stop function graph tracer and return
 376          */
 377         if (parent_ra_addr == 0)
 378                 goto out;
 379 #endif
 380         /* *parent_ra_addr = return_hooker; */
 381         safe_store_stack(return_hooker, parent_ra_addr, faulted);
 382         if (unlikely(faulted))
 383                 goto out;
 384
 385         if (ftrace_push_return_trace(old_parent_ra, self_ra, &trace.depth, fp)
 386             == -EBUSY) {
 387                 *parent_ra_addr = old_parent_ra;
 388                 return;
 389         }
 390
 391         /*
 392          * Get the recorded ip of the current mcount calling site in the
 393          * __mcount_loc section, which will be used to filter the function
 394          * entries configured through the tracing/set_graph_function interface.
 395          */
 396
 397         insns = in_kernel_space(self_ra) ? 2 : MCOUNT_OFFSET_INSNS + 1;
 398         trace.func = self_ra - (MCOUNT_INSN_SIZE * insns);
 399
 400         /* Only trace if the calling function expects to */
 401         if (!ftrace_graph_entry(&trace)) {
 402                 current->curr_ret_stack--;
 403                 *parent_ra_addr = old_parent_ra;
 404         }
 405         return;
 406 out:
 407         ftrace_graph_stop();
 408         WARN_ON(1);
 409 }
 410 #endif  /* CONFIG_FUNCTION_GRAPH_TRACER */
 411
 412 #ifdef CONFIG_FTRACE_SYSCALLS
 413
 414 #ifdef CONFIG_32BIT
 415 unsigned long __init arch_syscall_addr(int nr)
 416 {
 417         return (unsigned long)sys_call_table[nr - __NR_O32_Linux];
 418 }
 419 #endif
 420
 421 #ifdef CONFIG_64BIT
 422
 423 unsigned long __init arch_syscall_addr(int nr)
 424 {
 425 #ifdef CONFIG_MIPS32_N32
 426         if (nr >= __NR_N32_Linux && nr <= __NR_N32_Linux + __NR_N32_Linux_syscalls)
 427                 return (unsigned long)sysn32_call_table[nr - __NR_N32_Linux];
 428 #endif
 429         if (nr >= __NR_64_Linux  && nr <= __NR_64_Linux + __NR_64_Linux_syscalls)
 430                 return (unsigned long)sys_call_table[nr - __NR_64_Linux];
 431 #ifdef CONFIG_MIPS32_O32
 432         if (nr >= __NR_O32_Linux && nr <= __NR_O32_Linux + __NR_O32_Linux_syscalls)
 433                 return (unsigned long)sys32_call_table[nr - __NR_O32_Linux];
 434 #endif
 435
 436         return (unsigned long) &sys_ni_syscall;
 437 }
 438 #endif
 439
 440 #endif /* CONFIG_FTRACE_SYSCALLS */