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