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_lui_v1_hi16_mcount __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         /* lui v1, hi16_mcount */
  75         v1 = 3;
  76         buf = (u32 *)&insn_lui_v1_hi16_mcount;
  77         UASM_i_LA_mostly(&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
  94         /* *(unsigned int *)ip = new_code; */
  95         safe_store_code(new_code, ip, faulted);
  96
  97         if (unlikely(faulted))
  98                 return -EFAULT;
  99
 100         flush_icache_range(ip, ip + 8);
 101
 102         return 0;
 103 }
 104
 105 #ifndef CONFIG_64BIT
 106 static int ftrace_modify_code_2(unsigned long ip, unsigned int new_code1,
 107                                 unsigned int new_code2)
 108 {
 109         int faulted;
 110
 111         safe_store_code(new_code1, ip, faulted);
 112         if (unlikely(faulted))
 113                 return -EFAULT;
 114         safe_store_code(new_code2, ip + 4, faulted);
 115         if (unlikely(faulted))
 116                 return -EFAULT;
 117         flush_icache_range(ip, ip + 8);
 118         return 0;
 119 }
 120 #endif
 121
 122 /*
 123  * The details about the calling site of mcount on MIPS
 124  *
 125  * 1. For kernel:
 126  *
 127  * move at, ra
 128  * jal _mcount          --> nop
 129  *
 130  * 2. For modules:
 131  *
 132  * 2.1 For KBUILD_MCOUNT_RA_ADDRESS and CONFIG_32BIT
 133  *
 134  * lui v1, hi_16bit_of_mcount        --> b 1f (0x10000005)
 135  * addiu v1, v1, low_16bit_of_mcount
 136  * move at, ra
 137  * move $12, ra_address
 138  * jalr v1
 139  *  sub sp, sp, 8
 140  *                                  1: offset = 5 instructions
 141  * 2.2 For the Other situations
 142  *
 143  * lui v1, hi_16bit_of_mcount        --> b 1f (0x10000004)
 144  * addiu v1, v1, low_16bit_of_mcount
 145  * move at, ra
 146  * jalr v1
 147  *  nop | move $12, ra_address | sub sp, sp, 8
 148  *                                  1: offset = 4 instructions
 149  */
 150
 151 #define INSN_B_1F (0x10000000 | MCOUNT_OFFSET_INSNS)
 152
 153 int ftrace_make_nop(struct module *mod,
 154                     struct dyn_ftrace *rec, unsigned long addr)
 155 {
 156         unsigned int new;
 157         unsigned long ip = rec->ip;
 158
 159         /*
 160          * If ip is in kernel space, no long call, otherwise, long call is
 161          * needed.
 162          */
 163         new = in_kernel_space(ip) ? INSN_NOP : INSN_B_1F;
 164 #ifdef CONFIG_64BIT
 165         return ftrace_modify_code(ip, new);
 166 #else
 167         /*
 168          * On 32 bit MIPS platforms, gcc adds a stack adjust
 169          * instruction in the delay slot after the branch to
 170          * mcount and expects mcount to restore the sp on return.
 171          * This is based on a legacy API and does nothing but
 172          * waste instructions so it's being removed at runtime.
 173          */
 174         return ftrace_modify_code_2(ip, new, INSN_NOP);
 175 #endif
 176 }
 177
 178 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 179 {
 180         unsigned int new;
 181         unsigned long ip = rec->ip;
 182
 183         new = in_kernel_space(ip) ? insn_jal_ftrace_caller :
 184                 insn_lui_v1_hi16_mcount;
 185
 186         return ftrace_modify_code(ip, new);
 187 }
 188
 189 #define FTRACE_CALL_IP ((unsigned long)(&ftrace_call))
 190
 191 int ftrace_update_ftrace_func(ftrace_func_t func)
 192 {
 193         unsigned int new;
 194
 195         new = INSN_JAL((unsigned long)func);
 196
 197         return ftrace_modify_code(FTRACE_CALL_IP, new);
 198 }
 199
 200 int __init ftrace_dyn_arch_init(void *data)
 201 {
 202         /* Encode the instructions when booting */
 203         ftrace_dyn_arch_init_insns();
 204
 205         /* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */
 206         ftrace_modify_code(MCOUNT_ADDR, INSN_NOP);
 207
 208         /* The return code is retured via data */
 209         *(unsigned long *)data = 0;
 210
 211         return 0;
 212 }
 213 #endif  /* CONFIG_DYNAMIC_FTRACE */
 214
 215 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 216
 217 #ifdef CONFIG_DYNAMIC_FTRACE
 218
 219 extern void ftrace_graph_call(void);
 220 #define FTRACE_GRAPH_CALL_IP    ((unsigned long)(&ftrace_graph_call))
 221
 222 int ftrace_enable_ftrace_graph_caller(void)
 223 {
 224         return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
 225                         insn_j_ftrace_graph_caller);
 226 }
 227
 228 int ftrace_disable_ftrace_graph_caller(void)
 229 {
 230         return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP);
 231 }
 232
 233 #endif  /* CONFIG_DYNAMIC_FTRACE */
 234
 235 #ifndef KBUILD_MCOUNT_RA_ADDRESS
 236
 237 #define S_RA_SP (0xafbf << 16)  /* s{d,w} ra, offset(sp) */
 238 #define S_R_SP  (0xafb0 << 16)  /* s{d,w} R, offset(sp) */
 239 #define OFFSET_MASK     0xffff  /* stack offset range: 0 ~ PT_SIZE */
 240
 241 unsigned long ftrace_get_parent_ra_addr(unsigned long self_ra, unsigned long
 242                 old_parent_ra, unsigned long parent_ra_addr, unsigned long fp)
 243 {
 244         unsigned long sp, ip, tmp;
 245         unsigned int code;
 246         int faulted;
 247
 248         /*
 249          * For module, move the ip from the return address after the
 250          * instruction "lui v1, hi_16bit_of_mcount"(offset is 24), but for
 251          * kernel, move after the instruction "move ra, at"(offset is 16)
 252          */
 253         ip = self_ra - (in_kernel_space(self_ra) ? 16 : 24);
 254
 255         /*
 256          * search the text until finding the non-store instruction or "s{d,w}
 257          * ra, offset(sp)" instruction
 258          */
 259         do {
 260                 /* get the code at "ip": code = *(unsigned int *)ip; */
 261                 safe_load_code(code, ip, faulted);
 262
 263                 if (unlikely(faulted))
 264                         return 0;
 265                 /*
 266                  * If we hit the non-store instruction before finding where the
 267                  * ra is stored, then this is a leaf function and it does not
 268                  * store the ra on the stack
 269                  */
 270                 if ((code & S_R_SP) != S_R_SP)
 271                         return parent_ra_addr;
 272
 273                 /* Move to the next instruction */
 274                 ip -= 4;
 275         } while ((code & S_RA_SP) != S_RA_SP);
 276
 277         sp = fp + (code & OFFSET_MASK);
 278
 279         /* tmp = *(unsigned long *)sp; */
 280         safe_load_stack(tmp, sp, faulted);
 281         if (unlikely(faulted))
 282                 return 0;
 283
 284         if (tmp == old_parent_ra)
 285                 return sp;
 286         return 0;
 287 }
 288
 289 #endif  /* !KBUILD_MCOUNT_RA_ADDRESS */
 290
 291 /*
 292  * Hook the return address and push it in the stack of return addrs
 293  * in current thread info.
 294  */
 295 void prepare_ftrace_return(unsigned long *parent_ra_addr, unsigned long self_ra,
 296                            unsigned long fp)
 297 {
 298         unsigned long old_parent_ra;
 299         struct ftrace_graph_ent trace;
 300         unsigned long return_hooker = (unsigned long)
 301             &return_to_handler;
 302         int faulted, insns;
 303
 304         if (unlikely(atomic_read(&current->tracing_graph_pause)))
 305                 return;
 306
 307         /*
 308          * "parent_ra_addr" is the stack address saved the return address of
 309          * the caller of _mcount.
 310          *
 311          * if the gcc < 4.5, a leaf function does not save the return address
 312          * in the stack address, so, we "emulate" one in _mcount's stack space,
 313          * and hijack it directly, but for a non-leaf function, it save the
 314          * return address to the its own stack space, we can not hijack it
 315          * directly, but need to find the real stack address,
 316          * ftrace_get_parent_addr() does it!
 317          *
 318          * if gcc>= 4.5, with the new -mmcount-ra-address option, for a
 319          * non-leaf function, the location of the return address will be saved
 320          * to $12 for us, and for a leaf function, only put a zero into $12. we
 321          * do it in ftrace_graph_caller of mcount.S.
 322          */
 323
 324         /* old_parent_ra = *parent_ra_addr; */
 325         safe_load_stack(old_parent_ra, parent_ra_addr, faulted);
 326         if (unlikely(faulted))
 327                 goto out;
 328 #ifndef KBUILD_MCOUNT_RA_ADDRESS
 329         parent_ra_addr = (unsigned long *)ftrace_get_parent_ra_addr(self_ra,
 330                         old_parent_ra, (unsigned long)parent_ra_addr, fp);
 331         /*
 332          * If fails when getting the stack address of the non-leaf function's
 333          * ra, stop function graph tracer and return
 334          */
 335         if (parent_ra_addr == 0)
 336                 goto out;
 337 #endif
 338         /* *parent_ra_addr = return_hooker; */
 339         safe_store_stack(return_hooker, parent_ra_addr, faulted);
 340         if (unlikely(faulted))
 341                 goto out;
 342
 343         if (ftrace_push_return_trace(old_parent_ra, self_ra, &trace.depth, fp)
 344             == -EBUSY) {
 345                 *parent_ra_addr = old_parent_ra;
 346                 return;
 347         }
 348
 349         /*
 350          * Get the recorded ip of the current mcount calling site in the
 351          * __mcount_loc section, which will be used to filter the function
 352          * entries configured through the tracing/set_graph_function interface.
 353          */
 354
 355         insns = in_kernel_space(self_ra) ? 2 : MCOUNT_OFFSET_INSNS + 1;
 356         trace.func = self_ra - (MCOUNT_INSN_SIZE * insns);
 357
 358         /* Only trace if the calling function expects to */
 359         if (!ftrace_graph_entry(&trace)) {
 360                 current->curr_ret_stack--;
 361                 *parent_ra_addr = old_parent_ra;
 362         }
 363         return;
 364 out:
 365         ftrace_graph_stop();
 366         WARN_ON(1);
 367 }
 368 #endif  /* CONFIG_FUNCTION_GRAPH_TRACER */
 369
 370 #ifdef CONFIG_FTRACE_SYSCALLS
 371
 372 #ifdef CONFIG_32BIT
 373 unsigned long __init arch_syscall_addr(int nr)
 374 {
 375         return (unsigned long)sys_call_table[nr - __NR_O32_Linux];
 376 }
 377 #endif
 378
 379 #ifdef CONFIG_64BIT
 380
 381 unsigned long __init arch_syscall_addr(int nr)
 382 {
 383 #ifdef CONFIG_MIPS32_N32
 384         if (nr >= __NR_N32_Linux && nr <= __NR_N32_Linux + __NR_N32_Linux_syscalls)
 385                 return (unsigned long)sysn32_call_table[nr - __NR_N32_Linux];
 386 #endif
 387         if (nr >= __NR_64_Linux  && nr <= __NR_64_Linux + __NR_64_Linux_syscalls)
 388                 return (unsigned long)sys_call_table[nr - __NR_64_Linux];
 389 #ifdef CONFIG_MIPS32_O32
 390         if (nr >= __NR_O32_Linux && nr <= __NR_O32_Linux + __NR_O32_Linux_syscalls)
 391                 return (unsigned long)sys32_call_table[nr - __NR_O32_Linux];
 392 #endif
 393
 394         return (unsigned long) &sys_ni_syscall;
 395 }
 396 #endif
 397
 398 #endif /* CONFIG_FTRACE_SYSCALLS */