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