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 #include <asm-generic/sections.h>
  21
  22 #if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT)
  23 #define MCOUNT_OFFSET_INSNS 5
  24 #else
  25 #define MCOUNT_OFFSET_INSNS 4
  26 #endif
  27
  28 #ifdef CONFIG_DYNAMIC_FTRACE
  29
  30 /* Arch override because MIPS doesn't need to run this from stop_machine() */
  31 void arch_ftrace_update_code(int command)
  32 {
  33         ftrace_modify_all_code(command);
  34 }
  35
  36 #endif
  37
  38 /*
  39  * Check if the address is in kernel space
  40  *
  41  * Clone core_kernel_text() from kernel/extable.c, but doesn't call
  42  * init_kernel_text() for Ftrace doesn't trace functions in init sections.
  43  */
  44 static inline int in_kernel_space(unsigned long ip)
  45 {
  46         if (ip >= (unsigned long)_stext &&
  47             ip <= (unsigned long)_etext)
  48                 return 1;
  49         return 0;
  50 }
  51
  52 #ifdef CONFIG_DYNAMIC_FTRACE
  53
  54 #define JAL 0x0c000000          /* jump & link: ip --> ra, jump to target */
  55 #define ADDR_MASK 0x03ffffff    /*  op_code|addr : 31...26|25 ....0 */
  56 #define JUMP_RANGE_MASK ((1UL << 28) - 1)
  57
  58 #define INSN_NOP 0x00000000     /* nop */
  59 #define INSN_JAL(addr)  \
  60         ((unsigned int)(JAL | (((addr) >> 2) & ADDR_MASK)))
  61
  62 static unsigned int insn_jal_ftrace_caller __read_mostly;
  63 static unsigned int insn_lui_v1_hi16_mcount __read_mostly;
  64 static unsigned int insn_j_ftrace_graph_caller __maybe_unused __read_mostly;
  65
  66 static inline void ftrace_dyn_arch_init_insns(void)
  67 {
  68         u32 *buf;
  69         unsigned int v1;
  70
  71         /* lui v1, hi16_mcount */
  72         v1 = 3;
  73         buf = (u32 *)&insn_lui_v1_hi16_mcount;
  74         UASM_i_LA_mostly(&buf, v1, MCOUNT_ADDR);
  75
  76         /* jal (ftrace_caller + 8), jump over the first two instruction */
  77         buf = (u32 *)&insn_jal_ftrace_caller;
  78         uasm_i_jal(&buf, (FTRACE_ADDR + 8) & JUMP_RANGE_MASK);
  79
  80 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
  81         /* j ftrace_graph_caller */
  82         buf = (u32 *)&insn_j_ftrace_graph_caller;
  83         uasm_i_j(&buf, (unsigned long)ftrace_graph_caller & JUMP_RANGE_MASK);
  84 #endif
  85 }
  86
  87 static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
  88 {
  89         int faulted;
  90
  91         /* *(unsigned int *)ip = new_code; */
  92         safe_store_code(new_code, ip, faulted);
  93
  94         if (unlikely(faulted))
  95                 return -EFAULT;
  96
  97         flush_icache_range(ip, ip + 8);
  98
  99         return 0;
 100 }
 101
 102 #ifndef CONFIG_64BIT
 103 static int ftrace_modify_code_2(unsigned long ip, unsigned int new_code1,
 104                                 unsigned int new_code2)
 105 {
 106         int faulted;
 107
 108         safe_store_code(new_code1, ip, faulted);
 109         if (unlikely(faulted))
 110                 return -EFAULT;
 111         ip += 4;
 112         safe_store_code(new_code2, ip, faulted);
 113         if (unlikely(faulted))
 114                 return -EFAULT;
 115         flush_icache_range(ip, ip + 8); /* original ip + 12 */
 116         return 0;
 117 }
 118 #endif
 119
 120 /*
 121  * The details about the calling site of mcount on MIPS
 122  *
 123  * 1. For kernel:
 124  *
 125  * move at, ra
 126  * jal _mcount          --> nop
 127  *
 128  * 2. For modules:
 129  *
 130  * 2.1 For KBUILD_MCOUNT_RA_ADDRESS and CONFIG_32BIT
 131  *
 132  * lui v1, hi_16bit_of_mcount        --> b 1f (0x10000005)
 133  * addiu v1, v1, low_16bit_of_mcount
 134  * move at, ra
 135  * move $12, ra_address
 136  * jalr v1
 137  *  sub sp, sp, 8
 138  *                                  1: offset = 5 instructions
 139  * 2.2 For the Other situations
 140  *
 141  * lui v1, hi_16bit_of_mcount        --> b 1f (0x10000004)
 142  * addiu v1, v1, low_16bit_of_mcount
 143  * move at, ra
 144  * jalr v1
 145  *  nop | move $12, ra_address | sub sp, sp, 8
 146  *                                  1: offset = 4 instructions
 147  */
 148
 149 #define INSN_B_1F (0x10000000 | MCOUNT_OFFSET_INSNS)
 150
 151 int ftrace_make_nop(struct module *mod,
 152                     struct dyn_ftrace *rec, unsigned long addr)
 153 {
 154         unsigned int new;
 155         unsigned long ip = rec->ip;
 156
 157         /*
 158          * If ip is in kernel space, no long call, otherwise, long call is
 159          * needed.
 160          */
 161         new = in_kernel_space(ip) ? INSN_NOP : INSN_B_1F;
 162 #ifdef CONFIG_64BIT
 163         return ftrace_modify_code(ip, new);
 164 #else
 165         /*
 166          * On 32 bit MIPS platforms, gcc adds a stack adjust
 167          * instruction in the delay slot after the branch to
 168          * mcount and expects mcount to restore the sp on return.
 169          * This is based on a legacy API and does nothing but
 170          * waste instructions so it's being removed at runtime.
 171          */
 172         return ftrace_modify_code_2(ip, new, INSN_NOP);
 173 #endif
 174 }
 175
 176 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 177 {
 178         unsigned int new;
 179         unsigned long ip = rec->ip;
 180
 181         new = in_kernel_space(ip) ? insn_jal_ftrace_caller :
 182                 insn_lui_v1_hi16_mcount;
 183
 184         return ftrace_modify_code(ip, new);
 185 }
 186
 187 #define FTRACE_CALL_IP ((unsigned long)(&ftrace_call))
 188
 189 int ftrace_update_ftrace_func(ftrace_func_t func)
 190 {
 191         unsigned int new;
 192
 193         new = INSN_JAL((unsigned long)func);
 194
 195         return ftrace_modify_code(FTRACE_CALL_IP, new);
 196 }
 197
 198 int __init ftrace_dyn_arch_init(void *data)
 199 {
 200         /* Encode the instructions when booting */
 201         ftrace_dyn_arch_init_insns();
 202
 203         /* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */
 204         ftrace_modify_code(MCOUNT_ADDR, INSN_NOP);
 205
 206         /* The return code is retured via data */
 207         *(unsigned long *)data = 0;
 208
 209         return 0;
 210 }
 211 #endif  /* CONFIG_DYNAMIC_FTRACE */
 212
 213 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 214
 215 #ifdef CONFIG_DYNAMIC_FTRACE
 216
 217 extern void ftrace_graph_call(void);
 218 #define FTRACE_GRAPH_CALL_IP    ((unsigned long)(&ftrace_graph_call))
 219
 220 int ftrace_enable_ftrace_graph_caller(void)
 221 {
 222         return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
 223                         insn_j_ftrace_graph_caller);
 224 }
 225
 226 int ftrace_disable_ftrace_graph_caller(void)
 227 {
 228         return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP);
 229 }
 230
 231 #endif  /* CONFIG_DYNAMIC_FTRACE */
 232
 233 #ifndef KBUILD_MCOUNT_RA_ADDRESS
 234
 235 #define S_RA_SP (0xafbf << 16)  /* s{d,w} ra, offset(sp) */
 236 #define S_R_SP  (0xafb0 << 16)  /* s{d,w} R, offset(sp) */
 237 #define OFFSET_MASK     0xffff  /* stack offset range: 0 ~ PT_SIZE */
 238
 239 unsigned long ftrace_get_parent_ra_addr(unsigned long self_ra, unsigned long
 240                 old_parent_ra, unsigned long parent_ra_addr, unsigned long fp)
 241 {
 242         unsigned long sp, ip, tmp;
 243         unsigned int code;
 244         int faulted;
 245
 246         /*
 247          * For module, move the ip from the return address after the
 248          * instruction "lui v1, hi_16bit_of_mcount"(offset is 24), but for
 249          * kernel, move after the instruction "move ra, at"(offset is 16)
 250          */
 251         ip = self_ra - (in_kernel_space(self_ra) ? 16 : 24);
 252
 253         /*
 254          * search the text until finding the non-store instruction or "s{d,w}
 255          * ra, offset(sp)" instruction
 256          */
 257         do {
 258                 /* get the code at "ip": code = *(unsigned int *)ip; */
 259                 safe_load_code(code, ip, faulted);
 260
 261                 if (unlikely(faulted))
 262                         return 0;
 263                 /*
 264                  * If we hit the non-store instruction before finding where the
 265                  * ra is stored, then this is a leaf function and it does not
 266                  * store the ra on the stack
 267                  */
 268                 if ((code & S_R_SP) != S_R_SP)
 269                         return parent_ra_addr;
 270
 271                 /* Move to the next instruction */
 272                 ip -= 4;
 273         } while ((code & S_RA_SP) != S_RA_SP);
 274
 275         sp = fp + (code & OFFSET_MASK);
 276
 277         /* tmp = *(unsigned long *)sp; */
 278         safe_load_stack(tmp, sp, faulted);
 279         if (unlikely(faulted))
 280                 return 0;
 281
 282         if (tmp == old_parent_ra)
 283                 return sp;
 284         return 0;
 285 }
 286
 287 #endif  /* !KBUILD_MCOUNT_RA_ADDRESS */
 288
 289 /*
 290  * Hook the return address and push it in the stack of return addrs
 291  * in current thread info.
 292  */
 293 void prepare_ftrace_return(unsigned long *parent_ra_addr, unsigned long self_ra,
 294                            unsigned long fp)
 295 {
 296         unsigned long old_parent_ra;
 297         struct ftrace_graph_ent trace;
 298         unsigned long return_hooker = (unsigned long)
 299             &return_to_handler;
 300         int faulted, insns;
 301
 302         if (unlikely(atomic_read(&current->tracing_graph_pause)))
 303                 return;
 304
 305         /*
 306          * "parent_ra_addr" is the stack address saved the return address of
 307          * the caller of _mcount.
 308          *
 309          * if the gcc < 4.5, a leaf function does not save the return address
 310          * in the stack address, so, we "emulate" one in _mcount's stack space,
 311          * and hijack it directly, but for a non-leaf function, it save the
 312          * return address to the its own stack space, we can not hijack it
 313          * directly, but need to find the real stack address,
 314          * ftrace_get_parent_addr() does it!
 315          *
 316          * if gcc>= 4.5, with the new -mmcount-ra-address option, for a
 317          * non-leaf function, the location of the return address will be saved
 318          * to $12 for us, and for a leaf function, only put a zero into $12. we
 319          * do it in ftrace_graph_caller of mcount.S.
 320          */
 321
 322         /* old_parent_ra = *parent_ra_addr; */
 323         safe_load_stack(old_parent_ra, parent_ra_addr, faulted);
 324         if (unlikely(faulted))
 325                 goto out;
 326 #ifndef KBUILD_MCOUNT_RA_ADDRESS
 327         parent_ra_addr = (unsigned long *)ftrace_get_parent_ra_addr(self_ra,
 328                         old_parent_ra, (unsigned long)parent_ra_addr, fp);
 329         /*
 330          * If fails when getting the stack address of the non-leaf function's
 331          * ra, stop function graph tracer and return
 332          */
 333         if (parent_ra_addr == 0)
 334                 goto out;
 335 #endif
 336         /* *parent_ra_addr = return_hooker; */
 337         safe_store_stack(return_hooker, parent_ra_addr, faulted);
 338         if (unlikely(faulted))
 339                 goto out;
 340
 341         if (ftrace_push_return_trace(old_parent_ra, self_ra, &trace.depth, fp)
 342             == -EBUSY) {
 343                 *parent_ra_addr = old_parent_ra;
 344                 return;
 345         }
 346
 347         /*
 348          * Get the recorded ip of the current mcount calling site in the
 349          * __mcount_loc section, which will be used to filter the function
 350          * entries configured through the tracing/set_graph_function interface.
 351          */
 352
 353         insns = in_kernel_space(self_ra) ? 2 : MCOUNT_OFFSET_INSNS + 1;
 354         trace.func = self_ra - (MCOUNT_INSN_SIZE * insns);
 355
 356         /* Only trace if the calling function expects to */
 357         if (!ftrace_graph_entry(&trace)) {
 358                 current->curr_ret_stack--;
 359                 *parent_ra_addr = old_parent_ra;
 360         }
 361         return;
 362 out:
 363         ftrace_graph_stop();
 364         WARN_ON(1);
 365 }
 366 #endif  /* CONFIG_FUNCTION_GRAPH_TRACER */