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