arch/mips/kernel/ftrace.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Code for replacing ftrace calls with jumps.
   4  *
   5  * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
   6  * Copyright (C) 2009, 2010 DSLab, Lanzhou University, China
   7  * Author: Wu Zhangjin <wuzhangjin@gmail.com>
   8  *
   9  * Thanks goes to Steven Rostedt for writing the original x86 version.
  10  */
  11
  12 #include <linux/uaccess.h>
  13 #include <linux/init.h>
  14 #include <linux/ftrace.h>
  15 #include <linux/syscalls.h>
  16
  17 #include <asm/asm.h>
  18 #include <asm/asm-offsets.h>
  19 #include <asm/cacheflush.h>
  20 #include <asm/syscall.h>
  21 #include <asm/uasm.h>
  22 #include <asm/unistd.h>
  23
  24 #include <asm-generic/sections.h>
  25
  26 #if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT)
  27 #define MCOUNT_OFFSET_INSNS 5
  28 #else
  29 #define MCOUNT_OFFSET_INSNS 4
  30 #endif
  31
  32 #ifdef CONFIG_DYNAMIC_FTRACE
  33
  34 /* Arch override because MIPS doesn't need to run this from stop_machine() */
  35 void arch_ftrace_update_code(int command)
  36 {
  37         ftrace_modify_all_code(command);
  38 }
  39
  40 #define JAL 0x0c000000          /* jump & link: ip --> ra, jump to target */
  41 #define ADDR_MASK 0x03ffffff    /*  op_code|addr : 31...26|25 ....0 */
  42 #define JUMP_RANGE_MASK ((1UL << 28) - 1)
  43
  44 #define INSN_NOP 0x00000000     /* nop */
  45 #define INSN_JAL(addr)  \
  46         ((unsigned int)(JAL | (((addr) >> 2) & ADDR_MASK)))
  47
  48 static unsigned int insn_jal_ftrace_caller __read_mostly;
  49 static unsigned int insn_la_mcount[2] __read_mostly;
  50 static unsigned int insn_j_ftrace_graph_caller __maybe_unused __read_mostly;
  51
  52 static inline void ftrace_dyn_arch_init_insns(void)
  53 {
  54         u32 *buf;
  55         unsigned int v1;
  56
  57         /* la v1, _mcount */
  58         v1 = 3;
  59         buf = (u32 *)&insn_la_mcount[0];
  60         UASM_i_LA(&buf, v1, MCOUNT_ADDR);
  61
  62         /* jal (ftrace_caller + 8), jump over the first two instruction */
  63         buf = (u32 *)&insn_jal_ftrace_caller;
  64         uasm_i_jal(&buf, (FTRACE_ADDR + 8) & JUMP_RANGE_MASK);
  65
  66 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
  67         /* j ftrace_graph_caller */
  68         buf = (u32 *)&insn_j_ftrace_graph_caller;
  69         uasm_i_j(&buf, (unsigned long)ftrace_graph_caller & JUMP_RANGE_MASK);
  70 #endif
  71 }
  72
  73 static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
  74 {
  75         int faulted;
  76         mm_segment_t old_fs;
  77
  78         /* *(unsigned int *)ip = new_code; */
  79         safe_store_code(new_code, ip, faulted);
  80
  81         if (unlikely(faulted))
  82                 return -EFAULT;
  83
  84         old_fs = get_fs();
  85         set_fs(KERNEL_DS);
  86         flush_icache_range(ip, ip + 8);
  87         set_fs(old_fs);
  88
  89         return 0;
  90 }
  91
  92 #ifndef CONFIG_64BIT
  93 static int ftrace_modify_code_2(unsigned long ip, unsigned int new_code1,
  94                                 unsigned int new_code2)
  95 {
  96         int faulted;
  97         mm_segment_t old_fs;
  98
  99         safe_store_code(new_code1, ip, faulted);
 100         if (unlikely(faulted))
 101                 return -EFAULT;
 102
 103         ip += 4;
 104         safe_store_code(new_code2, ip, faulted);
 105         if (unlikely(faulted))
 106                 return -EFAULT;
 107
 108         ip -= 4;
 109         old_fs = get_fs();
 110         set_fs(KERNEL_DS);
 111         flush_icache_range(ip, ip + 8);
 112         set_fs(old_fs);
 113
 114         return 0;
 115 }
 116
 117 static int ftrace_modify_code_2r(unsigned long ip, unsigned int new_code1,
 118                                  unsigned int new_code2)
 119 {
 120         int faulted;
 121         mm_segment_t old_fs;
 122
 123         ip += 4;
 124         safe_store_code(new_code2, ip, faulted);
 125         if (unlikely(faulted))
 126                 return -EFAULT;
 127
 128         ip -= 4;
 129         safe_store_code(new_code1, ip, faulted);
 130         if (unlikely(faulted))
 131                 return -EFAULT;
 132
 133         old_fs = get_fs();
 134         set_fs(KERNEL_DS);
 135         flush_icache_range(ip, ip + 8);
 136         set_fs(old_fs);
 137
 138         return 0;
 139 }
 140 #endif
 141
 142 /*
 143  * The details about the calling site of mcount on MIPS
 144  *
 145  * 1. For kernel:
 146  *
 147  * move at, ra
 148  * jal _mcount          --> nop
 149  *  sub sp, sp, 8       --> nop  (CONFIG_32BIT)
 150  *
 151  * 2. For modules:
 152  *
 153  * 2.1 For KBUILD_MCOUNT_RA_ADDRESS and CONFIG_32BIT
 154  *
 155  * lui v1, hi_16bit_of_mcount        --> b 1f (0x10000005)
 156  * addiu v1, v1, low_16bit_of_mcount --> nop  (CONFIG_32BIT)
 157  * move at, ra
 158  * move $12, ra_address
 159  * jalr v1
 160  *  sub sp, sp, 8
 161  *                                  1: offset = 5 instructions
 162  * 2.2 For the Other situations
 163  *
 164  * lui v1, hi_16bit_of_mcount        --> b 1f (0x10000004)
 165  * addiu v1, v1, low_16bit_of_mcount --> nop  (CONFIG_32BIT)
 166  * move at, ra
 167  * jalr v1
 168  *  nop | move $12, ra_address | sub sp, sp, 8
 169  *                                  1: offset = 4 instructions
 170  */
 171
 172 #define INSN_B_1F (0x10000000 | MCOUNT_OFFSET_INSNS)
 173
 174 int ftrace_make_nop(struct module *mod,
 175                     struct dyn_ftrace *rec, unsigned long addr)
 176 {
 177         unsigned int new;
 178         unsigned long ip = rec->ip;
 179
 180         /*
 181          * If ip is in kernel space, no long call, otherwise, long call is
 182          * needed.
 183          */
 184         new = core_kernel_text(ip) ? INSN_NOP : INSN_B_1F;
 185 #ifdef CONFIG_64BIT
 186         return ftrace_modify_code(ip, new);
 187 #else
 188         /*
 189          * On 32 bit MIPS platforms, gcc adds a stack adjust
 190          * instruction in the delay slot after the branch to
 191          * mcount and expects mcount to restore the sp on return.
 192          * This is based on a legacy API and does nothing but
 193          * waste instructions so it's being removed at runtime.
 194          */
 195         return ftrace_modify_code_2(ip, new, INSN_NOP);
 196 #endif
 197 }
 198
 199 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 200 {
 201         unsigned int new;
 202         unsigned long ip = rec->ip;
 203
 204         new = core_kernel_text(ip) ? insn_jal_ftrace_caller : insn_la_mcount[0];
 205
 206 #ifdef CONFIG_64BIT
 207         return ftrace_modify_code(ip, new);
 208 #else
 209         return ftrace_modify_code_2r(ip, new, core_kernel_text(ip) ?
 210                                                 INSN_NOP : insn_la_mcount[1]);
 211 #endif
 212 }
 213
 214 #define FTRACE_CALL_IP ((unsigned long)(&ftrace_call))
 215
 216 int ftrace_update_ftrace_func(ftrace_func_t func)
 217 {
 218         unsigned int new;
 219
 220         new = INSN_JAL((unsigned long)func);
 221
 222         return ftrace_modify_code(FTRACE_CALL_IP, new);
 223 }
 224
 225 int __init ftrace_dyn_arch_init(void)
 226 {
 227         /* Encode the instructions when booting */
 228         ftrace_dyn_arch_init_insns();
 229
 230         /* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */
 231         ftrace_modify_code(MCOUNT_ADDR, INSN_NOP);
 232
 233         return 0;
 234 }
 235 #endif  /* CONFIG_DYNAMIC_FTRACE */
 236
 237 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 238
 239 #ifdef CONFIG_DYNAMIC_FTRACE
 240
 241 extern void ftrace_graph_call(void);
 242 #define FTRACE_GRAPH_CALL_IP    ((unsigned long)(&ftrace_graph_call))
 243
 244 int ftrace_enable_ftrace_graph_caller(void)
 245 {
 246         return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
 247                         insn_j_ftrace_graph_caller);
 248 }
 249
 250 int ftrace_disable_ftrace_graph_caller(void)
 251 {
 252         return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP);
 253 }
 254
 255 #endif  /* CONFIG_DYNAMIC_FTRACE */
 256
 257 #ifndef KBUILD_MCOUNT_RA_ADDRESS
 258
 259 #define S_RA_SP (0xafbf << 16)  /* s{d,w} ra, offset(sp) */
 260 #define S_R_SP  (0xafb0 << 16)  /* s{d,w} R, offset(sp) */
 261 #define OFFSET_MASK     0xffff  /* stack offset range: 0 ~ PT_SIZE */
 262
 263 unsigned long ftrace_get_parent_ra_addr(unsigned long self_ra, unsigned long
 264                 old_parent_ra, unsigned long parent_ra_addr, unsigned long fp)
 265 {
 266         unsigned long sp, ip, tmp;
 267         unsigned int code;
 268         int faulted;
 269
 270         /*
 271          * For module, move the ip from the return address after the
 272          * instruction "lui v1, hi_16bit_of_mcount"(offset is 24), but for
 273          * kernel, move after the instruction "move ra, at"(offset is 16)
 274          */
 275         ip = self_ra - (core_kernel_text(self_ra) ? 16 : 24);
 276
 277         /*
 278          * search the text until finding the non-store instruction or "s{d,w}
 279          * ra, offset(sp)" instruction
 280          */
 281         do {
 282                 /* get the code at "ip": code = *(unsigned int *)ip; */
 283                 safe_load_code(code, ip, faulted);
 284
 285                 if (unlikely(faulted))
 286                         return 0;
 287                 /*
 288                  * If we hit the non-store instruction before finding where the
 289                  * ra is stored, then this is a leaf function and it does not
 290                  * store the ra on the stack
 291                  */
 292                 if ((code & S_R_SP) != S_R_SP)
 293                         return parent_ra_addr;
 294
 295                 /* Move to the next instruction */
 296                 ip -= 4;
 297         } while ((code & S_RA_SP) != S_RA_SP);
 298
 299         sp = fp + (code & OFFSET_MASK);
 300
 301         /* tmp = *(unsigned long *)sp; */
 302         safe_load_stack(tmp, sp, faulted);
 303         if (unlikely(faulted))
 304                 return 0;
 305
 306         if (tmp == old_parent_ra)
 307                 return sp;
 308         return 0;
 309 }
 310
 311 #endif  /* !KBUILD_MCOUNT_RA_ADDRESS */
 312
 313 /*
 314  * Hook the return address and push it in the stack of return addrs
 315  * in current thread info.
 316  */
 317 void prepare_ftrace_return(unsigned long *parent_ra_addr, unsigned long self_ra,
 318                            unsigned long fp)
 319 {
 320         unsigned long old_parent_ra;
 321         unsigned long return_hooker = (unsigned long)
 322             &return_to_handler;
 323         int faulted, insns;
 324
 325         if (unlikely(ftrace_graph_is_dead()))
 326                 return;
 327
 328         if (unlikely(atomic_read(&current->tracing_graph_pause)))
 329                 return;
 330
 331         /*
 332          * "parent_ra_addr" is the stack address where the return address of
 333          * the caller of _mcount is saved.
 334          *
 335          * If gcc < 4.5, a leaf function does not save the return address
 336          * in the stack address, so we "emulate" one in _mcount's stack space,
 337          * and hijack it directly.
 338          * For a non-leaf function, it does save the return address to its own
 339          * stack space, so we can not hijack it directly, but need to find the
 340          * real stack address, which is done by ftrace_get_parent_addr().
 341          *
 342          * If gcc >= 4.5, with the new -mmcount-ra-address option, for a
 343          * non-leaf function, the location of the return address will be saved
 344          * to $12 for us.
 345          * For a leaf function, it just puts a zero into $12, so we handle
 346          * it in ftrace_graph_caller() of mcount.S.
 347          */
 348
 349         /* old_parent_ra = *parent_ra_addr; */
 350         safe_load_stack(old_parent_ra, parent_ra_addr, faulted);
 351         if (unlikely(faulted))
 352                 goto out;
 353 #ifndef KBUILD_MCOUNT_RA_ADDRESS
 354         parent_ra_addr = (unsigned long *)ftrace_get_parent_ra_addr(self_ra,
 355                         old_parent_ra, (unsigned long)parent_ra_addr, fp);
 356         /*
 357          * If fails when getting the stack address of the non-leaf function's
 358          * ra, stop function graph tracer and return
 359          */
 360         if (parent_ra_addr == NULL)
 361                 goto out;
 362 #endif
 363         /* *parent_ra_addr = return_hooker; */
 364         safe_store_stack(return_hooker, parent_ra_addr, faulted);
 365         if (unlikely(faulted))
 366                 goto out;
 367
 368         /*
 369          * Get the recorded ip of the current mcount calling site in the
 370          * __mcount_loc section, which will be used to filter the function
 371          * entries configured through the tracing/set_graph_function interface.
 372          */
 373
 374         insns = core_kernel_text(self_ra) ? 2 : MCOUNT_OFFSET_INSNS + 1;
 375         self_ra -= (MCOUNT_INSN_SIZE * insns);
 376
 377         if (function_graph_enter(old_parent_ra, self_ra, fp, NULL))
 378                 *parent_ra_addr = old_parent_ra;
 379         return;
 380 out:
 381         ftrace_graph_stop();
 382         WARN_ON(1);
 383 }
 384 #endif  /* CONFIG_FUNCTION_GRAPH_TRACER */
 385
 386 #ifdef CONFIG_FTRACE_SYSCALLS
 387
 388 #ifdef CONFIG_32BIT
 389 unsigned long __init arch_syscall_addr(int nr)
 390 {
 391         return (unsigned long)sys_call_table[nr - __NR_O32_Linux];
 392 }
 393 #endif
 394
 395 #ifdef CONFIG_64BIT
 396
 397 unsigned long __init arch_syscall_addr(int nr)
 398 {
 399 #ifdef CONFIG_MIPS32_N32
 400         if (nr >= __NR_N32_Linux && nr < __NR_N32_Linux + __NR_N32_Linux_syscalls)
 401                 return (unsigned long)sysn32_call_table[nr - __NR_N32_Linux];
 402 #endif
 403         if (nr >= __NR_64_Linux  && nr < __NR_64_Linux + __NR_64_Linux_syscalls)
 404                 return (unsigned long)sys_call_table[nr - __NR_64_Linux];
 405 #ifdef CONFIG_MIPS32_O32
 406         if (nr >= __NR_O32_Linux && nr < __NR_O32_Linux + __NR_O32_Linux_syscalls)
 407                 return (unsigned long)sys32_call_table[nr - __NR_O32_Linux];
 408 #endif
 409
 410         return (unsigned long) &sys_ni_syscall;
 411 }
 412 #endif
 413
 414 #endif /* CONFIG_FTRACE_SYSCALLS */