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
  77         /* *(unsigned int *)ip = new_code; */
  78         safe_store_code(new_code, ip, faulted);
  79
  80         if (unlikely(faulted))
  81                 return -EFAULT;
  82
  83         flush_icache_range(ip, ip + 8);
  84
  85         return 0;
  86 }
  87
  88 #ifndef CONFIG_64BIT
  89 static int ftrace_modify_code_2(unsigned long ip, unsigned int new_code1,
  90                                 unsigned int new_code2)
  91 {
  92         int faulted;
  93
  94         safe_store_code(new_code1, ip, faulted);
  95         if (unlikely(faulted))
  96                 return -EFAULT;
  97
  98         ip += 4;
  99         safe_store_code(new_code2, ip, faulted);
 100         if (unlikely(faulted))
 101                 return -EFAULT;
 102
 103         ip -= 4;
 104         flush_icache_range(ip, ip + 8);
 105
 106         return 0;
 107 }
 108
 109 static int ftrace_modify_code_2r(unsigned long ip, unsigned int new_code1,
 110                                  unsigned int new_code2)
 111 {
 112         int faulted;
 113
 114         ip += 4;
 115         safe_store_code(new_code2, ip, faulted);
 116         if (unlikely(faulted))
 117                 return -EFAULT;
 118
 119         ip -= 4;
 120         safe_store_code(new_code1, ip, faulted);
 121         if (unlikely(faulted))
 122                 return -EFAULT;
 123
 124         flush_icache_range(ip, ip + 8);
 125
 126         return 0;
 127 }
 128 #endif
 129
 130 /*
 131  * The details about the calling site of mcount on MIPS
 132  *
 133  * 1. For kernel:
 134  *
 135  * move at, ra
 136  * jal _mcount          --> nop
 137  *  sub sp, sp, 8       --> nop  (CONFIG_32BIT)
 138  *
 139  * 2. For modules:
 140  *
 141  * 2.1 For KBUILD_MCOUNT_RA_ADDRESS and CONFIG_32BIT
 142  *
 143  * lui v1, hi_16bit_of_mcount        --> b 1f (0x10000005)
 144  * addiu v1, v1, low_16bit_of_mcount --> nop  (CONFIG_32BIT)
 145  * move at, ra
 146  * move $12, ra_address
 147  * jalr v1
 148  *  sub sp, sp, 8
 149  *                                  1: offset = 5 instructions
 150  * 2.2 For the Other situations
 151  *
 152  * lui v1, hi_16bit_of_mcount        --> b 1f (0x10000004)
 153  * addiu v1, v1, low_16bit_of_mcount --> nop  (CONFIG_32BIT)
 154  * move at, ra
 155  * jalr v1
 156  *  nop | move $12, ra_address | sub sp, sp, 8
 157  *                                  1: offset = 4 instructions
 158  */
 159
 160 #define INSN_B_1F (0x10000000 | MCOUNT_OFFSET_INSNS)
 161
 162 int ftrace_make_nop(struct module *mod,
 163                     struct dyn_ftrace *rec, unsigned long addr)
 164 {
 165         unsigned int new;
 166         unsigned long ip = rec->ip;
 167
 168         /*
 169          * If ip is in kernel space, no long call, otherwise, long call is
 170          * needed.
 171          */
 172         new = core_kernel_text(ip) ? INSN_NOP : INSN_B_1F;
 173 #ifdef CONFIG_64BIT
 174         return ftrace_modify_code(ip, new);
 175 #else
 176         /*
 177          * On 32 bit MIPS platforms, gcc adds a stack adjust
 178          * instruction in the delay slot after the branch to
 179          * mcount and expects mcount to restore the sp on return.
 180          * This is based on a legacy API and does nothing but
 181          * waste instructions so it's being removed at runtime.
 182          */
 183         return ftrace_modify_code_2(ip, new, INSN_NOP);
 184 #endif
 185 }
 186
 187 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 188 {
 189         unsigned int new;
 190         unsigned long ip = rec->ip;
 191
 192         new = core_kernel_text(ip) ? insn_jal_ftrace_caller : insn_la_mcount[0];
 193
 194 #ifdef CONFIG_64BIT
 195         return ftrace_modify_code(ip, new);
 196 #else
 197         return ftrace_modify_code_2r(ip, new, core_kernel_text(ip) ?
 198                                                 INSN_NOP : insn_la_mcount[1]);
 199 #endif
 200 }
 201
 202 #define FTRACE_CALL_IP ((unsigned long)(&ftrace_call))
 203
 204 int ftrace_update_ftrace_func(ftrace_func_t func)
 205 {
 206         unsigned int new;
 207
 208         new = INSN_JAL((unsigned long)func);
 209
 210         return ftrace_modify_code(FTRACE_CALL_IP, new);
 211 }
 212
 213 int __init ftrace_dyn_arch_init(void)
 214 {
 215         /* Encode the instructions when booting */
 216         ftrace_dyn_arch_init_insns();
 217
 218         /* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */
 219         ftrace_modify_code(MCOUNT_ADDR, INSN_NOP);
 220
 221         return 0;
 222 }
 223 #endif  /* CONFIG_DYNAMIC_FTRACE */
 224
 225 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 226
 227 #ifdef CONFIG_DYNAMIC_FTRACE
 228
 229 extern void ftrace_graph_call(void);
 230 #define FTRACE_GRAPH_CALL_IP    ((unsigned long)(&ftrace_graph_call))
 231
 232 int ftrace_enable_ftrace_graph_caller(void)
 233 {
 234         return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
 235                         insn_j_ftrace_graph_caller);
 236 }
 237
 238 int ftrace_disable_ftrace_graph_caller(void)
 239 {
 240         return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP);
 241 }
 242
 243 #endif  /* CONFIG_DYNAMIC_FTRACE */
 244
 245 #ifndef KBUILD_MCOUNT_RA_ADDRESS
 246
 247 #define S_RA_SP (0xafbf << 16)  /* s{d,w} ra, offset(sp) */
 248 #define S_R_SP  (0xafb0 << 16)  /* s{d,w} R, offset(sp) */
 249 #define OFFSET_MASK     0xffff  /* stack offset range: 0 ~ PT_SIZE */
 250
 251 unsigned long ftrace_get_parent_ra_addr(unsigned long self_ra, unsigned long
 252                 old_parent_ra, unsigned long parent_ra_addr, unsigned long fp)
 253 {
 254         unsigned long sp, ip, tmp;
 255         unsigned int code;
 256         int faulted;
 257
 258         /*
 259          * For module, move the ip from the return address after the
 260          * instruction "lui v1, hi_16bit_of_mcount"(offset is 24), but for
 261          * kernel, move after the instruction "move ra, at"(offset is 16)
 262          */
 263         ip = self_ra - (core_kernel_text(self_ra) ? 16 : 24);
 264
 265         /*
 266          * search the text until finding the non-store instruction or "s{d,w}
 267          * ra, offset(sp)" instruction
 268          */
 269         do {
 270                 /* get the code at "ip": code = *(unsigned int *)ip; */
 271                 safe_load_code(code, ip, faulted);
 272
 273                 if (unlikely(faulted))
 274                         return 0;
 275                 /*
 276                  * If we hit the non-store instruction before finding where the
 277                  * ra is stored, then this is a leaf function and it does not
 278                  * store the ra on the stack
 279                  */
 280                 if ((code & S_R_SP) != S_R_SP)
 281                         return parent_ra_addr;
 282
 283                 /* Move to the next instruction */
 284                 ip -= 4;
 285         } while ((code & S_RA_SP) != S_RA_SP);
 286
 287         sp = fp + (code & OFFSET_MASK);
 288
 289         /* tmp = *(unsigned long *)sp; */
 290         safe_load_stack(tmp, sp, faulted);
 291         if (unlikely(faulted))
 292                 return 0;
 293
 294         if (tmp == old_parent_ra)
 295                 return sp;
 296         return 0;
 297 }
 298
 299 #endif  /* !KBUILD_MCOUNT_RA_ADDRESS */
 300
 301 /*
 302  * Hook the return address and push it in the stack of return addrs
 303  * in current thread info.
 304  */
 305 void prepare_ftrace_return(unsigned long *parent_ra_addr, unsigned long self_ra,
 306                            unsigned long fp)
 307 {
 308         unsigned long old_parent_ra;
 309         unsigned long return_hooker = (unsigned long)
 310             &return_to_handler;
 311         int faulted, insns;
 312
 313         if (unlikely(ftrace_graph_is_dead()))
 314                 return;
 315
 316         if (unlikely(atomic_read(&current->tracing_graph_pause)))
 317                 return;
 318
 319         /*
 320          * "parent_ra_addr" is the stack address where the return address of
 321          * the caller of _mcount is saved.
 322          *
 323          * If gcc < 4.5, a leaf function does not save the return address
 324          * in the stack address, so we "emulate" one in _mcount's stack space,
 325          * and hijack it directly.
 326          * For a non-leaf function, it does save the return address to its own
 327          * stack space, so we can not hijack it directly, but need to find the
 328          * real stack address, which is done by ftrace_get_parent_addr().
 329          *
 330          * If gcc >= 4.5, with the new -mmcount-ra-address option, for a
 331          * non-leaf function, the location of the return address will be saved
 332          * to $12 for us.
 333          * For a leaf function, it just puts a zero into $12, so we handle
 334          * it in ftrace_graph_caller() of mcount.S.
 335          */
 336
 337         /* old_parent_ra = *parent_ra_addr; */
 338         safe_load_stack(old_parent_ra, parent_ra_addr, faulted);
 339         if (unlikely(faulted))
 340                 goto out;
 341 #ifndef KBUILD_MCOUNT_RA_ADDRESS
 342         parent_ra_addr = (unsigned long *)ftrace_get_parent_ra_addr(self_ra,
 343                         old_parent_ra, (unsigned long)parent_ra_addr, fp);
 344         /*
 345          * If fails when getting the stack address of the non-leaf function's
 346          * ra, stop function graph tracer and return
 347          */
 348         if (parent_ra_addr == NULL)
 349                 goto out;
 350 #endif
 351         /* *parent_ra_addr = return_hooker; */
 352         safe_store_stack(return_hooker, parent_ra_addr, faulted);
 353         if (unlikely(faulted))
 354                 goto out;
 355
 356         /*
 357          * Get the recorded ip of the current mcount calling site in the
 358          * __mcount_loc section, which will be used to filter the function
 359          * entries configured through the tracing/set_graph_function interface.
 360          */
 361
 362         insns = core_kernel_text(self_ra) ? 2 : MCOUNT_OFFSET_INSNS + 1;
 363         self_ra -= (MCOUNT_INSN_SIZE * insns);
 364
 365         if (function_graph_enter(old_parent_ra, self_ra, fp, NULL))
 366                 *parent_ra_addr = old_parent_ra;
 367         return;
 368 out:
 369         ftrace_graph_stop();
 370         WARN_ON(1);
 371 }
 372 #endif  /* CONFIG_FUNCTION_GRAPH_TRACER */
 373
 374 #ifdef CONFIG_FTRACE_SYSCALLS
 375
 376 #ifdef CONFIG_32BIT
 377 unsigned long __init arch_syscall_addr(int nr)
 378 {
 379         return (unsigned long)sys_call_table[nr - __NR_O32_Linux];
 380 }
 381 #endif
 382
 383 #ifdef CONFIG_64BIT
 384
 385 unsigned long __init arch_syscall_addr(int nr)
 386 {
 387 #ifdef CONFIG_MIPS32_N32
 388         if (nr >= __NR_N32_Linux && nr < __NR_N32_Linux + __NR_N32_Linux_syscalls)
 389                 return (unsigned long)sysn32_call_table[nr - __NR_N32_Linux];
 390 #endif
 391         if (nr >= __NR_64_Linux  && nr < __NR_64_Linux + __NR_64_Linux_syscalls)
 392                 return (unsigned long)sys_call_table[nr - __NR_64_Linux];
 393 #ifdef CONFIG_MIPS32_O32
 394         if (nr >= __NR_O32_Linux && nr < __NR_O32_Linux + __NR_O32_Linux_syscalls)
 395                 return (unsigned long)sys32_call_table[nr - __NR_O32_Linux];
 396 #endif
 397
 398         return (unsigned long) &sys_ni_syscall;
 399 }
 400 #endif
 401
 402 #endif /* CONFIG_FTRACE_SYSCALLS */