root/arch/mips/kernel/ftrace.c

DEFINITIONS

1. arch_ftrace_update_code
2. ftrace_dyn_arch_init_insns
3. ftrace_modify_code
4. ftrace_modify_code_2
5. ftrace_modify_code_2r
6. ftrace_make_nop
7. ftrace_make_call
8. ftrace_update_ftrace_func
9. ftrace_dyn_arch_init
10. ftrace_enable_ftrace_graph_caller
11. ftrace_disable_ftrace_graph_caller
12. ftrace_get_parent_ra_addr
13. prepare_ftrace_return
14. arch_syscall_addr
15. arch_syscall_addr

   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 #endif
  41 
  42 #ifdef CONFIG_DYNAMIC_FTRACE
  43 
  44 #define JAL 0x0c000000          /* jump & link: ip --> ra, jump to target */
  45 #define ADDR_MASK 0x03ffffff    /*  op_code|addr : 31...26|25 ....0 */
  46 #define JUMP_RANGE_MASK ((1UL << 28) - 1)
  47 
  48 #define INSN_NOP 0x00000000     /* nop */
  49 #define INSN_JAL(addr)  \
  50         ((unsigned int)(JAL | (((addr) >> 2) & ADDR_MASK)))
  51 
  52 static unsigned int insn_jal_ftrace_caller __read_mostly;
  53 static unsigned int insn_la_mcount[2] __read_mostly;
  54 static unsigned int insn_j_ftrace_graph_caller __maybe_unused __read_mostly;
  55 
  56 static inline void ftrace_dyn_arch_init_insns(void)
  57 {
  58         u32 *buf;
  59         unsigned int v1;
  60 
  61         /* la v1, _mcount */
  62         v1 = 3;
  63         buf = (u32 *)&insn_la_mcount[0];
  64         UASM_i_LA(&buf, v1, MCOUNT_ADDR);
  65 
  66         /* jal (ftrace_caller + 8), jump over the first two instruction */
  67         buf = (u32 *)&insn_jal_ftrace_caller;
  68         uasm_i_jal(&buf, (FTRACE_ADDR + 8) & JUMP_RANGE_MASK);
  69 
  70 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
  71         /* j ftrace_graph_caller */
  72         buf = (u32 *)&insn_j_ftrace_graph_caller;
  73         uasm_i_j(&buf, (unsigned long)ftrace_graph_caller & JUMP_RANGE_MASK);
  74 #endif
  75 }
  76 
  77 static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
  78 {
  79         int faulted;
  80         mm_segment_t old_fs;
  81 
  82         /* *(unsigned int *)ip = new_code; */
  83         safe_store_code(new_code, ip, faulted);
  84 
  85         if (unlikely(faulted))
  86                 return -EFAULT;
  87 
  88         old_fs = get_fs();
  89         set_fs(KERNEL_DS);
  90         flush_icache_range(ip, ip + 8);
  91         set_fs(old_fs);
  92 
  93         return 0;
  94 }
  95 
  96 #ifndef CONFIG_64BIT
  97 static int ftrace_modify_code_2(unsigned long ip, unsigned int new_code1,
  98                                 unsigned int new_code2)
  99 {
 100         int faulted;
 101         mm_segment_t old_fs;
 102 
 103         safe_store_code(new_code1, ip, faulted);
 104         if (unlikely(faulted))
 105                 return -EFAULT;
 106 
 107         ip += 4;
 108         safe_store_code(new_code2, ip, faulted);
 109         if (unlikely(faulted))
 110                 return -EFAULT;
 111 
 112         ip -= 4;
 113         old_fs = get_fs();
 114         set_fs(KERNEL_DS);
 115         flush_icache_range(ip, ip + 8);
 116         set_fs(old_fs);
 117 
 118         return 0;
 119 }
 120 
 121 static int ftrace_modify_code_2r(unsigned long ip, unsigned int new_code1,
 122                                  unsigned int new_code2)
 123 {
 124         int faulted;
 125         mm_segment_t old_fs;
 126 
 127         ip += 4;
 128         safe_store_code(new_code2, ip, faulted);
 129         if (unlikely(faulted))
 130                 return -EFAULT;
 131 
 132         ip -= 4;
 133         safe_store_code(new_code1, ip, faulted);
 134         if (unlikely(faulted))
 135                 return -EFAULT;
 136 
 137         old_fs = get_fs();
 138         set_fs(KERNEL_DS);
 139         flush_icache_range(ip, ip + 8);
 140         set_fs(old_fs);
 141 
 142         return 0;
 143 }
 144 #endif
 145 
 146 /*
 147  * The details about the calling site of mcount on MIPS
 148  *
 149  * 1. For kernel:
 150  *
 151  * move at, ra
 152  * jal _mcount          --> nop
 153  *  sub sp, sp, 8       --> nop  (CONFIG_32BIT)
 154  *
 155  * 2. For modules:
 156  *
 157  * 2.1 For KBUILD_MCOUNT_RA_ADDRESS and CONFIG_32BIT
 158  *
 159  * lui v1, hi_16bit_of_mcount        --> b 1f (0x10000005)
 160  * addiu v1, v1, low_16bit_of_mcount --> nop  (CONFIG_32BIT)
 161  * move at, ra
 162  * move $12, ra_address
 163  * jalr v1
 164  *  sub sp, sp, 8
 165  *                                  1: offset = 5 instructions
 166  * 2.2 For the Other situations
 167  *
 168  * lui v1, hi_16bit_of_mcount        --> b 1f (0x10000004)
 169  * addiu v1, v1, low_16bit_of_mcount --> nop  (CONFIG_32BIT)
 170  * move at, ra
 171  * jalr v1
 172  *  nop | move $12, ra_address | sub sp, sp, 8
 173  *                                  1: offset = 4 instructions
 174  */
 175 
 176 #define INSN_B_1F (0x10000000 | MCOUNT_OFFSET_INSNS)
 177 
 178 int ftrace_make_nop(struct module *mod,
 179                     struct dyn_ftrace *rec, unsigned long addr)
 180 {
 181         unsigned int new;
 182         unsigned long ip = rec->ip;
 183 
 184         /*
 185          * If ip is in kernel space, no long call, otherwise, long call is
 186          * needed.
 187          */
 188         new = core_kernel_text(ip) ? INSN_NOP : INSN_B_1F;
 189 #ifdef CONFIG_64BIT
 190         return ftrace_modify_code(ip, new);
 191 #else
 192         /*
 193          * On 32 bit MIPS platforms, gcc adds a stack adjust
 194          * instruction in the delay slot after the branch to
 195          * mcount and expects mcount to restore the sp on return.
 196          * This is based on a legacy API and does nothing but
 197          * waste instructions so it's being removed at runtime.
 198          */
 199         return ftrace_modify_code_2(ip, new, INSN_NOP);
 200 #endif
 201 }
 202 
 203 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 204 {
 205         unsigned int new;
 206         unsigned long ip = rec->ip;
 207 
 208         new = core_kernel_text(ip) ? insn_jal_ftrace_caller : insn_la_mcount[0];
 209 
 210 #ifdef CONFIG_64BIT
 211         return ftrace_modify_code(ip, new);
 212 #else
 213         return ftrace_modify_code_2r(ip, new, core_kernel_text(ip) ?
 214                                                 INSN_NOP : insn_la_mcount[1]);
 215 #endif
 216 }
 217 
 218 #define FTRACE_CALL_IP ((unsigned long)(&ftrace_call))
 219 
 220 int ftrace_update_ftrace_func(ftrace_func_t func)
 221 {
 222         unsigned int new;
 223 
 224         new = INSN_JAL((unsigned long)func);
 225 
 226         return ftrace_modify_code(FTRACE_CALL_IP, new);
 227 }
 228 
 229 int __init ftrace_dyn_arch_init(void)
 230 {
 231         /* Encode the instructions when booting */
 232         ftrace_dyn_arch_init_insns();
 233 
 234         /* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */
 235         ftrace_modify_code(MCOUNT_ADDR, INSN_NOP);
 236 
 237         return 0;
 238 }
 239 #endif  /* CONFIG_DYNAMIC_FTRACE */
 240 
 241 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 242 
 243 #ifdef CONFIG_DYNAMIC_FTRACE
 244 
 245 extern void ftrace_graph_call(void);
 246 #define FTRACE_GRAPH_CALL_IP    ((unsigned long)(&ftrace_graph_call))
 247 
 248 int ftrace_enable_ftrace_graph_caller(void)
 249 {
 250         return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
 251                         insn_j_ftrace_graph_caller);
 252 }
 253 
 254 int ftrace_disable_ftrace_graph_caller(void)
 255 {
 256         return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP);
 257 }
 258 
 259 #endif  /* CONFIG_DYNAMIC_FTRACE */
 260 
 261 #ifndef KBUILD_MCOUNT_RA_ADDRESS
 262 
 263 #define S_RA_SP (0xafbf << 16)  /* s{d,w} ra, offset(sp) */
 264 #define S_R_SP  (0xafb0 << 16)  /* s{d,w} R, offset(sp) */
 265 #define OFFSET_MASK     0xffff  /* stack offset range: 0 ~ PT_SIZE */
 266 
 267 unsigned long ftrace_get_parent_ra_addr(unsigned long self_ra, unsigned long
 268                 old_parent_ra, unsigned long parent_ra_addr, unsigned long fp)
 269 {
 270         unsigned long sp, ip, tmp;
 271         unsigned int code;
 272         int faulted;
 273 
 274         /*
 275          * For module, move the ip from the return address after the
 276          * instruction "lui v1, hi_16bit_of_mcount"(offset is 24), but for
 277          * kernel, move after the instruction "move ra, at"(offset is 16)
 278          */
 279         ip = self_ra - (core_kernel_text(self_ra) ? 16 : 24);
 280 
 281         /*
 282          * search the text until finding the non-store instruction or "s{d,w}
 283          * ra, offset(sp)" instruction
 284          */
 285         do {
 286                 /* get the code at "ip": code = *(unsigned int *)ip; */
 287                 safe_load_code(code, ip, faulted);
 288 
 289                 if (unlikely(faulted))
 290                         return 0;
 291                 /*
 292                  * If we hit the non-store instruction before finding where the
 293                  * ra is stored, then this is a leaf function and it does not
 294                  * store the ra on the stack
 295                  */
 296                 if ((code & S_R_SP) != S_R_SP)
 297                         return parent_ra_addr;
 298 
 299                 /* Move to the next instruction */
 300                 ip -= 4;
 301         } while ((code & S_RA_SP) != S_RA_SP);
 302 
 303         sp = fp + (code & OFFSET_MASK);
 304 
 305         /* tmp = *(unsigned long *)sp; */
 306         safe_load_stack(tmp, sp, faulted);
 307         if (unlikely(faulted))
 308                 return 0;
 309 
 310         if (tmp == old_parent_ra)
 311                 return sp;
 312         return 0;
 313 }
 314 
 315 #endif  /* !KBUILD_MCOUNT_RA_ADDRESS */
 316 
 317 /*
 318  * Hook the return address and push it in the stack of return addrs
 319  * in current thread info.
 320  */
 321 void prepare_ftrace_return(unsigned long *parent_ra_addr, unsigned long self_ra,
 322                            unsigned long fp)
 323 {
 324         unsigned long old_parent_ra;
 325         unsigned long return_hooker = (unsigned long)
 326             &return_to_handler;
 327         int faulted, insns;
 328 
 329         if (unlikely(ftrace_graph_is_dead()))
 330                 return;
 331 
 332         if (unlikely(atomic_read(&current->tracing_graph_pause)))
 333                 return;
 334 
 335         /*
 336          * "parent_ra_addr" is the stack address where the return address of
 337          * the caller of _mcount is saved.
 338          *
 339          * If gcc < 4.5, a leaf function does not save the return address
 340          * in the stack address, so we "emulate" one in _mcount's stack space,
 341          * and hijack it directly.
 342          * For a non-leaf function, it does save the return address to its own
 343          * stack space, so we can not hijack it directly, but need to find the
 344          * real stack address, which is done by ftrace_get_parent_addr().
 345          *
 346          * If gcc >= 4.5, with the new -mmcount-ra-address option, for a
 347          * non-leaf function, the location of the return address will be saved
 348          * to $12 for us.
 349          * For a leaf function, it just puts a zero into $12, so we handle
 350          * it in ftrace_graph_caller() of mcount.S.
 351          */
 352 
 353         /* old_parent_ra = *parent_ra_addr; */
 354         safe_load_stack(old_parent_ra, parent_ra_addr, faulted);
 355         if (unlikely(faulted))
 356                 goto out;
 357 #ifndef KBUILD_MCOUNT_RA_ADDRESS
 358         parent_ra_addr = (unsigned long *)ftrace_get_parent_ra_addr(self_ra,
 359                         old_parent_ra, (unsigned long)parent_ra_addr, fp);
 360         /*
 361          * If fails when getting the stack address of the non-leaf function's
 362          * ra, stop function graph tracer and return
 363          */
 364         if (parent_ra_addr == NULL)
 365                 goto out;
 366 #endif
 367         /* *parent_ra_addr = return_hooker; */
 368         safe_store_stack(return_hooker, parent_ra_addr, faulted);
 369         if (unlikely(faulted))
 370                 goto out;
 371 
 372         /*
 373          * Get the recorded ip of the current mcount calling site in the
 374          * __mcount_loc section, which will be used to filter the function
 375          * entries configured through the tracing/set_graph_function interface.
 376          */
 377 
 378         insns = core_kernel_text(self_ra) ? 2 : MCOUNT_OFFSET_INSNS + 1;
 379         self_ra -= (MCOUNT_INSN_SIZE * insns);
 380 
 381         if (function_graph_enter(old_parent_ra, self_ra, fp, NULL))
 382                 *parent_ra_addr = old_parent_ra;
 383         return;
 384 out:
 385         ftrace_graph_stop();
 386         WARN_ON(1);
 387 }
 388 #endif  /* CONFIG_FUNCTION_GRAPH_TRACER */
 389 
 390 #ifdef CONFIG_FTRACE_SYSCALLS
 391 
 392 #ifdef CONFIG_32BIT
 393 unsigned long __init arch_syscall_addr(int nr)
 394 {
 395         return (unsigned long)sys_call_table[nr - __NR_O32_Linux];
 396 }
 397 #endif
 398 
 399 #ifdef CONFIG_64BIT
 400 
 401 unsigned long __init arch_syscall_addr(int nr)
 402 {
 403 #ifdef CONFIG_MIPS32_N32
 404         if (nr >= __NR_N32_Linux && nr < __NR_N32_Linux + __NR_N32_Linux_syscalls)
 405                 return (unsigned long)sysn32_call_table[nr - __NR_N32_Linux];
 406 #endif
 407         if (nr >= __NR_64_Linux  && nr < __NR_64_Linux + __NR_64_Linux_syscalls)
 408                 return (unsigned long)sys_call_table[nr - __NR_64_Linux];
 409 #ifdef CONFIG_MIPS32_O32
 410         if (nr >= __NR_O32_Linux && nr < __NR_O32_Linux + __NR_O32_Linux_syscalls)
 411                 return (unsigned long)sys32_call_table[nr - __NR_O32_Linux];
 412 #endif
 413 
 414         return (unsigned long) &sys_ni_syscall;
 415 }
 416 #endif
 417 
 418 #endif /* CONFIG_FTRACE_SYSCALLS */