arch/arm/kernel/ftrace.c

   1 /*
   2  * Dynamic function tracing support.
   3  *
   4  * Copyright (C) 2008 Abhishek Sagar <sagar.abhishek@gmail.com>
   5  * Copyright (C) 2010 Rabin Vincent <rabin@rab.in>
   6  *
   7  * For licencing details, see COPYING.
   8  *
   9  * Defines low-level handling of mcount calls when the kernel
  10  * is compiled with the -pg flag. When using dynamic ftrace, the
  11  * mcount call-sites get patched with NOP till they are enabled.
  12  * All code mutation routines here are called under stop_machine().
  13  */
  14
  15 #include <linux/ftrace.h>
  16 #include <linux/uaccess.h>
  17 #include <linux/module.h>
  18 #include <linux/stop_machine.h>
  19
  20 #include <asm/cacheflush.h>
  21 #include <asm/opcodes.h>
  22 #include <asm/ftrace.h>
  23 #include <asm/insn.h>
  24 #include <asm/set_memory.h>
  25
  26 #ifdef CONFIG_THUMB2_KERNEL
  27 #define NOP             0xf85deb04      /* pop.w {lr} */
  28 #else
  29 #define NOP             0xe8bd4000      /* pop {lr} */
  30 #endif
  31
  32 #ifdef CONFIG_DYNAMIC_FTRACE
  33
  34 static int __ftrace_modify_code(void *data)
  35 {
  36         int *command = data;
  37
  38         set_kernel_text_rw();
  39         ftrace_modify_all_code(*command);
  40         set_kernel_text_ro();
  41
  42         return 0;
  43 }
  44
  45 void arch_ftrace_update_code(int command)
  46 {
  47         stop_machine(__ftrace_modify_code, &command, NULL);
  48 }
  49
  50 #ifdef CONFIG_OLD_MCOUNT
  51 #define OLD_MCOUNT_ADDR ((unsigned long) mcount)
  52 #define OLD_FTRACE_ADDR ((unsigned long) ftrace_caller_old)
  53
  54 #define OLD_NOP         0xe1a00000      /* mov r0, r0 */
  55
  56 static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
  57 {
  58         return rec->arch.old_mcount ? OLD_NOP : NOP;
  59 }
  60
  61 static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
  62 {
  63         if (!rec->arch.old_mcount)
  64                 return addr;
  65
  66         if (addr == MCOUNT_ADDR)
  67                 addr = OLD_MCOUNT_ADDR;
  68         else if (addr == FTRACE_ADDR)
  69                 addr = OLD_FTRACE_ADDR;
  70
  71         return addr;
  72 }
  73 #else
  74 static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
  75 {
  76         return NOP;
  77 }
  78
  79 static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
  80 {
  81         return addr;
  82 }
  83 #endif
  84
  85 int ftrace_arch_code_modify_prepare(void)
  86 {
  87         set_all_modules_text_rw();
  88         return 0;
  89 }
  90
  91 int ftrace_arch_code_modify_post_process(void)
  92 {
  93         set_all_modules_text_ro();
  94         /* Make sure any TLB misses during machine stop are cleared. */
  95         flush_tlb_all();
  96         return 0;
  97 }
  98
  99 static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr,
 100                                          bool warn)
 101 {
 102         return arm_gen_branch_link(pc, addr, warn);
 103 }
 104
 105 static int ftrace_modify_code(unsigned long pc, unsigned long old,
 106                               unsigned long new, bool validate)
 107 {
 108         unsigned long replaced;
 109
 110         if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) {
 111                 old = __opcode_to_mem_thumb32(old);
 112                 new = __opcode_to_mem_thumb32(new);
 113         } else {
 114                 old = __opcode_to_mem_arm(old);
 115                 new = __opcode_to_mem_arm(new);
 116         }
 117
 118         if (validate) {
 119                 if (probe_kernel_read(&replaced, (void *)pc, MCOUNT_INSN_SIZE))
 120                         return -EFAULT;
 121
 122                 if (replaced != old)
 123                         return -EINVAL;
 124         }
 125
 126         if (probe_kernel_write((void *)pc, &new, MCOUNT_INSN_SIZE))
 127                 return -EPERM;
 128
 129         flush_icache_range(pc, pc + MCOUNT_INSN_SIZE);
 130
 131         return 0;
 132 }
 133
 134 int ftrace_update_ftrace_func(ftrace_func_t func)
 135 {
 136         unsigned long pc;
 137         unsigned long new;
 138         int ret;
 139
 140         pc = (unsigned long)&ftrace_call;
 141         new = ftrace_call_replace(pc, (unsigned long)func, true);
 142
 143         ret = ftrace_modify_code(pc, 0, new, false);
 144
 145 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
 146         if (!ret) {
 147                 pc = (unsigned long)&ftrace_regs_call;
 148                 new = ftrace_call_replace(pc, (unsigned long)func, true);
 149
 150                 ret = ftrace_modify_code(pc, 0, new, false);
 151         }
 152 #endif
 153
 154 #ifdef CONFIG_OLD_MCOUNT
 155         if (!ret) {
 156                 pc = (unsigned long)&ftrace_call_old;
 157                 new = ftrace_call_replace(pc, (unsigned long)func, true);
 158
 159                 ret = ftrace_modify_code(pc, 0, new, false);
 160         }
 161 #endif
 162
 163         return ret;
 164 }
 165
 166 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 167 {
 168         unsigned long new, old;
 169         unsigned long ip = rec->ip;
 170         unsigned long aaddr = adjust_address(rec, addr);
 171         struct module *mod = NULL;
 172
 173 #ifdef CONFIG_ARM_MODULE_PLTS
 174         mod = rec->arch.mod;
 175 #endif
 176
 177         old = ftrace_nop_replace(rec);
 178
 179         new = ftrace_call_replace(ip, aaddr, !mod);
 180 #ifdef CONFIG_ARM_MODULE_PLTS
 181         if (!new && mod) {
 182                 aaddr = get_module_plt(mod, ip, aaddr);
 183                 new = ftrace_call_replace(ip, aaddr, true);
 184         }
 185 #endif
 186
 187         return ftrace_modify_code(rec->ip, old, new, true);
 188 }
 189
 190 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
 191
 192 int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
 193                                 unsigned long addr)
 194 {
 195         unsigned long new, old;
 196         unsigned long ip = rec->ip;
 197
 198         old = ftrace_call_replace(ip, adjust_address(rec, old_addr), true);
 199
 200         new = ftrace_call_replace(ip, adjust_address(rec, addr), true);
 201
 202         return ftrace_modify_code(rec->ip, old, new, true);
 203 }
 204
 205 #endif
 206
 207 int ftrace_make_nop(struct module *mod,
 208                     struct dyn_ftrace *rec, unsigned long addr)
 209 {
 210         unsigned long aaddr = adjust_address(rec, addr);
 211         unsigned long ip = rec->ip;
 212         unsigned long old;
 213         unsigned long new;
 214         int ret;
 215
 216 #ifdef CONFIG_ARM_MODULE_PLTS
 217         /* mod is only supplied during module loading */
 218         if (!mod)
 219                 mod = rec->arch.mod;
 220         else
 221                 rec->arch.mod = mod;
 222 #endif
 223
 224         old = ftrace_call_replace(ip, aaddr,
 225                                   !IS_ENABLED(CONFIG_ARM_MODULE_PLTS) || !mod);
 226 #ifdef CONFIG_ARM_MODULE_PLTS
 227         if (!old && mod) {
 228                 aaddr = get_module_plt(mod, ip, aaddr);
 229                 old = ftrace_call_replace(ip, aaddr, true);
 230         }
 231 #endif
 232
 233         new = ftrace_nop_replace(rec);
 234         ret = ftrace_modify_code(ip, old, new, true);
 235
 236 #ifdef CONFIG_OLD_MCOUNT
 237         if (ret == -EINVAL && addr == MCOUNT_ADDR) {
 238                 rec->arch.old_mcount = true;
 239
 240                 old = ftrace_call_replace(ip, adjust_address(rec, addr), true);
 241                 new = ftrace_nop_replace(rec);
 242                 ret = ftrace_modify_code(ip, old, new, true);
 243         }
 244 #endif
 245
 246         return ret;
 247 }
 248
 249 int __init ftrace_dyn_arch_init(void)
 250 {
 251         return 0;
 252 }
 253 #endif /* CONFIG_DYNAMIC_FTRACE */
 254
 255 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 256 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
 257                            unsigned long frame_pointer)
 258 {
 259         unsigned long return_hooker = (unsigned long) &return_to_handler;
 260         unsigned long old;
 261
 262         if (unlikely(atomic_read(&current->tracing_graph_pause)))
 263                 return;
 264
 265         old = *parent;
 266         *parent = return_hooker;
 267
 268         if (function_graph_enter(old, self_addr, frame_pointer, NULL))
 269                 *parent = old;
 270 }
 271
 272 #ifdef CONFIG_DYNAMIC_FTRACE
 273 extern unsigned long ftrace_graph_call;
 274 extern unsigned long ftrace_graph_call_old;
 275 extern void ftrace_graph_caller_old(void);
 276 extern unsigned long ftrace_graph_regs_call;
 277 extern void ftrace_graph_regs_caller(void);
 278
 279 static int __ftrace_modify_caller(unsigned long *callsite,
 280                                   void (*func) (void), bool enable)
 281 {
 282         unsigned long caller_fn = (unsigned long) func;
 283         unsigned long pc = (unsigned long) callsite;
 284         unsigned long branch = arm_gen_branch(pc, caller_fn);
 285         unsigned long nop = 0xe1a00000; /* mov r0, r0 */
 286         unsigned long old = enable ? nop : branch;
 287         unsigned long new = enable ? branch : nop;
 288
 289         return ftrace_modify_code(pc, old, new, true);
 290 }
 291
 292 static int ftrace_modify_graph_caller(bool enable)
 293 {
 294         int ret;
 295
 296         ret = __ftrace_modify_caller(&ftrace_graph_call,
 297                                      ftrace_graph_caller,
 298                                      enable);
 299
 300 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
 301         if (!ret)
 302                 ret = __ftrace_modify_caller(&ftrace_graph_regs_call,
 303                                      ftrace_graph_regs_caller,
 304                                      enable);
 305 #endif
 306
 307
 308 #ifdef CONFIG_OLD_MCOUNT
 309         if (!ret)
 310                 ret = __ftrace_modify_caller(&ftrace_graph_call_old,
 311                                              ftrace_graph_caller_old,
 312                                              enable);
 313 #endif
 314
 315         return ret;
 316 }
 317
 318 int ftrace_enable_ftrace_graph_caller(void)
 319 {
 320         return ftrace_modify_graph_caller(true);
 321 }
 322
 323 int ftrace_disable_ftrace_graph_caller(void)
 324 {
 325         return ftrace_modify_graph_caller(false);
 326 }
 327 #endif /* CONFIG_DYNAMIC_FTRACE */
 328 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */