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 #include <asm/patch.h>
  26
  27 #ifdef CONFIG_THUMB2_KERNEL
  28 #define NOP             0xf85deb04      /* pop.w {lr} */
  29 #else
  30 #define NOP             0xe8bd4000      /* pop {lr} */
  31 #endif
  32
  33 #ifdef CONFIG_DYNAMIC_FTRACE
  34
  35 static int __ftrace_modify_code(void *data)
  36 {
  37         int *command = data;
  38
  39         ftrace_modify_all_code(*command);
  40
  41         return 0;
  42 }
  43
  44 void arch_ftrace_update_code(int command)
  45 {
  46         stop_machine(__ftrace_modify_code, &command, NULL);
  47 }
  48
  49 static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
  50 {
  51         return NOP;
  52 }
  53
  54 static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
  55 {
  56         return addr;
  57 }
  58
  59 int ftrace_arch_code_modify_prepare(void)
  60 {
  61         return 0;
  62 }
  63
  64 int ftrace_arch_code_modify_post_process(void)
  65 {
  66         /* Make sure any TLB misses during machine stop are cleared. */
  67         flush_tlb_all();
  68         return 0;
  69 }
  70
  71 static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr,
  72                                          bool warn)
  73 {
  74         return arm_gen_branch_link(pc, addr, warn);
  75 }
  76
  77 static int ftrace_modify_code(unsigned long pc, unsigned long old,
  78                               unsigned long new, bool validate)
  79 {
  80         unsigned long replaced;
  81
  82         if (IS_ENABLED(CONFIG_THUMB2_KERNEL))
  83                 old = __opcode_to_mem_thumb32(old);
  84         else
  85                 old = __opcode_to_mem_arm(old);
  86
  87         if (validate) {
  88                 if (copy_from_kernel_nofault(&replaced, (void *)pc,
  89                                 MCOUNT_INSN_SIZE))
  90                         return -EFAULT;
  91
  92                 if (replaced != old)
  93                         return -EINVAL;
  94         }
  95
  96         __patch_text((void *)pc, new);
  97
  98         return 0;
  99 }
 100
 101 int ftrace_update_ftrace_func(ftrace_func_t func)
 102 {
 103         unsigned long pc;
 104         unsigned long new;
 105         int ret;
 106
 107         pc = (unsigned long)&ftrace_call;
 108         new = ftrace_call_replace(pc, (unsigned long)func, true);
 109
 110         ret = ftrace_modify_code(pc, 0, new, false);
 111
 112 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
 113         if (!ret) {
 114                 pc = (unsigned long)&ftrace_regs_call;
 115                 new = ftrace_call_replace(pc, (unsigned long)func, true);
 116
 117                 ret = ftrace_modify_code(pc, 0, new, false);
 118         }
 119 #endif
 120
 121         return ret;
 122 }
 123
 124 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 125 {
 126         unsigned long new, old;
 127         unsigned long ip = rec->ip;
 128         unsigned long aaddr = adjust_address(rec, addr);
 129         struct module *mod = NULL;
 130
 131 #ifdef CONFIG_ARM_MODULE_PLTS
 132         mod = rec->arch.mod;
 133 #endif
 134
 135         old = ftrace_nop_replace(rec);
 136
 137         new = ftrace_call_replace(ip, aaddr, !mod);
 138 #ifdef CONFIG_ARM_MODULE_PLTS
 139         if (!new && mod) {
 140                 aaddr = get_module_plt(mod, ip, aaddr);
 141                 new = ftrace_call_replace(ip, aaddr, true);
 142         }
 143 #endif
 144
 145         return ftrace_modify_code(rec->ip, old, new, true);
 146 }
 147
 148 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
 149
 150 int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
 151                                 unsigned long addr)
 152 {
 153         unsigned long new, old;
 154         unsigned long ip = rec->ip;
 155
 156         old = ftrace_call_replace(ip, adjust_address(rec, old_addr), true);
 157
 158         new = ftrace_call_replace(ip, adjust_address(rec, addr), true);
 159
 160         return ftrace_modify_code(rec->ip, old, new, true);
 161 }
 162
 163 #endif
 164
 165 int ftrace_make_nop(struct module *mod,
 166                     struct dyn_ftrace *rec, unsigned long addr)
 167 {
 168         unsigned long aaddr = adjust_address(rec, addr);
 169         unsigned long ip = rec->ip;
 170         unsigned long old;
 171         unsigned long new;
 172         int ret;
 173
 174 #ifdef CONFIG_ARM_MODULE_PLTS
 175         /* mod is only supplied during module loading */
 176         if (!mod)
 177                 mod = rec->arch.mod;
 178         else
 179                 rec->arch.mod = mod;
 180 #endif
 181
 182         old = ftrace_call_replace(ip, aaddr,
 183                                   !IS_ENABLED(CONFIG_ARM_MODULE_PLTS) || !mod);
 184 #ifdef CONFIG_ARM_MODULE_PLTS
 185         if (!old && mod) {
 186                 aaddr = get_module_plt(mod, ip, aaddr);
 187                 old = ftrace_call_replace(ip, aaddr, true);
 188         }
 189 #endif
 190
 191         new = ftrace_nop_replace(rec);
 192         ret = ftrace_modify_code(ip, old, new, true);
 193
 194         return ret;
 195 }
 196
 197 int __init ftrace_dyn_arch_init(void)
 198 {
 199         return 0;
 200 }
 201 #endif /* CONFIG_DYNAMIC_FTRACE */
 202
 203 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 204 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
 205                            unsigned long frame_pointer)
 206 {
 207         unsigned long return_hooker = (unsigned long) &return_to_handler;
 208         unsigned long old;
 209
 210         if (unlikely(atomic_read(&current->tracing_graph_pause)))
 211                 return;
 212
 213         old = *parent;
 214         *parent = return_hooker;
 215
 216         if (function_graph_enter(old, self_addr, frame_pointer, NULL))
 217                 *parent = old;
 218 }
 219
 220 #ifdef CONFIG_DYNAMIC_FTRACE
 221 extern unsigned long ftrace_graph_call;
 222 extern unsigned long ftrace_graph_call_old;
 223 extern void ftrace_graph_caller_old(void);
 224 extern unsigned long ftrace_graph_regs_call;
 225 extern void ftrace_graph_regs_caller(void);
 226
 227 static int __ftrace_modify_caller(unsigned long *callsite,
 228                                   void (*func) (void), bool enable)
 229 {
 230         unsigned long caller_fn = (unsigned long) func;
 231         unsigned long pc = (unsigned long) callsite;
 232         unsigned long branch = arm_gen_branch(pc, caller_fn);
 233         unsigned long nop = 0xe1a00000; /* mov r0, r0 */
 234         unsigned long old = enable ? nop : branch;
 235         unsigned long new = enable ? branch : nop;
 236
 237         return ftrace_modify_code(pc, old, new, true);
 238 }
 239
 240 static int ftrace_modify_graph_caller(bool enable)
 241 {
 242         int ret;
 243
 244         ret = __ftrace_modify_caller(&ftrace_graph_call,
 245                                      ftrace_graph_caller,
 246                                      enable);
 247
 248 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
 249         if (!ret)
 250                 ret = __ftrace_modify_caller(&ftrace_graph_regs_call,
 251                                      ftrace_graph_regs_caller,
 252                                      enable);
 253 #endif
 254
 255
 256         return ret;
 257 }
 258
 259 int ftrace_enable_ftrace_graph_caller(void)
 260 {
 261         return ftrace_modify_graph_caller(true);
 262 }
 263
 264 int ftrace_disable_ftrace_graph_caller(void)
 265 {
 266         return ftrace_modify_graph_caller(false);
 267 }
 268 #endif /* CONFIG_DYNAMIC_FTRACE */
 269 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */