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 {
  73         return arm_gen_branch_link(pc, addr);
  74 }
  75
  76 static int ftrace_modify_code(unsigned long pc, unsigned long old,
  77                               unsigned long new, bool validate)
  78 {
  79         unsigned long replaced;
  80
  81         if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) {
  82                 old = __opcode_to_mem_thumb32(old);
  83                 new = __opcode_to_mem_thumb32(new);
  84         } else {
  85                 old = __opcode_to_mem_arm(old);
  86                 new = __opcode_to_mem_arm(new);
  87         }
  88
  89         if (validate) {
  90                 if (probe_kernel_read(&replaced, (void *)pc, MCOUNT_INSN_SIZE))
  91                         return -EFAULT;
  92
  93                 if (replaced != old)
  94                         return -EINVAL;
  95         }
  96
  97         __patch_text((void *)pc, new);
  98
  99         return 0;
 100 }
 101
 102 int ftrace_update_ftrace_func(ftrace_func_t func)
 103 {
 104         unsigned long pc;
 105         unsigned long new;
 106         int ret;
 107
 108         pc = (unsigned long)&ftrace_call;
 109         new = ftrace_call_replace(pc, (unsigned long)func);
 110
 111         ret = ftrace_modify_code(pc, 0, new, false);
 112
 113 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
 114         if (!ret) {
 115                 pc = (unsigned long)&ftrace_regs_call;
 116                 new = ftrace_call_replace(pc, (unsigned long)func);
 117
 118                 ret = ftrace_modify_code(pc, 0, new, false);
 119         }
 120 #endif
 121
 122         return ret;
 123 }
 124
 125 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 126 {
 127         unsigned long new, old;
 128         unsigned long ip = rec->ip;
 129
 130         old = ftrace_nop_replace(rec);
 131
 132         new = ftrace_call_replace(ip, adjust_address(rec, addr));
 133
 134         return ftrace_modify_code(rec->ip, old, new, true);
 135 }
 136
 137 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
 138
 139 int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
 140                                 unsigned long addr)
 141 {
 142         unsigned long new, old;
 143         unsigned long ip = rec->ip;
 144
 145         old = ftrace_call_replace(ip, adjust_address(rec, old_addr));
 146
 147         new = ftrace_call_replace(ip, adjust_address(rec, addr));
 148
 149         return ftrace_modify_code(rec->ip, old, new, true);
 150 }
 151
 152 #endif
 153
 154 int ftrace_make_nop(struct module *mod,
 155                     struct dyn_ftrace *rec, unsigned long addr)
 156 {
 157         unsigned long ip = rec->ip;
 158         unsigned long old;
 159         unsigned long new;
 160         int ret;
 161
 162         old = ftrace_call_replace(ip, adjust_address(rec, addr));
 163         new = ftrace_nop_replace(rec);
 164         ret = ftrace_modify_code(ip, old, new, true);
 165
 166         return ret;
 167 }
 168
 169 int __init ftrace_dyn_arch_init(void)
 170 {
 171         return 0;
 172 }
 173 #endif /* CONFIG_DYNAMIC_FTRACE */
 174
 175 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 176 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
 177                            unsigned long frame_pointer)
 178 {
 179         unsigned long return_hooker = (unsigned long) &return_to_handler;
 180         unsigned long old;
 181
 182         if (unlikely(atomic_read(&current->tracing_graph_pause)))
 183                 return;
 184
 185         old = *parent;
 186         *parent = return_hooker;
 187
 188         if (function_graph_enter(old, self_addr, frame_pointer, NULL))
 189                 *parent = old;
 190 }
 191
 192 #ifdef CONFIG_DYNAMIC_FTRACE
 193 extern unsigned long ftrace_graph_call;
 194 extern unsigned long ftrace_graph_call_old;
 195 extern void ftrace_graph_caller_old(void);
 196 extern unsigned long ftrace_graph_regs_call;
 197 extern void ftrace_graph_regs_caller(void);
 198
 199 static int __ftrace_modify_caller(unsigned long *callsite,
 200                                   void (*func) (void), bool enable)
 201 {
 202         unsigned long caller_fn = (unsigned long) func;
 203         unsigned long pc = (unsigned long) callsite;
 204         unsigned long branch = arm_gen_branch(pc, caller_fn);
 205         unsigned long nop = 0xe1a00000; /* mov r0, r0 */
 206         unsigned long old = enable ? nop : branch;
 207         unsigned long new = enable ? branch : nop;
 208
 209         return ftrace_modify_code(pc, old, new, true);
 210 }
 211
 212 static int ftrace_modify_graph_caller(bool enable)
 213 {
 214         int ret;
 215
 216         ret = __ftrace_modify_caller(&ftrace_graph_call,
 217                                      ftrace_graph_caller,
 218                                      enable);
 219
 220 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
 221         if (!ret)
 222                 ret = __ftrace_modify_caller(&ftrace_graph_regs_call,
 223                                      ftrace_graph_regs_caller,
 224                                      enable);
 225 #endif
 226
 227
 228         return ret;
 229 }
 230
 231 int ftrace_enable_ftrace_graph_caller(void)
 232 {
 233         return ftrace_modify_graph_caller(true);
 234 }
 235
 236 int ftrace_disable_ftrace_graph_caller(void)
 237 {
 238         return ftrace_modify_graph_caller(false);
 239 }
 240 #endif /* CONFIG_DYNAMIC_FTRACE */
 241 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */