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