arch/riscv/kernel/ftrace.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2013 Linaro Limited
   4  * Author: AKASHI Takahiro <takahiro.akashi@linaro.org>
   5  * Copyright (C) 2017 Andes Technology Corporation
   6  */
   7
   8 #include <linux/ftrace.h>
   9 #include <linux/uaccess.h>
  10 #include <linux/memory.h>
  11 #include <asm/cacheflush.h>
  12 #include <asm/patch.h>
  13
  14 #ifdef CONFIG_DYNAMIC_FTRACE
  15 int ftrace_arch_code_modify_prepare(void) __acquires(&text_mutex)
  16 {
  17         mutex_lock(&text_mutex);
  18         return 0;
  19 }
  20
  21 int ftrace_arch_code_modify_post_process(void) __releases(&text_mutex)
  22 {
  23         mutex_unlock(&text_mutex);
  24         return 0;
  25 }
  26
  27 static int ftrace_check_current_call(unsigned long hook_pos,
  28                                      unsigned int *expected)
  29 {
  30         unsigned int replaced[2];
  31         unsigned int nops[2] = {NOP4, NOP4};
  32
  33         /* we expect nops at the hook position */
  34         if (!expected)
  35                 expected = nops;
  36
  37         /*
  38          * Read the text we want to modify;
  39          * return must be -EFAULT on read error
  40          */
  41         if (copy_from_kernel_nofault(replaced, (void *)hook_pos,
  42                         MCOUNT_INSN_SIZE))
  43                 return -EFAULT;
  44
  45         /*
  46          * Make sure it is what we expect it to be;
  47          * return must be -EINVAL on failed comparison
  48          */
  49         if (memcmp(expected, replaced, sizeof(replaced))) {
  50                 pr_err("%p: expected (%08x %08x) but got (%08x %08x)\n",
  51                        (void *)hook_pos, expected[0], expected[1], replaced[0],
  52                        replaced[1]);
  53                 return -EINVAL;
  54         }
  55
  56         return 0;
  57 }
  58
  59 static int __ftrace_modify_call(unsigned long hook_pos, unsigned long target,
  60                                 bool enable)
  61 {
  62         unsigned int call[2];
  63         unsigned int nops[2] = {NOP4, NOP4};
  64
  65         make_call(hook_pos, target, call);
  66
  67         /* Replace the auipc-jalr pair at once. Return -EPERM on write error. */
  68         if (patch_text_nosync
  69             ((void *)hook_pos, enable ? call : nops, MCOUNT_INSN_SIZE))
  70                 return -EPERM;
  71
  72         return 0;
  73 }
  74
  75 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
  76 {
  77         int ret = ftrace_check_current_call(rec->ip, NULL);
  78
  79         if (ret)
  80                 return ret;
  81
  82         return __ftrace_modify_call(rec->ip, addr, true);
  83 }
  84
  85 int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
  86                     unsigned long addr)
  87 {
  88         unsigned int call[2];
  89         int ret;
  90
  91         make_call(rec->ip, addr, call);
  92         ret = ftrace_check_current_call(rec->ip, call);
  93
  94         if (ret)
  95                 return ret;
  96
  97         return __ftrace_modify_call(rec->ip, addr, false);
  98 }
  99
 100
 101 /*
 102  * This is called early on, and isn't wrapped by
 103  * ftrace_arch_code_modify_{prepare,post_process}() and therefor doesn't hold
 104  * text_mutex, which triggers a lockdep failure.  SMP isn't running so we could
 105  * just directly poke the text, but it's simpler to just take the lock
 106  * ourselves.
 107  */
 108 int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
 109 {
 110         int out;
 111
 112         ftrace_arch_code_modify_prepare();
 113         out = ftrace_make_nop(mod, rec, MCOUNT_ADDR);
 114         ftrace_arch_code_modify_post_process();
 115
 116         return out;
 117 }
 118
 119 int ftrace_update_ftrace_func(ftrace_func_t func)
 120 {
 121         int ret = __ftrace_modify_call((unsigned long)&ftrace_call,
 122                                        (unsigned long)func, true);
 123         if (!ret) {
 124                 ret = __ftrace_modify_call((unsigned long)&ftrace_regs_call,
 125                                            (unsigned long)func, true);
 126         }
 127
 128         return ret;
 129 }
 130
 131 int __init ftrace_dyn_arch_init(void)
 132 {
 133         return 0;
 134 }
 135 #endif
 136
 137 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
 138 int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
 139                        unsigned long addr)
 140 {
 141         unsigned int call[2];
 142         int ret;
 143
 144         make_call(rec->ip, old_addr, call);
 145         ret = ftrace_check_current_call(rec->ip, call);
 146
 147         if (ret)
 148                 return ret;
 149
 150         return __ftrace_modify_call(rec->ip, addr, true);
 151 }
 152 #endif
 153
 154 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 155 /*
 156  * Most of this function is copied from arm64.
 157  */
 158 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
 159                            unsigned long frame_pointer)
 160 {
 161         unsigned long return_hooker = (unsigned long)&return_to_handler;
 162         unsigned long old;
 163
 164         if (unlikely(atomic_read(&current->tracing_graph_pause)))
 165                 return;
 166
 167         /*
 168          * We don't suffer access faults, so no extra fault-recovery assembly
 169          * is needed here.
 170          */
 171         old = *parent;
 172
 173         if (!function_graph_enter(old, self_addr, frame_pointer, parent))
 174                 *parent = return_hooker;
 175 }
 176
 177 #ifdef CONFIG_DYNAMIC_FTRACE
 178 extern void ftrace_graph_call(void);
 179 int ftrace_enable_ftrace_graph_caller(void)
 180 {
 181         unsigned int call[2];
 182         static int init_graph = 1;
 183         int ret;
 184
 185         make_call(&ftrace_graph_call, &ftrace_stub, call);
 186
 187         /*
 188          * When enabling graph tracer for the first time, ftrace_graph_call
 189          * should contains a call to ftrace_stub.  Once it has been disabled,
 190          * the 8-bytes at the position becomes NOPs.
 191          */
 192         if (init_graph) {
 193                 ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call,
 194                                                 call);
 195                 init_graph = 0;
 196         } else {
 197                 ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call,
 198                                                 NULL);
 199         }
 200
 201         if (ret)
 202                 return ret;
 203
 204         return __ftrace_modify_call((unsigned long)&ftrace_graph_call,
 205                                     (unsigned long)&prepare_ftrace_return, true);
 206 }
 207
 208 int ftrace_disable_ftrace_graph_caller(void)
 209 {
 210         unsigned int call[2];
 211         int ret;
 212
 213         make_call(&ftrace_graph_call, &prepare_ftrace_return, call);
 214
 215         /*
 216          * This is to make sure that ftrace_enable_ftrace_graph_caller
 217          * did the right thing.
 218          */
 219         ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call,
 220                                         call);
 221
 222         if (ret)
 223                 return ret;
 224
 225         return __ftrace_modify_call((unsigned long)&ftrace_graph_call,
 226                                     (unsigned long)&prepare_ftrace_return, false);
 227 }
 228 #endif /* CONFIG_DYNAMIC_FTRACE */
 229 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */