arch/sh/kernel/ftrace.c

   1 /*
   2  * Copyright (C) 2008 Matt Fleming <matt@console-pimps.org>
   3  * Copyright (C) 2008 Paul Mundt <lethal@linux-sh.org>
   4  *
   5  * Code for replacing ftrace calls with jumps.
   6  *
   7  * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
   8  *
   9  * Thanks goes to Ingo Molnar, for suggesting the idea.
  10  * Mathieu Desnoyers, for suggesting postponing the modifications.
  11  * Arjan van de Ven, for keeping me straight, and explaining to me
  12  * the dangers of modifying code on the run.
  13  */
  14 #include <linux/uaccess.h>
  15 #include <linux/ftrace.h>
  16 #include <linux/string.h>
  17 #include <linux/init.h>
  18 #include <linux/io.h>
  19 #include <linux/kernel.h>
  20 #include <asm/ftrace.h>
  21 #include <asm/cacheflush.h>
  22 #include <asm/unistd.h>
  23 #include <trace/syscall.h>
  24
  25 #ifdef CONFIG_DYNAMIC_FTRACE
  26 static unsigned char ftrace_replaced_code[MCOUNT_INSN_SIZE];
  27
  28 static unsigned char ftrace_nop[4];
  29 /*
  30  * If we're trying to nop out a call to a function, we instead
  31  * place a call to the address after the memory table.
  32  *
  33  * 8c011060 <a>:
  34  * 8c011060:       02 d1           mov.l   8c01106c <a+0xc>,r1
  35  * 8c011062:       22 4f           sts.l   pr,@-r15
  36  * 8c011064:       02 c7           mova    8c011070 <a+0x10>,r0
  37  * 8c011066:       2b 41           jmp     @r1
  38  * 8c011068:       2a 40           lds     r0,pr
  39  * 8c01106a:       09 00           nop
  40  * 8c01106c:       68 24           .word 0x2468     <--- ip
  41  * 8c01106e:       1d 8c           .word 0x8c1d
  42  * 8c011070:       26 4f           lds.l   @r15+,pr <--- ip + MCOUNT_INSN_SIZE
  43  *
  44  * We write 0x8c011070 to 0x8c01106c so that on entry to a() we branch
  45  * past the _mcount call and continue executing code like normal.
  46  */
  47 static unsigned char *ftrace_nop_replace(unsigned long ip)
  48 {
  49         __raw_writel(ip + MCOUNT_INSN_SIZE, ftrace_nop);
  50         return ftrace_nop;
  51 }
  52
  53 static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
  54 {
  55         /* Place the address in the memory table. */
  56         __raw_writel(addr, ftrace_replaced_code);
  57
  58         /*
  59          * No locking needed, this must be called via kstop_machine
  60          * which in essence is like running on a uniprocessor machine.
  61          */
  62         return ftrace_replaced_code;
  63 }
  64
  65 static int ftrace_modify_code(unsigned long ip, unsigned char *old_code,
  66                        unsigned char *new_code)
  67 {
  68         unsigned char replaced[MCOUNT_INSN_SIZE];
  69
  70         /*
  71          * Note: Due to modules and __init, code can
  72          *  disappear and change, we need to protect against faulting
  73          *  as well as code changing. We do this by using the
  74          *  probe_kernel_* functions.
  75          *
  76          * No real locking needed, this code is run through
  77          * kstop_machine, or before SMP starts.
  78          */
  79
  80         /* read the text we want to modify */
  81         if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
  82                 return -EFAULT;
  83
  84         /* Make sure it is what we expect it to be */
  85         if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
  86                 return -EINVAL;
  87
  88         /* replace the text with the new text */
  89         if (probe_kernel_write((void *)ip, new_code, MCOUNT_INSN_SIZE))
  90                 return -EPERM;
  91
  92         flush_icache_range(ip, ip + MCOUNT_INSN_SIZE);
  93
  94         return 0;
  95 }
  96
  97 int ftrace_update_ftrace_func(ftrace_func_t func)
  98 {
  99         unsigned long ip = (unsigned long)(&ftrace_call) + MCOUNT_INSN_OFFSET;
 100         unsigned char old[MCOUNT_INSN_SIZE], *new;
 101
 102         memcpy(old, (unsigned char *)ip, MCOUNT_INSN_SIZE);
 103         new = ftrace_call_replace(ip, (unsigned long)func);
 104
 105         return ftrace_modify_code(ip, old, new);
 106 }
 107
 108 int ftrace_make_nop(struct module *mod,
 109                     struct dyn_ftrace *rec, unsigned long addr)
 110 {
 111         unsigned char *new, *old;
 112         unsigned long ip = rec->ip;
 113
 114         old = ftrace_call_replace(ip, addr);
 115         new = ftrace_nop_replace(ip);
 116
 117         return ftrace_modify_code(rec->ip, old, new);
 118 }
 119
 120 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 121 {
 122         unsigned char *new, *old;
 123         unsigned long ip = rec->ip;
 124
 125         old = ftrace_nop_replace(ip);
 126         new = ftrace_call_replace(ip, addr);
 127
 128         return ftrace_modify_code(rec->ip, old, new);
 129 }
 130
 131 int __init ftrace_dyn_arch_init(void *data)
 132 {
 133         /* The return code is retured via data */
 134         __raw_writel(0, (unsigned long)data);
 135
 136         return 0;
 137 }
 138 #endif /* CONFIG_DYNAMIC_FTRACE */
 139
 140 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 141 #ifdef CONFIG_DYNAMIC_FTRACE
 142 extern void ftrace_graph_call(void);
 143
 144 static int ftrace_mod(unsigned long ip, unsigned long old_addr,
 145                       unsigned long new_addr)
 146 {
 147         unsigned char code[MCOUNT_INSN_SIZE];
 148
 149         if (probe_kernel_read(code, (void *)ip, MCOUNT_INSN_SIZE))
 150                 return -EFAULT;
 151
 152         if (old_addr != __raw_readl((unsigned long *)code))
 153                 return -EINVAL;
 154
 155         __raw_writel(new_addr, ip);
 156         return 0;
 157 }
 158
 159 int ftrace_enable_ftrace_graph_caller(void)
 160 {
 161         unsigned long ip, old_addr, new_addr;
 162
 163         ip = (unsigned long)(&ftrace_graph_call) + GRAPH_INSN_OFFSET;
 164         old_addr = (unsigned long)(&skip_trace);
 165         new_addr = (unsigned long)(&ftrace_graph_caller);
 166
 167         return ftrace_mod(ip, old_addr, new_addr);
 168 }
 169
 170 int ftrace_disable_ftrace_graph_caller(void)
 171 {
 172         unsigned long ip, old_addr, new_addr;
 173
 174         ip = (unsigned long)(&ftrace_graph_call) + GRAPH_INSN_OFFSET;
 175         old_addr = (unsigned long)(&ftrace_graph_caller);
 176         new_addr = (unsigned long)(&skip_trace);
 177
 178         return ftrace_mod(ip, old_addr, new_addr);
 179 }
 180 #endif /* CONFIG_DYNAMIC_FTRACE */
 181
 182 /*
 183  * Hook the return address and push it in the stack of return addrs
 184  * in the current thread info.
 185  *
 186  * This is the main routine for the function graph tracer. The function
 187  * graph tracer essentially works like this:
 188  *
 189  * parent is the stack address containing self_addr's return address.
 190  * We pull the real return address out of parent and store it in
 191  * current's ret_stack. Then, we replace the return address on the stack
 192  * with the address of return_to_handler. self_addr is the function that
 193  * called mcount.
 194  *
 195  * When self_addr returns, it will jump to return_to_handler which calls
 196  * ftrace_return_to_handler. ftrace_return_to_handler will pull the real
 197  * return address off of current's ret_stack and jump to it.
 198  */
 199 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
 200 {
 201         unsigned long old;
 202         int faulted, err;
 203         struct ftrace_graph_ent trace;
 204         unsigned long return_hooker = (unsigned long)&return_to_handler;
 205
 206         if (unlikely(atomic_read(&current->tracing_graph_pause)))
 207                 return;
 208
 209         /*
 210          * Protect against fault, even if it shouldn't
 211          * happen. This tool is too much intrusive to
 212          * ignore such a protection.
 213          */
 214         __asm__ __volatile__(
 215                 "1:                                             \n\t"
 216                 "mov.l          @%2, %0                         \n\t"
 217                 "2:                                             \n\t"
 218                 "mov.l          %3, @%2                         \n\t"
 219                 "mov            #0, %1                          \n\t"
 220                 "3:                                             \n\t"
 221                 ".section .fixup, \"ax\"                        \n\t"
 222                 "4:                                             \n\t"
 223                 "mov.l          5f, %0                          \n\t"
 224                 "jmp            @%0                             \n\t"
 225                 " mov           #1, %1                          \n\t"
 226                 ".balign 4                                      \n\t"
 227                 "5:     .long 3b                                \n\t"
 228                 ".previous                                      \n\t"
 229                 ".section __ex_table,\"a\"                      \n\t"
 230                 ".long 1b, 4b                                   \n\t"
 231                 ".long 2b, 4b                                   \n\t"
 232                 ".previous                                      \n\t"
 233                 : "=&r" (old), "=r" (faulted)
 234                 : "r" (parent), "r" (return_hooker)
 235         );
 236
 237         if (unlikely(faulted)) {
 238                 ftrace_graph_stop();
 239                 WARN_ON(1);
 240                 return;
 241         }
 242
 243         err = ftrace_push_return_trace(old, self_addr, &trace.depth, 0);
 244         if (err == -EBUSY) {
 245                 __raw_writel(old, parent);
 246                 return;
 247         }
 248
 249         trace.func = self_addr;
 250
 251         /* Only trace if the calling function expects to */
 252         if (!ftrace_graph_entry(&trace)) {
 253                 current->curr_ret_stack--;
 254                 __raw_writel(old, parent);
 255         }
 256 }
 257 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
 258
 259 #ifdef CONFIG_FTRACE_SYSCALLS
 260
 261 extern unsigned long __start_syscalls_metadata[];
 262 extern unsigned long __stop_syscalls_metadata[];
 263 extern unsigned long *sys_call_table;
 264
 265 static struct syscall_metadata **syscalls_metadata;
 266
 267 static struct syscall_metadata *find_syscall_meta(unsigned long *syscall)
 268 {
 269         struct syscall_metadata *start;
 270         struct syscall_metadata *stop;
 271         char str[KSYM_SYMBOL_LEN];
 272
 273
 274         start = (struct syscall_metadata *)__start_syscalls_metadata;
 275         stop = (struct syscall_metadata *)__stop_syscalls_metadata;
 276         kallsyms_lookup((unsigned long) syscall, NULL, NULL, NULL, str);
 277
 278         for ( ; start < stop; start++) {
 279                 if (start->name && !strcmp(start->name, str))
 280                         return start;
 281         }
 282
 283         return NULL;
 284 }
 285
 286 struct syscall_metadata *syscall_nr_to_meta(int nr)
 287 {
 288         if (!syscalls_metadata || nr >= FTRACE_SYSCALL_MAX || nr < 0)
 289                 return NULL;
 290
 291         return syscalls_metadata[nr];
 292 }
 293
 294 int syscall_name_to_nr(char *name)
 295 {
 296         int i;
 297
 298         if (!syscalls_metadata)
 299                 return -1;
 300         for (i = 0; i < NR_syscalls; i++)
 301                 if (syscalls_metadata[i])
 302                         if (!strcmp(syscalls_metadata[i]->name, name))
 303                                 return i;
 304         return -1;
 305 }
 306
 307 void set_syscall_enter_id(int num, int id)
 308 {
 309         syscalls_metadata[num]->enter_id = id;
 310 }
 311
 312 void set_syscall_exit_id(int num, int id)
 313 {
 314         syscalls_metadata[num]->exit_id = id;
 315 }
 316
 317 static int __init arch_init_ftrace_syscalls(void)
 318 {
 319         int i;
 320         struct syscall_metadata *meta;
 321         unsigned long **psys_syscall_table = &sys_call_table;
 322
 323         syscalls_metadata = kzalloc(sizeof(*syscalls_metadata) *
 324                                         FTRACE_SYSCALL_MAX, GFP_KERNEL);
 325         if (!syscalls_metadata) {
 326                 WARN_ON(1);
 327                 return -ENOMEM;
 328         }
 329
 330         for (i = 0; i < FTRACE_SYSCALL_MAX; i++) {
 331                 meta = find_syscall_meta(psys_syscall_table[i]);
 332                 syscalls_metadata[i] = meta;
 333         }
 334
 335         return 0;
 336 }
 337 arch_initcall(arch_init_ftrace_syscalls);
 338 #endif /* CONFIG_FTRACE_SYSCALLS */