arch/s390/kernel/ftrace.c

   1 /*
   2  * Dynamic function tracer architecture backend.
   3  *
   4  * Copyright IBM Corp. 2009
   5  *
   6  *   Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>,
   7  *
   8  */
   9
  10 #include <linux/hardirq.h>
  11 #include <linux/uaccess.h>
  12 #include <linux/ftrace.h>
  13 #include <linux/kernel.h>
  14 #include <linux/types.h>
  15 #include <trace/syscall.h>
  16 #include <asm/asm-offsets.h>
  17
  18 #ifdef CONFIG_DYNAMIC_FTRACE
  19
  20 void ftrace_disable_code(void);
  21 void ftrace_disable_return(void);
  22 void ftrace_call_code(void);
  23 void ftrace_nop_code(void);
  24
  25 #define FTRACE_INSN_SIZE 4
  26
  27 #ifdef CONFIG_64BIT
  28
  29 asm(
  30         "       .align  4\n"
  31         "ftrace_disable_code:\n"
  32         "       j       0f\n"
  33         "       .word   0x0024\n"
  34         "       lg      %r1,"__stringify(__LC_FTRACE_FUNC)"\n"
  35         "       basr    %r14,%r1\n"
  36         "ftrace_disable_return:\n"
  37         "       lg      %r14,8(15)\n"
  38         "       lgr     %r0,%r0\n"
  39         "0:\n");
  40
  41 asm(
  42         "       .align  4\n"
  43         "ftrace_nop_code:\n"
  44         "       j       .+"__stringify(MCOUNT_INSN_SIZE)"\n");
  45
  46 asm(
  47         "       .align  4\n"
  48         "ftrace_call_code:\n"
  49         "       stg     %r14,8(%r15)\n");
  50
  51 #else /* CONFIG_64BIT */
  52
  53 asm(
  54         "       .align  4\n"
  55         "ftrace_disable_code:\n"
  56         "       j       0f\n"
  57         "       l       %r1,"__stringify(__LC_FTRACE_FUNC)"\n"
  58         "       basr    %r14,%r1\n"
  59         "ftrace_disable_return:\n"
  60         "       l       %r14,4(%r15)\n"
  61         "       j       0f\n"
  62         "       bcr     0,%r7\n"
  63         "       bcr     0,%r7\n"
  64         "       bcr     0,%r7\n"
  65         "       bcr     0,%r7\n"
  66         "       bcr     0,%r7\n"
  67         "       bcr     0,%r7\n"
  68         "0:\n");
  69
  70 asm(
  71         "       .align  4\n"
  72         "ftrace_nop_code:\n"
  73         "       j       .+"__stringify(MCOUNT_INSN_SIZE)"\n");
  74
  75 asm(
  76         "       .align  4\n"
  77         "ftrace_call_code:\n"
  78         "       st      %r14,4(%r15)\n");
  79
  80 #endif /* CONFIG_64BIT */
  81
  82 static int ftrace_modify_code(unsigned long ip,
  83                               void *old_code, int old_size,
  84                               void *new_code, int new_size)
  85 {
  86         unsigned char replaced[MCOUNT_INSN_SIZE];
  87
  88         /*
  89          * Note: Due to modules code can disappear and change.
  90          *  We need to protect against faulting as well as code
  91          *  changing. We do this by using the probe_kernel_*
  92          *  functions.
  93          *  This however is just a simple sanity check.
  94          */
  95         if (probe_kernel_read(replaced, (void *)ip, old_size))
  96                 return -EFAULT;
  97         if (memcmp(replaced, old_code, old_size) != 0)
  98                 return -EINVAL;
  99         if (probe_kernel_write((void *)ip, new_code, new_size))
 100                 return -EPERM;
 101         return 0;
 102 }
 103
 104 static int ftrace_make_initial_nop(struct module *mod, struct dyn_ftrace *rec,
 105                                    unsigned long addr)
 106 {
 107         return ftrace_modify_code(rec->ip,
 108                                   ftrace_call_code, FTRACE_INSN_SIZE,
 109                                   ftrace_disable_code, MCOUNT_INSN_SIZE);
 110 }
 111
 112 int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
 113                     unsigned long addr)
 114 {
 115         if (addr == MCOUNT_ADDR)
 116                 return ftrace_make_initial_nop(mod, rec, addr);
 117         return ftrace_modify_code(rec->ip,
 118                                   ftrace_call_code, FTRACE_INSN_SIZE,
 119                                   ftrace_nop_code, FTRACE_INSN_SIZE);
 120 }
 121
 122 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 123 {
 124         return ftrace_modify_code(rec->ip,
 125                                   ftrace_nop_code, FTRACE_INSN_SIZE,
 126                                   ftrace_call_code, FTRACE_INSN_SIZE);
 127 }
 128
 129 int ftrace_update_ftrace_func(ftrace_func_t func)
 130 {
 131         ftrace_dyn_func = (unsigned long)func;
 132         return 0;
 133 }
 134
 135 int __init ftrace_dyn_arch_init(void *data)
 136 {
 137         *(unsigned long *)data = 0;
 138         return 0;
 139 }
 140
 141 #endif /* CONFIG_DYNAMIC_FTRACE */
 142
 143 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 144 #ifdef CONFIG_DYNAMIC_FTRACE
 145 /*
 146  * Patch the kernel code at ftrace_graph_caller location:
 147  * The instruction there is branch relative on condition. The condition mask
 148  * is either all ones (always branch aka disable ftrace_graph_caller) or all
 149  * zeroes (nop aka enable ftrace_graph_caller).
 150  * Instruction format for brc is a7m4xxxx where m is the condition mask.
 151  */
 152 int ftrace_enable_ftrace_graph_caller(void)
 153 {
 154         unsigned short opcode = 0xa704;
 155
 156         return probe_kernel_write(ftrace_graph_caller, &opcode, sizeof(opcode));
 157 }
 158
 159 int ftrace_disable_ftrace_graph_caller(void)
 160 {
 161         unsigned short opcode = 0xa7f4;
 162
 163         return probe_kernel_write(ftrace_graph_caller, &opcode, sizeof(opcode));
 164 }
 165
 166 static inline unsigned long ftrace_mcount_call_adjust(unsigned long addr)
 167 {
 168         return addr - (ftrace_disable_return - ftrace_disable_code);
 169 }
 170
 171 #else /* CONFIG_DYNAMIC_FTRACE */
 172
 173 static inline unsigned long ftrace_mcount_call_adjust(unsigned long addr)
 174 {
 175         return addr - MCOUNT_OFFSET_RET;
 176 }
 177
 178 #endif /* CONFIG_DYNAMIC_FTRACE */
 179
 180 /*
 181  * Hook the return address and push it in the stack of return addresses
 182  * in current thread info.
 183  */
 184 unsigned long prepare_ftrace_return(unsigned long ip, unsigned long parent)
 185 {
 186         struct ftrace_graph_ent trace;
 187
 188         if (unlikely(atomic_read(&current->tracing_graph_pause)))
 189                 goto out;
 190         if (ftrace_push_return_trace(parent, ip, &trace.depth, 0) == -EBUSY)
 191                 goto out;
 192         trace.func = ftrace_mcount_call_adjust(ip) & PSW_ADDR_INSN;
 193         /* Only trace if the calling function expects to. */
 194         if (!ftrace_graph_entry(&trace)) {
 195                 current->curr_ret_stack--;
 196                 goto out;
 197         }
 198         parent = (unsigned long)return_to_handler;
 199 out:
 200         return parent;
 201 }
 202 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */