arch/ia64/kernel/ftrace.c

   1 /*
   2  * Dynamic function tracing support.
   3  *
   4  * Copyright (C) 2008 Shaohua Li <shaohua.li@intel.com>
   5  *
   6  * For licencing details, see COPYING.
   7  *
   8  * Defines low-level handling of mcount calls when the kernel
   9  * is compiled with the -pg flag. When using dynamic ftrace, the
  10  * mcount call-sites get patched lazily with NOP till they are
  11  * enabled. All code mutation routines here take effect atomically.
  12  */
  13
  14 #include <linux/uaccess.h>
  15 #include <linux/ftrace.h>
  16
  17 #include <asm/cacheflush.h>
  18 #include <asm/patch.h>
  19
  20 /* In IA64, each function will be added below two bundles with -pg option */
  21 static unsigned char __attribute__((aligned(8)))
  22 ftrace_orig_code[MCOUNT_INSN_SIZE] = {
  23         0x02, 0x40, 0x31, 0x10, 0x80, 0x05, /* alloc r40=ar.pfs,12,8,0 */
  24         0xb0, 0x02, 0x00, 0x00, 0x42, 0x40, /* mov r43=r0;; */
  25         0x05, 0x00, 0xc4, 0x00,             /* mov r42=b0 */
  26         0x11, 0x48, 0x01, 0x02, 0x00, 0x21, /* mov r41=r1 */
  27         0x00, 0x00, 0x00, 0x02, 0x00, 0x00, /* nop.i 0x0 */
  28         0x08, 0x00, 0x00, 0x50              /* br.call.sptk.many b0 = _mcount;; */
  29 };
  30
  31 struct ftrace_orig_insn {
  32         u64 dummy1, dummy2, dummy3;
  33         u64 dummy4:64-41+13;
  34         u64 imm20:20;
  35         u64 dummy5:3;
  36         u64 sign:1;
  37         u64 dummy6:4;
  38 };
  39
  40 /* mcount stub will be converted below for nop */
  41 static unsigned char ftrace_nop_code[MCOUNT_INSN_SIZE] = {
  42         0x00, 0x00, 0x00, 0x00, 0x01, 0x00, /* [MII] nop.m 0x0 */
  43         0x30, 0x00, 0x00, 0x60, 0x00, 0x00, /* mov r3=ip */
  44         0x00, 0x00, 0x04, 0x00,             /* nop.i 0x0 */
  45         0x05, 0x00, 0x00, 0x00, 0x01, 0x00, /* [MLX] nop.m 0x0 */
  46         0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* nop.x 0x0;; */
  47         0x00, 0x00, 0x04, 0x00
  48 };
  49
  50 static unsigned char *ftrace_nop_replace(void)
  51 {
  52         return ftrace_nop_code;
  53 }
  54
  55 /*
  56  * mcount stub will be converted below for call
  57  * Note: Just the last instruction is changed against nop
  58  * */
  59 static unsigned char __attribute__((aligned(8)))
  60 ftrace_call_code[MCOUNT_INSN_SIZE] = {
  61         0x00, 0x00, 0x00, 0x00, 0x01, 0x00, /* [MII] nop.m 0x0 */
  62         0x30, 0x00, 0x00, 0x60, 0x00, 0x00, /* mov r3=ip */
  63         0x00, 0x00, 0x04, 0x00,             /* nop.i 0x0 */
  64         0x05, 0x00, 0x00, 0x00, 0x01, 0x00, /* [MLX] nop.m 0x0 */
  65         0xff, 0xff, 0xff, 0xff, 0x7f, 0x00, /* brl.many .;;*/
  66         0xf8, 0xff, 0xff, 0xc8
  67 };
  68
  69 struct ftrace_call_insn {
  70         u64 dummy1, dummy2;
  71         u64 dummy3:48;
  72         u64 imm39_l:16;
  73         u64 imm39_h:23;
  74         u64 dummy4:13;
  75         u64 imm20:20;
  76         u64 dummy5:3;
  77         u64 i:1;
  78         u64 dummy6:4;
  79 };
  80
  81 static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
  82 {
  83         struct ftrace_call_insn *code = (void *)ftrace_call_code;
  84         unsigned long offset = addr - (ip + 0x10);
  85
  86         code->imm39_l = offset >> 24;
  87         code->imm39_h = offset >> 40;
  88         code->imm20 = offset >> 4;
  89         code->i = offset >> 63;
  90         return ftrace_call_code;
  91 }
  92
  93 static int
  94 ftrace_modify_code(unsigned long ip, unsigned char *old_code,
  95                    unsigned char *new_code, int do_check)
  96 {
  97         unsigned char replaced[MCOUNT_INSN_SIZE];
  98
  99         /*
 100          * Note: Due to modules and __init, code can
 101          *  disappear and change, we need to protect against faulting
 102          *  as well as code changing. We do this by using the
 103          *  probe_kernel_* functions.
 104          *
 105          * No real locking needed, this code is run through
 106          * kstop_machine, or before SMP starts.
 107          */
 108
 109         if (!do_check)
 110                 goto skip_check;
 111
 112         /* read the text we want to modify */
 113         if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
 114                 return -EFAULT;
 115
 116         /* Make sure it is what we expect it to be */
 117         if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
 118                 return -EINVAL;
 119
 120 skip_check:
 121         /* replace the text with the new text */
 122         if (probe_kernel_write(((void *)ip), new_code, MCOUNT_INSN_SIZE))
 123                 return -EPERM;
 124         flush_icache_range(ip, ip + MCOUNT_INSN_SIZE);
 125
 126         return 0;
 127 }
 128
 129 static int ftrace_make_nop_check(struct dyn_ftrace *rec, unsigned long addr)
 130 {
 131         unsigned char __attribute__((aligned(8))) replaced[MCOUNT_INSN_SIZE];
 132         unsigned long ip = rec->ip;
 133
 134         if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
 135                 return -EFAULT;
 136         if (rec->flags & FTRACE_FL_CONVERTED) {
 137                 struct ftrace_call_insn *call_insn, *tmp_call;
 138
 139                 call_insn = (void *)ftrace_call_code;
 140                 tmp_call = (void *)replaced;
 141                 call_insn->imm39_l = tmp_call->imm39_l;
 142                 call_insn->imm39_h = tmp_call->imm39_h;
 143                 call_insn->imm20 = tmp_call->imm20;
 144                 call_insn->i = tmp_call->i;
 145                 if (memcmp(replaced, ftrace_call_code, MCOUNT_INSN_SIZE) != 0)
 146                         return -EINVAL;
 147                 return 0;
 148         } else {
 149                 struct ftrace_orig_insn *call_insn, *tmp_call;
 150
 151                 call_insn = (void *)ftrace_orig_code;
 152                 tmp_call = (void *)replaced;
 153                 call_insn->sign = tmp_call->sign;
 154                 call_insn->imm20 = tmp_call->imm20;
 155                 if (memcmp(replaced, ftrace_orig_code, MCOUNT_INSN_SIZE) != 0)
 156                         return -EINVAL;
 157                 return 0;
 158         }
 159 }
 160
 161 int ftrace_make_nop(struct module *mod,
 162                     struct dyn_ftrace *rec, unsigned long addr)
 163 {
 164         int ret;
 165         char *new;
 166
 167         ret = ftrace_make_nop_check(rec, addr);
 168         if (ret)
 169                 return ret;
 170         new = ftrace_nop_replace();
 171         return ftrace_modify_code(rec->ip, NULL, new, 0);
 172 }
 173
 174 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 175 {
 176         unsigned long ip = rec->ip;
 177         unsigned char *old, *new;
 178
 179         old=  ftrace_nop_replace();
 180         new = ftrace_call_replace(ip, addr);
 181         return ftrace_modify_code(ip, old, new, 1);
 182 }
 183
 184 /* in IA64, _mcount can't directly call ftrace_stub. Only jump is ok */
 185 int ftrace_update_ftrace_func(ftrace_func_t func)
 186 {
 187         unsigned long ip;
 188         unsigned long addr = ((struct fnptr *)ftrace_call)->ip;
 189
 190         if (func == ftrace_stub)
 191                 return 0;
 192         ip = ((struct fnptr *)func)->ip;
 193
 194         ia64_patch_imm64(addr + 2, ip);
 195
 196         flush_icache_range(addr, addr + 16);
 197         return 0;
 198 }
 199
 200 /* run from kstop_machine */
 201 int __init ftrace_dyn_arch_init(void *data)
 202 {
 203         *(unsigned long *)data = 0;
 204
 205         return 0;
 206 }