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:
 101          * We are paranoid about modifying text, as if a bug was to happen, it
 102          * could cause us to read or write to someplace that could cause harm.
 103          * Carefully read and modify the code with probe_kernel_*(), and make
 104          * sure what we read is what we expected it to be before modifying it.
 105          */
 106
 107         if (!do_check)
 108                 goto skip_check;
 109
 110         /* read the text we want to modify */
 111         if (copy_from_kernel_nofault(replaced, (void *)ip, MCOUNT_INSN_SIZE))
 112                 return -EFAULT;
 113
 114         /* Make sure it is what we expect it to be */
 115         if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
 116                 return -EINVAL;
 117
 118 skip_check:
 119         /* replace the text with the new text */
 120         if (copy_to_kernel_nofault(((void *)ip), new_code, MCOUNT_INSN_SIZE))
 121                 return -EPERM;
 122         flush_icache_range(ip, ip + MCOUNT_INSN_SIZE);
 123
 124         return 0;
 125 }
 126
 127 static int ftrace_make_nop_check(struct dyn_ftrace *rec, unsigned long addr)
 128 {
 129         unsigned char __attribute__((aligned(8))) replaced[MCOUNT_INSN_SIZE];
 130         unsigned long ip = rec->ip;
 131
 132         if (copy_from_kernel_nofault(replaced, (void *)ip, MCOUNT_INSN_SIZE))
 133                 return -EFAULT;
 134         if (rec->flags & FTRACE_FL_CONVERTED) {
 135                 struct ftrace_call_insn *call_insn, *tmp_call;
 136
 137                 call_insn = (void *)ftrace_call_code;
 138                 tmp_call = (void *)replaced;
 139                 call_insn->imm39_l = tmp_call->imm39_l;
 140                 call_insn->imm39_h = tmp_call->imm39_h;
 141                 call_insn->imm20 = tmp_call->imm20;
 142                 call_insn->i = tmp_call->i;
 143                 if (memcmp(replaced, ftrace_call_code, MCOUNT_INSN_SIZE) != 0)
 144                         return -EINVAL;
 145                 return 0;
 146         } else {
 147                 struct ftrace_orig_insn *call_insn, *tmp_call;
 148
 149                 call_insn = (void *)ftrace_orig_code;
 150                 tmp_call = (void *)replaced;
 151                 call_insn->sign = tmp_call->sign;
 152                 call_insn->imm20 = tmp_call->imm20;
 153                 if (memcmp(replaced, ftrace_orig_code, MCOUNT_INSN_SIZE) != 0)
 154                         return -EINVAL;
 155                 return 0;
 156         }
 157 }
 158
 159 int ftrace_make_nop(struct module *mod,
 160                     struct dyn_ftrace *rec, unsigned long addr)
 161 {
 162         int ret;
 163         char *new;
 164
 165         ret = ftrace_make_nop_check(rec, addr);
 166         if (ret)
 167                 return ret;
 168         new = ftrace_nop_replace();
 169         return ftrace_modify_code(rec->ip, NULL, new, 0);
 170 }
 171
 172 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 173 {
 174         unsigned long ip = rec->ip;
 175         unsigned char *old, *new;
 176
 177         old=  ftrace_nop_replace();
 178         new = ftrace_call_replace(ip, addr);
 179         return ftrace_modify_code(ip, old, new, 1);
 180 }
 181
 182 /* in IA64, _mcount can't directly call ftrace_stub. Only jump is ok */
 183 int ftrace_update_ftrace_func(ftrace_func_t func)
 184 {
 185         unsigned long ip;
 186         unsigned long addr = ((struct fnptr *)ftrace_call)->ip;
 187
 188         if (func == ftrace_stub)
 189                 return 0;
 190         ip = ((struct fnptr *)func)->ip;
 191
 192         ia64_patch_imm64(addr + 2, ip);
 193
 194         flush_icache_range(addr, addr + 16);
 195         return 0;
 196 }
 197
 198 /* run from kstop_machine */
 199 int __init ftrace_dyn_arch_init(void)
 200 {
 201         return 0;
 202 }