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 (probe_kernel_read(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 (probe_kernel_write(((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 (probe_kernel_read(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 } 203