| 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 | } |