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a14a07b8 SL |
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 | /* | |
cbbe12c4 LB |
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. | |
a14a07b8 SL |
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 */ | |
3a36cb11 | 199 | int __init ftrace_dyn_arch_init(void) |
a14a07b8 | 200 | { |
a14a07b8 SL |
201 | return 0; |
202 | } |