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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 | } |
207 |
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