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538f1952 WZ |
1 | /* |
2 | * Code for replacing ftrace calls with jumps. | |
3 | * | |
4 | * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com> | |
5 | * Copyright (C) 2009 DSLab, Lanzhou University, China | |
6 | * Author: Wu Zhangjin <wuzj@lemote.com> | |
7 | * | |
8 | * Thanks goes to Steven Rostedt for writing the original x86 version. | |
9 | */ | |
10 | ||
11 | #include <linux/uaccess.h> | |
12 | #include <linux/init.h> | |
13 | #include <linux/ftrace.h> | |
14 | ||
15 | #include <asm/cacheflush.h> | |
29c5d346 WZ |
16 | #include <asm/asm.h> |
17 | #include <asm/asm-offsets.h> | |
538f1952 WZ |
18 | |
19 | #ifdef CONFIG_DYNAMIC_FTRACE | |
20 | ||
21 | #define JAL 0x0c000000 /* jump & link: ip --> ra, jump to target */ | |
22 | #define ADDR_MASK 0x03ffffff /* op_code|addr : 31...26|25 ....0 */ | |
23 | #define jump_insn_encode(op_code, addr) \ | |
24 | ((unsigned int)((op_code) | (((addr) >> 2) & ADDR_MASK))) | |
25 | ||
26 | static unsigned int ftrace_nop = 0x00000000; | |
27 | ||
28 | static int ftrace_modify_code(unsigned long ip, unsigned int new_code) | |
29 | { | |
30 | *(unsigned int *)ip = new_code; | |
31 | ||
32 | flush_icache_range(ip, ip + 8); | |
33 | ||
34 | return 0; | |
35 | } | |
36 | ||
37 | static int lui_v1; | |
38 | static int jal_mcount; | |
39 | ||
40 | int ftrace_make_nop(struct module *mod, | |
41 | struct dyn_ftrace *rec, unsigned long addr) | |
42 | { | |
43 | unsigned int new; | |
44 | unsigned long ip = rec->ip; | |
45 | ||
46 | /* We have compiled module with -mlong-calls, but compiled the kernel | |
47 | * without it, we need to cope with them respectively. */ | |
48 | if (ip & 0x40000000) { | |
49 | /* record it for ftrace_make_call */ | |
50 | if (lui_v1 == 0) | |
51 | lui_v1 = *(unsigned int *)ip; | |
52 | ||
53 | /* lui v1, hi_16bit_of_mcount --> b 1f (0x10000004) | |
54 | * addiu v1, v1, low_16bit_of_mcount | |
55 | * move at, ra | |
56 | * jalr v1 | |
57 | * nop | |
58 | * 1f: (ip + 12) | |
59 | */ | |
60 | new = 0x10000004; | |
61 | } else { | |
62 | /* record/calculate it for ftrace_make_call */ | |
63 | if (jal_mcount == 0) { | |
64 | /* We can record it directly like this: | |
65 | * jal_mcount = *(unsigned int *)ip; | |
66 | * Herein, jump over the first two nop instructions */ | |
67 | jal_mcount = jump_insn_encode(JAL, (MCOUNT_ADDR + 8)); | |
68 | } | |
69 | ||
70 | /* move at, ra | |
71 | * jalr v1 --> nop | |
72 | */ | |
73 | new = ftrace_nop; | |
74 | } | |
75 | return ftrace_modify_code(ip, new); | |
76 | } | |
77 | ||
78 | static int modified; /* initialized as 0 by default */ | |
79 | ||
80 | int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) | |
81 | { | |
82 | unsigned int new; | |
83 | unsigned long ip = rec->ip; | |
84 | ||
85 | /* We just need to remove the "b ftrace_stub" at the fist time! */ | |
86 | if (modified == 0) { | |
87 | modified = 1; | |
88 | ftrace_modify_code(addr, ftrace_nop); | |
89 | } | |
90 | /* ip, module: 0xc0000000, kernel: 0x80000000 */ | |
91 | new = (ip & 0x40000000) ? lui_v1 : jal_mcount; | |
92 | ||
93 | return ftrace_modify_code(ip, new); | |
94 | } | |
95 | ||
96 | #define FTRACE_CALL_IP ((unsigned long)(&ftrace_call)) | |
97 | ||
98 | int ftrace_update_ftrace_func(ftrace_func_t func) | |
99 | { | |
100 | unsigned int new; | |
101 | ||
102 | new = jump_insn_encode(JAL, (unsigned long)func); | |
103 | ||
104 | return ftrace_modify_code(FTRACE_CALL_IP, new); | |
105 | } | |
106 | ||
107 | int __init ftrace_dyn_arch_init(void *data) | |
108 | { | |
109 | /* The return code is retured via data */ | |
110 | *(unsigned long *)data = 0; | |
111 | ||
112 | return 0; | |
113 | } | |
114 | #endif /* CONFIG_DYNAMIC_FTRACE */ | |
29c5d346 WZ |
115 | |
116 | #ifdef CONFIG_FUNCTION_GRAPH_TRACER | |
117 | ||
118 | #define S_RA_SP (0xafbf << 16) /* s{d,w} ra, offset(sp) */ | |
119 | #define S_R_SP (0xafb0 << 16) /* s{d,w} R, offset(sp) */ | |
120 | #define OFFSET_MASK 0xffff /* stack offset range: 0 ~ PT_SIZE */ | |
121 | ||
122 | unsigned long ftrace_get_parent_addr(unsigned long self_addr, | |
123 | unsigned long parent, | |
124 | unsigned long parent_addr, | |
125 | unsigned long fp) | |
126 | { | |
127 | unsigned long sp, ip, ra; | |
128 | unsigned int code; | |
129 | ||
130 | /* in module or kernel? */ | |
131 | if (self_addr & 0x40000000) { | |
132 | /* module: move to the instruction "lui v1, HI_16BIT_OF_MCOUNT" */ | |
133 | ip = self_addr - 20; | |
134 | } else { | |
135 | /* kernel: move to the instruction "move ra, at" */ | |
136 | ip = self_addr - 12; | |
137 | } | |
138 | ||
139 | /* search the text until finding the non-store instruction or "s{d,w} | |
140 | * ra, offset(sp)" instruction */ | |
141 | do { | |
142 | ip -= 4; | |
143 | ||
144 | /* get the code at "ip" */ | |
145 | code = *(unsigned int *)ip; | |
146 | ||
147 | /* If we hit the non-store instruction before finding where the | |
148 | * ra is stored, then this is a leaf function and it does not | |
149 | * store the ra on the stack. */ | |
150 | if ((code & S_R_SP) != S_R_SP) | |
151 | return parent_addr; | |
152 | ||
153 | } while (((code & S_RA_SP) != S_RA_SP)); | |
154 | ||
155 | sp = fp + (code & OFFSET_MASK); | |
156 | ra = *(unsigned long *)sp; | |
157 | ||
158 | if (ra == parent) | |
159 | return sp; | |
160 | ||
161 | return 0; | |
162 | } | |
163 | ||
164 | /* | |
165 | * Hook the return address and push it in the stack of return addrs | |
166 | * in current thread info. | |
167 | */ | |
168 | void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, | |
169 | unsigned long fp) | |
170 | { | |
171 | unsigned long old; | |
172 | struct ftrace_graph_ent trace; | |
173 | unsigned long return_hooker = (unsigned long) | |
174 | &return_to_handler; | |
175 | ||
176 | if (unlikely(atomic_read(¤t->tracing_graph_pause))) | |
177 | return; | |
178 | ||
179 | /* "parent" is the stack address saved the return address of the caller | |
180 | * of _mcount, for a leaf function not save the return address in the | |
181 | * stack address, so, we "emulate" one in _mcount's stack space, and | |
182 | * hijack it directly, but for a non-leaf function, it will save the | |
183 | * return address to the its stack space, so, we can not hijack the | |
184 | * "parent" directly, but need to find the real stack address, | |
185 | * ftrace_get_parent_addr() does it! | |
186 | */ | |
187 | ||
188 | old = *parent; | |
189 | ||
190 | parent = (unsigned long *)ftrace_get_parent_addr(self_addr, old, | |
191 | (unsigned long)parent, | |
192 | fp); | |
193 | ||
194 | /* If fails when getting the stack address of the non-leaf function's | |
195 | * ra, stop function graph tracer and return */ | |
196 | if (parent == 0) { | |
197 | ftrace_graph_stop(); | |
198 | WARN_ON(1); | |
199 | return; | |
200 | } | |
201 | ||
202 | *parent = return_hooker; | |
203 | ||
204 | if (ftrace_push_return_trace(old, self_addr, &trace.depth, fp) == | |
205 | -EBUSY) { | |
206 | *parent = old; | |
207 | return; | |
208 | } | |
209 | ||
210 | trace.func = self_addr; | |
211 | ||
212 | /* Only trace if the calling function expects to */ | |
213 | if (!ftrace_graph_entry(&trace)) { | |
214 | current->curr_ret_stack--; | |
215 | *parent = old; | |
216 | } | |
217 | } | |
218 | #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ |