Commit | Line | Data |
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dfd9f7ab HC |
1 | /* |
2 | * Dynamic function tracer architecture backend. | |
3 | * | |
4 | * Copyright IBM Corp. 2009 | |
5 | * | |
6 | * Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>, | |
4cc9bed0 | 7 | * Martin Schwidefsky <schwidefsky@de.ibm.com> |
dfd9f7ab HC |
8 | */ |
9 | ||
88dbd203 | 10 | #include <linux/hardirq.h> |
dfd9f7ab HC |
11 | #include <linux/uaccess.h> |
12 | #include <linux/ftrace.h> | |
13 | #include <linux/kernel.h> | |
14 | #include <linux/types.h> | |
4cc9bed0 | 15 | #include <linux/kprobes.h> |
9bf1226b | 16 | #include <trace/syscall.h> |
cbb870c8 | 17 | #include <asm/asm-offsets.h> |
dfd9f7ab | 18 | |
88dbd203 HC |
19 | #ifdef CONFIG_DYNAMIC_FTRACE |
20 | ||
dfd9f7ab | 21 | void ftrace_disable_code(void); |
4cc9bed0 | 22 | void ftrace_enable_insn(void); |
dfd9f7ab HC |
23 | |
24 | #ifdef CONFIG_64BIT | |
4cc9bed0 MS |
25 | /* |
26 | * The 64-bit mcount code looks like this: | |
27 | * stg %r14,8(%r15) # offset 0 | |
28 | * > larl %r1,<&counter> # offset 6 | |
29 | * > brasl %r14,_mcount # offset 12 | |
30 | * lg %r14,8(%r15) # offset 18 | |
31 | * Total length is 24 bytes. The middle two instructions of the mcount | |
32 | * block get overwritten by ftrace_make_nop / ftrace_make_call. | |
33 | * The 64-bit enabled ftrace code block looks like this: | |
34 | * stg %r14,8(%r15) # offset 0 | |
35 | * > lg %r1,__LC_FTRACE_FUNC # offset 6 | |
36 | * > lgr %r0,%r0 # offset 12 | |
37 | * > basr %r14,%r1 # offset 16 | |
38 | * lg %r14,8(%15) # offset 18 | |
39 | * The return points of the mcount/ftrace function have the same offset 18. | |
40 | * The 64-bit disable ftrace code block looks like this: | |
41 | * stg %r14,8(%r15) # offset 0 | |
42 | * > jg .+18 # offset 6 | |
43 | * > lgr %r0,%r0 # offset 12 | |
44 | * > basr %r14,%r1 # offset 16 | |
45 | * lg %r14,8(%15) # offset 18 | |
46 | * The jg instruction branches to offset 24 to skip as many instructions | |
47 | * as possible. | |
48 | */ | |
dfd9f7ab HC |
49 | asm( |
50 | " .align 4\n" | |
51 | "ftrace_disable_code:\n" | |
4cc9bed0 | 52 | " jg 0f\n" |
dfd9f7ab | 53 | " lgr %r0,%r0\n" |
4cc9bed0 MS |
54 | " basr %r14,%r1\n" |
55 | "0:\n" | |
dfd9f7ab | 56 | " .align 4\n" |
4cc9bed0 MS |
57 | "ftrace_enable_insn:\n" |
58 | " lg %r1,"__stringify(__LC_FTRACE_FUNC)"\n"); | |
dfd9f7ab | 59 | |
4cc9bed0 | 60 | #define FTRACE_INSN_SIZE 6 |
dfd9f7ab HC |
61 | |
62 | #else /* CONFIG_64BIT */ | |
4cc9bed0 MS |
63 | /* |
64 | * The 31-bit mcount code looks like this: | |
65 | * st %r14,4(%r15) # offset 0 | |
66 | * > bras %r1,0f # offset 4 | |
67 | * > .long _mcount # offset 8 | |
68 | * > .long <&counter> # offset 12 | |
69 | * > 0: l %r14,0(%r1) # offset 16 | |
70 | * > l %r1,4(%r1) # offset 20 | |
71 | * basr %r14,%r14 # offset 24 | |
72 | * l %r14,4(%r15) # offset 26 | |
73 | * Total length is 30 bytes. The twenty bytes starting from offset 4 | |
74 | * to offset 24 get overwritten by ftrace_make_nop / ftrace_make_call. | |
75 | * The 31-bit enabled ftrace code block looks like this: | |
76 | * st %r14,4(%r15) # offset 0 | |
77 | * > l %r14,__LC_FTRACE_FUNC # offset 4 | |
78 | * > j 0f # offset 8 | |
79 | * > .fill 12,1,0x07 # offset 12 | |
80 | * 0: basr %r14,%r14 # offset 24 | |
81 | * l %r14,4(%r14) # offset 26 | |
82 | * The return points of the mcount/ftrace function have the same offset 26. | |
83 | * The 31-bit disabled ftrace code block looks like this: | |
84 | * st %r14,4(%r15) # offset 0 | |
85 | * > j .+26 # offset 4 | |
86 | * > j 0f # offset 8 | |
87 | * > .fill 12,1,0x07 # offset 12 | |
88 | * 0: basr %r14,%r14 # offset 24 | |
89 | * l %r14,4(%r14) # offset 26 | |
90 | * The j instruction branches to offset 30 to skip as many instructions | |
91 | * as possible. | |
92 | */ | |
dfd9f7ab HC |
93 | asm( |
94 | " .align 4\n" | |
95 | "ftrace_disable_code:\n" | |
4cc9bed0 | 96 | " j 1f\n" |
dfd9f7ab | 97 | " j 0f\n" |
4cc9bed0 MS |
98 | " .fill 12,1,0x07\n" |
99 | "0: basr %r14,%r14\n" | |
100 | "1:\n" | |
dfd9f7ab | 101 | " .align 4\n" |
4cc9bed0 MS |
102 | "ftrace_enable_insn:\n" |
103 | " l %r14,"__stringify(__LC_FTRACE_FUNC)"\n"); | |
dfd9f7ab | 104 | |
4cc9bed0 | 105 | #define FTRACE_INSN_SIZE 4 |
dfd9f7ab HC |
106 | |
107 | #endif /* CONFIG_64BIT */ | |
108 | ||
dfd9f7ab HC |
109 | |
110 | int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, | |
111 | unsigned long addr) | |
112 | { | |
4cc9bed0 MS |
113 | if (probe_kernel_write((void *) rec->ip, ftrace_disable_code, |
114 | MCOUNT_INSN_SIZE)) | |
115 | return -EPERM; | |
116 | return 0; | |
dfd9f7ab HC |
117 | } |
118 | ||
119 | int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) | |
120 | { | |
4cc9bed0 MS |
121 | if (probe_kernel_write((void *) rec->ip, ftrace_enable_insn, |
122 | FTRACE_INSN_SIZE)) | |
123 | return -EPERM; | |
124 | return 0; | |
dfd9f7ab HC |
125 | } |
126 | ||
127 | int ftrace_update_ftrace_func(ftrace_func_t func) | |
128 | { | |
dfd9f7ab HC |
129 | return 0; |
130 | } | |
131 | ||
132 | int __init ftrace_dyn_arch_init(void *data) | |
133 | { | |
4cc9bed0 | 134 | *(unsigned long *) data = 0; |
dfd9f7ab HC |
135 | return 0; |
136 | } | |
88dbd203 HC |
137 | |
138 | #endif /* CONFIG_DYNAMIC_FTRACE */ | |
139 | ||
140 | #ifdef CONFIG_FUNCTION_GRAPH_TRACER | |
88dbd203 HC |
141 | /* |
142 | * Hook the return address and push it in the stack of return addresses | |
143 | * in current thread info. | |
144 | */ | |
4cc9bed0 MS |
145 | unsigned long __kprobes prepare_ftrace_return(unsigned long parent, |
146 | unsigned long ip) | |
88dbd203 HC |
147 | { |
148 | struct ftrace_graph_ent trace; | |
149 | ||
88dbd203 HC |
150 | if (unlikely(atomic_read(¤t->tracing_graph_pause))) |
151 | goto out; | |
aca91209 | 152 | ip = (ip & PSW_ADDR_INSN) - MCOUNT_INSN_SIZE; |
71e308a2 | 153 | if (ftrace_push_return_trace(parent, ip, &trace.depth, 0) == -EBUSY) |
88dbd203 | 154 | goto out; |
aca91209 | 155 | trace.func = ip; |
88dbd203 HC |
156 | /* Only trace if the calling function expects to. */ |
157 | if (!ftrace_graph_entry(&trace)) { | |
158 | current->curr_ret_stack--; | |
159 | goto out; | |
160 | } | |
4cc9bed0 | 161 | parent = (unsigned long) return_to_handler; |
88dbd203 HC |
162 | out: |
163 | return parent; | |
164 | } | |
4cc9bed0 MS |
165 | |
166 | #ifdef CONFIG_DYNAMIC_FTRACE | |
167 | /* | |
168 | * Patch the kernel code at ftrace_graph_caller location. The instruction | |
169 | * there is branch relative and save to prepare_ftrace_return. To disable | |
170 | * the call to prepare_ftrace_return we patch the bras offset to point | |
171 | * directly after the instructions. To enable the call we calculate | |
172 | * the original offset to prepare_ftrace_return and put it back. | |
173 | */ | |
174 | int ftrace_enable_ftrace_graph_caller(void) | |
175 | { | |
176 | unsigned short offset; | |
177 | ||
178 | offset = ((void *) prepare_ftrace_return - | |
179 | (void *) ftrace_graph_caller) / 2; | |
180 | return probe_kernel_write(ftrace_graph_caller + 2, | |
181 | &offset, sizeof(offset)); | |
182 | } | |
183 | ||
184 | int ftrace_disable_ftrace_graph_caller(void) | |
185 | { | |
186 | static unsigned short offset = 0x0002; | |
187 | ||
188 | return probe_kernel_write(ftrace_graph_caller + 2, | |
189 | &offset, sizeof(offset)); | |
190 | } | |
191 | ||
192 | #endif /* CONFIG_DYNAMIC_FTRACE */ | |
88dbd203 | 193 | #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ |