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 | |
4cc9bed0 MS |
19 | #ifdef CONFIG_64BIT |
20 | #define MCOUNT_OFFSET_RET 12 | |
21 | #else | |
22 | #define MCOUNT_OFFSET_RET 22 | |
23 | #endif | |
24 | ||
88dbd203 HC |
25 | #ifdef CONFIG_DYNAMIC_FTRACE |
26 | ||
dfd9f7ab | 27 | void ftrace_disable_code(void); |
4cc9bed0 | 28 | void ftrace_enable_insn(void); |
dfd9f7ab HC |
29 | |
30 | #ifdef CONFIG_64BIT | |
4cc9bed0 MS |
31 | /* |
32 | * The 64-bit mcount code looks like this: | |
33 | * stg %r14,8(%r15) # offset 0 | |
34 | * > larl %r1,<&counter> # offset 6 | |
35 | * > brasl %r14,_mcount # offset 12 | |
36 | * lg %r14,8(%r15) # offset 18 | |
37 | * Total length is 24 bytes. The middle two instructions of the mcount | |
38 | * block get overwritten by ftrace_make_nop / ftrace_make_call. | |
39 | * The 64-bit enabled ftrace code block looks like this: | |
40 | * stg %r14,8(%r15) # offset 0 | |
41 | * > lg %r1,__LC_FTRACE_FUNC # offset 6 | |
42 | * > lgr %r0,%r0 # offset 12 | |
43 | * > basr %r14,%r1 # offset 16 | |
44 | * lg %r14,8(%15) # offset 18 | |
45 | * The return points of the mcount/ftrace function have the same offset 18. | |
46 | * The 64-bit disable ftrace code block looks like this: | |
47 | * stg %r14,8(%r15) # offset 0 | |
48 | * > jg .+18 # offset 6 | |
49 | * > lgr %r0,%r0 # offset 12 | |
50 | * > basr %r14,%r1 # offset 16 | |
51 | * lg %r14,8(%15) # offset 18 | |
52 | * The jg instruction branches to offset 24 to skip as many instructions | |
53 | * as possible. | |
54 | */ | |
dfd9f7ab HC |
55 | asm( |
56 | " .align 4\n" | |
57 | "ftrace_disable_code:\n" | |
4cc9bed0 | 58 | " jg 0f\n" |
dfd9f7ab | 59 | " lgr %r0,%r0\n" |
4cc9bed0 MS |
60 | " basr %r14,%r1\n" |
61 | "0:\n" | |
dfd9f7ab | 62 | " .align 4\n" |
4cc9bed0 MS |
63 | "ftrace_enable_insn:\n" |
64 | " lg %r1,"__stringify(__LC_FTRACE_FUNC)"\n"); | |
dfd9f7ab | 65 | |
4cc9bed0 | 66 | #define FTRACE_INSN_SIZE 6 |
dfd9f7ab HC |
67 | |
68 | #else /* CONFIG_64BIT */ | |
4cc9bed0 MS |
69 | /* |
70 | * The 31-bit mcount code looks like this: | |
71 | * st %r14,4(%r15) # offset 0 | |
72 | * > bras %r1,0f # offset 4 | |
73 | * > .long _mcount # offset 8 | |
74 | * > .long <&counter> # offset 12 | |
75 | * > 0: l %r14,0(%r1) # offset 16 | |
76 | * > l %r1,4(%r1) # offset 20 | |
77 | * basr %r14,%r14 # offset 24 | |
78 | * l %r14,4(%r15) # offset 26 | |
79 | * Total length is 30 bytes. The twenty bytes starting from offset 4 | |
80 | * to offset 24 get overwritten by ftrace_make_nop / ftrace_make_call. | |
81 | * The 31-bit enabled ftrace code block looks like this: | |
82 | * st %r14,4(%r15) # offset 0 | |
83 | * > l %r14,__LC_FTRACE_FUNC # offset 4 | |
84 | * > j 0f # offset 8 | |
85 | * > .fill 12,1,0x07 # offset 12 | |
86 | * 0: basr %r14,%r14 # offset 24 | |
87 | * l %r14,4(%r14) # offset 26 | |
88 | * The return points of the mcount/ftrace function have the same offset 26. | |
89 | * The 31-bit disabled ftrace code block looks like this: | |
90 | * st %r14,4(%r15) # offset 0 | |
91 | * > j .+26 # offset 4 | |
92 | * > j 0f # offset 8 | |
93 | * > .fill 12,1,0x07 # offset 12 | |
94 | * 0: basr %r14,%r14 # offset 24 | |
95 | * l %r14,4(%r14) # offset 26 | |
96 | * The j instruction branches to offset 30 to skip as many instructions | |
97 | * as possible. | |
98 | */ | |
dfd9f7ab HC |
99 | asm( |
100 | " .align 4\n" | |
101 | "ftrace_disable_code:\n" | |
4cc9bed0 | 102 | " j 1f\n" |
dfd9f7ab | 103 | " j 0f\n" |
4cc9bed0 MS |
104 | " .fill 12,1,0x07\n" |
105 | "0: basr %r14,%r14\n" | |
106 | "1:\n" | |
dfd9f7ab | 107 | " .align 4\n" |
4cc9bed0 MS |
108 | "ftrace_enable_insn:\n" |
109 | " l %r14,"__stringify(__LC_FTRACE_FUNC)"\n"); | |
dfd9f7ab | 110 | |
4cc9bed0 | 111 | #define FTRACE_INSN_SIZE 4 |
dfd9f7ab HC |
112 | |
113 | #endif /* CONFIG_64BIT */ | |
114 | ||
dfd9f7ab HC |
115 | |
116 | int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, | |
117 | unsigned long addr) | |
118 | { | |
4cc9bed0 MS |
119 | if (probe_kernel_write((void *) rec->ip, ftrace_disable_code, |
120 | MCOUNT_INSN_SIZE)) | |
121 | return -EPERM; | |
122 | return 0; | |
dfd9f7ab HC |
123 | } |
124 | ||
125 | int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) | |
126 | { | |
4cc9bed0 MS |
127 | if (probe_kernel_write((void *) rec->ip, ftrace_enable_insn, |
128 | FTRACE_INSN_SIZE)) | |
129 | return -EPERM; | |
130 | return 0; | |
dfd9f7ab HC |
131 | } |
132 | ||
133 | int ftrace_update_ftrace_func(ftrace_func_t func) | |
134 | { | |
dfd9f7ab HC |
135 | return 0; |
136 | } | |
137 | ||
138 | int __init ftrace_dyn_arch_init(void *data) | |
139 | { | |
4cc9bed0 | 140 | *(unsigned long *) data = 0; |
dfd9f7ab HC |
141 | return 0; |
142 | } | |
88dbd203 HC |
143 | |
144 | #endif /* CONFIG_DYNAMIC_FTRACE */ | |
145 | ||
146 | #ifdef CONFIG_FUNCTION_GRAPH_TRACER | |
88dbd203 HC |
147 | /* |
148 | * Hook the return address and push it in the stack of return addresses | |
149 | * in current thread info. | |
150 | */ | |
4cc9bed0 MS |
151 | unsigned long __kprobes prepare_ftrace_return(unsigned long parent, |
152 | unsigned long ip) | |
88dbd203 HC |
153 | { |
154 | struct ftrace_graph_ent trace; | |
155 | ||
88dbd203 HC |
156 | if (unlikely(atomic_read(¤t->tracing_graph_pause))) |
157 | goto out; | |
71e308a2 | 158 | if (ftrace_push_return_trace(parent, ip, &trace.depth, 0) == -EBUSY) |
88dbd203 | 159 | goto out; |
4cc9bed0 | 160 | trace.func = (ip & PSW_ADDR_INSN) - MCOUNT_OFFSET_RET; |
88dbd203 HC |
161 | /* Only trace if the calling function expects to. */ |
162 | if (!ftrace_graph_entry(&trace)) { | |
163 | current->curr_ret_stack--; | |
164 | goto out; | |
165 | } | |
4cc9bed0 | 166 | parent = (unsigned long) return_to_handler; |
88dbd203 HC |
167 | out: |
168 | return parent; | |
169 | } | |
4cc9bed0 MS |
170 | |
171 | #ifdef CONFIG_DYNAMIC_FTRACE | |
172 | /* | |
173 | * Patch the kernel code at ftrace_graph_caller location. The instruction | |
174 | * there is branch relative and save to prepare_ftrace_return. To disable | |
175 | * the call to prepare_ftrace_return we patch the bras offset to point | |
176 | * directly after the instructions. To enable the call we calculate | |
177 | * the original offset to prepare_ftrace_return and put it back. | |
178 | */ | |
179 | int ftrace_enable_ftrace_graph_caller(void) | |
180 | { | |
181 | unsigned short offset; | |
182 | ||
183 | offset = ((void *) prepare_ftrace_return - | |
184 | (void *) ftrace_graph_caller) / 2; | |
185 | return probe_kernel_write(ftrace_graph_caller + 2, | |
186 | &offset, sizeof(offset)); | |
187 | } | |
188 | ||
189 | int ftrace_disable_ftrace_graph_caller(void) | |
190 | { | |
191 | static unsigned short offset = 0x0002; | |
192 | ||
193 | return probe_kernel_write(ftrace_graph_caller + 2, | |
194 | &offset, sizeof(offset)); | |
195 | } | |
196 | ||
197 | #endif /* CONFIG_DYNAMIC_FTRACE */ | |
88dbd203 | 198 | #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ |