Commit | Line | Data |
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dfd9f7ab HC |
1 | /* |
2 | * Dynamic function tracer architecture backend. | |
3 | * | |
3d1e220d | 4 | * Copyright IBM Corp. 2009,2014 |
dfd9f7ab HC |
5 | * |
6 | * Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>, | |
4cc9bed0 | 7 | * Martin Schwidefsky <schwidefsky@de.ibm.com> |
dfd9f7ab HC |
8 | */ |
9 | ||
c933146a | 10 | #include <linux/moduleloader.h> |
88dbd203 | 11 | #include <linux/hardirq.h> |
dfd9f7ab HC |
12 | #include <linux/uaccess.h> |
13 | #include <linux/ftrace.h> | |
14 | #include <linux/kernel.h> | |
15 | #include <linux/types.h> | |
4cc9bed0 | 16 | #include <linux/kprobes.h> |
9bf1226b | 17 | #include <trace/syscall.h> |
cbb870c8 | 18 | #include <asm/asm-offsets.h> |
c933146a | 19 | #include <asm/cacheflush.h> |
63df41d6 | 20 | #include "entry.h" |
dfd9f7ab | 21 | |
4cc9bed0 | 22 | /* |
53255c9a | 23 | * The mcount code looks like this: |
4cc9bed0 | 24 | * stg %r14,8(%r15) # offset 0 |
3d1e220d HC |
25 | * larl %r1,<&counter> # offset 6 |
26 | * brasl %r14,_mcount # offset 12 | |
4cc9bed0 | 27 | * lg %r14,8(%r15) # offset 18 |
c933146a HC |
28 | * Total length is 24 bytes. Only the first instruction will be patched |
29 | * by ftrace_make_call / ftrace_make_nop. | |
53255c9a | 30 | * The enabled ftrace code block looks like this: |
c933146a HC |
31 | * > brasl %r0,ftrace_caller # offset 0 |
32 | * larl %r1,<&counter> # offset 6 | |
33 | * brasl %r14,_mcount # offset 12 | |
34 | * lg %r14,8(%r15) # offset 18 | |
3d1e220d HC |
35 | * The ftrace function gets called with a non-standard C function call ABI |
36 | * where r0 contains the return address. It is also expected that the called | |
37 | * function only clobbers r0 and r1, but restores r2-r15. | |
c933146a HC |
38 | * For module code we can't directly jump to ftrace caller, but need a |
39 | * trampoline (ftrace_plt), which clobbers also r1. | |
3d1e220d HC |
40 | * The return point of the ftrace function has offset 24, so execution |
41 | * continues behind the mcount block. | |
c933146a HC |
42 | * The disabled ftrace code block looks like this: |
43 | * > jg .+24 # offset 0 | |
44 | * larl %r1,<&counter> # offset 6 | |
45 | * brasl %r14,_mcount # offset 12 | |
46 | * lg %r14,8(%r15) # offset 18 | |
4cc9bed0 MS |
47 | * The jg instruction branches to offset 24 to skip as many instructions |
48 | * as possible. | |
49 | */ | |
dfd9f7ab | 50 | |
c933146a | 51 | unsigned long ftrace_plt; |
dfd9f7ab | 52 | |
10dec7db HC |
53 | int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, |
54 | unsigned long addr) | |
55 | { | |
56 | return 0; | |
57 | } | |
dfd9f7ab HC |
58 | |
59 | int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, | |
60 | unsigned long addr) | |
61 | { | |
c933146a HC |
62 | struct ftrace_insn insn; |
63 | unsigned short op; | |
64 | void *from, *to; | |
65 | size_t size; | |
66 | ||
67 | ftrace_generate_nop_insn(&insn); | |
68 | size = sizeof(insn); | |
69 | from = &insn; | |
70 | to = (void *) rec->ip; | |
71 | if (probe_kernel_read(&op, (void *) rec->ip, sizeof(op))) | |
72 | return -EFAULT; | |
73 | /* | |
74 | * If we find a breakpoint instruction, a kprobe has been placed | |
75 | * at the beginning of the function. We write the constant | |
76 | * KPROBE_ON_FTRACE_NOP into the remaining four bytes of the original | |
77 | * instruction so that the kprobes handler can execute a nop, if it | |
78 | * reaches this breakpoint. | |
79 | */ | |
80 | if (op == BREAKPOINT_INSTRUCTION) { | |
81 | size -= 2; | |
82 | from += 2; | |
83 | to += 2; | |
84 | insn.disp = KPROBE_ON_FTRACE_NOP; | |
3d1e220d | 85 | } |
c933146a | 86 | if (probe_kernel_write(to, from, size)) |
4cc9bed0 MS |
87 | return -EPERM; |
88 | return 0; | |
dfd9f7ab HC |
89 | } |
90 | ||
91 | int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) | |
92 | { | |
c933146a HC |
93 | struct ftrace_insn insn; |
94 | unsigned short op; | |
95 | void *from, *to; | |
96 | size_t size; | |
97 | ||
98 | ftrace_generate_call_insn(&insn, rec->ip); | |
99 | size = sizeof(insn); | |
100 | from = &insn; | |
101 | to = (void *) rec->ip; | |
102 | if (probe_kernel_read(&op, (void *) rec->ip, sizeof(op))) | |
103 | return -EFAULT; | |
104 | /* | |
105 | * If we find a breakpoint instruction, a kprobe has been placed | |
106 | * at the beginning of the function. We write the constant | |
107 | * KPROBE_ON_FTRACE_CALL into the remaining four bytes of the original | |
108 | * instruction so that the kprobes handler can execute a brasl if it | |
109 | * reaches this breakpoint. | |
110 | */ | |
111 | if (op == BREAKPOINT_INSTRUCTION) { | |
112 | size -= 2; | |
113 | from += 2; | |
114 | to += 2; | |
115 | insn.disp = KPROBE_ON_FTRACE_CALL; | |
116 | } | |
117 | if (probe_kernel_write(to, from, size)) | |
4cc9bed0 MS |
118 | return -EPERM; |
119 | return 0; | |
dfd9f7ab HC |
120 | } |
121 | ||
122 | int ftrace_update_ftrace_func(ftrace_func_t func) | |
123 | { | |
dfd9f7ab HC |
124 | return 0; |
125 | } | |
126 | ||
3a36cb11 | 127 | int __init ftrace_dyn_arch_init(void) |
dfd9f7ab | 128 | { |
dfd9f7ab HC |
129 | return 0; |
130 | } | |
88dbd203 | 131 | |
c933146a HC |
132 | static int __init ftrace_plt_init(void) |
133 | { | |
134 | unsigned int *ip; | |
135 | ||
136 | ftrace_plt = (unsigned long) module_alloc(PAGE_SIZE); | |
137 | if (!ftrace_plt) | |
138 | panic("cannot allocate ftrace plt\n"); | |
139 | ip = (unsigned int *) ftrace_plt; | |
140 | ip[0] = 0x0d10e310; /* basr 1,0; lg 1,10(1); br 1 */ | |
141 | ip[1] = 0x100a0004; | |
142 | ip[2] = 0x07f10000; | |
143 | ip[3] = FTRACE_ADDR >> 32; | |
144 | ip[4] = FTRACE_ADDR & 0xffffffff; | |
145 | set_memory_ro(ftrace_plt, 1); | |
146 | return 0; | |
147 | } | |
148 | device_initcall(ftrace_plt_init); | |
149 | ||
88dbd203 | 150 | #ifdef CONFIG_FUNCTION_GRAPH_TRACER |
88dbd203 HC |
151 | /* |
152 | * Hook the return address and push it in the stack of return addresses | |
153 | * in current thread info. | |
154 | */ | |
7a5388de | 155 | unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip) |
88dbd203 HC |
156 | { |
157 | struct ftrace_graph_ent trace; | |
158 | ||
88dbd203 HC |
159 | if (unlikely(atomic_read(¤t->tracing_graph_pause))) |
160 | goto out; | |
aca91209 | 161 | ip = (ip & PSW_ADDR_INSN) - MCOUNT_INSN_SIZE; |
aca91209 | 162 | trace.func = ip; |
05e0baaf | 163 | trace.depth = current->curr_ret_stack + 1; |
88dbd203 | 164 | /* Only trace if the calling function expects to. */ |
05e0baaf HC |
165 | if (!ftrace_graph_entry(&trace)) |
166 | goto out; | |
167 | if (ftrace_push_return_trace(parent, ip, &trace.depth, 0) == -EBUSY) | |
88dbd203 | 168 | goto out; |
4cc9bed0 | 169 | parent = (unsigned long) return_to_handler; |
88dbd203 HC |
170 | out: |
171 | return parent; | |
172 | } | |
7a5388de | 173 | NOKPROBE_SYMBOL(prepare_ftrace_return); |
4cc9bed0 | 174 | |
4cc9bed0 MS |
175 | /* |
176 | * Patch the kernel code at ftrace_graph_caller location. The instruction | |
0cccdda8 HC |
177 | * there is branch relative on condition. To enable the ftrace graph code |
178 | * block, we simply patch the mask field of the instruction to zero and | |
179 | * turn the instruction into a nop. | |
180 | * To disable the ftrace graph code the mask field will be patched to | |
181 | * all ones, which turns the instruction into an unconditional branch. | |
4cc9bed0 | 182 | */ |
2481a87b HC |
183 | int ftrace_enable_ftrace_graph_caller(void) |
184 | { | |
0cccdda8 | 185 | u8 op = 0x04; /* set mask field to zero */ |
2481a87b | 186 | |
0cccdda8 | 187 | return probe_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op)); |
2481a87b HC |
188 | } |
189 | ||
190 | int ftrace_disable_ftrace_graph_caller(void) | |
191 | { | |
0cccdda8 | 192 | u8 op = 0xf4; /* set mask field to all ones */ |
2481a87b | 193 | |
0cccdda8 | 194 | return probe_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op)); |
2481a87b HC |
195 | } |
196 | ||
88dbd203 | 197 | #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ |