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1 /*
2 * mcount and friends -- ftrace stuff
3 *
4 * Copyright (C) 2009-2010 Analog Devices Inc.
5 * Licensed under the GPL-2 or later.
6 */
7
8 #include <linux/linkage.h>
9 #include <asm/ftrace.h>
10
11 .text
12
13 #ifdef CONFIG_DYNAMIC_FTRACE
14
15 /* Simple stub so we can boot the kernel until runtime patching has
16 * disabled all calls to this. Then it'll be unused.
17 */
18 ENTRY(__mcount)
19 # if ANOMALY_05000371
20 nop; nop; nop; nop;
21 # endif
22 rts;
23 ENDPROC(__mcount)
24
25 /* GCC will have called us before setting up the function prologue, so we
26 * can clobber the normal scratch registers, but we need to make sure to
27 * save/restore the registers used for argument passing (R0-R2) in case
28 * the profiled function is using them. With data registers, R3 is the
29 * only one we can blow away. With pointer registers, we have P0-P2.
30 *
31 * Upon entry, the RETS will point to the top of the current profiled
32 * function. And since GCC pushed the previous RETS for us, the previous
33 * function will be waiting there. mmmm pie.
34 */
35 ENTRY(_ftrace_caller)
36 /* save first/second/third function arg and the return register */
37 [--sp] = r2;
38 [--sp] = r0;
39 [--sp] = r1;
40 [--sp] = rets;
41
42 /* function_trace_call(unsigned long ip, unsigned long parent_ip):
43 * ip: this point was called by ...
44 * parent_ip: ... this function
45 * the ip itself will need adjusting for the mcount call
46 */
47 r0 = rets;
48 r1 = [sp + 16]; /* skip the 4 local regs on stack */
49 r0 += -MCOUNT_INSN_SIZE;
50
51 .globl _ftrace_call
52 _ftrace_call:
53 call _ftrace_stub
54
55 # ifdef CONFIG_FUNCTION_GRAPH_TRACER
56 .globl _ftrace_graph_call
57 _ftrace_graph_call:
58 nop; /* jump _ftrace_graph_caller; */
59 # endif
60
61 /* restore state and get out of dodge */
62 .Lfinish_trace:
63 rets = [sp++];
64 r1 = [sp++];
65 r0 = [sp++];
66 r2 = [sp++];
67
68 .globl _ftrace_stub
69 _ftrace_stub:
70 rts;
71 ENDPROC(_ftrace_caller)
72
73 #else
74
75 /* See documentation for _ftrace_caller */
76 ENTRY(__mcount)
77 /* save third function arg early so we can do testing below */
78 [--sp] = r2;
79
80 /* load the function pointer to the tracer */
81 p0.l = _ftrace_trace_function;
82 p0.h = _ftrace_trace_function;
83 r3 = [p0];
84
85 /* optional micro optimization: don't call the stub tracer */
86 r2.l = _ftrace_stub;
87 r2.h = _ftrace_stub;
88 cc = r2 == r3;
89 if ! cc jump .Ldo_trace;
90
91 # ifdef CONFIG_FUNCTION_GRAPH_TRACER
92 /* if the ftrace_graph_return function pointer is not set to
93 * the ftrace_stub entry, call prepare_ftrace_return().
94 */
95 p0.l = _ftrace_graph_return;
96 p0.h = _ftrace_graph_return;
97 r3 = [p0];
98 cc = r2 == r3;
99 if ! cc jump _ftrace_graph_caller;
100
101 /* similarly, if the ftrace_graph_entry function pointer is not
102 * set to the ftrace_graph_entry_stub entry, ...
103 */
104 p0.l = _ftrace_graph_entry;
105 p0.h = _ftrace_graph_entry;
106 r2.l = _ftrace_graph_entry_stub;
107 r2.h = _ftrace_graph_entry_stub;
108 r3 = [p0];
109 cc = r2 == r3;
110 if ! cc jump _ftrace_graph_caller;
111 # endif
112
113 r2 = [sp++];
114 rts;
115
116 .Ldo_trace:
117
118 /* save first/second function arg and the return register */
119 [--sp] = r0;
120 [--sp] = r1;
121 [--sp] = rets;
122
123 /* setup the tracer function */
124 p0 = r3;
125
126 /* function_trace_call(unsigned long ip, unsigned long parent_ip):
127 * ip: this point was called by ...
128 * parent_ip: ... this function
129 * the ip itself will need adjusting for the mcount call
130 */
131 r0 = rets;
132 r1 = [sp + 16]; /* skip the 4 local regs on stack */
133 r0 += -MCOUNT_INSN_SIZE;
134
135 /* call the tracer */
136 call (p0);
137
138 /* restore state and get out of dodge */
139 .Lfinish_trace:
140 rets = [sp++];
141 r1 = [sp++];
142 r0 = [sp++];
143 r2 = [sp++];
144
145 .globl _ftrace_stub
146 _ftrace_stub:
147 rts;
148 ENDPROC(__mcount)
149
150 #endif
151
152 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
153 /* The prepare_ftrace_return() function is similar to the trace function
154 * except it takes a pointer to the location of the frompc. This is so
155 * the prepare_ftrace_return() can hijack it temporarily for probing
156 * purposes.
157 */
158 ENTRY(_ftrace_graph_caller)
159 # ifndef CONFIG_DYNAMIC_FTRACE
160 /* save first/second function arg and the return register */
161 [--sp] = r0;
162 [--sp] = r1;
163 [--sp] = rets;
164
165 /* prepare_ftrace_return(parent, self_addr, frame_pointer) */
166 r0 = sp; /* unsigned long *parent */
167 r1 = rets; /* unsigned long self_addr */
168 # else
169 r0 = sp; /* unsigned long *parent */
170 r1 = [sp]; /* unsigned long self_addr */
171 # endif
172 # ifdef CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST
173 r2 = fp; /* unsigned long frame_pointer */
174 # endif
175 r0 += 16; /* skip the 4 local regs on stack */
176 r1 += -MCOUNT_INSN_SIZE;
177 call _prepare_ftrace_return;
178
179 jump .Lfinish_trace;
180 ENDPROC(_ftrace_graph_caller)
181
182 /* Undo the rewrite caused by ftrace_graph_caller(). The common function
183 * ftrace_return_to_handler() will return the original rets so we can
184 * restore it and be on our way.
185 */
186 ENTRY(_return_to_handler)
187 /* make sure original return values are saved */
188 [--sp] = p0;
189 [--sp] = r0;
190 [--sp] = r1;
191
192 /* get original return address */
193 # ifdef CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST
194 r0 = fp; /* Blackfin is sane, so omit this */
195 # endif
196 call _ftrace_return_to_handler;
197 rets = r0;
198
199 /* anomaly 05000371 - make sure we have at least three instructions
200 * between rets setting and the return
201 */
202 r1 = [sp++];
203 r0 = [sp++];
204 p0 = [sp++];
205 rts;
206 ENDPROC(_return_to_handler)
207 #endif