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backtrace.h
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1 /*
2  * Copyright 2010 Tilera Corporation. All Rights Reserved.
3  *
4  * This program is free software; you can redistribute it and/or
5  * modify it under the terms of the GNU General Public License
6  * as published by the Free Software Foundation, version 2.
7  *
8  * This program is distributed in the hope that it will be useful, but
9  * WITHOUT ANY WARRANTY; without even the implied warranty of
10  * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
11  * NON INFRINGEMENT. See the GNU General Public License for
12  * more details.
13  */
14 
15 #ifndef _ASM_TILE_BACKTRACE_H
16 #define _ASM_TILE_BACKTRACE_H
17 
18 #include <linux/types.h>
19 
20 /* Reads 'size' bytes from 'address' and writes the data to 'result'.
21  * Returns true if successful, else false (e.g. memory not readable).
22  */
23 typedef bool (*BacktraceMemoryReader)(void *result,
24  unsigned long address,
25  unsigned int size,
26  void *extra);
27 
28 typedef struct {
29  /* Current PC. */
30  unsigned long pc;
31 
32  /* Current stack pointer value. */
33  unsigned long sp;
34 
35  /* Current frame pointer value (i.e. caller's stack pointer) */
36  unsigned long fp;
37 
38  /* Internal use only: caller's PC for first frame. */
39  unsigned long initial_frame_caller_pc;
40 
41  /* Internal use only: callback to read memory. */
42  BacktraceMemoryReader read_memory_func;
43 
44  /* Internal use only: arbitrary argument to read_memory_func. */
45  void *read_memory_func_extra;
46 
47 } BacktraceIterator;
48 
49 
50 typedef enum {
51 
52  /* We have no idea what the caller's pc is. */
53  PC_LOC_UNKNOWN,
54 
55  /* The caller's pc is currently in lr. */
56  PC_LOC_IN_LR,
57 
58  /* The caller's pc can be found by dereferencing the caller's sp. */
59  PC_LOC_ON_STACK
60 
61 } CallerPCLocation;
62 
63 
64 typedef enum {
65 
66  /* We have no idea what the caller's sp is. */
67  SP_LOC_UNKNOWN,
68 
69  /* The caller's sp is currently in r52. */
70  SP_LOC_IN_R52,
71 
72  /* The caller's sp can be found by adding a certain constant
73  * to the current value of sp.
74  */
75  SP_LOC_OFFSET
76 
77 } CallerSPLocation;
78 
79 
80 /* Bit values ORed into CALLER_* values for info ops. */
81 enum {
82  /* Setting the low bit on any of these values means the info op
83  * applies only to one bundle ago.
84  */
85  ONE_BUNDLE_AGO_FLAG = 1,
86 
87  /* Setting this bit on a CALLER_SP_* value means the PC is in LR.
88  * If not set, PC is on the stack.
89  */
90  PC_IN_LR_FLAG = 2,
91 
92  /* This many of the low bits of a CALLER_SP_* value are for the
93  * flag bits above.
94  */
95  NUM_INFO_OP_FLAGS = 2,
96 
97  /* We cannot have one in the memory pipe so this is the maximum. */
98  MAX_INFO_OPS_PER_BUNDLE = 2
99 };
100 
101 
102 /* Internal constants used to define 'info' operands. */
103 enum {
104  /* 0 and 1 are reserved, as are all negative numbers. */
105 
106  CALLER_UNKNOWN_BASE = 2,
107 
108  CALLER_SP_IN_R52_BASE = 4,
109 
110  CALLER_SP_OFFSET_BASE = 8,
111 };
112 
113 
114 /* Current backtracer state describing where it thinks the caller is. */
115 typedef struct {
116  /*
117  * Public fields
118  */
119 
120  /* How do we find the caller's PC? */
121  CallerPCLocation pc_location : 8;
122 
123  /* How do we find the caller's SP? */
124  CallerSPLocation sp_location : 8;
125 
126  /* If sp_location == SP_LOC_OFFSET, then caller_sp == sp +
127  * loc->sp_offset. Else this field is undefined.
128  */
129  uint16_t sp_offset;
130 
131  /* In the most recently visited bundle a terminating bundle? */
132  bool at_terminating_bundle;
133 
134  /*
135  * Private fields
136  */
137 
138  /* Will the forward scanner see someone clobbering sp
139  * (i.e. changing it with something other than addi sp, sp, N?)
140  */
141  bool sp_clobber_follows;
142 
143  /* Operand to next "visible" info op (no more than one bundle past
144  * the next terminating bundle), or -32768 if none.
145  */
146  int16_t next_info_operand;
147 
148  /* Is the info of in next_info_op in the very next bundle? */
149  bool is_next_info_operand_adjacent;
150 
151 } CallerLocation;
152 
153 extern void backtrace_init(BacktraceIterator *state,
154  BacktraceMemoryReader read_memory_func,
155  void *read_memory_func_extra,
156  unsigned long pc, unsigned long lr,
157  unsigned long sp, unsigned long r52);
158 
159 
160 extern bool backtrace_next(BacktraceIterator *state);
161 
162 #endif /* _ASM_TILE_BACKTRACE_H */
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