1 // Copyright 2009 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
4
5 // Stack scanning code for the garbage collector.
6
7 #include "runtime.h"
8
9 #ifdef USING_SPLIT_STACK
10
11 extern void * __splitstack_find (void *, void *, size_t *, void **, void **,
12 void **);
13
14 extern void * __splitstack_find_context (void *context[10], size_t *, void **,
15 void **, void **);
16
17 #endif
18
19 bool runtime_usestackmaps;
20
21 // Calling unwind_init in doscanstack only works if it does not do a
22 // tail call to doscanstack1.
23 #pragma GCC optimize ("-fno-optimize-sibling-calls")
24
25 extern void scanstackblock(uintptr addr, uintptr size, void *gcw)
26 __asm__(GOSYM_PREFIX "runtime.scanstackblock");
27
28 static bool doscanstack1(G*, void*)
29 __attribute__ ((noinline));
30
31 // Scan gp's stack, passing stack chunks to scanstackblock.
32 bool doscanstack(G *gp, void* gcw) {
33 // Save registers on the stack, so that if we are scanning our
34 // own stack we will see them.
35 if (!runtime_usestackmaps) {
36 __builtin_unwind_init();
37 flush_registers_to_secondary_stack();
38 }
39
40 return doscanstack1(gp, gcw);
41 }
42
43 // Scan gp's stack after saving registers.
44 static bool doscanstack1(G *gp, void *gcw) {
45 #ifdef USING_SPLIT_STACK
46 void* sp;
47 size_t spsize;
48 void* next_segment;
49 void* next_sp;
50 void* initial_sp;
51 G* _g_;
52
53 _g_ = runtime_g();
54 if (runtime_usestackmaps) {
55 // If stack map is enabled, we get here only when we can unwind
56 // the stack being scanned. That is, either we are scanning our
57 // own stack, or we are scanning through a signal handler.
58 __go_assert((_g_ == gp) || ((_g_ == gp->m->gsignal) && (gp == gp->m->curg)));
59 return scanstackwithmap(gcw);
60 }
61 if (_g_ == gp) {
62 // Scanning our own stack.
63 // If we are on a signal stack, it can unwind through the signal
64 // handler and see the g stack, so just scan our own stack.
65 sp = __splitstack_find(nil, nil, &spsize, &next_segment,
66 &next_sp, &initial_sp);
67 } else {
68 // Scanning another goroutine's stack.
69 // The goroutine is usually asleep (the world is stopped).
70
71 // The exception is that if the goroutine is about to enter or might
72 // have just exited a system call, it may be executing code such
73 // as schedlock and may have needed to start a new stack segment.
74 // Use the stack segment and stack pointer at the time of
75 // the system call instead, since that won't change underfoot.
76 if(gp->gcstack != 0) {
77 sp = (void*)(gp->gcstack);
78 spsize = gp->gcstacksize;
79 next_segment = (void*)(gp->gcnextsegment);
80 next_sp = (void*)(gp->gcnextsp);
81 initial_sp = (void*)(gp->gcinitialsp);
82 } else {
83 sp = __splitstack_find_context((void**)(&gp->stackcontext[0]),
84 &spsize, &next_segment,
85 &next_sp, &initial_sp);
86 }
87 }
88 if(sp != nil) {
89 scanstackblock((uintptr)(sp), (uintptr)(spsize), gcw);
90 while((sp = __splitstack_find(next_segment, next_sp,
91 &spsize, &next_segment,
92 &next_sp, &initial_sp)) != nil)
93 scanstackblock((uintptr)(sp), (uintptr)(spsize), gcw);
94 }
95 #else
96 byte* bottom;
97 byte* top;
98 byte* nextsp2;
99 byte* initialsp2;
100
101 if(gp == runtime_g()) {
102 // Scanning our own stack.
103 bottom = (byte*)&gp;
104 nextsp2 = secondary_stack_pointer();
105 } else {
106 // Scanning another goroutine's stack.
107 // The goroutine is usually asleep (the world is stopped).
108 bottom = (void*)gp->gcnextsp;
109 if(bottom == nil)
110 return true;
111 nextsp2 = (void*)gp->gcnextsp2;
112 }
113 top = (byte*)(void*)(gp->gcinitialsp) + gp->gcstacksize;
114 if(top > bottom)
115 scanstackblock((uintptr)(bottom), (uintptr)(top - bottom), gcw);
116 else
117 scanstackblock((uintptr)(top), (uintptr)(bottom - top), gcw);
118 if (nextsp2 != nil) {
119 initialsp2 = (byte*)(void*)(gp->gcinitialsp2);
120 if(initialsp2 > nextsp2)
121 scanstackblock((uintptr)(nextsp2), (uintptr)(initialsp2 - nextsp2), gcw);
122 else
123 scanstackblock((uintptr)(initialsp2), (uintptr)(nextsp2 - initialsp2), gcw);
124 }
125 #endif
126 return true;
127 }
128
129 extern bool onCurrentStack(uintptr p)
130 __asm__(GOSYM_PREFIX "runtime.onCurrentStack");
131
132 bool onCurrentStack(uintptr p)
133 {
134 #ifdef USING_SPLIT_STACK
135
136 void* sp;
137 size_t spsize;
138 void* next_segment;
139 void* next_sp;
140 void* initial_sp;
141
142 sp = __splitstack_find(nil, nil, &spsize, &next_segment, &next_sp,
143 &initial_sp);
144 while (sp != nil) {
145 if (p >= (uintptr)(sp) && p < (uintptr)(sp) + spsize) {
146 return true;
147 }
148 sp = __splitstack_find(next_segment, next_sp, &spsize,
149 &next_segment, &next_sp, &initial_sp);
150 }
151 return false;
152
153 #else
154
155 G* gp;
156 byte* bottom;
157 byte* top;
158 byte* temp;
159 byte* nextsp2;
160 byte* initialsp2;
161
162 gp = runtime_g();
163 bottom = (byte*)(&p);
164 top = (byte*)(void*)(gp->gcinitialsp) + gp->gcstacksize;
165 if ((uintptr)(top) < (uintptr)(bottom)) {
166 temp = top;
167 top = bottom;
168 bottom = temp;
169 }
170 if (p >= (uintptr)(bottom) && p < (uintptr)(top)) {
171 return true;
172 }
173
174 nextsp2 = secondary_stack_pointer();
175 if (nextsp2 != nil) {
176 initialsp2 = (byte*)(void*)(gp->gcinitialsp2);
177 if ((uintptr)(initialsp2) < (uintptr)(nextsp2)) {
178 temp = initialsp2;
179 initialsp2 = nextsp2;
180 nextsp2 = temp;
181 }
182 if (p >= (uintptr)(nextsp2) && p < (uintptr)(initialsp2)) {
183 return true;
184 }
185 }
186
187 return false;
188
189 #endif
190 }