1 #
2 # gdb helper commands and functions for Linux kernel debugging
3 #
4 # per-cpu tools
5 #
6 # Copyright (c) Siemens AG, 2011-2013
7 #
8 # Authors:
9 # Jan Kiszka <jan.kiszka@siemens.com>
10 #
11 # This work is licensed under the terms of the GNU GPL version 2.
12 #
13
14 import gdb
15
16 from linux import tasks, utils
17
18
19 task_type = utils.CachedType("struct task_struct")
20
21
22 MAX_CPUS = 4096
23
24
25 def get_current_cpu():
26 if utils.get_gdbserver_type() == utils.GDBSERVER_QEMU:
27 return gdb.selected_thread().num - 1
28 elif utils.get_gdbserver_type() == utils.GDBSERVER_KGDB:
29 return gdb.parse_and_eval("kgdb_active.counter")
30 else:
31 raise gdb.GdbError("Sorry, obtaining the current CPU is not yet "
32 "supported with this gdb server.")
33
34
35 def per_cpu(var_ptr, cpu):
36 if cpu == -1:
37 cpu = get_current_cpu()
38 if utils.is_target_arch("sparc:v9"):
39 offset = gdb.parse_and_eval(
40 "trap_block[{0}].__per_cpu_base".format(str(cpu)))
41 else:
42 try:
43 offset = gdb.parse_and_eval(
44 "__per_cpu_offset[{0}]".format(str(cpu)))
45 except gdb.error:
46 # !CONFIG_SMP case
47 offset = 0
48 pointer = var_ptr.cast(utils.get_long_type()) + offset
49 return pointer.cast(var_ptr.type).dereference()
50
51
52 cpu_mask = {}
53
54
55 def cpu_mask_invalidate(event):
56 global cpu_mask
57 cpu_mask = {}
58 gdb.events.stop.disconnect(cpu_mask_invalidate)
59 if hasattr(gdb.events, 'new_objfile'):
60 gdb.events.new_objfile.disconnect(cpu_mask_invalidate)
61
62
63 def cpu_list(mask_name):
64 global cpu_mask
65 mask = None
66 if mask_name in cpu_mask:
67 mask = cpu_mask[mask_name]
68 if mask is None:
69 mask = gdb.parse_and_eval(mask_name + ".bits")
70 if hasattr(gdb, 'events'):
71 cpu_mask[mask_name] = mask
72 gdb.events.stop.connect(cpu_mask_invalidate)
73 if hasattr(gdb.events, 'new_objfile'):
74 gdb.events.new_objfile.connect(cpu_mask_invalidate)
75 bits_per_entry = mask[0].type.sizeof * 8
76 num_entries = mask.type.sizeof * 8 / bits_per_entry
77 entry = -1
78 bits = 0
79
80 while True:
81 while bits == 0:
82 entry += 1
83 if entry == num_entries:
84 return
85 bits = mask[entry]
86 if bits != 0:
87 bit = 0
88 break
89
90 while bits & 1 == 0:
91 bits >>= 1
92 bit += 1
93
94 cpu = entry * bits_per_entry + bit
95
96 bits >>= 1
97 bit += 1
98
99 yield int(cpu)
100
101
102 def each_online_cpu():
103 for cpu in cpu_list("__cpu_online_mask"):
104 yield cpu
105
106
107 def each_present_cpu():
108 for cpu in cpu_list("__cpu_present_mask"):
109 yield cpu
110
111
112 def each_possible_cpu():
113 for cpu in cpu_list("__cpu_possible_mask"):
114 yield cpu
115
116
117 def each_active_cpu():
118 for cpu in cpu_list("__cpu_active_mask"):
119 yield cpu
120
121
122 class LxCpus(gdb.Command):
123 """List CPU status arrays
124
125 Displays the known state of each CPU based on the kernel masks
126 and can help identify the state of hotplugged CPUs"""
127
128 def __init__(self):
129 super(LxCpus, self).__init__("lx-cpus", gdb.COMMAND_DATA)
130
131 def invoke(self, arg, from_tty):
132 gdb.write("Possible CPUs : {}\n".format(list(each_possible_cpu())))
133 gdb.write("Present CPUs : {}\n".format(list(each_present_cpu())))
134 gdb.write("Online CPUs : {}\n".format(list(each_online_cpu())))
135 gdb.write("Active CPUs : {}\n".format(list(each_active_cpu())))
136
137
138 LxCpus()
139
140
141 class PerCpu(gdb.Function):
142 """Return per-cpu variable.
143
144 $lx_per_cpu("VAR"[, CPU]): Return the per-cpu variable called VAR for the
145 given CPU number. If CPU is omitted, the CPU of the current context is used.
146 Note that VAR has to be quoted as string."""
147
148 def __init__(self):
149 super(PerCpu, self).__init__("lx_per_cpu")
150
151 def invoke(self, var, cpu=-1):
152 return per_cpu(var.address, cpu)
153
154
155 PerCpu()
156
157 def get_current_task(cpu):
158 task_ptr_type = task_type.get_type().pointer()
159
160 if utils.is_target_arch("x86"):
161 if gdb.lookup_global_symbol("cpu_tasks"):
162 # This is a UML kernel, which stores the current task
163 # differently than other x86 sub architectures
164 var_ptr = gdb.parse_and_eval("(struct task_struct *)cpu_tasks[0].task")
165 return var_ptr.dereference()
166 else:
167 var_ptr = gdb.parse_and_eval("&pcpu_hot.current_task")
168 return per_cpu(var_ptr, cpu).dereference()
169 elif utils.is_target_arch("aarch64"):
170 current_task_addr = gdb.parse_and_eval("$SP_EL0")
171 if (current_task_addr >> 63) != 0:
172 current_task = current_task_addr.cast(task_ptr_type)
173 return current_task.dereference()
174 else:
175 raise gdb.GdbError("Sorry, obtaining the current task is not allowed "
176 "while running in userspace(EL0)")
177 elif utils.is_target_arch("riscv"):
178 current_tp = gdb.parse_and_eval("$tp")
179 scratch_reg = gdb.parse_and_eval("$sscratch")
180
181 # by default tp points to current task
182 current_task = current_tp.cast(task_ptr_type)
183
184 # scratch register is set 0 in trap handler after entering kernel.
185 # When hart is in user mode, scratch register is pointing to task_struct.
186 # and tp is used by user mode. So when scratch register holds larger value
187 # (negative address as ulong is larger value) than tp, then use scratch register.
188 if (scratch_reg.cast(utils.get_ulong_type()) > current_tp.cast(utils.get_ulong_type())):
189 current_task = scratch_reg.cast(task_ptr_type)
190
191 return current_task.dereference()
192 else:
193 raise gdb.GdbError("Sorry, obtaining the current task is not yet "
194 "supported with this arch")
195
196 class LxCurrentFunc(gdb.Function):
197 """Return current task.
198
199 $lx_current([CPU]): Return the per-cpu task variable for the given CPU
200 number. If CPU is omitted, the CPU of the current context is used."""
201
202 def __init__(self):
203 super(LxCurrentFunc, self).__init__("lx_current")
204
205 def invoke(self, cpu=-1):
206 return get_current_task(cpu)
207
208
209 LxCurrentFunc()
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