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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
14import gdb
15
16from linux import tasks, utils
17
18
19task_type = utils.CachedType("struct task_struct")
20
21
22MAX_CPUS = 4096
23
24
25def 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 tid = gdb.selected_thread().ptid[2]
30 if tid > (0x100000000 - MAX_CPUS - 2):
31 return 0x100000000 - tid - 2
32 else:
33 return tasks.get_thread_info(tasks.get_task_by_pid(tid))['cpu']
34 else:
35 raise gdb.GdbError("Sorry, obtaining the current CPU is not yet "
36 "supported with this gdb server.")
37
38
39def per_cpu(var_ptr, cpu):
40 if cpu == -1:
41 cpu = get_current_cpu()
42 if utils.is_target_arch("sparc:v9"):
43 offset = gdb.parse_and_eval(
44 "trap_block[{0}].__per_cpu_base".format(str(cpu)))
45 else:
46 try:
47 offset = gdb.parse_and_eval(
48 "__per_cpu_offset[{0}]".format(str(cpu)))
49 except gdb.error:
50 # !CONFIG_SMP case
51 offset = 0
52 pointer = var_ptr.cast(utils.get_long_type()) + offset
53 return pointer.cast(var_ptr.type).dereference()
54
55
56cpu_mask = {}
57
58
59def cpu_mask_invalidate(event):
60 global cpu_mask
61 cpu_mask = {}
62 gdb.events.stop.disconnect(cpu_mask_invalidate)
63 if hasattr(gdb.events, 'new_objfile'):
64 gdb.events.new_objfile.disconnect(cpu_mask_invalidate)
65
66
67def cpu_list(mask_name):
68 global cpu_mask
69 mask = None
70 if mask_name in cpu_mask:
71 mask = cpu_mask[mask_name]
72 if mask is None:
73 mask = gdb.parse_and_eval(mask_name + ".bits")
74 if hasattr(gdb, 'events'):
75 cpu_mask[mask_name] = mask
76 gdb.events.stop.connect(cpu_mask_invalidate)
77 if hasattr(gdb.events, 'new_objfile'):
78 gdb.events.new_objfile.connect(cpu_mask_invalidate)
79 bits_per_entry = mask[0].type.sizeof * 8
80 num_entries = mask.type.sizeof * 8 / bits_per_entry
81 entry = -1
82 bits = 0
83
84 while True:
85 while bits == 0:
86 entry += 1
87 if entry == num_entries:
88 return
89 bits = mask[entry]
90 if bits != 0:
91 bit = 0
92 break
93
94 while bits & 1 == 0:
95 bits >>= 1
96 bit += 1
97
98 cpu = entry * bits_per_entry + bit
99
100 bits >>= 1
101 bit += 1
102
103 yield int(cpu)
104
105
106def each_online_cpu():
107 for cpu in cpu_list("__cpu_online_mask"):
108 yield cpu
109
110
111def each_present_cpu():
112 for cpu in cpu_list("__cpu_present_mask"):
113 yield cpu
114
115
116def each_possible_cpu():
117 for cpu in cpu_list("__cpu_possible_mask"):
118 yield cpu
119
120
121def each_active_cpu():
122 for cpu in cpu_list("__cpu_active_mask"):
123 yield cpu
124
125
126class LxCpus(gdb.Command):
127 """List CPU status arrays
128
129Displays the known state of each CPU based on the kernel masks
130and can help identify the state of hotplugged CPUs"""
131
132 def __init__(self):
133 super(LxCpus, self).__init__("lx-cpus", gdb.COMMAND_DATA)
134
135 def invoke(self, arg, from_tty):
136 gdb.write("Possible CPUs : {}\n".format(list(each_possible_cpu())))
137 gdb.write("Present CPUs : {}\n".format(list(each_present_cpu())))
138 gdb.write("Online CPUs : {}\n".format(list(each_online_cpu())))
139 gdb.write("Active CPUs : {}\n".format(list(each_active_cpu())))
140
141
142LxCpus()
143
144
145class PerCpu(gdb.Function):
146 """Return per-cpu variable.
147
148$lx_per_cpu("VAR"[, CPU]): Return the per-cpu variable called VAR for the
149given CPU number. If CPU is omitted, the CPU of the current context is used.
150Note that VAR has to be quoted as string."""
151
152 def __init__(self):
153 super(PerCpu, self).__init__("lx_per_cpu")
154
155 def invoke(self, var_name, cpu=-1):
156 var_ptr = gdb.parse_and_eval("&" + var_name.string())
157 return per_cpu(var_ptr, cpu)
158
159
160PerCpu()
161
162def get_current_task(cpu):
163 task_ptr_type = task_type.get_type().pointer()
164
165 if utils.is_target_arch("x86"):
166 if gdb.lookup_global_symbol("cpu_tasks"):
167 # This is a UML kernel, which stores the current task
168 # differently than other x86 sub architectures
169 var_ptr = gdb.parse_and_eval("(struct task_struct *)cpu_tasks[0].task")
170 return var_ptr.dereference()
171 else:
172 var_ptr = gdb.parse_and_eval("&pcpu_hot.current_task")
173 return per_cpu(var_ptr, cpu).dereference()
174 elif utils.is_target_arch("aarch64"):
175 current_task_addr = gdb.parse_and_eval("$SP_EL0")
176 if (current_task_addr >> 63) != 0:
177 current_task = current_task_addr.cast(task_ptr_type)
178 return current_task.dereference()
179 else:
180 raise gdb.GdbError("Sorry, obtaining the current task is not allowed "
181 "while running in userspace(EL0)")
182 elif utils.is_target_arch("riscv"):
183 current_tp = gdb.parse_and_eval("$tp")
184 scratch_reg = gdb.parse_and_eval("$sscratch")
185
186 # by default tp points to current task
187 current_task = current_tp.cast(task_ptr_type)
188
189 # scratch register is set 0 in trap handler after entering kernel.
190 # When hart is in user mode, scratch register is pointing to task_struct.
191 # and tp is used by user mode. So when scratch register holds larger value
192 # (negative address as ulong is larger value) than tp, then use scratch register.
193 if (scratch_reg.cast(utils.get_ulong_type()) > current_tp.cast(utils.get_ulong_type())):
194 current_task = scratch_reg.cast(task_ptr_type)
195
196 return current_task.dereference()
197 else:
198 raise gdb.GdbError("Sorry, obtaining the current task is not yet "
199 "supported with this arch")
200
201class LxCurrentFunc(gdb.Function):
202 """Return current task.
203
204$lx_current([CPU]): Return the per-cpu task variable for the given CPU
205number. If CPU is omitted, the CPU of the current context is used."""
206
207 def __init__(self):
208 super(LxCurrentFunc, self).__init__("lx_current")
209
210 def invoke(self, cpu=-1):
211 return get_current_task(cpu)
212
213
214LxCurrentFunc()