[PATCH v4 12/13] scripts/gdb: Add internal helper and convenience function for per-cpu lookup

Jan Kiszka
2013-01-21T17:18:45Z

This function allows to obtain a per-cpu variable, either of the current
or an explicitly specified CPU.

Note: sparc64 version is untested.

CC: "David S. Miller" <davem@davemloft.net>
CC: sparclinux@vger.kernel.org
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
scripts/gdb/percpu.py | 61 ++++++++++++++++++++++++++++++++++++++++++++
scripts/gdb/vmlinux-gdb.py | 1 +
2 files changed, 62 insertions(+), 0 deletions(-)
create mode 100644 scripts/gdb/percpu.py

diff --git a/scripts/gdb/percpu.py b/scripts/gdb/percpu.py
new file mode 100644
index 0000000..e2556919
--- /dev/null
+++ b/scripts/gdb/percpu.py
@@ -0,0 +1,61 @@
+#
+# gdb helper commands and functions for Linux kernel debugging
+#
+# per-cpu tools
+#
+# Copyright (c) Siemens AG, 2011, 2012
+#
+# Authors:
+# Jan Kiszka <jan.kiszka@siemens.com>
+#
+# This work is licensed under the terms of the GNU GPL version 2.
+#
+
+import gdb
+
+from utils import *
+from task import *
+
+MAX_CPUS = 4096
+
+def get_current_cpu():
+ if get_gdbserver_type() == GDBSERVER_QEMU:
+ return gdb.selected_thread().num - 1
+ elif get_gdbserver_type() == GDBSERVER_KGDB:
+ tid = gdb.selected_thread().ptid[2]
+ if tid > (0x100000000 - MAX_CPUS - 2):
+ return 0x100000000 - tid - 2
+ else:
+ return get_thread_info(get_task_by_pid(tid))['cpu']
+ else:
+ raise gdb.GdbError("Sorry, obtaining the current CPU is "
+ "not yet supported with this gdb server.")
+
+def per_cpu(var_name, cpu):
+ var = gdb.parse_and_eval("&" + var_name)
+ if cpu == -1:
+ cpu = get_current_cpu()
+ if is_target_arch("sparc:v9"):
+ offset = gdb.parse_and_eval("trap_block[" + str(cpu) +
+ "].__per_cpu_base")
+ else:
+ offset = gdb.parse_and_eval("__per_cpu_offset[" + str(cpu) +
+ "]")
+ pointer = var.cast(get_long_type()) + offset
+ return pointer.cast(var.type).dereference()
+
+
+class PerCpu(gdb.Function):
+ __doc__ = "Return per-cpu variable.\n" \
+ "\n" \
+ "$lx_per_cpu(\"VAR\"[, CPU]): Return the per-cpu variable called VAR for the\n" \
+ "given CPU number. If CPU is omitted, the CPU of the current context is used.\n" \
+ "Note that VAR has to be quoted as string."
+
+ def __init__(self):
+ super(PerCpu, self).__init__("lx_per_cpu")
+
+ def invoke(self, var_name, cpu = -1):
+ return per_cpu(var_name.string(), cpu)
+
+PerCpu()
diff --git a/scripts/gdb/vmlinux-gdb.py b/scripts/gdb/vmlinux-gdb.py
index e78b353..6606247 100644
--- a/scripts/gdb/vmlinux-gdb.py
+++ b/scripts/gdb/vmlinux-gdb.py
@@ -25,3 +25,4 @@ else:
import symbols
import dmesg
import task
+ import percpu
--
1.7.3.4