[PATCH v11 17/28] scripts/gdb: Add internal helper and convenience function for per-cpu lookup

[Jan Kiszka <jan.kiszka@siemens.com>]

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/linux/cpus.py  | 68 ++++++++++++++++++++++++++++++++++++++++++++++
 scripts/gdb/vmlinux-gdb.py |  1 +
 2 files changed, 69 insertions(+)
 create mode 100644 scripts/gdb/linux/cpus.py

diff --git a/scripts/gdb/linux/cpus.py b/scripts/gdb/linux/cpus.py
new file mode 100644
index 0000000..18337e0
--- /dev/null
+++ b/scripts/gdb/linux/cpus.py
@@ -0,0 +1,68 @@
+#
+# gdb helper commands and functions for Linux kernel debugging
+#
+#  per-cpu tools
+#
+# Copyright (c) Siemens AG, 2011-2013
+#
+# Authors:
+#  Jan Kiszka <jan.kiszka@siemens.com>
+#
+# This work is licensed under the terms of the GNU GPL version 2.
+#
+
+import gdb
+
+from linux import tasks, utils
+
+
+MAX_CPUS = 4096
+
+
+def get_current_cpu():
+    if utils.get_gdbserver_type() == utils.GDBSERVER_QEMU:
+        return gdb.selected_thread().num - 1
+    elif utils.get_gdbserver_type() == utils.GDBSERVER_KGDB:
+        tid = gdb.selected_thread().ptid[2]
+        if tid > (0x100000000 - MAX_CPUS - 2):
+            return 0x100000000 - tid - 2
+        else:
+            return tasks.get_thread_info(tasks.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_ptr, cpu):
+    if cpu == -1:
+        cpu = get_current_cpu()
+    if utils.is_target_arch("sparc:v9"):
+        offset = gdb.parse_and_eval(
+            "trap_block[{0}].__per_cpu_base".format(str(cpu)))
+    else:
+        try:
+            offset = gdb.parse_and_eval(
+                "__per_cpu_offset[{0}]".format(str(cpu)))
+        except gdb.error:
+            # !CONFIG_SMP case
+            offset = 0
+    pointer = var_ptr.cast(utils.get_long_type()) + offset
+    return pointer.cast(var_ptr.type).dereference()
+
+
+class PerCpu(gdb.Function):
+    """Return per-cpu variable.
+
+$lx_per_cpu("VAR"[, CPU]): Return the per-cpu variable called VAR for the
+given CPU number. If CPU is omitted, the CPU of the current context is used.
+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):
+        var_ptr = gdb.parse_and_eval("&" + var_name.string())
+        return per_cpu(var_ptr, cpu)
+
+
+PerCpu()
diff --git a/scripts/gdb/vmlinux-gdb.py b/scripts/gdb/vmlinux-gdb.py
index 4d7eb2c..4848928 100644
--- a/scripts/gdb/vmlinux-gdb.py
+++ b/scripts/gdb/vmlinux-gdb.py
@@ -27,3 +27,4 @@ else:
     import linux.modules
     import linux.dmesg
     import linux.tasks
+    import linux.cpus
-- 
2.1.4