scripts/gdb/linux/cpus.py

#
# 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()


cpu_mask = {}


def cpu_mask_invalidate(event):
    global cpu_mask
    cpu_mask = {}
    gdb.events.stop.disconnect(cpu_mask_invalidate)
    if hasattr(gdb.events, 'new_objfile'):
        gdb.events.new_objfile.disconnect(cpu_mask_invalidate)


class CpuList():
    def __init__(self, mask_name):
        global cpu_mask
        self.mask = None
        if mask_name in cpu_mask:
            self.mask = cpu_mask[mask_name]
        if self.mask is None:
            self.mask = gdb.parse_and_eval(mask_name + ".bits")
            if hasattr(gdb, 'events'):
                cpu_mask[mask_name] = self.mask
                gdb.events.stop.connect(cpu_mask_invalidate)
                if hasattr(gdb.events, 'new_objfile'):
                    gdb.events.new_objfile.connect(cpu_mask_invalidate)
        self.bits_per_entry = self.mask[0].type.sizeof * 8
        self.num_entries = self.mask.type.sizeof * 8 / self.bits_per_entry
        self.entry = -1
        self.bits = 0

    def __iter__(self):
        return self

    def next(self):
        while self.bits == 0:
            self.entry += 1
            if self.entry == self.num_entries:
                raise StopIteration
            self.bits = self.mask[self.entry]
            if self.bits != 0:
                self.bit = 0
                break

        while self.bits & 1 == 0:
            self.bits >>= 1
            self.bit += 1

        cpu = self.entry * self.bits_per_entry + self.bit

        self.bits >>= 1
        self.bit += 1

        return cpu


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()


class LxCurrentFunc(gdb.Function):
    """Return current task.

$lx_current([CPU]): Return the per-cpu task variable for the given CPU
number. If CPU is omitted, the CPU of the current context is used."""

    def __init__(self):
        super(LxCurrentFunc, self).__init__("lx_current")

    def invoke(self, cpu=-1):
        var_ptr = gdb.parse_and_eval("&current_task")
        return per_cpu(var_ptr, cpu).dereference()


LxCurrentFunc()