kernel/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


task_type = utils.CachedType("struct task_struct")


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:
        return gdb.parse_and_eval("kgdb_active.counter")
    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)


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

    while True:
        while bits == 0:
            entry += 1
            if entry == num_entries:
                return
            bits = mask[entry]
            if bits != 0:
                bit = 0
                break

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

        cpu = entry * bits_per_entry + bit

        bits >>= 1
        bit += 1

        yield int(cpu)


def each_online_cpu():
    for cpu in cpu_list("__cpu_online_mask"):
        yield cpu


def each_present_cpu():
    for cpu in cpu_list("__cpu_present_mask"):
        yield cpu


def each_possible_cpu():
    for cpu in cpu_list("__cpu_possible_mask"):
        yield cpu


def each_active_cpu():
    for cpu in cpu_list("__cpu_active_mask"):
        yield cpu


class LxCpus(gdb.Command):
    """List CPU status arrays

Displays the known state of each CPU based on the kernel masks
and can help identify the state of hotplugged CPUs"""

    def __init__(self):
        super(LxCpus, self).__init__("lx-cpus", gdb.COMMAND_DATA)

    def invoke(self, arg, from_tty):
        gdb.write("Possible CPUs : {}\n".format(list(each_possible_cpu())))
        gdb.write("Present CPUs  : {}\n".format(list(each_present_cpu())))
        gdb.write("Online CPUs   : {}\n".format(list(each_online_cpu())))
        gdb.write("Active CPUs   : {}\n".format(list(each_active_cpu())))


LxCpus()


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, cpu=-1):
        return per_cpu(var.address, cpu)


PerCpu()

def get_current_task(cpu):
    task_ptr_type = task_type.get_type().pointer()

    if utils.is_target_arch("x86"):
        if gdb.lookup_global_symbol("cpu_tasks"):
            # This is a UML kernel, which stores the current task
            # differently than other x86 sub architectures
            var_ptr = gdb.parse_and_eval("(struct task_struct *)cpu_tasks[0].task")
            return var_ptr.dereference()
        else:
            var_ptr = gdb.parse_and_eval("&pcpu_hot.current_task")
            return per_cpu(var_ptr, cpu).dereference()
    elif utils.is_target_arch("aarch64"):
        current_task_addr = gdb.parse_and_eval("$SP_EL0")
        if (current_task_addr >> 63) != 0:
            current_task = current_task_addr.cast(task_ptr_type)
            return current_task.dereference()
        else:
            raise gdb.GdbError("Sorry, obtaining the current task is not allowed "
                               "while running in userspace(EL0)")
    elif utils.is_target_arch("riscv"):
        current_tp = gdb.parse_and_eval("$tp")
        scratch_reg = gdb.parse_and_eval("$sscratch")

        # by default tp points to current task
        current_task = current_tp.cast(task_ptr_type)

        # scratch register is set 0 in trap handler after entering kernel.
        # When hart is in user mode, scratch register is pointing to task_struct.
        # and tp is used by user mode. So when scratch register holds larger value
        # (negative address as ulong is larger value) than tp, then use scratch register.
        if (scratch_reg.cast(utils.get_ulong_type()) > current_tp.cast(utils.get_ulong_type())):
            current_task = scratch_reg.cast(task_ptr_type)

        return current_task.dereference()
    else:
        raise gdb.GdbError("Sorry, obtaining the current task is not yet "
                           "supported with this arch")

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):
        return get_current_task(cpu)


LxCurrentFunc()