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Commit e127a73d authored by Kieran Bingham's avatar Kieran Bingham Committed by Linus Torvalds
Browse files

scripts/gdb: add a Radix Tree Parser 

Linux makes use of the Radix Tree data structure to store pointers
indexed by integer values.  This structure is utilised across many
structures in the kernel including the IRQ descriptor tables, and
several filesystems.

This module provides a method to lookup values from a structure given
its head node.

Usage:

The function lx_radix_tree_lookup, must be given a symbol of type struct
radix_tree_root, and an index into that tree.

The object returned is a generic integer value, and must be cast
correctly to the type based on the storage in the data structure.

For example, to print the irq descriptor in the sparse irq_desc_tree at
index 18, try the following:

 (gdb) print (struct irq_desc)$lx_radix_tree_lookup(irq_desc_tree, 18)

Link: http://lkml.kernel.org/r/d2028c55e50cf95a9b7f8ca0d11885174b0cc709.1462865983.git.jan.kiszka@siemens.com


Signed-off-by: default avatarKieran Bingham <kieran.bingham@linaro.org>
Signed-off-by: default avatarJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4bc393db

scripts/gdb/linux/constants.py.in

+7 −0
Original line number Diff line number Diff line
@@ -14,6 +14,7 @@ 


#include <linux/fs.h>

#include <linux/mount.h>

#include <linux/radix-tree.h>



/* We need to stringify expanded macros so that they can be parsed */
@@ -50,3 +51,9 @@ LX_VALUE(MNT_NOEXEC) 
LX_VALUE(MNT_NOATIME)

LX_VALUE(MNT_NODIRATIME)

LX_VALUE(MNT_RELATIME)



/* linux/radix-tree.h */

LX_VALUE(RADIX_TREE_INDIRECT_PTR)

LX_GDBPARSED(RADIX_TREE_HEIGHT_MASK)

LX_GDBPARSED(RADIX_TREE_MAP_SHIFT)

LX_GDBPARSED(RADIX_TREE_MAP_MASK)

scripts/gdb/linux/radixtree.py

0 → 100644
+97 −0
Original line number Diff line number Diff line 
#

# gdb helper commands and functions for Linux kernel debugging

#

#  Radix Tree Parser

#

# Copyright (c) 2016 Linaro Ltd

#

# Authors:

#  Kieran Bingham <kieran.bingham@linaro.org>

#

# This work is licensed under the terms of the GNU GPL version 2.

#



import gdb



from linux import utils

from linux import constants



radix_tree_root_type = utils.CachedType("struct radix_tree_root")

radix_tree_node_type = utils.CachedType("struct radix_tree_node")





def is_indirect_ptr(node):

    long_type = utils.get_long_type()

    return (node.cast(long_type) & constants.LX_RADIX_TREE_INDIRECT_PTR)





def indirect_to_ptr(node):

    long_type = utils.get_long_type()

    node_type = node.type

    indirect_ptr = node.cast(long_type) & ~constants.LX_RADIX_TREE_INDIRECT_PTR

    return indirect_ptr.cast(node_type)





def maxindex(height):

    height = height & constants.LX_RADIX_TREE_HEIGHT_MASK

    return gdb.parse_and_eval("height_to_maxindex["+str(height)+"]")





def lookup(root, index):

    if root.type == radix_tree_root_type.get_type().pointer():

        root = root.dereference()

    elif root.type != radix_tree_root_type.get_type():

        raise gdb.GdbError("Must be struct radix_tree_root not {}"

                           .format(root.type))



    node = root['rnode']

    if node is 0:

        return None



    if not (is_indirect_ptr(node)):

        if (index > 0):

            return None

        return node



    node = indirect_to_ptr(node)



    height = node['path'] & constants.LX_RADIX_TREE_HEIGHT_MASK

    if (index > maxindex(height)):

        return None



    shift = (height-1) * constants.LX_RADIX_TREE_MAP_SHIFT



    while True:

        new_index = (index >> shift) & constants.LX_RADIX_TREE_MAP_MASK

        slot = node['slots'][new_index]



        node = slot.cast(node.type.pointer()).dereference()

        if node is 0:

            return None



        shift -= constants.LX_RADIX_TREE_MAP_SHIFT

        height -= 1



        if (height <= 0):

            break



    return node





class LxRadixTree(gdb.Function):

    """ Lookup and return a node from a RadixTree.



$lx_radix_tree_lookup(root_node [, index]): Return the node at the given index.

If index is omitted, the root node is dereferenced and returned."""



    def __init__(self):

        super(LxRadixTree, self).__init__("lx_radix_tree_lookup")



    def invoke(self, root, index=0):

        result = lookup(root, index)

        if result is None:

            raise gdb.GdbError("No entry in tree at index {}".format(index))



        return result



LxRadixTree()

scripts/gdb/vmlinux-gdb.py

+1 −0
Original line number Diff line number Diff line
@@ -31,3 +31,4 @@ else: 
    import linux.lists

    import linux.proc

    import linux.constants

    import linux.radixtree