From: Kieran Bingham <kieran.bingham@xxxxxxxxxx> Subject: 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@xxxxxxxxxxx Signed-off-by: Kieran Bingham <kieran.bingham@xxxxxxxxxx> Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- scripts/gdb/linux/constants.py.in | 7 ++ scripts/gdb/linux/radixtree.py | 97 ++++++++++++++++++++++++++++ scripts/gdb/vmlinux-gdb.py | 1 3 files changed, 105 insertions(+) diff -puN scripts/gdb/linux/constants.py.in~scripts-gdb-add-a-radix-tree-parser scripts/gdb/linux/constants.py.in --- a/scripts/gdb/linux/constants.py.in~scripts-gdb-add-a-radix-tree-parser +++ a/scripts/gdb/linux/constants.py.in @@ -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) diff -puN /dev/null scripts/gdb/linux/radixtree.py --- /dev/null +++ a/scripts/gdb/linux/radixtree.py @@ -0,0 +1,97 @@ +# +# gdb helper commands and functions for Linux kernel debugging +# +# Radix Tree Parser +# +# Copyright (c) 2016 Linaro Ltd +# +# Authors: +# Kieran Bingham <kieran.bingham@xxxxxxxxxx> +# +# 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() diff -puN scripts/gdb/vmlinux-gdb.py~scripts-gdb-add-a-radix-tree-parser scripts/gdb/vmlinux-gdb.py --- a/scripts/gdb/vmlinux-gdb.py~scripts-gdb-add-a-radix-tree-parser +++ a/scripts/gdb/vmlinux-gdb.py @@ -31,3 +31,4 @@ else: import linux.lists import linux.proc import linux.constants + import linux.radixtree _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
