scripts/gdb/linux/dmesg.py

File Facts

System

Linux kernel

Corpus path

scripts/gdb/linux/dmesg.py

Extension

.py

Size

5822 bytes

Lines

153

Domain

Support Tooling And Documentation

Bucket

scripts

Inferred role

Support Tooling And Documentation: scripts

Status

atlas-only

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

• Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.
• Uses kernel synchronization; read lock ordering, sleepability, and interrupt context assumptions before translating.
• Defines or uses C structs; map object ownership, embedded links, reference counts, and lock ownership.

Dependency Surface

• No C-style include directives detected by the generator.

Detected Declarations

• No top-level syscall, struct, function, initcall, or export declaration detected by the generator.

Annotated Snippet

#
# gdb helper commands and functions for Linux kernel debugging
#
#  kernel log buffer dump
#
# Copyright (c) Siemens AG, 2011, 2012
#
# Authors:
#  Jan Kiszka <jan.kiszka@siemens.com>
#
# This work is licensed under the terms of the GNU GPL version 2.
#

import gdb
import sys

from linux import utils

printk_info_type = utils.CachedType("struct printk_info")
prb_data_blk_lpos_type = utils.CachedType("struct prb_data_blk_lpos")
prb_desc_type = utils.CachedType("struct prb_desc")
prb_desc_ring_type = utils.CachedType("struct prb_desc_ring")
prb_data_ring_type = utils.CachedType("struct prb_data_ring")
printk_ringbuffer_type = utils.CachedType("struct printk_ringbuffer")

class LxDmesg(gdb.Command):
    """Print Linux kernel log buffer."""

    def __init__(self):
        super(LxDmesg, self).__init__("lx-dmesg", gdb.COMMAND_DATA)

    def invoke(self, arg, from_tty):
        inf = gdb.inferiors()[0]

        # read in prb structure
        prb_addr = int(str(gdb.parse_and_eval("(void *)'printk.c'::prb")).split()[0], 16)
        sz = printk_ringbuffer_type.get_type().sizeof
        prb = utils.read_memoryview(inf, prb_addr, sz).tobytes()

        # read in descriptor ring structure
        off = printk_ringbuffer_type.get_type()['desc_ring'].bitpos // 8
        addr = prb_addr + off
        sz = prb_desc_ring_type.get_type().sizeof
        desc_ring = utils.read_memoryview(inf, addr, sz).tobytes()

        # read in descriptor count, size, and address
        off = prb_desc_ring_type.get_type()['count_bits'].bitpos // 8
        desc_ring_count = 1 << utils.read_u32(desc_ring, off)
        desc_sz = prb_desc_type.get_type().sizeof
        off = prb_desc_ring_type.get_type()['descs'].bitpos // 8
        desc_addr = utils.read_ulong(desc_ring, off)

        # read in info size and address
        info_sz = printk_info_type.get_type().sizeof
        off = prb_desc_ring_type.get_type()['infos'].bitpos // 8
        info_addr = utils.read_ulong(desc_ring, off)

        # read in text data ring structure
        off = printk_ringbuffer_type.get_type()['text_data_ring'].bitpos // 8
        addr = prb_addr + off
        sz = prb_data_ring_type.get_type().sizeof
        text_data_ring = utils.read_memoryview(inf, addr, sz).tobytes()

        # read in text data size and address
        off = prb_data_ring_type.get_type()['size_bits'].bitpos // 8
        text_data_sz = 1 << utils.read_u32(text_data_ring, off)
        off = prb_data_ring_type.get_type()['data'].bitpos // 8
        text_data_addr = utils.read_ulong(text_data_ring, off)

        sv_off = prb_desc_type.get_type()['state_var'].bitpos // 8

Annotation

• Atlas domain: Support Tooling And Documentation / scripts.
• Implementation status: atlas-only.
• Synchronization appears in or near this file; preserve lock ordering, sleepability, and interrupt-context constraints.

Implementation Notes

• This generated page is the file-by-file coverage layer; curated subsystem chapters should link here when they synthesize a multi-file control flow.
• Core OS pages should be promoted from atlas-only to deep-reviewed when they explain data structures, invariants, locking, lifecycle, and C implementation snippets.
• Driver-family pages are intentionally pattern-oriented unless they are part of the selected PCIe/NVMe representative device path.