Commit 28939c3e authored by Ilya Leoshkevich's avatar Ilya Leoshkevich Committed by Andrew Morton
Browse files

scripts/gdb/symbols: determine KASLR offset on s390 

Use QEMU's qemu.PhyMemMode [1] functionality to read vmcore from the
physical memory the same way the existing dump tooling does this. 
Gracefully handle non-QEMU targets, early boot, and memory corruptions;
print a warning if such situation is detected.

[1] https://qemu-project.gitlab.io/qemu/system/gdb.html#examining-physical-memory

Link: https://lkml.kernel.org/r/20250303110437.79070-1-iii@linux.ibm.com


Signed-off-by: default avatarIlya Leoshkevich <iii@linux.ibm.com>
Acked-by: default avatarJan Kiszka <jan.kiszka@siemens.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Andrew Donnellan <ajd@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Kieran Bingham <kbingham@kernel.org>
Cc: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 8a56f266

scripts/gdb/linux/symbols.py

+30 −1
Original line number Diff line number Diff line
@@ -14,6 +14,7 @@ 
import gdb

import os

import re

import struct



from itertools import count

from linux import modules, utils, constants
@@ -54,6 +55,29 @@ if hasattr(gdb, 'Breakpoint'): 
            return False





def get_vmcore_s390():

    with utils.qemu_phy_mem_mode():

        vmcore_info = 0x0e0c

        paddr_vmcoreinfo_note = gdb.parse_and_eval("*(unsigned long long *)" +

                                                   hex(vmcore_info))

        inferior = gdb.selected_inferior()

        elf_note = inferior.read_memory(paddr_vmcoreinfo_note, 12)

        n_namesz, n_descsz, n_type = struct.unpack(">III", elf_note)

        desc_paddr = paddr_vmcoreinfo_note + len(elf_note) + n_namesz + 1

        return gdb.parse_and_eval("(char *)" + hex(desc_paddr)).string()





def get_kerneloffset():

    if utils.is_target_arch('s390'):

        try:

            vmcore_str = get_vmcore_s390()

        except gdb.error as e:

            gdb.write("{}\n".format(e))

            return None

        return utils.parse_vmcore(vmcore_str).kerneloffset

    return None





class LxSymbols(gdb.Command):

    """(Re-)load symbols of Linux kernel and currently loaded modules.
@@ -160,7 +184,12 @@ lx-symbols command.""" 
                obj.filename.endswith('vmlinux.debug')):

                orig_vmlinux = obj.filename

        gdb.execute("symbol-file", to_string=True)

        gdb.execute("symbol-file {0}".format(orig_vmlinux))

        kerneloffset = get_kerneloffset()

        if kerneloffset is None:

            offset_arg = ""

        else:

            offset_arg = " -o " + hex(kerneloffset)

        gdb.execute("symbol-file {0}{1}".format(orig_vmlinux, offset_arg))



        self.loaded_modules = []

        module_list = modules.module_list()

scripts/gdb/linux/utils.py

+35 −0
Original line number Diff line number Diff line
@@ -11,6 +11,11 @@ 
# This work is licensed under the terms of the GNU GPL version 2.

#



import contextlib

import dataclasses

import re

import typing



import gdb
@@ -216,3 +221,33 @@ def gdb_eval_or_none(expresssion): 
        return gdb.parse_and_eval(expresssion)

    except gdb.error:

        return None





@contextlib.contextmanager

def qemu_phy_mem_mode():

    connection = gdb.selected_inferior().connection

    orig = connection.send_packet("qqemu.PhyMemMode")

    if orig not in b"01":

        raise gdb.error("Unexpected qemu.PhyMemMode")

    orig = orig.decode()

    if connection.send_packet("Qqemu.PhyMemMode:1") != b"OK":

        raise gdb.error("Failed to set qemu.PhyMemMode")

    try:

        yield

    finally:

        if connection.send_packet("Qqemu.PhyMemMode:" + orig) != b"OK":

            raise gdb.error("Failed to restore qemu.PhyMemMode")





@dataclasses.dataclass

class VmCore:

    kerneloffset: typing.Optional[int]





def parse_vmcore(s):

    match = re.search(r"KERNELOFFSET=([0-9a-f]+)", s)

    if match is None:

        kerneloffset = None

    else:

        kerneloffset = int(match.group(1), 16)

    return VmCore(kerneloffset=kerneloffset)