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Commit e2b74f23 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'akpm' (patches from Andrew) 

Merge yet more updates from Andrew Morton:

 - a pile of minor fs fixes and cleanups

 - kexec updates

 - random misc fixes in various places: vmcore, rbtree, eventfd, ipc, seccomp.

 - a series of python-based kgdb helper scripts

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (58 commits)
  seccomp: cap SECCOMP_RET_ERRNO data to MAX_ERRNO
  samples/seccomp: improve label helper
  ipc,sem: use current->state helpers
  scripts/gdb: disable pagination while printing from breakpoint handler
  scripts/gdb: define maintainer
  scripts/gdb: convert CpuList to generator function
  scripts/gdb: convert ModuleList to generator function
  scripts/gdb: use a generator instead of iterator for task list
  scripts/gdb: ignore byte-compiled python files
  scripts/gdb: port to python3 / gdb7.7
  scripts/gdb: add basic documentation
  scripts/gdb: add lx-lsmod command
  scripts/gdb: add class to iterate over CPU masks
  scripts/gdb: add lx_current convenience function
  scripts/gdb: add internal helper and convenience function for per-cpu lookup
  scripts/gdb: add get_gdbserver_type helper
  scripts/gdb: add internal helper and convenience function to retrieve thread_info
  scripts/gdb: add is_target_arch helper
  scripts/gdb: add helper and convenience function to look up tasks
  scripts/gdb: add task iteration class
  ...
parents 9cd77374 580c57f1

.gitignore

+1 −0
Original line number Diff line number Diff line
@@ -43,6 +43,7 @@ Module.symvers 
/TAGS

/linux

/vmlinux

/vmlinux-gdb.py

/vmlinuz

/System.map

/Module.markers

Documentation/gdb-kernel-debugging.txt

0 → 100644
+160 −0
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Debugging kernel and modules via gdb

====================================



The kernel debugger kgdb, hypervisors like QEMU or JTAG-based hardware

interfaces allow to debug the Linux kernel and its modules during runtime

using gdb. Gdb comes with a powerful scripting interface for python. The

kernel provides a collection of helper scripts that can simplify typical

kernel debugging steps. This is a short tutorial about how to enable and use

them. It focuses on QEMU/KVM virtual machines as target, but the examples can

be transferred to the other gdb stubs as well.





Requirements

------------



 o gdb 7.2+ (recommended: 7.4+) with python support enabled (typically true

   for distributions)





Setup

-----



 o Create a virtual Linux machine for QEMU/KVM (see www.linux-kvm.org and

   www.qemu.org for more details). For cross-development,

   http://landley.net/aboriginal/bin keeps a pool of machine images and

   toolchains that can be helpful to start from.



 o Build the kernel with CONFIG_GDB_SCRIPTS enabled, but leave

   CONFIG_DEBUG_INFO_REDUCED off. If your architecture supports

   CONFIG_FRAME_POINTER, keep it enabled.



 o Install that kernel on the guest.



   Alternatively, QEMU allows to boot the kernel directly using -kernel,

   -append, -initrd command line switches. This is generally only useful if

   you do not depend on modules. See QEMU documentation for more details on

   this mode.



 o Enable the gdb stub of QEMU/KVM, either

    - at VM startup time by appending "-s" to the QEMU command line

   or

    - during runtime by issuing "gdbserver" from the QEMU monitor

      console



 o cd /path/to/linux-build



 o Start gdb: gdb vmlinux



   Note: Some distros may restrict auto-loading of gdb scripts to known safe

   directories. In case gdb reports to refuse loading vmlinux-gdb.py, add



    add-auto-load-safe-path /path/to/linux-build



   to ~/.gdbinit. See gdb help for more details.



 o Attach to the booted guest:

    (gdb) target remote :1234





Examples of using the Linux-provided gdb helpers

------------------------------------------------



 o Load module (and main kernel) symbols:

    (gdb) lx-symbols

    loading vmlinux

    scanning for modules in /home/user/linux/build

    loading @0xffffffffa0020000: /home/user/linux/build/net/netfilter/xt_tcpudp.ko

    loading @0xffffffffa0016000: /home/user/linux/build/net/netfilter/xt_pkttype.ko

    loading @0xffffffffa0002000: /home/user/linux/build/net/netfilter/xt_limit.ko

    loading @0xffffffffa00ca000: /home/user/linux/build/net/packet/af_packet.ko

    loading @0xffffffffa003c000: /home/user/linux/build/fs/fuse/fuse.ko

    ...

    loading @0xffffffffa0000000: /home/user/linux/build/drivers/ata/ata_generic.ko



 o Set a breakpoint on some not yet loaded module function, e.g.:

    (gdb) b btrfs_init_sysfs

    Function "btrfs_init_sysfs" not defined.

    Make breakpoint pending on future shared library load? (y or [n]) y

    Breakpoint 1 (btrfs_init_sysfs) pending.



 o Continue the target

    (gdb) c



 o Load the module on the target and watch the symbols being loaded as well as

   the breakpoint hit:

    loading @0xffffffffa0034000: /home/user/linux/build/lib/libcrc32c.ko

    loading @0xffffffffa0050000: /home/user/linux/build/lib/lzo/lzo_compress.ko

    loading @0xffffffffa006e000: /home/user/linux/build/lib/zlib_deflate/zlib_deflate.ko

    loading @0xffffffffa01b1000: /home/user/linux/build/fs/btrfs/btrfs.ko



    Breakpoint 1, btrfs_init_sysfs () at /home/user/linux/fs/btrfs/sysfs.c:36

    36              btrfs_kset = kset_create_and_add("btrfs", NULL, fs_kobj);



 o Dump the log buffer of the target kernel:

    (gdb) lx-dmesg

    [     0.000000] Initializing cgroup subsys cpuset

    [     0.000000] Initializing cgroup subsys cpu

    [     0.000000] Linux version 3.8.0-rc4-dbg+ (...

    [     0.000000] Command line: root=/dev/sda2 resume=/dev/sda1 vga=0x314

    [     0.000000] e820: BIOS-provided physical RAM map:

    [     0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable

    [     0.000000] BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved

    ....



 o Examine fields of the current task struct:

    (gdb) p $lx_current().pid

    $1 = 4998

    (gdb) p $lx_current().comm

    $2 = "modprobe\000\000\000\000\000\000\000"



 o Make use of the per-cpu function for the current or a specified CPU:

    (gdb) p $lx_per_cpu("runqueues").nr_running

    $3 = 1

    (gdb) p $lx_per_cpu("runqueues", 2).nr_running

    $4 = 0



 o Dig into hrtimers using the container_of helper:

    (gdb) set $next = $lx_per_cpu("hrtimer_bases").clock_base[0].active.next

    (gdb) p *$container_of($next, "struct hrtimer", "node")

    $5 = {

      node = {

        node = {

          __rb_parent_color = 18446612133355256072,

          rb_right = 0x0 <irq_stack_union>,

          rb_left = 0x0 <irq_stack_union>

        },

        expires = {

          tv64 = 1835268000000

        }

      },

      _softexpires = {

        tv64 = 1835268000000

      },

      function = 0xffffffff81078232 <tick_sched_timer>,

      base = 0xffff88003fd0d6f0,

      state = 1,

      start_pid = 0,

      start_site = 0xffffffff81055c1f <hrtimer_start_range_ns+20>,

      start_comm = "swapper/2\000\000\000\000\000\000"

    }





List of commands and functions

------------------------------



The number of commands and convenience functions may evolve over the time,

this is just a snapshot of the initial version:



 (gdb) apropos lx

 function lx_current -- Return current task

 function lx_module -- Find module by name and return the module variable

 function lx_per_cpu -- Return per-cpu variable

 function lx_task_by_pid -- Find Linux task by PID and return the task_struct variable

 function lx_thread_info -- Calculate Linux thread_info from task variable

 lx-dmesg -- Print Linux kernel log buffer

 lx-lsmod -- List currently loaded modules

 lx-symbols -- (Re-)load symbols of Linux kernel and currently loaded modules



Detailed help can be obtained via "help <command-name>" for commands and "help

function <function-name>" for convenience functions.

MAINTAINERS

+5 −0
Original line number Diff line number Diff line
@@ -4232,6 +4232,11 @@ W: http://www.icp-vortex.com/ 
S:	Supported

F:	drivers/scsi/gdt*



GDB KERNEL DEBUGGING HELPER SCRIPTS

M:	Jan Kiszka <jan.kiszka@siemens.com>

S:	Supported

F:	scripts/gdb/



GEMTEK FM RADIO RECEIVER DRIVER

M:	Hans Verkuil <hverkuil@xs4all.nl>

L:	linux-media@vger.kernel.org

Makefile

+4 −1
Original line number Diff line number Diff line
@@ -926,6 +926,9 @@ ifdef CONFIG_SAMPLES 
endif

ifdef CONFIG_BUILD_DOCSRC

	$(Q)$(MAKE) $(build)=Documentation

endif

ifdef CONFIG_GDB_SCRIPTS

	$(Q)ln -fsn `cd $(srctree) && /bin/pwd`/scripts/gdb/vmlinux-gdb.py

endif

	+$(call if_changed,link-vmlinux)
@@ -1181,7 +1184,7 @@ MRPROPER_FILES += .config .config.old .version .old_version $(version_h) \ 
		  Module.symvers tags TAGS cscope* GPATH GTAGS GRTAGS GSYMS \

		  signing_key.priv signing_key.x509 x509.genkey		\

		  extra_certificates signing_key.x509.keyid		\

		  signing_key.x509.signer

		  signing_key.x509.signer vmlinux-gdb.py



# clean - Delete most, but leave enough to build external modules

#

arch/powerpc/kernel/machine_kexec_64.c

+0 −2
Original line number Diff line number Diff line
@@ -96,8 +96,6 @@ int default_machine_kexec_prepare(struct kimage *image) 
	return 0;

}



#define IND_FLAGS (IND_DESTINATION | IND_INDIRECTION | IND_DONE | IND_SOURCE)



static void copy_segments(unsigned long ind)

{

	unsigned long entry;