On 2016-08-09 01:35, Jonathan Corbet wrote:
> Cc: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
> Signed-off-by: Jonathan Corbet <corbet@xxxxxxx>
> ---
> .../gdb-kernel-debugging.rst} | 77 +++++++++++++---------
> Documentation/dev-tools/tools.rst | 1 +
> 2 files changed, 46 insertions(+), 32 deletions(-)
> rename Documentation/{gdb-kernel-debugging.txt => dev-tools/gdb-kernel-debugging.rst} (73%)
>
> diff --git a/Documentation/gdb-kernel-debugging.txt b/Documentation/dev-tools/gdb-kernel-debugging.rst
> similarity index 73%
> rename from Documentation/gdb-kernel-debugging.txt
> rename to Documentation/dev-tools/gdb-kernel-debugging.rst
> index 7050ce8..5e93c9b 100644
> --- a/Documentation/gdb-kernel-debugging.txt
> +++ b/Documentation/dev-tools/gdb-kernel-debugging.rst
> @@ -1,3 +1,5 @@
> +.. highlight:: none
> +
> Debugging kernel and modules via gdb
> ====================================
>
> @@ -13,54 +15,58 @@ 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)
> +- 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.
> +- 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.
> +- 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.
> +- 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.
>
> - 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.
> +- Enable the gdb stub of QEMU/KVM, either
>
> - o Enable the gdb stub of QEMU/KVM, either
> - at VM startup time by appending "-s" to the QEMU command line
> - or
> +
> + or
> +
> - during runtime by issuing "gdbserver" from the QEMU monitor
> console
>
> - o cd /path/to/linux-build
> +- cd /path/to/linux-build
>
> - o Start gdb: gdb vmlinux
> +- 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
> + 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.
> + to ~/.gdbinit. See gdb help for more details.
> +
> +- Attach to the booted guest::
>
> - 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:
> +- Load module (and main kernel) symbols::
> +
> (gdb) lx-symbols
> loading vmlinux
> scanning for modules in /home/user/linux/build
> @@ -72,17 +78,20 @@ Examples of using the Linux-provided gdb helpers
> ...
> loading @0xffffffffa0000000: /home/user/linux/build/drivers/ata/ata_generic.ko
>
> - o Set a breakpoint on some not yet loaded module function, e.g.:
> +- 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
> +- Continue the target::
> +
> (gdb) c
>
> - o Load the module on the target and watch the symbols being loaded as well as
> - the breakpoint hit:
> +- 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
> @@ -91,7 +100,8 @@ Examples of using the Linux-provided gdb helpers
> 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:
> +- Dump the log buffer of the target kernel::
> +
> (gdb) lx-dmesg
> [ 0.000000] Initializing cgroup subsys cpuset
> [ 0.000000] Initializing cgroup subsys cpu
> @@ -102,19 +112,22 @@ Examples of using the Linux-provided gdb helpers
> [ 0.000000] BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved
> ....
>
> - o Examine fields of the current task struct:
> +- 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:
> +- 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:
> +- 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 = {
> @@ -144,7 +157,7 @@ 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:
> +this is just a snapshot of the initial version::
>
> (gdb) apropos lx
> function lx_current -- Return current task
> diff --git a/Documentation/dev-tools/tools.rst b/Documentation/dev-tools/tools.rst
> index 43f7dee..824ae8e 100644
> --- a/Documentation/dev-tools/tools.rst
> +++ b/Documentation/dev-tools/tools.rst
> @@ -22,3 +22,4 @@ whole; patches welcome!
> ubsan
> kmemleak
> kmemcheck
> + gdb-kernel-debugging
>
Acked-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
Looks nicer and less invasive than some of the markdown conversions.
Good to know.
Jan
--
Siemens AG, Corporate Technology, CT RDA ITP SES-DE
Corporate Competence Center Embedded Linux
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