Re: [PATCH v2 7/8] livepatch: Add sample livepatch module

Joe Lawrence
2019-03-18T19:21:17Z

On Fri, Mar 01, 2019 at 11:13:12AM -0300, Joao Moreira wrote:
> From: Josh Poimboeuf <jpoimboe@redhat.com>
>
> Add a new livepatch sample in samples/livepatch/ to make use of
> symbols that must be post-processed to enable load-time relocation
> resolution. As the new sample is to be used as an example, it is
> annotated with KLP_MODULE_RELOC and with KLP_SYMPOS macros.
>
> The livepatch sample updates the function cmdline_proc_show to
> print the string referenced by the symbol saved_command_line
> appended by the string "livepatch=1".
>
> Update livepatch-sample.c to remove livepatch MODULE_INFO
> statement.
>
> [jmoreira:
> * update module to use KLP_SYMPOS
> * Comments on symbol resolution scheme
> * Update Makefile
> * Remove MODULE_INFO statement
> * Changelog
> ]
>
> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
> Signed-off-by: Joao Moreira <jmoreira@suse.de>
> ---
> samples/livepatch/Makefile | 2 +
> samples/livepatch/livepatch-annotated-sample.c | 113 +++++++++++++++++++++++++
> 2 files changed, 115 insertions(+)
> create mode 100644 samples/livepatch/livepatch-annotated-sample.c
>
> [ ... snip ... ]
>
> diff --git a/samples/livepatch/livepatch-annotated-sample.c b/samples/livepatch/livepatch-annotated-sample.c
> new file mode 100644
> index 000000000000..44d9e9542db1
> --- /dev/null
> +++ b/samples/livepatch/livepatch-annotated-sample.c

Super small nit, but I shuffled the annotated-sample code around so it
better matched the original sample. This minimized the diff when I
compared the two versions to see what was added for sympos annotation:

[squash] livepatch: adjust annotated sample formatting
https://github.com/torvalds/linux/commit/ce49c70e85cf87e513de3bcf64953de191c3c6d7

> [ ... snip ... ]
>
> +static int livepatch_init(void)
> +{
> + int ret;
> +
> + ret = klp_register_patch(&patch);
> + if (ret)
> + return ret;
> + ret = klp_enable_patch(&patch);
> + if (ret) {
> + WARN_ON(klp_unregister_patch(&patch));
> + return ret;
> + }
> + return 0;
> +}
> +
> +static void livepatch_exit(void)
> +{
> + WARN_ON(klp_unregister_patch(&patch));
> +}

v5.0 deprecates klp_register_patch(), klp_unregister_patch(), and
klp_disable_patch(), so adjust the sample accordingly:

[squash] livepatch: rebase the annotated sample
https://github.com/torvalds/linux/commit/fc04952376cfd8281eb663bd2ce18fec27eb42b2

-- Joe