Live-Patching Archive on lore.kernel.org
 help / color / Atom feed
From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Petr Mladek <pmladek@suse.com>
Cc: Jiri Kosina <jikos@kernel.org>, Miroslav Benes <mbenes@suse.cz>,
	Joe Lawrence <joe.lawrence@redhat.com>,
	Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>,
	Nicolai Stange <nstange@suse.de>,
	live-patching@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 3/5] livepatch: Allow to distinguish different version of system state changes
Date: Wed, 23 Oct 2019 16:15:28 -0500
Message-ID: <20191023211528.nfstzbuzzxsyffqh@treble> (raw)
In-Reply-To: <20191003090137.6874-4-pmladek@suse.com>

Hi Petr,

Sorry for taking so long...

On Thu, Oct 03, 2019 at 11:01:35AM +0200, Petr Mladek wrote:
> diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h
> index 726947338fd5..42907c4a0ce8 100644
> --- a/include/linux/livepatch.h
> +++ b/include/linux/livepatch.h
> @@ -133,10 +133,12 @@ struct klp_object {
>  /**
>   * struct klp_state - state of the system modified by the livepatch
>   * @id:		system state identifier (non-zero)
> + * @version:	version of the change (non-zero)

Is it necessary to assume that 'version' is non-zero?  It would be easy
for a user to not realize that and start with version 0.  Then the patch
state would be silently ignored.

I have the same concern about 'id', but I guess at least one of them has
to be non-zero to differentiate valid entries from the array terminator.

> +/* Check if the patch is able to deal with the given system state. */
> +static bool klp_is_state_compatible(struct klp_patch *patch,
> +				    struct klp_state *state)
> +{
> +	struct klp_state *new_state;
> +
> +	new_state = klp_get_state(patch, state->id);
> +
> +	if (new_state)
> +		return new_state->version >= state->version;
> +
> +	/* Cumulative livepatch must handle all already modified states. */
> +	return !patch->replace;
> +}

From my perspective I view '!new_state' as an error condition.  I'd find
it easier to read if the ordering were changed to check for the error
first:

	if (!new_state) {
		/*
		 * A cumulative livepatch must handle all already
		 * modified states.
		 */
		return !patch->replace;
	}

	return new_state->version >= state->version;


> +
> +/*
> + * Check that the new livepatch will not break the existing system states.
> + * Cumulative patches must handle all already modified states.
> + * Non-cumulative patches can touch already modified states.
> + */
> +bool klp_is_patch_compatible(struct klp_patch *patch)
> +{
> +	struct klp_patch *old_patch;
> +	struct klp_state *state;
> +
> +
> +	klp_for_each_patch(old_patch) {

Extra newline above.

> +		klp_for_each_state(old_patch, state) {
> +			if (!klp_is_state_compatible(patch, state))
> +				return false;
> +		}
> +	}

I think renaming 'state' to 'old_state' would make the intention a
little clearer, and would be consistent with 'old_patch'.

-- 
Josh


  reply index

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-03  9:01 [PATCH v3 0/5] livepatch: new API to track " Petr Mladek
2019-10-03  9:01 ` [PATCH v3 1/5] livepatch: Keep replaced patches until post_patch callback is called Petr Mladek
2019-10-03  9:01 ` [PATCH v3 2/5] livepatch: Basic API to track system state changes Petr Mladek
2019-10-03  9:01 ` [PATCH v3 3/5] livepatch: Allow to distinguish different version of " Petr Mladek
2019-10-23 21:15   ` Josh Poimboeuf [this message]
2019-10-24 12:13     ` Petr Mladek
2019-10-03  9:01 ` [PATCH v3 4/5] livepatch: Documentation of the new API for tracking " Petr Mladek
2019-10-03  9:01 ` [PATCH v3 5/5] livepatch: Selftests of the " Petr Mladek
2019-10-04 14:47   ` Joe Lawrence
2019-10-09 14:18     ` Petr Mladek
2019-10-09 14:27       ` Joe Lawrence
2019-10-08 22:19   ` kbuild test robot
2019-10-04 14:39 ` [PATCH v3 0/5] livepatch: new API to track " Joe Lawrence

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20191023211528.nfstzbuzzxsyffqh@treble \
    --to=jpoimboe@redhat.com \
    --cc=jikos@kernel.org \
    --cc=joe.lawrence@redhat.com \
    --cc=kamalesh@linux.vnet.ibm.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=live-patching@vger.kernel.org \
    --cc=mbenes@suse.cz \
    --cc=nstange@suse.de \
    --cc=pmladek@suse.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Live-Patching Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/live-patching/0 live-patching/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 live-patching live-patching/ https://lore.kernel.org/live-patching \
		live-patching@vger.kernel.org
	public-inbox-index live-patching

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.live-patching


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git